Bioactivity Of Fungal Secondary Metabolites Against Some Economic Pests

Abstract Fungi have been shown to be a good source for lead molecules in drug discovery and development. However, many compounds derived from fungi were not evaluated for their bioactivity against economic pests. In this study, twelve fungal secondary metabolites (1-12) were evaluated for herbicidal activity against Silybum marianum, fungicidal activity against Alternaria solani and Fusarium oxysporum, insecticidal activity against Culex pipiens larvae, and antifeedant activity against Spodoptera littoralis larvae. Among the tested metabolites, brefeldin A (6) and 6-eopxy-4-hydroxy-3-methoxy-5-methyl-cyclohex-2-en-1-one (11) showed potent herbicidal activity against S. marianum with complete inhibition of seed germination at 500 mg/l. Compound 6 revealed an exceptional herbicidal activity as it caused complete inhibition of root growth and strong reduction in shoot growth (I = 74.5%) and germination (10.0%) at 25 mg/l. In addition, anthracobic acid A (7) showed the highest antifungal activity against F. oxysporum (EC50 = 8.21 mg/l) and 19-(α-D-glucopyranosyloxy)isopimara-7,15-dien-3β-ol (2) was the most potent compound against A. solani (EC50 = 140.8 mg/l). Furthermore, dehydroaustin (9), phomaxanthone A (4) and deacetylphomaxanthone A (5) displayed a potent toxicity against fourth larval instar of C. pipiens with LC50 values of 3.27, 57.03 and 63.5 mg/l, respectively. Among the tested metabolites, four compounds (4, 5, 7 and 11) showed antifeedant activity against third-instar larvae of S. littoralis at 1000 mg/l. The results presented in this study should be useful for developing brefeldin A (6) and dehydroaustin (9) as natural herbicide and insecticide, respectively.