Antifungal activity of Heterothalamus alienus metabolites

The chemical study of Heterothalamus alienus gave rutin, spathulenol (1), (1R,7S)‐germacra‐4(15),5,10(14)‐trien‐1 β ‐ol (2), sakuranetin (3), padmatin 3‐acetate (4), (2R,3R)‐dihydroquercetin‐7,3′,4′‐trimethyl ether (5), (2R,3R)‐dihydroquercetin‐7,4′‐dimethyl ether (6), (2R,3R)‐3‐acetoxy‐5,7,4′‐trihydroxyflavanone (7), as the main components of an antifungal extract of the aerial parts of the plant. Compound 2 showed moderate activity, with Epidermophyton floccosum being the most susceptible species (MIC = 100 µg/mL); compound 3 showed the best antifungal behavior having a broad spectrum of action and the lowest MICs. This flavanone along with flavanolol 5 showed very good activity against standardized (MIC = 31.2 µg/mL) as well as clinical isolates of Trichophyton rubrum and T. mentagrophytes (MIC ranges 31.2–62.5 µg/mL and 31.2–125 µg/mL, respectively) and demonstrated not only fungistatic but also fungicide properties. Flavanolol 6 was active against all the dermatophytes tested with MICs of 62.5–250 µg/mL. Rutin, spathulenol (1) and the 3‐acetylated flavanones 4 and 7 were inactive or marginally active against the fungal panel. Copyright © 2008 John Wiley & Sons, Ltd.