Selective enzymatic lipophilization of anthocyanin glucosides from blackcurrant (Ribes nigrum L.) skin extract and characterization of esterified anthocyanins

Progress on molecular modification and functional applications of anthocyanins

Anthocyanins have attracted a lot of attention in the fields of natural pigments, food packaging, and functional foods due to their color, antioxidant, and nutraceutical properties. However, the poor chemical stability and low bioavailability of anthocyanins currently limit their application in the food industry. Various methods can be used to modify the structure of anthocyanins and thus improve their stability and bioavailability characteristics under food processing, storage, and gastrointestinal conditions. This paper aims to review in vitro modification methods for altering the molecular structure of anthocyanins, as well as their resulting improved properties such as color, stability, solubility, and antioxidant properties, and functional applications as pigments, sensors and functional foods. In industrial production, by mixing co-pigments with anthocyanins in food systems, the color and stability of anthocyanins can be improved by using non-covalent co-pigmentation. By acylation of fatty acids and aromatic acids with anthocyanins before incorporation into food systems, the surface activity of anthocyanins can be activated and their antioxidant and bioactivity can be improved. Various other chemical modification methods, such as methylation, glycosylation, and the formation of pyranoanthocyanins, can also be utilized to tailor the molecular properties of anthocyanins expanding their range of applications in the food industry.

Enzymatic acylation of cyanidin-3-O-glucoside with aromatic and aliphatic acid methyl ester: Structure-stability relationships of acylated derivatives

Anthocyanins are water-soluble pigments, but they tend to be unstable in aqueous solutions. Modification of their molecular structure offers a viable approach to alter their intrinsic properties and enhance stability. Aromatic and aliphatic acid methyl esters were used as acyl donors in the enzymatic acylation of cyanidin-3-O-glucoside (C3G), and their analysis was conducted using ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). The highest conversion rate achieved was 96.41 % for cyanidin-3-O-(6″-feruloyl) glucoside. Comparative evaluations of stability revealed that aromatic acyl group-conjugated C3G exhibited superior stability enhancement compared with aliphatic acyl group derivatives. The stability of aliphatic C3G decreased with increasing carbon chain length. The molecular geometries of different anthocyanins were optimized, and energy level calculations using density functional theory (DFT) identified their sites with antioxidant activities. Computational calculations aligned with the in vitro antioxidant assay results. This study provided theoretical support for stabilizing anthocyanins and broadened the application of acylated anthocyanins as food colorants and nutrient supplements.

Chemo- and regio-selective enzymatic lipophilisation of rutin, and physicochemical and antioxidant properties of rutin ester derivatives

Enzymes are one of the most powerful tools in organic Green Chemistry and enzymatic reactions offer numerous advantages like regio- and enantio-selectivity along with their eco-friendly and sustainable nature. More specifically, lipases can catalyse both ester hydrolysis and formation depending on the nature of the substrate and water content. Herein, the focus is on the development of an enzymatically catalysed lipophilisation of natural compounds using lipases of microbial origin and the investigation of the optimal reaction conditions, aiming ultimately to ameliorate the compounds' properties. The flavonoid disaccharide rutin (quercetin-3-O-rutinoside) was the model compound on which the acylation protocol was built, allowing an efficient procedure to be established, while simultaneously offering the possibility of developing rapid, clear and robust methodologies, using state-of-the-art techniques, for analysis and purification of the synthesized compounds. An optimal 72 h reaction at 55 °C, using Candida antarctica lipase B immobilized on acrylic resin, combined with silicon dioxide as dehydrating agent, followed by product purification, achieved conversion ratios up to 50%. Full characterization and evaluation of the physicochemical and antioxidant properties of the esterified compounds was obtained. The lipophilicity of the rutin esters produced increased with increasing alkyl chain length, yet antioxidant properties were unaffected in comparison with the parent compound. A preparatively useful acylation protocol was established, allowing full investigation into the properties of the acylated compounds. It is also applicable for use on mixtures of compounds as most natural products are found in nature in mixtures and such a development greatly enhances the potential of this method for future commercial applications.

