Lipase‐catalyzed regioselective synthesis of flavone C‐glucosides esters and high‐efficiency oil‐soluble antioxidant of bamboo leaves (eAOB‐o)

Abstract

AOB-w is a water-soluble antioxidant extracted from bamboo leaves, containing four flavone C-glucosides (orientin, isoorientin, vitexin, and isovitexin) as functional components. Flavone C-glucoside esters were firstly synthesized by three lipases (CALB, RM IM, and TL IM) in an organic solvent system or a solvent-free system. Results indicated that C12 fatty acid ester exhibited the optimal antioxidant capacity; CALB was the most efficient lipase in both systems; and higher conversion yields were achieved in a solvent-free system. Highest conversion was obtained with 1% water content for CALB and 2% water content for RM IM and TL IM. All lipases displayed absolute 6 00 -regioselectivities with monoester. It is required to consider both hydrophobicity and antioxidant capacity in order to prepare high-efficiency oil-soluble antioxidants. Regression equations were built up to illuminate the relationship between conversion yield of flavone C-glucoside and antioxidant capacity of its corresponding ester. The highest antioxidant capacity could be achieved when conversion yield was nearly 60% for flavone C-glucosides. Based on reaction parameters of flavone C-glucosides, high-efficiency eAOB-o was prepared, which could be expected as an excellent oil-soluble antioxidant in lipids.Practical applications: Water-soluble antioxidant of bamboo leaves (AOB-w) is a natural food antioxidant extracted from bamboo leaves, with four flavone C-glucosides (orientin, isoorientin, vitexin, and isovitexin) as functional components. This study aimed to provide a practical procedure to prepare high-efficiency lipid antioxidant by enzymatic acylation. Based on the optimal parameters from the synthesis of flavone C-glucoside esters, a high-efficiency oil-soluble antioxidant of bamboo leaves (eAOB-o) was prepared. eAOB-o exhibited higher antioxidant capacity than cAOB-o, which has been approved as a food antioxidant in China. Abbreviations: AOB-w, water-soluble antioxidant of bamboo leaves; BLFs, bamboo leaves flavonoids; CALB, Candida antarctica lipase B; cAOB-o, oil-soluble antioxidant of bamboo leaves synthesized by chemical acylation; eAOB-o, oil-soluble antioxidant of bamboo leaves synthesized by enzyme; ESI À , electrospray negative ionization; LDL, lowdensity lipoprotein; MS, mass spectrum; RM IM, Rhizomucor miehei lipase; TLC, thin-layer chromatography; TL IM, Thermomyces lanuginosus lipase 1636Eur.

Lipophilized Grape Seed Proanthocyanidin Derivatives as Novel Antioxidants

“…In biocatalytic systems, substrates must be dispersed from the solvent to the active center of the enzyme, and the synthesized products also need to diffuse from the active center enzymes to the reaction medium, which suggested that the choice of solubilized substrate must be considered in a suitable reaction medium. 27 Solvents affect the catalytic ability of the enzyme by regulating the three-dimensional conformation of the protein and therefore can significantly change the total conversion and reaction rate. 28 The difference in solvent effect is mainly due to log p and the dielectric constant, and a low log p solvent favors high conversion rates.…”

Enzymatic synthesis of bioactive compounds with high potential for cosmeceutical application

“…Irilone, chrysin, and dihydromyricetin acetate have been synthesized by Pseudomonas (syn Burkholderia ) cepacia lipases and an immobilized lipase from P. expansum (Nazir et al 2009 ; Chebil et al 2007 ; Li et al 2015 ). Orientin, vitexin, salicin fatty acid esters, and helicin butyrate have been synthesized by CALB (Liu et al 2015 ; Katsoura et al 2007 ). Silibyn, which occurs in nature as an equimolar mixture of two diastereoisomers (A and B) with different biological activities, has been acylated by CALB at the C-23 position producing new anti-viral and anti-tumor compounds (Gazak et al 2010 ).…”

Enzymatic Acylation of Flavonoids from Bamboo Leaves: Improved Lipophilicity and Antioxidant Activity for Oil-Based Foods

“…9 Furthermore, antioxidants from bamboo leaves were enzymatically acylated with fatty acids of different chain lengths, which significantly improved their lipophilicity and increased the oxidative stability of palm oil, lard, and fried potato chips. 10,11 In other studies, malvidin-3-glucoside was enzymatically acylated with stearoyl chloride, oleic acid, and saturated fatty acids of different chain lengths, which improved the lipid solubility of malvidin-3-glucoside to a certain extent. 12−14 The introduction of lauric acid into anthocyanins from blackcurrants (Ribes nigrum L.), including delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside, and cyanidin-3-O-rutinoside, and from alpine bearberries (Arctostaphylos alpine L.), including cyanidin-3-O-galactoside, significantly improved the lipid solubility and thermostability of the modified anthocyanins.…”

“…For example, Ma et al grafted fatty acids of different chain lengths onto isoorientin and isovitexin isolated from bamboo leaf extracts through enzymatic acylation, which significantly improved their lipophilicity but reduced their antioxidant activity . Furthermore, antioxidants from bamboo leaves were enzymatically acylated with fatty acids of different chain lengths, which significantly improved their lipophilicity and increased the oxidative stability of palm oil, lard, and fried potato chips. , In other studies, malvidin-3-glucoside was enzymatically acylated with stearoyl chloride, oleic acid, and saturated fatty acids of different chain lengths, which improved the lipid solubility of malvidin-3-glucoside to a certain extent. − The introduction of lauric acid into anthocyanins from blackcurrants (Ribes nigrum L.), including delphinidin-3- O -glucoside, delphinidin-3- O -rutinoside, cyanidin-3- O -glucoside, and cyanidin-3- O -rutinoside, and from alpine bearberries (Arctostaphylos alpine L.), including cyanidin-3- O -galactoside, significantly improved the lipid solubility and thermostability of the modified anthocyanins. , Moreover, recent studies have reported that introducing aromatic acid groups with strong hydrophobicity can also improve the lipid solubility of flavonoids. Cai et al successfully prepared lipid-soluble anthocyanins by grafting cinnamic acids onto anthocyanins from bilberries, which also improved their capacity to inhibit lipid peroxidation .…”