Integrated Sugar–Acid–Phenolic Profiling Identifies Distinct Chemical Types Associated with Antioxidant Capacity in Apple Pulp Samples

This study characterized the sugar, organic acid, and phenolic profiles of 25 apple pulp samples from 12 cultivars to investigate their associations with antioxidant potential. Fructose and malic acid were the predominant free sugar and organic acid, respectively. Hierarchical clustering based on seven non-redundant chemical traits classified the samples into four distinct chemical types: acid-rich, sugar-enriched/low-phenolic, intermediate/low-accumulation, and phenolic-rich types. Phenolic-related traits showed stronger associations with in vitro antioxidant capacity than sugar- and acid-related traits. For cellular validation, polyphenol extracts from five representative samples were tested at 5 μg/mL, a concentration selected based on cell viability results under the tested conditions. The extracts significantly reduced H2O2- and t-BHP-induced intracellular ROS accumulation in HepG2 cells, with the TPGSH sample exhibiting the strongest cellular protection. These findings establish an integrated chemical–antioxidant framework for characterizing apple pulp samples and identifying compositional patterns associated with antioxidant activity.