P.S. Rajini

Antioxidant-mediated protective effect of potato peel extract in erythrocytes against oxidative damage

Potato peels are waste by-product of the potato processing industry. They are reportedly rich in polyphenols. Our earlier studies have shown that extracts derived from potato peel (PPE) possess strong antioxidant activity in chemical and biological model systems in vitro, attributable to its polyphenolic content. The main objective of this study was to investigate the ability of PPE to protect erythrocytes against oxidative damage, in vitro. The protection rendered by PPE in erythrocytes was studied in terms of resistance to oxidative damage, morphological alterations as well as membrane structural alterations. The total polyphenolic content in PPE was found to be 3.93 mg/g powder. The major phenolic acids present in PPE were predominantly: gallic acid, caffeic acid, chlorogenic acid and protocatechuic acid. We chose the experimental prooxidant system: FeSO(4) and ascorbic acid to induce lipid peroxidation in rat RBCs and human RBC membranes. PPE was found to inhibit lipid peroxidation with similar effectiveness in both the systems (about 80-85% inhibition by PPE at 2.5 mg/ml). While PPE per se did not cause any morphological alteration in the erythrocytes, under the experimental conditions, PPE significantly inhibited the H(2)O(2)-induced morphological alterations in rat RBCs as revealed by scanning electron microscopy. Further, PPE was found to offer significant protection to human erythrocyte membrane proteins from oxidative damage induced by ferrous-ascorbate. In conclusion, our results indicate that PPE is capable of protecting erythrocytes against oxidative damage probably by acting as a strong antioxidant.

Protective effect of potato peel extract against carbon tetrachloride-induced liver injury in rats.

Our earlier studies have shown that extracts derived from potato peel (PPE) are rich in polyphenols and possess strong antioxidant activity both in vitro and in vivo. The objective of the present study was to investigate its potential to offer protection against acute liver injury in rats. Rats pretreated with PPE (oral, 100mg/kgb.w./day for 7 days) were administered a single oral dose carbon tetrachloride (CCl(4), 3ml/kg b.w., 1:1 in groundnut oil) and sacrificed 8h of post-treatment. Hepatic damage was assessed by employing biochemical parameters (transaminase enzyme levels in plasma and liver [AST-aspartate transaminase; ALT-alanine transaminase, LDH-lactate dehydrogenase]). Further, markers of hepatic oxidative damage were measured in terms of malondialdehyde (MDA), enzymic antioxidants (CAT, SOT, GST, GPX) and GSH (reduced glutathione) levels. In addition, the CCl(4)-induced pathological changes in liver were evaluated by histopathological studies. Our results demonstrated that pretreatment of rats with PPE significantly prevented the increased activities of AST and ALT in serum, prevented the elevation of hepatic MDA formation as well as protected the liver from GSH depletion. PPE pretreatment also restored CCl(4)-induced altered antioxidant enzyme activities to control levels. The protective effect of PPE was further evident through the decreased histological alterations in liver. Our findings provide evidences to demonstrate that PPE pretreatment significantly offsets CCl(4)-induced liver injury in rats, which may be attributable to its strong antioxidant propensity.

Reversible hyperglycemia in rats following acute exposure to acephate, an organophosphorus insecticide : Role of gluconeogenesis

The present study was undertaken to investigate the hyperglycemic potential of acute exposure to acephate and its etiology employing rat model system. Oral administration of acephate (140mg/kg b.w.) caused reversible hyperglycemia as evidenced by peak increase in blood glucose at 2h after the administration (87% over control) followed by trend of normalization. In further experiment carried out to understand the etiology of the induced hyperglycemia, we observed that 2h exposure to acephate caused significant increase in blood glucose, plasma corticosterone (78%) and activities of two gluconeogenesis enzymes in liver viz., glucose-6-phosphatase (91%) and tyrosine aminotransferase (84%) compared to that in control. When rats were exposed to acephate for 6h, decrement was observed in elevated levels of blood glucose, plasma corticosterone and the gluconeogenesis enzymes of the liver. Adrenal cholesterol levels in acephate-exposed rats were significantly depleted. While the glycogen content in liver of 2-h exposure group was comparable to control, a tremendous increase in liver glycogen content ( approximately 3.5 folds) was observed in rats of the 6-h exposure group. Our results demonstrate that acephate causes reversible hyperglycemia in rats probably by enhancing hepatic glucose output via gluconeogenesis. A role for hyperactivity of adrenal cortex is suggested in increased gluconeogenesis while significant attenuation in elevated levels of blood glucose and the activity the gluconeogenesis enzyme, glucose-6-phosphatase in liver with concomitant increase in liver glycogen are indicative of the onset of counter-regulatory responses such as hyperinsulinemia, to overcome the induced hyperglycemia.

