A multimodal Darwinian strategy for alleviating the atherosclerosis pandemic.

The conflict between our 'primitive' genes and 'modern' lifestyle probably lies at the root of several disorders that afflict modern man. Atherosclerosis, which is relatively unknown among contemporary hunter-gatherer populations, has reached pandemic proportions in recent times. Being an evolutionary problem with several inter-related pathologies, current therapeutic strategy for treating atherosclerosis has inherent limitations. Reviewing evolution-linked risk factors suggests that there are four aspects to the etiology of atherosclerosis namely, decreased intestinal parasitism, oversensitivity of evolutionarily redundant mast cells, chronic underactivation of AMPK (cellular energy sensor) and a deficiency of vitamin D. A combination of these four causes appear to have precipitated the atherosclerosis pandemic in modern times. Man and worms co-existed symbiotically in the past. Massive de-worming campaigns could have disrupted this symbiosis, increasing nutritional availability to man (pro-obesity) at the cost of decreased immunotolerance (pro-atherogenicity). A reduction in helminth-induced chronic TH2 activation could also have enhanced TH1 polarization, eventually disrupting the reciprocal regulation of TH1/TH2 balance and resulting in atherosclerosis. The riddance of helminth infestations may have rendered mast cells immunologically redundant, making them oversensitive to inflammatory stimuli, thereby playing a pro-atherogenic role. AMPK activation exerts pleiotropic anti-atherogenic effects, such as suppression of fatty acid, cholesterol, protein synthesis, reduction of vascular smooth muscle proliferation, etc. As energy deficit is the chief stimulus for AMPK activation, the over-nourished modern man appears to be suffering from chronic underactivation of AMPK, legitimising the unrivalled supremacy of metformin, the oldest prescribed antidiabetic drug. The fact that humans evolved in the sunny tropics suggests that humans are selected for high vitamin D levels. Vitamin D deficiency is now linked to several conditions including increased risk of CV disorders, diabetes, etc. The manifold decrease in vitamin D levels in modern man justifies a need for supplementation. We therefore hypothesize that a judicious combination of mast cell stabilization, AMPK activation, vitamin D supplementation, and moderation in hygiene practices could be an evolution-based multimodal strategy for both preventing and mitigating the pandemic of atherosclerosis.

6b,11b-Dihydroxy-6b,11b-dihydro-7H-indeno[1,2-b]naphtho[2,1-d]furan-7-one (DHFO), a small molecule targeting NF-κB, demonstrates therapeutic potential in immunopathogenic chronic inflammatory conditions.

6b,11b-Dihydroxy-6b,11b-dihydro-7H-indeno[1,2-b]naphtho[2,1-d]furan-7-one (DHFO), an easily synthesisable, orally bioavailable and relatively non-toxic small molecule synthesised in our lab, was previously reported to possess anti-oxidant, 5-lipoxygenase inhibitory, anti-inflammatory and peripheral analgesic activities. The present work deals with exploration of DHFO's efficacy in immunopathogenic chronic inflammatory conditions - arthritis and allergy. In carrageenan-induced inflammatory air pouch, which resembles the arthritic synovium, DHFO effectively reduced inflammatory redness and swelling and neutrophil infiltration. In complete Freund's adjuvant-induced arthritis, DHFO significantly decreased paw oedema and nitrite levels with efficacy comparable to diclofenac. DHFO inhibited neutrophil activation (observed as decreased myeloperoxidase levels), in both the in vivo models of inflammation. Interestingly, DHFO did not ulcerate the gastrointestinal tract, while diclofenac was observed to be extremely ulcerogenic. In antigen-induced active and passive anaphylaxis (allergy) models, DHFO dose-dependently prevented mesenteric mast cell (MC) degranulation with efficacy comparable to ketotifen. DHFO also inhibited compound 48/80 (C48/80)-induced paw oedema and peritoneal MC degranulation. DHFO stabilised p815 murine MCs stimulated by C48/80 and calcium ionophore-A23187, indicating an action downstream of calcium mobilisation. DHFO's anti-allergic mechanism could be two-pronged involving (1) inhibition of IgE production and/or (2) MC stabilisation. DHFO inhibited lipopolysaccharide (LPS)-induced pro-inflammatory mediator release (ROS, NO, IL-6 levels) and COX2 expression in RAW264.7 murine macrophages. Protein expression studies confirmed DHFO's ability to reduce nuclear levels of NF-κB in LPS-stimulated macrophages. Thus, DHFO is a promising non-ulcerogenic synthetic small molecule lead for immunopathogenic chronic inflammatory conditions.

