Quercetin in a lotus leaves extract may be responsible for antibacterial activity

In the course of a search for chemotherapeutic agents inhibiting suspected peridontitis bacteria, extracted and purified substances from lotus leaf were identified by antimicrobial activity tests with use of the broth micro-dilution methods on 96-microwell plate. The antimicrobial activity of extracts was tested against five microorganisms, namely: Actinobacillus actinomycetemcomitans Y4, Actinomyces viscosus 19246, Porphyromonas gingivalis 33277, Fusobacterium nucleatum 25586, and Actinomyces naeslundii wvl 45. The most active antimicrobial extract was subjected to spectroscopic analysis using UV, mass spectrometry, and by H-1, C-13-, nuclear magnetic resonance spectroscopy. Our data showed that the minimum inhibitory concentrations of the most active extract were 0.625, 1.25, 1.25, 0.625 and 2.5 mg/mL for A. actinomycetemcomitans, A. viscosus, P. gingivalis, F. nucleatum, and A. naeslundii, respectively. The component that had a greatest antimicrobial activity was determined to be quercetin. Thus, we conclude that quercetin extracted from lotus leaves may be a potential antibacterial agent for periodontitis.