Comparative study on antioxidant activity of different varieties of commonly consumed legumes in India

Legumes are rich source of proteins, dietary fiber, micronutrients and bioactive phytochemicals. Thirty different varieties of commonly consumed legumes in India, were screened for phenolic content and antioxidant activity using, radical scavenging [(1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenz-thiazoline-6-sulfonic acid, (ABTS⁺)], Ferric Reducing Antioxidant Power (FRAP) and metal ion (Fe²⁺) chelation assays. Legumes varied largely in their antioxidant activity. Horse gram, common beans, cowpea (brown and red) and fenugreek showed high DPPH radical scavenging activity (>400 units/g), while lablab bean (cream and white), chickpea (cream and green), butter bean and pea (white and green) showed low antioxidant activity (<125 units/g). Green gram, black gram, pigeon pea, lentils, cowpea (white) and common bean (maroon) showed intermediate activity. Similar trend was observed when the activity was assessed with ABTS⁺ and FRAP assays. Thus most of the varieties having light color seed coat, except soybean exhibited low antioxidant activity. While legumes having dark color seed coat did not always possessed high antioxidant activity (e.g. moth bean, black pea, black gram, lentils). Antioxidant activity showed positive correlation (r² > 0.95) with phenolic contents, in DPPH, ABTS⁺ and FRAP assays, whereas poor correlation (r² = 0.297) was observed between Fe²⁺ chelating activity of the legumes and phenolic contents.     

Arsenic alters monocyte superoxide anion and nitric oxide production in environmentally exposed children

Arsenic (As) exposure has been associated with alterations in the immune system, studies in experimental models and adults have shown that these effects involve macrophage function; however, limited information is available on what type of effects could be induced in children. The aim of this study was to evaluate effects of As exposure, through the association of inorganic As (iAs) and its metabolites [monomethylated arsenic (MMA) and dimethylated arsenic (DMA)] with basal levels of nitric oxide (NO⁻) and superoxide anion (O₂⁻), in peripheral blood mononuclear cells (PBMC) and monocytes, and NO⁻ and O₂⁻ produced by activated monocytes. Hence, a cross-sectional study was conducted in 87 children (6-10 years old) who had been environmentally exposed to As through drinking water. Levels of urinary As species (iAs, MMA and DMA) were determined by hydride generation atomic absorption spectrometry, total As (tAs) represents the sum of iAs and its species; tAs urine levels ranged from 12.3 to 1411 μg/g creatinine. Using multiple linear regression models, iAs presented a positive and statistical association with basal NO⁻ in PBMC (β = 0.0048, p = 0.049) and monocytes (β = 0.0044, p = 0.044), while basal O₂⁻ had a significant positive association with DMA (β = 0.0025, p = 0.046). In activated monocytes, O₂⁻ showed a statistical and positive association with iAs (β = 0.0108, p = 0.023), MMA (β = 0.0066, p = 0.022), DMA (β = 0.0018, p = 0.015), and tAs (β = 0.0013, p = 0.015). We conclude that As exposure in the studied children was positively associated with basal levels of NO⁻ and O₂⁻ in PBMC and monocytes, suggesting that As induces oxidative stress in circulating blood cells. Additionally, this study showed a positive association of O₂⁻ production with iAs and its metabolites in stimulated monocytes, supporting previous data that suggests that these cells, and particularly the O₂⁻ activation pathway, are relevant targets for As toxicity.     

β-ODAP accumulation could be related to low levels of superoxide anion and hydrogen peroxide in Lathyrus sativus L.

Level of the neuroexcitatory β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP) in grass pea (Lathyrus sativus L.) varies with development and environmental stress. Reactive oxygen species (ROS) (mainly O₂⁻ and H₂O₂) are frequently reported to play important roles in plant development and in response to various stresses. To investigate the possible inter-relationship between contents of β-ODAP and ROS, grass pea leaves have been analyzed for contents of β-ODAP, O₂⁻ and H₂O₂. The results showed that leaves containing high levels of β-ODAP, exhibited low levels of O₂⁻ and H₂O₂, while leaves with high contents of O₂⁻ and H₂O₂ accumulated little β-ODAP. The application of pyridine or ABA which inhibit the production of O₂⁻ or H₂O₂ led to an increase in β-ODAP contents in intact or detached young leaves, whereas inhibition of catalase activity using AT (3-amino-1,2,4-triazole), leading to an increase in H₂O₂ content, result in significant decrease in β-ODAP levels of detached young leaves. In addition, inoculation of Rhizobium to young seedlings enhanced O₂⁻ and H₂O₂ levels, but reduced β-ODAP contents in shoots. These results suggest that β-ODAP accumulation could be related to low levels of superoxide anion and hydrogen peroxide in grass pea tissues.     

