Antioxidant Synergy Of Osmanthus Fragrans Flower With Tea And Bioactive Compounds By In Vitro Digestion-dialysis And Prieto’s Interaction Model

Edible flowers are rich in phenolic compounds and thus possess pretty good antioxidant activities. Osmanthus fragrans flower, with a long history of compution, is the favoured drink when brewed with tea. There is antioxidant synergy between tea polyphenols and many antioxidants. However, no study has reported the antioxidant synergy between tea and O. fragrans flower, which showed great antioxidant activity. Therefore, based on the in vitro digestion-dialysis model, the research compared phenolic compounds and antioxidant activities among 10 edible flowers from China, evaluated the antioxidant synergy between O. fragrans flower and tea from the level of "point", "line" and "surface" and find out the compound with the biggest contribution to synergy. Main research contents and results of this research are as follows:1. Based on the in vitro digestion-dialysis model, phenolic compounds, and chemical and cellular antioxidant activities of 10 common edible flowers from China were evaluated.These 10 edible flowers were rich in phenolic compounds (gallic acid, ferulic acid, rutin, et al.) and had strong antioxidant activities. Rosae rugosae, Paeonia suffruticosa, and Osmanthus fragrans possessed the highest total phenolic contents without significant difference, with the value of 29.97mg CAE/g DW,28.10mg CAE/g DW and 26.48mg CAE/g DW, reppectively. Meanwhile, these 3 flowers exhibited the best activity to scavenge DPPH and ABTS free radical, Ferric reducing power and cellular antioxidant activity.2. Based on the in vitro digestion-dialysis model, interaction effects between O. fragrans flower and tea with various fermentation degrees (green, oolong, black and dark tea) at 5 different ratios were evaluated by the contour graphic method from the level of "line". The tea with the best antioxidant synergy was screened out, and thus used to analyze the synergetic protection on HepG2 cells under oxidative stress by the method of direct comparison from the level of "point".O. fragrans flower with green tea exhibited the best antioxidant synergy in scavenging DPPH and ABTS free radical, expecially at the ratio of 4:1. When compared with 1:1 and 7:1,O. fragrans flower with green tea at the ratio of 4:1 showed the best antioxidant synergy in promoting the proliferation, inhibiting the apoptosis and the production of ROS in HepG2 cells under oxidative stress. Morever, the synergy effect could be easier observed at relatively lower concentrations.3. LC-MS was used to qualify the main functional compounds in O. fragrans flower and green tea, respectively. Based on bioaccessibility, mian functional compounds in O. fragrans flower with green tea at the ratio of 4:1 were quantified by UPLC-PDA.The nine main functional components in green tea were gallic acid(GA), catechin(C), L-epicatechin(EC), (-)-epigallocatechin(EGC), (-)-epigallocatechin gallate(EGCG), (-)-epicatechin gallate(ECG), (-)-gallocatechin gallate(GCG), (-)-gallocatechin(GC) and caffeine, respectively. The five main functional components in O. fragrans flower were acteoside, isoacteoside, chlorogenic acid and caffeic acid, respectively. Acteoside and caffeine were abundant in O. fragrans flower with green tea at the ratio of 4:1.4. After selecting compounds with good antioxidant activity in O. fragrans flower with green tea, based on the in vitro digestion-dialysis model, Prieto’s synergy quantification model was used to evaluate the antioxidant interaction effects between compounds in O. fragrans flower and green tea from the level of "surface", and find out compounds that made best contribution to synergy.12 kinds of compounds in O. fragrans flower with green tea exhibited good antioxidant activity. Antioxidant synergy was generally observed between bioactive compounds in O. fragrans and green tea, which could be reflected in the antioxidant synergy between O. fragrans flower and green tea. Generally, among main compounds in O. fragrans flower, chlorogenic acid showed the best antioxidant synergy with green tea and 8 kinds of compounds in green tea. Among main compounds in green tea, ECG showed the best antioxidant synergy with 4 kinds of compounds in O. fragrans flower. Morever, among 12 kinds of compounds in O. fragrans with green tea, acteoside made the greatest contribution to antioxidant synergy.