Allicin from garlic neutralizes the haemolytic activity from pneumococcal diseases. - GreenMedInfo Summary

Pneumolysin (PLY) is a key virulence factor contributes to the pathogenesis of Streptococcus pneumoniae. In this study we investigated the effect of allicin and aqueous garlic extracts on haemolytic activity of PLY both in prelysed and intact cells. Additionally the antimicrobial activity of allicin was tested against the bacteria. All tested materials potently inhibited the PLY haemolytic activity. Allicin neutralizes PLY in a concentration- and time-dependent manner. Twenty five minute incubation of PLY (2 HU/mL) with 0.61μM/mL concentration of allicin, totally inhibited haemolytic activity of PLY (IC50 = 0.28 μM/mL). The inhibitory activity of old extract of garlic was similar to pure allicin (IC50 = 50.46 μL/mL; 0.31 μM/mL; P<0.05). In contrast fresh extract of garlic inhibits the PLY haemolytic activity at lower concentrations (IC50 = 13.96μL/mL; 0.08 μM/mL allicin). Exposure of intact cells to allicin (1.8 μM) completely inhibited haemolytic activity of PLY inside bacterial cells. The inhibitory effect of the allicin was restored by addition of reducing agent DTT at 5 mM, proposing that allicin likely inhibits the PLY by binding to cysteinyl residue in the binding site. The MIC value of allicin was determined to be 512 μg/mL (3.15 μM/mL). These results indicate that PLY is a novel target for allicin and may provide a new line of investigation on pneumococcal diseases in the future.