Hazelnuts are grown in many parts of the world and their kernels are a popular food. Hazelnut kernels contain a wide range of secondary metabolites, which could have biological effects. In-depth knowledge of these components can help to understand the nutritional value of hazelnuts and decide if some of their contents can be used, e.g., in functional foods.

Haji Akber Aisa, Xinjiang Technical Institute of Physics and Chemistry and University of the Chinese Academy of Sciences, both Beijing, and colleagues have isolated seven indoleacetic acid glycosides (six of which were previously unknown), three indole alkaloids, and a dihydrobenzofuran-type neolignan from hazelnut kernels. Shelled and ground kernels were degreased with petroleum ether and extracted with methanol. The researchers separated the components in the methanol extract using chromatographic techniques and isolated the eleven compounds listed above. Their structures were determined by high-resolution electrospray-ionization mass spectrometry (HR-ESI-MS), NMR spectroscopy, and gas chromatography (GC). The team tested the compounds for biological effects using an in vitro anti-inflammatory activity assay, antimicrobial activity assays, and a 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), or ABTS, radical-scavenging activity assay.

Five of the indoleacetic acid glycosides showed anti-inflammatory activity, and three of the isolated compounds were active against the yeast Candida albicans. The dihydrobenzofuran-type neolignan showed strong antioxidant activity. Thus, several of the newly isolated hazelnut kernel compounds display promising biological activity. In combination with previously described beneficial health effects of other hazelnut components, these findings could provide a basis for further studies on the health effects and potential applications of hazelnuts.

• Chemical Composition of the Hazelnut Kernel (Corylus avellana L.) and Its Anti-inflammatory, Antimicrobial, and Antioxidant Activities,
  Dilireba Shataer, Jun Li, Xiao-Mei Duan, Liu Liu, Xue-Lei Xin, Haji Akber Aisa,
  J. Agric. Food Chem. 2021.
  https://doi.org/10.1021/acs.jafc.1c00297