Isolation and characterization of a new oxyphenisatin analogue, oxyphenisatin propionate, from a processed plum intended as a weight loss product

A new oxyphenisatin analogue was detected from a processed plum claiming to be a weight loss product without any side effects during the daily inspecting and monitoring of illegal adulterants in health supplements. An abundant peak caused our interest firstly owing to its identical fragments of m/z 224 and 196 in the MS/MS experiments with those of oxyphenisatin acetate. The chemical structure of the unknown compound was characterized by ultra-high performance liquid chromatography equipped with diode array detector and quadrupole time-of-flight tandem mass spectrometry (UHPLC-DAD-Q-TOF/MS), followed by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy experiments. Based on the data, it was defined that the two symmetrical acetyl groups in oxyphenisatin acetate were replaced by two propionyl groups for the unknown structure. Finally, the new oxyphenisatin analogue was identified as 3,3-bis[4'-(propionyloxy)phenyl]-1,3-dihydroindole-2-one and designated as oxyphenisatin propionate. Thereafter, the content of the new analogue was quantitatively determined to be 681 mg/kg, which would inevitably cause adverse health effect because there was not specification for daily consumption of this product. To the best of our knowledge, this is the first report for identification of oxyphenisatin propionate.