Potential Antifungal Activity against Pythium insidiosum of Isoflavonoids from the Stems of Dalbergia cultrata

Chemical investigation of Dalbergia cultrata Grah. stems growing in Thailand resulted in the isolation and characterization of 14 known compounds, including tectorigenin (1), calycosin (2), pratensein (3), afromosin (4), irilin D (5), biochanin A (6), daidzein (7), formononetin (8), 8-O-methylretusin (9), 7,3′-dihydroxy-5′-methoxyisoflavone (10), (3S)-sativanone (11), (3S)-violanone (12), erycibenin D (13) and isoliquiritigenin (14). Their structures were established mainly based on NMR spectroscopic techniques and physical properties. The isolated compounds were evaluated for antifungal activity against Pythium insidiosum using disc diffusion assay. Antifungal drugs available now are not effective to treat this microorganism. It was found that compound 1 exhibited stronger antifungal activity than amphotericin-B standard with an MIC value of 10 μg/disc.