(Poly)phenols of apples contribute to in vitro antidiabetic properties: Assessment of Canada's Apple Biodiversity Collection

Societal Impact Statement Apples are affordable and accessible fruit with tremendous biodiversity. Among over 10,000 identified apple cultivars, only a few are commercially available. Habitual fruit consumption is correlated with the prevention of Type 2 diabetes and related complications. Particularly, (poly)phenols found in apples are major contributors to their antidiabetic properties. Here, we have screened (poly)phenol-rich extracts of 476 apple accessions in Canada's Apple Biodiversity Collection for antidiabetic properties. The results of this work provide insights into the prevention and management of Type 2 diabetes by identifying high (poly)phenol-containing specialty apples for use in fresh fruit form or value-added functional food ingredients. Summary The recent trend in sedentary lifestyles and nutritionally-imbalanced diets has elevated the prevalence of Type 2 diabetes in many parts of the world. Some pharmacological glycemic management can cause undesirable gastrointestinal side effects or hypoglycemia. Thus, there is a growing interest in safe glycemic management using dietary (poly)phenols. In this study, (poly)phenol-rich extracts of 476 apple accessions from Canada's Apple Biodiversity Collection (ABC) and six major apple (poly)phenols were assessed for in vitro antidiabetic properties against the activities of alpha-glucosidase, alpha-amylase, and dipeptidyl peptidase-4 (DPP-4) and the formation of advanced glycation end products (AGE). Apple (poly)phenol extracts varied in their antidiabetic activities in a dose-dependent manner. High (poly)phenol-containing apples demonstrated that their total phenolic contents (TPC) were inversely correlated with the IC50 values of alpha-glucosidase, alpha-amylase, and AGE formation, but not DPP-4. Concentrations of major (poly)phenol compounds such as procyanidin B2, phloridzin, and epicatechin in apples were significantly inversely correlated with IC50 values of alpha-glucosidase in the high (poly)phenol-containing apples. High TPC apples are not suitable for marketing for fresh fruit consumption due to bitterness and astringency; however, these apples show potential to use in the development of value-added functional food ingredients or nutraceuticals for blood glucose management. The high TPC apple, "S23-03-749," an advanced breeding line of dessert apple, presents a novel option as a specialty apple cultivar for the dietary management of glycemia.