Pyranocarbazoles from <i>Murraya koenigii</i> (L.) Spreng. as antimicrobial agents

<p>The bioassay guided fractionation of methanolic extract of <i>Murraya koenigii</i> (L.) Spreng. leaves resulted in the isolation of seven pyranocarbazoles. These were evaluated against four bacterial strains and ten Candida sp. including two matched pair of fluconazole sensitive/resistant clinical isolates. Out of seven, three i.e. Koenine (mk279), Koenigine (mk309) and Mahanine (mk347) exhibited significant antibacterial activity MIC90 3.12–12.5 μg/mL against bacterial strains <i>Streptococcus aureus</i> and <i>Klebsiella pneumonia</i> compared with standard drug Kanamycin MIC90 12.5 μg/mL. However, only mk309 was found active against variety of Candida species MIC90 12.5–100 μg/mL. It was observed that hydroxylation at C-6 and C-7 positions in the studied pyranocarbazoles activate the bioactivity. Simultaneously, decrease in Log P value compares with −H and −O−CH3 substituted derivatives. The study is focused on selective antifungal and antibacterial activity of pyranocarbazoles on bacterial strains <i>S. aureus</i>, <i>K. pneumonia</i> and variety of Candida species with structure activity relationship observations.</p>