Levels of the antioxidant melatonin in fruits of edible berry species

Melatonin (N-acetyl-5-methoxytryptamine) was originally identified as an animal hormone. It was later found also in many plants. It is a free radical scavenger and antioxidant and also activates some antioxidant enzymes. Evidence, mainly from animal models, suggests that melatonin administration may help to prevent or cure diseases associated with oxidative stress, including neurodegenerative diseases, which frequently occur during aging. (See [1] for review.)

Melatonin consumed in edible plants may thus have beneficial effects on human health. It has yet to be shown whether consumption of melatonin in plant-based food increases melatonin levels in humans. However, rats fed with walnuts had increased melatonin blood levels and increased total antioxidant capacity of blood serum [2].

Berries are popular fruits but melatonin levels in most of them are unknown. We therefore investigated melatonin levels in several edible berries. For sample preparation, we developed a method based on Tris/HCl buffer extraction (modified from [3]) followed by partitioning with chloroform and solid-phase extraction using C₁₈ cartridges. Melatonin was determined by liquid chromatography – tandem mass spectrometry.

Melatonin was measured in fresh fruits of 10 species: blueberry (Vaccinium myrtillus), goldenberry (Physalis peruviana), blackberry, elderberry (Sambucus nigra), grape, highbush blueberry (Vaccinium corymbosum), raspberry (Rubus idaeus), red currant, cranberry (Vaccinium vitis-idaea), and strawberry. Levels ranged between 7 and 48 pg.g^-1 fresh weight, being the highest in Vaccinium myrtillus (48 pg.g^-1), Physalis peruviana (41 pg.g^-1), and blackberry (21 pg.g^-1).

Acknowledgements: Supported by grant COST OC154 by MSMT CR.

References: [1] Pandi-Perumal, S. R. et al. (2006) FEBS J. 273:2813–2838.

[2] Reiter, R. J. et al. (2005) Nutrition 21:920–924.

[3] Poeggeler, B. et al. (1991) Naturwissenschaften 78:268–269.