Protocatechuic Acid Ethyl Ester Research Articles

Comprehensive quality analyses of important apricot varieties produced in Türkiye

Türkiye, its geographical location, and climatic conditions make it suitable for hosting various fruit species. Among these species, the apricot holds worldwide fame. In this study, local varieties including Hacıhaliloğlu, Kabaaşı, Hasanbey, and Şalak were used, as well as foreign varieties commonly grown in coastal regions, namely Mogador and Mikado. Local varieties are significantly distinguished from foreign varieties by their high soluble solids and low acid content. The low taste values in foreign varieties are primarily attributed to their genotypic structure, as well as the fact that full ripening is not expected due to obtained high price early harvest period under Mediterranean climate conditions. The main sugars were sucrose and sorbitol among varieties, while citric acid was found the highest in all varieties except for the Hasanbey variety grown in Malatya. The Şalak variety attracts attention with its high amounts of catechin, neochlorogenic acid, gallic acid, and PAEE (protocatechuic acid ethyl ester) contents. Foreign-origin cultivars are generally found to be superior in terms of carotenoid compounds. The content of β-carotene ranges from 61.2% to 80.9% among apricot varieties. The results of the study have clearly shown that the genotype is a fundamental determinant in terms of the examined quality parameters.

The Array of Antibacterial Action of Protocatechuic Acid Ethyl Ester and Erythromycin on Staphylococcal Strains.

The spread of antibiotic resistance among bacteria has become one of the major health problems worldwide. Methicillin-resistant staphylococcal strains are especially dangerous because they are often resistant to other antibiotics. The increasing insensitivity to macrolides, lincosamides and streptogramin B antibiotics of methicillin-resistant staphylococcal isolates has limited the use of these drugs in therapy. The combination of natural compounds and antibiotics can be considered as an alternative tool to fight multi-drug-resistant pathogen infections. The aim of the presented study was to examine the antibacterial activity of protocatechuic acid ethyl ester–erythromycin combination towards Staphylococcus aureus and Staphylococcus epidermidis strains with various resistance profiles to methicillin and macrolides, lincosamides and streptogramin B (MLSB) antibiotics. The in-vitro antibacterial potential of the above combination was investigated by minimum inhibitory concentration assays and checkerboard testing. The observed effects were strain dependent, with 8 of 12 tested staphylococcal strains showing an indifferent effect on the natural compound and erythromycin; for 2 strains, the tested combination had an additive effect, while for another 2, the effect was synergistic. Interestingly, the multi-drug-resistant strains were more sensitive to the cooperative action of the protocatechuic acid ethyl ester and the antibiotic.

Effect of Protocatechuic Acid Ethyl Ester on Biomembrane Models: Multilamellar Vesicles and Monolayers.

The interactions of drugs with cell membranes are of primary importance for several processes involved in drugs activity. However, these interactions are very difficult to study due to the complexity of biological membranes. Lipid model membranes have been developed and used to gain insight into drug–membrane interactions. In this study, the interaction of protocatechuic acid ethyl ester, showing radical-scavenging activity, antimicrobial, antitumor and anti-inflammatory effects, with model membranes constituted by multilamellar vesicles and monolayers made of DMPC and DSPC, has been studied. Differential scanning calorimetry and Langmuir–Blodgett techniques have been used. Protocatechuic acid ethyl ester interacted both with MLV and monolayers. However, a stronger interaction of the drug with DMPC-based model membranes has been obtained. The finding of this study could help to understand the protocatechuic acid ethyl ester action mechanism.

