The hazelnut as an antitumour agent

After the recent harsh winter a welcome sight, if somewhat later than usual, was an abundance of yellow catkins dangling from the bare branches of hazel trees in gardens and hedgerows.

The common hazel (Corylus avellana) has long been associated with folklore and legend. In medieval England it was a symbol of fertility, with a prolific show of catkins foretelling an abundance of babies in the year to come.

Hazel trees were cultivated by the Romans, and their name for Scotland, Caledonia, is a latinised version of the term “Cal-Dun”, meaning “hill of hazel”.

The hazel has not been as widely used in herbal and folk medicine as some other trees. The dried or fresh leaves have been reported to stimulate bile production, and were employed in patent medicines for gall and liver diseases. Oil extracted from the nuts has been shown to have a mild anthelmintic effect, and the bark has been employed as an astringent substitute for the less widespread witch hazel.

The nuts are a dietary source of protein, unsaturated fatty acids and linoleic acid. They also contain the highest concentration of alpha-tocopherol of any nut, with 100g of nuts providing about 15mg of vitamin E.

A large cohort study in the US demonstrated a significant correlation between blood lipid levels and dietary hazelnut intake, with a 1g per kg body weight supplement of hazelnuts leading to a reduction in low-density lipoproteins and total blood cholesterol and an increase in high-density lipoproteins and triglycerides.

More recent research has focused on the presence of taxanes in extracts from hazel tissue. Originally extracted from the bark of the Pacific yew (Taxus brevifolia), taxanes affect the dissociation of microtubules during mitosis in tumour cells, inhibiting cell division, and are used in cancer treatment.

Their increasing application, particularly in the early stages of treatment, has led to efforts to manufacture them synthetically, but the processes have proved to be costly and low yielding.

However, researchers at the University of Genoa in Italy have succeeded in producing taxanes from quick growing suspension cell cultures derived from various parts of the hazel, particularly the seeds, including the shells.

The fact that potentially valuable taxanes can be produced from a disposable by-product of the food industry could have significant economic implications, and further research is being carried out in this area.