In vitro bioaccessibility of phenolics and flavonoids in various dried vegetables, and the determination of their antioxidant capacity via different spectrophotometric assays

In the present work, the in vitro bioaccessibility of total phenolic content (TPC), total flavonoid content (TFC) and total antioxidant capacity (TAC) of 13 dried vegetables were determined. The dried vegetables analysed were eggplant, dill, red pepper, green pepper, celery leaves, parsley, zucchini, tomato, onion, leek, garlic, white cucumber and string beans. Three different TAC determination methods (ABTS, DPPH, CUPRAC) were performed for this purpose. According to the results; prior to in vitro digestion, eggplant yielded the highest TAC and TFC values in all assays. In addition, eggplant and red pepper yielded the highest TPC (p > 0.05). Following in vitro digestion, dill yielded the highest TAC in DPPH assay, while celery leaves yielded the highest TAC in ABTS and CUPRAC assays from IN sample. Dill also yielded the highest TFC, while white cucumber and zucchini yielded the lowest. TPC was found the lowest value in string beans while it was the highest in red pepper. The highest bioaccessibility of both TPC (85%) and TFC (86%) were determined in garlic, while eggplant had the lowest TPC, TFC and TAC (≤ 10%) bioaccessibility. Maximum TAC bioaccessibility (%) of IN samples was determined in garlic in ABTS (30%) and CUPRAC (720%) assays; and zucchini (127%) in DPPH assay. The present work provides valuable data on the effect of in vitro gastrointestinal digestion on phenolic content, flavonoid content and antioxidant capacity of 13 types of dried vegetables.