Phytochemical and Antidiabetic Evaluation of the Methanolic Stem Bark Extract of Spathodea campanulata (P. Beauv.) Bignoniaceae

Background: Spathodea campanulata (P. Beauv.) Bignoniaceae extract (SCE) is one of many herbal medicines used widely in Ugandan traditional medicine for various ailments. Generally most of these herbal medicines are yet to be standardized or have their phytochemical content characterized. Method: This study identified the secondary metabolites in the stem bark methanolic extract and quantified them. The same extract was subjected to serial solvent fractionation, TLC characterization and antidiabetic testing. Results: The secondary metabolites were found to comprise of 7.5% alkaloids, 10% flavonoids, 13% tannins and 17% saponins per gram of plant material. The TLC characteristics of the fractions (hexane (HX), ethylacetate (EA) and methanol (ME)) viewed under UV light revealed spots with the following Rf values; the hexane partition gave HX7EA3 (0.96 and 0.68) HX9EA1 (0.68 and 0.3), EA1ME9 (0.86 and 0.58), EA3ME7 (0.87), EA7ME3 (0.85) and EA9ME1 (0.85). The ethylacetate partition gave the following HX1EA9 (0.53, 0.34 and 0.18), HX3EA7 (0.59, 0.40 and 0.26). Discussion: All the fractions produced nominal reduction of hyperglycemia. Except hexane fraction at 50 mg/kg and ethylacetate fraction at 200 mg/kg all the fractions had percentage reductions of glucose greater than that of the control at the experimental doses. Although the values of percentage reductions of hyperglycemia by the hexane fraction were apparently dose-dependent, the greatest margin of reduction of hyperglycemia was observed in the residual aqueous fraction. Conclusion: It was found that SCE contains valuable phytochemicals in appreciable quantities which are antidiabetic. The residual aqueous fraction is the most potent antihyperglycemic of the solvent fractions.