Phytochemical Screening and Anti-diabetic Evaluation of Citrus sinensis Stem Bark Extracts

Aim: Diabetes Mellitus remains amongst the highest cause of mortality in the world. This study was carried out to determine the phytochemical composition of stem bark extracts of Citrus sinensis and study their anti-hyperglycaemic activities as well as their modulatory effects on starch and sucrose digestion on normal Wistar rats.

Methodology: Stem bark Aqueous (AqE), Ethanolic (EtE), Hydroethanolic (HEE) extracts of C. sinensis were prepared. The content of polyphenols, flavonoids, alkaloids was determined. Anti-hyperglycaemic activity was evaluated in vivo by oral glucose tolerance test (OGTT) for 120 minutes. Wistar male rats of 180-200 g were used. After an overnight fast, their glycaemia were measured (T0). Rats were then distributed into five groups of six each: Control (water), Tests (400 mg/kg of each (AqE, EtE, HEE) extracts), Reference (4 mg/kg B. W., glibenclamide). Thirty minutes later, an overload of 2 g/kg B. W. of glucose was administered to all the groups. Glycaemia was measured by tail pricks: 30, 60, 90, 120 minutes after glucose administration. Sucrose (2 g/kg B. W.), starch (1 g/kg B. W.) and acarbose in co-administration were used as substrates for digestion in a protocol similar to OGTT.

Results: EtE was very rich in polyphenols (435.56 ± 3.85 µg of eq catechin/mg). Area under the Curves, AUC (mg.min.dL-1, P=.05) were: 4015, 786.6, 1163 for PC, AqE group, Reference respectively and confirmed that AqE was more efficient than glibenclamide. AqE also showed moderate efficacy with sucrose (841.2 vs 1172 mg.min/dL, P=.05) and starch digestion (892.8 vs 1148; P=.05) compared to positive controls.

Conclusion: Therefore, stem bark aqueous extract of C. sinensis is able to reduce postprandial glycaemia by slowing down the absorption of glucose, challenging the efficacy of glibenclamide,an anti-diabetic drug. Also, AqE has moderate efficacy on starch and sucrose digestion. AqE could thus be further explored for its potency in the treatment of diabetes mellitus.