Leishmanicidal activities of benzophenanthridine alkaloids isolated from fruits of Bocconia pearcei and their derivatives were examined. Seven benzophenanthridine compounds were isolated from the methanolic extracts of B. pearcei. Among them, dihydrosanguinarine showed the most potent leishmanicidal activities (IC50 value: 0.014 μg/ml, respectively). To examine the structure–activity relationship of the benzophenanthridine skeleton, the leishmanicidal activities for 32 synthetic samples were examined. The existence of bulky groups at the C7–C8 position was found to enhance the activity. On the other hand, the bulkiness at the C2–C3 position on the D-ring, a carbonyl group at C-6, substitution at C-6 and cleavage or saturation of the C5–C6 bond reduced activity. A methyl group on nitrogen of the C-ring was thought to be necessary for significant activity.

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 1H-NMR, 13C-NMR, and 2D-NMR spectral data. Some of these compounds showed leishmanicidal activity.