Hyperglycemic and stressogenic effects of monocrotophos in rats: Evidence for the involvement of acetylcholinesterase inhibition

The purpose of this study was to investigate the involvement of acetylcholinesterase (AChE) inhibition in hyperglycemic and stressogenic effects of monocrotophos in rats. Oral administration of monocrotophos (1.8 mg/kg b.w., 1/10 LD(50)) caused reversible hyperglycemia in rats with peak increase occurring at 2 h following administration. The hyperglycemic outcome at 2 h was accompanied by significant inhibition of acetylcholinesterase (AChE) activity in brain (84%), adrenal (68%) and liver (53%) and stressogenic effects as revealed by marked increase in plasma corticosterone (102%) and liver tyrosine aminotransferase (TAT) (104%) activity. At 4 h following administration, there was normalization of hyperglycemia and hypercorticosteronemia, marginal attenuation of liver TAT activity and marked increase in liver glycogen content, without spontaneous reactivation of AChE activity in the organs studied. Interestingly, pre-treatment of rats with acetylcholine (ACh) receptor antagonists-atropine sulfate and methyl atropine nitrate offered significant protection against hyperglycemia, hypercorticosteronemia and increased liver TAT activity induced by monocrotophos. Our results clearly demonstrate the involvement of AChE inhibition in hyperglycemia and stressogenic effects of monocrotophos in rats following acute exposure. Protection offered by both, general and peripheral ACh antagonists provide further evidence for the involvement of peripheral AChE inhibition in the monocrotophos-induced effects.

Evaluation of sublethal effects of dichlorvos upon Caenorhabditis elegans based on a set of end points of toxicity

The primary objective of this study was to examine a possible correlation among the three endpoints of toxicity, namely, stress gene expression (hsp16), feeding, and acetylcholinesterase (AChE) activity in transgenic C. elegans (hsp16‐lacZ) exposed to sublethal concentrations of dichlorvos, an organophosphorus insecticide. Worms exposed to dichlorvos (at 5, 40, and 80 μM) exhibited a concentration‐dependent inhibition in feeding with total cessation in feeding occurring beyond 4 h of exposure. Concomitantly, marked and dose‐dependent inhibition (69%–90%) of AChE was also evident after 4 h of exposure. Induction of heat shock protein (Hsp) was evident after 4 h of exposure (as seen from quantitative analysis), although maximum expression of Hsp was evident only after 24 h of exposure (as evident from qualitative analysis). Interestingly, the Hsp induction was restricted only to the pharyngeal region. Significant correlation was discernible between the three evaluated end points suggesting their possible interrelated role in the physiological dysfunctions evoked by sublethal concentrations of dichlorvos.

Biochemical and physiological responses in Caenorhabditis elegans exposed to sublethal concentrations of the organophosphorus insecticide, monocrotophos.

The objective of this study was to investigate the impact of sublethal concentrations of MCP on definitive markers of toxicity and oxidative balance in the nematode, Caenorhabditis elegans. Exposure of worms to 0.85, 1.7 and 3.4mM (1/40, 1/20 and 1/10 LC50; LC50=34 mM) for 4h at 20°C induced significant perturbations in physiological parameters such as decreased brood size (47-73%), increased paralysis (47-85%) and inhibition of the activities of acetylcholinesterase (75-86%) and carboxylesterase (76-81%). These changes were accompanied by distinct oxidative impairments as evidenced by increased reactive oxygen species, decline in glutathione content and decrease in superoxide dismutase activity. Our results clearly demonstrate that low concentrations of MCP may alter the physiological and biochemical status in the nematode, thereby affecting the organisms fitness. Our findings on C. elegans provide an easy diagnosis for OPI contamination and may become helpful in evaluating the ecotoxicological effects of OPI in the aquatic environment near agricultural fields.

Elicitation of Dopaminergic Features of Parkinson’s Disease in C. elegans by Monocrotophos, an Organophosphorous Insecticide

Positive correlations have been suggested between usage of pesticides and the incidence of Parkinsons disease (PD) through epidemiological as well as few experimental evidences. Organophosphorus insecticides (OPI), which are extensively used in agricultural and household insect control, have been the subject of increasing concern in the past decades due to their neurotoxic potential. However, very few studies have demonstrated the potentials of OPI to induce features of PD in model organisms. In the present study, Caenorhabditis elegans was selected as the model organism to evaluate the potential of monocrotophos (MCP), an OPI, to elicit dopaminergic features of Parkinsons disease in terms of dopamine content, basic movement and integrity of dopaminergic neurons along with its effect on acetylcholinesterase (AChE) activity and life span. All the responses elicited by MCP were compared with that elicited by 1-methyl-4-phenyl- 1, 2, 3, 6-tetrahydropyridine (MPTP) in both N2 and BZ555 worms. N2 worms were exposed to varying concentrations of MCP (50, 100 and 200 μM) or MPTP (200, 300 and 400 μM) for 48 hours and locomotory rate, as measured by the number of body bends made in 20 seconds, was enumerated. Worms subjected to the same dose paradigms were also analyzed for the dopamine content by HPLC. The results indicated a significant reduction in the dopamine levels in the worms that were treated with MCP/MPTP and this correlated with the changes in locomotion compared to untreated worms. Worms treated with MCP also exhibited significant reduction in AChE activity. Both MPTP and MCP caused a marked reduction in life span in the worms. Transgenic worms (BZ555, which has GFP tagged to its 8 dopaminergic neurons) exposed to MCP and MPTP at the above concentrations showed a dose-dependent reduction in the number of green pixels in CEP and ADE neurons which also correlated with the neurodegeneration as visualized by decreased fluorescence in photomicrographs. Taken together, our data demonstrate that low levels of MCP elicits dopaminergic features of PD in C. elegans.

