AAPH-induced Oxidative Damage Research Articles

Investigation of Antioxidant Mechanisms of Novel Peptides Derived from Asian Swamp Eel Hydrolysate in Chemical Systems and AAPH-Induced Human Erythrocytes.

Sixteen novel antioxidant peptides from Asian swamp eel (ASE) were identified in previous studies. However, their chemical and cellular antioxidant mechanisms remain unclear. Molecular docking of these peptides with ABTS and DPPH radicals revealed the critical role of hydrogen bonding and Pi-Pi stacking hydrophobic interactions between hydrophobic amino acid residues and free radicals. Residues, such as tryptophan, proline, leucine, and valine, played significant roles in these interactions. All these peptides exhibited notable erythrocyte morphoprotective effects in a model of AAPH-induced oxidative damage of human erythrocytes. Erythrocyte hemolysis was reduced primarily through the modulation of both non-enzymatic (GSH/GSSG) and enzymatic antioxidant systems (SOD, CAT, and GSH-Px) by these peptides. A decrease in levels of MDA, LDH release, and hemoglobin oxidation was observed. Among the peptides, VLYPW demonstrated superior chemical and cellular antioxidant activities, which may be attributed to its higher levels of tyrosine and tryptophan, as well as to its increased hydrophobic amino acid content.

AAPH-induced oxidative damage reduced anion exchanger 1 (SLC4A1/AE1) activity in human red blood cells: protective effect of an anthocyanin-rich extract.

Introduction: During their lifespan in the bloodstream, red blood cells (RBCs) are exposed to multiple stressors, including increased oxidative stress, which can affect their morphology and function, thereby contributing to disease. Aim: This investigation aimed to explore the cellular and molecular mechanisms related to oxidative stress underlying anion exchanger 1 activity (band 3, SLC4A1/AE1) in human RBCs. To achieve this aim, the relationship between RBC morphology and functional and metabolic activity has been explored. Moreover, the potential protective effect of an anthocyanin-enriched fraction extracted from Callistemon citrinus flowers was studied. Methods: Cellular morphology, parameters of oxidative stress, as well as the anion exchange capability of band 3 have been analyzed in RBCs treated for 1h with 50mM of the pro-oxidant 2,2'-azobis (2-methylpropionamide)-dihydrochloride (AAPH). Before or after the oxidative insult, subsets of cells were exposed to 0.01μg/mL of an anthocyanin-enriched fraction for 1h. Results: Exposure to AAPH caused oxidative stress, exhaustion of reduced glutathione, and over-activation of the endogenous antioxidant machinery, resulting in morphological alterations of RBCs, specifically the formation of acanthocytes, increased lipid peroxidation and oxidation of proteins, as well as abnormal distribution and hyper-phosphorylation of band 3. Expected, oxidative stress was also associated with a decreased band 3 ion transport activity and an increase of oxidized haemoglobin, which led to abnormal clustering of band 3. Exposure of cells to the anthocyanin-enriched fraction prior to, but not after, oxidative stress efficiently counteracted oxidative stress-related alterations. Importantly, protection of band3 function from oxidative stress could only be achieved in intact cells and not in RBC ghosts. Conclusion: These findings contribute a) to clarify oxidative stress-related physiological and biochemical alterations in human RBCs, b) propose anthocyanins as natural antioxidants to neutralize oxidative stress-related modifications, and 3) suggest that cell integrity, and therefore a cytosolic component, is required to reverse oxidative stress-related pathophysiological derangements in human mature RBCs.

Protective Effects of Mulberry (Morus atropurpurea Roxb.) Leaf Protein Hydrolysates and Their In Vitro Gastrointestinal Digests on AAPH-Induced Oxidative Stress in Human Erythrocytes.

