Phytochemical Study and Alpha-amylase Inhibitory Properties of Leaf Extracts of Croton zambesicus (Müll. Arg.)

Aims: This study was designed to determine the phytochemical contents, percentage of alkaloids and flavonoids and also to determine the alpha-amylase inhibitory properties of the n-hexane, ethyl acetate and ethanol extracts from the leaves of Croton zambesicus (Müll. Arg.) in-vitro.

Study Design: Phytochemical Screening, determination of percentage alkaloids and flavonoids and in-vitro evaluation of alpha-amylase inhibitory activities of the leaf extracts.

Place and Duration: This work was carried out in the Chemistry Laboratory of the Department of Science Laboratory Technology (Chemistry Unit), School of Pure and Applied Science, Lagos State Polytechnic, Ikorodu and the Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria, between March and November, 2016.

Methodology: Croton zambesicus leaves was successively extracted with n-hexane, ethyl acetate, and ethanol by maceration to obtain the respective extracts. Phytochemical screening of the extracts for the presence of alkaloids, tannins, cardiac glycosides, steroids, saponins, flavanoids, anthraqiunones and reducing sugar was carried out using standard method. The percentage of alkaloids and flavonoids was determined using Harborne and Boham and Kocipaiabyazan methods respectively. Alpha-amylase inhibitory properties of the leaf extracts were carried in-vitro qualitatively by starch-iodine colour assay and then quantified using dinitrosalicyclic acid reagent (DNSA reagent) using acarbose as the standard.

Results: The results showed alkaloids, cardiac glycosides steroids and antraquinone derivatives were detected in all the extracts while tannins, saponins and flavonoids were detected only in the ethanol extract. The percentage of alkaloids and flavonoids in the Croton zambesicus leaf are 16.67±3.06% and 2.67±1.16% respectively. Starch iodide indicator indicated a positive Alpha-amylase inhibitory properties in the hexane and the ethanol extracts. The ethanol extract exhibited the most alpha-amylase inhibitory property (IC50= 78.7 ± 1.7) followed by the hexane extract (IC50= 89.2 ± 1.1) while the lowest was observed in the standard drug, acarbose (IC50= 114.9 ± 11.3).

Conclusion: The result of this study showed Croton zambesicus leaf extracts can effectively inhibit pancreatic alpha-amylase hence could be a source of new drugs for reducing post-prandial glucose level in diabetic patients.