Flavonols and flavan-3-ols as modulators of xanthine oxidase and manganese superoxide dismutase activity

The Ultrasound-Assisted Extraction of Polyphenols from Mexican Firecracker (Hamelia patens Jacq.): Evaluation of Bioactivities and Identification of Phytochemicals by HPLC-ESI-MS

The objective of the present work was to optimize the extraction of phytochemicals from Hamelia patens Jacq. by ultrasound-assisted extraction. Taguchi L9 orthogonal array was used to evaluate the factors solid/liquid ratio (1:8, 1:12, and 1:16), extraction time (10, 20, and 30 min), and ethanol concentration (0, 35, and 70%). Total polyphenols were the response variable. Chromatographic fractionation using Amberlite XAD-16 was carried out and the total polyphenols, flavonoids, and condensed tannins were quantified. The redox potential, the reduction of the 2,2-diphenyl-1-picrylhydrazyl (DPPH), and the lipid oxidation inhibition were determined. Anti-bacterial activity was evaluated. The phytochemicals were identified by liquid chromatography coupled to mass spectrometry. Optimal extraction conditions were a solid/liquid ratio of 1:16, ethanol of 35%, and 10 min of ultrasound-assisted extraction. Maximum polyphenol content in the crude extract was 1689.976 ± 86.430 mg of gallic acid equivalents (GAE)/100 g of dried plant material. The purified fraction showed a total polyphenols content of 3552.84 ± 7.25 mg of GAE, flavonoids 1316.17 ± 0.27 mg of catechin equivalents, and condensed tannins 1694.87 ± 22.21 mg of procyanidin B1 equivalents, all per 100 g of purified fraction. Its redox potential was 553.93 ± 1.22 mV, reducing 63.08 ± 0.42% of DPPH radical and inhibiting 77.78 ± 2.78% of lipid oxidation. The polyphenols demonstrated antibacterial activity against Escherichia coli, Klebsiella pneumonia, and Enterococcus faecalis. The HPLC-ESI-MS analysis revealed the presence of coumarins, hydroxycinnamic acids, and flavonoids.

Induction of Autophagy by Pterostilbene Contributes to the Prevention of Renal Fibrosis via Attenuating NLRP3 Inflammasome Activation and Epithelial-Mesenchymal Transition

Chronic kidney disease (CKD) is recognized as a global public health problem. NLRP3 inflammasome activation has been characterized to mediate diverse aspect mechanisms of CKD through regulation of proinflammatory cytokines, tubulointerstitial injury, glomerular diseases, renal inflammation, and fibrosis pathways. Autophagy is a characterized negative regulation mechanism in the regulation of the NLRP3 inflammasome, which is now recognized as the key regulator in the pathogenesis of inflammation and fibrosis in CKD. Thus, autophagy is undoubtedly an attractive target for developing new renal protective treatments of kidney disease via its potential effects in regulation of inflammasome. However, there is no clinical useful agent targeting the autophagy pathway for patients with renal diseases. Pterostilbene (PT, trans-3,5-dimethoxy-4-hydroxystilbene) is a natural analog of resveratrol that has various health benefits including autophagy inducing effects. Accordingly, we aim to investigate underlying mechanisms of preventive and therapeutic effects of PT by reducing NLRP3 inflammasome activation and fibrosis through autophagy-inducing effects. The renal protective effects of PT were evaluated by potassium oxonate (PO)-induced hyperuricemia and high adenine diet-induced CKD models. The autophagy induction mechanisms and anti-fibrosis effects of PT by down-regulation of NLRP3 inflammasome are investigated by using immortalized rat kidney proximal tubular epithelial NRK-52E cells. To determine the role of autophagy induction in the alleviating of NLRP3 inflammasome activation and epithelial-mesenchymal transition (EMT), NRK-52E with Atg5 knockdown [NRK-Atg5-(2)] cells were applied in the study. The results indicated that PT significantly reduces serum uric acid levels, liver xanthine oxidase activity, collagen accumulation, macrophage recruitment, and renal fibrosis in CKD models. At the molecular levels, pretreatment with PT downregulating TGF-β-triggered NLRP3 inflammasome activation, and subsequent EMT in NRK-52E cells. After blockage of autophagy by treatment of Atg5 shRNA, PT loss of its ability to prevent NLRP3 inflammasome activation and EMT. Taken together, we suggested the renal protective effects of PT in urate nephropathy and proved that PT induces autophagy leading to restraining TGF-β-mediated NLRP3 inflammasome activation and EMT. This study is also the first one to provide a clinical potential application of PT for a better management of CKD through its autophagy inducing effects.

Phytochemical composition and the cholinesterase and xanthine oxidase inhibitory properties of seed extracts from the Washingtonia filifera palm fruit

The chemical composition and biological properties of palm Washingtonia filifera (Lindl.) H. Wendl. seeds are seldom studied.

Antioxidant and pro-oxidant mechanisms of (+) catechin in microsomal CYP2E1-dependent oxidative stress

The objectives of this work were to evaluate the effects of catechin on cytochrome P450 2E1 (CYP2E1)-dependent oxidative stress. Microsomes co-expressing human CYP2E1 with NADPH cytochrome P450 reductase and cytochrome b5 were incubated with NADPH and DTPA at pH 7.0. Superoxide anion generation was specifically detected by spin-trapping with DEPMPO. Generation of the DEPMPO-OOH adduct was not observed in the absence of CYP2E1 and in the presence of superoxide dismutase (SOD) or catechin, while catalase was ineffective. Reactive oxygen species generation was detected with 1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine (CPH) by the EPR-detection of its oxidation product, 3-carboxy-proxyl radical (CP^●). CP^● generation was not observed in the absence of CYP2E1 and in the presence of SOD, while catalase was ineffective. In contrast, catechin increased CPH oxidation, an effect that was not observed in the absence of CYP2E1 or in the presence of SOD (but not catalase), and was not associated with an increase in oxygen consumption. Catechin also increased the non-specific oxidation of the probes CPH and hydroethidine by the superoxide anion-generating system xanthine plus xanthine oxidase. Catechin oxidized CPH in the presence of horseradish peroxidase plus hydrogen peroxide, a catechin radical-generating system. In conclusion, catechin exhibits both antioxidant (superoxide-scavenging) and pro-oxidant effects under CYP2E1-dependent oxidative stress.

Potential efficiency of antioxidants to prevent pressure ulcers. A neglected hypothesis

Pressure ulcers are necrotic lesions mainly due to capillary hypoperfusion. It is well known that hypoxia and also subsequent oxygenation at reperfusion provoke the formation of reactive oxygen species (ROS) responsible for cell death. The hypothesis of their participation in the pathogenesis of pressure ulcers has already been tested; several antioxidants have the capacity to inhibit skin necrosis in animal models but their efficiency in preventing bedsores has never been demonstrated in patients. The failure of clinical trials to show the protective activity of some antioxidants does not rule out the involvement of ROS in ischemic ulcers and the potential efficacy of other antioxidants in preventing their formation remains possible.