The effect of pH on the antibacterial activity of the ethanol extract of betel leaf was assayed following the method reported
Hoque et al.
59
previously by Shibata et al. (1995)28, and Ohno et al., (2003)29 with slight modification. The 50mM citrate-phosphate buffer (pH 5.0), 50mM Phosphate buffer (pH 7.0), 20mM Tris-HCl buffer (pH 9.0) and 20mM Glycine-NaOH buffer (pH 10.0) were used in this assay. All the buffers were sterilized by filter sterilization through 0.45mm membrane filter and stored at 4oC and used within 30 minutes after preparation.