Antifungal activity against anthracnose-causing species of homopterocarpin derivatives.

Derivatives of 3,9-dimethoxypterocarpan (, homopterocarpin) were prepared by nitration, amination, and oxidation reactions, among others, and their antifungal activity was evaluated against the phytopathogenic fungi and . Derivatives were purified by chromatographic techniques and identified by nuclear magnetic resonance spectroscopy. Eight derivatives were obtained from corresponding to 3,9-dimethoxy-8-nitropterocarpan (), 3,9-dimethoxy-2,8-dinitropterocarpan (), 3,9-dimethoxy-2,8,10-trinitropterocarpan (), 2,8-diamino-3,9-dimethoxypterocarpan (), 3,9-dimethylcoumestan (), medicarpin (), 2'-hydroxy-4-(2-hydroxyethylsulfanyl)-7,4'-dimethoxyisoflavan (), and 4-(2-hydroxyethylsulfanyl)-7,2',4'-trimethoxyisoflavan (). The antifungal activity of the derivatives was determined at concentrations between 35 and 704 μM. Compounds and  at 704 μM, showed an inhibition of radial growth and spore germination close to 100%, exceeding that found for the starting compound , which was 46%. Growth inhibition assays were also performed for the derivative on papaya fruits ( L. cv. Hawaiana) and mango ( L. cv. Hilacha) infected with . Compound showed fungal growth inhibition in fruits higher than that found for and thymol (a recognized natural antifungal), under the same conditions. In general, derivatives that exhibited greater antifungal activity correspond to the compounds containing hydroxyl groups in the structure. Some of the compounds obtained could be considered promising for the control of phytopathogenic fungi.