Geranins A and B, new antiprotozoal A-type proanthocyanidins from Geranium niveum.

Bioassay-guided fractionation of the antiprotozoal extract of Geranium niveum led to the isolation of two new A-type proanthocyanidins, epi-afzelechin-(4beta-->8, 2beta-->O-->7)-afzelechin (1) and epi-catechin-(4beta-->8, 2beta-->O-->7)-afzelechin (2). Compounds 1 and 2 were given the trivial names of geranins A and B, respectively. In addition, five known compounds, mahuannin B (3), reynoutrin (4), hyperin (5), methyl gallate (6), and 3-beta-caffeoyl-12-oleanen-28-oic acid (7), were obtained. The structures of the new proanthocyanidins were elucidated by spectroscopic and chemical methods as well as CD measurements. Compounds 1, 2, and 4-7 were tested against axenically grown trophozoites of Giardia lamblia and Entamoeba histolytica.