Search for synthetic and natural substances with in vitro bioactivity against Mycobacterium tuberculosis. Part I

Maria-Fernanda Moreno , Wellman Ribón

Affiliation: Universidad Industrial de Santander. Colombia.

Keywords: Mycobacterium tuberculosis, tuberculosis, antimycobacterial activity, synthetic molecules, essential oils, plant extracts,

DOI: 10.17160/josha.4.6.367

Languages: Spanish, Castilian

INTRODUCTION: tuberculosis (TB) is still considered as an important worldwide health problem. For this reason, national and international health agencies encourage the researchers to improve and strengthen the control strategies and disease treatment. Currently, there have been important advances in the discovery and development of drugs that probably will be included in the standard scheme of anti-TB treatment, however for many of the current treatments, there have been resistant strains reported and even worst for most of the new treatments resistance is expected, making it necessary to maintain a continuous search for treatment alternatives. OBJECTIVE: determine the in vitro antimycobacterial activity of 15 synthetic molecules, 14 essential oils and 6 extracts from endemic plants growing in the department of Santander, Colombia. METHODS: the 15 synthetic molecules were designed using the strategy of diversity-oriented synthesis (DOS), the 14 essential oils were extracted by hydrodistillation assisted by microwave radiation (MWHD) and the 6 plant extracts were obtained by supercritical fluid extraction (SFE). Bioactivity was tested against the reference strain of Mycobacterium tuberculosis H37Rv from American Type Culture Collection (ATCC) 27294 using the macrodilution or microdilution methods to evaluate the Minimum Inhibitory Concentration (MIC) which was evidenced by the colourimetric assay of 3 - (4,5 - dimethylthiazol-2-yl) -2,5-diphenyl tetrazolium bromide (MTT). Killing curves were performed to determine the bactericidal effect of the substances considered as promising with lower MICs. The tests were run with isoniazid and rifampin as control drugs. Additionally, growing control and sterility of the culture medium control were included. RESULTS: Both, natural and synthetic substances showed bioactivity against M. tuberculosis within the range of concentrations tested. 3 of 15 analyzed molecules were bioactive with MICs between 50.8 and 100 mg / mL and the other 12 were not bioactive. The extracts from Salvia officinalis, Escallonia pendula and Lippia origanoides were bioactive with MICs between 793.70 and 1000μg/mL. There was no evidence of bioactivity of extracts from Baccharis aff. buddleioides, Nectranda calycina and Wedelia reticulata. The 14 essential oils showed bioactivity against the microorganism and the oils obtained from Eucalyptus citriodora Hook, Cymbopogon citratus, Cymbopogon flexuosus and Turnera diffusa were considered as promising (MICs between 31.25 and 100 µg / mL). The killing curves indicated a bactericidal effect of C. citratus and T. diffusa with a ≥ 99% of bacterial death rate at day 6th of the assay. E. citriodora and C. flexuosus presented bacteriostatic effect. CONCLUSIONS: bactericidal activity showed from C. citratus and T. diffusa against M. tuberculosis support further research for the discovery and development of anti - TB agents. The bacteriostatic activity display by C. flexuosus and E. citriodora Hook suggest a promissory use of this extracts in various industrial nonpharmacological products. This research contributes to the study and characterization of biodiversity and the development of new active principles against diseases of public health concern as TB. The photo on the cover: A sickly female invalid sits covered up on a balcony overlooking a beautiful view, death (a ghostly skeleton clenching a scythe and an hourglass) is standing next to her; representing tuberculosis. Watercolour by R. Cooper. Iconographic Collections, Richard Tennant Cooper This file comes from Wellcome Images, a website operated by Wellcome Trust, a global charitable foundation based in the United Kingdom. Refer to Wellcome blog post.Library reference: ICV No 17400.Photo number: V0017058 Full Bibliographic Record: http://catalogue.wellcomelibrary.org/record=b1181863 https://commons.wikimedia.org/wiki/File:A_sickly_female_invalid_sits_covered_up_on_a_balcony_overloo_Wellcome_V0017058.jpg

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