Antimicrobial efficacy of Acacia nilotica, Murraya koenigii L. Sprengel, Eucalyptus hybrid, and Psidium guajava on primary plaque colonizers: An in vitro comparison between hot and cold extraction process

BACKGROUND: The potential drawbacks of the existing antiplaque agents call for innovative strategies that are safe, effective, and easily available. OBJECTIVE: The objective was to assess and compare antimicrobial efficacy of four plant extracts derived using hot and cold extraction methods against Streptococcus mutans, Streptococcus sanguis, and Streptococcus salivarius. MATERIALS AND METHODS: The leaves of Acacia nilotica, P. guajava, Eucalyptus hybrid, and Murraya konigii L. Sprengel were collected from the surrounding areas, identified and authenticated by a taxonomist. The leaves were washed, shade-dried, and hand crushed to obtain coarse powder. This was subsequently ground into a fine powder and extracted using ethanol by cold infusion and hot extraction process. The antimicrobial efficacy testing was done on American Type Culture Collection strains of S. mutans, S. sanguis, and S. salivarius using agar well diffusion method. 0.2% chlorhexidine and dimethyl sulfoxide were used as positive and negative controls. The mean inhibition zone using 10% concentration of these extracts was compared using independent sample t-test and one-way analysis of variance. RESULTS: All the four plant extracts inhibited the growth of S. mutans, S. sanguis, and S. salivarius irrespective of the method of extraction. The extracts of A. nilotica, P. guajava, and E. hybrid derived from both the methods of extraction exhibited a significantly higher inhibition zone against S. mutans in comparison with Murraya koenigii L. Sprengel and chlorhexidine. The cold extracts of A. nilotica and E. hybrid exhibited higher zone of inhibition against S. sanguis while the hot extracts of M. koenigii L. Sprengel exhibited a higher zone of inhibition against S. mutans. CONCLUSION: All the four plant extracts derived using either hot or cold extraction were effective against these bacteria and have the potential to be used as antiplaque agents.