Phytochemical Investigation And Antibacterial Activities Of Roots Extracts Of Aloe Debrana

Abstract

The genus Aloe (Asphodelaceae), with nearly 600 species confined mainly to Africa, has over the years proved to be one of the most important sources of biologically active compounds. There are about 46 Aloe species in Ethiopia , of which 24 are endemic. In Ethiopian traditional medicine, the leaf latex of Aloe debrana is used for the treatment of several diseases including malaria and infectious diseases. This study focused on extraction, isolation and characterization of the chemical constituents from the roots of Aloe debrana. The roots were extracted by dissolving 500g grinded and powdered root sample in the solvent CH2Cl2/CH3OH (1:1) and CH3OH yielded 16.51g (3.3%) and 9.98g (2.0%) successively, followed by separation using repeated silica gel column chromatography which afforded two compounds. They were characterized as isomer of aloe saponarin I (1,8-dihydroxy-3-methyl-4-anthraquinoic methyl methanoate (AD-18) and 2-ethyl-2,3-dihydro-7-hydroxychromen-4-one (AD-20). The structures of these compounds were elucidated by using spectroscopic analysis (UV-Vis, IR and 1D- NMR). Phytochemical screening test revealed the presence of anthraquinones, saponins, and steroids whereas alkaloids, flavonoids, protiens and triterpenoides were absent. The antibacterial activity of crude extract (0.5mg/ml) as well as one of the isolated compound, AD-18 (0.5mg/ml) were conducted using disk diffusion method using gentamycine and methanol as positive and negative controls respectively on selected strains of microorganisms which were Staphylococcus aureus, Bacillus subtilis, Escherchia coli, and Proteus mirabilis. Accordingly, 11, 7 ,15 and 6 mm zone of inhibition were found to be the cut off for crude extract, AD-18 ,gentamycine (0.05mg/ml) and methanol respectively, against S. aureus. Whereas 6, 9 , 15 and 6 mm were found to be cut off for crude extract, AD-18, gentamycine and methanol respectively, against E.coli. The present study started with only 500g of the plant material and could not achieve to isolated and identify some of the minor compounds as supported by the literature reports, literature reports suggest for the genus as rich source of anthraquinones, Hence, future phytochemical work is recommended starting with higher amount of the plant material and also needs further optimization of extraction solvents for better extraction yeild.