Thin Layer Chromatography Bio-autography guided identification of Antibacterial constituents of leaf extract of Stereospermum kunthianum Cham. (Bignoniaceae)

Abstract

Background: There is an incessant quest for the discovery of novel antibacterial agents. Stereospermum kunthianum Cham.  Bignoniaceae) is used in traditional medicine in Nigeria and other parts of Africa in the treatment of venereal diseases e.g., syphilis,  wounds, refractory cough, malaria, tooth ache leprosy etc. The present work investigates the antimicrobial activity and phytochemical constituents of the ethanolic leaf extract of the plant.  Methods: Ethanolic leaf extract of S.Kunthianum was obtained by macerations method. Agar well diffffusion method was used to carry  out preliminary antimicrobial susceptibility testing. The test was carried out at extract concentration of 100, 200 and 400 mgmL-1 . The  agar dilution method was used to determine the Minimum Inhibitory Concentration (MIC) of the extracts. Phytochemical screening  was conducted using standard procedures. Thin layer chromatography bioautography analysis was carried out using the agar overlay  method. Six micro-organisms including two gram positive- Bacillus subtilis and Staphylococcus aureus, two gram negative Salmonella  typhi , and Pseudomonas aeruginosa, two fungi, Aspergillus niger and Candida albicans were used as test organisms.  Results: The ethanol extracts of S.kunthianum leaves showed antimicrobial activity against B.subtilis, S.aureus and S.typhi with zones of  Inhibition ranging from 13±1.41 to 29.5 ± 1.00 mm and MIC values ranging from 16 -64 mgmL-1 . Phytochemical screening revealed the  presence of saponins, flflavonoids and terpenoid compounds  Conclusion: The study showed that the antibacterial activities of the leaf extract are probably due to polyphenolic and steroidal  compounds.  &nbsp