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Study of flavonoids in aqueous spinach extract using positive electrospray ionisation tandem quadrupole mass spectrometry

Dehkharghanian, Masood, Adenier, Hervé, Vijayalakshmi, Mookambeswaran A.
Food chemistry 2010 v.121 no.3 pp. 863-870
spinach, food analysis, food composition, flavonoids, analytical methods, plant extracts, mass spectrometry, ionization, quercetin, kaempferol, myricetin, apigenin, luteolin, polyphenols, flavonols, flavones, phytochemicals
The presence of three flavonols (quercetin, kaempferol, myricetin) and two flavones (apigenin, luteolin) were investigated in the extract of fresh spinach leaves. Aqueous spinach extracts were prepared with a leaf/water ratio of 1:2 at 80°C for 30min stirring. Ferric ammonium sulphate method was used for measuring total polyphenols in the extracts and expressed as catechins and tannic acid equivalents. The flavonoids glycosides in the extract were hydrolysed to their aglycons with 1.2M HCl in boiling 50% water methanol solution. The resulting aglycons were identified and quantified by a C18 reverse phase high-performance liquid chromatography (RP-HPLC). Furthermore, the results were confirmed by HPLC coupled to an electrospray ionisation tandem triple-quadrupole mass spectrometer ESI-MS performing low-energy collision induced dissociation (CID-MS/MS) in the collision cell (HPLC-ESI-MS/MS). Analyses were made in the multiple reaction monitory (MRM) mode. Results showed that total polyphenols contents in fresh spinach leaves were 270mgkg⁻¹ and 390mgkg⁻¹ as tannic acid and catechin equivalents, respectively, in which, major flavonoids aglycons were apigenin (170mgkg⁻¹), quercetin (50mgkg⁻¹) and kaempferol (30mgkg⁻¹).