A series of cinnamic acid derivatives and their inhibitory activity on intestinal α-glucosidase

Inhibition of α-glucosidase and α-amylase delays the digestion of starch and disaccharides to absorbable monosaccharides, resulting in a reduction of postprandial hyperglycemia. Finding effective mammalian α-glucosidase inhibitors from natural sources can be beneficial in the prevention and treatment of diabetes mellitus. We investigated the inhibitory activity of cinnamic acid derivatives against rat intestinal α-glucosidase and porcine pancreatic α-amylase in vitro. Among 11 cinnamic acid derivatives, caffeic acid, ferulic acid, and isoferulic acid were the most potent inhibitors against intestinal maltase with IC₅₀ values of 0.74?±?0.01, 0.79?±?0.04, and 0.76?±?0.03?mM, respectively, whereas ferulic acid (IC₅₀?=?0.45?±?0.01?mM) and isoferulic acid (IC₅₀?=?0.45?±?0.01?mM) were effective intestinal sucrase inhibitors. However, all cinnamic acid derivatives were found to be inactive in pancreatic α-amylase inhibition. Kinetic analysis revealed that intestinal maltase was inhibited by caffeic acid, ferulic acid, and isoferulic acid in a mixed-inhibition manner. In addition, ferulic acid and isoferulic acid inhibited intestinal sucrase in a mixed type manner, whereas caffeic acid was a non-competitive inhibitor. The combination of isoferulic acid and acarbose showed an additive inhibition on intestinal sucrase. This study could provide a new insight into naturally occurring intestinal α-glucosidase inhibitors that could be useful for treatment of diabetes and its complications.     

Search for novel histone deacetylase inhibitors. Part II: Design and synthesis of novel isoferulic acid derivatives

Previously, we described the discovery of potent ferulic acid-based histone deacetylase inhibitors (HDACIs) with halogeno-acetanilide as novel surface recognition moiety (SRM). In order to improve the affinity and activity of these HDACIs, twenty seven isoferulic acid derivatives were described herein. The majority of title compounds displayed potent HDAC inhibitory activity. In particular, IF5 and IF6 exhibited significant enzymatic inhibitory activities, with IC₅₀ values of 0.73 ± 0.08 and 0.57 ± 0.16 μM, respectively. Furthermore, these compounds showed moderate antiproliferative activity against human cancer cells. Especially, IF6 displayed promising profile as an antitumor candidate with IC₅₀ value of 3.91 ± 0.97 μM against HeLa cells. The results indicated that these isoferulic acid derivatives could serve as promising lead compounds for further optimization.     

Enhanced Lignin Monomer Production Caused by Cinnamic Acid and Its Hydroxylated Derivatives Inhibits Soybean Root Growth

Cinnamic acid and its hydroxylated derivatives (p-coumaric, caffeic, ferulic and sinapic acids) are known allelochemicals that affect the seed germination and root growth of many plant species. Recent studies have indicated that the reduction of root growth by these allelochemicals is associated with premature cell wall lignification. We hypothesized that an influx of these compounds into the phenylpropanoid pathway increases the lignin monomer content and reduces the root growth. To confirm this hypothesis, we evaluated the effects of cinnamic, p-coumaric, caffeic, ferulic and sinapic acids on soybean root growth, lignin and the composition of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) monomers. To this end, three-day-old seedlings were cultivated in nutrient solution with or without allelochemical (or selective enzymatic inhibitors of the phenylpropanoid pathway) in a growth chamber for 24 h. In general, the results showed that 1) cinnamic, p-coumaric, caffeic and ferulic acids reduced root growth and increased lignin content; 2) cinnamic and p-coumaric acids increased p-hydroxyphenyl (H) monomer content, whereas p-coumaric, caffeic and ferulic acids increased guaiacyl (G) content, and sinapic acid increased sinapyl (S) content; 3) when applied in conjunction with piperonylic acid (PIP, an inhibitor of the cinnamate 4-hydroxylase, C4H), cinnamic acid reduced H, G and S contents; and 4) when applied in conjunction with 3,4-(methylenedioxy)cinnamic acid (MDCA, an inhibitor of the 4-coumarate:CoA ligase, 4CL), p-coumaric acid reduced H, G and S contents, whereas caffeic, ferulic and sinapic acids reduced G and S contents. These results confirm our hypothesis that exogenously applied allelochemicals are channeled into the phenylpropanoid pathway causing excessive production of lignin and its main monomers. By consequence, an enhanced stiffening of the cell wall restricts soybean root growth.     

