Antioxidant, Antidiabetic, and Anti-Obesity Properties of Apple Pulp Extracts (Malus domestica Bork): A Comparative Study of 15 Local and Commercial Cultivars from Spain

SIMPLE SUMMARY: Apples are one of the most important fruits worldwide. In addition to their interesting nutritional value, they are a source of bioactive compounds with health-promoting effects. The composition may differ in different genotypes so it is important to investigate whether local varieties may differ in terms of total phenolic content, antioxidant, and bioactive properties. In this study Spanish local varieties showed better behavior in terms of phenolic content, antioxidant activity and bioactivity than other commercial samples, acting as functional foods with antiradical, antidiabetic and anti-obesity potential. ABSTRACT: Apples (Malus domestica Borkh.) have a great agricultural and economic impact worldwide; they also present an interesting nutritional value, and their consumption has been associated with beneficial health effects. In this study, 15 apple varieties (three commercial, 12 autochthonous genotypes) were collected from mountainous areas in Spain and were evaluated for their phenolic content, antioxidant, anti-obesity and antidiabetic activities. Quercetin was tested as the reference substance in bioassays due to its role as one of the most common flavonoids in apples and other vegetables. Total Phenolic Content (TPC) of apple pulp extracts was quantified using the Folin-Ciocalteu method. The antioxidant activity was determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging and xanthine/xanthine oxidase (X/XO) scavenging assays. Antidiabetic and anti-obesity potential were evaluated by inhibition of alpha-glucosidase (α-GLU), advance glycation end products (AGEs) formation and pancreatic lipase. The results showed in general higher phenol content in autochthonous varieties than in commercial apple pulp extracts. Phenolic-rich extracts showed better antioxidant profiles and significantly inhibited AGEs production and the α-glucosidase enzyme in a dose-dependent manner. None of them showed pancreatic lipase inhibitory effects but in general, the genotype known as “Amarilla de Octubre” was the best in terms of TPC and bioactive properties.