Microbial bioconversion and processing methods enhance the phenolic acid and flavonoids and the radical scavenging capacity of Smilax china L. leaf

BACKGROUND: It has been reported that Smilax china L. leaf (SCL) provided various biological functions owing to polyphenols. The objective of the current study was to assess the enhancing effect of processing methods and microbial conversions on phenolic acid and flavonoid content and radical scavenging capacity of SCL for potential applications of diverse food products. RESULTS: Targeted phenolic acid (chlorogenic acid) and flavonoids (piceid and quercetin) were identified in fresh SCL using liquid chromatography-mass spectrometry. The total amount of identified phenolic acid and flavonoids was highest in steamed SCL (12.70+/-0.12mg g(-1) on a dry matter basis, dmb). A substantial amount of chlorogenic acid (5.81+/-0.16mg g(-1) dmb), piceid (3.96+/-0.04mg g(-1) dmb) and quercetin (6.06+/-0.12mg g(-1) dmb) were quantified in SCL fermented by Bacillus species, roasted and steamed, respectively (P < 0.05). The oxygen radical absorbance capacity (ORAC) value was greater in microbial fermented SCL than in others, with the exception of Saccharomyces cerevisiae and Aspergillus oryzae. However, vitamin C equivalent antioxidant capacity (VCEAC) was highest in SCL fermented by Aspergillus oryzae. CONCLUSION: Results from our study suggest that the microbial fermentation processing method could improve accessibility to extraction of phenolic acids and flavonoid content and radical scavenging capacity. (C) 2015 Society of Chemical Industry