Trend in Detection of Anthocyanins from Fresh Fruits and the Influence of Some Factors on Their Stability Impacting Human Health: Kinetic Study Assisted by UV-Vis Spectrophotometry.

Abstract

Anthocyanins (ANTHs) are polyphenolic compounds with health promoting properties, being known for their strong antioxidant effects as well as for their antimicrobial properties, obesity and cardiovascular disease prevention, and anticarcinogenic activity. Being main dietary components, it is important to know the content of anthocyanins in various dietary sources and their stability in time. The total anthocyanin content (TAC) of various fresh fruits has been spectrophotometrically determined using the pH differential method. The results showed that in the analyzed samples, the TAC increased in the order: blackcurrants > blackberries > blueberries > raspberries > strawberries > plums. The degradation degree of anthocyanins extracted from blueberries (BBEs) in an ethanol/water solution in four experimental conditions was studied. Kinetic studies have been approached, fitting the experimental data recorded by UV-Vis spectrophotometric analysis in agreement with some kinetic models verified for the ANTH degradation reaction. Therefore, zero-order kinetics for BBE extract degradation exposed to sunlight were identified, while for the other storage conditions (shadow, dark, cold), the first-order kinetics were respected. The results indicate that the stability decreased as follows: (ANTH stability)_{sunlight test} << (ANTH stability)_{shadow test} ≈ (ANTH stability)_{dark test} < (ANTH stability)_{cold test}. A mechanism for BBE anthocyanin degradation was proposed and the impact on human health of the degradation products is discussed.