An investigation of the effect of Kigelia Africana fruit fractions on diabetes bio-markers in alloxan monohydrate induced diabetes Wistar rat models
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Date
2025
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University of Namibia
Abstract
Diabetes affects 19 million people in Africa, with 60% of diabetic patients opting for
traditional therapies due to cost-effectiveness, accessibility, and perceived safety. Kigelia
africana (Bignoniaceae) is used as a traditional antidiabetic remedy, but data on the
specific phytochemicals responsible for its benefits and safety are limited. This study
investigated the antidiabetic properties of Kigelia africana fruit fractions and their effects
on diabetes markers in alloxan-induced diabetic rats. The chemical composition of the
bioactive fractions was determined, while cytotoxic and genotoxic effects of the crude
extracts were also analysed.
The antidiabetic effects of the Kigelia africana fruit extract were compared with those of
glibenclamide in 54 alloxan-induced diabetic rats. Fractions were obtained using liquidliquid and column fractionation. The effects of Kigelia fractions on lipid profile, blood
glucose, alanine aminotransferase, and creatinine levels were determined.
Histopathological changes in the liver, kidneys, heart, brain, and pancreas were examined.
In vitro bioactivity against alpha-amylase, alpha-glucosidase, glucose utility, and glucose
uptake in Caco2 colorectal cells was determined for the bioactive ethyl acetate fraction.
The phytochemical profile was obtained using Gas Chromatography-Mass Spectrometry
(GC-MS). Total phenolic content, total flavonoid content, and free radical scavenging
activity were determined. Mutagenicity and genotoxicity were assessed using quantitative
fluorescence microscopy and compared with Ames results obtained in this study.
The ethyl acetate fraction at 1000mg/kg significantly reduced blood glucose levels to 8.16
± 4.4 mmol/L from 28.42 ± 2.7 mmol/L after 28 days, comparable to glibenclamide
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(p=0.15). In vitro studies showed its α-glucosidase inhibitory activity. Animals receiving
Kigelia fruit fractions and extracts showed decreased weight (p<0.05). The ethyl acetate
fraction produced a more favourable lipid profile than glibenclamide. Inter-group
variations were observed in triglycerides (p=0.03), total cholesterol (p =0.001), and nonHDL cholesterol (p=0.0007) levels. Biochemical and histological examinations revealed
improved cell viability in the liver, kidneys, and nervous system of treated rats.
No significant differences in DPPH inhibition, TPC, or TFC were observed amongst the
fractions. GC-MS analysis showed that the most bioactive fraction contained 11"(2-
cyclopenten-1-yl) undecanoic acid, (+)- and cyclopentane undecanoic acid, along with the
indole alkaloids Akuammilan-17-ol-10-methoxy, N-nitroso-2-methyl-oxazolidine and
epoxide Oxirane2.2″ -(1.4-butanediyl) bis-.
The aqueous extract had no effect on cell viability, whereas the ethyl acetate extract caused
a concentration-dependent decrease in cell viability (IC50 = 414.8 ± 8.69 µg/mL). Fruit
extracts showed similar effects on His+ revertants as the negative control, indicating no
mutagenic activity. The highest concentration of ethyl acetate fruit extract increased the
average nuclear area of Vero cells (IC50 EtOAc = 338.6± 1.058 µg/mL). After 48 hours,
no significant changes were observed in the ratio of multi+dual to mononucleated Vero
cells.
K. africana fruit fraction improved glucose and lipid profiles and the histoarchitecture of
organs in diabetes-induced rats. It showed notable alpha-glucosidase inhibitory activity,
whereas its alpha-amylase inhibitory activity was limited. At therapeutic doses, the extracts
did not display genotoxic properties. This study identified the bioactive phytocomposition
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of this fruit, highlighting its potential as a medicinal agent for the treatment of diabetes
mellitus. It suggests a potential natural alpha-glucosidase inhibitor and phytocompounds
that could serve as lead compounds for developing new antidiabetic medications.
Description
A Dissertation submitted in fulfillment of the requirements for the Degree of Doctor of Philosophy in Pharmacology
Keywords
Kigelia africana, Diabetes, Mutagenicity, Genotoxicity, GC-MS analysis, Phytochemistry, Namibia, University of Namibia