The health-promoting anthocyanin petanin in Lycium ruthenicum fruit: a promising natural colorant

Acylated anthocyanins derived from dietary sources have gained significant attention due to their health-promoting properties and potential as natural colorants with high stability. However, exploration of the functional food products using acylated anthocyanins enriched in fruits and vegetables remains largely delayed in food industries. The black goji (Lycium ruthencium) fruit (LRF) is a functional food that is extensively used due to its exceptionally high levels of acylated anthocyanins, including petanin. This review provides a comprehensive summary of the functional properties and anthocyanin components of LRF. The stability, bioaccessibility, bioavailability, and bioactivities of petanin, the major anthocyanin component, are compared with those of LRF anthocyanin extracts and other food sources. Furthermore, the biosynthetic pathway and regulatory network of petanin in LRF are proposed and constructed, respectively. The key genes that could be potentially used for metabolic engineering to produce petanin are predicted. Finally, the potential application of petanin derivatives in the food industry is also discussed. This review presents comprehensive and systematic information about the dual-function of petanin as a bioactive component and a promising natural colorant for future food industrial applications.

Pharmacological Activities and Chemical Stability of Natural and Enzymatically Acylated Anthocyanins: A Comparative Review

Anthocyanins (ANCs) are naturally occurring water-soluble pigments responsible for conferring red, blue, and purple colors to fruits, vegetables, flowers, and grains. Due to their chemical structure, they are highly susceptible to degradation by external factors, such as pH, light, temperature, and oxygen. Naturally acylated anthocyanins have proven to be more stable in response to external factors and exhibit superior biological effects as compared with their non-acylated analogues. Therefore, synthetic acylation represents a viable alternative to make the application of these compounds more suitable for use. Enzyme-mediated synthetic acylation produces derivatives that are highly similar to those obtained through the natural acylation process, with the main difference between these two pathways being the catalytic site of the enzymes involved in the synthesis; acyltransferases catalyze natural acylation, while lipases catalyze synthetic acylation. In both cases, their active sites perform the addition of carbon chains to the hydroxyl groups of anthocyanin glycosyl moieties. Currently, there is no comparative information regarding natural and enzymatically acylated anthocyanins. In this sense, the aim of this review is to compare natural and enzyme-mediated synthetic acylated anthocyanins in terms of chemical stability and pharmacological activity with a focus on inflammation and diabetes.

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

The goal of this study was to expand the applications of bamboo leaf flavonoids (BLFs) by improving their lipophilicity through enzymatic acylation with vinyl cinnamate. Characterization of the acylated BLFs using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, high-resolution electrospray ionization mass spectrometry, electrospray ionization with tandem mass spectrometry, and ¹H nuclear magnetic resonance spectroscopy indicated that acylation occurred at the C6-OH position of glucoside moieties. The highest degree of acylation (18.61%) was obtained by reacting BLFs with vinyl cinnamate (1:5, w/w) at 60 °C for 48 h. Acylation significantly improved the lipophilicity of BLFs and their capacity to inhibit lipid peroxidation, as evidenced by the reduced production of lipid hydroperoxides and malondialdehyde in rapeseed oil and rapeseed oil-in-water emulsions during storage at 37 °C for 15 days. The study findings provide important data that will enable the use of BLFs in lipid or lipophilic matrices, such as oil-based foods.

Anthocyanin accumulation in grape berry flesh is associated with an alternative splicing variant of VvMYBA1

