Sade ve süt eklenmiş yeşil çay ve yalancı iğde yaprağı çaylarının antioksidan özelliklerinin ve fenolik bileşiklerin in vitro biyoerişilebilirliklerinin karşılaştırılması

Green tea is a commonly recommended beverage for its strong antioxidant properties. On the other hand, sea buckthorn leaf tea also contains abundant amount of bioactive compounds. Present study focused on comparing the antioxidant properties and in vitro bioaccessibility of green tea and sea buckthorn leaf tea extracts. Green tea and sea buckthorn leaf tea samples were extracted with ethanol and also prepared in forms of tea infusions. Skimmed and whole milk (at room temperature) was added to get 20% and 40% (v/v) to tea infusions. In vitro gastrointestinal digestion model was used for investigating the bioaccessibility of samples. All samples were analyzed for their contents of total phenolics (TP) and total flavonoids (TF) as well as their total antioxidant capacity by using four different methods including 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzo-thiazoline-6-sulphonic acid) diammonium salt (ABTS), CUPRAC (Copper Reducing Antioxidant Capacity), and FRAP (Ferric Reducing Antioxidant Power) methods. According to TP the results, ethanolic extaction of green tea (EG) was richer in phenolic material (153.5 mg of GAE/ g sample) compared to ethanolic extraction of Sea buckthorn leaf tea (ES) (114.8 mg of GAE/g sample). On the contrary, sea buckthorn leaf tea (TS) had higher phenolic content than green tea (TS) considering that the tea infusion forms. In fact, the highest TP content among all fractions was observed in Ethanolic green tea extract (GE) (p<0.05). TP results of milk added samples were ranged between 43.6 to 58.4 mg GAE/g for SBT leaf tea and 37.8 to 44.9 mg GAE/g for green tea. Comparing the control group, whole and skimmed milk added samples, results showed that 20% whole milk added samples of SBT were increased compared to the 20% control group. However there were a decrease in 40% whole milk added samples. On the other hand there were a decrease in 20% skimmed milk added SBT and there were a little increase in 40% skimmed milk added samples of SBT. Considering the green tea samples, there were no significant variation between 20% of whole milk and control group samples while slight decreases were observed between control groups and 40% whole milk, 20% skimmed milk and 40% skimmed milk added samples. There were no significant difference between the TP of skimmed and whole milk added both green tea and SBT leaf tea samples, however, control groups were significantly higher than milk added samples (p<0.05). Total flavonoid (TF) of plain and milk added tea samples were measured colorimetrically in terms of both rutin and catechin equivalent and found to be higher rutin in EG (115.2 mg of Rutin eq./g) compared to ES (66.7 mg of RE/g). Also, the flavonoid content in TG (43.8 mg of RE/g) was higher than TS (39.9 mg of RE/g). Contrary the rutin content results, ES (35.0 mg of Catechin eq./g) and TS (14.0 mg of CE/g) were higher catechin content than EG (21.6 mg of CE/g) and TG (12.3 mg of CE/g). There was no significant difference between the TF of tea infusion forms both in terms of rutin and catechin, however, EG was significantly higher than ES in terms of rutin and ES was significantly higher than EG in terms of catechin (p<0.05). TF of milk added tea samples were observed range between 19.0 to 107.8 mg RE/g for SBT leaf tea and 30.8 to 88.4 mg RE/g for green tea. Also catechin equivalent results were observed range between 5.9 to 33.5 mg CE/g for SBT leaf tea and 9.6 to 27.5 mg CE/g for green tea. Both rutin and catechin results showed similar variation between control group and milk added samples of SBT leaf tea and green tea. There were only slight differences among the skimmed milk added sample and control group results. On the other hand, rapid increases were detected on the whole milk added samples. TAC was found to be higher in EG, ranging from 89.2 mg of TE/g for ABTS to 622.9 mg of TE/g for CUPRAC. For both SBT leaf tea and green tea, ethanolic extractions were more efficient to the total antioxidant capacity compared to tea infusions, having ~1.5-2.5 fold higher capacity. Thus, TAC for TG varied from 55.9-227.0 mg of TE/g, 89.1-456.1 mg of TE/g for ES and 55.7-251.3 mg of TE/g for TS. According to all four analyses carried out, TAC was decreased in 20% whole milk added samples both SBT leaf tea and green tea, respectively. Similarly TAC of 20% skimmed milk added samples decreased both SBT leaf tea and green tea except ABTS assay results. Considering the 40% milk added samples results, there were slight increase in both whole and skimmed milk added SBT leaf tea in DPPH assay. There were also slight increases in skimmed milk added green tea in ABTS assay. After the simulation of in vitro gastrointestinal digestion system, 18.1% and 8.3% of the antioxidant compounds were present in the dialyzed fraction for Sea buckthorn leaf tea and Green tea, respectively. Milk addition caused an increase in the dialyzed fractions for both tea samples. For milk added samples, percent recovery of total phenolics and total antioxidant capacity after in vitro GI digestion were significantly higher from control group samples whereas total flavonoid was found to be significantly lower except skimmed milk added samples of green tea.