Abstract:
Diabetes mellitus (DM), a metabolic disease, is becoming more prevalent globally. Solanum
macrocarpon (Linn.) is traditionally used in the treatment of DM but there is paucity of
information on the scientific evaluation of its diabetic activity. The aim of this study was to
evaluate the antidiabetic activity of the methanol leaf extract of Solanum macrocarpon in
streptozotocin-induced diabetic male Wistar rats.
Solanum macrocarpon leaves were air-dried, pulverised, extracted with methanol (SME) and
then fractionated into n-hexane, chloroform, ethyl acetate (EA), n-butanol and methanol.
Phytochemical screening and antioxidant [Total flavonoids content, 2,2 diphenyl-1-
picryhydrazl reduction (DPPH), Total Antioxidant Capacity (TAC), and Reducing Power
(RP)] activity were evaluated in SME and its fractions while α-amylase inhibition (α-AI), α-
glucosidase inhibition (α-GI), Metal Chelating (MC) and Nitric Oxide (NO) scavenging
activities were evaluated in SME only by spectrophotometry. Diabetes mellitus was induced
using streptozotocin (50mg/kg i.p.) and animals with fasting blood glucose (FBG) ≥
250mg/dL were considered as being diabetic. Twenty-four rats (139-146g) were grouped
(n=6): Groups 1 (control), 2 (diabetic control), 3 (diabetic rats + EA fraction, 300mg/kg) and
4 (diabetic rats + Glibenclamide, 1mg/kg) and treated orally for 28 days. The animals were
sacrificed and FBG, Oral Glucose Tolerance Test (OGGT), glycated haemoglobin, urea,
creatinine, Alkaline Phosphatase (ALP), Glutathione Peroxidase (GPx), Aspartate
Transaminase (AST), Superoxide Dismutase (SOD), and levels of GSH and malondialdehyde
were assessed by spectrophotometry. Histological examinations of the liver and kidney were
performed using standard procedures. Chemical profiling of EA fraction was determined
using Fourier Transformed Infrared (FT-IR) spectroscopy and GC-MS. Data were analysed
using descriptive statistics and ANOVA at α0.05.
The presence of alkaloids, saponins, phenols, flavonoids, steroids, and terpenoids were
detected in SME and its fractions. Antidiabetic activity analysis showed that SME exhibited
α-AI (59.9%) and α-GI (41.7%) activities. The SME also exhibited NO scavenging (77.4%)
and MC (48.8%) activities as well as TAC (0.021mg/gAAE). The EA fraction possessed the
highest total flavonoids (0.23mg/gQUE), TAC (0.05 mg AAE/g) and DPPH (92.6%)
scavenging activity. In diabetic rats+EA fraction, body weight (36.5%) increased, while
decrease in FBG (60%), OGTT and glycated haemoglobin decreased relative to control was
observed. Creatinine (28.2%), urea (18.5%), AST (16.3%), ALT (20%), and ALP (31.1%)
were reduced in diabetic rats+EA fraction relative to diabetic controls. Activities of SOD
(0.104 vs 0.128 units/mg protein), CAT (0.121vs 0.155units/mg protein), and GPx (8.59 vs
10.17 units/mg protein) as well as GSH level (2.66 vs 3.64 µmol/L) elevated in the diabetic
rats+EA fraction compared with diabetic. Malondialdheyde levels (26.7%) reduced relative to
diabetic control. The diabetic rats+EA fraction showed reversal of hepatic and renal periportal
inflammatory infiltration observed in the diabetic controls. Presence of hydroxy groups in EA
fraction (3500 cm-1) was revealed, and squalene intermediates as the most abundant
compounds.
The ethyl acetate fraction of Solanum macrocarpon ameliorated hyperglycaemia and
protected renal and hepatic tissues through antioxidant mediated mechanisms in
streptozotocin-induced diabetic rats.
