Ascorbic acid oxidation of thiol groups from dithiotreitol is mediated by its conversion to dehydroascorbic acid

The aim of the present study was to investigate whether the in vitro pro-oxidant effect of ascorbic acid towards thiol groups could be mediated by free radicals formed during its autooxidation and/or by a direct oxidation of -SH groups by its oxidized form (dehydroascorbic acid). This hypothesis was examined by measuring the rate of AA (ascorbic acid) oxidation in MOPS (3-morpholinepropanesulfonic acid buffer) and phosphate buffer (PB). Here we have used dithiothreitol (DTT) as model of vicinal thiol-containing enzymes, namely delta-aminolevulinate dehydratase. The rate of AA and DTT oxidation was more pronounced in the presence of PB than in the MOPS. AA oxidation induced by iron/EDTA complex was significantly reduced by addition of superoxide dismutase, catalase and DTT to the reaction medium. H2O2 alone did not stimulate the oxidation of AA; however, AA oxidation was enhanced significantly with the addition of crescent concentrations of iron. Conversely, in DTT oxidation assay (without AA) the addition of iron, EDTA and H2O2, did not promote the oxidation of -SH groups. Our findings suggest that in the presence of physiological concentrations of AA and thiols, the oxidation of -SH groups is mediated by AA conversion to dehydroascorbic acid with the participation of iron. Furthermore, free radical species formed during the autooxidation of AA apparently did not oxidize thiol groups to a significant extent

Effect of Syzygium cumini and Bauhinia forficata aqueous-leaf extracts on oxidative and mitochondrial parameters in vitro

Aqueous-leaf extract of Syzygium cumini and Bauhinia forficata are traditionally used in the treatment of diabetes and cancer, especially in South America, Africa, and Asia. In this study, we analyzed the effects of these extracts on oxidative and mitochondrial parameters in vitro, as well as their protective activities against toxic agents. Phytochemical screenings of the extracts were carried out by HPLC analysis. The in vitro antioxidant capacities were compared by DPPH radical scavenging and Fe2+ chelating activities. Mitochondrial parameters observed were swelling, lipid peroxidation and dehydrogenase activity. The major chemical constituent of S. cumini was rutin. In B. forficata were predominant quercetin and gallic acid. S. cumini reduced DPPH radical more than B. forficata, and showed iron chelating activity at all tested concentrations, while B. forficata had not similar property. In mitochondria, high concentrations of B. forficata alone induced a decrease in mitochondrial dehydrogenase activity, but low concentrations of this extract prevented the effect induced by Fe2++H2O2. This was also observed with high concentrations of S. cumini. Both extracts partially prevented the lipid peroxidation induced by Fe2+/citrate. S. cumini was effective against mitochondrial swelling induced by Ca2+, while B. forficata alone induced swelling more than Ca2+. This study suggests that leaf extract of S. cumini might represent a useful therapeutic for the treatment of diseases related with mitochondrial dysfunctions. On the other hand, the consumption of B. forficata should be avoided because mitochondrial damages were observed, and this possibly may pose risk to human health

EFFECT OF SYZYGIUM CUMINI AND BAUHINIA FORFICATA AQUEOUS-LEAF EXTRACTS ON OXIDATIVE AND MITOCHONDRIAL PARAMETERS IN VITRO

ABSTRACT Aqueous-leaf extract of Syzygium cumini and Bauhinia forficata are traditionally used in the treatment of diabetes and cancer, especially in South America, Africa, and Asia. In this study, we analyzed the effects of these extracts on oxidative and mitochondrial parameters in vitro, as well as their protective activities against toxic agents. Phytochemical screenings of the extracts were carried out by HPLC analysis. The in vitro antioxidant capacities were compared by DPPH radical scavenging and Fe 2+ chelating activities. Mitochondrial parameters observed were swelling, lipid peroxidation and dehydrogenase activity. The major chemical constituent of S. cumini was rutin. In B. forficata were predominant quercetin and gallic acid. S. cumini reduced DPPH radical more than B. forficata, and showed iron chelating activity at all tested concentrations, while B. forficata had not similar property. In mitochondria, high concentrations of B. forficata alone induced a decrease in mitochondrial dehydrogenase activity, but low concentrations of this extract prevented the effect induced by Fe 2+ +H 2 O 2 . This was also observed with high concentrations of S. cumini. Both extracts partially prevented the lipid peroxidation induced by Fe 2+ /citrate. S. cumini was effective against mitochondrial swelling induced by Ca 2+ , while B. forficata alone induced swelling more than Ca 2+ . This study suggests that leaf extract of S. cumini might represent a useful therapeutic for the treatment of diseases related with mitochondrial dysfunctions. On the other hand, the consumption of B. forficata should be avoided because mitochondrial damages were observed, and this possibly may pose risk to human health

Effects of gender and geographical origin on the chemical composition and antiradical activity of Baccharis myriocephala and and Baccharis trimera.

This study aimed to characterize and compare essential oils and ethyl acetate fractions obtained in basic and acidic conditions from both male and female Baccharis species (Baccharis myriocephala and Baccharis trimera) from two different Brazilian regions. Samples were characterized according to their chemical compositions and antiradical activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. Principal component analysis (PCA) provided a clear separation regarding the chemical composition of essential oils from the samples obtained from different regions by using gas chromatography?mass spectrometry with flame-ionization detection (GC-MS-FID). PCA also revealed that gender and region of plant collections did not influence the chemical composition and antiradical activity of ethyl acetate fractions, which was corroborated with hierarchical cluster analysis (HCA) data. High performance liquid chromatography with diode-array detector (HPLC-DAD) identified significant quantities of flavonoids and phenolic acids in the fractions obtained in basic and acidic fractions, respectively. The obtained results clearly demonstrated that the geographical region of plant collection influenced the chemical composition of essential oils from the studied Baccharis species. Moreover, the obtained fractions were constituted by several antiradical compounds, which reinforced the usage of these species in folk medicine.Published: 9 October 2020

Parkia biglobosa Improves Mitochondrial Functioning and Protects against Neurotoxic Agents in Rat Brain Hippocampal Slices

Objective. Methanolic leaf extracts of Parkia biglobosa, PBE, and one of its major polyphenolic constituents, catechin, were investigated for their protective effects against neurotoxicity induced by different agents on rat brain hippocampal slices and isolated mitochondria. Methods. Hippocampal slices were preincubated with PBE (25, 50, 100, or 200 µg/mL) or catechin (1, 5, or 10 µg/mL) for 30 min followed by further incubation with 300 µM H2O2, 300 µM SNP, or 200 µM PbCl2 for 1 h. Effects of PBE and catechin on SNP- or CaCl2-induced brain mitochondrial ROS formation and mitochondrial membrane potential (ΔΨm) were also determined. Results. PBE and catechin decreased basal ROS generation in slices and blunted the prooxidant effects of neurotoxicants on membrane lipid peroxidation and nonprotein thiol contents. PBE rescued hippocampal cellular viability from SNP damage and caused a significant boost in hippocampus Na+, K+-ATPase activity but with no effect on the acetylcholinesterase activity. Both PBE and catechin also mitigated SNP- or CaCl2-dependent mitochondrial ROS generation. Measurement by safranine fluorescence however showed that the mild depolarization of the ΔΨm by PBE was independent of catechin. Conclusion. The results suggest that the neuroprotective effect of PBE is dependent on its constituent antioxidants and mild mitochondrial depolarization propensity