Effects of Black Soldier Fly ( Hermetia illucens ) Larvae on Bulk Secondary Metabolite Levels and Antioxidant Activity in Moringa oleifera Biomass

Abstract

ABSTRACT Moringa oleifera is a nutrient‐rich tropical plant containing bioactive secondary metabolites. While these metabolites provide antioxidant and antimicrobial properties, they may reduce digestibility or palatability when used as animal feed. This study evaluated the impact of Black soldier fly (BSF) larvae on the bulk levels of secondary metabolites and antioxidant activity in M. oleifera leaves. Leaves were incubated with 1500 7‐day‐old BSF larvae at 27°C and 65% relative humidity for 16 days, with three replicates per treatment. Post‐treatment material, consisting of residual substrate and larval excreta (frass), was analyzed using qualitative phytochemical screening and quantitative spectrophotometric assays. Larval treatment was associated with significantly lower levels of total phenols (0.712 ± 0.22 and 0.534 ± 0.34 mg gallic acid equivalents per gram (mg GAE g −1 ) in treated fresh and dried samples, respectively) compared with untreated controls (1.264 ± 0.18 and 1.05 ± 0.67 mg GAE g −1 ). Similar reductions were observed for flavonoids and tannins. Antioxidant activity was also reduced, as indicated by values in the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay and lower ferric reducing antioxidant power (FRAP) responses ( p ≤ 0.001). These results suggest that BSF larvae feeding alters the chemical profile of M. oleifera residues; however, the compound‐specific alteration mechanism or larval accumulation was not assessed. Notably, reductions in secondary metabolites may represent a trade‐off between lowering anti‐nutritional factors and diminishing beneficial bioactive compounds. Future work employing targeted metabolomics and larval biomass analysis is needed to clarify the fate of individual phytochemicals. This study provides preliminary evidence for the potential use of BSF larvae in modifying plant residues for feed applications.