Keywords

9.1 Introduction

Sponges are simple invertebrates with loose organization. Generally, they have spicules of silica or calcium carbonate embedded in their bodies for support and fibrous skeletons made of a horny substance called spongin; however, either or both of these may be lacking. Because sponges lack a distinct enteron and the germ layers are not well established, the phylum Porifera is sometimes classed in a separate subkingdom, the Parazoa, or the Metazoa.

There are approximately 4000 species of sponges. About 1 % (all members of a single family) inhabits freshwater, 10 % are intertidal, and the remaining is marine or benthic. Sponges obtain feed by propelling water through tiny pores in the body wall, thus capturing microorganisms and organic detritus that may be present in their body. Further the sponges inhabit several millions of symbiotic organisms, particularly microorganisms which are producing many biologically active substances for their successful survival in sponges which are also taking part in it. Because of this reason, there is a debate among the researchers about the source of these biological substances. Thus the sponge as a whole contributes to show a variety of biological activities, including antimicrobial, anticancer, and also reported to have toxic materials (Table 9.1).

Table 9.1 Details of the compound, source and its potential biological activity
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9.2 Biologically Active Metabolites from Sponges

9.2.1 Polyketides

9.2.1.1 Fatty Acid Metabolites

The azacyclopropene, dysidazirine (Fig. 9.1) was isolated from the grey sponge Dysidea fragilis that lacks a spicule skeleton; instead it has a network of fibers loaded with sand grains, broken spicules, and other foreign material. It is strongly conulose and forming lobate or digitate cushions and elastic when compressed. It is a common sponge along most coasts of Western Europe. The dysidazirine reported an IC50 value of 0.27 μg/ml against L1210, the mouse lymphocytic leukemia cells (Molinski and Ireland 1988).

Ficulinic acids A (Fig. 9.2) and B (Fig. 9.3) from the sponge Ficulina ficus (= Suberites ficus Linnaeus 1767) reported inhibition on the growth of the mouse lymphocytic leukemia cells (L1210) with an ID50 value of 10–12 μg/ml (Guyot et al. 1986). It is an orange sponge with big massive lobate, occasionally cylindrical, with one or more conspicuous, large oscules. It has a velvety smooth appearance. It enjoys its distributed in North East Atlantic coast mostly in places with tidal currents.

Fig. 9.1
figure 1

Dysidazirine

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Fig. 9.2
figure 2

Ficulinic acid A: n = 7

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Fig. 9.3
figure 3

Ficulinic acid B: n = 9

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9.2.1.2 Long-Chain Acetylenes

Numerous aliphatic compounds have been isolated from sponges, and a number of these have been reported to be cytotoxic. Five monoacetylenic alcohols with different reactive groups (Fig. 9.4) from the sponge Cribrochalina vasculum collected in Belize were toxic to the mouse P388 cell line (IC50 1.0,1.3, 1.1, 0.2, 0.1 μg/ml, respectively), and they also showed in vitro immunosuppressive activity in lymphocyte reaction tests (Gunasekera and Faircloth 1990). This appears to be the first report of branched-chain aliphatic acetylenic compounds from marine organisms. C. vasculum is also called Cribrochalina infundibulum (Schmidt 1870). Smooth inverted cones, to ear-shaped or fan-shaped, sometimes torn or crooked by waves or predators; color tan to vinaceous. The skeleton of Cribrochalina is made of thick multispicular tracts cemented by spongin and is found distributed in Santa Marta, Colombia (Hallock et al. 1995).

Duryne (Fig. 9.5) that was isolated from the Caribbean sponge Cribrochalina dura, was found toxic to murine leukemia cells (IC50 0.07 μg/ml) and also colon, lung and mammary cell lines, with MIC (Minimum Inhibitory Concentration) of 0.1 μg/ml (Wright et al. 1987a).

Petrosia ficiformis is one of the sponges found producing more acetylenes, that have different purposes in industry. One among them is Petrosynol (Fig. 9.6), a polyacetylene of 30 atoms, showed antibiotic activity and was also active in the starfish egg assay at 1 μg/ml (Fusetani et al. 1987). Cimino et al. (1990) have described a number of C46 polyacetylenes that were active in the brine shrimp assay (IC50 0.002–0.12 μg/ml) and also the sea urchin egg assay (IC50 1–50 μg/ml).

P. ficiformis has a compact, hard texture, with spherical oscula irregularly spread over the surface. It is found on the underside of rocks, on overhangs and in caves between 5 m and 70 m depth. The species has been reported at Adriatic Sea, Aegean Sea, Azores, Canaries, Madeira, Cape Verde, Ionian Sea, Levantine Sea, Mediterranean Sea, North Atlantic, Tunisian Plateau/Gulf of Sidra, West Africa and Western Mediterranean.

Fig. 9.4
figure 4

Monoacetylenic alcohols

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Fig. 9.5
figure 5

Duryne (Molecular formula – C30H48O2)

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Fig. 9.6
figure 6

Petrosynol

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9.2.1.3 Aliphatic Ester Peroxides

Xestins A and B (Figs. 9.7 and 9.8), isolated from Xestospongia sp., were found toxic against P388 cells (ID50 0.3 and 3 μg/ml, respectively) (Quinoa et al. 1986). P. lita is maroon to pink, with the opening of the barrel pale white. In the intertidal zones, this species ranges from 10 to 20 cm in diameter, and are about 10–20 cm tall. This species is found in the Philippines, Australia, western and central Indian Ocean, Indonesia, Malaya, and New Caledonia.

