Phytochemical investigation of Aloe kefaensis roots and evaluation of its antimicrobial activity

Abstract

Infectious diseases are a serious and remain health and economic problem due to the emerging of new infectious antimicrobial resistance agents. Therefore, the search for antimicrobial compounds mainly from medicinal plants with traditional practice cannot be over emphasized so as to target these problems. Thus, the aim of this study was to isolate compounds from roots of Aloe kefaensis and evaluate their antimicrobial activity. The air-dried and powdered plant material was sequentially extracted with petroleum ether, dichloromethane, acetone, and methanol to yield crude extracts of 3.2 g (0.4 %), 7.5 g (0.93 %), and 10 g (1.25 %), 7 g (0.88 %) respectively. The extracts were evaluated for their in-vitro antimicrobial activity against four bacterial (E.coli, S.aureus, B.cereus, S.typhi, and one fungal (C.albicans) strains using agar disk diffusion method. Superior antimicrobial activity was exhibited against all the strains by dichloromethane extract with the highest activity was observed against S. typhi (23.0 ± 0.28 mm). Following this superior activity, serial dilutions of the extract have been prepared with a concentration of 100, 50, 25, 12.5 mg/ml; and showed the maximum inhibition of 18.0 ± 0.28, 15.5 ± 0.71, 11.0 ± 0.28, and 10.0 ± 0.71 mm , respectively against S. typhi. The acetone extract and dichloromethane extract were combined, as their TLC profile is similar and subjected to silica gel column chromatography for fractionation and isolation of the compounds. The column was eluted with petroleum ether containing increasing amount of EtOAc and resulted six compounds (AK-1, AK-2, AK-3, AK-4, AK-5, and AK-6) after further purification by using Sephadex LH-20 and small size column chromatography. The structural elucidation of only two compounds were carried on basis of NMR ( 1H NMR, 13C NMR and DEPT) data and found to be deoxyerythrolaccin (AK-3), and (5Z, 9Z)- 26-methyloctacosa-5, 9-dienoic acid (AK-2). Antimicrobial evaluations of the isolated compounds were also carried out, and AK-3 and AK-4 have displayed strong activity against S. typhi and E. coli (16.5 ± 0.71-19.0 ± 0.28 mm). The compounds were also showed interesting antifungal activity against C. albicans with superior activity exhibited by AK-3 with zone of inhibition 17.5 ± 0.71 mm. The antimicrobial activity of the crude extracts and isolated compound support the traditional uses of the plants for the treatments of microbial infections