Solasonine Modulates Aldose Reductase Activity in Galleria mellonella (Lepidoptera): Implications for the Polyol Pathway

Glycoalkaloids are plant secondary metabolites known to affect multiple physiological processes in insects; however, their effects on carbohydrate and polyol metabolism remain poorly understood. This study investigated the effects of solasonine on hemolymph metabolites and aldose reductase activity in the fat body of Galleria mellonella larvae. Larvae were fed a diet supplemented with five nominal dietary concentrations of solasonine (10−4–1 mg/kg diet) for three days. Hemolymph metabolites were analyzed by RP-HPLC, and aldose reductase activity was determined in fat body lysates. Inositol levels differed significantly among experimental groups (one-way ANOVA, p < 0.0001), with the 10−4 mg/kg diet treatment differing significantly from the vehicle control (p = 0.0015). Aldose reductase activity was significantly lower at 10−2, 10−3, and 10−4 mg/kg diet compared with the untreated control (p = 0.0439, p = 0.027, and p < 0.0001, respectively), while only the 10−4 mg/kg treatment differed significantly from the vehicle control (p = 0.0029). Formic acid also significantly affected several metabolic parameters. Overall, solasonine exposure was associated with altered aldose reductase activity and changes in polyol-related metabolites, although some metabolic effects may be attributable to the vehicle.