Monoamine oxidase inhibitory naphthoquinones from the roots ofLithospermum erythrorhizon
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Activity-guided fractionation of a hexane-soluble extract of the roots ofLithospermum erythrorhizon, using a mouse brain monoamine oxidase (MAO) inhibition assay, led to the isolation of two known naphthoquinones, acetylshikonin and shikonin, and a furylhydroquinone, shikonofuran E. These compounds were shown to inhibit MAO with IC50 values of 10.0, 13.3, and 59.1 μM, respectively. Although no specificity for MAO-A and MAO-B was shown by acetylshikonin and shikonin, a Lineweaver-Burk plot analysis indicated that the inhibition was competitive for both MAO-A and MAO-B activity.
Key wordsLithospermum erythrorhizon Boraginaceae Naphthoquinone Monoamine oxidase inhibitor
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