Bioactive potential of hazelnut husks was determined as a function of their cultivar source and extraction solvent. Hazelnut husks from four hazelnut cultivars (Butler, Grada de Viseu, Lansing and Morell) were picked in a hazelnut orchard at harvest and extracted with five solvents with different polarity: water, methanol, acetone, ethyl acetate and hexane. Phenolics were identified by HPLC–DAD and antioxidant activity was determined by three complementary methods: DPPH, FRAP and inhibition of lipid peroxidation. A total of 11 phenolics were identified in studied cultivars and grouped in five main classes namely, ellagitannin (ellagic acid), benzoic acids (gallic acid, protocatechuic acid and vanillic acid), flavonols (kaempferol-3,7-O-diglucoside, kaempferol-3-O-[6-acetylglucoside]-7-O-glucoside, kaempferol-3-O-[6acetylglucoside]-7-O-rhamnoside and quercetin-3-O-rutinoside), flavone (luteolin-7-O-rutinoside) and flavan-3-ol (epicatechin). Cultivar and extraction solvent influenced significantly (p < 0.001) the extraction yield. ‘Grada de Viseu’ husks presented the highest content of individual phenolics identified, particularly in methanol extracts whilst ‘Lansing’ showed the lowest levels. Similar pattern was found for antioxidant activities. Methanolic husk extracts exhibited the greatest antioxidant potentials followed by water and acetone. The valorization of hazelnuts by-products gives an important contribution for the isolation and purification of bioactive molecules that can be used for both medicinal and industrial purposes.

Graphic abstract

中文翻译：

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榛子Hu壳利用不足，但多酚的重要来源

确定了榛子皮的生物活性潜力，取决于其品种来源和提取溶剂。将来自四个榛子品种（巴特勒，格拉达·德维塞乌，兰辛和莫雷尔）的榛子皮在收获时采摘到榛子果园中，并用五种极性不同的溶剂萃取：水，甲醇，丙酮，乙酸乙酯和己烷。通过HPLC-DAD鉴定酚类，并通过三种互补方法测定抗氧化剂活性：DPPH，FRAP和抑制脂质过氧化。在研究的品种中共鉴定出11种酚类化合物，并分为5个主要类别，即鞣花单宁（鞣花酸），苯甲酸（没食子酸，原儿茶酸和香草酸），黄酮醇（山茱emp醇-3,7 - O-二葡萄糖苷，山emp酚） -3- O-[[6-乙酰基葡萄糖苷] -7- O-葡萄糖苷，山奈酚-3 - O- [6-乙酰基葡萄糖苷] -7 - O-鼠李糖苷和槲皮素-3 - O-芸香苷），黄酮（木犀草素-7- O-rutinoside）和flavan-3-ol（epicatechin）。品种和提取溶剂对提取得率有显着影响（p <0.001）。“维萨格拉豆”皮中所鉴定的单个酚类含量最高，尤其是甲醇提取物中，而“兰辛”皮中含量最低。发现抗氧化剂活性相似的模式。甲醇皮提取物表现出最大的抗氧化潜力，其次是水和丙酮。榛子副产品的增值为分离和纯化可用于医学和工业目的的生物活性分子做出了重要贡献。

图形摘要