Nuts: Oh, hazelnuts

Skip to Navigation


  • Published: Dec 15, 2013
  • Author: David Bradley
  • Channels: NMR Knowledge Base
thumbnail image: Nuts: Oh, hazelnuts

Codensed tannins

Identification of Two Novel Prodelphinidin A-type Dimers from Roasted Hazelnut Skins  1  (Corylus avellana L.)

Two condensed tannins, novel A-type dimeric prodelphinidins, which are thought to be beneficial to health have been isolated from the skin of the festive favourite roasted hazelnuts and characterised using NMR spectroscopy.

Greece, Italy, southern Catalonia and Kent in the South East of England as well as the US states of Oregon and Washington are big producers of hazelnuts. However it is turkey that has cracked the market, generating about three-quarters of worldwide production.

The alleged health benefits of nuts and pulses are apparently well known to the readers of so-called lifestyle and health magazines, but rationalising the effects of particular nutty treats, such as hazelnuts, requires more than a passing glance at their broad nutritional values. Hazelnuts, the seeds of the Corylus avellana (hazel) tree, are rich in protein and unsaturated fats and they also contain various vitamins and minerals of value to human health, including significant concentrations of thiamine and vitamin B6, as well smaller quantities of other vitamins. It is the presence of other nutritional agents, phytochemicals with physiological activity, antioxidants and the like, that is of interest for specific benefits.

Pharmaceuticals and functional foods

Writing in the American Chemical Society's Journal of Agricultural and Food Chemistry, Tuba Esatbeyoglu and Peter Winterhalter of the Institute of Food Chemistry, at the Technische Universität Braunschweig, in Braunschweig, and Victor Wray of the Helmholtz Centre for Infection Research, also in Braunschweig, Germany, explain their interest in proanthocyanidins. These compounds of current interest in medicine because they are thought to have a role to play in protecting us from chronic diseases, such as cardiovascular disease, type 2 diabetes and cancer. The proanthocyanidins, also known as condensed tannins, are a group of the ubiquitous phenolic compounds in our diet. The A-type proanthocyanidins, while of potential importance to health, have only been found in a limited number of foods such as peanuts, plums, cranberries, avocados and cinnamon.

Winterhalter and colleagues were well aware that hazelnut skins, a by-product of the roasting process are of interest to the pharmaceutical and food industries as a feedstock for novel drugs and natural "functional" food additives, especially given that they are rich in antioxidants.

Purification and characterisation

The team has now used low-speed rotary countercurrent chromatography (LSRCCC), with final purification by preparative high-performance liquid chromatography (HPLC) to isolate the A-type dimeric prodelphinidins from the skins of roasted hazelnut. They then explain how they used a combination of mass spectrometry (HPLC-ESI-MS and HR-ESI-MS) together with NMR spectroscopy (2D proton-proton COSY, HSQC, HMBC and NOESY) to determine the structures of these compounds. They also looked at the circular dichroism (CD) and acid-catalyzed degradation (phloroglucinolysis) of the extracted substances to corroborate their proposed structures.

The team concedes that these compounds are but minor components of the hazelnut skin. However, they point out that to the best of their knowledge, they are unique compounds with particular linkages in the dimmers. As such, they represent molecular novelty in natural structures that will be of interest to researchers investigating the potential of natural products from food sources with value as pharmaceutical or nutritional starting points.

Related Links

J Agric Food Chem, 2014, in press: "Identification of Two Novel Prodelphinidin A-type Dimers from Roasted Hazelnut Skins (Corylus avellana L.)"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

Social Links

Share This Links

Bookmark and Share


Suppliers Selection
Societies Selection

Banner Ad

Click here to see
all job opportunities

Copyright Information

Interested in separation science? Visit our sister site

Copyright © 2018 John Wiley & Sons, Inc. All Rights Reserved