PHYTOCHEMICAL INVESTIGATION AND ANTIBACTERIAL ACTIVITY EVALUATION OF THE ROOT EXTRACTS OF OTOSTEGIA INTEGRIFOLIA

Abstract

Medicinal plants have been the oldest and most widely used system of medicine to treat diseases caused by different pathogens and fight infections worldwide since ancient times. Recently, including in Europe and America, there has been a growing interest in medicinal plants. Traditionally, O. integrifolia leaves have been used in Ethiopia & Eritrea as insecticides, to treat tonsillitis, uvulitis, hypertension, etc. Its roots have also been used as an anthelmintic and for the treatment of lung conditions. Thus, this study was aimed at phytochemical investigation and antibacterial activity evaluation of the root extracts of Otostegia integrifolia. The roots were collected, washed, chopped into pieces, air-dried, ground and extracted successively with CHCl3, CHCl3/CH3OH (1:1 v/v), and CH3OH to obtain 0.4, 3.77, and 1.27 % of crude extracts, respectively. The phytochemical screening test revealed the absence of alkaloids and anthraquinones and the presence of terpenoids, phenols, flavonoids, saponins, tannins, steroids, coumarins, carbohydrates, and glycosides in all extracts except phenols, which is absent in CHCl3 extracts. The CHCl3/CH3OH (1:1 v/v) extract was subjected to gradient elution of silica gel column chromatography in n-hexane/EtOAc solvent system. The elution was result in a total of 122 fractions, and fractions 48-51 (FT1) and 59-65 (FT2) had single spots on TLC. Based on the spectral data obtained from IR, 1H NMR, 13C NMR, and DEPT-135, the compounds were proposed to be hystroxene-I for FT1 and Angustanoic acid E for FT2. The extracts and isolated compounds were evaluated for their antibacterial activities against two gram positive bacterial strains (S. pyogen (ATCC19615), S. aureus (ATCC25923)) and two gram negative bacterial strains (P. aeruginosa (ATCC27853), E. coli (ATCC25922)) using ampicillin as a positive control, and all showed positive effects. Among FT1 and all the extracts FT2 exhibited the most effective antibacterial activity and the CHCl3 extract showed the least. The 400 μg/ml of isolate FT2 showed comparible effects (11.5, 12, 11, and 10.5 mm) with Ampicillin (13, 14, 12.5, and 12 mm) on S. aureus, S. pyogen, E. coli, and P. aeruginosa respectively