Anthocyanins are flavonoids that contribute to the color of grape berries and are an essential component of grape berry and wine quality. Anthocyanin accumulation in grape berries is dependent on the coordinated expression of genes encoding enzymes in the anthocyanin pathway that are principally regulated at the transcriptional level, with VvMYBA1 as the main transcriptional regulator in grapes. Alternative splicing (AS) events in VvMYBA1, however, have not been examined. In the present study, VvMYBA1-L, an AS variant of VvMYBA1, was identified in 'ZhongShan-Hong' (ZS-H) and its offspring. The AS variant is characterized by a deletion in the third exon of the open reading frame (ORF) of VvMYBA1-L, resulting in the early termination of the encoded protein. Overexpression of VvMYBA1-L in grape berries resulted in delayed flesh coloration and ectopic overexpression of VvMYBA1-L in tobacco inhibited the coloration of petals. Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays revealed that VvMYBA1-L interacts with VvMYBA1. Dual luciferase assays indicated that co-infiltration of VvMYC1 and VvMYBA1 significantly activated the promoter regulated expression of VvCHS3, VvDFR, VvUFGT, and VvF3H. In the presence of VvMYBA1-L, however, the induction effect of VvMYBA1 on the indicated promoters was significantly inhibited. Our findings provide insight into the essential role of VvMYBA1 and its variant, VvMYBA1-L, in regulating anthocyanin accumulation in grape berry flesh.

Enzymatic acylation of cyanidin-3-O-glucoside in raspberry anthocyanins for intelligent packaging: Improvement of stability, lipophilicity and functional properties

Anthocyanins (ACNs) as one category of water-soluble flavonoid pigments are increasingly employed in pH sensing indicator applications for monitoring food freshness. Nevertheless, considering that anthocyanins are sensitive to environmental factors, their practical applications in food industries are still rather limited. In order to improve the stability of anthocyanins and capitalize upon their application in pH-color responsive intelligent packaging, this study aims to graft octanoic aid onto raspberry anthocyanins catalyzed by immobilized Candida antarctica lipase B (Novozymes 435). Structural analyses based on Fourier transform infrared spectroscopy (FTIR), UV-Vis, liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR) revealed that octanoic acid was regioselective grafted onto the 6-OH position of its glucoside. The acylation efficiency of C3G by octanoic acid up to 47.1%. The octanoic acid moiety was found to improve lipophilicity, antioxidant activity and stability of C3G. In addition, acylated derivative also maintained the pH-color response characteristics of nature ACNs and exhibited excellent NH3 response properties. These results indicated that acylated anthocyanins exhibit potential application as intelligent packaging indicator for monitoring food freshness.

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.

Acylation of Anthocyanins and Their Applications in the Food Industry: Mechanisms and Recent Research Advances

Anthocyanins are extensively used as natural non-toxic compounds in the food industry due to their unique biological properties. However, the instability of anthocyanins greatly affects their industrial application. Studies related to acylated anthocyanins with higher stability and increased solubility in organic solvents have shown that the acylation of anthocyanins can improve the stability and fat solubility of anthocyanins. However, relevant developments in research regarding the mechanisms of acylation and applications of acylated anthocyanins are scarcely reviewed. This review aims to provide an overview of the mechanisms of acylation and the applications of acylated anthocyanins in the food industry. In the review, acylation methods, including biosynthesis, semi-biosynthesis, and chemical and enzymatic acylation, are elaborated, physicochemical properties and biological activities of acylated anthocyanins are highlighted, and their application as colourants, functionalizing agents, intelligent indicators, and novel packaging materials in the food industry are summarized. The limitations encountered in the preparation of acylated anthocyanins and future prospects, their applications are also presented. Acylated anthocyanins present potential alternatives to anthocyanins in the food industry due to their functions and advantages as compared with non-acylated analogues. It is hoped that this review will offer further information on the effective synthesis and encourage commercialization of acylated anthocyanins in the food industry.

Catalytic Routes to Produce Polyphenolic Esters (PEs) from Biomass Feedstocks

Polyphenolic esters (PEs) are valuable chemical compounds that display a wide spectrum of activities (e.g., anti-oxidative effects). As a result, their production through catalytic routes is an attractive field of research. The present review aims to discuss recent studies from the literature regarding the catalytic production of PEs from biomass feedstocks, namely, naturally occurred polyphenolic compounds. Several synthetic approaches are reported in the literature, mainly bio-catalysis and to a lesser extent acid catalysis. Immobilized lipases (e.g., Novozym 435) are the preferred enzymes thanks to their high reactivity, selectivity and reusability. Acid catalysis is principally investigated for the esterification of polyphenolic acids with fatty alcohols and/or glycerol, using both homogeneous (p-toluensulfonic acid, sulfonic acid and ionic liquids) and heterogeneous (strongly acidic cation exchange resins) catalysts. Based on the reviewed publications, we propose some suggestions to improve the synthesis of PEs with the aim of increasing the greenness of the overall production process. In fact, much more attention should be paid to the use of new and efficient acid catalysts and their reuse for multiple reaction cycles.

