Beneficial efficacy of various propolis extracts and their digestive products by in vitro simulated gastrointestinal digestion

Propolis is a waxy substance from many plant material which is rich in polyphenols with numerous biological activities. The current experiment was designed to assess the antioxidant and cyclooxygenase-2 (COX-2) inhibitory activities of various propolis extracts and their digestive products on human oral carcinoma KB cells. Three different solvents like ethanol (EtOH), glycerol and water (before digestion; BD) as well as three different phases of in vitro simulated digestion (after digestion; AD) like oral (O), gastric (G) and gastrointestinal (GI) were used to mimic the human digestion model. Both phenolic and flavonoids contents, as well as antioxidant capacity, are significantly higher in EtOH extract than glycerol and water (BD). Whereas, the O phase of all solvent (AD) showed highest phenolic and flavonoids contents as well as antioxidant capacity than G or GI phase. Moreover, COX-2 protein expression was markedly downregulated on treatment with EtOH (BD) on oral carcinoma KB cells as compared to other extracts. Likewise, the addition of oral digested EtOH notably downregulated the COX-2 protein expression in oral carcinoma KB cells. In conclusion, the original (undigested) and oral digested propolis of EtOH showed perfect antioxidant and COX-2 inhibitory activity, owing to increased phenolic and flavonoids contents.