Augmentation of hepatic and renal oxidative stress and disrupted glucose homeostasis by monocrotophos in streptozotocin-induced diabetic rats

Several recent studies have demonstrated that organophosphorus insecticides (OPI) possess the potential to disrupt glucose homeostasis leading to hyperglycemia in experimental animals. The propensity of OPI to induce hyperglycemia along with oxidative stress may have far-reaching consequences on diabetic outcomes and associated complications. The primary objective of this study was to assess the potential of monocrotophos (MCP), an extensively used OPI, on hepatic and renal oxidative stress markers and dysregulation of hepatic glucose homeostasis in experimentally induced diabetic rats. Rats rendered diabetic by a single dose of streptozotocin (60mg/kg b.w) were orally administered MCP (0.9mg/kg b.w/d for 5d). Monocrotophos per se caused only a marginal increase in blood glucose levels but significantly elevated the blood glucose levels and also disrupted glucose homeostasis by depleting liver glycogen content and increasing the gluconeogenetic enzyme activities in diabetic rats. Experimentally induced diabetes was also associated with alterations in antioxidant enzymes in liver and kidney. MCP markedly enhanced lipid peroxidation in kidney and altered the enzymatic antioxidant defense mechanisms in both liver and kidney of diabetic rats. Collectively our data provides evidence that MCP has the propensity to augment the oxidative stress and further disrupt glucose homeostasis in diabetic rats.

Evidence of neuroprotective effects of saffron and crocin in a Drosophila model of parkinsonism

Evidence suggests that saffron and its major bioactives exhibit significant neuromodulatory effects in various animal models. However, specific data related to their efficacy to attenuate oxidative stress and neurotoxicity in animal models of Parkinsons disease (PD) are limited. Hence, we investigated the neuroprotective efficacy of saffron methanolic extract (SME) and its active constituent, crocin (CR) employing a Drosophila model of parkinsonism. We focussed on attenuation of Rotenone (ROT)-induced locomotor phenotype, oxidative stress, mitochondrial dysfunction and neurotoxicity in this model. SME and CR-enrichment significantly reduced ROT (500μM) induced mortality, rescued the locomotor phenotype and diminished the enhanced levels of oxidative stress markers in head/body regions of flies. The reduced levels of reduced glutathione (GSH) and total thiols (TSH) resulting from ROT exposure were significantly restored with concomitant enhancement of the antioxidant enzymes activities. Further, ROT-induced mitochondrial dysfunctions (MTT reduction, activities of SDH and NADH-Cyt C reductase (complexes I-III) enzymes) were markedly attenuated by SME/CR enrichment. While ROT elevated the activity of acetylcholinesterase (AChE) in head/body regions, both the treatments caused marked diminution of AChE activity and restored the dopamine levels suggesting their effectiveness to mitigate cholinergic function. Interestingly, SME/CR enrichment significantly delayed the onset of locomotor deficits and extended life span of flies among ROT (50μM)-stressed flies. In a satellite study, flies provided with SME/CR prophylaxis exhibited marked resistance to an acute Paraquat (PQ) challenge as evidenced by the lower incidence of lethality and improved locomotor phenotype. Taken together, the neuroprotective effects of saffron and crocin in the fly model may be largely attributable to its antioxidant action. Based on our findings, we propose that saffron may be exploited as a supplementary therapeutic agent in PD and other oxidative stress mediated neurodegenerative conditions.

Cashew Nut ( Anacardium occidentale L.) Skin Extract as a Free Radical Scavenger

Publisher Summary This chapter provides information on the free radical scavenging activity of cashew kernel testa. Cashew kernel testa (skin) is an important by-product obtained during the processing of cashew. With an annual global consumption of over 1,000,000 tons of cashew kernel, the resultant testa is a serious option for commercial exploitation. It has been reported to be a good source of hydrolyzable tannins. The tannin content of cashew kernel testa from various varieties of cashew samples has been quantified and reported to be higher than that of almond skin testa. Cashew kernel testa from different varieties and industrial samples has also been analyzed for protein, sugar, starch, and phenols, and significant variation in the composition of testa among different released varieties and industrial samples has been reported. Cashew kernel testa exhibits significant antioxidant activity due to the presence of radical scavenging polyphenols. Various extracts of cashew kernel testa have also been analyzed for protein, carbohydrate, and fiber content. Methanol-extracted cashew kernel testa was reported to contain higher protein, carbohydrate, and crude fiber contents, compared to cashew kernel testa. Methanol extraction of cashew kernel testa also resulted in a considerable decrease in tannin content, while it improved the water absorption capacity, and the in vitro digestibility of protein decreased considerably. Tannin-stripped cashew kernel testa has protein, starch, and sugar content comparable to that of other seed testa and hence may be viewed as a probable food and animal feed additive.