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

Scientia Pharmaceutica Article In Vitro Activities of Enantiopure and Racemic 10 -Acetoxychavicol Acetate against Clinical Isolates of Mycobacterium tuberculosis Saradee Warit 1 , Kamolchanok Rukseree 2 , Therdsak Prammananan 1 , Poonpilas Hongmanee 3 , Pamaree Billamas 1 , Sarinya Jaitrong 1 , Angkana Chaiprasert 4 , Birgit U. Jaki 5,6 , Guido F. Pauli 5,6 , Scott G. Franzblau 5 ID and Prasit Palittapongarnpim 1,7, * 1 2 3 4 5 6 7 * Tuberculosis Research Laboratory, Medical Molecular Biology Research Unit, BIOTEC, National Science and Technology Development Agency, Thailand Science Park, Pathum Thani 12120, Thailand; (S.W.); (T.P.); (P.B.); (S.J.) Science and Liberal Art, Amnatcharoen Campus, Mahidol University, Bangkok 73170, Thailand; Department of Pathology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok 73170, Thailand; Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 73170, Thailand; Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60607, USA; (B.U.J.); (G.F.P.); (S.G.F.) Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60607, USA Department of Microbiology, Faculty of Science, Mahidol University, Bangkok 73170, Thailand Correspondence: ; Tel.: +66-02-201-5670 Academic Editor: Gernot A. Eller Received: 22 June 2017; Accepted: 13 September 2017; Published: 18 September 2017 In the process of evaluating the effect of several plant extracts against Abstract: Mycobacterium tuberculosis using the Microplate Alamar Blue Assay (MABA), an extract of Thai herb Alpinia galanga rhizome and its major component, 10 -acetoxychavicol acetate (ACA), exhibited marked anti-tuberculosis activity. The minimal inhibition concentrations (MICs) of the S-enantiomer of ACA (S-ACA) against M. tuberculosis H37Ra ATCC 25177 and H37Rv ATCC 27294 strains were 0.2 µg/mL and 0.7 µg/mL, respectively. More than 95% of 100 drug-sensitive and 50 drug-resistant mycobacterial clinical isolates were inhibited by extracted S-ACA at 1.0 µg/mL. All of the remaining isolates were inhibited at 2.0 µg/mL. In contrast to the S-enantiomer, synthetic racemic 10 -R,S-ACA (rac-ACA) showed MICs of 0.5 µg/mL and 2.7 µg/mL for M. tuberculosis H37Ra ATCC 25177 and H37Rv ATCC 27294, respectively, suggesting that the anti-tuberculosis effect might be primarily due to the S-form. These observations were in line with the MICs of rac-ACA against 98% of 93 drug-resistant clinical isolates, which showed the effective inhibitory dose at 2.0 µg/mL. After exposure to 2.7 µg/mL of rac-ACA for at least 3 h, the tubercle bacilli were completely killed. These demonstrated that ACA had potent anti-TB activity. Keywords: Alpinia galanga; 1’-S-acetoxychavicol acetate; anti-tuberculosis; drug resistance 1. Introduction Tuberculosis (TB) is caused by Mycobacterium tuberculosis and constitutes a major health problem exacerbated by the global human immunodeficiency virus (HIV) pandemic and the emergence Sci. Pharm. 2017, 85, 32; doi:10.3390/scipharm85030032 www.mdpi.com/journal/scipharm Sci. Pharm. 2017, 85, 32 Sci. Pharm. 2017, 85, 30 10.3390/scipharm85030032 2 of 8 2 of 8 drug-resistant strains, such as multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB of drug-resistant strains, such as multidrug-resistant TB (MDR-TB) and extensively drug-resistant (XDR-TB) [1]. Consequently, novel anti-tuberculosis drugs are widely sought after entities. TB (XDR-TB) [1]. Consequently, novel anti-tuberculosis drugs are widely sought after entities. Our laboratory has screened numerous medicinal plant extracts against the avirulent Our laboratory has screened numerous medicinal plant extracts against the avirulent M. tuberculosis H37Ra strain. The activity of 1′-S-acetoxychavicol acetate (S-ACA), a major secondary M. tuberculosis H37Ra strain. The activity of 10 -S-acetoxychavicol acetate (S-ACA), a major secondary metabolite of a popular Thai herb, Alpinia galanga (Linn) Swartz (A. galanga (syn. Languas galanga metabolite of a popular Thai herb, Alpinia galanga (Linn) Swartz (A. galanga (syn. Languas galanga (Linn) Stuntx), commonly known as greater galangal, gave the most promising primary screening (Linn) Stuntx), commonly known as greater galangal, gave the most promising primary screening result, with an activity comparable to that of known first-line drugs [2]. A. galanga belongs to the result, with an activity comparable to that of known first-line drugs [2]. A. galanga belongs to the family Zingiberaceae and is commonly used in the preparation of Thai condiments and family Zingiberaceae and is commonly used in the preparation of Thai condiments and ethnomedicine. ethnomedicine. The crude rhizome extract of A. galanga has been shown to inhibit the in vitro growth The crude rhizome extract of A. galanga has been shown to inhibit the in vitro growth of the avirulent of the avirulent M. tuberculosis H37Ra strain [3], streptomycin-resistant M. tuberculosis, M. avium and M. tuberculosis H37Ra strain [3], streptomycin-resistant M. tuberculosis, M. avium and M. bovis [4]. M. bovis [4]. Soundhari and Rajarajan [5] reported a minimum inhibitory concentration (MIC) of Soundhari and Rajarajan [5] reported a minimum inhibitory concentration (MIC) of 250 µg/mL 250 µg/mL of the lyophilized ethanolic extract of galangal against isoniazid-resistant isolates. An of the lyophilized ethanolic extract of galangal against isoniazid-resistant isolates. An ethanolic ethanolic extract at 50–100 µg/mL inhibited M. tuberculosis under axenic aerobic and anaerobic extract at 50–100 µg/mL inhibited M. tuberculosis under axenic aerobic and anaerobic conditions conditions and in an intracellular environment [6]. This is consistent with a previous report that and in an intracellular environment [6]. This is consistent with a previous report that A. galanga A. galanga extracts are able to penetrate into human adenocarcinomic alveolar basal epithelial cells extracts are able to penetrate into human adenocarcinomic alveolar basal epithelial cells (A549) (A549) and act on the bacterium residing intracellularly [7]. Additionally, broad spectrum activities and act on the bacterium residing intracellularly [7]. Additionally, broad spectrum activities of of A. galanga rhizome extracts toward other pathogens have been described since 1976. For instance, A. galanga rhizome extracts toward other pathogens have been described since 1976. For instance, it was found that the essential oil of A. galanga contains ACA at a high level and could inhibit the it was found that the essential oil of A. galanga contains ACA at a high level and could inhibit the growth of many dermatophytes that cause tinea or dermatophytosis [8]. Later, A. galanga crude growth of many dermatophytes that cause tinea or dermatophytosis [8]. Later, A. galanga crude extracts were found to (...truncated)