Comparative Alpha-amylase Inhibitory Properties of the Leaf Extracts of Petiveria alliacea L.

Aims: The study was designed to determine the phytochemical contents and the inhibitory effects of the leaf extracts of Petiveria alliacea L. on alpha-amylase enzyme.

Study Design: Phytochemical Screening and in-vitro evaluation of alpha-amylase inhibitory effects of the leaf extracts of Petiveria alliacea L using starch-iodide and 3,5- dinitrosalicyclic acid assays.

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 Biochemistry Laboratory of the Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria, between April and August 2016.

Methodology: Petiveria alliacea leaves was successively extracted with n-hexane, ethyl acetate, and ethanol by maceration for 72 h to obtain the respective extracts. Phytochemical screening of the extracts for the presence of secondary metabolites: tannins, alkaloid, flavonoids, cardiac glycosides, reducing sugar, saponins, and anthraquinones was carried out using standard methods. The percentage of alkaloids and flavonoids was determined using Harborne and Boham and Kocipaiabyazan methods respectively. In-vitro alpha-amylase inhibitory properties of the leaf extracts were carried out by starch-iodine and 3,5-dinitrosalicyclic acid reagent (DNSA reagent) assays using acarbose as the standard.

Results: The results showed alkaloids, cardiac glycosides were detected in all the extracts. saponins, flavonoids, anthraquinones and reducing sugars were detected in the ethyl acetate and ethanol extracts; steroids are detected in the hexane extract only; tannins and terpenoids were not detected in all the extracts. The percentage of alkaloids and flavonoids are 2.14±0.16% and 6.14±1.07% respectively. All the extracts showed positive Alpha-amylase inhibitory properties with percentage inhibition increasing with increase in concentration. starch-iodine and 3,5- dinitrosalicyclic acid reagent assays gave similar values for percentage inhibition of alpha-amylase at 50 and 100 µg/mL concentration of extracts in the hexane, ethyl acetate extracts and acarbose with slightly different values for the ethanol extract.

Conclusion: The results suggested Petiveria alliacea leaf extracts could reduce post-prandial glucose level in type 2 diabetes mellitus and both methods of assay are effective.