In vitro antifungal activity of plant extracts obtained with alternative organic solvents against Rhizoctonia solani Kühn

There is a lack of knowledge about the antimicrobial activity of plant extracts obtained with organic solvents different to ethanol, methanol or acetone. In this study, plant extracts from Larrea tridentata, Flourensia cernua, Agave lechuguilla, Opuntia sp. and Yucca sp., obtained with alternative organic solvents (lanolin and cocoa butter) and water were tested against the fungus Rhizoctonia solani. In addition, the IC50 concentration of each plant extract was determined. Extractions using the alternative organic solvents permitted the extraction of tannins in higher amount than those obtained using water as solvent. Tannin extraction was strongly dependent on plant specie as well as on the solvent used. Results showed that extracts from L. tridentata and F. cernua using lanolin and cocoa butter to dozes 2000 and 1000 ppm of total tannins inhibited 100% the R. solani growth. The IC50 for each extract was highly variable; the lowest IC50 value was obtained with L. tridentata extract using lanolin to 1.85 × 102 ppm. The lanolin and cocoa butter solvents allowed high recovery of polyphenolic molecules with strong antifungal activity against R. solani, and offer an alternative in production of antimicrobial agents for organic agriculture.