Evaluating the anti Mycobacterium tuberculosis activity of Alpinia galanga (L.) Willd. axenically under reducing oxygen conditions and in intracellular assays

Abstract

BackgroundIn tuberculosis (TB), the steadily increasing bacterial resistance to existing drugs and latent TB continue to be major concerns. A combination of conventional drugs and plant derived therapeutics can serve to expand the antimicrobial spectrum, prevent the emergence of drug resistant mutants and minimize toxicity. Alpinia galanga, used in various traditional medicines, possesses broad spectrum antibacterial properties. The study was undertaken to assess the antimycobacterial potential of A. galanga in axenic (under aerobic and anaerobic conditions) and intracellular assays.MethodsPhytochemical analysis was done using HPTLC. The acetone, aqueous and ethanolic extracts (1, 10, 25, 50 and 100 μg/ml) of A. galanga were tested axenically using Microplate Alamar Blue Assay (MABA) against Mycobacterium tuberculosis (M.tb) H37Rv and three drug sensitive and three multi drug resistant clinical isolates. The activity of the extracts was also evaluated intracellularly in A549 cell line against these strains. The extracts active under intracellular conditions were further tested in an axenic setup under reducing oxygen concentrations using only H37Rv.Results1´ acetoxychavicol acetate, the reference standard used, was present in all the three extracts. The acetone and ethanolic extracts were active in axenic (aerobic and anaerobic) and intracellular assays. The aqueous extract did not demonstrate activity under the defined assay parameters.ConclusionA. galanga exhibits anti M.tb activity with multiple modes of action. Since the activity of the extracts was observed under reducing oxygen concentrations, it may be effective in treating the dormant and non-replicating bacteria of latent TB. Though the hypothesis needs further testing, A. galanga being a regular dietary component may be utilized in combination with the conventional TB therapy for enhanced efficacy.

Identification of plant-derived natural products as potential inhibitors of the Mycobacterium tuberculosis proteasome

“…Furthermore, natural products have specific selectivity for cellular targets [ 26 ], with biologically active natural products providing selective ligands for disease-related targets [ 27 ]. The in vitro inhibitory activity of crude extracts and/or pure active compounds extracted from plants against Mtb has been extensively reported [ 28 – 31 ].…”

Plants in our combating strategies against Mycobacterium tuberculosis : progress made and obstacles met

“…The acetone and ethanolic extracts of these plants has also showed intracellular anti-TB activity inside human lung epithelial carcinoma cell line (Gupta et al. 2014 ). Marsypopetalum modestum Xue and R.M.K.…”

In Vitro Activities of Enantiopure and Racemic 1′-Acetoxychavicol Acetate against Clinical Isolates of Mycobacterium tuberculosis

“…Soundhari and Rajarajan [ 5 ] reported a minimum inhibitory concentration (MIC) of 250 μg/mL of the lyophilized ethanolic extract of galangal against isoniazid-resistant isolates. An ethanolic extract at 50–100 μg/mL inhibited M. tuberculosis under axenic aerobic and anaerobic conditions and in an intracellular environment [ 6 ]. This is consistent with a previous report that A. galanga extracts are able to penetrate into human adenocarcinomic alveolar basal epithelial cells (A549) and act on the bacterium residing intracellularly [ 7 ].…”