The cyclic peroxide acids (Fig. 9.9) isolated from the sponge Plakortis angulospiculatis, which are much more highly branched were collected in Venezuela, and the esters derived from the sponge were found inhibiting the growth of P388 cells (IC50 0.2–0.9 μg/ml) (Gunasekera et al. 1990b).

Fig. 9.7
figure 7

Xestin A

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Fig. 9.8
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Xestin B

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Fig. 9.9
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Cyclic peroxide acids

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9.2.1.4 Complex Polyketides

The polyether carboxylic acids acanthifolicin (Fig. 9.10) and okadaic acid (Fig. 9.11) were initially isolated from sponges – acanthifolicin from the Caribbean sponge Pandaros acanthifolium and okadaic acid from Halichondria okadai collected in Japan and also from H. melaodocia from the Florida Keys, reported strong cytotoxic activity (Schmitz et al. 1981; Tachibana et al. 1981). The ED50 value of 0.0002 and 0.0017 μg/ml against P388 cells were reported by acanthifolicin and okadaic acid, respectively.

The sponge, P. acanthifolium (Duchassaing and Michelotti 1864) is erect, dark bushy with flattened branches. Branches up to 25 cm long, 4 cm wide. Oscules inconspicuous. It is a reef dweller and it is found distributed in Florida and the Caribbean.

The polyketide natural product, discodermolide (Fig. 9.12), was isolated from the deep-sea marine sponge Discodermia dissoluta in 1990 by Gunasekara et al. (1990a). It was found to be a potent inhibitor of tumor cell growth in several MDR cancer cell lines. Further, it was identified as one of the most potent natural promoters of tubulin assembly.

Fig. 9.10
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Acanthifolicin

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Fig. 9.11
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Okadaic acid

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Fig. 9.12
figure 12

Discodermolide

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9.2.1.5 Macrolides

9.2.1.5.1 Assorted Macrolides

Fijianolides A and B (Figs. 9.13 and 9.14) were isolated from the Vanuatuan sponge Spongin mycofijiensis (= Leiosella lavis) (Quinoa et al. 1988). This sponge is massive, lobate, or tubular, sometimes with a short stalk (2–3 cm). The size varies from 3 to 20 cm in height, and 2–10 cm in diameter. The surface is microconulose, and the texture is compressible and flexible. This species is dark brown/black, in colour, externally and tan inside and is generally found in sheltered reef habitats, under ledges or in caves. It is fairly rare despite its broad range of distribution in the South and Indo Pacific.

Fijianolide A reported the IC50 of 9 μg/ml against P388 and 11 μg/ml vs HT-29 human colon tumor cells. When the diacetate of fijianolide B was tested against the same cells, it reported the IC50 as 6 μg/ml vs P388 and 0.5 μg/ml vs HT-29.

The three other tris-isoxazole containing macrolides, mycalolides A–C (Figs. 9.15, 9.16 and 9.17), were isolated from Mycale. Although the above were highly cytotoxic (IC50 0.0005–0.001 μg/ml vs. B16), they have not shown promising results in vivo (Fusetani et al. 1988).

Apart from okadaic acid, the Japanese sponge H. kadai was a good source of a group of very complex and biologically active macrolides, halichondrins B (Fig. 9.18) and C (Fig. 9.19); norhalichondrins A (Fig. 9.20), B (Fig. 9.21), and C (Fig. 9.22) and homohalichondrins A (Fig. 9.23), B (Fig. 9.24), and C (Fig. 9.25) (Hirata and Uemura 1986). The above macrolides showed the following in vitro activity against B16 melanoma cell lines: norhalichondrin A – 0.0052 μg/ml; halichondrin B – 0.000093 μg/ml; homohalichondrin A – 0.00026 μg/ml; halichondrin C – 0.00035 μg/ml and homohalichondrin B – 0.0001 μg/ml. Halichondrin B showed good in vivo activity against B16 melanoma in mice (T/C values of 203–244 %, depending on dose (5–20 μg/kg) and regimen), against P388 leukemia in mice (T/C 323 % @ 10 μg/kg), and against L1210 in mice (T/C 207–375 % with doses of 50–100 μg/kg under various injection schedules). From the results, it was concluded that it is important for antitumor activity that the tricyclic ring be relatively lipophilic and that the terminal group have two or more hydroxyls, but not a carboxylate. Halichondria are massive, amorphous sponges with clearly separated inner and outer skeletons consisting of bundles of spicules arranged in a seemingly random pattern.

Misakinolide A (Fig. 9.26) isolated from Theonella sp. was collected in Okinawas (Sakai et al. 1986), and it showed in vitro antiviral and antifungal activities. Theonella sp. is a coral reef sponge (Theonella swinhoei), found distributed in the Red Sea and Indian Ocean.

The macrolide latrunculin A (Fig. 9.27) was isolated from the red sea sponge Latrunculia magnifica. It binds and stabilizes the globular G-actin in a 1:1 complex, preventing the conversion of globular (monomeric) G-actin into filamentous (polymeric) F-actin, disturbing microfilament organization in the cell. Latruculin A affects normal functioning of the cell by disrupting the polymerization of G-actin and microfilament organization which is essential for the cellular mechanical processes including motility and cytoskeleton scaffolding (Groweiss et al. 1980).