Mulberry leaf protein hydrolysates (HMP), and their in vitro gastrointestinal digests (GHMP), have shown favorable chemical antioxidant activities. The aim of this study is to investigate the potential protective effects of HMP and GHMP against 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress in human erythrocytes. The inhibition rate of hemolysis, the reactive oxygen species (ROS) level, the concentration of malondialdehyde (MDA), the reduced glutathione (GSH) and oxidized glutathione (GSSH), and the enzymatic activities of total superoxide dismutase (SOD), catalase (CAT), and cellular glutathione peroxidase (GSH-Px) were evaluated as the biomarkers of oxidative status in human erythrocytes. The results showed that HMP and GHMP effectively inhibit the occurrence of erythrocyte hemolysis in the range of 0.025-1.0 mg/mL, and the inhibition rates of HMP and GHMP reached 92% and 90% at concentrations of 0.4 mg/mL and 1.0 mg/mL, respectively. HMP and GHMP reduced the AAPH-induced oxidative hemolysis damage via suppressing the generation of ROS by inhibiting the formation of MDA, maintaining the balance of GSH/GSSG, and preserving the activities of the antioxidant enzymes, including SOD, GSH-Px, and CAT. Our findings revealed that both HMP and GHMP could be used as natural antioxidants, and have the potential for further application in the development of functional foods.

Effects of simulated gastrointestinal digestion on chickpea protein, and its hydrolysate physicochemical properties, erythrocyte haemolysis inhibition, and chemical antioxidant activity

Chickpea protein and its hydrolysates have good antioxidant activity. Proteins and peptides are degraded and modified in the gastrointestinal tract before being digested and absorbed, a process that changes their physicochemical and biological properties. Changes in structure and antioxidant capacity of the chickpea protein and its hydrolysates after simulated gastrointestinal digestion were studied. The secondary structure, amino acid composition, and chemical antioxidant activity of chickpea protein and its hydrolysates were determined, and their protective effects on AAPH-induced erythrocyte oxidative damage were studied. Results showed that chickpea protein hydrolysate was easier to be digested by the gastrointestinal tract than chickpea protein. After digestion, the chemical antioxidant capacity of chickpea protein and its hydrolysates increased in a dose-dependent manner, and showed a protective effect against erythrocytes AAPH-induced oxidative damage. Chickpea protein and its hydrolysates can be used as natural antioxidants to promote healthy digestion.

Novel Antioxidant Peptides from Pearl Shell Meat Hydrolysate and Their Antioxidant Activity Mechanism

Free radicals are associated with aging and many diseases. Antioxidant peptides with good antioxidant activity and absorbability are one of the hotspots in antioxidant researches. In our study, pearl shell (Pinctada martensii) meat hydrolysate was purified, and after identification by proteomics, six novel antioxidant peptides SPSSS, SGTAV, TGVAS, GGSIT, NSVAA, and GGSLT were screened by bioinformatics analysis. The antioxidant peptides exhibited good cellular antioxidant activity (CAA) and the CAA of SGTAV (EC50: 0.009 mg/mL) and SPSSS (EC50: 0.027 mg/mL) were better than that of positive control GSH (EC50: 0.030 mg/mL). In the AAPH-induced oxidative damage models, the antioxidant peptides significantly increased the viability of HepG2 cells, and the cell viability of SGTAV, SPSSS, and NAVAA were significantly restored from 79.41% to 107.43% and from 101.09% and 100.09%, respectively. In terms of antioxidant mechanism by molecular docking, SGTAV, SPSSS, and NAVAA could tightly bind to free radicals (DPPH and ABTS), antioxidant enzymes (CAT and SOD), and antioxidant channel protein (Keap1), suggesting that the antioxidant peptides had multiple antioxidant activities and had structure-activity linkages. This study suggests that the antioxidant peptides above are expected to become new natural materials for functional food industries, which contribute to the high-value applications of pearl shell meat.

