Polyphenolic Characterization and Anti-Inflammatory Effect of In Vitro Digested Extracts of Echinacea purpurea L. Plant Parts in an Inflammatory Model of Human Colon Cells.

Echinacea purpurea L. (EP) preparations are globally popular herbal supplements known for their medicinal benefits, including anti-inflammatory activities, partly related to their phenolic composition. However, regarding their use for the management of inflammation-related intestinal diseases, the knowledge about the fate of orally ingested constituents throughout the human gastrointestinal tract and the exposition of in vitro digested extracts in relevant inflammatory models are unknown. This study investigated for the first time the impact of in vitro gastrointestinal digestion (INFOGEST) on the phenolic composition and anti-inflammatory properties of EP extracts from flowers (EF), leaves (EL), and roots (ER) on IL-1ß-treated human colon-derived CCD-18Co cells. Among the seven hydroxycinnamic acids identified using HPLC-UV-MS/MS, chicoric and caftaric acids showed the highest concentrations in EL, followed by EF and ER, and all extracts exerted significant reductions in IL-6, IL-8, and PGE2 levels. After digestion, despite reducing the bioaccessibility of their phenolics, the anti-inflammatory effects were preserved for digested EL and, to a lesser extent, for EF, but not for digested ER. The lower phenolic content in digested EF and ER could explain these findings. Overall, this study emphasizes the potential of EP in alleviating intestinal inflammatory conditions and related disorders.

Sustainable biosynthetic pathways to value-added bioproducts from hydroxycinnamic acids.

The biorefinery concept, in which biomass is utilized for the production of fuels and chemicals, emerges as an eco-friendly, cost-effective, and renewable alternative to petrochemical-based production. The hydroxycinnamic acid fraction of lignocellulosic biomass represents an untapped source of aromatic molecules that can be converted to numerous high-value products with industrial applications, including in the flavor and fragrance sector and pharmaceuticals. This review describes several biochemical pathways useful in the development of a biorefinery concept based on the biocatalytic conversion of the hydroxycinnamic acids ferulic, caffeic, and p-coumaric acid into high-value molecules. KEY POINTS: • The phenylpropanoids bioconversion pathways in the context of biorefineries • Description of pathways from hydroxycinnamic acids to high-value compounds • Metabolic engineering and synthetic biology advance hydroxycinnamic acid-based biorefineries.

Investigation of Polyphenolic Compounds in Different Varieties of Black Chokeberry Aronia melanocarpa.

The purpose of this work was to study the qualitative and quantitative composition of the main groups of biologically active substances in the fresh fruits of five different varieties of black chokeberry (Aronia melanocarpa (Michx.) Elliot), carried out within the framework of the search for available and cost-effective raw materials for food product fortification. Samples of aronia chokeberry were grown at the Federal Scientific Center named after I.V. Michurin in the Tambov region of Russia. Using a modern chemical-analytical methodology, the contents and profiles of anthocyanin pigments, proanthocyanidins, flavonoids, hydroxycinnamic acids, organic acids (malic, quinic, succinic, and citric), monosaccharides, disaccharides, and sorbitol were determined in detail. Based on the results of the study, the most promising varieties were determined in terms of the content of the main biologically active substances.

Food Polyphenols and Type II Diabetes Mellitus: Pharmacology and Mechanisms.