Antidiabetic effect of Ficus racemosa Linn. stem bark in high-fat diet and low-dose streptozotocin-induced type 2 diabetic rats: a mechanistic study.

The present study was designed to investigate the effects of the ethanol extract of Ficus racemosa (FRE) on biochemical parameters in type 2-like diabetes, induced by a combination of standardised high-fat diet and low-dose streptozotocin (25mgkg(-1), i.p.) in rats. To elucidate the mode of action of FRE, its effects on a battery of targets involved in glucose homeostasis was evaluated. FRE (200 and 400mgkg(-1), p.o.), in a dose-dependent manner, altered the biochemical parameters and significantly improved glucose tolerance and HDL-c levels. In different bioassays, FRE showed inhibition of PTP-1B (IC50 12.1µg/mL) and DPP-IV (42.5%). FRE exhibited 82.6% binding to PPAR-γ. Furthermore FRE exhibited stimulation of glucose uptake by skeletal muscles (hemi-diaphragm). Bergenin was quantified in bioactive-FRE by high-performance liquid chromatography (0.15%w/w). This is the first report demonstrating the effectiveness of F. racemosa stem bark in type 2 diabetes and targets involved in it.

Antidiabetic, antihyperlipidemic and antioxidant effects of the flavonoid rich fraction of Pilea microphylla (L.) in high fat diet/streptozotocin-induced diabetes in mice.

The present study describes the antidiabetic effect of the flavonoid rich fraction of Pilea microphylla (PM1). HPLC characterization of PM1 revealed the presence of polyphenols viz., chlorogenic acid, rutin, luteolin-7-O-glucoside, isorhoifolin, apigenin-7-O-glucoside, and quercetin. PM1 inhibited dipeptidyl peptidase IV (DPP-IV) in vitro with an IC(50) of 520.4±15.4 µg/ml. PM1, at doses of 300, 600 and 900 mg/kg i.p., also produced dose-dependent mean percent reductions of 9.9, 30.6 and 41.0 in glucose excursion (AUC(0-120 min)) respectively in lean mice. However, even the highest dose of PM1 did not alter normoglycemic condition. PM1 at dose of 100 mg/kg/day, i.p. for 28 days produced significant (p<0.05) reduction in body weight, plasma glucose (PG), triglycerides (TG) and total cholesterol (TC) content in high-fat streptozotocin-induced diabetic mice. PM1 also improved oral glucose tolerance significantly (p<0.05) with mean percentage reduction of 48.0% in glucose excursion (AUC(0-120 min)) and significantly (p<0.05) enhanced the endogenous antioxidant status in mice liver compared to diabetic control. PM1 preserved islet architecture and prevented hypertrophy of hepatocytes as evident from the histopathology of pancreas and liver. PM1 did not show any detectable hematological toxicity at therapeutic doses. In conclusion, PM1 exhibits antidiabetic effect possibly by inhibiting DPP-IV and improving antioxidant levels in high fat diet/streptozotocin (HFD/STZ) diabetic mice.

Polyphenolic fraction of Pilea microphylla (L.) protects Chinese hamster lung fibroblasts against γ-radiation-induced cytotoxicity and genotoxicity.