The Hypoxia Mimetic Protocatechuic Acid Ethyl Ester Inhibits Synaptic Signaling and Plasticity in the Rat Hippocampus

During hypoxia a number of physiological changes occur within neurons including the stabilization of hypoxia-inducible factors (HIFs). The activity of these proteins is regulated by O2, Fe2+, 2-OG and ascorbate-dependant hydroxylases which contain prolyl-4-hydroxylase domains (PHDs). PHD inhibitors have been widely used and have been shown to have a preconditioning and protective effect against a later and more severe hypoxic insult. In this study we have investigated the neuroprotective effects of the PHD inhibitor, protocatechuic acid ethyl ester (ethyl 3,4, dihydroxybenzoate: EDHB), as well as its effects on synaptic transmission and plasticity in the rat hippocampus using electrophysiological techniques. We report for the first time, an acute concentration-dependent and reversible inhibitory effect of EDHB (10–100 μM) on synaptic transmission in the dentate gyrus but not Cornu Ammonis 1 (CA1) region which does not affect cell viability. This effect was attenuated through the application of the NMDA or GABAA receptor antagonists, AP-5 and picrotoxin in the dentate gyrus. There were no changes in the ratio of paired responses after EDHB application suggesting a post-synaptic mechanism of action. EDHB (100 μM), was found to inhibit synaptic plasticity in both the dentate gyrus and CA1 regions. Application of exogenous Fe2+ (100 μM) or digoxin (100 nM) did not reverse EDHB’s inhibitory effect on synaptic transmission or plasticity in both regions, suggesting that its effects may be HIF-independent. These results highlight a novel modulatory role for the PHD inhibitor EDHB in hippocampal synaptic transmission and plasticity. A novel post-synaptic mechanism of action may be involved, possibly involving NMDA and GABAA receptor activation.

Attenuation of acute restraint stress-induced depressive like behavior and hippocampal alterations with protocatechuic acid treatment in mice.

Protocatechuic acid ethyl ester (PCA), a phenolic compound, exhibits neuroprotective effects through improving endogenous antioxidant enzymatic and nonezymatic system. Based on the role of oxidative stress in modulating depressive disorders and the relationship between neuroprotective and antioxidant potential of PCA, we studied if its antidepressant like effect is associated by modulation of cerebral cortex and hippocampal antioxidant alterations. Acute restraint stress (ARS) is known to induce depressive like behavior by neuronal oxidative damage in mice. Swiss albino mice subjected to ARS exhibited an increased immobility time in forced swim test, elevated serum corticosterone and produced oxidative stress dependent alterations in cerebral cortex and hippocampus mainly increased thiobarbituric acid reactive substances and reduced catalase (CAT), superoxide dismutase (SOD) activity. Treatment with PCA was able to prevent stress induced immobility time in forced swim test without altering locomotor activity in mice. Further, PCA treatment attenuated the elevation of serum corticosterone, lipid peroxidation and restored enzymatic antioxidants in cerebral cortex and hippocampus in ARS mice. Altogether, the experimental findings demonstrate the notion that PCA exhibit antidepressant like activity might be related, at least in part, to its capability of modulating antioxidant defense system and oxidative damage induced by ARS in cerebral cortex and hippocampus in mice and thus maintain the pro-/anti-oxidative homeostasis.

Abstract 1025: A prolyl-hydroxylase inhibitor, ethyl-3,4-dihydroxybenzoate, induces cell autophagy and apoptosis in esophageal squamous cell carcinoma cells

Abstract The protocatechuic acid ethyl ester ethyl-3,4-dihydroxybenzoate (EDHB) is an antioxidant found in the testa of peanut seeds. The cytotoxic effect of EDHB on esophageal squamous cell carcinoma (ESCC) cells was investigated and 46 up- and down-regulated genes involved in several signaling pathways associated with cell cycle regulation and cellular metabolism were identified. Our studies have shown that EDHB can effectively induce autophagy and apoptosis of esophageal cancer cells by BNIP3 and NDRG1 respectively, and AKR1C family were one of the differentially expressed genes after cells treated with EDHB. We also found that the esophageal cancer cells with higher (KYSE 180) and lower (KYSE 510) AKR1C expressing levels were selected, and the cell proliferation was found inhibited more effectively in KYSE 180 than KYSE 510 cells after treated with EDHB. Furthermore, at the same condition, the effective subunits of AKR1C superfamily, AKR1C1/C2, were identified quantitatively by multiple reaction monitoring (MRM) assays. And the involvement of AKR1C1/C2 in the metabolism of the EDHB in ESCC cells and induced cell death. When autophagy was inhibited using 3-methyladenine (3-MA), KYSE 180 cells exhibited higher sensitivity to EDHB and it may act as metabolic substrate of AKR1C1/C2. These results indicate that esophageal cancer patients with high expression of AKR1C1/C2 are more sensitive to EDHB and facilitate its induced autophagy and apoptosis that providing potential guidance for the chemoprevention of ESCC. Citation Format: Wei Li, Guixue Hou, Dianrong Zhou, Xiaomin Lou, Yang Xu, Siqi Liu, Xiaohang Zhao. A prolyl-hydroxylase inhibitor, ethyl-3,4-dihydroxybenzoate, induces cell autophagy and apoptosis in esophageal squamous cell carcinoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1025.

