Simultaneously Determined Antioxidant and Pro-Oxidant Activity of Randomly Selected Plant Secondary Metabolites and Plant Extracts.

Oxidative stress is a well-known phenomenon arising from physiological and nonphysiological factors, defined by the balance between antioxidants and pro-oxidants. While the presence and uptake of antioxidants are crucial, the pro-oxidant effects have not received sufficient research attention. Several methods for assessing pro-oxidant activity, utilizing various mechanisms, have been published. In this paper, we introduce a methodology for the simultaneous determination of antioxidant and pro-oxidant activity on a single microplate in situ, assuming that the FRAP method can measure both antioxidant and pro-oxidant activity due to the generation of pro-oxidant Fe2+ ions in the Fenton reaction. Systematic research using this rapid screening method may help to distinguish between compounds with dominant antioxidant efficacy and those with dominant pro-oxidant effects. Our preliminary study has revealed a dominant pro-oxidant effect for compounds with a higher number of oxygen heteroatoms, especially sp2 hybridized compounds (such as those containing keto groups), such as flavonoids and plant extracts rich in these structural types. Conversely, catechins, carotenoids, and surprisingly, extracts from birch leaves and chestnut leaves have demonstrated dominant antioxidant activity over pro-oxidant. These initial findings have sparked significant interest in the systematic evaluation of a more extensive collection of compounds and plant extracts using the developed method.

Pycnogenol Cytotoxicity in Pancreatic INS-1E ß cells Induced by Calcium Dysregulation.

Natural standardized flavonoid extract from the bark of Pinus pinaster, Pycnogenol (Pyc), was recently found to decrease intensively the activity of sarcoplasmic reticulum Ca2+ -ATPase of rabbit skeletal muscle (SERCA1). On the basis of this inhibitory effect in a cell-free system and similarities of SERCA1 to its other isoforms, proapoptotic properties of Pyc may be expected in cellular systems. Pycnogenol (40-100 µg/mL) induced a concentration-dependent decrease of the viability of pancreatic INS-1E ß cells associated with induction of apoptosis. In addition, intracellular Ca2+ level increase was found along with reduction of protein expression level of SERCA2b and impairment of insulin secretion by ß cells. These facts indicate that Pyc may induce apoptosis by impairment of calcium homeostasis. Copyright © 2017 John Wiley & Sons, Ltd.

Antioxidant and Proteinase Inhibitory Activities of Selected Poppy (Papaver somniferum L.) Genotypes.

Poppy seeds (Papaver somniferum L.) belong to tasty food ingredients however, they should be considered also as valuable source of biologically active compounds. Content of selected metabolites, antioxidant and proteinase inhibitory activities were analyzed in vitro in extracts from seeds of fifteen poppy genotypes. Considerable variation in all parameters was detected within the set of analyzed poppy genotypes. The genotype Major expressed the highest antioxidant activity determined by all four methodological approaches (DPPH, ABTS, FRAP, RP). The genotype MS 423 exhibited the highest inhibitory activities against trypsin, thrombin and collagenase. Very specific position among all had the genotype Redy. Its grain extract reached significantly high levels in 9 out of 14 measured parameters (TPC, TFC, TTC, TAC, FRAP, RP, inhibitory activities against trypsin, thrombin, collagenase). Edible grains of poppy are valuable source of natural compounds which may be beneficial in pathological states associated with oxidative stress or increased proteinase activities.

Rutin stimulates sarcoplasmic reticulum Ca(2+)-ATPase activity (SERCA1) and protects SERCA1 from peroxynitrite mediated injury.

In this study we analyzed the protective action of the flavonoid rutin on peroxynitrite (ONOO(-)) mediated impairment of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA1 isoform), especially related to posttranslational and conformational changes. Rutin concentration dependently protected ONOO(-) induced SERCA1 activity decrease with effective concentration EC50 of 18 ± 1.5 µM. Upon treatment with ONOO(-), this flavonoid also prevented SERCA1 from thiol group oxidation and significantly reduced tyrosine nitration and protein carbonyl formation. In the absence of ONOO(-), rutin (250 and 350 µM) stimulated SERCA1 activity at 2.1 mM [ATP] and 10 µM [Ca(2+)]free. According to changes in the kinetic parameters V max and K m with regard to [ATP], rutin (250 µM) increased the rate of enzyme catalysis and decreased the affinity of SERCA1 to ATP. FITC fluorescence decreased in the presence of rutin (150 and 250 µM), indicating conformational changes in the cytosolic ATP binding region of SERCA1. In silico study confirmed the binding of rutin in the cytosolic region of SERCA1, in the vicinity of the ATP binding site. Residue Glu183 localized within the conserved TGES loop was identified to play a key role in rutin-SERCA1 interaction (H-bond length of 1.7 Å), elucidating the ability of rutin to affect the affinity of SERCA1 to ATP. The binding of rutin in the proximity of Lys515 is likely to cause a decrease in FITC fluorescence.

Natural and synthetic antioxidants: an updated overview.

Abstract The current understanding of the complex role of ROS in the organism and pathological sequelae of oxidative stress points to the necessity of comprehensive studies of antioxidant reactivities and interactions with cellular constituents. Studies of antioxidants performed within the COST B-35 action has concerned the search for new natural antioxidants, synthesis of new antioxidant compounds and evaluation and elucidation of mechanisms of action of both natural and synthetic antioxidants. Representative studies presented in the review concern antioxidant properties of various kinds of tea, the search for new antioxidants of herbal origin, modification of tocopherols and their use in combination with selenium and properties of two promising groups of synthetic antioxidants: derivatives of stobadine and derivatives of 1,4-dihydropyridine.

Pycnogenol and Ginkgo biloba extract: effect on peroxynitrite-oxidized sarcoplasmic reticulum Ca-ATPase.

The effect of two natural standardized plant extracts, Pycnogenol(®) and EGb 761, on sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) activity and posttranslational modifications induced by peroxynitrite was investigated to assess their possible protective role. EGb 761 was found to have a protective effect on SERCA activity in the concentration range of 5-40 µg/ml. On the other hand, Pycnogenol(®) caused a decrease of SERCA activity at concentrations of 25 µg/ml. EGb 761 did not prevent protein carbonyl formation upon oxidation with peroxynitrite. On the contrary, Pycnogenol(®) at the concentrations of 5 and 10 µg/ml significantly decreased the level of protein carbonyls by 44% and 54%, respectively. Neither Pycnogenol(®) nor EGb 761 exerted a protective effect against thiol group oxidation.The plant extracts studied modulated peroxynitrite-injured SERCA activity by different ways and failed to correlate with posttranslational modifications. Their effect seems to be associated with their ability to change SERCA conformation rather than by their antioxidant capacity.