Antiplasmodial alkaloids from bulbs of Amaryllis belladonna Steud.

Abstract A bioassay-guided fractionation and chemical investigation of Amaryllis belladonna Steud. bulbs resulted in the isolation and identification of the new crinane alkaloid 1,4-dihydroxy-3-methoxy powellan ( 1 ), along with the 3 known crinane alkaloids 2 – 4 and the two lycorane alkaloids 5 – 6 . The structures were elucidated by interpretation of combined HR-ESIMS, CD and 2D NMR spectroscopic data. Among these isolated compounds the lycorane-type alkaloid acetylcaranine ( 5 ) exhibited strong antiplasmodial activity, while compounds 3 and 4 were moderately active, and compounds 1 and 6 were inactive.