An optimized solvent extraction and characterization of unidentified flavonoid glucuronide derivatives from spinach by UHPLC-HR-QTOF-MS

Jashbir Singh; G K Jayaprakasha; Bhimanagouda S Patil

doi:10.1016/j.talanta.2018.06.025

An optimized solvent extraction and characterization of unidentified flavonoid glucuronide derivatives from spinach by UHPLC-HR-QTOF-MS

Talanta. 2018 Oct 1:188:763-771. doi: 10.1016/j.talanta.2018.06.025. Epub 2018 Jun 11.

Authors

Jashbir Singh¹, G K Jayaprakasha², Bhimanagouda S Patil³

Affiliations

¹ Vegetable and Fruit Improvement Center, Department of Horticultural Sciences,Texas A&M University, 1500 Research Parkway, Suite A120, College Station, TX 77845, USA.
² Vegetable and Fruit Improvement Center, Department of Horticultural Sciences,Texas A&M University, 1500 Research Parkway, Suite A120, College Station, TX 77845, USA. Electronic address: gkjp@tamu.edu.
³ Vegetable and Fruit Improvement Center, Department of Horticultural Sciences,Texas A&M University, 1500 Research Parkway, Suite A120, College Station, TX 77845, USA. Electronic address: b-patil@tamu.edu.

PMID: 30029444
DOI: 10.1016/j.talanta.2018.06.025

Abstract

A rapid, sensitive analytical method using ultra-high-pressure liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-HR-QTOF-MS) was developed for the identification and quantification of flavonoids from spinach. The extraction efficiency of flavonoids was evaluated by different solvents such as acetone, ethanol, methanol, acetone: water (70:30), ethanol: water (70:30) and methanol: water (70:30). Flavonoid identification was achieved by UV spectra, high resolution accurate mass and their fragmentation pattern. The precursor and product ions were recorded by both broadband collision ion dissociation (bbCID) and multiple reaction monitoring (MRM) techniques. Different collision energies (5, 10, 15, 20, 40, and 70 eV) were optimized to obtain the mass spectra of flavonoids in positive and negative ionization modes. For the first time, five minor flavonoid glucuronide derivatives were identified in spinach. MRM and bbCID provided glucuronide fingerprint ions at m/z 175.0278 and m/z 113.0257 respectively in negative ionization mode. The quantification of identified flavonoids was achieved by 5,3',4'-trihydroxy-3-methoxy-6:7-methylen-dioxyflavone-4'-β-D-glucuronide which was purified by semi-preparatory HPLC. The purity of the isolated compound was confirmed by NMR analysis. The identified 5,3',4'-trihydroxy-3-methoxy-6:7-methylen-dioxyflavone-4'-β-D-(2'-O-feurloyl-glucuronide) was the prominent flavonoid and the level was significantly higher in the acetone fraction (2.95 ± 0.16 µg/g FW). This study demonstrates the systematic identification of potential bioactive compounds especially glucuronide derivatives from spinach.

Keywords: Glucuronide; MRM; NMR; Spinach; UHPLC-HR-QTOF-MS.