Type II diabetes mellitus and its related complications are growing public health problems. Many natural products present in our diet, including polyphenols, can be used in treating and managing type II diabetes mellitus and different diseases, owing to their numerous biological properties. Anthocyanins, flavonols, stilbenes, curcuminoids, hesperidin, hesperetin, naringenin, and phenolic acids are common polyphenols found in blueberries, chokeberries, sea-buckthorn, mulberries, turmeric, citrus fruits, and cereals. These compounds exhibit antidiabetic effects through different pathways. Accordingly, this review presents an overview of the most recent developments in using food polyphenols for managing and treating type II diabetes mellitus, along with various mechanisms. In addition, the present work summarizes the literature about the anti-diabetic effect of food polyphenols and evaluates their potential as complementary or alternative medicines to treat type II diabetes mellitus. Results obtained from this survey show that anthocyanins, flavonols, stilbenes, curcuminoids, and phenolic acids can manage diabetes mellitus by protecting pancreatic ß-cells against glucose toxicity, promoting ß-cell proliferation, reducing ß-cell apoptosis, and inhibiting α-glucosidases or α-amylase. In addition, these phenolic compounds exhibit antioxidant anti-inflammatory activities, modulate carbohydrate and lipid metabolism, optimize oxidative stress, reduce insulin resistance, and stimulate the pancreas to secrete insulin. They also activate insulin signaling and inhibit digestive enzymes, regulate intestinal microbiota, improve adipose tissue metabolism, inhibit glucose absorption, and inhibit the formation of advanced glycation end products. However, insufficient data are available on the effective mechanisms necessary to manage diabetes.

A Combined NMR and UV-Vis Approach to Evaluate Radical Scavenging Activity of Rosmarinic Acid and Other Polyphenols.

Oxidative stress results from an imbalance between reactive oxygen species (ROS) production and the body's ability to neutralize them. ROS are reactive molecules generated during cellular metabolism and play a crucial role in normal physiological processes. However, excessive ROS production can lead to oxidative damage, contributing to various diseases and aging. This study is focused on rosmarinic acid (RA), a hydroxycinnamic acid (HCA) derivative well known for its antioxidant activity. In addition, RA has also demonstrated prooxidant behavior under specific conditions involving high concentrations of transition metal ions such as iron and copper, high pH, and the presence of oxygen. In this study, we aim to clarify the underlying mechanisms and factors governing the antioxidant and prooxidant activities of RA, and to compare them with other HCA derivatives. UV-Vis, NMR, and EPR techniques were used to explore copper(II)'s binding ability of RA, caffeic acid, and p-coumaric acid. At the same time, UV-Vis and NMR methods were exploited to evaluate the polyphenols' free radical scavenging abilities towards ROS generated by the ascorbic acid-copper(II) system. All the data indicate that RA is the most effective polyphenol both in copper binding abilities and ROS protection.

Almond [Prunus dulcis (Mill.) DA Webb] Processing Residual Hull as a New Source of Bioactive Compounds: Phytochemical Composition, Radical Scavenging and Antimicrobial Activities of Extracts from Italian Cultivars ('Tuono', 'Pizzuta', 'Romana').

In this study we developed a new extract, by the use of conventional solid-solvent extraction and a food-grade hydroalcoholic solvent, rich in phenolic and triterpenoid components from almon hull to be employed as functional ingredient in food, pharma and cosmetic sectors. Two autochthonous Sicilian cultivars ('Pizzuta' and 'Romana') and an Apulian modern cultivar ('Tuono') have been tested for the production of the extract. Results showed that the two Sicilian varieties, and in particular the 'Romana' one, present the best characteristics to obtain extracts rich in triterpenoids and hydroxycinnamic acids, useful for the production of nutraceutical supplements. About triterpenoids, the performance of the hydroalcoholic extraction process allowed to never go below 46% of recovery for 'Pizzuta' samples, with significantly higher percentages of recovery for 'Tuono' and 'Romana' extracts (62.61% and 73.13%, respectively) while hydroxycinnamic acids were recovered at higher recovery rate (84%, 89% and 88% for 'Pizzuta', 'Romana' and 'Tuono' extracts, respectively). Invitro antioxidant and antimicrobial activities exerted by the extracts showed promising results with P. aeruginosa being the most affected strain, inhibited up to the 1/8 dilution with 'Romana' extract. All the three tested extracts exerted an antimicrobial action up to 1/4 dilutions but 'Romana' and 'Pizzuta' extracts always showed the greatest efficacy.

Influence of Different Rootstocks on Fruit Quality and Primary and Secondary Metabolites Content of Blood Oranges Cultivars.