Interaction of hydroxycinnamic acid derivatives with the Cl3COO radical: a pulse radiolysis study

The electron transfer reactions between the trichloromethylperoxyl radical (Cl₃COO^·) and hydroxycinnamic acid derivatives, including chlorogenic acid, sinapic acid, caffeic acid, ferulic acid and 3,4-(methylenedioxy)cinnamic acid, have been studied by pulse radiolysis. The hydroxycinnamic acid derivatives, especially sinapic acid, are identified as good antioxidants for reduction of Cl₃COO^· via electron transfer reactions. From buildup kinetic analysis of phenoxyl radical, the rate constant for reaction of Cl₃COO^· with sinapic acid has been determined to be 8.2 × 10⁷ dm³ mol^-1 s^-1, while the rate constants of electron transfer from other hydroxycinnamic acid derivatives to Cl₃COO^· were obtained to be about 2 × 10⁷dm³ mol^-1 s^-1. The reaction of 3,4-(methylenedioxy)cinnamic acid with Cl₃COO^· was investigated as an evidence for the electron transfer mechanism.     

Lipase catalyzed reaction of L-ascorbic acid with cinnamic acid esters and substituted cinnamic acids

To perform the lipase-catalyzed synthesis of L-ascorbic acid derivatives from plant-based compounds such as cinnamic and ferulic acid under mild reaction conditions, the activities of immobilized Candida ntarctica lipase with different cinnamic acid esters and substituted cinnamic acids were compared. As a result, immobilized C. ntarctica lipase was found to prefer vinyl cinnamic acid to other esters such as allyl-, ethyl-, and isobutyl cinnamic acids as well as substituted cinnamic acids such as p-coumaric acid, caffeic acid, ferulic acid, and sinapic acid. Based on these results, large-scale synthesis of 6-O-cinnamyl-L-ascorbic acid ester was performed using immobilized C. ntarctica lipase in dry organic solvent, resulting in 68% yield (493 mg) as confirmed by ¹³C-NMR.     

N-Caffeoyl serotonin as selective COX-2 inhibitor

The inhibitory effects of the synthetic serotonin analogues (1-8) on COX (1 and 2) were evaluated. Two serotonin derivatives (4 and 8) showed inhibitory effect of COX (1 and 2). Especially, 4 exhibited excellent inhibitions on COX-2 with extremely high potency (IC(50)=42.5 μM). The inhibitory activities of cinnamic acid derivatives and serotonin were evaluated to clarify whether inhibitory activities of compound 4 and 8 are due to cinnamic acid moiety or serotonin moiety. Caffeic acid and N-caffeoyl serotonin (4) exhibited selective inhibition of COX-2 compared to aspirin. Comparison caffeic acid with 4 suggested that the linkage of caffeic acid and serotonin enhance COX-2 inhibition. Comparison of structures of caffeic acid and sinapic acid implied that catechol moiety of cinnamic acid derivatives is a major contributing factor for selective inhibition of COX-2. The selective COX-2 inhibitory activity of compound 4 is significant and could be employed as drugs against inflammatory and allergy.     