Antioxidative extracts and phenols isolated from Qinghai–Tibet Plateau medicinal plant Saxifraga tangutica Engl.

Saxifraga tangutica Engl., is a medicinal herb that grows on the Qinghai–Tibet Plateau. Extracts and phenols from the Qinghai population have been subjected to antioxidative assays against DPPH radical-scavenging and reducing power (FRAP). The 50% ethanol extract showed strong antioxidative activity against DPPH and FRAP, with IC50±SEM [μg/mL] values of 9.38±0.46 and 15.46±0.52, respectively. The antioxidative activity-guided fractionations were performed according to the DPPH and FRAP screening results. Fourteen fractions from the 50% ethanol extract showed dissimilar antioxidative activity against DPPH and FRAP of 8.16±0.76∼38.42±0.58μg/mL and 13.22±0.68∼61.47±0.49μg/mL. The chemical assay-guided separation of the active fractions (fractions 3, 6, 7 and 8) led to eight phenols: protocatechuic aldehyde (1), ethyl gallate (2), rhododendrin (3), p-hydroxyacetophenone (4), rhododendrol (5), protocatechuic acid ethyl ester (6), frambinone (7) and ethylparaben (8). All phenols are reported here for the first time from S. tangutica Engl. Protocatechuic aldehyde (1), ethyl gallate (2), rhododendrin (3) and protocatechuic acid ethyl ester (6) showed strong antioxidative activities (IC50±SEM [mM] between 8.79±0.15 and 4.25±0.47 and between 6.15±0.48 and 2.83±0.49) against DPPH and FRAP.

Antibacterial Activity of Protocatechuic Acid Ethyl Ester on Staphylococcus aureus Clinical Strains Alone and in Combination with Antistaphylococcal Drugs.

The aim of the presented study was to examine in vitro the antibacterial activity of protocatechuic acid ethyl ester (ethyl 3,4-dihydroxybenzoate, EDHB) against Staphylococcus aureus clinical isolates alone and in the combination with four selected antibiotics. The EDHB antimicrobial activity was tested against twenty S. aureus strains isolated from the clinical samples, and three reference strains. The phenotypes and genotypes of resistance to methicillin for the tested strains were defined as well as the phenotypic resistance to macrolides, lincosamides and streptogramin B (MLSB). EDHB displayed diverse activity against examined S. aureus strains with the minimal inhibitory concentration (MIC) within the range from 64 to 1024 µg/mL. Addition of ¼ MIC of EDHB into the Mueller-Hinton Agar (MHA) resulted in augmented antibacterial effect in the presence of clindamycin. In the case of cefoxitin no synergistic effect with EDHB was noted. For erythromycin and vancomycin the decrease of mean MICs in the presence of EDHB was observed but did not reach statistical significance. The results of the present study showed that in vitro EDHB possesses antibacterial activity against S. aureus clinical strains and triggers a synergistic antimicrobial effect with clindamycin and to the lesser extent with erythromycin and vancomycin.