Antioxidant potential of hydrolysate-derived seahorse (Hippocampus abdominalis) peptide: Protective effects against AAPH-induced oxidative damage in vitro and in vivo

In this study, seahorse peptide (SHP) was isolated from an alcalase-treated hydrolysate from Hippocampus abdominalis and assessed for its antioxidant potential against AAPH-induced oxidative stress damage. AAPH stimulation significantly decreased cell viability and increased intracellular reactive oxygen species (ROS) production in Vero cells. SHP treatment increased cell viability and remarkably lowered ROS production under AAPH-induced oxidative stress. Furthermore, it protected against AAPH-induced apoptotic DNA damage. Western blot analysis demonstrated that SHP treatment remarkably increased the protein expression levels of catalase and SOD in AAPH-induced Vero cells. A zebrafish study revealed that SHP-treated zebrafish embryos resulted in lower cell death, ROS generation, and lipid peroxidation than the AAPH-treated group. These results suggest that SHP is a potent functional antioxidant that could be developed as a natural antioxidant in the food and functional food industries.

Protective Effect of Flavonoids from Mulberry Leaf on AAPH-Induced Oxidative Damage in Sheep Erythrocytes.

To evaluate the antioxidant activity of flavonoids extracted from Chinese herb mulberry leaves (ML), flavonoids from mulberry leaves (FML) were extracted and purified by using ultrasonic-assisted enzymatic extraction and D101 macroporous resin. Using LC-MS/MS-Liquid Chromatography with tandem mass spectrometry analysis, hesperidin, rutoside, hyperoside, cyanidin-3-o-glucoside, myricitrin, cyanidin, and quercetin were identified, and NMR and UV were consistent with the verification of IR flavonoid characteristics. The antioxidant activity of FML has also been evaluated as well as the protective effect on 2,2 0-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress. The results showed that FML exhibited powerful antioxidant activity. Moreover, FML showed dose-dependent protection against AAPH-induced sheep erythrocytes' oxidative hemolysis. In the enzymatic antioxidant system, pretreatment with high FML maintained the balance of SOD, CAT, and GSH-Px; in the non-enzymatic antioxidant system, the content of MDA can be effectively reduced after FML treatment. This study provides a research basis for the development of natural products from mulberry leaves.

Protecting Effect of Bacillus coagulans T242 on HT-29 Cells Against AAPH-Induced Oxidative Damage.

The aim of the present study was to investigate the in vitro antioxidant potential of Bacillus coagulans T242. B. coagulans T242 showed better antioxidant activities, including the 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging ability, lipid peroxidation inhibiting ability and reducing ability, than those exerted by Lactobacillus rhamnosus GG (LGG). B. coagulans T242 positively regulated the expression of the nuclear factor erythroid 2-relatedfactor 2/Kelch-like ECH-associated protein-1 (Nrf2/Keap1) pathway-related proteins (Nrf2, Keap1, heine oxygenase-1 (HO-1)); increased antioxidant enzymes (glutathione peroxidase (GSH-Px), catalase (CAT), superoxide dismutase (SOD)); reduced the content of malondialdehyde (MDA) level; decreased the expression of inflammatory-related cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α); and thus increased the survival rate in 2,2'-azobis (2-methylpropionamidine) dihydrochloride (AAPH)-damaged HT-29 cells. This study proved that B. coagulans T242 exerted antioxidative effects by quenching oxygen free radicals and activating the Nrf2 signaling pathway in HT-29 cells.

A flavone from the ethyl acetate extract of Leea rubra leaves with DNA damage protection and antineoplastic activity

Among the major constituents of Leea rubra (Family Vitaceae) leaves, phenolic and flavonoind compounds are most important for therapeutic purposes and the plant parts have been used in traditional medicine to treat several diseases for long. Thus, in order to scientifically confirm the traditional uses of the L. rubra leaves, the present study was designed to investigate the efficacy of the isolated flavones against AAPH induced oxidative damage to pUC19 DNA by gel electrophoresis and antineoplastic activity was evaluated on Ehrlich ascites carcinoma (EAC) bearing Swiss albino mice by evaluating percentage inhibition of cell growth, morphological changes of EAC cells and hematological parameters of the mice. The isolation was carried out by column chromatography and structure was revealed by 1H-NMR and 13C NMR. The result shows that, the isolated compound was identified as myricetin 4'-methoxy-3-O-α-l-rhamnopyranoside based on previously reported data. The isolated flavone effectively inhibited AAPH-induced oxidative damage to DNA; because it could inhibit the formation of circular and linear forms of the DNA. In anti-proliferative assay, 76% growth inhibition of EAC cells was observed as compare to the control mice (p<0.05) at a dose 100 mg/kg body weight. Thus the isolated flavone showed great importance as a possible therapeutic agent in preventing oxidative damage to DNA and the chronic diseases caused by such DNA damage, and can also become important in cancer chemotherapy.

