In the doctoral dissertation we have studied the efficiency of various extraction methods in the extraction of tannins. Additionally, we have studied changes and synthesis of proanthocyanidins and other phenolic compounds during fruit ripening. The content of tannins was measured in different plant parts: leaves, fruits and seeds and in various fruit species: apples, medlar, persimmon, quince, hazelnut and walnut. The studies encompassed analyses of phenolic compounds using high-pressure liquid chromatography coupled with mass spectrometry (HPLC-MS). Enzymatic activity was analyzed by using radiographic TLC scan and relative gene expression was determined with RT-qPCR method. Our results have shown optimized proanthocyanidin extraction from quince leaves at higher temperatures. In firm and mellow medlar fruit, optimal extraction was achieved with 100% acetone and 100% methanol, but the efficiency of solvent was highly dependent on the ripening stage and tissue type. We have studied the changes in tannin content in two cultivars of persimmon during ripening in various conditions. We have confirmed the possibility of polymerization and/or interaction of proanthocyanidins with compounds from the cell wall during ripening of persimmon. The accumulation of phenolic compounds was detected in walnut pellicle during fruit ripening. However, the content of phenolic compounds decreased in walnut kernel. Proanthocyanidin synthesis pathway was studied in a red-pellicle walnut and no competition for substrates in synthesis of proanthocyanidins and anthocyanidins was detected. High content of phenolic compounds in the pellicle of red walnut fruit is the result of increased activity of PAL enzyme and high expression of PAL and ANS genes.
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