Participation of phenylalanine ammonia-lyase (PAL) in increased phenolic compounds in fresh cold stressed walnut (Juglans regia L.) kernels

Mature fresh walnut (Juglans regia L.) kernels showed increased phenolics under cold storage in a previous study. The aim of the present work was to investigate changes in individual soluble phenolic compounds under cold stress in relation to changes in total and specific activity of phenylalanine ammonia-lyase (PAL) as an approach to study the association of particular compounds with phenylpropanoid pathway (PhP). Treatments with inhibitors of phenylalanine ammonia-lyase (PAL), mRNA, RNA and protein synthesis, as well as, activities of the enzymes polyphenol oxidase (PPO) and peroxidase (POD) were included in the experiment. Treated samples were stored at 1°C and 90% RH for 20d. Results revealed increases in specific and total activity of PAL during cold storage. Among phenolics, 2,4-dihydroxybenzoic acid and protocatechuic acid ethyl ester were identified by HPLC–DAD–ESI-MS. Increases in acids 4-hydroxybenzoic, 2,4-dihydroxybenzoic, syringic and vanillic agreed with PAL activity increases, whereas in ellagic were largely independent on PAL. Increases in protocatechuic acid and decreases in protocatechuic acid ethyl ester exhibited no direct relation to PAL.

A prolyl-hydroxylase inhibitor, ethyl-3,4-dihydroxybenzoate, induces cell autophagy and apoptosis in esophageal squamous cell carcinoma cells via up-regulation of BNIP3 and N-myc downstream-regulated gene-1.

The protocatechuic acid ethyl ester ethyl-3,4-dihydroxybenzoate is an antioxidant found in the testa of peanut seeds. Previous studies have shown that ethyl-3,4-dihydroxybenzoate can effectively reduce breast cancer cell metastasis by inhibiting prolyl-hydroxylase. In this study, we investigated the cytotoxic effect of ethyl-3,4-dihydroxybenzoate on esophageal squamous cell carcinoma cells in vitro and identified key regulators of ethyl-3,4-dihydroxybenzoate-induced esophageal cancer cell death through transcription expression profiling. Using flow cytometry analysis, we found that ethyl-3,4-dihydroxybenzoate induced S phase accumulation, a loss in mitochondrial membrane permeabilization, and caspase-dependent apoptosis. Moreover, an expression profile analysis identified 46 up- and 9 down-regulated genes in esophageal cancer KYSE 170 cells treated with ethyl-3,4-dihydroxybenzoate. These differentially expressed genes are involved in several signaling pathways associated with cell cycle regulation and cellular metabolism. Consistent with the expression profile results, the transcriptional and protein expression levels of candidate genes NDRG1, BNIP3, AKR1C1, CCNG2 and VEGFA were found to be significantly increased in treated KYSE 170 cells by reverse-transcription PCR and western blot analysis. We also found that protein levels of hypoxia-inducible factor-1α, BNIP3, Beclin and NDRG1 were increased and that enriched expression of BNIP3 and Beclin caused autophagy mediated by microtubule-associated protein 1 light chain 3 in the treated cells. Autophagy and apoptosis were activated together in esophageal cancer cells after exposed to ethyl-3,4-dihydroxybenzoate. Furthermore, knock-down of NDRG1 expression by siRNA significantly attenuated apoptosis in the cancer cells, implying that NDRG1 may be required for ethyl-3,4-dihydroxybenzoate-induced apoptosis. Together, these results suggest that the cytotoxic effects of ethyl-3,4-dihydroxybenzoate were mediated by the up-regulation of NDRG1, BNIP3, Beclin and hypoxia-inducible factor-1α, initiating BNIP3 and Beclin mediated autophagy at an early stage and ultimately resulting in esophageal cancer cell apoptosis.

In vitro anti-osteoporosis properties of diverse Korean Drynariae rhizoma phenolic extracts.

