Bactericidal activity was found in the 50% ethanol (v/v) extract of Streblu
s asper leaves. The extract possessed a selective bactericidal activity tow
ards Streptococcus, especially to Streptococcus mutans which has been shown
to be strongly associated with dental caries. The extract-had no effect on
cultures of Escherichia coli, Staphylococcus aureus and Pseudomonas aerugi
nosa, Staphylococcus coagulase positive, Staphylococcus coagulase negative,
Serratia marcescens, Klebsiella pneumoniae, Enterobacter, Pseudomonas aeru
ginosa, Burkholderia pseudomeallei and Candida albicans. The minimum growth
inhibitory concentration and the minimum bactericidal concentration of S.
asper extract against 10(8) CFU/mL of S. mutans was 2 mg/mL. The active com
pound is partially polar, partially heat labile, precipitated by 80% ammoni
um sulphate, and possesses a molecular weight larger than 10000 Da. The pot
ential for using S. asper extract as a natural product for controlling dent
al caries is discussed. Copyright (C) 2001 John Wiley & Sons, Ltd.