Abstract
BackgroundTuberculosis is counted amongst the most infectious and lethal illnesses worldwide and remains one of the major threats to human health. The aim of the current study was to isolate and characterize anti-mycobacterial compounds present in Curtisia dentata (Burm.f.) C.A.Sm, a medicinal plant reportedly used in the treatment of tuberculosis, stomach ailments and sexually transmitted infections.MethodsThe bioassay guided principle was followed to isolate the anti-mycobacterial compounds. The crude ethanol extracts of the leaves was partitioned with various solvents four compounds such as β-sitosterol, betulinic acid, ursolic acid and lupeol were successfully isolated. The compounds and their derivatives were evaluated for anti-mycobacterial activity using Microplate Alamar Blue Assay (MABA) against Mycobacterium tuberculosis H37RV (ATCC 27294). Furthermore, the derivatives were investigated for their toxicity against HepG2 and HEK293 using the MTT assay.ResultsThe methanol fraction had the lowest minimum inhibitory concentration (MIC) of 22.2 μg/ml against the selected Mycobacterium strain when compared to other fractions. Ursolic acid acetate (UAA) was the most active compound with MIC value of 3.4 μg/ml. The derivatives had varying degrees of toxicity, but were generally non-toxic to the selected cell lines. Derivatives also exhibited highest selectivity index and offers a higher safety margin.ConclusionsThe derivatives had better antimicrobial activity and low cytotoxic effects compared to isolated compounds. These increased their selectivity. It appears that acetylation of both betulinic acid and ursolic acid increased their activity against the selected Mycobacterium species. The results obtained in this study gives a clear indication that Curtisia dentata may serve as major source of new alternative medicines that may be used to treat TB. Furthermore, there is a need to explore the activity of these tested plant against other pathogenic Mycobacterium species.
Highlights
Tuberculosis is counted amongst the most infectious and lethal illnesses worldwide and remains one of the major threats to human health
Western methods of healing may be preferred by modernized individuals, the traditional medicines still serve as a primary health care system preferred in developing countries
The methanol fraction was the most active with minimum inhibitory concentration (MIC) of 22.2 μg/ml; this is followed by acetone extracts with minimum inhibitory concentration of 44.2 μg/ml
Summary
Tuberculosis is counted amongst the most infectious and lethal illnesses worldwide and remains one of the major threats to human health. Three million people die due to tuberculosis (TB) each year. This renders the disease a major public health problem [1]. Several drugs such as rifampicin, isoniazid, ethambutol and pyrazinamide have been used in the treatment of TB over a period of six months [2]. There is an increase in the investigations of anti-tubercular activity of plant extracts and isolated compounds from various medicinal plants [15,16,17,18,19,20]. Little is known about the mode of action of such extracts and the efficacy of derivatives of such compounds against various tuberculosis agents
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