Antibacterial activity of polysaccharide gel extract from fruit rinds of Durio zibethinus Murr. against oral pathogenic bacteria

Aim: The polysaccharide gel (PG) extract from durian fruit rinds (Durio zibethinus Murr. Monthong'') is a pectic polysaccharide with antibacterial activity. This study aimed to investigate the in vitro antibacterial activity of PG against oral pathogens, Streptococcus mutans (S. mutans) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans). Methods: The inhibitory activity of PG at 50, 100, and 150 mg/mL against S. mutans (American Tissue Culture Collection 25175) and A. actinomycetemcomitans (American Tissue Culture Collection 43718) was determined after 1-and 5-min exposure by broth macrodilution susceptibility test and scanning electron microscopy. Normal saline or culture broth medium and 0.1% chlorhexidine were used as negative and positive controls, respectively. Results: For 1-min exposure, 150 mg/mL PG or 0.1% chlorhexidine significantly possessed bactericidal activity against both tested bacteria (P = 0.037), while PG at 100 mg/mL possessed significant bactericidal activity against S. mutans (P = 0.037) and inhibitory activity against A. actinomycetemcomitans (P = 0.05). Blebs, irregular-shaped cells, and disrupted cells were found in bacteria treated with either 0.1% chlorhexidine or 50-150 mg/mL PG under scanning electron microscopy. Conclusion: The bactericidal activity of PG at 150 mg/mL against oral bacteria at 1-min exposure suggests its possibility to be used as a natural antibacterial ingredient in oral hygiene products.