Phytochemical Investigation Of Aloe Pulcherrium Roots And Evaluation Of Its Antibacterial Activities

Abstract

Natural products isolated from plants have been providing noble and clinically active drugs. This plant-based traditional medicinal system continues to play an essential role in health care, with about 80% of the world’s inhabitants relying mainly on traditional medicines for their primary health care. Thus, the objective of this study was to isolate and characterizes bioactive natural products from the roots of Aloe pulcherrium. The air dried was extracted successively with n-hexane, chloroform, acetone and methanol solvents by maceration. The extracts were evaluated for their antibacterial activity against different bacterial strains (Staphylococcus aureus ATCC 25923, Escherichia coli ATCC35218, Pseudomonas aeruginosa ATCC 27853 and Bacillus subtilis ATCC 6633). The MIC were conducted using concentration ranging from 200 to 12.5 mg. mL-1 by serial dilution. The acetone extract has shown superior activities against all the strains. The extract has shown the inhibition zone diameter 15, 16, 12 and 24 mm against B.subtilis, E.coli, S.aureus and P.aeruginosa, respectively. Likewise, the corresponding inhibition zone of Gentamycin was found to be 20, 20, 23 and 25 mm against B.subtilis, E.coli, S.aureus and P.aeruginosa, respectively. The MIC results has also indicated that the lowest concentration (12.5 mgmL-1) have shown a significant influence on the four strains. Then, the acetone extract was subjected to fractionation using Column Chromatography (CC) over oxalic acid impregnated silica gel eluted with n-hexane containing increasing amounts of ethyl acetate and has resulted two compounds (AP-8G and AP-11D). Meanwhile, the antibacterial activities of the isolated compounds were carried out. The corresponding inhibition zone diameter for AP-11D was 22, 21, 18 and 23 mm, and AP-8G was 27, 22, 18 and 21 mm on B.subtilis, E.coli, S.aureus, and P. aeruginosa, respectively. Then, the pure compounds were characterized by using a combination of spectroscopic techniques such as IR, UV, 1H-NMR, 13C-NMR and, 2D NMR, so as to establish the structure of the isolated compounds. Finally, AP-8G was identified as 1, 6-dihydroxy-8-methyl-anthracene-7-methyl ester-9, 10-dione, (trivial name aloesaponarin I) and AP-11D as 1, 6-dihydroxy-8-methylanthracene-9, 10-dione, (trivial name aloesaponarin II) with melting points of 207-209 ℃ and 190-192 ℃, respectively. Devising alternative method of extraction as well as carrying the antifungal and antiplasmodium activities of this plant are recommended forfurther researchers.