Protoberberine alkaloids from Berberis pruinosa and their antimalarial activities

Three new protoberberine alkaloids berpruines A-C (1, 2, and 4), along with six known compounds and one isolation artifact (9) from the 95 % EtOH extract of roots of Berberis pruinosa. Their structures were determined by the comprehensive analyses of the spectroscopic data (1D NMR, 2D NMR, HRESIMS, and CD) and physicochemical properties, and berpruine C (4) as the first example of 2,3,9,10,12 pentasubstituted protoberberine alkaloid from plants. Compounds 4, 5, 7, and 10 exhibited significant in vitro antimalarial activities with IC₅₀ values of 5.5, 1.1, 8.4, and 3.1 μM, and compounds 1, 6, and 8 exhibited moderate antimalarial activities with IC₅₀ values ranging from 23.0 to 39.9 μM. In addition, a summary of preliminary structure-activity relationship of isolated protoberberine alkaloids for in vitro antimalarial activity was described.