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IntroductionIn China and other Asian nations, Geum japonicum (GJ) is used as functional vegetables or as a type of folk medicine. Ellagic acid (EA) is one of the main active ingredients in GJ and has been utilized in food, cosmetics, and medicinal goods worldwide. Natural deep eutectic solvents (NADESs) have gradually replaced organic solvents for efficient extraction of plant-derived active compounds due to its environmental protection, low toxicity, low solubility, reusability, etc.MethodsNADES with the highest EA yield was selected and the extraction conditions were optimized by response surface methodology (RSM), the antioxidant activity of NADES extract was determined, and finally Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) were used to explain the mechanism for the increase of EA yield in GJ.ResultsIn this work, several NADESs were tailored for the ultrasound assisted extraction (UAE) of EA from GJ, among which choline chloride-oxalic acid (ChCl:Oa) was the most effective. In optimal conditions, ChCl:Oa extract produced higher EA yields than common organic solvents including methanol, ethanol, and acetone. In vitro antioxidant experiments showed that ChCl:Oa extract had stronger DPPH radical scavenging ability than other solvent extracts. Mechanically, FT-IR results indicated that ChCl:Oa could form a hydrogen bonding with EA, which enhanced the stability of EA. Meanwhile, ChCl:Oa-UAE treatment could destroy the tissue structure of GJ, thereby improving EA yield.DiscussionIn conclusion, these results imply that the ChCl:Oa-UAE method might be an environmentally friendly approach for extracting EA from GJ.

Additional file 1: Quality Control of Rhubarb, Figure S1 Multicomponent quantification of the rhubarb, Table S1 Calibration curve of 15 analytes. Animal Experiments, Figure S2 Average food intake (A), weight (B), fecal pellet numbers (C) and fecal water content (D) of the normal group and model group, Figure S3 Evacuation index (A) and fecal water content (B) of the normal group, model group and rhubarb groups, Figure S4 Pathological sections of colons in the normal group, model groupand rhubarb groups. UPLC-Q-TOF/MS Data Acquisition, Figure S5 Representative base peak intensity (BPI) chromatograms of serum samples from the normal group, model group and rhubarb groups in positive ion and negative ion modes, Figure S6 PLS-DA score plots of serum samples classifying the normal group, model group and rhubarb groups and QC samples detected in positive (A1) and negative (A2) ion modes, Table S2 Mean values of 462 metabolic features for serum samples of the normal group, model group and rhubarb groups.