Blood oranges have high concentrations of bioactive compounds that are beneficial to health. In Europe, the cultivation of blood oranges is increasing due to their excellent nutritional properties. In Citrus crops, rootstocks play an important role in juice and can increase the content of bioactive compounds. The morphological, qualitative and nutritional parameters were analyzed in cultivars 'Tarocco Ippolito', 'Tarocco Lempso', 'Tarocco Tapi' and 'Tarocco Fondaconuovo' grafted onto Citrus macrophylla and Citrus reshni. 'Tarocco Lempso' grafted onto Citrus macrophylla obtained the highest values of weight (275.78 g), caliber (81.37 mm and 76.79 mm) and juice content (162.11 g). 'Tarocco Tapi' grafted onto Citrus reshni obtained the most interesting qualitative parameters (15.40 °Brix; 12.0 MI). 'Tarocco Lempso' grafted onto Citrus reshni obtained the most intense red juice (a* = 9.61). Overall, the highest concentrations of primary metabolites were in proline, aspartate, citric acid, and sucrose. The results showed that 'Tarocco Ippolito' juice grafted onto Citrus reshni had the highest levels of total hydroxycinnamic acids (263.33 mg L-1), total flavones (449.74 mg L-1) and total anthocyanins (650.42 mg L-1). To conclude, 'Tarocco Lempso' grafted onto Citrus macrophylla obtained the best values of agronomic parameters, and the cultivars grafted onto Citrus reshni obtained significantly higher concentrations in primary and secondary metabolites.

Suppression of a BAHD acyltransferase decreases p-coumaroyl on arabinoxylan and improves biomass digestibility in the model grass Setaria viridis.

Grass cell walls have hydroxycinnamic acids attached to arabinosyl residues of arabinoxylan (AX), and certain BAHD acyltransferases are involved in their addition. In this study, we characterized one of these BAHD genes in the cell wall of the model grass Setaria viridis. RNAi silenced lines of S. viridis (SvBAHD05) presented a decrease of up to 42% of ester-linked p-coumarate (pCA) and 50% of pCA-arabinofuranosyl, across three generations. Biomass from SvBAHD05 silenced plants exhibited up to 32% increase in biomass saccharification after acid pre-treatment, with no change in total lignin. Molecular dynamics simulations suggested that SvBAHD05 is a p-coumaroyl coenzyme A transferase (PAT) mainly involved in the addition of pCA to the arabinofuranosyl residues of AX in Setaria. Thus, our results provide evidence of p-coumaroylation of AX promoted by SvBAHD05 acyltransferase in the cell wall of the model grass S. viridis. Furthermore, SvBAHD05 is a promising biotechnological target to engineer crops for improved biomass digestibility for biofuels, biorefineries and animal feeding.

Feruloyl Esterases Protein Engineering to Enhance Their Performance as Biocatalysts: A Review.

Feruloyl esterases (FAEs) are versatile enzymes able to release hydroxycinnamic acids or synthesize their ester derivatives, both molecules with interesting biological activities such as: antioxidants, antifungals, antivirals, antifibrotic, anti-inflammatory, among others. The importance of these molecules in medicine, food or cosmetic industries provides FAEs with several biotechnological applications as key industrial biocatalysts. However, FAEs have some operational limitations that must be overcome, which can be addressed through different protein engineering approaches to enhance their thermal stability, catalytic efficiencies, and selectivity. This review aims to present a brief historical tour through the mutagenesis strategies employed to improve enzymes performance and analyze the current protein engineering strategies applied to FAEs as interesting biocatalysts. Finally, an outlook of the future of FAEs protein engineering approaches to achieve successful industrial biocatalysts is given.

Hydroxycinnamoyltransferase and CYP98 in phenolic metabolism in the rosmarinic acid-producing hornwort Anthoceros agrestis.

