Kynurenic acid: A potential characteristic marker of Rhus chinensis Mill. honey

Screening for characteristic markers of honey is an effective approach to assessing the authenticity of honey, however, as a high-economic valuable honey, the characteristic markers of Rhus chinensis Mill. honey (RCMH) have not been adequately elucidated. Here, kynurenic acid was identified as a potential characteristic marker of RCMH by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). Subsequently, we developed a quantitative method based on high performance liquid chromatography with diode array detector (HPLC-DAD) that exclusively quantified kynurenic acid in honey with high sensitivity (LOD of 0.08 μg/mL), high precision (RSD<4 %) and good recovery (95.71 %∼103.06 %), allowing the analysis to be completed in 10 min. Quantitative analysis of all 55 RCMHs revealed a mean kynurenic acid content of 79.00 mg/kg, exceeding that of most honey varieties. And despite high kynurenic acid in chestnut honey, its lack of lumichrome makes the combination a definitive marker to differentiate RCMH. The stability tests demonstrated that kynurenic acid was chemically stable, proving it suitable for use as a characteristic marker. Our study identified kynurenic acid as a potential characteristic marker of RCMH and developed a method for its quantification, providing a theoretical basis for the authenticity assessment and quality control of RCMH. • Kynurenic acid was identified as a marker of Rhus chinensis Mill. honey (RCMH). • A method that exclusively quantified kynurenic acid in honey was established. • The quantitative method has high sensitivity, high precision and good recovery. • The content of kynurenic acid in 55 RCMHs and 55 other honey samples was determined. • Thermal, light, oxidation and storage stability of kynurenic acid were analyzed.