Components and Bioactivity of Ipomoea batatas (L.) (Sweet Potato) Ethanolic Leaf Extract

Abstract

Sweet potato (SP) popularly known as Ipomoea batatas, has played an important role as an energy and a phytochemical source in human nutrition and animal feeding as well as herbal medicine to treat inflammatory and infectious oral diseases in Nigeria. This research aims to evaluate the secondary metabolites (phytochemical), antioxidants and antimicrobial activities as well as proximate analysis and to determine the minerals content of sweet potato ethanolic leaf extracts. The screenings were performed for triterpenes, steroids, alkaloids, anthraquinones, coumarins, flavonoids, saponins, tannins and phenolic acids. The color intensity of the precipitate formation was used as analytical responses to these tests. The antioxidant capacity was evaluated and antimicrobial activity was done by agar well diffusion method. The phytochemical screening showed the presence of secondary metabolites. Alkaloids, saponin, cardiac glycosides, tannin, terpenoidand steriod respectively with the following values 13.649%, 2.545 mg/g, 8.271 mg/g, 4.726 mg/g, 6.888 mg/g and 0.276%. Flavonoids were 0.852 while negative results were obtained for phlobatannin and anthraquinone. Proximate analysis of SP leaf, moisture content(MC), crude fat (CF), crude protein (CP),ash content (ASH), cured fat (CFAT) and carbohydrate(CHO) as 32.98%, 0.725%, 14.953%, 5.863%, 0.319% and 45.16%, respectively. Ca, Mg, Fe, Na and K were the mineral contents determined for SP. The zones of inhibition of bacterial growth at different concentrations (100 mg/ml, 50 mg/ml, 25 mg/ml and 12.5 mg/ml) of SP leaf extracts showed the highest antibacterial activity to Salmonella typhi with 25 mm zones of inhibition at 100 mg/ml and lowest activity to Listeria monocytogens, Staphylococcus aureus, Vibrio cholea and Pseudomonas aeruginosa all with 20 mm zones of inhibition and 12.5 mg/ml. However, the leaf extracts had the lowest antimicrobial activity to Enterrococcus faecalis, with 7 mm diameter. SP leaves demonstrated the presence of secondary metabolites with potential biological activities. Therefore it can be concluded that bioactive components and antimicrobial activity of sweet potato leaf ethanol extract against bacteria show its medicinal value and supports the widespread use of the plant as local remedy for a variety of ailment.