Antifungal Activity of Secondary Metabolites from Lantana Camara L. against Bio-Deteriorating Fungi of Oryza Sativa L. (Nigerian Local Rice)

Fungal contamination in rice can result in the production of mycotoxins, posing significant health risks to humans. This study investigated the antifungal efficacy of selected secondary metabolites, terpenoids, saponins, alkaloids, and flavonoids, as well as the antioxidant properties of Lantana camara L. against fungal pathogens in locally cultivated rice. The plant extract was obtained, and fungal pathogens were isolated and identified using standard microbiological techniques. Antioxidant activity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Ability of Plasma (FRAP) assays, while antifungal susceptibility was evaluated via the agar diffusion plating method. Statistical analysis was conducted using ANOVA with Tukey’s HSD test at p < 0.05. The fungal species identified in the rice samples included Aspergillus niger, Nigrospora oryzae, Fusarium oxysporum, Rhizopus sp., Alternaria alternata, and Rhizopus oryzae. A total metabolite yield of 63.18% was obtained from 1300 g of plant material, with phytochemical screening confirming the presence of terpenoids, flavonoids, saponins, tannins, cardiac glycosides, anthraquinones, steroids, alkaloids, and phenols. Antioxidant assays revealed a concentration-dependent increase in radical scavenging activity, whereas absorbance values declined at higher metabolite concentrations. Among the tested metabolites, alkaloids exhibited the highest antifungal activity, effectively inhibiting the radial growth of all fungal isolates, whereas saponins demonstrated the least potency, inhibiting only Rhizopus oryzae. These findings indicate that secondary metabolites from L. camara exhibit significant antifungal activity at minimal effective concentrations. Further activity-guided fractionation is recommended to isolate and characterize the most potent antifungal compounds for potential application in rice pathogen management.