On the antioxidant properties of kynurenic acid: Free radical scavenging activity and inhibition of oxidative stress

Kynurenic acid (KYNA) is an endogenous metabolite of the kynurenine pathway for tryptophan degradation and an antagonist of both N-methyl-d-aspartate (NMDA) and alpha-7 nicotinic acetylcholine (α7nACh) receptors. KYNA has also been shown to scavenge hydroxyl radicals (OH) under controlled conditions of free radical production. In this work we evaluated the ability of KYNA to scavenge superoxide anion (O₂⁻) and peroxynitrite (ONOO⁻). The scavenging ability of KYNA (expressed as IC₅₀ values) was as follows: OH = O₂⁻ > ONOO⁻. In parallel, the antiperoxidative and scavenging capacities of KYNA (0-150 μM) were tested in cerebellum and forebrain homogenates exposed to 5 μM FeSO₄ and 2.5 mM 3-nitropropionic acid (3-NPA). Both FeSO₄ and 3-NPA increased lipid peroxidation (LP) and ROS formation in a significant manner in these preparations, whereas KYNA significantly reduced these markers. Reactive oxygen species (ROS) formation were determined in the presence of FeSO₄ and/or KYNA (0-100 μM), both at intra and extracellular levels. An increase in ROS formation was induced by FeSO₄ in forebrain and cerebellum in a time-dependent manner, and KYNA reduced this effect in a concentration-dependent manner. To further know whether the effect of KYNA on oxidative stress is independent of NMDA and nicotinic receptors, we also tested KYNA (0-100 μM) in a biological preparation free of these receptors - defolliculated Xenopus laevis oocytes - incubated with FeSO₄ for 1 h. A 3-fold increase in LP and a 2-fold increase in ROS formation were seen after exposure to FeSO₄, whereas KYNA attenuated these effects in a concentration-dependent manner. In addition, the in vivo formation of OH evoked by an acute infusion of FeSO₄ (100 μM) in the rat striatum was estimated by microdialysis and challenged by a topic infusion of KYNA (1 μM). FeSO₄ increased the striatal OH production, while KYNA mitigated this effect. Altogether, these data strongly suggest that KYNA, in addition to be a well-known antagonist acting on nicotinic and NMDA receptors, can be considered as a potential endogenous antioxidant.     

DSM-RX78, a new phosphodiesterase inhibitor, suppresses superoxide anion production in activated human neutrophils and attenuates hemorrhagic shock-induced lung injury in rats

Neutrophils are activated following hemorrhagic shock and the accumulation of neutrophils in the lung is associated with lung injury. This research investigated the effects of a semisynthetic 2-benzoylaminobenzoic acid derivative, methyl 2-(2-fluorobenzamido)benzoate (DSM-RX78), on superoxide anion (O₂⁻) production in formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP)-activated human neutrophils, and on lung injury in Sprague-Dawley rats subjected to trauma-hemorrhage. DSM-RX78 concentration-dependently inhibited O₂⁻ production, but not elastase release, in FMLP-activated human neutrophils. DSM-RX78 displayed no superoxide-scavenging ability, and it failed to alter the subcellular NADPH oxidase activity. Significantly, DSM-RX78 increased cAMP formation and protein kinase (PK)A activity in FMLP-activated neutrophils, which occurred through the selective inhibition of cAMP-specific phosphodiesterase (PDE) activity but not an increase in adenylate cyclase function or cGMP-specific PDE activity. These results show that DSM-RX78 is a new inhibitor of cAMP-specific PDE. Moreover, DSM-RX78 reduced FMLP-induced phosphorylation of protein kinase B (Akt), but not calcium mobilization. The inhibitory effects of DSM-RX78 on O₂⁻ production and Akt phosphorylation were reversed by PKA inhibitors, suggesting that DSM-RX78 regulates O₂⁻ production of human neutrophils by promoting cAMP/PKA-dependent inhibition of Akt activation. On the other hand, administration of DSM-RX78 significantly attenuated the increase in myeloperoxidase activity and edema in the lung, as well as protein concentrations in bronchoalveolar lavage fluid in rats after trauma-hemorrhagic shock. In summary, these results strongly suggest that DSM-RX78 exerts anti-inflammatory effects, which result from the elevation of cAMP levels and PKA activity through its inhibition of cAMP-specific PDE. Also, our findings show that DSM-RX78 attenuates hemorrhagic shock-induced lung injury in rats.