Four new carbazole alkaloids from Murraya koenigii that display anti-inflammatory and anti-microbial activities

Abstract

In our present study, four new, designated as murrayakonine A–D (1–4), along with 18 known carbazole alkaloids were isolated from CHCl₃ : MeOH (1 : 1) crude extracts of the stems and leaves of Murraya koenigii (Linn.) Spreng. The structures of the all isolated compounds were characterized by analysis of HR-ESI-MS and NMR (1D and 2D spectroscopy) results, and comparison of their data with the literature data. For the first time, all the isolates were evaluated for their anti-inflammatory activities, using both in vitro and in vivo experiments, against the key inflammatory mediators TNF-α and IL-6. The new compound murrayakonine A (1), O-methylmurrayamine A (13) and mukolidine (18) were proven to be the most active, efficiently inhibiting TNF-α and IL-6 release in a dose-dependent manner and showing decreased LPS induced TNF-α and IL-6 production in human PBMCs. Furthermore, all the isolates were screened for their antimicrobial potential, and the compounds girinimbine (12) (IC₅₀ 3.4 μM) and 1-hydroxy-7-methoxy-8-(3-methylbut-2-en-1-yl)-9H-carbazole-3-carbaldehyde (19) (IC₅₀ 10.9 μM) displayed potent inhibitory effects against Bacillus cereus. Furthermore, compounds murrayamine J (7) (IC₅₀ 11.7 μM) and koenimbine (14) (IC₅₀ 17.0 μM) were active against Staphylococcus aureus. However, none of the compounds were found to be active against Escherichia coli or Candida albicans.