Antioxidative and Cytoprotective Effects of Ganoderma applanatum and Fomitopsis pinicola in PC12 Adrenal Phaeochromocytoma Cells.

Considering the impact of oxidative stress on the development of many diseases, together with the role of natural antioxidants in maintaining physiological balance in humans, medicinal mushrooms are potential sources of bioactive compounds against many diseases. In the present work, in vitro evaluation of the biological activities of the alcoholic extracts of two wild tree mushrooms, namely, Ganoderma applanatum and Fomitopsis pinicola, has been performed. Extraction of G. applanatum (GAE) and F. pinicola (FPE) was conducted with 60% ethanol and 100% ethanol sequentially. UPLC-MS/MS identification was conducted on the two mushrooms extracts. A total of 15 substances were identified in GAE, including 3 spiro meroterpenoids and 12 triterpenoids; a total of 14 chemical constituents were iden¬tified in FPE, including 8 triterpenoids, 4 triterpene glycosides, 1 lanosterol, and 1 lanostanoid. The resulting extracts were examined for their in vitro antioxidative and cytoprotective effects against AAPH-induced oxidative damage. Our results demonstrated that both extracts have potent antioxidative activities, when GAE was 0.2 mg/mL, the clearance rates of DPPH and ABTS have reached 93.34% and 99.93%, respectively. When FPE was 1.4 mg/mL and 0.6 mg/mL, the scavenging rates of DPPH and ABTS have reached 91.76% and 100%, respectively. Both the alcoholic extracts of G. applanatum and F. pinicola were able to protect the AAPH-induced damage and could effectively inhibit cell aging via β-galactosidase (SA β-gal) staining activity test and scanning electron microscopy analysis.

Evaluation of Leea rubra Leaf Extract for Oxidative Damage Protection and Antitumor and Antimicrobial Potential.

Background The leaves of Leea rubra contain an abundance of phenolic constituents and have medicinal uses as antipyretic and diaphoretic agents and are also used in the treatment of stomach ache, rheumatism, arthritis etc. In spite of the traditional uses, data on the scientific evaluation of the plant are not sufficient. So, the present study was designed to evaluate the protective role of the extract against oxidative damage to DNA and human erythrocytes as well as antitumor and antibacterial activities against some resistant bacteria. Methods The protective activity of the ethyl acetate fraction (EAF) of the extract was investigated by evaluating the inhibition of oxidative damage of pUC19 plasmid DNA as well as hemolysis and lipid peroxidation damage to human erythrocytes induced by 2,2′-azobis-2-amidinopropane (AAPH). Antitumor activity was assessed by evaluating the percentage inhibition of cell growth, morphological changes of Ehrlich's ascites carcinoma (EAC) cells, and hematological parameters. Antimicrobial activity was determined by the disc diffusion method against different resistant microorganisms. Results EAF effectively inhibited AAPH-induced oxidative damage to DNA because it can inhibit the transformation of the supercoiled form of plasmid DNA to open circular and further linear form. The oxidative hemolysis caused by AAPH in human erythrocytes was inhibited by EAF extract in a time-dependent manner, and the production of malondialdehyde (MDA) was significantly reduced, which indicates the prevention of lipid peroxidation. In antitumor assay, 76% growth of inhibition of EAC was observed compared with the control mice (p < 0.05) at a dose of 100 mg/kg body weight. Antimicrobial activity was evaluated against two pathogenic resistant microorganisms (Escherichia coli and Pseudomonas aeruginosa), and the highest antimicrobial activity was observed against Pseudomonas spp. Conclusion EAF may have great importance in preventing oxidative damage to DNA, erythrocytes, and other cellular components as well as can be a good candidate in cancer chemotherapy and treating infectious diseases caused by antibiotic-resistant bacteria.

