Fatty Acid Composition and In Vitro Antioxidant, Anti-Inflammatory, and Antibacterial Properties of Unrefined Black Soldier Fly (Hermetia illucens) Larvae Oil

Black soldier fly (Hermetia illucens) larvae are increasingly used as sustainable feed resources, and recent studies have expanded knowledge of their lipid fraction. This study characterized a single batch of mechanically extracted unrefined black soldier fly larvae oil (HIO), determining its fatty acid composition and assay-defined total phenolic and flavonoid contents (TPC and TFC) and evaluating its in vitro radical-scavenging activity, its effects on inflammatory mediators in LPS-stimulated RAW 264.7 macrophages, and the growth responses of five animal-associated bacterial pathogens. HIO contained 69.12% saturated fatty acids, with lauric acid accounting for 43.44% of the total fatty acids; the TPC and TFC were 2.96 ± 0.20 mg GAE/g and 1.00 ± 0.03 mg QE/g, and the ABTS and DPPH IC50 values were 3.89 ± 0.12% and 4.22 ± 0.21% (v/v), respectively. Within the non-cytotoxic range of 1.563–6.25% (v/v), HIO reduced nitric oxide and pro-inflammatory cytokine production. HIO also reduced bacterial growth in all five strains, with no growth detectable by absorbance at 6.25–12.5% (v/v) depending on the species; these endpoints were not confirmed by viable counts. Exploratory correlation analysis showed concordant concentration–response patterns across the measured domains but, because all variables followed the same concentration gradient within one oil batch, was interpreted descriptively. These findings provide a batch-specific in vitro characterization of unrefined HIO and support its further evaluation as a candidate functional feed ingredient.