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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.

Argyreia speciosa (sweet) (Burm.f.) Boj. is an Ayurvedic rasayana plant used as an adaptogen. The present study reports the investigations done on the adaptogenic property of ethanol (EtAS; 100 and 200 mg/kg; po), ethyl acetate (EAAS; 100 and 200 mg/kg; po) fraction and flavanoids such as quercetin and kaempferol (25 mg/kg; po) of the root. Immobilization induced acute stress (AS; 3 days) and chronic stress (CS; 7 days) and swimming induced stress models were used to screen the anti-stress effect of the plant fractions and isolated flavanoids. The tested doses of EtAS and isolated flavanoids were able to produce significant effects in normalizing altered serum biochemical parameters and the severity of ulcer in both AS and CS models. Higher dose of EtAS, quercetin and kaempferol (25 mg/kg; po) were found to be significant in restoring the hypertrophy of adrenal gland and atrophy of spleen and thymus gland only in CS model. Greater swimming time was noted in the mice pretreated with tested doses of flavanoids and EtAS. In addition, levels of adrenal ascorbic acid and cortisol were restored compared to stress control group. EtAS exhibited significant scavenging effect of DPPH, hydroxyl radical and LPO. Thus, EtAS, quercetin and kaempferol are capable of increasing the capacity to tolerate non-specific stress in experimental animals, as evident from restoration of large number of parameters in the stress models studied. Bioactivity of EtAS may be due to the synergetic action of isolated flavanoids. Improvement in stress markers may be due its prolong effect of resistance to stress and partly due to free radical scavenging activity.