Phytochemical Compositions, Antioxidant Properties, and Colon Cancer Antiproliferation Effects of Turkish and Oregon Hazelnut

Abstract

Roasted and raw Turkish and Oregon hazelnuts were examined. Whole nuts, skins, and skinless nuts of both hazelnut varieties were tested for fat contents, fatty acid profiles. Hazelnut and other byproducts were extracted with 50% ace- tone and examined for total phenolic contents (TPC), antioxidant activities against the peroxyl (ORAC) and DPPH radicals, and were also administered in vitro to the human colon cancer HT-29 cell line to determine antiproliferative effects. The Turkish hazelnuts contained over 65% total oil while the Oregon roasted variety contained 43.8%. The primary fatty acid in both was oleic acid (18:1n-9) comprising 76.7 g/100 g oil in the Oregon variety and 83.3 g/100 g oil in the Turkish variety. The TPC were 91.4 and 102.16 mg gallic acid equivalents/ g sample for the Turkish roasted hazelnut skin and Oregon roasted hazelnut skin respectively, at least 30-folds as high as the hazelnut without skin. Turkish roasted hazelnut skin had the highest ORAC value of 1166.27 Trolox equivalents (TE) mmol/g sample (TE mmol/g), it is 38 times as high as the Oregon roasted hazelnut no skin which as a value of 30.2 TE mmol/g sample. The range of ED50 of DPPH? is from 118.22 to 0.075 mg sample equivalents/ mL among the samples, Oregon roasted hazelnut skin and Turkish raw hazelnut no skin exhibit the weakest and strongest ability to reduce DPPH? respectively. At 6 mg/mL media Oregon roasted hazelnut skin extract significantly inhibited the growth of the HT-29 cells by 96h following 4 days of treatment, and no effect was seen from the Turkish roasted skinned hazelnut extract. The Turkish raw hazelnut had significantly higher antioxidant activities compared to the Oregon roasted variety which may be explained by chemical changes during heating or possibly the total oil to flour ratio.