Phytochemical Investigation, Biological Evaluation and Computational Studies of Isolated Compounds from the Root Extracts of Acanthus polystachius

Abstract

Acanthus polystachius (Acanthaceae) is a medicinal plant traditionally used for treatment of diseases in livestock and humans; it alleviates bleeding and stabbing pain, scorpion stings,, malaria, and vomiting. In view of its traditional uses and the absence of scientific reports, an attempt was made to explore its phytochemicals, evaluate their biological activities, and perform computational studies on the isolated compounds from the solvent extracts of the roots of A. polystachius. In this regard, the dried and pulverized roots of the plant (800g) were extracted with n-hexane, chloroform, EtOAc, and MeOH, resulting in extract yields of 1 g, 1.25 g, 2.1 g, and 27.65 g, respectively. Phytochemical screening of the n-hexane, chloroform, EtOAc, and MeOH extracts revealed the presence of flavonoids, saponins, terpenoids, alkaloids, phenols, coumarins, and steroids. The essential oil obtained by hydrodistillation was analyzed using GC-MS and showed the presence of 37 components, with n-hexadecanoic acid identified as the major constituent (34.89%) of the total components. EtOAc and chloroform extracts were subjected to repeated silica gel column chromatography and four compounds were isolated and identified as benzoxazol-2(3H) -one, 2, 4-dihydroxy-(2H)-1,4- benzoxazin-3(4H)-one, 2-hydroxy-2H-1,4-benzoxazin from EtOAc, and β-stigma sterol from chloroform. Structural elucidation of these compounds was performed using UV-Vis, IR, and NMR spectroscopy techniques, and the obtained data were compared with literature. The radical scavenging activities of the n-hexane, chloroform, EtOAc, MeOH extracts, as well as EO and isolated compounds were assessed using the DPPH assay, and found to inhibit 93.72% with IC50 10.20±4 for MeoH extract and 85.99% with IC50 33.16±4 for APF-42 isolated compound. The extracts and isolated compounds were also evaluated for their antimicrobial activities by disc diffusion method against four bacterial strains viz., E. coli, P. aeruginosa, E. faecalis and S. pyogenes and one fungi C. albicans. IZ of 21.66±0.57 mm by n hexane extract and 22.33±0.57 mm by APR-29 against E. faecalis. APF-170 displayed 26.67±00mm against C. albicans. These were promising antibacterial and antifungal activities compared to the standard drugs. The results obtained from the study support the traditional uses of plant against mos and provide the scientific basis for future research.