IN VITRO ANTIMYCOBACTERIAL ACTIVITY OF TWO MEDICINAL PLANTS IDENTIFIED FROM NIGER STATE, NIGERIA

Abstract

The global threat of tuberculosis demands for search for alternative antimycobacterial drugs [1]. The crude methanolic extracts of eight Nigerian medicinal plant species used in the treatment of TB and other respiratory diseases were evaluated for activity against a clinical isolate of Mycobacterium tuberculosis and attenuated Mycobacterium bovis (BCG) using broth microdilution method. The plant parts used were obtained as described by the users from a forest near Baddegi, Niger State, Nigeria. Voucher specimens were deposited in the Herbarium at the Department of Biological Sciences, Ahmadu Bello University (ABU), Zaria, Nigeria and National Institute for Pharmaceutical Research and Development (NIPRD), Abuja, Nigeria. Two hundred grams (200g) of each dried plant material was powdered and extracted by maceration with methanol for 72h at room temperature (3 x 250mL). All the crude extracts were filtered and evaporated in vacuo (350C). Each extract was then partitioned with n-hexane-MeOH (3 x 250mL, 1: 1) to give n -hexane and MeOH solubles as well as all the partitioned extracts for each plant were combined; concentrated and dried in vacuo. Both hexane and methanol extracts of each plant species were tested for antimycobacterial activity. Four out of the eight plant extracts exhibited inhibitory activities against Mycobacterium tuberculosis at 78 and 1250μg/mL [2]. The hexane fractions obtained after fractionation were the most active fractions for all the plants tested against BCG, having Anogeissus leiocarpus and Terminalia avicennioides exhibiting the highest activity at 312 and 200μg/mL respectively. Fractions Ta5 and Al4 obtained on further purification exhibited most significant activity (MIC 4.7μg/mL, 7.8μg/mL) respectively. From the results of phytochemical analysis, terpenes and triterpenoid saponins are the most prominent compounds in these fractions and several reports earlier indicated that these metabolites are potential antimycobacterial agents [1]. This class of metabolites presents interesting area for further investigation with special attention on the Combretaceae family from Nigeria flora. References: [1] Copp, BR: The Review of Natural Products with antimycobacterial activity. Nat. Prod. Rep., 20(6): 535-557. (2003). [2] Mann, A., Amupitan, J. O., Oyewale, A.O., Okogun, J. I., Ibrahim, K., Oladosu, P., Lawson, L., Olajide, I., and Nnamdi, A.: Evaluation of in vitro antimycobacterial activity of Nigerian plants used for treatment of respiratory diseases, Afri. J. Biotech., 7 (11): 1630-1636 (2008)