MAIN CONCLUSION: Anthoceros agrestis hydroxycinnamoyltransferase accepts shikimic and 3-hydroxyanthranilic acids while hydroxycinnamoylester/amide 3-hydroxylase (CYP98A147) preferred p-coumaroyl-(3-hydroxy)anthranilic acid compared to the shikimic acid derivative. Alternative pathways towards rosmarinic acid have to be considered. Rosmarinic acid (RA) is a well-known ester of caffeic acid and 3,4-dihydroxyphenyllactic acid. In the search for enzymes involved in RA biosynthesis in the hornwort Anthoceros agrestis, the hydroxycinnamoyltransferase sequence with the highest similarity to rosmarinic acid synthase from Lamiaceae has been amplified and heterologously expressed in Escherichia coli. In parallel, the single cytochrome P450 sequence belonging to the CYP98 group in Anthoceros agrestis was isolated and expressed in Saccharomyces cerevisiae which did not result in protein formation. Codon optimization and co-expression with NADPH:cytochrome P450 reductase (CPR) from Coleus blumei resulted in the formation of active enzymes. Both, the hydroxycinnamoyltransferase and CYP98 were characterized with respect to their temperature and pH optimum as well as their substrate acceptance. The hydroxycinnamoyltransferase (AaHCT6) readily accepted p-coumaroyl- and caffeoyl-CoA with a slightly higher affinity towards p-coumaroyl-CoA. The best acceptor substrate was shikimic acid (Km 25 µM with p-coumaroyl-CoA) followed by 3-hydroxyanthranilic acid (Km 153 µM with p-coumaroyl-CoA). Another accepted substrate was 2,3-dihydroxybenzoic acid. Anthranilic acid and 4-hydroxyphenyllactic acid (as precursor for RA) were not used as substrates. p-Coumaroylesters and -amides are substrates hydroxylated by CYP98 hydroxylases. The only CYP98 sequence from Anthoceros agrestis is CYP98A147. The best substrates for the NADPH-dependent hydroxylation were p-coumaroylanthranilic and p-coumaroyl-3-hydroxyanthranilic acids while p-coumaroylshikimic and p-coumaroyl-4-hydroxyphenyllactic acids were poor substrates. The biosynthetic pathway towards rosmarinic acid thus still remains open and other enzyme classes as well as an earlier introduction of the 3-hydroxyl group to afford the caffeic acid substitution pattern must be taken into consideration.

Chitosan-Hydroxycinnamic Acids Conjugates: Emerging Biomaterials with Rising Applications in Biomedicine.

Over the past thirty years, research has shown the huge potential of chitosan in biomedical applications such as drug delivery, tissue engineering and regeneration, cancer therapy, and antimicrobial treatments, among others. One of the major advantages of this interesting polysaccharide is its modifiability, which facilitates its use in tailor-made applications. In this way, the molecular structure of chitosan has been conjugated with multiple molecules to modify its mechanical, biological, or chemical properties. Here, we review the conjugation of chitosan with some bioactive molecules: hydroxycinnamic acids (HCAs); since these derivatives have been probed to enhance some of the biological effects of chitosan and to fine-tune its characteristics for its application in the biomedical field. First, the main characteristics of chitosan and HCAs are presented; then, the currently employed conjugation strategies between chitosan and HCAs are described; and, finally, the studied biomedical applications of these derivatives are discussed to present their limitations and advantages, which could lead to proximal therapeutic uses.

In Vitro Bioaccessibility and Antioxidant Activity of Phenolic Compounds in Coffee-Fortified Yogurt.

Yogurt is considered one of the most popular and healthy dairy products, and has been exploited as a delivery matrix for phenolic compounds. In this study, coffee powder was added to yogurt as a functional ingredient to produce coffee-fortified yogurt. Total phenolic compounds, antioxidant activity and individual hydroxycinnamic acids have been identified and quantified through mass spectrometry. The results from coffee-fortified yogurt were compared with fermented coffee and plain yogurt. Coffee-fortified yogurt had higher total phenolic content and antioxidant activity compared to plain yogurt. However, the total phenolic compounds found in coffee-fortified yogurt represented only 38.9% of the original content in coffee. Caffeoylquinic acids were the most abundant phenolic compounds in coffee. Fermented coffee and coffee-fortified yogurt displayed lower amounts of individual phenolic compounds with respect to coffee (69.8% and 52.4% of recovery, respectively). A protective effect of the yogurt matrix on total and individual coffee phenolic compounds has been observed after in vitro digestion, resulting in a higher bioaccessibility in comparison with digested fermented coffee. Moreover, coffee-fortified yogurt showed the highest antioxidant values after digestion. These findings clearly demonstrate that coffee-fortified yogurt can be considered a significant source of bioaccessible hydroxycinnamic acids, besides its health benefits as a fermented dairy product.

