Antimicrobial activity of a protein purified from the latex of Hevea brasiliensis on oral microorganisms

This study aimed at screen for antimicrobial activity present in the non-rubber constituents of rubber latex of Hevea brasiliensis against various microbial strains. An antimicrobial protein, hevein was extracted from the bottom fraction after centrifugation and purified by acetone fractionation and anion exchange chromatography on a DEAE-Sepharose Fast Flow column. This procedure was more efficient and rapid than the previously described procedures. The antimicrobial activity was investigated and revealed that hevein, a small (4.7 kDa) cysteine-rich protein, had strong antimicrobial activity, especially against Candida spp. including Candida albicans, Candida tropicalis and Candida krusei. The MIC80 value for hevein was as low as 12 mu g ml(-1) with C. tropicalis ATCC 750. Higher MIC80 values were obtained for C. albicans ATCC 10231 (95 mu g ml(-1)) and C. krusei ATCC 6258 (190 mu g ml(-1)). To confirm the antifungal activity, hevein also inhibited the growth of those fungi in a disk diffusion assay and its inhibition was enhanced when a Hevea latex protease inhibitor was also included. Hevein at a concentration of 30 mu g ml(-1) also caused a Ca2+-dependent aggregation of C. tropicalis yeast cells. These data indicate that hevein can inhibit the growth of certain potential oral fungal pathogens.