Antioxidant and fibroblast-activating activities of the by-product of skate chondroitin extractive production

Owing to the increasing popularity of chondroitin sulfate (CS) for joint pain treatment, the CS-production industry has been producing an increasing amount of waste, which includes type II collagen, non-collagenous proteins, and residual CS. To effectively utilize these resources, we intended to develop new products from the by-product of skate chondroitin sulfate production (BP-sCS). In this study, we examined the antioxidant and fibroblast-activating properties of BP-sCS, intending to apply it for a wound-healing promoter. BP-sCS exhibited ABTS and DPPH radical scavenging activities, protected L929 fibroblasts from H2O2- or AAPH-induced oxidative stress, and scavenged intracellular reactive oxygen species. Moreover, BP-sCS promoted L929 fibroblast proliferation/metabolism and stimulated collagen deposition into the extracellular matrix. In addition, BP-sCS counteracted AAPH-induced oxidative stress damage that inhibited fibroblast migration. These effect were attributed to the cooperation among the molecules of BP-sCS, namely, type II collagen peptides, non-collagenous peptides, and CS polysaccharides. Our findings indicate that BP-sCS has the potential as a novel wound-healing promoter. This study is the first step toward the realization of a sustainable CS-production industry by waste utilization in healthcare products.

Antioxidant efficacy of (−)-loliolide isolated from Sargassum horneri against AAPH-induced oxidative damage in Vero cells and zebrafish models in vivo

Seaweed-derived compounds are known to possess various biological activities. The present study evaluated the antioxidant potential of (−)-loliolide, a monoterpenoid isolated from Sargassum horneri in Vero cells and zebrafish models. (−)-Loliolide was purified from the chloroform fraction of an S. horneri methanol extract using high-performance centrifugal partition chromatography (HPCPC). HPCPC was found to be an effective method to isolate (−)-loliolide, yielding a high purity product. Electron spin resonance evaluation demonstrated that (−)-loliolide had significant alkyl radical scavenging activity (IC50: 0.043 ± 0.005 mg mL−1). In addition, our study showed that (−)-loliolide demonstrated dose-dependent protective effects for Vero cell viability against 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced intracellular reactive oxygen species (ROS). Moreover, (−)-loliolide reduced lipid peroxidation in AAPH-induced zebrafish embryos, while ameliorating the survival rate and cell death in a dose-dependent manner. These results reveal the antioxidant potential of (−)-loliolide. Future studies highlighting the potential applications of S. horneri in manufacturing functional food ingredients are required.

Decursin inhibits the oxidation of low-density lipoprotein and protects human aortic endothelial cells against oxidative damage

Atherosclerosis is the pathological basis of cardiovascular diseases (CVDs) which are the leading cause of death worldwide. The pathogenesis of atherosclerosis itself is complex. Low-density lipoprotein (LDL) oxidation has been shown to increase lipid peroxide levels in arterial wall of atherosclerosis lesion site. Decursin is a coumarin with a range of pharmacological effects. The present study investigated the inhibitory effect of decursin on LDL oxidation, and its protective effect against oxidative damage in human aortic endothelial cells (HAECs). Two models of oxidative damage were used in this study: Cu2+-induced LDL oxidative damage and 2,2'-azobis-2-methyl-propanimidyl, dihydrochloride (AAPH)-induced oxidative damage of HAECs. The inhibitory effect of decursin on LDL oxidation, and its protective effect on oxidative damage of HAECs were determined. The results showed that the level of thiobarbituric acid reactive substances (TBARS) was significantly increased by Cu2+, but was significantly and concentration-dependently reduced after treatment with decursin (p &lt; 0.05). There were only a few viable cells in AAPH-treated group, but treatment with decursin led to significant, time- and concentration-dependent increases in their viability (p &lt; 0.05). The AAPH-induced oxidative damage significantly increased the activity of lactate dehydrogenase (LDH) and level of reactive oxygen species (ROS), but significantly reduced the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) (p &lt; 0.05). However, treatment of HAECs with decursin significantly and concentration-dependently reduced the LDH activity and level of ROS, but significantly increased the activities of SOD and GPx, concentration-dependently (p &lt; 0.05). It also significantly and concentration-dependently reduced apoptosis induced by AAPH (p &lt; 0.05). These results show that decursin effectively inhibits LDL oxidation induced by Cu2+, and protects HAECs from oxidative damage caused by AAPH in vitro via a mechanism involving activation of SOD and GPx.

