Alkaloids isolated from Haemanthus humilis Jacq., an indigenous South African Amaryllidaceae: Anticancer activity of coccinine and montanine

Haemanthus humilis Jacq., an indigenous South African Amaryllidaceae, was studied for the first time for its alkaloid content. From the acid extract of its bulbs, albomaculine, incartine, coccinine and montanine, belonging to the lycorine-, homolycorine- and isoquinoline-type alkaloids respectively, were isolated. Coccinine was the main metabolite (1.49 g/kg) and to the best of our knowledge H. humilis is to date the best natural source of this alkaloid. It is noteworthy that this Amaryllidaceae does not synthesize lycorine, the main and most common alkaloid produced by this plant genus. All the isolated alkaloids were bio-assayed for their anticancer activity against a panel of six human cancer cell lines, with coccinine evaluated for the first time. The results showed that coccinine and montanine have significant activity at low micromolar concentrations.