Fig. 9.13
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Fijianolides A

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Fig. 9.14
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Fijianolides B

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Fig. 9.15
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Mycalolides A

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Fig. 9.16
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Mycalolides B

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Fig. 9.17
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Mycalolides C

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Fig. 9.18
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Halichondrins B (R = H)

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Fig. 9.19
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Halichondrins C (R = OH)

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Fig. 9.20
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Norhalichondrins A

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Fig. 9.21
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Norhalichondrins B

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Fig. 9.22
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Norhalichondrins C

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Fig. 9.23
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Homohalichondrins A (R1 = R2 = OH, R3 = H)

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Fig. 9.24
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Homohalichondrins B (R1 = R2 = R3 = H)

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Fig. 9.25
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Homohalichondrins C (R1 = R3 = H, R2 = OH)

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Fig. 9.26
figure 26

Misakinolide A

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Fig. 9.27
figure 27

Latrunculin A

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9.2.1.6 Miscellaneous

The sponge, Polyfibrospongia sp., collected on the island of Miyako in Okinawa was the source for hennoxazoles A–D (Figs. 9.28, 9.29 and 9.30) (Ichiba et al. 1991). Apart from displaying analgesic activity, hennoxazole A, the major component (0.01 % of wet weight) showed strong activity against HSV-1 (IC50 0.6 μg/ml).

Fig. 9.28
figure 28

Hennoxazoles A (R1 = OH, R2 = CH3)

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Fig. 9.29
figure 29

Hennoxazoles B (R1 = OH, R2 = CH2 CH3)

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Fig. 9.30
figure 30

Hennoxazoles C (R1 = OH, R2 = CH2 CH2 CH2 CH3)

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9.3 Terpenes

9.3.1 Sesquiterpenes

Curcuphenol (Fig. 9.31) extracted from the sponge Didiscus flavus collected in both shallow and deep waters in the Bahamas and Belize was found inhibiting the growth of several cell lines [IC50 7 μg/ml vs. P388; MIC for human cell lines: A549 (lung) 10 μg/ml; HCT-8 (colon) 0.1 μg/ml; MDAMB (mammary) 0.1 μg/ml] (Wright et al. 1987b).

Metachromins A (Fig. 9.32) and B (Fig. 9.33), isolated from the sponge Hippospongia cf. metachromia, were reported to be toxic to L1210 cells (IC50 2.4 and 1.62 μg/ml, respectively) (Ishibashi et al. 1988). Further they also showed coronary vasodilating effects and inhibited potassium chloride-induced contraction of the rabbit isolated coronary artery.

Avarol (Fig. 9.34) from the sponge Dysidea avara interferes with the mitotic processes, thus preventing telophase formation which may be due to changes of the intracellular pools and/or alterations of the permeability properties of the cell membranes for the precursors (Mueller et al. 1985).

Puupehenone (Fig. 9.35) was isolated from a deep water sponge, Strongylophora hartmani by Kohmoto et al. (1987a). It was found to inhibit the growth of a number of tumour cell lines (IC50; P388, 1 μg/ml; A549 human lung, 0.1–1 μg/ml; HCT-8 human colon, 1–10 μg/ml; MCF-7 human mammary, 0.1–1 μg/ml). Besides the above, it also showed very modest in vivo effects on p388 cell lines (19 % increase in lifetime @ 25 mg/kg for 9 days).

Isonitrile, isothiocyanate, and related functionalized terpenes are characteristic metabolites of sponges belonging to the order Halichondida. Four amorphane sesquiterpenes (Fig. 9.36) were isolated from the Fijian sponge Axinyssa fenestratus (Alvi et al. 1991) and tested for their anthelmintic activity.

Another sesquiterpene, axisonitrile-3 (Fig. 9.37) (D’ Blassio et al. 1976) extracted from Topsentia sp. from Thailand (Alvi et al. 1991). Though it reported superior anthelmintic activity in vitro at 50 μg/ml, it was not active in vivo.

Fig. 9.31
figure 31

Curcuphenol

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Fig. 9.32
figure 32

Metachromin A

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Fig. 9.33
figure 33

Metachromin B

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Fig. 9.34
figure 34

Avarol

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Fig. 9.35
figure 35

Puupehenone (Molecular formula – C21H28O3)

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Fig. 9.36
figure 36

Amorphane sesquiterpenes

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Fig. 9.37
figure 37

Axisonitrile-3

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9.3.2 Sesterterpenes

A nonsteroidal sesterterpene, manoalide (Fig. 9.38), isolated from the sponge Luffariella variabilis (De Silva and Scheuer 1980) has emerged as a potent tool for studying inflammation. It irreversibly inhibited PLA2 (Glaser and Jacobs 1986; Jacobson et al. 1990).

In addition to inhibiting PLA2, manoalide inhibited 5-lipoxygenase (de Vries et al. 1988), leading to speculation that its anti-inflammatory activity of manoalide was attributed to its inhibitory effect on Ca2+ channels (Wheeler et al. 1988). Interestingly at low concentrations, manoalide inhibited calcium channels with no effect on phosphor-inositide metabolism. The ability of manoalide to dissect these two components of the inflammation process may prove to be its most useful attribute in studying the role of Ca2+ signaling in inflammation and proliferation (Barzaghi et al. 1989).

Another analog of manoalide, luffariellolide (Fig. 9.39), isolated from the same organism, also exhibited anti-inflammatory activity, but it was slightly less potent than manoalide and was a partially reversible PLA2 inhibitor (Albizati et al. 1987).

A number of cytotoxic furanosesterpenes have been obtained from a variety of sponges. Variabilin (Fig. 9.40) and the related sesterpene tetronic acids from a Caribbean Ircinia sp. sponge were all described as being cytotoxic to host BSC cells at 2 μg/ml in an antiviral assay (Barrow et al. 1988).