A review on enzymatic acylation as a promising opportunity to stabilizing anthocyanins

Anthocyanins are naturally occurring bioactive compounds found mainly in fruits, vegetables, and grains. They are usually extracted due to their biological properties and great potential for technological applications. These compounds have characteristic pH-dependent colorations that are natural dyes since they come in different colors. However, they are susceptible to processing conditions, remarkably light, temperature, and oxygen. The acylated anthocyanins showed better stability characteristics, and therefore, an acylation process of these compounds could improve their applications. The enzymatic acylation was effective and showed promising results. The current review provides an overview of the works that performed enzymatic acylation of anthocyanins and studies on the stability, antioxidant activity, and lipophilicity. In general, enzymatically acylated anthocyanins showed better stability to light and temperature than non-acylated compounds. In addition, they were liposoluble, a characteristic that allows their addition to products with lipid matrices. The results showed that these compounds formed by enzymatic acylation have perspectives of application mainly as natural colorants in food products. Therefore, the enzymatic acylation of anthocyanins appears viable to increase the industrial applicability of anthocyanins. There are still some gaps to be filled in process optimization, the reuse of enzymes, and toxicity analysis of the acylated compounds formed.

Natural and Synthetic Flavylium-Based Dyes: The Chemistry Behind the Color

Flavylium compounds are a well-known family of pigments because they are prevalent in the plant kingdom, contributing to colors over a wide range from shades of yellow-red to blue in fruits, flowers, leaves, and other plant parts. Flavylium compounds include a large variety of natural compound classes, namely, anthocyanins, 3-deoxyanthocyanidins, auronidins, and their respective aglycones as well as anthocyanin-derived pigments (e.g., pyranoanthocyanins, anthocyanin-flavan-3-ol dimers). During the past few decades, there has been increasing interest among chemists in synthesizing different flavylium compounds that mimic natural structures but with different substitution patterns that present a variety of spectroscopic characteristics in view of their applications in different industrial fields. This Review provides an overview of the chemistry of flavylium-based compounds, in particular, the synthetic and enzymatic approaches and mechanisms reported in the literature for obtaining different classes of pigments, their physical-chemical properties in relation to their pH-dependent equilibria network, and their chemical and enzymatic degradation. The development of flavylium-based systems is also described throughout this Review for emergent applications to explore some of the physical-chemical properties of the multistate of species generated by these compounds.

Identification and Characterization of a Novel Carboxylesterase Belonging to Family VIII with Promiscuous Acyltransferase Activity Toward Cyanidin-3-O-Glucoside from a Soil Metagenomic Library

An alkaline esterase, designated as EstXT1, was identified through functional screening from a metagenomic library. Sequence analysis revealed that EstXT1 belonged to the family VIII carboxylesterases and contained a characteristic conserved S-x-x-K motif and a deduced catalytic triad Ser56-Lys59-Tyr165. EstXT1 exhibited the strongest activity toward methyl ferulate at pH 8.0 and temperature 55°C and retained over 80% of its original activity after incubation in the pH range of 7.0-10.6 buffers. Biochemical characterization of the recombinant enzyme showed that it was activated by Zn²⁺ and Co²⁺ metal ion, while inhibited by Cu²⁺ and CTAB. EstXT1 exhibited significant promiscuous acyltransferase activity preferred to the acylation of benzyl alcohol acceptor using short-chain pNP-esters (C2-C8) as acyl-donors. A structure-function analysis indicated that a WAG motif is essential to acyltransferase activity. This is the first report example that WAG motif plays a pivotal role in acyltransferase activity in family VIII carboxylesterases beside WGG motif. Further experiment indicated that EstXT1 successfully acylated cyanidin-3-O-glucoside in aqueous solution. The results from the current investigation provided new insights for the family VIII carboxylesterase and lay a foundation for the potential applications of EstXT1 in food and biotechnology fields.

