Hazelnut By-Products as a Valuable Resource: Lipid Peroxidation Inhibition Effect, Bioaccessibility and Antidiabetic Properties

Abstract

The aim of this study is to determine the chemical and molecular properties of hazelnut by-products, to measure the bioaccessibility values of phenolic compounds found in the structure of these wastes and to reveal their antidiabetic and lipid peroxidation (LPO) inhibition effects. The highest moisture and protein content were found in skin samples with 6.33% and 7.70%, respectively. The predominant fatty acid in hazelnut skin is oleic acid, which constitutes 78.65% of the total fatty acid composition. The highest antioxidant activity value was measured in the shell with an IC50 value of 19.08 mg/mL. The sample with the highest content of gallic acid and protocatechuic acid content was the skin extract. The dominant phenolic component in the shell and husk samples was kaempferol, while in the skin sample it was rutin. Shell bioaccessibility was found to be much higher for o-coumaric acid (45.83%), rutin (49.25%) and kaempferol (46.32%) components. The bioaccessibility of the shell sample in total phenolic concentration was measured as 45.87%. The highest LPO inhibition value belonged to the shell sample with an IC50 of 4.50 mg/mL, while the lowest value belonged to the husk sample with an IC50 value of 25.03 mg/mL. The highest antidiabetic effect was observed in the shell sample with values of 3.55 mg/ mL and 25.44 mg/mL for alpha-amylase and alpha-glucosidase inhibition, respectively. The highest recovery belonged to 4-Hydroxybenzoic acid in the skin sample. As a result, it was concluded that hazelnut by-products, especially the shell, exhibit high antioxidant effects, have antidiabetic and LPO inhibition properties thanks to their bioactive components and high bioaccessibility values. Thus, they have valuable usage opportunities in the fields of food, pharmacology and medicine.