Phytochemical, Antibacterial And Antioxidant Studies Of The Flower Extracts Of Vernonia Amygdalina

Abstract

Medicinal plants are the raw materials for both traditional medicine and conventional medicine and 90% of all traditional medicines are estimated to be plant based. Vernonia amygdalina is a soft woody shrub/tree belonging to the family Asteraceae and genus Vernonia. The flowers of V. amygdalina were extracted successively with CHCl3 and acetone to furnish 1.78 and 1.91%, respectively. The phytochemical screening test of the chloroform extract of the flower of V. amygdalina revealed the presence of secondary metabolites including alkaloids, quinones, saponins, steroids, tannins and terpenoids where as the acetone extract showed the presence of alkaloids, flavonoids, phenols, quinones, saponins, steroids and terpenoids. The CHCl3 extract after silica gel column chromatography has led to the isolation of two compounds identified as tricosane (VAC-F1) and vernolide (VAC-F16). On the other hand, the acetone extract furnished isorhamnetin (VAA-F16-17) and luteolin. Structure elucidations of these compounds were achieved using various spectroscopic methods such as NMR, IR and UV-Vis. The extracts and constituents were assessed for their radical scavenging activity. Results showed that the acetone extract and isorhamnetin scavenged the DPPH radical by 91.6 and 94%, respectively. The result is comparable with ascorbic acid (97%) used as positive control. Furthermore the extracts, isorhamnetin and vernolide were also evaluated for their antibacterial activity against three gram negative (Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis) and two gram positive (Staphylococcus aureus and bacillus) bacteria. The CHCl3 extract and vernolide showed strong activity against S. aureus with an inhibition zone of about 21 and 19 mm, respectively. The acetone extract and isorhamnetin were active against all bacterial pathogens tested in this study. The biological activity displayed by the extracts and constituents of this plant corroborate the traditional uses of this plant by the local people against various diseases.