Bioconversion of cinnamic acid derivatives by Schizophyllum commune

To investigate the production of useful phenols from plant resources, we examined the metabolism of cinnamic acid derivatives by a wood-rotting fungus, Schizophyllum commune. Four cinnamic acid derivatives (cinnamic, p-coumaric, ferulic, and sinapic acids) were tested as substrates. Two main reactions, reduction and cleavage of the side chain, were observed. Reduction of the side chain was confirmed in cinnamic acid and p-coumaric acid metabolism. The side chain cleavage occurred in p-coumaric acid and ferulic acid metabolism but the initial reactions of these acids differed. Sinapic acid was not metabolized by S. commune. p-Hydroxybenzaldehyde accumulation was observed in the culture to which p-coumaric acid was added. This suggests that S. commune is a useful agent for transforming p-coumaric acid into p-hydroxybenzaldehyde.     

Enhanced fluorescence of tetrasulfonated zinc phthalocyanine by graphene quantum dots and its application in molecular sensing/imaging

When excited at 435 nm, tetra‐sulfonate zinc phthalocyanine (ZnPcS₄) emitted dual fluorescence at 495 and 702 nm. The abnormal fluorescence at 495 nm was experimentally studied and analyzed in detail for the first time. The abnormal fluorescence at 495 nm was deduced to originate from triplet–triplet (T–T) energy transfer of excited phthalocyanine (³*ZnPcS₄). Furthermore, graphene quantum dots (GQDs) enhanced the 495 nm fluorescence quantum yield (Q) of ZnPcS₄. The fluorescence properties of ZnPcS₄–GQDs conjugate were retained in a cellular environment. Based on the fluorescence of ZnPcS₄–GQDs conjugate, we designed and prepared an Apt29/thrombin/Apt15 sandwich thrombin sensor with high specificity and affinity. This cost‐saving, simple operational sensing strategy can be extended to use in sensing/imaging of other biomolecules.     

Novel polycondensed biopolyamide generated from biomass-derived 4-aminohydrocinnamic acid

Biomass plastics are expected to contribute to the establishment of a carbon-neutral society by replacing conventional plastics derived from petroleum. The biomass-derived aromatic amine 4-aminocinnamic acid (4ACA) produced by recombinant bacteria is applied to the synthesis of high-performance biopolymers such as polyamides and polyimides. Here, we developed a microbial catalyst that hydrogenates the α,β-unsaturated carboxylic acid of 4ACA to generate 4-aminohydrocinnamic acid (4AHCA). The ability of 10 microbial genes for enoate and xenobiotic reductases expressed in Escherichia coli to convert 4ACA to 4AHCA was assessed. A strain producing 2-enoate reductase from Clostridium acetobutylicum (ca2ENR) reduced 4ACA to 4AHCA with a yield of > 95% mol mol⁻¹ and reaction rates of 3.4 ± 0.4 and 4.4 ± 0.6 mM h⁻¹ OD₆₀₀ ⁻¹ at the optimum pH of 7.0 under aerobic and anaerobic conditions, respectively. This recombinant strain reduced caffeic, cinnamic, coumaric, and 4-nitrocinnamic acids to their corresponding propanoic acid derivatives. We polycondensed 4AHCA generated from biomass-derived 4ACA by dehydration under a catalyst to form high-molecular-weight poly(4AHCA) with a molecular weight of M _n = 1.94 MDa. This polyamide had high thermal properties as indicated by a 10% reduction in weight at a temperature of T _d10 = 394 °C and a glass transition temperature of T _g = 240 °C. Poly(4AHCA) derived from biomass is stable at high temperatures and could be applicable to the production of high-performance engineering plastics.

     

Ultrasensitive chemiluminescence assay for cimetidine detection based on the synergistic improving effect of Au nanoclusters and graphene quantum dots

