Abstract
In this work a comparative study of the chemical composition and potential biological activity of high molecular weight (HMW) melanoidins isolated from instant soluble coffee (ISC) and instant soluble barley (ISB) was performed. ISB HMW melanoidins were almost exclusively composed by an ethanol soluble (EtSn) melanoidin fraction composed by glucose (76% w/w) partially susceptible to in vitro digestion, whereas ISC was composed mainly by arabinogalactans (~41% w/w) and lower amounts of galactomannans (~14% w/w) presenting a range of ethanol solubilities and resistant to in vitro digestion. Melanoidins from ISC presented a significantly higher content of condensed phenolic compounds (17/100 g) when compared to ISB (8/100 g) showing also a higher in vitro scavenging of ABTS•+ (329 mmol Trolox/100 g vs. 124 mmol Trolox/100 g) and NO radicals (inhibition percentage of 57 and 26%, respectively). Nevertheless, ISB EtSn melanoidins presented, on average a higher inhibitory effect on NO production from LPS-stimulated macrophages. ISB melanoidins, up to 1 mg/mL, did not induce toxicity in Caco-2, HepG2 and RAW 264.7 cell lines while at the highest concentration ISC slightly reduced cell viability. Thus, consumption of a diet rich in ISC and ISB melanoidins may reduce the oxidative stress, the inflammatory levels and increase the protective effects against chronic inflammatory diseases.
Highlights
Coffee is one of the most popular non-alcoholic beverages around the world with an estimated world annual consumption of 500 billion cups [1]
The high molecular weight material (HMWM) isolated from instant soluble barley (ISB), despite its brown colour, was largely composed by carbohydrates (93%), mainly glucose (88%) and smaller amounts of other sugars such as xylose, arabinose, galactose, and rhamnose
This chemical composition was significantly different from the HMWM isolated from instant soluble coffee (ISC) that was composed by 59% of carbohydrates, mainly galactose (38%) and mannose (13%), and lower amounts of arabinose and glucose
Summary
Coffee is one of the most popular non-alcoholic beverages around the world with an estimated world annual consumption of 500 billion cups [1]. One of the factors for this popularity is its caffeine content, the best-known psychoactive stimulant [2], that improves cognitive performance [3]. Besides caffeine, thousands of other constituents, Instant Soluble Coffee/Barley Melanoidins including carbohydrates, lipids, nitrogenous compounds, vitamins, minerals, alkaloids, and phenolic compounds [4, 5], some of them with potential health-beneficial properties. Debate still persists whether coffee is beneficial or troublesome for human health. Consumption of coffee may inhibit inflammation and reduce the risk of cardiovascular and other inflammatory diseases in postmenopausal women [10]
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