Present study was designed to compare cytoprotective and antigenotoxic activity of the polyphenolic fraction of Pilea microphylla (PM1) with that of its active polyphenolic constituents against γ-radiation in V79 cells. PM1 was standardized with respect to the polyphenols present by RP-HPLC. It was evaluated for its free radical scavenging potential using Fenton reaction-induced DNA damage and lipid peroxidation. Further, PM1 was subjected against γ-radiation-induced cytotoxicity and genotoxicity in V79 cells. PM1 significantly reduced free radical-mediated calf thymus DNA damage and lipid peroxidation. Among the concentrations tested (12.5, 25 and 50 µg/ml) for radioprotection, PM1 at 25 µg/ml exhibited maximum protection. Further, when compared with constituent polyphenols viz., rutin, quercetin and chlorogenic acid (concentrations equivalent to that present in PM1-25 µg/ml), a combination of polyphenols was found most effective in preventing γ-radiation-induced cytotoxicity and genotoxicity. To conclude, radioprotection is possibly a synergistic effect of the phytochemicals present in the herbal extract, rather than any single component.

5'-adenosine monophosphate-activated protein kinase and the metabolic syndrome.

Lifestyle changes such as physical inactivity combined with calorie-rich, low-fibre diets have triggered an explosive surge in metabolic syndrome, outlined as a cluster of heart attack risk factors such as insulin resistance, raised fasting plasma glucose, abdominal obesity, high cholesterol and high blood pressure. By acting as a master-switch of energy homeostasis and associated pathophysiological phenomena, 5'-adenosine monophosphate-activated protein kinase (AMPK) appears to orchestrate the adaptive physiology of energy deficit, suggesting that the sedentary modern human could be suffering from chronic suboptimal AMPK activation. Addressing individual targets with potent ligands with high specificity may be inappropriate (it has not yielded any molecule superior to the sixty year old metformin) because this strategy cannot address a cluster of interrelated pathologies. However, spices, dietary supplements and nutraceuticals attenuate the multiple symptoms of metabolic syndrome in a collective and perhaps more holistic fashion with fewer adverse events. Natural selection could have favoured races that developed a taste for spices and dietary supplements, most of which are not only antioxidants but also activators of AMPK. The review will outline the various biochemical mechanisms and pathophysiological consequences of AMPK activation involving the cluster of symptoms that embrace metabolic syndrome and beyond. Recent advances that integrate energy homeostasis with a number of overarching metabolic pathways and physiological phenomena, including inflammatory conditions, cell growth and development, malignancy, life span, and even extending into environmental millieu, as in obesity mediated by gut microflora and others will also be outlined.

Chromium (D-phenylalanine)3 alleviates high fat-induced insulin resistance and lipid abnormalities.

High-fat diet has been implicated as a major cause of insulin resistance and dyslipidemia. The objective of this study was to evaluate the impact of dietary-supplementation of chromium (D-phenylalanine)(3) [Cr(D-Phe)(3)] on glucose and insulin tolerance in high-fat diet fed mice. C57BL/6-mice were randomly assigned to orally receive vehicle or Cr(D-Phe)(3) (45 µg of elemental chromium/kg/day) for 8-weeks. High-fat-fed mice exhibited impaired whole-body-glucose and -insulin tolerance and elevated serum triglyceride levels compared to normal chow-fed mice. Insulin-stimulated glucose up-take in the gastrocnemius muscles, assessed as 2-[(3)H-deoxyglucose] incorporation was markedly diminished in high-fat fed mice compared to control mice. Treatment with chromium reconciled the high-fat diet-induced alterations in carbohydrate and lipid metabolism. Treatment of cultured, differentiated myotubes with palmitic acid evoked insulin resistance as evidenced by lower levels of insulin-stimulated Akt-phosphorylation, elevated JNK-phosphorylation, (assessed by Western blotting), attenuation of phosphoinositol-3-kinase activity (determined in the insulin-receptor substrate-1-immunoprecipitates by measuring the extent of phosphorylation of phosphatidylinositol by γ-(32)P-ATP), and impairment in cellular glucose up-take, all of which were inhibited by Cr(d-Phe)(3). These results suggest a beneficial effect of chromium-supplementation in insulin resistant conditions. It is likely that these effects of chromium may be mediated by augmenting downstream insulin signaling.

Antidiabetic effect of Dodonaea viscosa aerial parts in high fat diet and low dose streptozotocin-induced type 2 diabetic rats: a mechanistic approach.