Enrichment and purification of red pigments from defective mulberry fruits using biotransformation in a liquid-liquid-solid three-phase system

A large number of defective mulberries are discarded each year because mulberries are easy to break. The red pigments from defective mulberries are recognized as the sustainable sources of anthocyanins extracted from nature. Cyanidin-3-O-rutinoside and cyanidin-3-O-glucoside are the main components of mulberry red pigments, accounting for 50% and 40% of the total, respectively. Cyanidin-3-O-glucoside exhibits anticancer, hypoglycemic, and liver and visceral protection properties. Cyanidin-3-O-glucoside can be prepared by enzymatically hydrolyzing the rhamnosidase bond of cyanidin-3-O-rutinoside. To obtain mulberry red pigment with a high purity of cyanidin-3-O-glucoside, immobilized α-L-rhamnosidase was added to the aqueous two-phase system to construct a liquid-liquid-solid three-phase enzyme catalytic system. After optimization, the three-phase system was composed of 27.12% (w/w) ethanol, 18.10% (w/w) ammonium sulfate, 15% (w/w) mulberry juice, 4.24% (w/w) immobilized α-L-rhamnosidase, and 35.54% (w/w) pure water. The three-phase system was employed to enrich and purify cyanidin-3-O-glucoside at pH 5 and 45 °C for 1 h. The purity of cyanidin-3-O-glucoside was increased from 40 to 82.42% with cyanidin-3-O-rutinoside conversion of 60.68%. The immobilized α-L-rhamnosidase could be reused seven times, maintaining a relative activity of over 50%. Overall, the developed system provided an efficient and simple approach for high purity mulberry red pigment production and recycling in the field of sustainable agriculture. Graphical abstract.

Comparative assessment of three RNA extraction methods for obtaining high-quality RNA from Candida viswanathii biomass

Isolating high quality RNA is a limiting factor in molecular analysis, since it is the base for transcriptional studies. The RNA extraction method can directly affect the RNA quality and quantity, as well as, its overall cost. The industrial importance of the yeast genus Candida in several sectors comes from their capacity to produce Lipases. These enzymes are one of the main metabolites produced by some Candida species, and it has been shown that Candida yeast can biodegrade petroleum hydrocarbons and diesel oil from biosurfactants that they can produce, a feature that turns these organisms into potential combatants for bioremediation techniques. Thus, this study aimed to determine an efficient method for isolating high quality RNA from Candida viswanathii biomass. To achieve this aim, three different RNA extraction methods, TRIzol, Hot Acid Phenol, and CTAB (Cetyltrimethylammonium Bromide), were tested. The three tested methods allowed the isolation of high-quality RNA from C. viswanathii biomass and yielded suitable RNA quantity for carrying out RT-qPCR studies. In addition, all methods displayed high sensitivity for the expression analysis of the CvGPH1 gene through RT-qPCR, with TRIzol and CTAB showing the best results and the CTAB method displaying the best cost-benefit ratio (US$0.35/sample).

Cyanidin-3-glucoside Lipophilic Conjugates for Topical Application: Tuning the Antimicrobial Activities with Fatty Acid Chain Length

