Antibacterial activity of isoquinoline isolated from Andrographis serpyllifolia

Abstract

The medicinal herb Andrographis serpyllifolia is used in various ethnobotanical preparations due to its high therapeutic value. In this study, the antibacterial activity of aqueous, hexane, chloroform and methanol extract of A. serpyllifolia extracts were tested against human pathogenic bacteria Campylobacter jejuni- ATCC 29428, Neisseria gonorrhoeae- ATCC 49226, Haemophilus influenzae- ATCC 10211, Enterobacter aerogenes- ATCC 13048 and Mycobacterium tuberculosis- MTCC 300. Among the extracts tested aqueous and methanol extract recorded significant inhibitory activity. Methanol extract was further subjected to bioactivity directed fractionation coupled with isolation and characterization. Purification of the bioactive principle was done by subjecting the crude extract to thin layer, column and HPLC analysis. The fraction exhibiting the antibacterial activity with highest purity and yield was further subjected to 1H and 13C NMR and LC-MS analysis to elucidate its structure. The compound was identified as C17H27NO with IUPAC name 8-(3, 4- dihydroisoquinolin-2(1H)-yl) octan-1-ol. Further MIC of the isolated compound against C. jejuni, H. influenza and M. tuberculosis was 500, 500 and 250 μg/ml respectively. The present study is successful in isolating a plant bioactive principle responsible for the antibacterial activity.