Enzymatic acylation of isoorientin isolated from antioxidant of bamboo leaves with palmitic acid and antiradical activity of the acylated derivatives

Mini-Review on the Enzymatic Lipophilization of Phenolics Present in Plant Extracts with the Special Emphasis on Anthocyanins

Different plant extracts have the potential to be important sources of phenolic compounds. Their antibacterial, antifungal and antioxidant properties are of interest to researchers due to various possibilities for use in the pharmacy, cosmetic and food industries. Unfortunately, the direct application of phenolics in food is limited because of their hydrophilic nature and low solubility. The review is devoted to the recent advances in the methods of lipophilization of phenolic extracts along with the use of enzymes. The concept of extract modification instead of single compound modification is based on the expected synergistic effect of many phenolic compounds. The main focus is on the phenolic compounds found in fruits, flowers and leaves of different common and underutilized as well as medicinal, folk-medicinal or endemic plants. The compiled papers point to the great interest in the modification of anthocyanins, highly active but often unstable phenolics. Some examples of other flavonoids are also outlined. The possible applications of the lipophilized plant extracts are presented for improving the stability of edible oils, decreasing the content of acrylamide, exhibiting higher color stability in thermal processing and increasing the nutritional value.

Modification of flavonoids: methods and influences on biological activities

Flavonoids are important active ingredients in plant-based food, which have many beneficial effects on health. But the low solubility, poor oral bioavailability, and inferior stability of many flavonoids may limit their applications in the food, cosmetics, and pharmaceutical industries. Structural modification can overcome these shortcomings to improve and extend the application of flavonoids. The study of how to modify flavonoids and the influence of various modifications on biological activity have drawn great interest in the current literature. In this review, the working principles and operating conditions of modification methods were summarized along with their potential and limitations in terms of operational safety, cost, and productivity. The influence of various modifications on biological activities and the structure-activity relationships of flavonoids derivatives were discussed and highlighted, which may give guidance for the synthesis of highly effective active agents. In addition, the safety of flavonoids derivatives is reviewed, and future research directions of flavonoid modification research are discussed.

Investigation of acute, subacute and subchronic toxicities of anthocyanin derived acylation reaction products and evaluation of their antioxidant activities in vitro

Previously, anthocyanins were successfully acylated with lauric acid using Novozym 435 lipase, and the corresponding products were confirmed to have higher stability. As novel synthetic compounds, their toxicological safety has not been evaluated. Therefore, acute, subacute and subchronic toxicities of anthocyanin-lauric acid derivatives (ALDs) were investigated while their antioxidant activities were also evaluated in vitro. The acute toxicity results showed that the 50% lethal dose (LD₅₀) of ALDs in mice was >10 g kg^-1. Subsequently, the subacute toxicity test was conducted by oral administration of ALDs at doses of 0.63, 1.25 and 2.50 g kg^-1 for 28 days. No adverse effect of ALDs on body weight, food/water intake, organ coefficient and histology was observed. Though there were some fluctuations in AST and ALT, the tested biochemical parameters were maintained within the normal ranges. The subchronic toxicity test results demonstrated that less than 0.60 g of ALDs per kg BW intake did not affect mortality, body weight, food/water intake, gross pathology, histology, hematology and serum biochemistry. Furthermore, cyanidin-3-(6''-dodecanoyl)-glucoside, the main component of ALDs, had a beneficial reducing power and a strong DPPH˙, ABTS⁺˙, and O^2-˙ scavenging activity. This study provides an imperative reference to the safety of ALDs, suggesting their application as novel colorants or antioxidants in food and therapeutics.

