Melatonin: a grape excuse to hit the bottle

Update 22.2.2007(12.7.2006)billn

Back from a short break. Gratified to see that the site made a new record last week when the summer issue was launched: 743 unique IP addresses in one day – wow – that’s 200 up on the last record!

Just in case you need more excuse to drink here’s an article I picked up last week from Chemistry in Industry:

Melatonin: a grape excuse to hit the bottle

by Marina Murphy

There is now yet another reason to drink more wine. Scientists in Italy say they have discovered that grape varieties used to make some of the most popular red wines contain melatonin, the ‘sleep hormone’ previously thought to be produced only by mammals.

Melatonin (N-acetyl-5-methoxy-tryptamine) is produced in the pineal gland, a pea-like organ located in the brain that is sensitive to light. When light hits the eye, production of melatonin ceases. Besides aiding sleep, melatonin is thought to influence annual rhythms and seasonal changes in animals.

Researcher Iriti Marcello of the University of Milan believes: ‘the melatonin content in wine could help regulate the circadium rhythm [sleep-wake patterns], such as the melatonin produced by the pineal gland in mammals’. This, he said, may well explain why so many of us reach for the bottle to help us wind down after a long day.

Iriti’s group measured melatonin content in the skins of eight Vitis vinifera cultivars (grape varieties): Barbera, Cabernet Franc, Cabernet Sauvignon, Croatina, Nebbiolo, Merlot, Marzemino and Sangiovese. Concentration varied greatly among the cultivars with the highest levels of melatonin found in Nebbiolo, Merlot, Cabernet Sauvignon, Sangiovese and Croatina (Journal of the Science of Food and Agriculture, doi:10.1002/jsfa.2537). Nebbiolo contained the highest melatonin levels at around 400pg/ml.

But Richard Wurtman, of the department of brain and cognitive sciences at Massachusetts Institute of Technology, Cambridge, is sceptical. ‘Many investigators have tried and failed in the past to find melatonin in a number of foods,’ he said. Wurtman is not convinced that what the researchers are calling ‘melatonin’ is melatonin — ‘just something with some fairly similar high-pressure liquid chromatography parameters and some immune cross-reactivity (by enzyme-linked immunosorbent assay). More appropriate studies should use gas chromatography/mass spectrometry,’ he said.

Itisi’s group say that the concentration of melatonin in grapes can be increased using benzothiadiazole, a chemical that increases disease resistance in plants (a plant ‘vaccine’).

Melatonin levels in human blood range from 20pg/ml in the morning to 55pg/ml at night.

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