Okinonellins A and B (Figs. 9.41 and 9.42), from Spongionella sp., were reported to inhibit division of fertilized starfish eggs at 5 μg/ml (Kato et al. 1986a).

The bishomo scalarene sesterpene phyllofoliaspongin (Fig. 9.43) from Phyllospongia foliascens inhibited P388 cell growth at 5 μg/ml (Kitagawa et al. 1989). Another activity noted for this compound was its antithrombocytic inhibitory effect on ADP-induced and collagen-induced aggregation of rabbit platelets in vitro.

Sesterterpenes extracted from the sponge Hyrtios erecta showed in vitro anthelmintic activity. Heteronemin (Fig. 9.44) (Kazlauskas et al. 1976; Kashman and Rudi 1977) showed in vitro activity with varying results. Another compound 12-episcalarin (Fig. 9.45) (Cimino et al. 1977; Crews and Bescansa 1986) exhibited moderate in vitro anthelmintic activity.

Fig. 9.38
figure 38

Manoalide

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Fig. 9.39
figure 39

Luffariellolide (Molecular formula – C25H38O3)

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Fig. 9.40
figure 40

Variabilin

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Fig. 9.41
figure 41

Okinonellin A

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Fig. 9.42
figure 42

Okinonellin B

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Fig. 9.43
figure 43

Phyllofoliaspongin

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Fig. 9.44
figure 44

Heteronemin

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Fig. 9.45
figure 45

12-episcalarin

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9.3.3 Sesquiterpenoid Isocyanide

Wright et al. (1988) reported the antitumor, antiviral, and antifungal activities for a sesquiterpenoid isocyanine (Fig. 9.46) isolated from the marine sponge Bubaris sp.. At 20 μg/0.5 ml, the A59 coronavirus in mouse liver cells was partially inhibited, indicating that the sesquiterpenoid compound is only weakly virucidal.

Fig. 9.46
figure 46

Isocyanine

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9.3.4 Diterpenes

Among the various kalihinols extracted from the sponge Acanthella cavernosa, Kalihinols Y (Fig. 9.47) and J (Fig. 9.48) reported potent in vitro anthelmintic activity (Chang et al. 1987; Omar et al. 1988; Alvi et al. 1991).

Kohmoto et al. (1987b) isolated spongiadiol (Fig. 9.49), epispongiadiol (R1 + R2 = O, R3 = OH, R4 = H), and the new isospongiadiol [2∞, 19-dihydroxyspongia – 13(16), 14-dien-3-one] (R1 = H, R2 = OH, R3 + R4 = O) from the deep-water Caribbean sponge Spongia sp.. Both antiviral activity and cytotoxicity were reported for all the three spongiodiols. In vitro assays against HSV-1 revealed a spectrum of activities ranging from the very active spongiadiol (IC50 = 0.25 μg/ml) to the modestly active epispongiadiol (IC50 = 12.5 μg/ml), with isospongiadiol exhibiting intermediate activity (IC50 = 2.0 μg/ml). Further the studies on antitumour and antiviral activities of these three furanoditerpenoids, spongidiol and isospongiadiol gave 100 % inhibition on HSV-1 plaque formation at 20 and 0.5 μg/(6 mm disk), and epispongiadiol gave partial inhibition at 12.5 μg/ml (Kohmoto et al. 1987b).

Kashman et al. (1987) isolated reiswigins A (R = CH CH(CH3)2) and B (R = −CH = C(CH3)2) (Fig. 9.50), bioactive terpenes from the sponge Epipolasis reiswigi. Both reiswigins A and B were found reporting the inhibition of HSV-1 completely at 2 μg and A59 virus partially at 20 μg (+ +). Particularly reiswigin A completely inhibited VSV at 2 μg without accompanying cytotoxicity (Kashman et al. 1989a).

Fig. 9.47
figure 47

Kalihinol Y

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Fig. 9.48
figure 48

Kalihinol J

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Fig. 9.49
figure 49

Spongiadiol

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Fig. 9.50
figure 50

Reiswigin A

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9.3.5 Triterpenes

Pouoside A (Fig. 9.51) from Asteropus sp., collected in Truk Lagoon, inhibited P388 cell growth with an ED50 of 1.5 μg/ml (Ksebati et al. 1988, 1989). The Okinawan sponge Penares sp. was the source of penasterol (Fig. 9.52), which was active against L1210 cells with an ED50 of 3.6 μg/ml (Cheng et al. 1988a).

Fig. 9.51
figure 51

Pouoside A

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Fig. 9.52
figure 52

Penasterol

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9.3.6 Sterols

Several polyoxygenated sterols and glycosylated sterols showed cytotoxicity. Sarasinoside A1 (Fig. 9.53), a saponin containing amino sugar, exhibited an ED50 of 2.8 μg/ml against P388 cells. This saponin was isolated by Schmitz et al. (1988) from Asteropus sp. from Truk and Guam Islands.

Eryloside A (Fig. 9.54) from the red sea sponge Erylus lendenfeldi reported to have both cytotoxic (IC50 4.2 μg/ml vs. P388) and antifungal activity against Candida albicans (MIC 15.6 μg/ml) (Carmely et al. 1989a).

Fig. 9.53
figure 53

Sarasinoside A1

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Fig. 9.54
figure 54

Eryloside A

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9.4 Brominated Compounds

The compound isolated from the marine sponge Verongia cauliformis (Sharma and Burkholder 1967) has been characterized as 2,6-dibromo-4-acetamido-4-hydroxycyclohexadienone (Fig. 9.55) showed antibacterial activity (Sharma et al. 1970).

