Seasonal evaluation of the postharvest fungicidal activity of powders and extracts of huamuchil (Pithecellobium dulce):: action against Botrytris cinerea, Penicillium digitatum and Rhizopus stolonifer of strawberry fruit

The fungistatic or fungicidal effect of powders, and aqueous and ethanolic extracts of seeds, and monthly harvested leaves of huamuchil (Pithecellobium dulce) were evaluated for fungicidal activity, against Botrytis cinerea, Penicillium digitatum, and Rhizopus stolonifer. Fungicidal activity of huamuchil powders and aqueous extracts were also evaluated on strawberry fruit during storage. Preliminary characterization of the active compound responsible for the fungicidal effect was carried out using thin layer chromatography and spectrophotometry. Results indicated that powders had the best fungicidal effect, in both in vitro and in situ studies. Fungistatic or fungicidal properties were associated with the plant organ and harvest month. A correlation between high absorbance values of extracts with the fungicidal or fungistatic effect was not observed. The highest fungistatic or fungicidal effect for both in vitro and in situ studies was recorded from extracts of leaves harvested in months having more stressful environmental conditions; the cold season (October-February) and, the dry, hot season (April and June). Attempts to characterize the active compound suggest that kaempferol may be responsible for the fungicidal effect. (C) 2003 Elsevier Science B.V. All rights reserved.