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