A novel and sensitive chemiluminescence (CL) procedure based on the synergetic catalytic effects of gold nanoclusters (Au NCs) and graphene quantum dots (GQDs) was developed for the reliable measurement of cimetidine (CM). The initial experiments showed that the KMnO₄‐based oxidation of alkaline rhodamine B (RhoB) generated a very weak CL emission, which was intensively enhanced in the simultaneous presence of Au NCs and GQDs. CL intermediates can be adsorbed and gathered on the surface of Au NCs, becoming more stable. GQDs participate in the energy transferring processes and facilitate them. These improving effects were simultaneously obtained by adding both Au NCs and GQDs into the RhoB‐KMnO₄ reaction. Consequently, the increasing effect of the Au NCs/GQDs mixture was more than that of pure Au NCs or GQDs, and a new nano‐assisted powerful CL system was achieved. Furthermore, a marked quenching in the emission of the introduced CL system was observed in the presence of CM, so the system was examined to design a sensitive sensor for CM. After optimization of influencing parameters, the linear lessening in CL emission intensity of KMnO₄‐RhoB‐Au NCs/GQDs was verified for CM concentrations in the range 0.8–200 ng ml^?1. The limit of detection (3S_b/m) was 0.3 ng ml^?1. Despite being a simple CL method, good sensitivity was obtained for CM detection with reliable results for CM determination in human urine samples.     

Cinnamic acid production using <Emphasis Type="Italic">Streptomyces lividans</Emphasis> expressing phenylalanine ammonia lyase

Cinnamic acid production was demonstrated using Streptomyces as a host. A gene encoding phenylalanine ammonia lyase (PAL) from Streptomyces maritimus was introduced into Streptomyces lividans, and its expression was confirmed by Western blot analysis. After 4 days cultivation using glucose as carbon source, the maximal level of cinnamic acid reached 210 mg/L. When glycerol (30 g/L) was used as carbon source, the maximal level of produced cinnamic acid reached 450 mg/L. In addition, using raw starch, xylose or xylan as carbon source, the maximal level of cinnamic acid reached 460, 300, and 130 mg/L, respectively. We demonstrated that S. lividans has great potential to produce cinnamic acid as well as other aromatic compounds.     

Activity of caffeic acid derivatives against Candida albicans biofilm

The aim of this study was to evaluate the caffeic acid (1) and ester derivatives (2–10) against Candida albicans biofilm and to investigate whether these compounds are able to inhibit the biofilm formation or destroy pre-formed biofilm.Caffeic acid ester 7, cinnamic acid ester 8 and 3,4-dihydroxybenzoic acid ester 10 are more active than fluconazole, used as reference drug, both on biofilm in formation with MIC₅₀ values of 32, 32 and 16 μg/mL, respectively, and in the early stage of biofilm formation (4 h) with MIC₅₀ values of 64, 32 and 64 μg/mL, respectively. These esters result also more active than fluconazole on mature biofilm (24 h), especially 8 and 10 with MIC₅₀ values of 64 μg/mL.     

Synthesis of non-prenyl analogues of baccharin as selective and potent inhibitors for aldo-keto reductase 1C3

Inhibitors of a human member (AKR1C3) of the aldo-keto reductase superfamily are regarded as promising therapeutics for the treatment of prostatic and breast cancers. Baccharin [3-prenyl-4-(dihydrocinnamoyloxy)cinnamic acid], a component of propolis, was shown to be both potent (K_i 56 nM) and highly isoform-selective inhibitor of AKR1C3. In this study, a series of derivatives of baccharin were synthesized by replacing the 3-prenyl moiety with aryl and alkyl ether moieties, and their inhibitory activities for the enzyme were evaluated. Among them, two benzyl ether derivatives, 6m and 6n, showed an equivalent inhibitory potency to baccharin. The molecular docking of 6m in AKR1C3 has allowed the design and synthesis of (E)-3-{3-[(3-hydroxybenzyl)oxy]-4-[(3-phenylpropanoyl)oxy]phenyl}acrylic acid (14) with improved potency (K_i 6.4 nM) and selectivity comparable to baccharin. Additionally, 14 significantly decreased the cellular metabolism of androsterone and cytotoxic 4-oxo-2-nonenal by AKR1C3 at much lower concentrations than baccharin.     

O-Methyletransferases endoplasmiques de Populus nigra

O-Methyltransferases catalysing the methylation of caffeic acid to ferulic acid, isoferulic acid and dimethylcaffeic acid were extracted from the endoplasmic reticulum of Populus glandular tissue. The significance of methoxylated cinnamic acids in secreted flavonoid biosynthesis is discussed.     

