Comparable Metabolic and Histopathological Observations of Enzymatic and Non-Enzymatic Thai Shallot Extracts in High-Fat Diet-Induced Obese Mice

Thai shallot (Allium cepa L. var. aggregatum) is rich in quercetin glycosides, which can be enzymatically hydrolyzed into aglycone forms with potentially higher bioavailability. However, whether this structural modification enhances metabolic efficacy in vivo remains unclear. This study aimed to compare the metabolic and histopathological effects of enzymatic (ESE) and non-enzymatic (NES) Thai shallot extracts in a high-fat diet (HFD)-induced obese mouse model. Male C57BL/6 mice were fed HFD for 12 weeks to induce obesity, followed by a 12-week treatment with NES or ESE (1000 and 2000 mg/kg/day). Metabolic parameters, lipid profiles, oxidative stress markers, hepatic enzyme activities, and histopathological changes were evaluated. Enzymatic hydrolysis significantly increased the proportion of quercetin aglycone without altering total quercetin content. Both NES and ESE improved fasting glucose, insulin resistance, lipid profiles, and oxidative stress markers compared with HFD controls. Histological examination showed attenuation of hepatic steatosis and preservation of tissue architecture in treated groups. However, no consistent superiority of ESE over NES was observed across metabolic or histopathological outcomes. Despite substantial modification of flavonoid composition, enzymatic processing did not enhance the measured metabolic efficacy of Thai shallot extract under the conditions tested. Because circulating quercetin and metabolite levels were not assessed, this finding should be interpreted as comparable metabolic efficacy rather than evidence of equivalent bioavailability. These findings suggest that factors beyond aglycone content may play a key role in determining biological activity, with implications for the development and cost-effectiveness of functional food products.