Antihyperglycemic Studies on the Leaf Extract and Active Fractions of <i>Newbouldia laevis</i> (Bignoniaceae)

Abstract

Optimal control of chronic hyperglycemia prevents both micro and macro vascular complications-a leading cause of morbidity and mortality in diabetic subjects. This study was undertaken to give credence to the traditional use of Newbouldia laevis leaves in the treatment of diabetes mellitus (DM). Dichloromethane-methanol (1:1) extract (DME) of N. laevis leaves was prepared by cold maceration. Separation of DME into column chromatographic fractions yielded the n-hexane fraction (HF), ethylacetate fraction (EF) and methanol fraction (MF). The extract and fractions were evaluated for antihyperglycemic activity in alloxanized diabetic rats. The results showed that the oral administration of extract and fractions (250, 500, 1000 mg/kg) caused a significant (P < 0.5) and dose-dependent reduction in blood glucose level in diabetic rats. The hypoglycemic potency after 24 h was in the order MF (methanol fraction; 56.31%) > DME (dichloromethane/methanol extract; 36.19%) > EF (ethylacetate fraction; 20.70%) > HF (n-hexane fraction; 10.09. The methanol fraction, which showed the highest potency in oral glucose tolerance test (OGTT), was further separated into column chromatographic sub-fractions-F₁, F₂, F₃ and F₄ fractions. These sub-fractions were evaluated for antihyperglycemic activity. Sub-fractions F₁, F₂ and F₃ (1000 mg/kg) did produce significant (P > 0.05) reduction in blood glucose level after 24 h. Sub-fraction F4 (50, 100, 200 mg/kg), however caused a significant (P < 0.05) and dose-dependent reduction in blood glucose level. The reduction at 200 mg/kg dose of F 4 (74.57%) was significantly (P < 0.05) higher than that of glibenclamide (58.04%). These findings suggest that leaf extract and fractions of Newbouldia laevis possess antihyperglycemic activities and can be the basis for the folk use N. laevis in management of diabetes mellitus.

Biochemical and Haematological Effects of the Leaf Extract of &lt;i&gt;Newbouldia laevis&lt;/i&gt; in Alloxan-Induced Diabetic Rats

“…In this study, induction of diabetes with alloxan is demonstrated to be associated with a characteristic decrease in body weight. The ability of DME to protect against massive weight loss in alloxan diabetic rats seems to be due to its ability to improve glucose utilization, reduce hepato-renal dysfunction, [18] [79], improve the TAS and restore haematopoetic function. Earlier report noted a significant increase in the body weight of normal rats supplemented with N. laevis extract [49].…”

“…Recently, the antihyperglycemic activity of the leaf extract and active fractions of the plant was reported [18] and apigenin was reported to be one of the active metabolites responsible for the antihyperglycemic activity [19].…”

Anti-hyperglycemic effects of Stemonocoleus micranthus (Fabaceae) stem bark on alloxan-induced hyperglycemic rats

“…to slow the progression of this disorder, diabetes mellitus and its associated complications continue to pose a major health challenge to people (Ravi et al, 2005;Kavishankar et al, 2011). In view of this, alternative approaches are therefore urgently needed to manage it (Osigwe et al, 2015).…”

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“…Although, the aqueous leaf extract of N. laevis have been reportedly evaluated by Omonkhelin et al, and Owolabi et al, for its antihyperglycaemic activity at 100, 200 and 400 mg/kg body weight 31,36 as well as Ajah et al, and Osigwe et al, at 200 and 250, 500, 1000 mg/kg body weight 37,38 respectively in alloxan-induced hyperglycaemic rats, there is dearth of information in the open scientific literature on the possibility of antidiabetic activity of N. laevis leaf on alloxan-induced hyperglycaemia especially at the specific pharmacologic dose of 100 and 200 mg/kg body weight. Therefore, the present study was undertaken to provide information on the antihyperglycaemic effects of aqueous leaf extract of N. laevis on alloxan-induced hyperglycaemia in rats.…”