CONTEXT: High fat diet (HFD) and low-dose streptozotocin (STZ) is an ideal model for type 2 diabetes mellitus (T2DM) that would closely reflect the natural history and metabolic characteristics of human T2DM and is also suitable for pharmacological screening. OBJECTIVE: The present study was designed to investigate the effect of the water extract (DVW) and the polar fraction of ethanol extract (DVE-4) of Dodonaea viscosa (L). Jacq. (Sapindaceae) on biochemical parameters in type 2 diabetes induced by a standardized HFD and low dose streptozotocin (25 mg/kg) in rats. Further, to elucidate the mode of action we evaluated its effects on a battery of targets involved in glucose homeostasis (in vitro studies). MATERIALS AND METHODS: Different doses of DVW and DVE-4 were administered once daily for two weeks to HFD + STZ diabetic rats. Quantification of biomarker quercetin was done using HPLC. RESULTS AND DISCUSSION: Both DVW and DVE-4 dose-dependently reduced blood glucose, serum insulin, homeostatic model assessment (HOMA), lipid profiles, and significantly improved glucose tolerance and HDL-c levels. In addition, the extract and fraction also decreased oxidative stress by improving endogenous antioxidants. In different, bioassays, DVW and DVE-4 showed inhibition of PTP-1B and at a concentration of 10 µg/mL showed 60 and 54.2% binding to PPARγ, respectively. Both extract/fraction exhibited stimulation of glucose uptake by skeletal muscles. CONCLUSION: Taken together, these results suggest that DVW and DVE-4 inhibits HFD + STZ-induced insulin resistance, lipid abnormalities and oxidative stress indicating that these effects may be mediated by interacting with multiple targets operating in diabetes mellitus.

Antidiabetic effect of Dodonaea viscosa (L). Lacq. aerial parts in high fructose-fed insulin resistant rats: a mechanism based study.

To study the effect and mode of action of water extract (DVW) and polar fraction of ethanol extract (DVE-4) of D. viscosa in high-fructose diet induced insulin resistance in male Wistar rats. D. viscosa's effects were evaluated on a battery of targets involved in glucose homeostasis (in vitro studies). Rats were rendered insulin resistant by feeding 66% (w/w) fructose and 1.1% (v/w) coconut oil mixed with normal pellet diet (NPD) for six weeks. DVW and DVE4 at different doses were administered simultaneously. At the end of the study, blood glucose, oral glucose tolerance test, lipid profile and insulin were estimated and homeostatic model assessment (HOMA) levels were calculated. In addition, enzymatic and nonenzymatic liver antioxidant levels were also estimated. Quantification of biomarker quercetin was done using HPLC. Fructose diet with DVW, DVE-4 significantly reduced blood glucose, serum insulin, HOMA, lipid profiles and significantly improved glucose tolerance and HDL-c levels. In addition, these extract and fraction also decreased oxidative stress by improving endogenous antioxidants. In different bioassays, DVW and DVE-4 inhibited protein tyrosine phosphatase-1B with IC50 65.8 and 54.9 microg/ml respectively and showed partial inhibition of dipeptidyl peptidase-IV. Moreover, DVW and DVE-4, at 10 microg/ml showed 60 and 54.2% binding to peroxisome proliferator-activated receptor-gamma. Further, 2.1% (w/w) of quercetin was quantified in bioactive-DVE-4 using HPLC method. The results provide pharmacological evidence of D. viscosa in treatment of prediabetic conditions and these effects may be mediated by interacting with multiple targets operating in diabetes mellitus.

Ficus racemosa Stem Bark Extract: A Potent Antioxidant and a Probable Natural Radioprotector.