Aerothionin (Fig. 9.56) having a spiro-cyclohexadienylisoxazole skeleton was isolated from two sponges namely Aplysia aerophoba and Verongia thiona showed antibiotic activity (Encarnacion et al. 2000; Thoms et al. 2004).

Fig. 9.55
figure 55

2,6-dibromo-4-acetamido-4-hydroxycyclohexadienone

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Fig. 9.56
figure 56

Aerothionin

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9.5 Nitrogen-Containing Compounds

9.5.1 Tyrosine-Based Metabolites

Several members of the bastadin series of cyclic amides (Figs. 9.57) isolated from the sponge Iarthella basta were found to inhibit P388 cell growth (ED50 2–4 μg/ml) (Pordesimo and Schmitz 1990).

Fig. 9.57
figure 57

Bastadin series of cyclic amides

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9.5.2 Other Amines

Mycalamides A (R = 4) and B (R = Me) (Fig. 9.58) obtained from a New Zealand sponge Mycale sp. (Perry et al. 1988a, 1990) showed antiviral and cytotoxic activity.

Calyculins A–D (Fig. 9.59) are unusual amines isolated from Discodermia calyx (Kato et al. 1986b, c, 1988a, b) that showed the IC50 value of 7.4 × 10−4, 8.8 × 10−4, 8.6 × 10−4, and 1.5 × 10−3 μg/ml respectively against L1210 cells. They also inhibited cell division of both starfish and sea urchin eggs in the 10−2 μg/ml range. Further, the calyculin A (Fig. 9.59) exhibited in vivo activity against Erlich and P388 leukemia in mice (T/C 245 and 144 %, respectively) apart from inhibiting the uptake of [3H] thymidine, [3H] uridine and [3H] leucine in L1210 murine leukemia cells (Kato et al. 1988a, b).

Fig. 9.58
figure 58

Mycalamide A (R = 4) and B (R = Me)

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Fig. 9.59
figure 59

Calyculin A

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9.5.3 Pyrroles

The alkaloid 300 (Fig. 9.60) isolated from the sponges Teichaxinella morchella and Ptilocaulis walpersi reported mild cytotoxicity to L1210 cells (IC50 19 μg/ml) (Wright and Thompson 1987).

Fig. 9.60
figure 60

Alkaloid

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9.5.4 Imidazoles

The girolline (Fig. 9.61) extracted from the sponge Pseudaxinyssa cantharella was found active against P388 at 0.001–1 μg/ml, and this activity was confirmed in vivo also in mice models (P388 at 1 mg/kg doses (Ahond et al. 1989).

Pyronaamide (Fig. 9.62), obtained from Leucetta sponge from Saipan and Guam, was toxic to KB cells (MIC 5 μg/ml) (Akee et al. 1990). A series of 2-amino imidazole alkaloids called naamidines (e.g. Fig. 9.63) were obtained by Carmely et al. (1989b) from the marine sponge Leucetia chagosensis that showed cytotoxicity at 2–10 μg/ml against P388 cells.

Fig. 9.61
figure 61

Girolline

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Fig. 9.62
figure 62

Pyronaamide

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Fig. 9.63
figure 63

Series of 2-amino imidazole alkaloids Naamidines

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9.5.5 Indoles

Horbindoles A–C (Fig. 9.64) extracted from Axinella sp. from western Australia showed cytotoxicity (KB; MIC 5, >10, and 10 μg/ml, respectively) and were also found to have fish antifeedant activity (Herb et al. 1990).

A deep water sponge, Dragmacidian sp. was the source for dragmacidin (Fig. 9.65) that was found to be toxic to P388 cells (IC50 15 μg/ml) and also to A549 human-8 human colon, and MDAMB human mammary cells, all with IC50 of 1–10 μg/ml (Kohmoto et al. 1988). Morris and Anderson (1990) isolated the closely related dragmacidon A (Fig. 9.66) which showed cytotoxicity against L1210 cells (ED50 10 μg/ml) similar to that of dragmacidin.

An antimicrobial pigment, fascaplysin (Fig. 9.67), obtained from a Fijian sponge, Fascaplysinopsis sp., killed L1210 cells (LD50 0.2 μg/ml) and also showed antibiotic activity against four different microorganisms (Roll et al. 1988).

The other group of indoles, eudistomins were initially reported as antiviral agents, but Eudistomin K (Fig. 9.68), obtained from Riterella sigillinoides, is described in a patent as being “very effective in inhibiting growth of L1210, P388, A549 and HCT-8 cells at varying concentrations” (Blunt et al. 1988).

Manzamine A, an alkaloid (Fig. 9.69) was reported as its hydrochloride salt from a Haliclona sp. of sponge from Okinawa with as IC50 of 0.07 μg/ml against P388 cells in vitro (Sakai et al. 1986b).

Fig. 9.64
figure 64

Horbindole A (R = Me); Horbindole B (R = Et); Horbindole C (R = CH = CH-Et)

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Fig. 9.65
figure 65

Dragmacidin

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Fig. 9.66
figure 66

Dragmacidon A

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Fig. 9.67
figure 67

Fascaplysin

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Fig. 9.68
figure 68

Eudistomin K

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Fig. 9.69
figure 69

Manzamine A

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9.5.6 Pyridines

The pyridine alkaloids theonelladins A–D (Fig. 9.70) isolated from the sponge Theonella swinhoei (Kobayashi et al. 1989) showed the cytotoxicities of 4.7, 1.0, 3.6, and 1.6 μg/ml (IC50) against L1210 cell lines and 10.0, 3.6, 10.0, and 5.2 μg/ml (ED50) against KB cells. These compounds were also reported to be 20 times more than caffeine in causing release of Ca2+ from sarcoplasmic reticulum.

