Antioxidant acitivity - guided optimisation of polyphenols from onion soil waste employing water/ethanol mixtures
2006
Khiari, Z.
The purpose of this thesis was to extract the phenolic compounds from onion solid waste. The compounds of interest were quercetin, its glucosides (mono and di glucosides) and its oxidation products. These compounds are known by their proposed health promoting effects as antioxidants and anticarcinogens. High-performance liquid chromatographic mass spectrometry methods for the screening of these phenolic compounds and for the quantification of flavonols were used. The stability of these compounds was also studied. When the onion flavonols were subjected to degradation, four products were identified; quercetin, quercetin monoglucoside, Protocatechiuc acid and other oxidation products. Finally, an optimization of the out; it was found extraction process was carried that there is not a standard protocol to maximize all the parameters together. A solvent of 90 percent EtOH is sufficient to get the highest level of anthocyanins. Regarding the antioxtdant potency, a solvent of 60 percent EtOH and 0.1 percent HC1 should be used. Concerning the time and temperature effect, it was observed that 360 min soaking at 40 deg C was the optimum.
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