The
preliminary screening of ethanol extracts of the plant materials
was performed by agar diffusion technique. The pH of the
crude extracts was adjusted to neutrality and different working
concentrations were prepared by serial dilution. All the
extracts showed varying degree of antimicrobial spectrum
against Streptococcus mutans. Samples were designated by from
S1 to S10 and different concentrations by upper case alphabetes
(A to G) by descending order. The result of preliminary
screening has been pooled in Table 1. S4 (S. oleracea), S6 (C.
longa), S9 (P. emblica) and S10 (T. indica), showed the most effectiveness
against S. mutans and obviously in the highest concentration
(100 mg/ml, designated as A). The samples S2 (A.
indica), S3 (V. negundo) and S7 (P. nigrum) showed the least acactivity.
All the samples showed reduction in antimicrobial activity
as the concentration were reduced and showed almost no
antibacterial effect beyond concentration of 12.5 mg/ml. Sample
S6 (C. longa) showed antibacterial effectiveness exceptionally
in concentration of 3.125 mg/ml (G). In this study, the inhibition
zone values were interpreted as sensitive (18 mm),
intermediate (14-17 mm) and resistant (