Development of a Rapid UHPLC-PDA Method for the Simultaneous Quantification of Flavonol Contents in Onions (Allium cepa L.)

Abstract

Onion, one of the most consumed vegetables in the world, is also known to contain high levels of antioxidant compounds, with protective effects against different degenerative pathologies. Specifically, onion is rich in flavonols, mainly quercetin derivatives, which are compounds with high antioxidant and free radical scavenging power. For this reason, it is of the utmost importance to count on optimal analytical methods that allow for the determination and quantification of these compounds of interest. A rapid ultra-high performance liquid chromatography (UHPLC)-photo-diode array (PDA) method for the separation of the major flavonols in onions was developed using a Box–Behnken design in conjunction with multiresponse optimization on the basis of the desirability function. The conditions that provided a successful separation were 9.9% and 53.2% of phase B at the beginning and at the end of the gradient, respectively; 55 °C column working temperature; and 0.6 mL min−1 flow rate. The complete separation was achieved in less than 2.7 min with excellent chromatographic characteristics. The method was validated, and its high precision, low detection and quantification limits, good linearity, and robustness were confirmed. The correct applicability of the method improves the analysis of the raw material, increasing the quality of onions and its subproducts in terms of bioactive compounds and functional characteristics for consumers.

Quercetin-Rich Extracts from Onions (Allium cepa) Play Potent Cytotoxicity on Adrenocortical Carcinoma Cell Lines, and Quercetin Induces Important Anticancer Properties

“…Allium cepa L., commonly known as onion, is a commonly consumed food worldwide, with antioxidant effects related to its intake. Among its biological active molecules, flavonoids are appointed as the major contributors to this beneficial effect [11]. Flavonoids are a type of plant secondary metabolite largely known for their antioxidant effects [12].…”

Phytochemical Analysis of the Antioxidant Compounds of Baper Tea and Its Potential as an Immunomodulatory agent and Candidate for Standardized Herbal Medicine

“…Flavonoids (flavonol, quercetin, and lutenoline), bioactive components in Baper tea, can enhance the proliferation of T lymphocyte cells, which are indications of increased body immune systems [24,25]. Flavonoid content is a natural antioxidant that boosts immune response and fights lymphokine generated by T-cytotoxic cells, encouraging phagocytic cells to respond to phagocytosis.…”

Optimization of a Microwave Assisted Extraction Method for Maximum Flavonols and Antioxidant Activity of Onion Extracts

“…The method used to identify flavonoids and subsequently quantify their content in the onion samples had been previously developed by our research group [ 26 ]. Before both analyses, the extracts were filtered through a 0.20 µm nylon syringe filter (Membrane Solutions, Dallas, TX, USA), and 3 µL were injected into each extraction system.…”

“…The general characteristics of the UHPLC-PDA method were the following: a C18 analytical column (1.7 µm, 2.1 × 50 mm., UPLC ® BEH C18, Waters Corporation, Milford, MA, USA), a binary solvent system (phase A, 2% solution of acetic acid in water, and phase B, 2% solution of acetic acid in acetonitrile), a flow rate of 0.6 mL min −1 and a column at 55 °C. The gradient employed, which had been previously optimized based on a multi-response (MRO) Box–Behnken (BBD) experimental design, allowed the separation and quantification of the seven flavonols that have been previously mentioned in less than 2.7 min [ 26 ]. The UHPLC chromatogram obtained can be seen in Figure 1 .…”