Effects of heat treatment of mandarin peel on flavonoid profiles and lipid accumulation in 3T3-L1 adipocytes

Citrus peel, a primary byproduct of citrus fruits, contains a variety of flavonoids. Heat treatment is a favorable food processing for solid peel to release bioactive compounds from tissues and intensify nutritional effects. In this study, we explored alterations of flavonoids by thermal treatment of mandarin peel and their effects on lipid accumulation and intracellular levels during differentiation of 3T3-L1 cells to adipocytes. The heat-treated sample showed stronger inhibition on the formation of lipid droplets than the non-treated sample, along with enhanced intracellular levels of flavonoids. Overall flavonoids, especially flavonoid aglycones showing better efficacy, were found to increase in the peel after heat-treatment. Our findings indicate thermal processing could help release flavonoids from citrus peel and convert them into aglycone forms, leading to efficient cellular uptake and suppression of lipid accumulation in 3T3-L1 cells. This study provides useful information of heat-treated citrus peel as potential dietary supplements with antiobesity-related effects.