Characterization of Colorants Formed by Non-Enzymatic Browning Reactions of Hydroxycinnamic Acid Derivatives.

The browning of plant-based food is commonly understood to result from the enzymatic polymerization of phenolic compounds to pigments, called melanin. However, during the thermal treatment of food, enzymes are deactivated, and non-enzymatic reactions predominate. The extent of the contribution of phenolic compounds to these non-enzymatic reactions has been speculated ("melanin-like vs. melanoidin-like"), but the literature is limited. Therefore, the aim of the present study was to investigate the heat-induced reactions of caffeic acid (CA), para-coumaric acid (CS), ferulic acid (FA), hydrocaffeic acid (HC), and 5-O-caffeoylquinic acid (CGA) under dry conditions. The model systems were characterized by color formation, reactant conversion, and antioxidant properties. Reaction products were analyzed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. Decarboxylation could be classified as the driving force for the observed color formation and was significantly impacted by the substitution of the aromatic system. Reaction products were found to contribute to an increase in the antioxidant properties of the model systems. The oligomers described in this study could be incorporated into food melanoidins, contributing to the color and antioxidant properties observed in roasted food rich in phenolic compounds, such as coffee or cocoa.

Oil matrix modulates the bioaccessibility of polyphenols: a study of salad dressing formulation with industrial broccoli by-products and lemon juice.

BACKGROUND: The potential health-promoting effects of polyphenols depend considerably on their bioaccessibility, which is affected by the presence of other nutrients in the diet, including lipids. In this study, several salad dressing formulations were prepared using industrial broccoli by-product powder (BBP), lemon juice (LJ), and three different sources of oils (olive oil, hazelnut oil and sunflower oil) to both valorize polyphenol-rich industrial discards and also to investigate polyphenol bioaccessibility. The changes in the bioaccessibility of polyphenols from BBP and LJ were determined using the standardized in vitro digestion model. RESULTS: Four groups of polyphenols (hydroxycinnamic acids, flavonols, flavones, and flavonones) were detected in BBP and LJ. The bioaccessibility of hydroxycinnamic acids and flavonols from BBP increased significantly in the presence of LJ and oils (0.3- to 5.8-fold), whereas there was no significant difference between formulations containing different oil types. On the other hand, the bioaccessibility of phenolic acids from LJ did not change notably after co-ingestion with BBP and oils, whereas flavonoids, including vicenin-2 and hesperidin, were found to be significantly more bioaccessible when LJ was co-ingested with BBP and oils (0.8- to 1.4-fold) (P < 0.05). CONCLUSION: Overall, the current study highlighted that the bioaccessibility of polyphenols from BBP and LJ was modulated in the presence of an oil matrix. © 2022 Society of Chemical Industry.

Targeted phenolic profile of radler beers by HPLC-ESI-MS/MS: the added value of hesperidin to beer antioxidants.

The well-known health beneficial properties of beer are mainly due to phenolic antioxidants. Citrus-flavored beers represent a growing side-market in the beer industry, sparingly investigated to date. The phenolic profile of commercial radler beers (R1, R2) was investigated to evaluate the impact of the lemon juice added to beer in the industrial production. Results were compared to those obtained for opportunely chosen commercial beer (B) and lemonade (L). The study was carried out by an HPLC-MS/MS with an electrospray ionization source in selected ion recording mode, analyzing in a single chromatographic run 26 compounds belonging to the different phenolic classes of hydroxybenzoic, hydroxycinnamic and caffeoylquinic acids, flavonoids and prenylflavonoids. Different phenolic profiles were found for R1 and R2, mainly ascribed to different malt/hop/recipe used for the beer. High to very high level of hesperidin were found in the radlers, so that a major impact on phenolic antioxidants of the radlers was due to the lemon. Similarly, a major impact of the lemon aromas was found, D-limonene being the dominant peak resulting from the GC-MS analysis of the volatile fraction of the radlers.

