Screening for antimycobacterial activity of plants used in traditional medicine

Tuberculosis is a disease mainly caused by Mycobacterium tuberculosis. It is estimated that one-third of the world's population is infected with tuberculosis bacillus and two million people will develop an active disease per year. The increasing prevalence of the disease is due to the emergence of multidrug-resistant strains as well to the HIV pandemic which provides a large reservoir of highly susceptible individuals [1]. Since no anti-tuberculosis drugs have been introduced in the past 30 years, there is an urgent need for new effective anti-mycobacterial agents to circumvent new drug resistance cases. In this instance, the plant kingdom is undoubtedly a valuable source for new potential anti-tuberculosis agents to be explored [2].

According to WHO, almost 65% of the global population uses medicinal plants for primary health care [3]. The scientific evaluation of plants used by traditional healers becomes an urgent need [4]. In this study, the crude extracts from different parts of seven plants from Mozambique, used to treat respiratory disorders in traditional medicine, were screened for their ability to inhibit the growth of Mycobacterium smegmatis. From those plants, the methanolic extract and resulting fractions from the bark of Cassia abbreviata Oliver (Leguminosae) showed significant inhibitory activity when tested both by disc and wells diffusion methods. Three milligrams of each extract were applied on the discs/wells. Rifampicin was used as a positive control (30µg). The inhibition zones of the tested extracts oscillate between 10 and 27.5mm, and the positive control showed an inhibition zone of >19mm. The screening of the ability of those extracts to kill intracellular bacteria in macrophages, including pathogenic species such as Mycobacterium tuberculosis and M. avium is under progress. TLC analysis of the extracts, using the diphenylboric acid 2-aminoethylester reagent, revealed the presence of phenolic compounds as a major group of constituents.

References: [1] Pauli, G.F. et al. (2005) Life Sci. 78: 485–494. [2] Gautam, R. et al. (2007) J Ethnopharmacol. 110: 200–234. [3] Molina-Salinas, G.M. et al. (2006) Arch Med Res. 37: 45–49. [4] Eldeen, I.M. et al. (2005) J Ethnopharmacol. 102: 457–464.