Abstract
Upon a thorough investigation, the Editor-in-Chief has determined that the paper Tung NH, Hoang Anh NT, Tan CV, et al. Oleanane-type saponins from the aerial parts of Panax bipinnatifidus. Nat Prod Commun. 2020;15(5). doi:10.1177/1934578X20926278, includes likely suspected spectral manipulation and data fabrication. Specifically, the authors were asked to address the following inconsistencies:
The carbon signal at 67.1 ppm in Carbon-13 NMR as well as cross-peaks/correlations to H2-6 at 3.66 and 3.80 ppm for xylopyranosyl (II) are missing in HMQC spectrum.
The H5-H2-6 connectivity shown in earlier diagrams is materially different from the current presentation for the glucopyranosyl unit (IV) at C-28.
Request to add unambiguous assignments of all sugar resonances, including sequence analysis and any other details necessary to support the article’s conclusions.
In response to the requested explanations, the authors replied that there is “some deviation in NMR alignment from original 1H-NMR and 2D NMR during NMR processing” and that the “DQF COSY spectrum is very helpful in revealing the coupling system of each sugar units for sugar determination. It is difficult for complex saponin with many sugar units or oligosaccharide.”
The editor has determined that these statements and the authors’ overall response did not address the raised concerns with the data irregularities.
Thus, the structure of the new saponin (1) elucidated as 3-O-{β-D-xylopyranosyl(1→3)-[α-L-arabinofuranosyl(1→4)]-β-D-glucopyranosyl}oleanolic acid 28-O-β-D-glucopyranosyl ester is questionable. When asked to address the apparent data irregularities, the authors were not able to satisfactorily resolve the concerns and were not able to isolate the described saponin in their reinvestigation. As a result, the journal expresses no confidence that the article accurately describes identification a genuine saponin.