Drynariae rhizoma has been used to prevent bone loss that occurs with increasing age. However, the chemical compounds in extracts that act on bone metabolism in herbal medicine are poorly understood. This study aimed to investigate and compare the extraction efficacy of polyphenolic compounds, antioxidant activity, and in vitro anti-osteoporosis properties of water extract (DR-DW) and ethanol extract (DR-EtOH) from D. rhizoma. Total phenolics and flavonoids were better extracted with 70% EtOH, and this extraction method also resulted in higher antioxidant activity and in vitro anti-osteoporosis properties in these extracts. In particular, the contents of phloroglucinol, protocatechuic acid ethyl ester, 2-amino-3,4-dimethyl-benzoic acid, 3-(3,5-dimethyl-pyrazol-1-yl)-benzoic acid, chlorogenic acid, syringic acid, trans-ferulic acid, (−)-epigallocatechin, epigallocatechin gallate, quercetin dehydrate, luteolin and emodin in DR-EtOH were higher than those in DR-DW. These results indicated that DR-EtOH could be a good source of natural herbs with anti-osteoporosis properties.

Amelioration of cognitive, motor and endogenous defense functions with silymarin, piracetam and protocatechuic acid in the cerebral global ischemic rat model

AimsThe neuroprotective activities of silymarin, piracetam and protocatechuic acid ethyl ester (PCA) on cerebral global ischemic/reperfusion were evaluated in a rat model. Main methodsA midline ventral incision was made in the throat region. The right and left common carotid arteries were located and a bilateral common carotid artery occlusion (BCCAO) was performed for 30min using atraumatic clamps followed by a 24h period of reperfusion. Neurological/behavioral functions (cognitive and motor), endogenous defense systems (lipid peroxidation, glutathione, catalase, and superoxide dismutase), reduced water content and infarct size and histopathological alterations were then studied. Key findingsSilymarin and PCA treatments significantly improved cognitive, motor and endogenous defense functions, histopathological alterations, and, reduced both water content and infarct size compared to the vehicle-treated ischemic control group. Piracetam treatment improved neurological and histopathological alterations, reduced water content and infarct size, but failed to restore/prevent the impaired endogenous defense functions significantly. SignificanceSilymarin showed better neuroprotection than piracetam and PCA in experimentally induced global ischemic/reperfusion and was able to facilitate mnemonic performance.

Storage of fresh walnuts (Juglans regia L.) – Low temperature and phenolic compounds

Undried or fresh walnut (Juglans regia L.) kernels are a less widespread product than the dried kernels with no information concerning their storage. Weight loss, respiration, ethylene production, colour, total phenolics (TP) and total antioxidant capacity (TAC) were examined in fresh de-hulled walnuts of cv Franquette with or without extraction from the shell during storage in air at 1°C and 90% RH for 20–40d. The effect of low temperature on TP, TAC and individual phenolic compounds was also investigated during the storage of fresh shelled kernels at 1°C and 8°C for up to 30d. Walnuts were harvested at the commercially mature stage. Respiration, as determined at 20°C, decreased sharply in shelled kernels during the first 20d at 1°C, but gradually in whole walnuts during 40d storage. No ethylene production was detected in samples. Before storage, the TP concentration in fresh kernels was already 1.2-times higher than in kernels dried at 36°C for 24h. Additionally, TP and TAC increased by 1.2- and 1.3-fold, respectively, in fresh kernels stored at 1°C for 20d and remained almost stable thereafter. Shelling increased kernel browning slightly at the lower temperature, but had no effect on TP and TAC values. At 1°C, 4-hydroxybenzoic, protocatechuic, vanillic, ellagic, 2,4-dihydroxybenzoic and syringic acids exhibited major increases within the first 20d and did not change subsequently. At 8°C, no increases in TP, TAC and most phenolic compounds were observed apart from those in 2,4-dihydroxybenzoic and syringic acids. By contrast, protocatechuic acid ethyl ester decreased at both storage temperatures, the decrease being promoted by the higher temperature used. Ellagic acid was the major acid observed in all cases. Treatments with actinomycin D, cordycepin, cycloheximide and 2-aminoindane-2-phosphonic acid (inhibitor of phenylalanine ammonia-lyase or PAL inhibitor) inhibited TP increases at 1°C, indicating the induction of at least the phenylpropanoid pathway in fresh walnuts at 1°C.

