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. 2022 Jan 28;14(3):575. doi: 10.3390/nu14030575

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© 2022 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Chemical characterization of a URAT1-inhibitory activity-guided fraction from the ethanolic extract of rooibos leaves. Each subfraction and authentic quercetin (lower panels in (c–e)) were analyzed using a high-performance liquid chromatography instrument coupled with a diode array and multiple wavelength detector (LC-DAD), and a quadrupole time-of-flight-mass spectrometry system (LC-Q-TOF-MS). (a) Purity verification of the isolated ingredient in Subfraction #11 (Fr.#11) by spectrometric analyses. Left panels, UV chromatograms recorded at 285 nm. Right panels, LC-Q-TOF-MS extracted ion chromatograms (EICs; at m/z 303.0506 in the positive ESI spectrum). †, a specific peak in Fr.#11 with a retention time of 5.298 min. (b) Chemical structure of quercetin. (c–e) Comparison of obtained data between Fr.#11 and quercetin; (c) DAD spectrum; (d) EIC; (e) information regarding the fragment ions derived from MS/MS analyses.