Phytochemical investigation and antimicrobial evaluationof the root bark of dodonaea angustifolia

Abstract

Medicinal plants are considered as good resources of ingredients which can be used in drug development. Plant derived drugs are also considered as safe and with little side effects when compared to synthetic drugs. Thus, the aim of this study was to isolate and characterize compounds from the root bark of Dodonaea angustofolia and evaluate its antimicrobial activities. The air-dried root bark of the plant material was sequentially extracted with petroleum ether, chloroform, acetone and methanol by maceration at room temperature and gave the crude extracts amounting to 6.5 g, 12 g, 8 g and 36 g respectively. The phytochemical analysis of the extracts revealed the presence of alkaloids, phenols, tannins, saponins, flavonoids and sterols. The chloroform and acetone extract was combined as they have displayed similar TLC profile and subjected to silica gel column chromatography (CC) for fractionation and purification of the compounds. The column was eluted with petroleum ether with increasing polarity of ethyl acetate and has resulted six compounds DA1, DA2, DA3, DA4, DA5 and DA6. However, characterizations of only two compounds were performed. The structures of the isolated compounds were performed by NMR (1HNMR, 13CNMR, and DEPT-135) spectroscopic data and comparison with reported literature data. The isolated compounds were characterized as (3β, 22E)-Stigmasta-5, 22-dien-3-ol (DA1) and β-Stigmasteryl linoleate (DA3). Both compounds were isolated for the first time from the study plant species. The antibacterial and antifungal activity of the crude extract and isolated compounds were evaluated against four bacterial strains (Staphylococcus aureus, Bacillus cereus, and Salmonella Typhimurium and Escherichia coli) and a fungal strain (Candida albicans) using agar disk diffusion method. The extracts showed zone of inhibition ranging 7.5-12.75 mm, with the acetone extract exhibited the highest activity against both bacteria and fungi strain. Therefore, the acetone extract was further evaluation for minimum inhibitory concentration and displayed 62.5, 15.6, 15.6, 31.3 and 15.6 mg/ mL against, E.coli, S. typhi, B. cereus, S. aureus and C. albican respectively. The isolated compounds have weak antibacterial activity but compound DA5 has good antifungal activity. Therefore, the presence of this phytochemicals in this plant root bark provides scientific support for the ethno medicinal use of the plant