Characterization of soluble and insoluble-bound polyphenols from Psidium guajava L. leaves co-fermented with Monascus anka and Bacillus sp. and their bio-activities

- Co-fermentation of Psidium guajava L. (PGL) leaves with Monascus and Bacillus promoted the release of bound polyphenolics.
- Soluble and insoluble-bound polyphenols from PGL was successfully identified.
- Soluble polyphenol from PGL exhibited higher antioxidant activities.
- Soluble polyphenol from PGL exhibited higher protective effect against DNA damage.
- Microbial co-fermentation way significantly increased the antioxidant capacities from PGL.

The leaves of Psidium guajava L. (PGL) were co-fermented with Monascus anka and bacillus sp. to promote the release of insoluble-bound polyphenol components. The variation tendency of polyphenols contents were tracked during fermentation. Polyphenol compounds from unfermented PGL (UPGL) and fermented PGL (FPGL) were identified by HPLC-TOF-ESI/MS. The antioxidant activities of polyphenols extracts from UPGL and FPGL were determined by different standard methods. The results indicated that total polyphenols and soluble polyphenols contents especially for quercetin were enhanced at the first 8 days of fermentation. Polyphenol extracts from FPGL had higher antioxidant than that from UPGL. Soluble polyphenol extracts exhibited higher antioxidant activity and protective effect against Fenton-induced DNA oxidative damage compared to insoluble-bound polyphenol extracts. This microbial co-fermentation way significantly increased the antioxidant capacities of soluble polyphenols from PGL. Our study provided a new way to upgrade polyphenols or other bioactive compounds with higher health beneficial effects.