Improving liposolubility and lipid antioxidant activity of mangiferin through esterification by lipase

Mangiferin is one of the main bioactive ingredients in leaves of Mangifera indica. But the poor liposolubility and low bioavailability restrict its application. This study aimed to esterify mangiferin with lipase to improve its lipophilicity, and evaluate its antioxidant activity and hypoglycemic properties. Four fatty acids (palmitic acid, lauric acid, stearic acid, oleic acid) were selected for enzymatic esterification with mangiferin by single-factor experiments. Under the following optimum reaction conditions of tetrahydrofuran (THF):tert-amyl alcohol (2:1) was used as solvent, water activity was 0.31, TLIM lipase was 45 mg mL^–1, The ratio of mangiferin to fatty acid was 1:50, and the substrates were pretreated by ultrasonic for 0.5 h, then reacted at 55°C for 21 h, the resulting conversion rates of mangiferin-esterified derivatives exceeded 70.0%.

Lipophilicity, antioxidant, and PTP1B inhibitory activity of mangiferin-esterified derivatives were determined. The results demonstrated that compared with mangiferin, the ability to scavenge DPPH radicals decreased by about 9%, but the lipophilicity was increased by 10–30 times, and the lipid antioxidant capacity was also improved significantly. Moreover, the inhibitory activity of protein tyrosine phosphatase 1B (PTP1B) exhibited minimal alteration. This indicates that esterification can not only improve the lipophilicity of mangiferin, but also improve its lipid antioxidant capacity.

Practical Applications: In the study, a series of mangiferin-esterified derivatives were synthesized and their lipophilicity, antioxidant properties, and PTP1B inhibitory activity were determined. The results indicated that, compared with the untreated mangiferin, the mangiferin-esterified derivatives exhibited superior lipid antioxidant and hypoglycemic activities. Furthermore, the enzymatic esterification method employed in this study offered greater economic and environmental advantages when compared to chemical catalysis. Therefore, the preparation of mangiferin derivatives through enzymatic esterification were deemed feasible with potential application value for enhancing lipid antioxidant capacity in high-fat foods.