Kinetics of Enzymatic Synthesis of Cyanidin-3-Glucoside Lauryl Ester and Its Physicochemical Property and Proliferative Effect on Intestinal Probiotics

The interest in anthocyanins used in food, cosmetic, and pharmaceutical industries has increased the research in order to improve their stability while maintaining bioactivity. In this work, cyanidin-3-glucoside lauryl ester (Cy3glc-C12) was enzymatically synthesized, using Novozym 435 as a catalyst, as well as to obtain a kinetic model for the bioprocess. Its liposolubility, UV–VIS absorbance property, thermostability, and potential proliferative effect on intestinal probiotics were also studied. The maximum conversion yield (68.7 ± 2.1%) was obtained with a molar ratio (substrate:donor) of 1:56, 435 16.5 g/L Novozym, temperature of 56 °C, and a time of 28 h via the acylation occurred at 6′′-OH position of the glucoside. The kinetics of the reaction is consistent with a ping-pong bi-bi mechanism and the parameters of the respective kinetic equations are reported. Compared with native Cy3glc, the liposolubility, pH resistivity and thermostability of Cy3glc-C12 were significantly improved. The growth kinetics of Bifidobacteria and Lactobacillus was established based on the Logistic equation, and Cy3glc-C12 could promote their proliferation especially during the logarithmic growth, in which lower pH and more bacteria population were found compared with those of media without anthocyanins. This research provided a reference for the industrial production of Cy3glc-C12 and extended its application to natural products in lipophilic systems.

Antioxidant capacity and hepatoprotective activity of myristic acid acylated derivative of phloridzin

The antioxidant activities in vitro and hepatoprotective effects against carbon tetrachloride (CCl₄) induced acute liver injury in vivo of myristic acid acylated derivative of phloridzin (PZM) were investigated. The PZM was obtained by enzymatic acylation of myristic acid and phloridzin (PZ). The antioxidant capability of PZM in vitro was evaluated by the ferric reducing antioxidant power assay (FRAP), 2,2'-Azinobis- 3-ethylbenzthiazoline-6-sulphonate (ABTS⁺·) and 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging assay. Mice were intragastrically treated with control or PZM (20, 40, and 80 mg/kg) for 5 days and intra-peritoneal injection with CCl₄. The enzymatic acylated synthesis of myristic acid and phloridzin was region-selective taken place on 6″-OH of phloridzin glycoside moiety and achieved 93% yield. PZM had a significantly higher total antioxidant ability, same scavenging ABTS⁺· ability and weaker scavenging DPPH· ability when compared to the parent PZ. The of aminotransferase serum activity and malondialdehyde hepatic activity were elevated (P < 0.015) after treatment with CCl₄, while the related liver enzymatic activities and glutathione concentration were lower. These changes were enhanced by PZM. Further studies showed that PZM reduced the interleukin-6 expression and stimulated liver regeneration caused by CCl₄. PZM attained good antioxidant capacity in vitro and had excellent hepatoprotective effects in vivo and better bioactivity compared to the parent phloridzin. The significance of hepatoprotective effect of phloridzin derivative against CCl₄-induced hepatotoxicity in mice is an important and new finding.

Kinetic study on the inhibition of xanthine oxidase by acylated derivatives of flavonoids synthesised enzymatically

Studies have reported that flavonoids inhibit xanthine oxidase (XO) activity; however, poor solubility and stability in lipophilic media limit their bioavailability and applications. This study evaluated the kinetic parameters of XO inhibition and partition coefficients of flavonoid esters biosynthesised from hesperidin, naringin, and rutin via enzymatic acylation with hexanoic, octanoic, decanoic, lauric, and oleic acids catalysed by Candida antarctica lipase B (CALB). Quantitative determination by ultra-high performance liquid chromatography–mass spectrometry (UHPLC–MS) showed higher conversion yields (%) for naringin and rutin esters using acyl donors with 8C and 10C. Rutin decanoate had higher partition coefficients (0.95), and naringin octanoate and naringin decanoate showed greater inhibitory effects on XO (IC₅₀ of 110.35 and 117.51 μM, respectively). Kinetic analysis showed significant differences (p < .05) between the flavonoids before and after acylation regarding K_m values, whereas the values for V_max were the same, implying the competitive nature of XO inhibition.

