Leishmanicidal active constituents from Nepalese medicinal plant Tulsi (Ocimum sanctum L.)

In the course of screening leishmanicidal active compounds from Asian and South American medicinal plants, a Nepalese medicinal plant, Tulsi (Ocimum sanctum L.), showed strong activity. We therefore studied the isolation and structural elucidation of the active constituents from O. sanctum L. From the ethyl acetate soluble fraction of the plant, seven new novel neolignan derivatives were isolated along with 16 known compounds. The structures of the new compounds (1-7) were elucidated as 6-allyl-3',8-dimethoxy-flavan-3,4'-diol (1), 6-allyl-3-(4-allyl-2-methoxyphenoxy)-3',8-dimethoxyflavan-4'-ol (2), 5-allyl-3-(4-allyl-2-methoxyphenoxymethyl)-2-(4-hydroxy-3-methoxyphenyl)-7-methoxy-2,3-dihydrobenzofuran (3), 1,2-bis(4-allyl-2-methoxyphenoxy)-3-(4-hydroxy-3-methoxyphenyl)-3-methoxypropane (4), 1-(4-hydroxy-3-methoxyphenyl)-1,2,3-tris(4-allyl-2-methoxyphenoxy)propane (5), 1-allyl-4-(5-allyl-2-hydroxy-3-methoxyphenoxy)-3-(4-allyl-2-methoxyphenoxy)-5-methoxybenzene (6), and 3-(5-allyl-2-hydroxy-3-methoxyphenyl)-1-(4-hydroxy-3-methoxyphenoxy)-prop-1-ene (7) by means of (1)H-NMR, (13)C-NMR, and 2D-NMR spectral data. Some of these compounds showed leishmanicidal activity.