Quantitative Analysis of Kynurenic Acid in Chestnut Honey from Different Regions and Method Validation

Abstract

Chestnut honey is a sweet dark-colored honey with a distinct bitter aftertaste. It contains numerous phenolic compounds and alkaloids and is noted for its antioxidant and anti-inflammatory activities. However, it has been established that there are differences in the composition and activity of chestnut honey constituents depending on the region of origin, the sources of which warrant further research. In this study, we analyzed the kynurenic acid (KA) contents in chestnut honey produced in nine different regions in Korea, using high-performance liquid chromatography in conjunction with ultraviolet detection, and validated the analytical method developed. Use of a reverse-phase column and detection at a wavelength of 240 nm were found to be optimal for the detection of KA. Similar evaluation of an optimal method for extracting KA from chestnut honey revealed that extraction using 10% EtOH at 20 times the sample volume over a 6 h period was the most suitable for obtaining a high content of KA. Among the nine regional chestnut honeys assessed, KA content was found to be highest in the “Gongju” sample (1.14 mg/g), followed by that in the “Cheongdo” and “Damyang” samples. Validation of the KA analytical method revealed a good analyte linearity, with a correlation coefficient (r2) of 0.9995, an accuracy of between 92.37% and 107.35%, and good precision (RSD ≤ 1.05%). Our findings in this study, based on a validated quantitative analytical method for KA, could make an important contribution to establishing a data profiling procedure for characterizing chestnut honeys produced in different regions, and may also provide basic data for the identification of functional honey.