In vitro antimycobacterial activity of six Cameroonian medicinal plants using microplate alamarBlue assay

AbstractObjective/backgroundThe latest incidence of tuberculosis (TB) (per 100,000 people) in Cameroon was 243.00 as of 2011. Over the past 21years, the value for this indicator has fluctuated between 112.00 in 1990 and 320.00 in 2003. Worldwide, this incidence has also increased, bringing back TB as a reemerging disease. On the same note, resistance to anti-TB drugs has increased, urging the search for new molecules.MethodsThis study was carried out to evaluate the antimycobacterial activity of six medicinal plants on the virulent strain, H37Rv, using the microplate alamarBlue assay. Mycobacterium tuberculosis (H37Rv strain) was incubated with decreased concentrations of six plant extracts, ranging from 250μg/mL to 31.25μg/mL. After 7days of incubation at 37°C, the effects of these plant extracts on the viability of the mycobacteria were evaluated. For each plant extract, the minimal inhibitory concentration was determined.ResultsThe results showed that the compounds MBC1, MBC24, MBC68, MBC81, MBC117, and MBC118 were the best candidates with minimal inhibitory concentrations of 31.25, 62.5, 125, 62.5, and 125μg/mL, respectively.ConclusionThese results confirm and validate the traditional use of these plants to treat respiratory diseases, which could be good sources and alternatives of plant metabolites for anti-TB-drug development

Anti-mycobacterial activity of polyketides from Penicillium sp. endophyte isolated from Garcinia nobilis against Mycobacterium smegmatis

Objective/background: According to estimates by the World Health Organization, there were 9.6 million new tuberculosis (TB) cases in 2014: 5.4 million among men, 3.2 million among women, and 1.0 million among children. There were also 1.5 million TB deaths. Although there are potent anti-TB molecules, the misuse of these drugs in addition to inconsistent or partial treatment have led to the development of multidrug-resistant TB and extensively drug-resistant TB. It is established that plants harbor microorganisms, collectively known as endophytes, which also produce metabolites. Exploring the as-yet untapped natural products from the endophytes increases the chances of finding novel and active compounds. The present study was aimed to investigate the antimycobacterial activity of the crude extract and compounds isolated from Penicillium sp. endophyte associated with Garcinia nobilis against Mycobacterium smegmatis. Methods: Liquid culture obtained from the fermentation of Penicillium sp. was extracted using ethylacetate and the liquid chromatography–mass spectrometry monitored fractionation of crude extracts yielded six compounds. Their structures were elucidated with spectroscopic analyses including two-dimensional nuclear magnetic resonance, high resolution mass spectrometry by dereplication using Antibase, and by comparison to literature data. All compounds and the crude extract from the liquid medium were evaluated for their antimycobacterial activity against M. smegmatis. Results: In this study, the activity of penialidins A–C (1–3), citromycetin (4), p-hydroxy phenyl glyoxalaldoxime (5), and Brefeldin A (6) were tested against nonpathogenic M. smegmatis. Penialidin C was the most active compound with a minimum inhibitory concentration of 15.6μg/mL. Conclusion: Isolated compounds from Penicillium sp. harbored in G. nobilis exhibited promising antimycobacterial activity against M. smegmatis thus supporting the immensity of the potential of antimycobacterial drug discovery from endophytes from medicinal plants. Penialidin C could further be investigated for antimycobacterial drug development