Silymarin improves the behavioural, biochemical and histoarchitecture alterations in focal ischemic rats: A comparative evaluation with piracetam and protocatachuic acid

Comparative neuroprotective potential of silymarin, piracetam and protocatechuic acid ethyl ester (PCA) was evaluated in focal ischemic rats. Various pharmacological, biochemical (lipid peroxidation, reduced glutathione, catalase, nitrite content, brain water content) and behavioural (memory impairment, motor control, neurological score) including infarct size and histopathological alterations were evaluated. Silymarin (200mg/kg) and PCA treatment significantly improved behavioural, biochemical and histopathological changes, and reduced water content and infarct size. However, piracetam only improved behavioural and histopathological changes, reduced water content and infarct size. The findings indicate that silymarin exhibits neuroprotective activity better than PCA and piracetam in focal ischemia/reperfusion reflected by its better restoration of behavioural and antioxidant profile.

Studies on chemical constituents of <I>Chaenomeles speciosa</I> (Sweet) Nakai (Ⅱ)

Objective:To investigate the chemical constituents of Chaenomeles speciosa.Methods:The chemical constituents of Chaenomeles speciosa was analyzed by various chromatographic methods.The structures of the compounds were identified based on physicochemical properties and spectral data.Results:Nine compounds were obtained from the ethyl acetate fraction of C.speciosa and were identified as methyl chlorogenate (Ⅰ),5-O-cafeoyl quinic acid butyl ester (Ⅱ),quinic acid butyl ester (Ⅲ),5-hydroxymethyl-furan-2-carbaldehyde (Ⅳ),triacontanoic acid (Ⅴ),(-)-epicatichin (Ⅵ),7,8-dihydroxy-coumanrin (Ⅶ),protocatechuic acid ethyl ester (Ⅷ),and protocatechuic acid (Ⅸ).Conclusion:Compounds Ⅲ-Ⅷ have been obtained from this genus for the first time.

Polyhydroxybenzoates Inhibit Ascorbic Acid Activation of Mitochondrial Glycerol-3-phosphate Dehydrogenase: IMPLICATIONS FOR GLUCOSE METABOLISM AND INSULIN SECRETION

Glycerol-3-phosphate dehydrogenase from pig brain mitochondria was stimulated 2.2-fold by the addition of 50 microm l-ascorbic acid. Enzyme activity, dependent upon the presence of l-ascorbic acid, was inhibited by lauryl gallate, propyl gallate, protocatechuic acid ethyl ester, and salicylhydroxamic acid. Homogeneous pig brain mitochondrial glycerol-3-phosphate dehydrogenase was activated by either 150 microm L-ascorbic acid (56%) or 300 microm iron (Fe(2+) or Fe(3+) (62%)) and 2.6-fold by the addition of both L-ascorbic acid and iron. The addition of L-ascorbic acid and iron resulted in a significant increase of k(cat) from 21.1 to 64.1 s(-1), without significantly increasing the K(m) of L-glycerol-3-phosphate (10.0-14.5 mm). The activation of pure glycerol-3-phosphate dehydrogenase by either L-ascorbic acid or iron or its combination could be totally inhibited by 200 microm propyl gallate. The metabolism of [5-(3)H]glucose and the glucose-stimulated insulin secretion from rat insulinoma cells, INS-1, were effectively inhibited by 500 microm or 1 mm propyl gallate and to a lesser extent by 5 mm aminooxyacetate, a potent malate-aspartate shuttle inhibitor. The combined data support the conclusion that l-ascorbic acid is a physiological activator of mitochondrial glycerol-3-phosphate dehydrogenase, that the enzyme is potently inhibited by agents that specifically inhibit certain classes of di-iron metalloenzymes, and that the enzyme is chiefly responsible for the proximal signal events in INS-1 cell glucose-stimulated insulin release.