Phytochemical Analysis, In silico Molecular Docking Study, and Evaluation of Antibacterial and Radical Scavenging Activities of Constituents of the Roots Extracts of Gomphocarpus purpurascens A. Richs.

Abstract

The notable increase in emerging infectious diseases (EIDs) and re-emerging infectious diseases (REIDs), coupled with the rise of antimicrobial resistance in healthcare environments, has become a significant global health issue. Natural products derived from plants origin and their derivatives continue to play a key role in the development of antimicrobial drugs. In Ethiopia, there are cultural diversity which allow varies use of medicinal plants. G. purpurascens is an endemic plant to Ethiopia which widely practiced as a medicinal plant to treat different human ailment such as Pneumonia, itching, mental illness, ring worm, wound, abdominal pain, and hemorrhoid. Despite of it’s widely uses, to the best of our knowledge, there are no scientific reports on the isolation of bioactive molecules, and evaluation of biological activities of the plant. This study aims to perform a phytochemical analysis and assess the in-vitro antibacterial and antioxidant activities along with molecular docking study of phytoconstituents of root extract of Gomphocarpus purpurascens. Hydrodistillation and maceration extraction techniques using DCM/MeOH were employed in this study where silica gel column chromatography used for separation of compounds. The isolated compounds were characterized by determining their physical properties and spectroscopic techniques (GC-MS, UV, FT-IR, 1H NMR and 13C NMR). The biological activity was evaluated in vitro for its anti bacterial activities by using the disc diffusion method and radical scavenging activity was assessed by DPPH assay. The phytochemical screening indicated the possible presence of flavonoids, coumarins, saponins, tannins, steroids, anthraquinones, glycosides, phenolics, and terpenoids. Hydrodistillation yielded (0.028% w/w) essential oils and its GC-MS analysis furnished 51 different compounds with major constituent of benzoic esters, fatty acid and its derivatives, phenols and steroids. Silica gel column chromatography has led to the isolation of five compounds namely: β-sitosterol (32), ethyl palmitate (37), oleanolic acid (38) ursolic acid (39) and Isorhamnetin 3-O-rhamnoside (40).The crude extract and isolated compounds exhibited promising biological activity. DCM/MeOH extract showed inhibition zone 16.14±0.58 mm, and 15.00±0.44 mm against (E. coli), and (S. aureus) at a concentration of 200 mg/mL. Compound 38 and 39 displayed highest activity against P. aeruginosa and E. coli with inhibition zone of 17.22±0.58mm and 17.00±0.22 mm respectively at concentration of 200 mg/mL. This was validated by the binding affinity recorded (-8.2 kcal/mol) against Pseudomonas quinolone signal A and (-8.1 kcal/mol) E. coli DNA Gyrase B in docking studies. The highest radical scavenging activity was observed by isorhamnetin 3-O-rhamnoside with IC50 8.63 (μg/mL) followed by Oleanolic acid and ursolic IC50 =11.21 (μg/mL. Generally the study showed the plant is enrich of phytochemicals and showed anti-bacterial and radical scavenging activities