Comprehensive Phenolic Profiling and Antioxidant Evaluation of Calyx, Rind, and Edible Tissues From Non-Astringent...

Persimmon (Diospyros kaki L.) processing generates substantial quantitiesof underutilized by-products despite their richness in bioactive compounds. This study evaluated the phenolic content, antioxidant potential, and phytochemical composition of four tissues (calyx, rind, pulp, inner pulp) from two non-astringent cultivars, namely, Fuyu and Jiro. Phenolic estimation (TPC, TFC, and TTC) and seven antioxidant assays (DPPH, ABTS⁺, ·OH-RSA, FRAP, RPA, TAC, and FICA) revealed strong tissue-specific variation. Calyx tissues displayed the highest phenolic concentrations and antioxidant activities, with Fuyu calyx showing the greatest TPC (38.98 mg GAE/g DW) and TTC (46.32 mg CE/g). Edible tissues exhibited substantially lower values, consistent with tannin insolubilization during ripening. Pearson's correlations showed strong associations between TPC/TFC and all antioxidant assays (r = 0.985-0.999), except FICA, which demonstrated weak negative correlations, highlighting method limitations for metal-chelating evaluation in persimmon matrices. LC-ESI-QTOF-MS/MS profiling identified 95 phenolic compounds across samples, including hydroxybenzoic acids, hydroxycinnamic acids, flavonoids, lignans, and stilbenes, with calyx tissues containing the greatest diversity. HPLC-DAD quantification confirmed gallic acid, catechin hydrate, and sinapic acid as key compounds, detected in Fuyu calyx. Overall, persimmon calyx represents a potent source of antioxidant phenolics with strong potential for valorization in functional food and nutraceutical applications.