Extract of Bauhinia vahlii Shows Antihyperglycemic Activity, Reverses Oxidative Stress, and Protects against Liver Damage in Streptozotocin-induced Diabetic Rats

Abstract

Background: Several studies have affirmed the effectiveness of some Bauhinia plants as antihyperglycemic agents.

Objective: We investigated the possible effect of Bauhinia vahlii leaves extract in reducing hyperglycemia and reversing signs of organ damage associated with diabetes in streptozotocin (STZ) rat model.

Materials and methods: Both polar fraction of the B. vahlii leaves (defatted ethanolic extract [DEE]) and nonpolar fraction (n-hexane extract) were evaluated in vitro for α-glucosidase inhibition and 2,2-diphenyl-1-picrylhydrazyl radical scavenging potential. DEE was selected for further in vivo studies and was administered at two doses, i.e., 150 or 300 mg/kg to STZ-diabetic rats for 4 weeks.

Results: Only DEE exhibited in vitro antioxidant and antihyperglycemic activities and its oral administration at both dose levels resulted in significant reduction in fasting blood glucose and glycated hemoglobin. Furthermore, signs of oxidative stress as indicated by hepatic reduced glutathione, nitric oxide, and malondialdehyde levels were completely reversed. In addition, histopathological examination and measurement of serum aspartate transaminase and alanine transaminase levels showed that DEE protected the liver from signs of liver pathogenesis when compared to diabetic untreated animals and those treated with metformin. Phytochemical analysis of DEE showed high flavonoids content with quercitrin as the major constituent along with other quercetin glycosides.

Conclusion: This study strongly highlights the possible beneficial effect of B. vahlii leaves extract in relieving hyperglycemia and liver damage in STZ-diabetic rats and recommends further investigation of the value of quercetin derivatives in controlling diabetes and ameliorating liver damage associated with it.

Summary: The polar fraction of the Bauhinia vahlii leaves (defatted ethanolic extract [DEE]) exhibited both in vitro antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl scavenging assay and strong α-glucosidase inhibition while the nonpolar fraction (n-hexane extract) failed to show any activity in both assays. DEE was further investigated in streptozotocin-induced diabetic rat model where oral administration of DEE at 2 doses (150 and 300 mg/kg) for 4 weeks resulted in significant reduction in fasting blood glucose and glycated hemoglobin and reversal of oxidative stress signs as indicated by measurement of hepatic reduced glutathione, nitric oxide, and malondialdehyde levels. In addition, histopathological examination and measurement of serum aspartate transaminase and alanine transaminase levels showed that DEE protected the liver from signs of pathogenesis observed in diabetic untreated rats. Phytochemical analysis of DEE showed high flavonoid content with quercitrin as the major constituent (62.9 ± 0.18 mg/mg). Abbreviations used: ALT: Alanine transaminase, AST: Aspartate transaminase, DEE: Defatted ethanol extract, DPPH: 2,2-diphenyl-1-picrylhydrazyl, FBG: Fasting blood glucose, GAE: Gallic acid equivalent, GSH: Reduced glutathione, Hb1Ac: Glycated hemoglobin, HE: Hexane extract MDA: Malondialdehyde, QE: Quercetin equivalent, STZ: Streptozotocin, TAC: Total antioxidant capacity.

Keywords: Antihyperglycemic; Bauhinia vahlii; antioxidant; quercitrin; α-glucosidase inhibitor.

Figure 1

Biochemical parameters of hyperglycemia, oxidative stress, and liver functions as measured in five animals groups. (a) Serum levels of fasting blood glucose; (b) percentage of glycated hemoglobin, (c) serum total antioxidant capacity, (d) hepatic reduced glutathione, (e) hepatic malondialdehyde, (f) hepatic nitric oxide, (g) serum alanine transaminase and (h) serum aspartate transaminase. Biochemical parameters were measured in serum and hepatic tissue of streptozotocin-induced diabetic animal after 4 weeks of treatments. **Significantly different from the control group at P < 0.01, ^##Significantly different from the untreated diabetic group at P < 0.01, ^#Significantly different from the untreated diabetic group at P < 0.05

Figure 2

Photomicrographs of liver tissue from (a) normal group, (b) diabetic untreated, (c) diabetic + 150 mg DEE/kg, (d) diabetic + 300 DEE mg/kg, (e) diabetic + 300 mg metformin/kg. Photomicrographs of the effect of DEE of Bauhinia vahlii leaves on liver tissues in streptozotocin-induced diabetic rats cv: Central vein, h: Hepatocytes, bd: Bile ducts, n: Newly formed ductules, pv: Portal vein, m: Inflammatory cell infiltration, o: edema. DEE: Defatted ethanolic extract