PHYTOCHEMICAL SCREENING AND ANTIMICROBIAL ACTIVITY OF COMMON MULLEIN (Verbascum thapsus L.) ROOT, LEAF AND FRUIT EXTRACTS

Abstract

ommon mullein, also known as Wooly Mullein (Verbascum thapsus L., Scrophulariaceae) has been used as a medicinal herb since ancient times. The aim of the present study was to investigate qualitative screening of major phytochemicals and antimicrobial activity of common mullein (Verbascum thapsus L.) root, leaf and fruit methanolic extracts. The qualitative analyses of major phytochemicals were tested for tannins, phlobatannins, saponins, flavonoids, steroids, termenoids and alkaloids. The antimicrobial experiment was arranged as 3 x 1 x 4 (3 source extracts: root, leaf and fruits of common mullein at three concentration levels; 1 solvent system i.e. methanol, 4 test organisms (2 bacteria: Escherichia coli (gram negative), Staphylococcus aureus (gram positive), two fungi (Aspergillus versicolor and A. Niger)) factorial design in three replications. The result indicated that phytochemical substances of the methanolic extract of V. thapsus (L) were screening by qualitative chemical analysis which revealed the presence of tannins, flavonoids, steroids, terpenoids and alkaloids as bioactive compounds in the leaf methanolic extracts. While the methanolic fruit extract of V. thapsus revealed the presence of tannins, saponins, flavonoids, terpenoids and alkaloids. Contrastingly, the methanolic root extract indicated the presence of tannins, phlobatannins, saponins, flavonoids, steroids, terpenoids and alkaloids. The antibacterial activity of methanolic extracts of V. thapsus (L) root, leaf and fruit at highest concentration of the extracts has recorded mean zone of inhibition ranging from 12.00±0.55 to 16.07±0.40mm While the antifungal activity of the methanolic extract with growth inhibitory effect at the highest dose recorded a mean zone of inhibition ranged from13.50±0.50 to 16.03±0.90mm. The methanolic root extract of V. thapsus (L.)demonstrated strong bactericidal activity with minimum inhibitory concentration MIC (6.25mg/ml) and corresponding minimum bactericidal concentration MBC (12.50mg/ml) against S.aureus. The strongest antifungal activity with MIC (4.70mg/ml) and corresponding minimum fungicidal concentration MFC (6.25mg/ml) was recorded for methanolic fruit extract of V. thapsus (L) against Aspergillus versicolor. It can be concluded from the result of antimicrobial activities that the methanolic root extract of V. thasus (L) had exhibited the strongest antibacterial potential while the methanolic fruit extract presented strongest antifungal potential