The Antioxidant and Antihyperglycemic Activities of Bottlebrush Plant (Callistemon lanceolatus) Stem Extracts

Abstract

Background: Diabetes mellitus, a metabolic disease, is a major health concern today throughout the world. Callistemon lanceolatus (Myrtaceae), commonly known as bottlebrush, has been used by Indian tribal communities for the treatment of many diseases. The purpose of this study was to explore antioxidant and antihyperglycemic potential of methanolic and aqueous extracts of the stem of C. lanceolatus in vitro and in vivo. Methods: Phytoconstituents of C. lanceolatus stem were extracted in methanol and water sequentially followed by phytochemical analysis. The in vitro antioxidant potential of aqueous and methanolic extracts was assessed by metal ion chelating, free radical scavenging, and reducing power assays. The in vivo antihyperglycemic activity of the oral methanolic extract was studied in alloxan-induced diabetic rats. Bodyweight and blood glucose were monitored regularly. After the treatment period, serum was examined for total cholesterol, triglycerides, high-density lipoprotein (HDL), bilirubin, creatinine, urea, glutamate pyruvate transaminase (SGPT), glutamate oxaloacetate transaminase (SGOT), and alkaline phosphatase (ALP). Results: Methanolic extract exhibited superior antioxidant activity to aqueous extract. A marked increase in levels of serum markers, viz., glucose, triglycerides, total cholesterol, bilirubin, urea, creatinine, SGOT, SGPT, and ALP along with a reduction in HDL was observed in diabetic rats. Methanol extract treatment for 28 days accounted for a decrease in blood glucose and other metabolic markers accompanied by an improvement in body weight and HDL level in hyperglycemic rats. Conclusions: The present study suggests that C. lanceolatus methanolic stem extract possesses antioxidant and antihyperglycemic activities and has potential as a therapeutic agent in diabetes.

Keywords: Callistemon lanceolatus; antidiabetic; antioxidant; hyperglycemia; rats; serum markers.

Figure 1

Images of C. lanceolatus whole tree (A) and flowers (B).

Figure 2

Free radical scavenging activity of methanolic (Meth) and aqueous (AQ) extracts of C. lanceolatus stem. Radical scavenging activity was determined at various concentrations of both extracts (40–100 µg/mL). Butylated hydroxyl anisole (BHA) was used as a control. The results are expressed as a mean ± SD of three replicates. * p ˂ 0.05 compared to BHA.

Figure 3

Reducing power of C. lanceolatus stem methanolic (Meth) and aqueous (AQ) extracts. The reducing power was measured at different extract concentrations (200–1000 µg. Vitamin C was used for comparison. The results are expressed as a mean ± SD of three replicates. ** p < 0.01 compared to vitamin C.

Figure 4

Metal ion chelation activity of C. lanceolatus stem methanolic (Meth) and aqueous (AQ) extracts. The chelating activity of extracts was measured in concentration range of 100–400 µg/mL. Propyl gallate was used for comparison. The results are expressed as a mean ± SD of three replicates. *** p ˂ 0.001 compared to propyl gallate.

Figure 5

Effect of C. lanceolatus methanolic extract on body weight (A) and blood glucose level (B) of rats. The results are expressed as a mean ± SD (n = 5). Group 1: Normal control; Group 2: Diabetic control; Group 3: Diabetic rats treated with glibenclamide; Group 4: Diabetic rats fed with C. lanceolatus extract (200 mg/kg); Group 5: Diabetic rats fed with C. lanceolatus extract (400 mg/kg); Group 6: C. lanceolatus extract (400 mg/kg) control. ⁺ p < 0.01 compared to normal control. * p < 0.05, ** p < 0.01 and *** p < 0.001 compared to the diabetic control.

Figure 6

Effect of C. lanceolatus methanolic extract on serum total cholesterol (A) and high-density lipoprotein (HDL) (B) levels. The results are expressed as a mean ± SD (n = 5). Group 1: Normal control; Group 2: Diabetic control; Group 3: Diabetic rats treated by glibenclamide; Group 4: Diabetic rats fed with C. lanceolatus extract (200 mg/kg); Group 5: Diabetic rats fed with C. lanceolatus extract (400 mg/kg); Group 6: C. lanceolatus extract (400 mg/kg) control. ⁺ p < 0.01 and ⁺⁺ p < 0.001 compared to normal control. * p < 0.05 and ** p < 0.01 compared to the diabetic control.

Figure 7

Effect of C. lanceolatus methanolic extract on serum triglyceride (A) and bilirubin (B) levels. The results are expressed as a mean ± SD (n = 5). Group 1: Normal control; Group 2: Diabetic control; Group 3: Diabetic rats treated with glibenclamide; Group 4: Diabetic rats fed with C. lanceolatus extract (200 mg/kg); Group 5: Diabetic rats fed with C. lanceolatus extract (400 mg/kg); Group 6: C. lanceolatus extract (400 mg/kg) control. ⁺ p < 0.001 compared to normal control. * p < 0.05, ** p < 0.01 and *** p < 0.001 compared to the diabetic control.

Figure 8

Effect of C. lanceolatus methanolic extract on serum glutamate oxaloacetate transaminase (SGOT) (A), glutamate pyruvate transaminase (SGPT) (B) and alkaline phosphatase (ALP) (C) levels. The results are expressed as a mean ± SD (n = 5). Group 1: Normal control; Group 2: Diabetic control; Group 3: Diabetic rats treated by glibenclamide; Group 4: Diabetic rats fed with C. lanceolatus extract (200 mg/kg); Group 5: Diabetic rats fed with C. lanceolatus extract (400 mg/kg); Group 6: C. lanceolatus extract (400 mg/kg) control. ⁺ p < 0.001 compared to normal control. * p < 0.05, ** p < 0.01 and *** p < 0.001 compared to the diabetic control.

Figure 9

Effect of C. lanceolatus methanolic extract on serum creatinine (A) and blood urea nitrogen (B) levels. The results are expressed as a mean ± SD (n = 5). Group 1: Normal control; Group 2: Diabetic control; Group 3: Diabetic rats treated with glibenclamide; Group 4: Diabetic rats fed with C. lanceolatus extract (200 mg/kg); Group 5: Diabetic rats fed with C. lanceolatus extract (400 mg/kg); Group 6: C. lanceolatus methanolic extract (400 mg/kg) control. ⁺ p < 0.001 compared to normal control. * p < 0.05, ** p < 0.01 and *** p < 0.001 compared to the diabetic control.