to a wide range of health benefits. In fact, anti-allergenic, anti-microbial, anti-inflammatory, anti-fungal, anti-tumoral properties [1][2][3][4] have all documented for flavonoids, yet it is their anti-oxidative related properties [5,6] which have really generated the most interest to date.The use of flavonoids in numerous cosmetic and pharmaceutic formulations seems very attractive. Unfortunately, the development of such products is seriously limited due to their poor solubility in lipophilic media thus limiting their use in oil-based foods and cosmetics. a solution to improve the hydrophobic nature of flavonoids consists in the esterification of the hydroxyl functions by fatty acids. Studies [7][8][9][10][11][12] have been investigated chemical and enzymatic acylation to improve flavonoid properties.The increasing concern of the consumers for food safety has pushed industries to the elimination of synthetic additives and their replacement by natural additives. The antioxidant of bamboo leaves (aOB), which is the trade name of bamboo-leaf extracts, has been approved as a natural food additive for food, edible oils, fried food and vegetable juices by Chinese Ministry of Health. The functional components of aOB include flavonoids, lactones and phenolic acids, and the highest content compound is isoorientin [13]. However, its use is also limited by weak solubility in lipidic matrices. To our knowledge, enzymatic acylation of flavonoids from aOB has seldom been studied.In order to evaluate and exploit the potential of the esters of aOB fully, it is extremely important to establish a simple, effective and relatively cheap method for preparation of esters for such testing. as such, this paper focuses on the optimization of enzymatic acylation of isoorientin from aOB by different lipases in different conditions with palmitic acids as acyl donor. AbstractThe utilization of bamboo-leaf extracts is limited by their weak solubility in lipidic media. as such, this study established an effective and relatively cheap method for preparation of ester of isoorientin isolated from bamboo-leaf extracts. acylation of isoorientin with palmitic acid was efficient in a system containing dried tert-amyl alcohol and molecular sieves, yielding from 22 to 90 % bioconversion with different conditions; in detail, several factors (the origin and the amount of the lipase, temperature and water content of the system) were investigated in depth with the effect on the performance of the acylation reaction in this paper. Thereafter high purity ester (95 %) was obtained following a two-step solvent purification procedure and a chromatographic separation. With 1 H and 13 C nuclear magnetic resonance spectroscopy analysis, single product was detected to be 6″-O-palmitate isoorientin ester. Introducing an acyl group into isoorientin significantly improved its lipophilicity yet slightly reduced their antioxidant activity.

This present study aims to establish a relatively cheap and effective method for preparation of ester of flavone isolated from bamboo‐leaf extracts. According to this method, the solubility of bamboo leaf extract in a lipid medium could be improved, which would expand the utilization of bamboo leaf extract. Acylation of flavone with oleic acid was efficient in a system containing dried tert‐amyl‐alcohol and molecular sieves. The bioconversion yield ranged from 24 to 63% in different conditions. the type of fatty acids, the amount of the lipase, water content and temperature of the system were investigated in detail to influence on the performance of the acylation reaction. High purity of ester (>95%) was obtained by a two‐step solvent purification procedure and chromatographic separation. Followed by the 1H and 13C nuclear magnetic resonance spectroscopy analysis, single product of 6′′‐O‐oleate isoorientin ester was detected. Introducing an acyl group into isoorientin significantly improved its lipophilicity yet slightly reduced their antioxidant activity, while its antioxidant activity still significantly better than VE.