Antimicrobial activity of the diarylheptanoids from the black and green alder

Antimicrobial activity of fourteen diarylheptanoids isolated from the bark of black and green alder against twelve bacterial species (five Gram-positive and seven Gram-negative) and eight fungal strains has been reported. The most sensitive bacterial species were Klebsiella pneumoniae and Pseudomonas aeruginosa (Gramnegative), and Streptosporangium longisporum and Bacillus subtilis (Gram-positive). Among fungal strains the most sensitive to the diarylheptanoids were Fusarium equiseti, F. tricinctum, Candida albicans, and Saccharomyces cerevisiae. Oregonin (8), platyphyllenone (13), hirsutenone (14), (5S)-5-hydroxy-1,7-bis(4-hydroxyphenyl)heptan-3-one-5-O-beta-D-apiofuranosyl(1 -> 6)-beta-D-glucopyranoside (2), and platyphylloside (1) were the most active diarylheptanoids against both bacteria and fungi, especially against fungi. Eleven of fourteen investigated diarylheptanoids exhibited stronger antifungal activity than standards nystatin and fluconazole against C. albicans and eight against S. cerevisiae. Structure/activity analysis revealed the importance of the enone moiety in the structure of diarylheptanoids for the antifungal activity. Significant antifungal activity and high content of oregonin (8) and hirsutenone (14) in the black alder bark chloroform/methanol (1:1) extract recommend the use of these compounds as easily accessible potential antifungal remedies.