Phytochemical Analysis and Evaluation of Invitro Antimicrobial and Antioxidant Activities of the Leaf Extracts and Leaf Extract Mediated Silver nano Particles of Verbascum sinaiticum Benth

Abstract

Verbascum sinaiticum (Mullein) is one of the medicinal plants, traditionally used to cure various human diseases including skin disorders, fungal infection, stomachache, elephantiasis, wound and several animal ailments. Phytochemical investigation and evaluation of biological properties of traditionally used medicinal plants such as Verbascum sinaiticum in Ethiopia haven’t been widely studied. The aim of this study was to investigate the phytochemical constituent, evaluation of antimicrobial and antioxidant activities of leaf extracts and leaf extract-mediated green synthesized silver nanoparticles of V. sinaiticum. Leaves powder of V. sinaiticum was macerated with methanol, distilled water, acetone, chloroform and n-hexane solvents separately for extraction. The qualitative phytochemical analysis was performed by using standard methods and antimicrobial activity of crude extracts and silver nanoparticles were done by Disc diffusion assay against selected bacterial and fungal species. The Minimum inhibitory concentrations of crude extracts and silver nano particles were determined by broth dilution methods. The antioxidant activities were evaluated by DPPH assay. Silver nanoparticles were synthesized by mixing silver nanoparticles and plant leaf extract. Synthesized silver nanoparticles were characterized by XRD and SEM. The results of phytochemical compositions showed the presence of alkaloids, flavonoids, saponins, steroids, phenols, tannins, glycosides and terpenoids in different crude extracts of V. sinaiticum leaf. The XRD pattern confirmed the green synthesized silver nanoparticles were in nano crystalline nature with face cubic centered structure. SEM analysis indicated highly agglomeration of silver nanoparticles with spherical shape. Antimicrobial activity of the extract and silver nanoparticles showed maximum zone of inhibition against S. aureus (17±1.0mm), C. albican (13.0±1.0mm) and E. coli(16.0±1.0mm), C. albican (15.0±1.0mm) respectively. Methanol and chloroform extract exhibited significantly(p<0.05) a high antimicrobial activity. Whereas acetone and distilled water extract shown moderate antimicrobial activity. The minimum inhibitory concentrations values of the leaf crude extracts and silver nanoparticles were range from 12.5 to 50mg/ml and 0.625 to 1.25mg/ml respectively. The minimum bactericidal and fungicidal concentration values ranged from 50 to 100mg/ml and 5 to 10mg/ml for crude extracts and silver nanoparticles respectively. Methanol extract and silver nanoparticles exhibited very high radical scavenging activity with IC50 values 49.42 and 18.35µg/ml respectively. Whereas acetone crude extract revealed low radical scavenging activity with high IC50 values (172.62 µg/ml). This result suggests crude extracts and Leaf extract mediated AgNps of V. sinaiticum exhibited both antimicrobial and antioxidant activity. Various therapeutic agents present in the leaf extracts of this plant are promises this plant to be studied further.