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The instability of ester bonds, low water solubility, and increased cytotoxicity of flavonoid glycoside esters significantly limit their application in the food industry. Therefore, the present study attempted to resolve these issues through liposome encapsulation. The results showed that baicalin butyl ester (BEC4) and octyl ester (BEC8) have higher encapsulation and loading efficiencies and lower leakage rate from liposomes than baicalin. FTIR results revealed the location of BEC4 and BEC8 in the hydrophobic layer of liposomes, which was different from baicalin. Additionally, liposome encapsulation improved the water solubility and stability of BEC4 and BEC8 in the digestive system and PBS but significantly reduced their cytotoxicity. Furthermore, the release rate of BEC4 and BEC8 from liposomes was lower than that of baicalin during gastrointestinal digestion. These results indicate that liposome encapsulation alleviated the negative effects of fatty chain introduction into flavonoid glycosides.

Different mechanisms for inhibiting tyrosinase can be exploited to avoid quality losses caused by the enzymatic browning of fruits and vegetables. Piceid (PI) and piceid 6″-O- azelaic acid ester (PIA) are oxidized by tyrosinase; however, their oxidation products may have inhibitory effects on tyrosinase. This notion is because l-DOPA oxidation was inhibited after the pre-incubation of PI/PIA with tyrosinase, however, l-DOPA oxidation was not affected if this pre-incubation was not performed. Circular dichroism analysis indicated a conformational change in the secondary structure of tyrosinase after pre-incubation. Further, molecular docking and enzyme reaction kinetics assays were employed to reveal the mechanism underlying the effects of PI/PIA on tyrosinase in the absence of pre-incubation with tyrosinase. PI/PIA had anti-browning effects in the potato models. The increased rate of A 420 in PI/PIA groups at 24 h were 281% and 279%, which were approximately 2.4- and 2.5-fold lower than that of control (668%)., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Baicalin, a phenolic glycoside with good lipid-lowering activity, has poor intestinal absorption due to low lipophilicity. In this study, six ester derivatives of baicalin, named BECn (n = 2, 3, 4, 6, 8, and 10) based on their fatty chain lengths, were synthesized by whole-cell catalyzed esterification to improve lipophilicity, and the intestinal absorption and lipid-lowering activity of the synthesized esters were investigated using cell models in vitro. BEC2, BEC3, and BEC4 exhibited higher P app values than baicalin in Caco-2 cell monolayers. The lipid-lowering activity of the three esters was stronger than baicalin in the cell models of hepatic steatosis, adipocytes and foam macrophages, and was attributed to their higher intracellular accumulation and stronger direct activation of the carnitine palmitoyltransferase 1A. Moreover, these esters were easily hydrolyzed by carboxylesterase and were unstable at pH 7.4, which significantly weakened their absorption and lipid-lowering activity. This study laid the foundation for industrial production and practical application of BAI esters., (Copyright © 2022 Elsevier Inc. All rights reserved.)

In this paper, an enzymatic route for synthesizing phenolic glycoside azelaic acid esters was successfully set up via lipase-catalyzed esterification and transesterification. Among the lipases tested, Candida antarctica lipase B (Novozyme 435) showed the highest activity in catalyzing esterification and Thermomyces lanuginosus (Lipozyme TLIM) gave the highest substrate conversion in catalyzing transesterification for the synthesis of ester. The addition of 4A molecular sieves into the reaction system is found to be an effective method for in situ absorption of the byproduct water and methanol, with which the substrate conversions of the enzymatic esterification and transesterification were 98.7 and 95.1%, respectively. Also, the main product ratios in transesterification were above 99.0% with lipozyme TLIM as a catalyst because the hydrolysis reaction was hindered. The results of the physical and biological properties indicate that all esters had higher Clog  p values than their parent compounds. Also, the esters showed higher intracellular tyrosinase inhibitory and depigmentating activities than phenolic glycosides, azelaic acid (AA), and their physical mixtures due to their higher membrane penetration and tyrosinase inhibitory effects. In particular, piceid 6″- O -azelaic acid ester (PIA) showed the strongest inhibitory effect against melanin production. Its inhibitory rate was 77.4% at a concentration of 0.25 mM, about 4.2 times higher than that of arbutin (18.5%).