Neuroprotective Effects of Phlorotannin-Rich Extract from Brown Seaweed Ecklonia cava on Neuronal PC-12 and SH-SY5Y Cells with Oxidative Stress.

Neurodegenerative disorders in the elderly are characterized by gradual loss of memory and cognitive function. Oxidative stress caused by reactive oxygen species is associated with progressive neuronal cell damage and death in Alzheimer's disease, one of the most common neurodegenerative disorders. An edible brown seaweed, Ecklonia cava, contains a variety of biologically active compounds such as phlorotannins. In this study, we comparatively evaluated the total phenolic content, antioxidant capacity, and neuroprotective effects of the phlorotannin-rich extract from E. cava (PEEC). The total phenolic content of PEEC and dieckol was 810.8 mg gallic acid equivalents (GAE)/g and 996.6 mg GAE/g, respectively. Antioxidant capacity of PEEC was 1,233.8 mg vitamin C equivalents (VCE)/g and 392.1 mg VCE/g determined using ABTS and DPPH assays, respectively, while those of dieckol were 2,238.4 mg VCE/g and 817.7 mg VCE/g. High-performance liquid chromatography results revealed 48.08 ± 0.67 mg dieckol/g of PEEC. PEEC had neuroprotective effects in pheochromocytoma (PC-12) and human neuroblastoma (SH-SY5Y) cells against H2O2- and AAPH-induced oxidative damage, partly due to reduced intracellular oxidative stress. PEEC treatment inhibited acetylcholinesterase and butyrylcholinesterase in a dose-dependent manner. Taken together, these findings suggest that PEEC is a good source of antioxidants and neuroprotective materials.

Synthesis, Radical-Scavenging Activities, and Protective Effects against AAPH-Induced Oxidative Damage in DNA and Erythrocytes of Piperine Derivatives

Piperine amino acid derivatives containing phenolic hydroxyl groups were synthesized using piperine as the raw material by amide hydrolysis, amidation, ester hydrolysis, and deacetalization. The obtained products were characterized by mass spectrometry and nuclear magnetic resonance. The antioxidant activity of the piperine derivatives was evaluated by the DPPH and ABTS scavenging rates and the total antioxidant capacity. The results showed that the piperine amino acid (4a–4d) had relatively weak radical-scavenging ability, while the piperine amino acid derivatives (5a–5d) containing phenolic hydroxyl groups had significant radical-scavenging effects. In addition, the total reducing ability of 5a–5d was better than that of piperine. The study also found that piperine derivatives containing phenolic hydroxyl groups played an important role in inhibiting oxidative damage in DNA and erythrocytes.

Protective effects of flavonoids from Gynostemma pentaphyllum on oxidative damage in LLC-PK1 cells

Four flavonoids were isolated from Gynostemma pentaphyllum by chromatography methods and their structures were identified by MS and NMR spectra data as quercetin-3-O-( 2″,6″-di-α-L-rhamnosyl)-β-D-galactopyranoside( 1),quercetin-3-O-( 2″,6″-di-α-L-rhamnosyl)-β-D-glucopyranoside( 2),quercetin-3-O-( 2″-α-L-rhamnosyl)-β-D-galactopyranoside( 3),and quercetin-3-O-( 2″-α-L-rhamnosyl)-β-D-glucopyranoside( 4). Among them,compounds 1-3 were obtained from the Cucurbitaceae family for the first time.The four flavonoids showed potent antioxidant effects against the DPPH,·OH and ■radicals in vitro,especially for DPPH radical scavenging activity with the IC50 values of 71. 4,29. 5,48. 3 and 79. 2 μmol·L~(-1),respectively. Moreover,the four flavonoids displayed strong cytoprotection against AAPH-induced oxidative damage in LLC-PK1 cells by suppressing the increase of malondialdehyde( MDA) and the decrease of the superoxide dismutase( SOD) and glutathione( GSH). Since further research is needed to prove its efficacy in vivo and clinical trial,the study may provide four potential antioxidants from G. pentaphyllum.