Oxidation of hydroxycinnamic acid and hydroxycinnamyl alcohol derivatives by laccase and peroxidase. Interactions among p-hydroxyphenyl,guaiacyl and syringyl groups during the oxidation reactions

Fungal laccase oxidized derivatives of hydroxycinnamic acid. The rates decreased in the order sinapic acid > ferulic acid ≥p-coumaric acid. The laccase oxidized sinapyl alcohol faster than coniferyl alcohol. The rates of oxidation of the hydroxycinnamic acid derivatives by an isoenzyme of peroxidase from horseradish decreased in the order p-coumaric acid > ferulic acid ≥ sinapic acid. The peroxidase oxidized coniferyl alcohol much faster than sinapyl alcohol. The laccase and the peroxidase predominantly oxidized (a) ferulic acid in a reaction mixture that contained p-coumaric acid and ferulic acid, (b) sinapic acid in a mixture of p-coumaric acid plus sinapic acid, and (c) sinapic acid in a mixture of ferulic acid plus sinapic acid. In a reaction mixture that contained both coniferyl and sinapyl alcohols, both fungal laccase and horseradish peroxidase predominantly oxidized sinapyl alcohol. From these results, it is concluded (1) that the p-hydroxyphenyl radical can oxidize guaiacyl and syringyl groups and produce their radicals and (2) that the guaiacyl radical can oxidize the syringyl group under formation of its radical; and that (3) in both cases the reverse reactions are very slow.     

Solid‐phase synthesis of graphene quantum dots from the food additive citric acid under microwave irradiation and their use in live‐cell imaging

The work demonstrated that solid citric acid, one of the most common food additives, can be converted to graphene quantum dots (GQDs) under microwave heating. The as‐prepared GQDs were further characterized by various analytical techniques like transmission electron microscopy, atomic force microscopy, X‐ray diffraction, X–ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, fluorescence and UV‐visible spectroscopy. Cytotoxicity of the GQDs was evaluated using HeLa cells. The result showed that the GQDs almost did not exhibit cytotoxicity at concentrations as high as 1000 µg mL^–1. In addition, it was found that the GQDs showed good solubility, excellent photostability, and excitation‐dependent multicolor photoluminescence. Subsequently, the multicolor GQDs were successfully used as a fluorescence light‐up probe for live‐cell imaging. Copyright © 2015 John Wiley & Sons, Ltd.     

Chiral separation and discrimination of catechin by sinorhizobial octasaccharides in capillary electrophoresis and C NMR spectroscopy

Succinoglycan, a sinorhizobial exopolysaccharide produced by Sinorhizobium meliloti, is composed of an octasaccharide subunit. S. meliloti produces both high-molecular-weight and low-molecular-weight (M_r < 10,000) succinoglycans which consist of monomers, dimers, or trimers. Succinoglycan monomers were isolated and further purified in the monomer series (M1, M2, and M3) by the degree of succinylation. We used sinorhizobial octasaccharides (M1, M2, and M3) as chiral additives in capillary electrophoresis (CE) for chiral separation of catechin and also as chiral shift reagents with ¹³C NMR spectroscopy for chiral discrimination of catechin. Chiral separation of catechin took place when sinorhizobial octasaccharides (M2 and M3) were added to the background electrolyte (BGE) in CE. NMR signal splittings were also observed in the interactions of sinorhizobial octasaccharides with the enantiomers of catechin. Both chiral separation and discrimination of catechin depend on the presence of succinate substituents of the linear monomeric octasaccharide in CE and NMR spectroscopy, suggesting that succinylation of sinorhizobial octasaccharide is decisive for the effective chiral separation and discrimination of catechin.     

