Oleuropein and Other Polyphenols from Olive (Olea europea) for Protecting the Plant Against Pseudomonas syringae subsp. savastanoi

Abstract

p ]Among the main polyphenols isolated from waste waters of olive (Olea europea) mill, catechol, 4-methylcatechol and hydroxytyrosol were toxic for Pseudomonas syringae subsp. savastanoi, the causai agent of olive knot disease. In particular the most toxic was 4-methylcatechol, Among some synthetic derivatives of catechol, as o-quinone, guaiachol, veratrole and diacetylcatechol, which were tested on P. savastanoi and on Corynebacterium michiganense (Gram⁺), o-quinone was strongly toxic for both bacteria, whereas veratroie and diacetylcatechol were toxic only for P. savastanoi. From fruits and leaves of olive was isolated oieuropein, a well known phenolic glucoside, from which was prepared its agtycone, by using a commercial β-giucosidase and hydroxytyrosol by chemical hydroiysis. The oieuropein was significantly toxic on P. savastanoi at a concentration of 10^-3 and 10^-4 M, while its aglycone was toxic in the range between 10^-2 and 10^-4 M and hydroxytyrosot at 10^-2 and 10^-3 M.

It is interesting to note that free glucose was growth stimulant of P. savastanoi at 10^-2 M, while was growth inhibiting at 10^-3 and 10^-4 M. Among all the compounds cited above, the most interesting byproducts for a possible application in agriculture are oieuropein, its agiycone and hydroxytyrosol, because of the other polyphenols are toxic on olive and human cells.