Background: Natural anthocyanins present a low solubility in lipophilic media, which compromises their effective application in lipophilic systems. In this work, cyanidin-3-O-glucoside (Cy3glc) was esterified by the addition of fatty acids with increasing chain-lengths and a structure-activity relationship was performed towards the description of the best analog for skin-care applications. Methods: By enzymatic hemi-synthesis, it was possible to obtain 5 structurally related derivatives of cyanidin-3-O-glucoside with successive C2 increments in the aliphatic chain. The stability in hanks buffer and DMEM with or without FBS was followed by HPLC. The cytotoxicity against keratinocytes was evaluated by MTT assay. The antioxidant capacity was determined by using the fluorescent probe DCF-DA. The effect on enzyme activity was evaluated towards tyrosinase, collagenase, and elastase enzymes by colorimetric assays. MIC and MBC values were obtained against reference strains and against multidrug-resistant isolates. Results: In physiological conditions, cy3glc−fatty acid derivatives are more stable and may be converted to the native anthocyanin. The 5 conjugates showed lower antioxidant capacity and enzymatic inhibitory activities in comparison to the anthocyanin precursor. However, concerning the antibacterial activity, the insertion of a fatty acid chain sprouted the antibacterial activity, showing a clear biphasic effect and a more effective effect on Gram-positive bacteria. Conclusions: Cy3glc-C10 was the most effective compound considering the antimicrobial activity, although a general reduction was observed among the other activities evaluated. This work prompt further assays with a different panoply of derivatives ranging other features including saturation vs. unsaturation, even vs. odd carbon content and linear vs. branched.

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.

Disaccharide anthocyanin delphinidin 3-O-sambubioside from Hibiscus sabdariffa L.: Candida antarctica lipase B-catalyzed fatty acid acylation and study of its color properties

Enzymatic lipophilization is an important process to extend the use of anthocyanins in lipidic media. In this work delphinidin 3-O-sambubioside (Dp3sam) isolated from Hibiscus sabdariffa L. flower was esterified with octanoic acid using Candida antarctica lipase B. The physical-chemical properties of the new lipophilic pigment were studied by UV-vis spectroscopy. Dp3sam with chloride, acetate and formate as counter ions were employed to study the lipophilization reaction. The hydrolysis of the reagent was avoided with a formate counter ion and the expected product was achieved with a noteworthy change of solubility. 1D and 2D NMR characterization of Dp3sam-C8 confirmed that the lipophilization took place at the primary alcohol of the glucoside moiety. Overall, the Dp3sam-C8 ester presents a stabilization of the quinoidal base (blue color) at neutral or moderate alkaline pH, which foresees a potential use of this pigment as a broad kind of industries on lipo-soluble formulations.

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.

Highly Efficient Regioselective Decanoylation of Hyperoside Using Nanobiocatalyst of Fe3O4@PDA-Thermomyces lanuginosus Lipase: Insights of Kinetics and Stability Evaluation

The immobilization of Thermomyces lanuginosus lipase on polydopamine-functionalized Fe₃O₄ magnetic nanoparticles (Fe₃O₄@PDA-TLL) as a nanobiocatalyst was successfully performed for the first time, and the Fe₃O₄@PDA-TLL was used for regioselective acylation of natural hyperoside with vinyl decanoate. The effects of several crucial factors, such as the reaction solvent, substrate molar ratio, temperature, and immobilized enzyme dosage, were investigated. Under optimum conditions, the reaction rate, 6″-regioselectivity, and maximum substrate conversion were as high as 12.6 mM/h, 100%, and 100%, respectively. An operational stability study demonstrated that the immobilized enzyme could maintain 90.1% of its initial maximum conversion even after reusing it five times. In addition, further investigations on the kinetic parameters, like V_max, K_m, V_max/K_m, and E_a, also revealed that the biocompatible Fe₃O₄@PDA could act as an alternative carrier for the immobilization of different enzymes.

Preparation and pH Controlled Release of Fe3O4/Anthocyanin Magnetic Biocomposites