Ethanol extract (FRE) and water extract (FRW) of Ficus racemosa (family: Moraceae) were subjected to free radical scavenging both by steady state and time resolved methods such as nanosecond pulse radiolysis and stopped-flow spectrophotometric analyses. FRE exhibited significantly higher steady state antioxidant activity than FRW. FRE exhibited concentration dependent DPPH, ABTS(*-), hydroxyl radical and superoxide radical scavenging and inhibition of lipid peroxidation with IC(50) comparable with tested standard compounds. In vitro radioprotective potential of FRE was studied using micronucleus assay in irradiated Chinese hamster lung fibroblast cells (V79). Pretreatment with different doses of FRE 1h prior to 2 Gy gamma-radiation resulted in a significant (P < 0.001) decrease in the percentage of micronucleated binuclear V79 cells. Maximum radioprotection was observed at 20 mug/ml of FRE. The radioprotection was found to be significant (P < 0.01) when cells were treated with optimum dose of FRE (20 mug/ml) 1 h prior to 0.5, 1, 2, 3 and 4 Gy gamma-irradiation compared to the respective radiation controls. The cytokinesis-block proliferative index indicated that FRE does not alter radiation induced cell cycle delay. Based on all these results we conclude that the ethanol extract of F. racemosa acts as a potent antioxidant and a probable radioprotector.

Radioprotective effect of sulfasalazine on mouse bone marrow chromosomes.

Sulfasalazine (SAZ), a prescribed drug for inflammatory bowel disease, is a potent scavenger of reactive oxygen species. The present study was undertaken to ascertain its ability to protect against gamma radiation-induced damage. Acute toxicity of the drug was studied taking 24-h, 72-h and 30-day mortality after a single intraperitoneal injection of 400-1200 mg/kg body weight (b.wt.) of the drug. The drug LD(50) for 24- and 72-h/30-day survival were found to be 933 and 676 mg/kg b.wt., respectively. The optimum time of drug administration and drug dose-dependent effect on in vivo radiation protection of bone marrow chromosomes was studied in mice. Injection of 30-180 mg/kg SAZ 30 min before gamma irradiation (RT) with 4 Gy produced a significant dose-dependent reduction in the RT-induced percent aberrant metaphases and in the frequency of micronucleated erythrocytes at 24 h after exposure, with a corresponding decrease in the different types of aberrations. The optimum dose for protection without drug toxicity was 120 mg/kg b.wt. At this dose, SAZ produced >60% reduction in the RT-induced percent aberrant metaphases and micronucleated erythrocytes. SAZ also produced a significant increase in the ratio of polychromatic erythrocytes to normochromatic erythrocytes from that of irradiated control. Injection of 120 mg/kg of the drug 60 or 30 min before or within 15 min after 4 Gy whole-body RT resulted in a significant decrease in the percent of aberrant metaphases and in the frequency of micronucleated erythrocytes at 24 h post-irradiation; the maximum effect was seen when the drug was administered 30 min before irradiation. These results show that SAZ protect mice against RT-induced chromosomal damage and cell cycle progression delay. SAZ also protected plasmid DNA (pGEM-7Zf) against Fenton's reactant-induced breaks, suggesting free radical scavenging as one of the possible mechanism for radiation protection.

Antioxidant and radioprotective effect of the active fraction of Pilea microphylla (L.) ethanolic extract.

The ethanolic extract of Pilea microphylla (L.) was defatted, successively fractionated with acetone and the residue so obtained was found to be most potent when subjected to detailed free radical scavenging and in vivo radioprotection studies. The most active fraction reacts with free radicals, such as DPPH (50 microM), ABTS(.)(-) (100 microM) and (.)OH (generated by Fenton reaction) with IC(50) value of 23.15 microg/ml, 3.0 microg/ml and 310 microg/ml, respectively. The most active fraction inhibited iron-induced lipid peroxidation in phosphatidyl choline liposomes with an IC(50) of 13.74 microg/ml. The kinetics of scavenging of DPPH and ABTS(.)(-) radicals were followed at different concentrations of the fraction by employing stopped-flow studies. The observed first order decay rate constants at 200 microg/ml and 50 microg/ml of fraction with DPPH (50 microM) and ABTS(.)(-) (50 microM) were found to be 0.4s(-1) and 2.1s(-1), respectively. The fraction when screened for in vivo radioprotection in Swiss albino mice showed 80% protection at a dose of 900 mg/kg and with a DRF of about 1.12. The fraction was also found to protect livers of irradiated mice from depletion of endogenous antioxidant enzymes like glutathione, GST, SOD, catalase and thiols. The fraction also protected the villi height, increased the number of crypt cells while offering general protection to the intestine from acute radiation effects. The fraction also protected the hematopoietic system as assessed by endogenous spleen colony assay, contributing to the overall radioprotective ability.

