Separation and enrichment of phenolics improved the antibiofilm and antibacterial activity of the fractions from Citrus medica L. var. sarcodactylis in vitro and in tofu.

Separation and enrichment of phenolic components from Citrus medica L. var. sarcodactylis were performed to improve the antibiofilm and antibacterial activity/efficiency of the fractions for the first time. Through separation of the crude extracts, the preparation of four fractions was done by chromatography on macroporous resin. It was found that the antibiofilm and antibacterial activity of the fractions were significantly enhanced. The obtained 30% ethanol eluted fraction (EEF) and 60% EEF both significantly inhibited biofilm formation. After the second separation by polyamide resin chromatography, the activity of the fractions was also improved. Complete inhibition (100%) on biofilm formation of S. aureus was achieved at 2.0 mg/mL. The MIC of the fractions on S. aureus was decreased to 2.0 mg/mL. There has been variation of 7.3-185.6 mg/g of phenolic content in the fractions, and a strong correlation between the anti-biofilm, the antibacterial activity and the phenolic content. Chemical composition analysis showed the EEF comprised 17 phenolic compounds. Moreover, the obtained EEF exhibited much higher antibacterial activity in tofu than crude extract. Therefore, chromatography separation significantly improved the antibacterial and antibiofilm activity/efficiency of the fractions both in vitro and in tofu.