The related pyridine alkaloids niphatynes A (Fig. 9.71) and B (Fig. 9.72), from Niphates sp. collected in Fiji, were found cytotoxic to P388 cells (IC50 0.5 μg/ml) (Quinoa and Crews 1987).

Fig. 9.70
figure 70

Theonelladins A (R = H); Theonelladin B (R = CH3-D); Theonelladin C (R = H); Theonelladin D (R = CH3)

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Fig. 9.71
figure 71

Niphatyne A

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Fig. 9.72
figure 72

Niphatyne B

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9.5.7 Nucleosides

Nucleosides are vital components of all living cells and are involved in several biological processes.

The two cytotoxic nucleosides 5-(methoxycarbonyl) tubercidin (Fig. 9.73) and toyocamycin (Fig. 9.73) isolated from the Fijian sponge Jaspis (Zabriskie and Ireland 1989) showed IC50 values of 0.0026 and 0.27 μg/ml, respectively, against L1210. The 5-(methoxycarbonyl) tubercidin (Fig. 9.73) also reported earlier to have in vivo activity against L1210, increasing lifetimes by up to 39 %.

The two antiviral and antitumor compounds presently in clinical use as antiviral or antitumor agents (i.e., ara-A, 9-β-D-arabinofuranosyladenine, Fig. 9.74; ara-C, 1-β-D-arabinosylcytosine, Fig. 9.74) were isolated from the marine sponge Cryptotethia crypta in the early 1950s (Bergmann and Feeney 1950, 1951). Bergmann collected C. crypta in 1945, within next few years he reported the presence of spongothymidine (ara-T, 1-β-D-arabinofuranosylthymidine, Fig. 9.74), spongouridine (ara-U, 1-β-D-arabinofuranosyluracil, Fig. 9.74), and spongosine (1-β-D-arabinofuranosyl-2-methoxyadenine) (Cohen 1966).

The in vitro studies of the arabinosides (Fig. 9.74) showed varying antiviral activity against HSV-1 or HSV-2. Using rabbit kidney and human skin fibroblast cultures, De Clercq et al. (1977) reported MICs (minimum inhibitory concentration) as low as 0.02 and 1 μg/ml for ara-C and ara-A, respectively, against HSV-1; and 200 and 10 μg/ml, respectively, against HSV-2. Besides the above, a significant in vitro activity was also observed for a number of xylofuranonucleosides against three DNA viruses (HSV-1, HSV-2, and vaccinia) and one RNA virus (thinovirus-9) (Gosselin et al. 1986).

Doridosine (Fig. 9.75) (Quinu et al. 1980) was isolated from marine sponge Tedania digitala from Australia. It causes reduced arterial pressure and reduced heart rate in mammalians in a manner that is qualitatively similar to adenosine. It also acts as muscle relaxant and showed hypothermic activity.

1-Methylisoguanosine (Fig. 9.76) was isolated from the sponge Tedania digitata (Quinu et al. 1980). This nucleoside showed potent muscle relaxant, blood pressure lowering, cardiovascular, and anti-inflammatory activity (Jamieson and Davis 1980).

Fig. 9.73
figure 73

5-(methoxycarbonyl) tubercidin (R1 = CO2Me, R2 = ribose) and Toyocamycin (R1 = CN, R2 = ribose)

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Fig. 9.74
figure 74

Arabinosides

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Fig. 9.75
figure 75

Doridosine

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Fig. 9.76
figure 76

1-Methylisoguanosine

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9.5.8 Quinolines and Isoquinolines

The aaptamine (Fig. 9.77) and some of its derivatives (R1 = H, R2 = H; 163. R1 = H, R2 = CH3) were isolated from the sponge Suberites sp., which were reported to have some in vitro and in vivo cell inhibitory activity when tested for antitumor activity against Ehrlich ascites tumor in mice. A 95 % inhibition was reported in the case of mice inoculated with Ehrlich ascites tumor cells pretreated with the derivative with R1 = H, R2 = H or R1 = H, and R2 = CH3 at 25 μg/ml (Fedoreov et al. 1988).

A series of pyrroloquinoline alkaloids namely isobatzellines A–D (Figs. 9.78) were found in extracts of the Caribbean sponge Batzella sp. (Sun et al. 1990). These compounds showed antifungal activity against C. albicans. Renierol (Fig. 9.79), obtained from the Fijian sponge Xestospongia caycedoi, inhibited the growth of L1210 cells (IC50 3 μg/ml) (McKee and Ireland 1987).

Fig. 9.77
figure 77

Aaptamine (R1 = CH3, R2 = H) and some of its derivatives (R1 = H, R2 = H; 163. R1 = H, R2 = CH3)

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Fig. 9.78
figure 78

Isobatzellines

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Fig. 9.79
figure 79

Renierol

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9.5.9 Quinilizidines and Indolizidines

The indolizidine stellenamide A (Fig. 9.80) from the sponge Stella sp. showed antifungal activity and also inhibited K562 epithelium cell growth (IC50 of 5.1 μg/ml) (Hirota et al. 1990a).