Evaluation and optimization of radioprotective activity of Coronopus didymus Linn. in gamma-irradiated mice.

PURPOSE: To evaluate and optimize the radioprotective ability of the most potent fraction of an aqueous extract of Coronopus didymus in whole body gamma-irradiated Swiss albino mice and to evaluate the antioxidant status and lipid peroxidation of the livers of the surviving mice. To correlate the free radical scavenging studies with in vivo radioprotection ability. MATERIALS AND METHODS: Swiss albino mice were treated with either vehicle or the different doses of extract/fraction suspension by an i.p. route, 30 min before exposure to 10 Gy gamma-irradiation and the animals were monitored twice daily for any signs of radiation toxicity and mortality. Radiation dose response (7-11 Gy), optimization of route, time of drug administration and evaluation of dose response factor (DRF) at the best dose of the fraction was studied. Endogenous antioxidant status and lipid peroxidation of the livers of the mice surviving on the 31st day was evaluated by using spectrophotometric methods. RESULTS: The most active free radical scavenging fraction (CDF1) as assessed by competition kinetic studies using pulse radiolysis showed maximum in vivo radioprotection of 70% at a dose of 400 mg/kg body weight (bw) compared to corresponding 10 Gy irradiated control. Optimum radioprotection was observed upon i.p. administration, 30 min prior to 10 Gy irradiation and DRF at a dose of 400 mg/kg bw for 30 day survival was found to be 1.07. The levels of endogenous antioxidant enzymes and lipid peroxidation in the CDF1 treated surviving mice were found to reverse back to their normal levels. CONCLUSIONS: The optimum dose, time and route of drug administration for maximum radioprotection by CDF1 were determined. The reversal of the levels of endogenous antioxidant enzymes and lipid peroxidation indicates reduced oxidative stress in CDF1 treated surviving mice.

Identification and evaluation of antioxidant, analgesic/anti-inflammatory activity of the most active ninhydrin-phenol adducts synthesized.

Treatment of phenols with ninhydrin in acidic medium afforded 2-hydroxy-2-(ortho-hydroxy-phenyl/naphthyl)-1,3-dioxoindanes, which being unstable were isolated in their hemiketal forms. These synthesized compounds were subjected to TLC screening for radical scavenging and in vitro lipoxgenase and cycloxygenase enzyme inhibition assays. The best compound was identified and studied in detail for steady-state and time-resolved free radical kinetics, viz., DPPH, ABTS(-), *OH and rate constants for these reactions were evaluated. The best compound was also subjected to in vivo anti-inflammatory and analgesic activities in which the compound showed good promise for further structural optimization.

Bioactivity-guided fractionation of Coronopus didymus: A free radical scavenging perspective.

The whole plant aqueous extract of Coronopus didymus Linn. was fractionated on the basis of polarity and resulting fractions were evaluated for free radical scavenging ability. The most non-polar fraction (CDF1) was found to be more active than other fractions in scavenging DPPH, ABTS(-), nitric oxide and hydroxyl radicals in steady-state conditions. Stop-flow spectrometric studies showed 58.13% inhibition of 100 microM DPPH at a concentration of 150 microg/ml of CDF1 in 1000 s and 32.31% scavenging of 960 microM ABTS(-) at a concentration of 300 microg/ml of CDF1 in 100 s. The reaction of CDF1 with hydroxyl radicals produced by pulse radiolysis showed a transient spectrum with absorption peaks at 320, 390 and 400 nm, indicating the presence of flavonoids/related components. Competition kinetics with potassium thiocyanate against scavenging of hydroxyl radicals showed a reactivity of 0.1326 against thiocyanate. CDF1 also protected against Fenton reagent-induced calf thymus DNA damage at a concentration of 400 mg/ml indicating it to be the most potent fraction.

