There are three main reasons for doing screening studies i.e. to find new lead compounds for developing pharmaceuticals, to confirm the ethnomedicinal use of plants or to develop phytomedicines for use as herbal medicine. Apparently, little effort has gone into developing low technology techniques to use medicinal plants in rural communities. In many screening studies, activities are reported non-quantitatively. Shale et al (1999) for example used agar diffusion assay for antibacterial activity and classified plants with a 0–0.3 mm, 0.3–0.7 mm and 0.7–1.0 mm zone of inhibition as having low, medium and high activity. Even if data on extracts are expressed in quantitative terms such as antibacterial activity in minimum inhibitory concentration (MIC) or anti-oxidant activity in trolox equivalent it is usually still not possible to compare different plants with the results presented.