Induction of phenolsulfotransferase expression by phenolic acids in human hepatoma HepG2 cells

Antiglycation and antioxidant potential of coumaric acid isomers: a comparative in-vitro study

Advanced glycation end products (AGEs) are the product of non-enzymatic glycation of serum proteins. AGEs increase reactive oxygen species (ROS) formation, which leads to diabetic complications. Phytochemicals exhibit lesser side effects as compared to conventional therapy. In this study, three isomers of coumaric acid (ortho, meta, para) were used to deduce the better one in terms of reducing diabetic complications. For this purpose, human serum albumin (HSA) was incubated with glucose in the absence and presence of isomers for 28 days. To avoid any growth, NaN3 was added and temperature was kept constant throughout the incubation period. Studies like fluorescence, circular dichroism spectroscopy, fructosamine analysis, free lysine estimation, free thiol group estimation were done. To investigate the ROS production, fluorescence microscopy of isolated lymphocytes using DAPI and dichloro-dihydro-fluorescein diacetate were performed. Molecular docking and molecular dynamic simulations (root-mean-square deviation, root-mean-square fluctuations, radius of gyration and solvent-accessible surface area) of HSA and peroxisome proliferator activated receptor (PPAR) alpha and gamma were also done. It was observed that in glycated protein samples, the level of absorbance, fluorescence, fructosamine and carbonyl group increased along with the loss of secondary structure, free lysine and thiol group. These parameters were found gradually recovered in treated samples. ROS production and apoptosis were found to be reduced in lymphocytes treated with p-Coumaric acid (pCA)-treated protein samples as compared to lymphocyte treated with glycated protein. Computational modelling suggested a stable complex formation of HSA and PPARs with pCA. Results with pCA at 200 µM were consistently better than other two isomers. Our next step is to evaluate this study in rats.Communicated by Ramaswamy H. Sarma.

Qualitative and quantitative analysis of phenolic acid glycosides in Ginkgo biloba L. leaf, G. biloba leaf extract and its injection

Ginkgo biloba L. leaf (GBL) is one of the most commonly used medicinal plants in the world. Phenolic acids with biological activities have a relatively high content in G. biloba leaf extracts (GBE); therefore they are of great significance for the quality control of GBL, GBE and its preparations. However, there have been few studies focused on their analysis. In this work, 12 phenolic acids, including 11 phenolic acid glycosides, were identified by liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS). Then, a method combining enzymolysis with HPLC was established for quantification of phenolic acid glycosides. It was found that the aglycones of phenolic acid glycosides mainly comprised five phenolic acids: 2,4,6-trihydroxybenzoic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid and p-coumaric acid. The quantitative method was validated, and the correlation coefficient (0.9993-0.9999), recovery (≥88.4%), repeatability (≤0.8%), and inter-day precision (≤5.5%) were satisfactory. Finally, the contents of glycosides of five phenolic acids in GBL, GBE and GBE injection from different sources were determined by the developed method. The method was accurate, repeatable and practicable, which could be helpful for the quantification of phenolic acid glycosides in other products containing GBL or GBE.

An aqueous pomegranate seed extract ameliorates oxidative stress of human hepatoma HepG2 cells

BACKGROUND

Aqueous pomegranate seed extract (PSE), a by-product of the pomegranate juice industry, was recently identified as a potential antiglycative ingredient. Ellagic acid was proposed as the major polyphenol responsible for the antiglycative activity as exerted in in vitro models. However, there is no information on safety aspects of this extract in biological systems before its application as ingredient. The cytotoxicity of PSE (1-100 µg mL(-1) ) was evaluated by determining its effect on cell viability and redox status of cultured HepG2 cells. The protective effect of the PSE against oxidative stress induced by tert-butyl hydroperoxide (t-BOOH) was also investigated.

RESULTS

No changes in cell integrity or intrinsic antioxidant status resulted from a direct treatment with aqueous PSE, even at high dosage. In addition, reactive oxygen species (ROS) induced by t-BOOH were reduced by 21% when cells were pretreated with 100 µg mL(-1) of aqueous PSE at 180 min. The range of concentrations investigated was effective in decreasing the ROS formation but not in a dose-dependent manner.

CONCLUSION

Aqueous pomegranate seed extract enhances human hepatoma cells integrity and resistance to cope with a stressful situation at concentration up to 100 µg mL(-1) .

Plant phenolics regulate neoplastic cell growth and survival: a quantitative structure-activity and biochemical analysis

The anti-tumour activities of many plant phenolics at high concentrations (>100 micromol/L) suggest their potential use as dietary supplements in cancer chemoprevention and cancer chemotherapy. However, it is not clear what impact phenolic compounds have at the physiological concentrations obtained through consumption of high phenolic diets on neoplastic cells. In the present study, 54 naturally occurring phenolics were evaluated at physiologically relevant concentrations for their capacity to alter PC12 cell viability in response to serum deprivation, the chemotherepeutic agent etoposide, and the apoptogen C2-ceramide. Surprisingly, novel mitogenic, cytoprotective, and antiapoptotic activities were detected. Quantitative structure-activity relationship modelling indicated that many of these activities could be predicted by compound lipophilicity, steric bulk, and (or) antioxidant capacity, with the exception of inhibition of ceramide-induced apoptosis. Where quantitative structure-activity relationship analysis was insufficient, biochemical assessment demonstrated that the benzoate orsellinic acid blocked downstream caspase-12 activation following ceramide challenge. These findings demonstrate substantive mitogenic, cytoprotective, and antiapoptotic biological activities of plant phenolics on neoplastic cells at physiologically relevant dietary concentrations that should be considered in chemopreventive and chemotherapeutic strategies.

Induction of human sulfotransferase 1A3 (SULT1A3) by glucocorticoids

Sulfotransferases (SULTs) play an important role in the detoxification and bioactivation of endogenous compounds and xenobiotics. Studies on rat sulfotransferases had shown that SULT genes, like cytochrome P450 genes, can be regulated by ligands that bind nuclear receptors. For human SULT genes, the regulation of human SULT2A1 expression is currently the best characterized. In this study, we systematically examined the regulation of human SULT1A genes by glucocorticoids. Treatment of the human hepatocellular carcinoma derived HepG2 cells with 10(-7) M dexamethasone did not affect the SULT1A1 activity toward p-nitrophenol. In contrast, SULT1A3 activity toward dopamine was significantly induced. Transient transfection of the SULT1A3 5'-flanking region/luciferase reporter construct showed that SULT1A3 was responsive to dexamethasone and prednisolone in a concentration-dependent manner with maximal induction at 10(-7) M dexamethasone or 1 microM prednisolone. In addition, induction by dexamethasone was dependent on the level of expression of the glucocorticoid receptor. Analysis of the 5'-flanking region led to the identification of a putative glucocorticoid response element at position (-1211 to -1193) upstream of the transcription start site and deletion or mutation of this element resulted in a loss of response. In summary, the data from this study shows that the human SULT1A3 gene is inducible by glucocorticoids through a glucocorticoid receptor-mediated mechanism and the glucocorticoid response element at position (-1211 to -1193) is necessary for this induction.