Cellular Transport of Esculin and Its Acylated Derivatives in Caco-2 Cell Monolayers and Their Antioxidant Properties in Vitro

Esculin has many pharmacological effects, but these are difficult to observe after oral administration owing to poor lipid solubility. In our previous study, five acylated derivatives with different acyl chain lengths (EA, EP, EO, EL, and EM) were synthesized to improve the lipophilicity of esculin. In this study, the bioavailability and antioxidant activity of the five derivatives were investigated. The logP of esculin, EA, EP, EO, EL, and EM were -1.1 ± 0.1, -0.3 ± 0.14, 0.1 ± 0.17, 1.6 ± 0.09, 2.4 ± 0.11, and 2.8 ± 0.18, and their P_app were 0.71 ± 0.02, 1.24 ± 0.18, 1.74 ± 0.11, 11.6 ± 3.6, 4.11 ± 1.03, and 2.64 ± 0.97 × 10^-6 cm/s, respectively. Besides, the bioavailability of EO, EL, and EM were seriously affected by carboxylesterase. The results of ABTS, ORAC, and DPPH assays indicated that the antiradical ability of the five derivatives did not exceed that of esculin. However, EA, EP, and EO showed more effective inhibition of AAPH-induced oxidative hemolysis than esculin did (p < 0.05), and EL and EM were less effective than esculin (p < 0.05). The mechanism was related to the distribution and localization of the derivatives in "oil-water interface" between the cytomembrane and the aqueous phase.

Enzymatic Acylation of Anthocyanin Isolated from Black Rice with Methyl Aromatic Acid Ester as Donor: Stability of the Acylated Derivatives

The enzymatic acylation of anthocyanin from black rice with aromatic acid methyl esters as acyl donors and Candida antarctica lipase B was carried out under reduced pressure. The highest conversion of 91% was obtained with benzoic acid methyl ester as acyl donor; cyanidin 3-(6″-benzoyl)-glucoside, cyanidin 3-(6″-salicyloyl)-glucoside, and cyanidin 3-(6″-cinnamoyl)-glucoside were successfully synthesized. This is the first report on the enzymatic acylation of anthocyanin from black rice with methyl aromatic esters as acyl donors and lipase as biocatalyst. Furthermore, the acylation with aromatic carboxylic acids enhanced both the thermostability and light resistivity of anthocyanin. In particular, cyanidin 3-(6″-cinnamoyl)-glucoside was the most stable among the three acylated anthocyanins synthesized.

Enzymatic synthesis, structural characterization and antioxidant capacity assessment of a new lipophilic malvidin-3-glucoside–oleic acid conjugate

Enzymatic synthesis of a novel lipophilic malvidin-3-glucoside–oleic acid conjugate for potential technological applications.

Acylation of Antioxidant of Bamboo Leaves with Fatty Acids by Lipase and the Acylated Derivatives' Efficiency in the Inhibition of Acrylamide Formation in Fried Potato Crisps

This study selectively acylated the primary hydroxyl groups on flavonoids in antioxidant of bamboo leaves (AOB) using lauric acid with Candida antarctica lipase B in tert-amyl-alcohol. The separation and isolation of acylated derivatives were performed using silica gel column chromatography with a mixture of dichloromethane/diethyl ether/methanol as eluents. Both thin layer chromatography and high-performance liquid chromatography analyses confirmed the high efficiency of the isolation process with the purified orientin-6″-laurate, isoorientin-6″-laurate, vitexin-6″-laurate, and isovitexin-6″-laurate that were obtained. The addition of AOB and acylated AOB reduced acrylamide formation in fried potato crisps. Results showed that 0.05% AOB and 0.05% and 0.1% acylated AOB groups significantly (p < 0.05) reduced the content of acrylamide in potato crisps by 30.7%, 44.5%, and 46.9%, respectively.