Melatonin is a hormone synthesized during the night by the pineal gland in mammals. Melatonin regulates our sleep/wake cycle and exerts its effects by binding to its receptors named MT1 and MT2. Since melatonin is also synthesized by plants, the authors wondered if the known beneficial effects of some plants on sleep could be explained by a high content in melatonin. Thus, they studied on melatonin receptors the effect of 25 plant extracts known for their beneficial effects on sleep and anxiety.

The team of Ralf Jockers and his collaborators in partnership with the pharmaceutical company Sanofi (France) showed that among the 25 plant extracts tested, the pistachio extract "Pistacia vera" differs from all the other extracts by its high binding affinity and potency of activating melatonin receptors signaling pathways (inhibition of cAMP production, activation of ERK phosphorylation, etc…) at a similar extend than exogenous melatonin. The determination of the melatonin content in the “Pistacia vera” extract revealed a very high content of 5 mg of melatonin per gram of extract.

Consequently, the consumption of 0.5 to 1 g of pistachio extract is sufficient to ingest 2 to 5 mg of melatonin, the daily amount recommended in humans to facilitate sleep initiation and the adjustment of the circadian rhythm.

Another unexpected result of our study was the existence of an additional unidentified active component able to increase the efficacy and potency of endogenous and exogenous melatonin. This potentiating effect was also found in 4 other of the tested plant extracts.

The amount of melatonin produced by the body tends to decrease with age and during the development of some diseases such as Alzheimer disease, type 2 diabetes, cardiovascular disease, some types of cancer, endocrine and metabolic disorders etc. To compensate for this decline, many people take melatonin preventively. Thus, the consumption of pistachio extract, which would also contain other beneficial and potentiating molecules, could become a natural alternative to synthetic melatonin.

This work was funded by Sanofi-aventis Group, the Inserm, the CNRS and China Scholarship Council.