Novel anti-adherence activity of mulberry leaves: inhibition of Streptococcus mutans biofilm by 1-deoxynojirimycin isolated from Morus alba

Abstract

<sec><st>Objectives</st> The present study focused on isolation, characterization and evaluation of purified compounds from <it>Morus alba</it> against <it>Streptococcus mutans</it> biofilm formation. </sec> <sec><st>Methods</st> The effect of crude extract from <it>M</it>. <it>alba</it> leaves was evaluated against oral pathogens, chiefly <it>S</it>. <it>mutans</it>. MICs were determined by the microdilution method. The compound was purified by employing silica gel chromatography and critically analysed with GC–MS, NMR and IR spectroscopy. The <it>S</it>. <it>mutans</it> traits of adherence and biofilm formation were assessed at sub-MIC concentrations of the crude extract and purified compound. Both water-soluble and alkali-soluble polysaccharide were estimated to determine the effect of the purified compound on the extracellular polysaccharide secretion of <it>S</it>. <it>mutans</it>. Its effect on biofilm architecture was also investigated with the help of confocal microscopy. </sec> <sec><st>Results</st> The purified compound of <it>M</it>. <it>alba</it> showed an 8-fold greater reduction of MIC against <it>S</it>. <it>mutans</it> than the crude extract (MICs, 15.6 and 125 mg/L, respectively). The extract strongly inhibited biofilm formation of <it>S</it>. <it>mutans</it> at its active accumulation and plateau phases. The purified compound led to a 22% greater reduction in alkali-soluble polysaccharide than in water-soluble polysaccharide. The purified compound was found to be 1-deoxynojirimycin (DNJ). Confocal microscopy revealed that DNJ distorts the biofilm architecture of <it>S</it>. <it>mutans</it>. </sec> <sec><st>Conclusions</st> The whole study reflects a prospective role of DNJ as a therapeutic agent by controlling the overgrowth and biofilm formation of <it>S</it>. <it>mutans</it>. </sec>