Potent Inhibitory Effects of Some Phenolic Acids on Lactoperoxidase

Lactoperoxidase (LPO) plays a key role in immune response against pathogens. In this study, we examined the effects of some phenolic acids on LPO. For this purpose, bovine milk LPO was purified 380.85‐fold with a specific activity of 26.66 EU/mg and overall yield of 73.33% by using Amberlite CG‐50 H⁺ resin and CNBr‐activated Sepharose‐4B‐l ‐tyrosine‐sulfanilamide affinity chromatography. After purification, the in vitro effects of phenolic acids (tannic acid, 3,4‐dihydroxybenzoic acid, 3,5‐ dihydroxybenzoic acid, chlorogenic acid, sinapic acid, 4‐hydroxybenzoic acid, vanillic acid, salicylic acid, and 3‐hydroxybenzoic acid) were investigated on LPO. These phenolic acids showed potent inhibitory effect on LPO. K_i values for these phenolic acids were found as 0.0129 nM, 0.132 μM, 0.225 μM, 0.286 μM, 0.333 μM, 2.33 μM, 10.82 μM, 0.076 mM, and 0.405 mM, respectively. Sinapic acid and 4‐hydroxybenzoic acid exhibited noncompetitive inhibition; 3,4‐dihydroxybenzoic acid showed uncompetitive inhibition, and other phenolic acids showed competitive inhibition.     

Effects of Ascorbate on the Oxidation of Derivatives of Hydroxycinnamic Acid and the Mechanism of Oxidation of Sinapic Acid by Cell Wall-Bound Peroxidases

A cell wall fraction isolated from epicotyls of Vigna angularis,which contained both ionically and covalently bound peroxidases,rapidly oxidized p-coumaric, caffeic and ferulic acids and slowlyoxidized sinapic acid. The oxidation of sinapic acid was greatlyenhanced in the presence of p-coumaric, caffeic or ferulic acid.Ascorbate (20 µM) inhibited the oxidation of ferulic acidby about 70% and completely inhibited the oxidation of p-coumaricand ferulic acids. The cell wall fraction was capable of bindingferulic and sinapic acids but not caffeic acid. p-Coumaric acidbound only slightly to cell walls. The oxidation of p-coumaricand ferulic acids by KCl-washed cell walls was inhibited byabout 60% and 10%, respectively, by 20 µM ascorbate, butthe oxidation of caffeic acid was completely inhibited by ascorbateat less than 20 µM. The oxidation of derivatives of hydroxycinnamicacid by peroxidases released from cell walls by washing with1 M KCl was completely inhibited by ascorbate. These resultssuggest that the inhibition by ascorbate depends on the substituentgroup of the phenyl ring of the derivatives of hydroxycinnamicacid when the oxidation reaction is catalyzed by cell wall-boundperoxidases and that the oxidation of sinapic acid is mediatedby phenoxyl radicals of derivatives of hydroxycinnamic acidother than sinapic acid. (Received December 2, 1993; Accepted March 3, 1994)     

Cloning and characterization of a new laccase from Bacillus licheniformis catalyzing dimerization of phenolic acids

A new laccase gene (cotA) was cloned from Bacillus licheniformis and expressed in Escherichia coli. The recombinant protein CotA was purified and showed spectroscopic properties, typical for blue multi-copper oxidases. The enzyme has a molecular weight of ~65 kDa and demonstrates activity towards canonical laccase substrates 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), syringaldazine (SGZ) and 2,6-dimethoxyphenol (2,6-DMP). Kinetic constants K _M and k _cat for ABTS were of 6.5 ± 0.2 μM and 83 s⁻¹, for SGZ of 4.3 ± 0.2 μM and 100 s⁻¹, and for 2,6-DMP of 56.7 ± 1.0 μM and 28 s⁻¹. Highest oxidizing activity towards ABTS was obtained at 85°C. However, after 1 h incubation of CotA at 70°C and 80°C, a residual activity of 43% and 8%, respectively, was measured. Furthermore, oxidation of several phenolic acids and one non-phenolic acid by CotA was investigated. CotA failed to oxidize coumaric acid, cinnamic acid, and vanillic acid, while syringic acid was oxidized to 2,6-dimethoxy-1,4-benzoquinone. Additionally, dimerization of sinapic acid, caffeic acid, and ferulic acid by CotA was observed, and highest activity of CotA was found towards sinapic acid.