School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemLC-ESI-QTOF/MS Characterisation of Phenolic Acids and Flavonoids in Polyphenol-Rich Fruits and Vegetables and Their Potential Antioxidant Activities(MDPI, 2019-09)Polyphenols are naturally occurring compounds found largely in fruits and vegetables. The antioxidant properties of these polyphenols including total phenolic content (TPC), total flavonoid content (TFC), tannin content, 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), 2,2'-azinobis-(3-ethylbenzo-thiazoline-6-sulfonic acid) (ABTS) scavenging abilities and ferric ion reducing antioxidant power (FRAP) were measured among sixteen (16) plant foods (mango, blueberry, strawberry, black carrot, raspberry, dark grapes, garlic, ginger, onion, cherry, plum, apple, papaya, peach, pear and apricot) by modifying, standardising and translating existing antioxidant methods using a 96-well plate reader. Eighteen targeted phenolic acids and flavonoids were characterised and quantified using high-performance liquid chromatography-photometric diode array (HPLC-PDA) and verified by modifying an existing method of liquid chromatography coupled with electrospray-ionisation triple quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF/MS). While most of these compounds were accurately detected by the HPLC-PDA at a low concentration, a few polyphenols in low concentrations could be only be characterised using the LC-ESI-QTOF/MS method. Our results showed that mango possessed the highest overall antioxidant activity, phenolic acid and flavonoid content among the selected fruits. Factor analysis (FA) and Pearson's correlation tests showed high correlations among ABTS, DPPH, FRAP and phenolic acids, implying the comparable capabilities of scavenging the DPPH/ABTS free radicals and reducing ferric ions from the antioxidant compounds in the samples. Phenolic acids contributed significantly to the antioxidant activities, and flavonoids contributed more to tannin content based on the correlations. Overall, methods modified and standardized in this study can provide better understanding of high throughput technologies and increase the reliability of antioxidant data of different plant foods.
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ItemEffect of a polyphenol-rich plant matrix on colonic digestion and plasma antioxidant capacity in a porcine model(Elsevier, 2019-06-01)Altering cellular structure by reducing the particle size and applying heat may enhance the release of polyphenols from the plant cell matrix. The released polyphenols could ameliorate the impacts of a high-fat diet. Using a pig model in a 2 × 2 cross-over trial, we tested the effects of processing on the bioaccessibility of polyphenols in the diet, using low- and high-fat diets supplemented with raw and diced or cooked and pureed black carrots. Raw diced black carrots resulted in higher average particle size in the digesta of all gastrointestinal compartments and higher total and major short chain fatty acids in the descending colon. Supplementing the diet with raw and diced carrots also increased the colonic bacterial counts but with limited effects on gut microbiome diversity. The presence of carrots did not mitigate the negative impacts of decreased plasma antioxidant capacity and high atherogenic index induced by a high-fat diet.