Fig. 9.80
figure 80

Indolizidine stellenamide A

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9.5.10 Prianosins/Discorhabdins

The prianosins and discorhabdins, the two closely related sulfur-containing alkaloids, were extracted from Latrunculia sp. and Prianos sp. The first of these to be reported was discorhabdin C (Fig. 9.83) (Perry et al. 1988a). The remaining discorhabdins (Figs. 9.81, 9.82, 9.83 and 9.84 = discorhabdins A,B,C,D, respectively) were described subsequently (Perry et al. 1988a,b). The discorhabdins A–D isolated from the sponges Latrunculia brevis and Prianos sp. reported the cytotoxicity (IC50) of 0.05, 0.1, 0.03, and 6.0 μg/ml, respectively, against P388 cells. Only discohabdin D (Fig. 9.84) showed any in vivo activity in the P388 model and that was modest (T/C 132 at 20 mg/kg).

Prianosin A (Fig. 9.85), from the Okinawan sponge Prianos melanos (Kobayashi et al. 1987), is the nonprotonated form of discorhabdin A (Fig. 9.81). The remaining prianosins B–C (Figs. 9.86 and 9.87) were reported in 1988 (Cheng et al. 1988b). Prianosin D (Fig. 9.87) and discorhabdin D (Fig. 9.84) are a hydroquinone/quinine pair. The prianosins A–D reported the IC50 of 0.037, 2.0, 0.15, and 0.18 μg/ml against L1210 cells, 0.014, 1.8, 0.024 and 0.048 μg/ml against L5178Y cells and 0.073, >5, 0.57 and 0.46 μg/ml against KB cells respectively. In addition to these activities, the prianosin D (Fig. 9.87), but not the others, induced Ca2+ release from sarcoplasmic reticulum, with potency ten times than that of caffeine.

Fig. 9.81
figure 81

Discorhabdin A

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Fig. 9.82
figure 82

Discorhabdin B

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Fig. 9.83
figure 83

Discorhabdin C

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Fig. 9.84
figure 84

Discorhabdin D

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Fig. 9.85
figure 85

Prianosin A

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Fig. 9.86
figure 86

Prianosin B

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Fig. 9.87
figure 87

Prianosin C (R = OH) and D (R = H)

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9.5.11 Marine Alkaloids

Dysemenin (Fig. 9.88) a hexachlorinated alkaloid isolated from the sponge Dysidea herbacea (Charles et al. 1978, 1980; Biskupiak and Ireland 1984) was found inhibiting iodide transfer in thyroid cells. This molecule might provide insight into the mechanism of the elusive “iodide pump” as it inhibits iodine transport by a different mechanism than ouabain (Van Sande et al. 1990).

The polycyclic aromatic alkaloid, amphimedine (Fig. 9.89), isolated from Amphimedon sp. was found active against P388 in vitro with an ED50 value of 0.4 μg/ml, but proved inactive in vivo (Schmitz et al. 1983).

Dercitin (Fig. 9.90), from a deepwater sponge Descitus sp., showed in vitro and in vivo activity (T/C 170 at 5 mg/kg) in the P388 model (Gunawardana et al. 1988). In addition, dercitin was described as having immunosuppressive and antiviral activity. The dercitin was found disrupting the macromolecular synthesis (DNA, RNA, and protein) in the P388 system by binding to DNA and inhibiting nucleic acid synthesis (Burres et al. 1989).

Inman et al. (1990) isolated plakinidines A (Fig. 9.91) and B (Fig. 9.91), using an antiparasite bioassay, from the fijian sponge Plakortis sp. The planinidine A inhibited reverse transcriptase activity at 1 μg/ml. Thereafter West et al. (1990) described plakinidines A, B, and C (Fig. 9.91) from the same Fijian sponge species and reported the IC50 values of 0.1, 0.3 and 0.7 μg/ml, respectively, for these compounds against L1210 cells.

Fig. 9.88
figure 88

Dysemenin

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Fig. 9.89
figure 89

Amphimedine

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Fig. 9.90
figure 90

Dercitin

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Fig. 9.91
figure 91

Plakinidine A (R = H); Plakinidine B (R = CH3); Plakinidine C (R = HΔ9)

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Other anthelmintic-active alkaloids were isolated from a Fijian sponge of the family Spongiidae, originally identified as Spongia mycofijiensis (Kakou et al. 1987). This sponge yielded latrunculin A (Fig. 9.92) (Kashman et al. 1980), which showed excellent in vitro activity at 50 μg/ml against N. brasiliensis.

Fig. 9.92
figure 92

Latrunculin A

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9.5.12 Guanidines

Kashman et al. (1989b) isolated ptilomycalin A (Fig. 9.93) from the Caribbean sponge Ptilocaulis spiculifer and a red sea sponge Hemimycale sp. that reported activity against HSV at a concentration of 0.2 μg/ml (Kashman et al. 1989a). In addition to the high antiviral activity, this compound exhibited antitumor and antifungal activities also.

In later years, Janes Erijman et al. (1991) isolated a series of compounds related to ptilomycalin A from the Mediterranean sponge Crambe crambe. The new compounds, the crambescidins (Fig. 9.93) showed activity against HSV-1 at 1.25 μg/ml and exhibited 98 % inhibition of L1210 cell growth at 0.1 μg/ml.

The diacetate salts of the series of bromopyrroles were extracted from the Caribbean sponge Agelas conifer (Rinehart 1988; Keifer et al. 1991). Based on spectroscopic comparisons to the known sceptrin (Fig. 9.94) (Walker et al. 1981), as well as on FABMS and NMR data, the structures assigned included the oxysceptrins (Fig. 9.96) and ageliferins (Fig. 9.95). The compounds of the sceptrin and ageliferin groups were found active against HSV-1 at 20 μg/disk and VSV at 100 μg/disk, while the oxysceptrins were less active (Keifer et al. 1991).