Anthocyanins are a class of antioxidants extracted from plants, with a variety of biochemical and pharmacological properties. However, the wide and effective applications of anthocyanins have been limited by their relatively low stability and bioavailability. In order to expand the application of anthocyanins, Fe3O4/anthocyanin magnetic biocomposite was fabricated for the storage and release of anthocyanin in this work. The magnetic biocomposite of Fe3O4 magnetic nanoparticle-loaded anthocyanin was prepared through physical intermolecular adsorption or covalent cross-linking. Scanning electron microscopy (SEM), Dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and thermal analysis were used to characterize the biocomposite. In addition, the anthocyanin releasing experiments were performed. The optimized condition for the Fe3O4/anthocyanin magnetic biocomposite preparation was determined to be at 60 °C for 20 h in weak alkaline solution. The smooth surface of biocomposite from SEM suggested that anthocyanin was coated on the surface of the Fe3O4 particles successfully. The average size of the Fe3O4/anthocyanin magnetic biocomposite was about 222 nm. Under acidic conditions, the magnetic biocomposite solids could be repeatable released anthocyanin, with the same chemical structure as the anthocyanin before compounding. Therefore, anthocyanin can be effectively adsorbed and released by this magnetic biocomposite. Overall, this work shows that Fe3O4/anthocyanin magnetic biocomposite has great potential for future applications as a drug storage and delivery nanoplatform that is adaptable to medical, food and sensing.

Anti-proliferation activities of Oryza sativa L. anthocyanins-Hohenbuehelia serotina polysaccharides complex after in vitro gastrointestinal digestion

In order to improve the bioavailability of Oryza sativa L. anthocyanins, we fabricated Oryza sativa L. anthocyanins-Hohenbuehelia serotina polysaccharides (OSA-HSP) complex and investigated its anti-proliferation activities taking into account its changes along simulated gastrointestinal digestion in vitro. Results showed that OSA mainly composed by delphinidin, cyanidin, petunidin, malvidin and their derivatives was combined with HSP through electrostatic interaction. OSA-HSP complex belonged to non-crystalline substance, and had compact and laminar structural characteristics. Under simulated gastrointestinal digestion, OSA-HSP complex significantly prevented the degradation of anthocyanins, and presented sustain release effect. However, the anti-proliferation activities of OSA-HSP complex digested by different gastrointestinal process were remarkably changed, especially after small intestinal digestion. HeLa cells treated with OSA-HSP complex exhibited pro-apoptosis characteristics by triggering endogenous mitochondrial apoptosis pathway through activating the expressions of Bax, cytochrome c and Caspase-3 as well as inhibiting the expression of Bcl-2. These findings provided new insight to improve the bioavailability of anthocyanins in functional foods and tumor therapy.

Blackcurrants (Ribes nigrum): A Review on Chemistry, Processing, and Health Benefits

Blackcurrants (BC; Ribes nigrum) are relatively new to the U.S. market; however, they are well known and popular in Europe and Asia. The use of BC has been trending worldwide, particularly in the United States. We believe that demand for BC will grow as consumers become aware of the several potential health benefits these berries offer. The objectives of this review were to provide an up-to-date summary of information on BC based on articles published within the last decade; furthermore, to provide the food industry insights into possibilities for the utilization of BC. The chemistry, processing methods, and health benefits have been highlighted in addition to how the environment and variety impact the chemical constituents of BC. A search for journal publications on BC was conducted, which included keywords such as chemical characterization, health benefits, processing, technologies, anthocyanins (ANC), and proanthocyanidins. This review provides up-to-date information available on the subject. In conclusion, BC and their products have industrial uses from which extractions can be made to produce natural pigments to be used as food additives. BC contain flavonoids, specifically ANC, which provide the fruits with their purple color. BC are a rich source of phytochemicals with potent antioxidant, antimicrobial, and anti-inflammatory properties. Also, BC have the potential to improve overall human health particularly with diseases associated with inflammation and regulation of blood glucose.

