**4. Medicinal plants with demonstrated anti-tuberculosis activity**

 Tuberculosis (TB) is an airborne infectious disease which does not only affect the lungs but also other parts of the body such as the brain and spine [52]. The main cause of TB is *Mycobacterium tuberculosis*. Other *M. tuberculosis* complex that causes TB include *M. bovis*, *M. africanum*, *M. canetti* and *M. microti* [53]. The predominant symptoms of active TB are fever, night sweat, weight loss and chronic cough with blood containing sputum. However, most TB infections are latent which may progress into active disease if left untreated [52]. Treatment of TB is very tedious and requires a long course with multiple antibiotics involved. However, this fastidious bacteria have become resistant to most antibiotics, and hence researchers are working tirelessly to come up with new and effective products especially from natural products such as medicinal plant. Some medicinal plants that have been investigated to possess active anti-tuberculosis activity are reviewed below.

#### **4.1** *Anogeissus leiocarpa*

 *A. leiocarpa* (Combretaceae) commonly called African birch is a tall deciduous tree which is indigenous to the savannas of tropical Africa. Traditionally, its stem and root barks are used to treat gonorrhea, worm infestation, cough, asthma and tuberculosis [54]. The susceptibility of clinical isolates of *M. tuberculosis* to the methanolic extract of *A. leiocarpa* was investigated using the broth dilution method. The results demonstrated anti-mycobacterial property (MIC 78 μg/mL). *A. leiocarpa* fraction showed an increased anti-mycobacterial activity (MIC 7.8 μg/mL) [55].

#### **4.2** *Terminalia avicennioides*

*T. avicennioides* (Combretaceae) is a tree commonly found in West Africa. Its root bark, fruit and mistletoes are used traditionally to treat diarrhea, hemoptysis, sore throat, TB, asthma and cough [54]. The *in vitro* antibacterial studies using broth dilution method of methanolic extract of *T. avicennioides* showed a significant antimycobacterial activity (MIC 78 μg/mL) against clinical isolates of *M. tuberculosis.*  The n-hexane and ethyl acetate fractions obtained from the crude methanol extract of *T. avicennioides* showed inhibitory activity (MIC 200 and 625 μg/mL, respectively) against attenuated strains of *M. bovis*. A further study of *T. avicennioides*  fraction obtained demonstrated anti-mycobacterial activity (MIC 4.7 μg/mL) [55].

#### **4.3** *Capparis brassii*

*C. brassii* (Capparidaceae)*,* the narrow-leaf caper bush is distributed in the coastal forest and mixed woodland from tropical West Africa to South-East Africa. The root bark is used to treat TB in folk medicine [54]. The methanol extract of *C. brassii* has demonstrated some level of anti-mycobacterial activity (MIC 1.25 mg/mL) against clinically isolated strains of *M. tuberculosis* [55].

#### **4.4** *Combretum* **spp.**

*Combretum* (Combretaceae) commonly called the bush willows has about 370 species of shrubs and trees, predominant in southern and tropical Africa, Madagascar, Asia and tropical America. Traditionally, its root and stem barks are used to treat cough, bronchitis and TB [54]. The methanol extract exhibited antimycobacterial activity (MIC 1.25 mg/mL) against *M. tuberculosis* clinical isolates when evaluated in vitro using the broth microdilution method [55].