Acarnidines la–1c (Figs. 9.97 and 9.98) were isolated from Acarnus erithacus, collected from Gulf of California, and were reported to show antiviral property (Carter and Rinehart 1978). The homospermidine skeleton common to these three guanidine compounds was assigned based on GC/MS data, and the compounds were distinguished from one another by their fatty acid constituents. In addition to some antibacterial activity, the activity against HSV-1 was also obtained at 100 μg/disk.

Fig. 9.93
figure 93

Ptilomycalin A (R1 = R2 = H, n = 13)

Crambescidins (Crambescidin 816: R1 = R2 = OH, n = 13; Crambescidin 830:R1 = R2 = OH, n = 14; Crambescidin 844: R1 = R2 = OH, n = 15; Crambescidin 800: R1 = H, R2 = OH, n = 13

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Fig. 9.94
figure 94

Sceptrin

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Fig. 9.95
figure 95

Ageliferin

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Fig. 9.96
figure 96

Oxysceptrin

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Fig. 9.97
figure 97

Acarnidine la (R = CO(CH2)10CH3)

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Fig. 9.98
figure 98

Acarnidine 1b (R = CO(CH2)3CH = CH(CH2)5CH3(z))

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9.5.13 Peptides and Depsipeptides

Sponges are a large and diverse group of colonial organisms that constitute the phylum Porifera with thousands of different species extensively distributed from superficial waters near the sea shores up to deep waters of the ocean. Active peptides from sponges most of them with unique unprecedent structures in comparison with these kind of compounds from other sources are often cyclic or linear peptides containing unusual amino acids which are either rare in terrestrial and microbial systems or even totally novel, and also frequently containing uncommon condensation between amino acids (Aneiros and Garateix 2004).

Discobahamin A (Fig. 9.99) was a bioactive antifungal peptide evaluated as inhibitor of the growth of Candida albicans isolated from the Bahamian deep water marine sponge Discodermia sp. (Gunasekera et al. 1994; Tohma et al. 2003).

The cyclic depsipeptides papuamides A and B (Fig. 9.100) isolated from sponges of the genus Theonella, containing a number of unusual amino acids are also the first marine-derived peptides reported to contain 3-hydroxyleucine and homoproline residues (Ford et al. 1999). They inhibited the infection of human T-lymphoblastoid cells be HIV-1 sub (RF) in vitro with an EC50 of approximately 4 ng/ml.

Microspinosamide a new cyclic depsipeptide incorporating 12 amino acid residues (Fig. 9.101) from the sponge Sidonops microspinosa reported anti-HIV activity (Rashid et al. 2001). It also inhibited the cytopathic effect of HIV-1 infection in an XTT-based in vitro assay.

Another novel peptide, keramamide (Fig. 9.102) (Kobayashi et al. 1991) as well as orbiculamide A (Fig. 9.103) (Fusetani et al. 1991) isolated from the marine sponge Theonella sp. reported cytotoxic effect against P388 murine leukemia cells (IC50 = 4.7 ng/ml). The other active peptide Cyclotheonamide (Fig. 9.104) (Fusetani et al. 1990) isolated from the species of the same genus was reported as a potent antithrombin cyclic peptide which strongly inhibited various proteinases, particularly thrombin.

Theonellamide F (Fig. 9.105) an antifungal peptide isolated from Theonella sp. from Japan also showed activity against L1210 and P388 cells (IC50 3.2 and 2.7 μg/ml, respectively) (Matsunaga et al. 1989).

From a western Pacific sponge, Hymeniacidon sp., collected at Palau, Pettit et al. (1990) isolated the cyclic octopeptide, hymenistatin 1 (Fig. 9.106) in which all amino acids therein having the schirality. It showed both in vitro (ED50 3.5 μg/ml) and in vivo activity (T/C 130) against P388 murine leukemia cells.

Three new antifungal cyclic peptides with unprecedented amino acids, microsclerodermins A-B (Figs. 9.107) were isolated from two species of sponges, Theonella sp. and Microscleroderma sp. from the Philippines (Schmidt and Faulkner 1998). Another antifungal cyclic peptide isolated from the same sponges was the Theonegramide (Fig. 9.108) (Bewley and Faulkner 1994).

Fig. 9.99
figure 99

Discobahamin A

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Fig. 9.100
figure 100

Papuamides A and B

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Fig. 9.101
figure 101

Microspinosamide

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Fig. 9.102
figure 102

Keramamide

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Fig. 9.103
figure 103

Orbiculamide A

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Fig. 9.104
figure 104

Cyclotheonamide

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Fig. 9.105
figure 105

Theonellamide F

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Fig. 9.106
figure 106

Hymenistatin 1

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Fig. 9.107
figure 107

Microsclerodermin A (R = OH) – Microsclerodermin B (R = H)

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Fig. 9.108
figure 108

Theonegramide

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9.6 Conclusion

The researchers studying the marine natural products report several substances with interesting pharmacological properties. But only very few of them are available as potent drugs in the market which are being superseded by the synthetic ones. This may be because of the non-availability of source materials for the continuous supply of such biologically active compounds. Further this acts as a limiting factor for the pharmaceutical companies to go for patenting. So the pharmaceutical companies prefer the synthetic compounds to get continuous supply after launching their product in the market. However, it is not that much easy to synthesize, economically, some of the natural products, since they have more complex structure. Hence, further research is needed to find out the ways and means to synthesize the more complex marine natural products.

Above all, the research in the field of marine natural products needs to be encouraged by the funding agencies to get fruitful results in future which need not be immediate as that of synthetic chemistry outcomes.