Three years after questions surfaced, PLOS ONE retracts paper about potential antibiotic

In April 2015, two high-profile chemistry bloggers — and their commenters — raised questions about a paper that had been published in PLOS ONE some 18 months earlier. More than three years later, the journal has now retracted the paper, with a notice that echoes the 2015 blog posts.

So what took so long? PLOS tells Retraction Watch:

We investigate all retraction cases comprehensively and with due care. There have also been delays at points in the process, and we have been addressing these by strengthening our workflows and increasing our staff resources.

Indeed, PLOS ONE editor Joerg Heber pointed out in a recent interview with us that the journal had recently created a team dedicated to reviewing allegations about papers.

Here’s the retraction notice for “A Novel Alkaloid from Marine-Derived Actinomycete Streptomyces xinghaiensis with Broad-Spectrum Antibacterial and Cytotoxic Activities:”

The PLOS ONE Editors retract this publication due to concerns about the chemical structure and spectral data reported in this article.

After publication of the article, concerns were raised regarding the validity of the reported structure of Xinghaiamine A, and about the spectral data used to validate that structure.

PLOS ONE staff consulted a Section Editor and asked the authors to provide the raw data underlying the results presented in the article. The authors did not provide the original data, but they requested withdrawal of the article and confirmed that the structure presented is incorrect.

The corresponding author apologized for the errors and indicated that spectral images from NMR analyses of different purification batches had been combined in error when deducing the reported structures.

In the light of the concerns about the integrity of the results and the underlying data, the PLOS ONE editors retract this publication.

WJ, FZ, XZ, JH and J-WS agreed with the retraction.

Questions raised in 2015

The original paper appeared on October 1, 2013. On April 16, 2015, after coming across the article in a search, chemistry blogger See Arr Oh wrote:

Ever looked at a molecule and thought something was just…off?

Derek Lowe, who blogs at The Pipeline, followed up the next day:

Now, there are some truly crazy-looking natural products out there, but this one, were it to be real, would be a strong contender for the craziest.

I don’t think it’s real.

Given our relative lack of training in chemistry, we’d urge readers to click through to See Arr Oh’s and Lowe’s blogs to see what questions they and their commenters raised.

The paper has been cited a dozen times, according to Clarivate Analytics’ Web of Science, including seven times since the 2015 blog posts.

We asked Lowe for his take on the retraction notice. In a post, he says:

As for those NMR spectra, the notice says that the corresponding author “indicated that spectral images from NMR analyses of different purification batches had been combined in error when deducing the reported structures“. Why yes. It is indeed an error to use image-editing software to cut and paste peaks and assemble a spectrum. If your NMR spectra from different batches do not agree with each other, you don’t get to glue the pieces together into what you think one should look like.

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