Bioassay-Guided Isolation and Structural Elucidation of Antidiabetic Principle of Methanol Leaf Extract of Newbouldia laevis (P.Beauv)

Abstract

NLE (Newbouldia laevis (P.Beauv)) is used in folk medicine to treat diabetes. The aim of the study was to isolate and characterize the active compound responsible for the antidiabetic activity.This was carried out using standard in vivo and in vitro models in rats. The antidiabetic activities were evaluated using alloxan-induced diabetes in male and female albino rats after an over night fast and various doses of NLE and glibenclamide, the reference drug 2.0 mg/kg. Bioassay-guided isolation/fractionation techniques were used to isolate the active compound. Characterization of the active compound was carried out including molecular and structural elucidation using NMR (nuclear magnetic resonance) and Gas-Chromatography Mass spectroscopy. The extract caused 60.2% reduction in the FBS (fasting blood sugar) of diabetic rats. Bioassay-guided fractionation of NLE yielded ten (10) fractions with F9 (fraction nine) as the active fraction, which caused 66.0% reduction of FBS in alloxan-induced diabetic rats. Further purification using preparative TLC (thin layer chromatography), gave sub-fraction 9.2 as the active compound. Sub-fraction 9.2 reduced the FBS by 61.4%. The characterization of F9:2 using nuclear magnetic resonance and MS (mass spectroscopy) confirmed it to be a polyunsaturated fatty acid with a molecular weight of 358.56 g.

Antidiabetic and Hypolipidemic Effects of Methanol Leaf Extract of Newbouldia laevis in Alloxan Induced Diabetic Rats

“…The NLE at the highest dose (250.0 mg/kg) caused 60.2% decreases in FBS at 24 h, when compared to the negative control rats as against the reference drug glibenclamide (2 mg/kg) which caused 51.5% decrease under the same condition (Table 1). The dose and time-dependent decrease of FBS in diabetic rats by Newbouldia laevis has been reported by other workers also Tanko et al [30]; Owolabi et al [31]; Kolawole et al [32]; Bosha et al [22]; Bosha et al [24]; Bosha et al [33].…”

“…The time of maximum effect was at the 24th h in the dose response study. The dose and time-dependent reductions in the FBS levels also manifested in the subacute study of 21 days oral administration of NLE Bosha et al [29]. The NLE at the highest dose (250.0 mg/kg) caused 60.2% decreases in FBS at 24 h, when compared to the negative control rats as against the reference drug glibenclamide (2 mg/kg) which caused 51.5% decrease under the same condition (Table 1).…”

“…The effect of NLE on alloxan-induced diabetes was carried out using diabetic rats divided into 5 groups of 8 rats each. Any rat with fasting blood sugar ≥ 7.0 mMol/l was considered diabetic using Accu-check Advantage II® (Roche Diagnostics, New Jersey USA) Bosha et al [24].…”

“…Since time immemorial patients with type 2 diabetes have been treated orally with a variety of plant extracts in folk medicine Ivorra et al [20]; Andrede-cetto & Heinrich [21]. One of such plants is Newbouldia laevis Bosha et al [22]. The present hypoglycaemic agents used in the treatment of DM have shown reduced efficacy due to drug resistance and have many serious side effects.…”