Electrochemical behavior and anti/prooxidant activity of thioethers with redox-active catechol moiety

A number of asymmetrical thioethers combining sterically hindered catechol moiety and different groups (polar, non-polar, or redox active) at sulfur atom have been synthesized. Redox transformations of sulfides were studied by cyclic voltammetry. The electrooxidation of thioethers at the first stage leads to the formation of o-benzoquinones. The presence of a redox-active thioether linker and additional phenolic fragment favors to an extension of the range of redox properties for such functionalized catechols. The introduction of the thioether fragment into catechol ring affects not only the electrochemical behavior of the compounds, but also the antioxidant activity. The antioxidant activities of the compounds were evaluated using 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH) assay, the oxidative damage of the DNA, the reaction of 2,2′-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced glutathione depletion, and the process of lipid peroxidation of rat liver (Wistar) homogenates in vitro. The compounds have greater antiradical effect than 3,5-di-tert-butylcatechol (CatH2) in DPPH assay. In the course of the AAPH-induced oxidative DNA damage, all tested compounds exhibit inhibitory activity unlike CatH2. Among the compounds under investigation, three catechol thioethers reveal mostly antioxidant properties. Several compounds with polar groups possess dual anti/prooxidant activity. The thiolation of catechol ring can change properties of target thiothers by a variation of different organic fragments at sulfur atom.

Two novel polysaccharides from the torus of Saussurea laniceps protect against AAPH-induced oxidative damage in human erythrocytes

Two major polysaccharides (SLT-3, SLT-4) were isolated from the torus of Saussurea laniceps. Their molecular weight, monosaccharide compositions and the ability to protect human erythrocytes from oxidative damage induced by AAPH were assessed. Results showed that the Mw of SLT-3 and SLT-4 were 10,113 Da and 12,392 Da. SLT-3 was composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose, and arabinose in a molar ratio of 0.25:0.53:0.19:15.35:0.51:1.10:0.63:1.73, whereas SLT-4 was composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose in a molar ratio of 0.92:5.61:0.93:19.50:2.42:5.27:3.01. Pretreatment with SLT-3 and SLT-4 reduced MDA content, inhibited the generation of intracellular ROS and maintained the balance of GSH and GSSG in AAPH-treated erythrocytes. Furthermore, the activities of intracellular antioxidant enzymes, such as SOD, GSH-Px and CAT, were attenuated in polysaccharide treated cells. The results provide an important basis for the development of S. laniceps as a natural antioxidant.

Strawberry and Achenes Hydroalcoholic Extracts and Their Digested Fractions Efficiently Counteract the AAPH-Induced Oxidative Damage in HepG2 Cells.

Strawberry fruits are highly appreciated by consumers worldwide due to their bright red color, typical aroma, and juicy texture. While the biological activity of the complete fruit has been widely studied, the potential beneficial effects of the achenes (commonly named seeds) remain unknown. In addition, when raw fruit and achenes are consumed, the digestion process could alter the release and absorption of their phytochemical compounds, compromising their bioactivity. In the present work, we evaluated the protective effects against oxidative damage of nondigested and digested extracts from strawberry fruit and achenes in human hepatocellular carcinoma (HepG2) cells. For that purpose, cells were treated with different concentration of the extracts prior to incubation with the stressor agent, AAPH (2,2′-azobis(2-amidinopropane) dihydrochloride). Subsequently, intracellular accumulation of reactive oxygen species (ROS) and the percentage of live, dead, and apoptotic cells were determined. Our results demonstrated that all the evaluated fractions were able to counteract the AAPH-induced damage, suggesting that the achenes also present biological activity. The positive effects of both the raw fruit and achenes were maintained after the in vitro digestion process.