he results shown in Tables 2, 3, and 4 pointed to better sensibility of diffusion method variant well rather than variant disc. Besides, additional arguments are in favor of the preferential use of the first variant for the screening of natural products with antibacterial activity. The hole plate method is the only suitable diffusion technique for testing aqueous suspensions of plant ethanol extracts (20). In this method, the presence of suspended particulate matter in the sample being tested is much less likely to interfere with the diffusion of the antimicrobial substance into the agar than in the filter paper disc. Precipitation of water-insoluble substances in the disc will indeed prevent any diffusion of antimicrobial substances into the agar. Little time consuming and simplicity are stimulating reasons for the use of diffusion method variant well rather than variant disc. In general, both diffusion method variants are similar to each other in terms of cost, although discs variant may be a little more expensive because of the price of paper filter Whatman, which is composed of cellulose [b-(1-4) linked glucose monomers]. The many free hydroxyl groups present on each glucose residues renders the surface of the disc hydrophilic (3). Thus, if natural products were cationic, they would be expected to adsorb to the surface of the disc and not diffuse into the medium. Consequently, a cationic polar compound may display a good antibacterial activity, but which is therefore not noticeably antibacterial by paper disc diffusion method. Apolar compounds would not be influenced by the hydroxyls on the surface of the paper and would diffuse easily. Thus, in this case, well agar diffusion method is more convenient than the disc variant. This theory explains at least in part, the higher sensitivity detected by well agar diffusion method. Also, the fact that the well variant yielded larger growth inhibition zones might be related to natural products transport by carrier compounds such as DMSO, for it is expected that they diffuse easily across the medium.