Antimicrobial Prenylated Acetophenones from Berries of Harrisonia abyssinica.

The ripe berries of Harrisonia abyssinica yielded two new prenylated acetophenones, namely 5-(ethan-1'-one)-4,6-dihydroxy- 7-(3",3"-dimethylallyl)-2S-(1'S-hydroxy-1',5'-dimethylhex-4'- enyl)-2,3-dihydrobenzofuran (1) and 5-(2"'-hydroxyethan-1"'- one)-4,6-dihydroxy-7-(3",3"-dimethylallyl)-2S-(1'S-hydroxy-1', 5'-dimethylhex-4'-enyl)-2,3-dihydrobenzofuran (2), herein named harronin I and harronin II, respectively. The compounds were isolated following activity guided fractionation and the structures were determined using 1D, 2D NMR spectroscopic, CD and MS spectrometric techniques. The methanol-dichloromethane mixture (1:1 v/v) crude extract exhibited strong antimicrobial activity against Candida albicans, Bacillus cereus, Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Lactobacillus casei. Harronin I (1) showed a MIC of 5 μg/mL against C. albicans, 6 μg/mL against B. cereus, and more than 20 μg/mL against other tested microorganisms. Harronin II (2) showed much weaker MIC values (> 100 μg/mL) against all the tested microorganisms. [ABSTRACT FROM AUTHOR]