Chemical Constituents and Comparative Toxicity of Aspilia africana (Pers) C. D ADAMS LEAF Extracts Against Two Leafspot Fungal Isolates of PAW-PAW (C arica papaya L.)

Abstract

The toxicity of chloroform, Petroleum ether and Methanol leaf extracts of Aspilia africana against Collectotrichum gloesporiodes and Curvularia lunatus , the pathogens of leafspot disease of paw-paw was investigated. The fungi were cultured in potato dextrose-leaf extract agar medium at the concentrations of 20mg/ml, 40mg/ml, 80mg/ml, 160mg/ml, 320mg/ml and the mycelial extension growth rate were observed. All the extracts showed significant (p<0.05) activity and concentration-dependent growth inhibition against the leafspot fungi with the percentage inhibition range from 35-100% at various concentrations. Only methanol extract gave 100% inhibition of fungal growth at 160mg/ml and 320mg/ml. C. lunatus was more sensitive to the extract than C. gloeosporioides . Preliminary phytochemical screening of the extracts revealed the presence of alkaloids, anthraquinones, flavonoids, glycosides, phenols, saponins, tannins and terpenes in varying degrees. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the extracts showed a complex mixture of compounds which included 8 in methanol and petroleum ether extracts and 7 in chloroform extract. The implication of these findings is that extracts of A. africana could be a good antifungal agent with potential applications in agriculture against foliar diseases of paw-paw so as to improve production.