Quantitative estimation of metabolites and antifungal efficacy of leaf extracts <i>Aspilia africana</i> on cucumber and pawpaw fruit spoilage fungi

Abstract

Several reports have shown that about 25% of harvested fruits globally are lost to spoilage by microorganisms. The study determined the quantitative metabolites and bioactivities of Aspilia africana extracts on fungi from spoiled Cucumis sativus and Carica papaya fruits. The fungi from spoiled C. sativus and C. papaya fruits were obtained using mycological techniques. The quantitative metabolites and bioactivities of the aqueous (ALEAA) and ethanol (ELEAA) extracts of A. africana were determined using the standard protocol and disc diffusion technique, respectively. The fungal genera obtained were Aspergillus, Penicillium, Mucor, Fusarium, and Rhizopus. There were variations in percentage yields, physical appearances, and pH of the extracts. The results of quantitative estimation of metabolites showed that ALEAA had mean protein, carbohydrate, and lipid contents of 15.36 ± 0.32%, 60.97 ± 1.14%, and 6.66 ± 0.04%, respectively. Alkaloids showed a positive correlation with protein (r = 0.2028) and carbohydrate (r = 0.421), and a negative correlation with lipid (r = -0.6556) at p < 0.05. The ELEAA exhibited more inhibitory effects on test fungal isolates, with mean zones of inhibition (IZs) ranging from 9.3 ± 0.1 to 18.8 ± 0.3 mm, than the ALEAA, with mean IZs ranging between 9.4 ± 0.4 and 16.0 ± 1.0 mm. The R coefficients of the extracts and IZs as exhibited by the fungi ranged from 0.5985 to 0.9936. The results have revealed quantitative metabolites and antifungal activities of the extract and also provided rationale for its utilization as a preservative for fruits against spoilage by fungi.