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Advisor(s)
Abstract(s)
Fruits and vegetables are considered a good source of antioxidants, which are beneficial in
protecting the human body against damage induced by free radicals and other reactive oxygen (ROS)
and nitrogen (RNS) species. In this work, we aimed to evaluate the integral antioxidant activity (AOA)
and determine individual polyphenols in fruits and vegetables of frequent consumption. For this
purpose, an innovative and high throughput analytical approach based on original QuEChERS assisted
by ultrasound extraction (USAE), instead of the manual agitation used in the classical procedure,
was optimized and implemented for the isolation of polyphenols. The total phenolic content (TPC),
flavonoids, anthocyanins, and betalains were evaluated using different spectrophotometric assays.
In addition, free radical scavenging by methods 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonate)
(ABTS) and 2,20
-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP)
were used to estimate the AOA of the investigated fruit and vegetable extracts. Red onion,
tamarillo, and beetroot were the samples with the highest AOA. The quantification and identification
of free low molecular weight polyphenols from QuEChERS-USAE extracts was carried out by
ultra-high-pressure liquid chromatography equipped with a photodiode array detection system
(UHPLC-PDA). Catechin was the most abundant polyphenol, followed by gentisic and ferulic acids,
mainly in the watercress sample. In relation to flavonols, quercetin and kaempferol were found mostly
in onion samples, and in small quantities in tomato and watercress. The improved analytical approach,
QuEChERS-USAE/UHPLC-PDA, offers an attractive alternative for the analysis of polyphenols from
fruit and vegetable samples, providing several advantages over traditional extraction techniques, in
terms of reproducibility, simplicity, low cost, analysis speed, and analytical performance.
Description
Keywords
Bioactive compounds Polyphenols Antioxidants Fruits Vegetables QuEChERS-USAE . Faculdade de Ciências Exatas e da Engenharia Centro de Química da Madeira
Citation
Aguiar, J., Gonçalves, J. L., Alves, V. L., & Câmara, J. S. (2020). Chemical fingerprint of free polyphenols and antioxidant activity in dietary fruits and vegetables using a non-targeted approach based on QuEChERS ultrasound-assisted extraction combined with UHPLC-PDA. Antioxidants, 9(4), 305.
Publisher
MDPI