Antiinflammatory and antiulcer activities of phytic acid in rats.

Maximum antiinflammatory activity of phytic acid (PA) was seen at an oral dose of 150 mg/kg in the carrageenan induced rat paw edema model. Although PA showed ability to prevent denaturation of proteins, it showed less antiinflammatory activity than ibuprofen. Ability of PA to bring down thermal denaturation of proteins might be a contributing factor in the mechanism of action against inflammation. PA, at all the doses tested, showed significant protection from ulcers induced by ibuprofen, ethanol and cold stress, with a maximum activity at 150 mg/kg. There was a significant increase in gastric tissue malondialdehyde levels in ethanol treated rats but these levels decreased following PA pretreatment. Moreover, pretreatment with PA significantly inhibited various effects of ethanol on gastric mucosa, such as, reduction in the concentration of nonprotein sulfhydryl groups, necrosis, erosions, congestion and hemorrhage. These results suggested that gastro-protective effect of PA could be mediated by its antioxidant activity and cytoprotection of gastric mucosa.

Effect of O-glycosilation on the antioxidant activity and free radical reactions of a plant flavonoid, chrysoeriol.

Chrysoeriol and its glycoside (chrysoeriol-6-O-acetyl-4'-beta-D-glucoside) are two natural flavonoids extracted from the tropical plant Coronopus didymus. The aqueous solutions of both the flavonoids were tested for their ability to inhibit lipid peroxidation induced by gamma-radiation, Fe (III) and Fe (II). In all these assays chrysoeriol showed better protecting effect than the glycoside. The compounds were also found to inhibit enzymatically produced superoxide anion by xanthine/xanthine oxidase system; here the glycoside is more effective than the aglycone. The rate constants for the reaction of the compounds with superoxide anion determined by using stopped-flow spectrometer were found to be nearly same. Chrysoeriol glycoside reacts with DPPH radicals at millimolar concentration, but the aglycone showed no reaction. Using nanosecond pulse radiolysis technique, reactions of these compounds with hydroxyl, azide, haloperoxyl radicals and hydrated electron were studied. The bimolecular rate constants for these reactions and the transient spectra of the one-electron oxidized species indicated that the site of oxidation for the two compounds is different. Reaction of hydrated electron with the two compounds was carried out at pH 7, where similar reactivity was observed with both the compounds. Based on all these studies it is concluded that chrysoeriol exhibits potent antioxidant activity. O-glycosylation of chrysoeriol decreases its ability to inhibit lipid peroxidation and reaction with peroxyl radicals. However the glycoside is a more efficient scavenger of DPPH radicals and a better inhibitor of xanthine/xanthine oxidase than the aglycone.

Radiation protection by the ocimum flavonoids orientin and vicenin: mechanisms of action.

In previous studies, flavonoids, orientin and vicenin, that were isolated from the leaf extract of Ocimum sanctum, were found to protect mice against radiation injury. Several flavonoids are known to be good antioxidants. Therefore, the effect of orientin and vicenin on radiation-induced lipid peroxidation in vivo and their antioxidant activity in vitro were studied. Adult mice were injected intraperitoneally with 50 microgram/kg of orientin or vicenin and exposed whole-body to 3 Gy of gamma radiation. Lipid peroxidation was measured in the liver 15 min to 8 h postirradiation. The antioxidant activity of orientin/vicenin (10-500 microM) was studied by measuring inhibition of hydroxyl radicals generated by the Fenton reaction (Fe(3+)-EDTA-ascorbic acid-H(2)O(2)) in vitro. The compounds were also tested for possible pro-oxidant and iron chelation activities at the above concentrations in the in vitro system. Orientin and vicenin provided almost equal protection against radiation-induced lipid peroxidation in mouse liver. Both compounds showed a significantly greater free radical-inhibiting activity in vitro than DMSO. Neither orientin nor vicenin showed any pro-oxidant activity at the concentrations tested. Both compounds inhibited free radical formation in the absence of EDTA. Free radical scavenging appears to be a likely mechanism of radiation protection by these flavonoids.