Chemical compositions and α-glucosidase inhibitory effects of anthocyanidins from blueberry, blackcurrant and blue honeysuckle fruits

The chemical compositions and α-glucosidase inhibitory activities of anthocyanins extracted from blueberry, blackcurrant and blue honeysuckle fruits and their acid hydrolysates (anthocyanidins) were analysed. Those anthocyanins were glycosidic anthocyanins that converted to anthocyanidins during acid hydrolysis, leading to increases in their α-glucosidase inhibitory activities (expressed as IC₅₀ values) from 0.232, 0.152 and 0.188 to 0.113 to 0.005 and 0.025 mg/mL. The potential inhibitory mechanism of these anthocyanidins was then investigated through inhibition kinetics, fluorescence quenching and docking simulations. The results showed the following: 1) all anthocyanidins were mixed-type inhibitors of α-glucosidase and they bind more tightly to free α-glucosidase as compared to the α-glucosidase-substrate complex; 2) anthocyanidin inhibition of α-glucosidase was a static procedure, presumably driven by hydrophobic associations and hydrogen bonding; and 3) all anthocyanidins were inserted into the active site of α-glucosidase and avoided the entrance of p-nitrophenyl-a-D-glucopyranoside. This study is valuable for anthocyanidins as potential α-glucosidase inhibitors.

Enzymatic acylation of blackcurrant (Ribes nigrum) anthocyanins and evaluation of lipophilic properties and antioxidant capacity of derivatives

Anthocyanin-rich fractions isolated from blackcurrant (Ribes nigrum L.) including delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside were enzymatically acylated with lauric acid. All the four anthocyanins were successfully monoacylated, and their relative proportions did not affect the conversion yield. The acylation occurred at the 6″-OH position of the glucosides and at the rhamnose 4‴-OH of the rutinosides. The rutinoside moieties of the anthocyanins were successfully acylated for the first time, and the corresponding acylation sites were verified by NMR analysis. The acylation enhanced the lipophilicity. The hydrophilic anthocyanin rutinosides were more lipophilic after acylation. Introducing lauric acid into the anthocyanins significantly improved the thermostability and capacity to inhibit lipid peroxidation and maintained UV-vis absorbance and antioxidant activity. This research provides important insights into acylation of mixed anthocyanins with different glycosyl moieties.

Enhancing the Potential Exploitation of Food Waste: Extraction, Purification, and Characterization of Renewable Specialty Chemicals from Blackcurrants ( Ribes nigrum L.)

Natural colorants were extracted from renewable botanical sources, specifically waste epicarp from the blackcurrant fruit pressing industry. A process was developed which used acidified water extraction followed by a solid-phase extraction (SPE) purification stage which allowed the production of an anthocyanin-rich extract in good yields (ca. 2% w/ w based on dry weight of raw material). The components in the extracts were extensively characterized by HPLC, mass spectrometry, IR, NMR, and UV-vis spectroscopy. HPLC confirmed presence of four anthocyanins: delphinidin-3- O-rutinoside (45%), cyanidin-3- O-rutinoside (31%), and the corresponding glucosides at 16% and 8%, respectively. On sequential liquid-liquid aqueous-organic partitioning of the post-SPE sample, monomeric anthocyanins (54.7%) and polymeric anthocyanins (18%) were found in the aqueous layer with 3- O-rutinosides of myricetin (3.1%) and quercetin (3.2%), while isopropylacetate achieved selective extraction of caffeic acid (3%), p-coumaric acid (5%), and myricetin (2.5%) and quercetin (3.2%) aglycons. 3- O-Glucosides of myricetin (3.1%) and quercetin (2%), along with nigrumin- p-coumarate (1%) and nigrumin ferulate (0.5%) were selectively extracted from the remaining aqueous fraction using ethyl acetate. This allowed for near total quantification of the blackcurrant extract composition.

Improvement of the Color Stability of Cyanidin-3-glucoside by Fatty Acid Enzymatic Acylation

Anthocyanins are water-soluble pigments with limited application in lipophilic matrices such as lipid-based foods and cosmetic formulations. In this work, the liposolubility improvement of cyanidin-3-glucoside (cy3glc) was performed by enzymatic esterification with saturated fatty acids with variable chain lengths, and their thermostabilities were evaluated at different pH values in a lipophilic medium (an aqueous sodium dodecyl sulfate solution) by means of UV-vis spectroscopy. Overall, lipophilic cy3glc derivatives showed improved color stability and lowered sensitivity to thermal degradation than nonmodified cy3glc in an SDS micellar solution between pH 3 and 7.