Le. Wolinsky et al., THE INHIBITING EFFECT OF AQUEOUS AZADIRACHTA-INDICA (NEEM) EXTRACT UPON BACTERIAL PROPERTIES INFLUENCING IN-VITRO PLAQUE-FORMATION, Journal of dental research, 75(2), 1996, pp. 816-822
The purpose of this investigation was to examine the inhibitory effect
s of aqueous extracts derived from the bark-containing sticks (Neem st
ick) of Azadirachta indica upon bacterial aggregation, growth adhesion
to hydroxyapatite, and production of insoluble glucan, which may affe
ct in vitro plaque formation. Neem stick extracts were screened for mi
nimal bacterial growth inhibition (MIG) against a panel of streptococc
i by means of a broth dilution assay. Initial bacterial attachment was
quantified by the measurement of the adhesion of H-3-labeled Streptoc
occus sanguis to saliva-conditioned synthetic hydroxyapatite. The effe
ct of the Neem stick extract upon insoluble glucan synthesis was measu
red by the uptake of radiolabeled glucose from C-14-sucrose. Aggregati
ng activity of the Neem stick extracts upon a panel of streptococci wa
s also examined. No inhibition of bacterial growth was observed among
the streptococcal strains tested in the presence of less than or equal
to 320 mu g/mL of the Neem stick extract. The pre-treatment of S. san
guis with the Neem stick extract or the gallotannin-enriched extract f
rom Melaphis chinensis at 250 mu g/mL resulted in a significant inhibi
tion of the bacterial adhesion to saliva-conditioned hydroxyapatite. P
re-treatment of saliva-conditioned hydroxyapatite with the Neem stick
or gallotannin-rich extract prior to exposure to bacteria yielded sign
ificant reductions in bacterial adhesion. The Neem stick extract and t
he gallotannin-enriched extract from Melaphis chinensis inhibited inso
luble glucan synthesis. Incubation of oral streptococci with the Neem
stick extract resulted in a microscopically observable bacterial aggre
gation. These data suggest that Neem stick extract can reduce the abil
ity of some streptococci to colonize tooth surfaces.