Dysfunction of the 4-coumarate:coenzyme A ligase 4CL4 impacts aluminum resistance and lignin accumulation in rice.

The root cell wall is the first and primary target of aluminum (Al) toxicity. Monocots such as rice (Oryza sativa) can accumulate appreciable levels of hydroxycinnamic acids (HCAs) to modify and cross-link hemicellulose and/or lignin of the cell wall. Nevertheless, it is unclear whether this HCA-mediated modification of the cell wall is important for Al accumulation and resistance. We previously isolated and characterized a rice ral1 (resistance to aluminum 1) mutant that shows enhanced Al resistance. In this study, we cloned RAL1 and found that it encodes the 4-coumarate:coenzyme A ligase 4CL4, an enzyme putatively involved in lignin biosynthesis. Mutation of RAL1/4CL4 reduces lignin content and increases the accumulation of its substrates 4-coumaric acid (PA) and ferulic acid (FA). We demonstrate that altered lignin accumulation is not required for the enhanced Al resistance in ral1/4cl4 mutants. We found that the increased accumulation of PA and FA can reduce Al binding to hemicellulose and consequently enhance Al resistance in ral1/4cl4 mutants. Al stress is able to trigger PA and FA accumulation, which is likely caused by the repression of the expression of RAL1/4CL4 and its homologous genes. Our results thus reveal that Al-induced PA and FA accumulation is actively and positively involved in Al resistance in rice through the modification of the cell wall and thereby the reduced Al binding to the cell wall.

Catabolism of hydroxycinnamic acids in contact with probiotic Lactobacillus.

AIMS: The catabolism products of the fermentation process of selected hydroxycinnamic acids initiated by different species of Lactobacillus strains were identified. METHODS AND RESULTS: Three dietary supplements (Sanprobi IBS® , BioGaia ProTectis Baby® and Dicoflor 60® ) were used to isolate the Lactobacillus strains. The overnight bacterial cultures (18 h) were diluted and grown in a microaerophilic atmosphere at 37°C. Then, each phenolic acid was added to bacterial cultures and incubated for 24 h at 37°C. Samples were collected at specific intervals for a further 24 h of incubation. LC-MS/MS was used for the identification of metabolism products of selected phenolic acids. CONCLUSIONS: The phenolic acids were resistant to the Lactobacillus rhamnosus GG. Lactobacillus plantarum 299v caused degradation of caffeic and ferulic acids. The former was degraded either to dihydrocaffeic acid or to 4-vinylcatechol and 4-ethylcatechol. Ferulic acid was degraded only to dihydroferulic acid. Lactobacillus reuteri DSM 17938 caused only the degradation of chlorogenic acid (5-caffeoylquinic acid, referred to IUPAC nomenclature) to caffeic acid. SIGNIFICANCE AND IMPACT OF THE STUDY: Using of Lactobacilli as food additive should be taken into account that phenolic acids metabolism rate depends on not only the specific bacterial strain but also the structural properties of the acid.

Approaches for the enzymatic synthesis of alkyl hydroxycinnamates and applications thereof.

