A spectroscopy journal has issued an expression of concern over a 2014 paper by researchers in Iran on the amount of the sleep hormone melatonin in pistachios after German authorities — prompted by a journalist’s questions — concluded that the analysis was in error.
The article, “Expression of concern to spectrofluorimetric determination of melatonin in kernels of four different pistacia varieties after ultrasound-assisted solid-liquid extraction,” was published in Spectrochimica Acta A: Molecular and Biomolecular Spectroscopy, an Elsevier journal.
The authors, from the University of Kerman, reported:
Melatonin is normally consumed to regulate the body’s biological cycle. However it also has therapeutic properties, such as anti-tumor, anti-aging and protects the immune system. There are some reports on the presence of melatonin in edible kernels such as walnuts, but the extraction of melatonin from pistachio kernels is reported here for the first time.
Among the conclusions of the paper (which has been cited 16 times, according to Clarivate Analytics’ Web of Knowledge):
Considering the numerous medicinal effects of melatonin, its presence in pistachio kernels, a common nut, can provide a delicious source of melatonin for us.
But that didn’t sit right with Nicola Kuhrt, who wrote in February on Medwatch (via Google Translate):
For a scientific publication, a surprisingly eloquent formulation – from the land of pistachio exporter Iran.
‘No significant melatonin content could be detected’
So Kuhrt asked some experts for their takes on the paper. They were dubious, so she asked the German Federal Institute for Consumer Protection and Food Safety (BVL) for comment. Werner Mäntele, editor of the journal, who was also contacted for comment for the Medwatch article in February, told us that BVL
…had been informed that some of the melatonin concentrations reported in the article published by Oladi et al. were at a level where regulations on pharmaceutical products would eventually apply. They performed an independent analysis of pistachia from the same region and came to the conclusion that the (i) specificity of the analysis method reported by Oladi et al. is insufficient for melatonin detection and (ii) no significant melatonin content could be detected for pistachia from that region in their lab.
And so, the expression of concern has now appeared:
The editors of Spectrochimica Acta A have been informed that an independent analysis by the German Federal Institute for Consumer Protection and Food Safety (BVL) could not detect traces of melatonin in pistachia from the same region as reported in the above paper, and has claimed that the method described by the authors may be inadequate for detection of traces of melatonin. The authors of that paper state that the method they describe is valid and that the discrepancy in melatonin content may be explained by the high variability from year to year as well as on harvesting conditions.
We emailed the senior author, Ali Mostafavi, of Shahid Bahonar University of Kerman in Iran, for comment but have yet to hear back. [See update at end of post.]
Mäntele added that the manuscript was handled by a former co-editor:
This editor had followed the rules of SAA in that he asked colleagues to act as reviewers. Both reviews were correct and positive, so the manuscript was finally accepted for publication.
After a long discussion with the journalist and the authors, we finally have decided for an expression of concern.
Update, 1400 UTC, 5/7/19: Mostafavi sent us some comments by email:
We don’t judge the German authorities claim. We can only rest to the present studies on the melanin content. Unfortunately, there are not similar works on the melatonin content of pistachio. However, different studies have been performed on the melatonin as a plant hormone in different plant species. In these reports, we can find that the melatonin content in plants varies with different factors for example the environment conditions.
He added:
It is worth noting that we should not look at melatonin as a simple phytochemical, but also it is a plant hormone. As we know, the level of a hormone considerably varies in response to the different changes and stresses made. So, We cannot provide even a range for the level of melatonin. It depends on the harvest time. Since our samples were collected on 2011 and our article has been published on 2014, the samples of the German journalist have been harvested at least 4 years after our samples. During these years many things have been changed in the garden that both samples were collected from, especially right at the harvest time. Have all the parameters mentioned above has been the same when the samples were harvested?
However, we checked the notes, data and calculations of Mrs. Oladi, the student worked on the project. No objection was found.
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The editor should never have published the paper in that state. Subjective judgements (“delicious”) have no place in a scientific article.
Fill disclosure: I don’t like the taste of pistachios.
I love pistachios, and I still think subjective descriptors should stay away from the literature.
I am surprised SAA took this action, considering my prior (rather negative) experience with them when contacted about fundamental errors in >50 papers. All I and a colleague managed was a critical Editorial (https://doi.org/10.1016/S1386-1425(12)00853-0) that eventually had limited impact (seven years later, and SAA still publishes the same type of papers that Mäntele criticized in his Editorial).
An Expression of Concern does seem unusual for an inter-laboratory replication attempt failure. Not inappropriate, but unusual. Still, I wonder how it would have played out if the affiliations were switched: if the journal had been contacted by Iranian food safety authorities complaining that they couldn’t replicate findings by German chemists, would it have been handled the same?
this is why I buy only California pistachios
So pistachia is the plural of pistachio? Who knew?
I scrolled through volume 132 of Spectrochimica Acta and got the impression it is quite inclusive and provides authors from developing countries with the opportunity to publish something looking like a scientific paper. Maybe they also provide opportunities to referees from such countries to practice writing referee reports.
The authors of the article in question extracted pistacia and measured the fluorescence of the crude extract (no prior fractionation took place) and assumed that whatever the emission was, it must all come from melatonin, because that is the compound they were hoping to find. It is the method of wishful thinking applied to analytical chemistry, really.
I find it notable that the Editor Dr. Mäntele is cited in the Medwatch article as stating: “The morale of many authors, both at home and abroad, is often not the best, and the ability of reviewers and editors to identify these mistakes before publication is limited.”
This journal does not appear to publish too many articles by “authors from home”, judging from the absence of recognizable German names among the authors in volume 132. Mentioning the home/abroad distinction without being asked and stating that it is irrelevant is a bit lake saying: “Go on, nothing to see here…”.