Phenolic compounds and multifunctional properties of thinned apples: revalorizing fruit by-products for industrial applications

Thinned apples are a common by-product of apple orchards, produced in abundant quantities through thinning or natural drop, leading to the loss of substantial amounts of phenolic compounds with potential bioactive properties. Ten thinned apple samples, representing both commercial and autochthonous cultivars, were ultrasonicated using ethanol as green solvent, with the main goal of reusing their phenolic content for industrial and nutritional applications. For this reason, the phenolic content was characterized with high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The antioxidant, antidiabetic, and cardiovascular activities were evaluated and correlated with the targeted phenolic compounds. Under non-cytotoxic conditions in Caco-2, HepG2 and HFF-1 cells, Amarilla de Octubre and Pomera de Pomes Agrias showed the strongest antioxidant-antiglycation activity as well as ACE inhibition, while Reineta and Verde Doncella excelled in HMGR and ACE inhibition. Pomera de Pomes Agrias, Vadiello-02, Reineta and Verde Doncella led digestive enzymes under Caco-2 safety.