Naringin, one of the citrus flavonoids and known as a natural antioxidant, has limited bioavailability owing to its low stability and solubility. However, naringin esters formed via acylation have recently been reported to possess improved physical and chemical properties. The development of these compounds has a great potential in the food, cosmetic and pharmaceutical industries, but low conversion and productivity are barriers to industrial applications. This study aimed to improve the conversion of naringin acetate, which is formed via the enzymatic reaction between naringin and an acyl donor. An optimal reaction condition was determined by evaluating the effect of various variables (enzyme type, enzyme concentration, acyl donor, molar ratio of reactants, reaction temperature, and solvent) on the synthesis of naringin acetate. The optimal condition was as follows: 3 g/L of Lipozyme TL IM, molar ratio of 1:5 (naringin:acyl donor), reaction temperature of 40 °C, and acetonitrile as the reaction solvent. Under this condition, the maximum conversion to naringin acetate from acetic anhydride and vinyl acetate was achieved at approximately 98.5% (8 h) and 97.5% (24 h), respectively. Compared to the previously reported values, a high conversion was achieved within a short time, confirming the commercial potential of the process.

Puerarin is a flavonoid known as a natural antioxidant found in the root of Pueraria robata. Its antioxidant, anticancer, and anti-inflammatory effects have attracted attention as a potential functional ingredient in various bioindustries. However, puerarin has limited bioavailability owing to its low lipid solubility and stability. Acylation is proposed as a synthesis method to overcome this limitation. In this study, lipase-catalyzed acylation of puerarin and various acyl donors was performed, and the enzymatic synthetic condition was optimized. Under the condition (20 g/L of Novozym 435, palmitic anhydride, 1:15, 40 °C, tetrahydrofuran (THF)), the synthesis of puerarin ester achieved a significantly high conversion (98.97%) within a short time (3 h). The molecule of the synthesized puerarin palmitate was identified by various analyses such as liquid chromatography–mass spectrometry (LC–MS), Fourier-transform infrared spectroscopy (FT-IR), and carbon-13 nuclear magnetic resonance (¹³C NMR). The lipid solubility and the radical scavenging activity were also evaluated. Puerarin palmitate showed a slight decrease in antioxidant activity, but lipid solubility was significantly improved, improving bioavailability. The high conversion achieved for puerarin esters in this study will provide the foundation for industrial applications.