The presence of melatonin in plant foodstuffs is a matter of growing interest since its antioxidant properties and the possible benefits for health of consumers. Fruits of date palm (Phoenix dactylifera, L.) are highly appreciated because of their nutritional value and healthy properties related to high content in antioxidant compounds present in them. In this study, we show that dates’ antioxidant properties persist in several commercialized varieties typical of the European markets, as compared to values referenced from studies in date fruit varieties collected in the origin countries. We also show for the first time that melatonin and one of its isomers are present in dates, being that the isomer content is several times higher than melatonin (in the range of 1 µg per 100 g of fresh weight). The isomer content was highly correlated with total phenolic compounds and total antioxidant capacity in the date varieties. Additionally, high levels of the indoleamines, serotonin and auxin accumulate in dates, which could be related to fruit ripening. All the indole derivatives analyzed in dates exhibited antioxidant activity as assayed by DPPH, with differences among the compounds and concentrations used. These results support that melatonin, its isomer, and related indoles present in dates could contribute to the reported health benefits of this fruit by increasing its natural antioxidant potential.
Date palm fruit Antioxidant capacity Phenolic and flavonoid content Melatonin Melatonin isomer Indoleamines
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The authors thank Sihem Latrach for technical support and assistance in date fruits collection. A. Verde is a fellowship recipient from Xunta de Galicia into the pre-doctoral formation program (Reference ED481A-2017/387).
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Conflict of interest
The authors declare that they have no conflict of interest.
Compliance with ethics requirements
This article does not contain any studies with human or animal subjects.
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