Alkyl hydroxycinnamates (AHs) is a group of molecules of biotechnological interest due to their cosmetic, food, and pharmaceutical applications. Among their most interesting uses are as UV protectants, skin depigmentation agents, and antioxidant ingredients which are often claimed for their antitumoral potential. Nowadays, many sustainable enzymatic approaches using low-cost starting materials are available and interesting immobilization techniques are helping to increase the reuse of the biocatalysts, allowing the intensification of the processes and increasing AHs accessibility. Here a convenient summary of AHs most interesting biological activities and possible applications is presented. A deeper analysis of the art state to obtain AHs, focusing on most employed enzymatic synthesis approaches, their sustainability, acyl donors relevance, and most interesting enzyme immobilization strategies is provided.Key points• Most interesting alkyl hydroxycinnamates applications are summarized.• Enzymatic approaches to obtain alkyl hydroxycinnamates are critically discussed.• Outlook of enzyme immobilization strategies to attain alkyl hydroxycinnamates.

Aspergillus niger uses the peroxisomal CoA-dependent ß-oxidative genes to degrade the hydroxycinnamic acids caffeic acid, ferulic acid, and p-coumaric acid.

Aromatic compounds are important molecules which are widely applied in many industries and are mainly produced from nonrenewable sources. Renewable sources such as plant biomass are interesting alternatives for the production of aromatic compounds. Ferulic acid and p-coumaric acid, a precursor for vanillin and p-vinyl phenol, respectively, can be released from plant biomass by the fungus Aspergillus niger. The degradation of hydroxycinnamic acids such as caffeic acid, ferulic acid, and p-coumaric acid has been observed in many fungi. In A. niger, multiple metabolic pathways were suggested for the degradation of hydroxycinnamic acids. However, no genes were identified for these hydroxycinnamic acid metabolic pathways. In this study, several pathway genes were identified using whole-genome transcriptomic data of A. niger grown on different hydroxycinnamic acids. The genes are involved in the CoA-dependent ß-oxidative pathway in fungi. This pathway is well known for the degradation of fatty acids, but not for hydroxycinnamic acids. However, in plants, it has been shown that hydroxycinnamic acids are degraded through this pathway. We identified genes encoding hydroxycinnamate-CoA synthase (hcsA), multifunctional ß-oxidation hydratase/dehydrogenase (foxA), 3-ketoacyl CoA thiolase (katA), and four thioesterases (theA-D) of A. niger, which were highly induced by all three tested hydroxycinnamic acids. Deletion mutants revealed that these genes were indeed involved in the degradation of several hydroxycinnamic acids. In addition, foxA and theB are also involved in the degradation of fatty acids. HcsA, FoxA, and KatA contained a peroxisomal targeting signal and are therefore predicted to be localized in peroxisomes. KEY POINTS: • Metabolism of hydroxycinnamic acid was investigated in Aspergillus niger • Using transcriptome data, multiple CoA-dependent ß-oxidative genes were identified. • Both foxA and theB are involved in hydroxycinnamate but also fatty acid metabolism.

Laccase and Tyrosinase Biosensors Used in the Determination of Hydroxycinnamic Acids.

In recent years, researchers have focused on developing simple and efficient methods based on electrochemical biosensors to determine hydroxycinnamic acids from various real samples (wine, beer, propolis, tea, and coffee). Enzymatic biosensors represent a promising, low-cost technology for the direct monitoring of these biologically important compounds, which implies a fast response and simple sample processing procedures. The present review aims at highlighting the structural features of this class of compounds and the importance of hydroxycinnamic acids for the human body, as well as presenting a series of enzymatic biosensors commonly used to quantify these phenolic compounds. Enzyme immobilization techniques on support electrodes are very important for their stability and for obtaining adequate results. The following sections of this review will briefly describe some of the laccase (Lac) and tyrosinase (Tyr) biosensors used for determining the main hydroxycinnamic acids of interest in the food or cosmetics industry. Considering relevant studies in the field, the fact has been noticed that there is a greater number of studies on laccase-based biosensors as compared to those based on tyrosinase for the detection of hydroxycinnamic acids. Significant progress has been made in relation to using the synergy of nanomaterials and nanocomposites for more stable and efficient enzyme immobilization. These nanomaterials are mainly carbon- and/or polymer-based nanostructures and metallic nanoparticles which provide a suitable environment for maintaining the biocatalytic activity of the enzyme and for increasing the rate of electron transport.