2 research outputs found
Degradation of Caffeic Acid in Subcritical Water and Online HPLC-DPPH Assay of Degradation Products
Caffeic acid was
subjected to degradation under subcritical water
conditions within 160–240 °C and at a constant pressure
of 5 MPa in a continuous tubular reactor. Caffeic acid degraded quickly
at these temperatures; the main products identified by liquid chromatography-diode
array detection/mass spectrometry were hydroxytyrosol, protocatechuic
aldehyde, and 4-vinylcatechol. The reaction rates for the degradation
of caffeic acid and the formation of products were evaluated. Online
high-performance liquid chromatography/2,2-diphenyl-1-picryhydrazyl
assay was used to determine the antioxidant activity of each product
in the solution. It was found that the overall antioxidant activity
of the treated solution did not change during the degradation process.
This study showed a potential of formation of antioxidants from natural
phenolic compounds under these subcritical water conditions, and this
may lead to a discovering of novel antioxidants compounds during the
extraction by this technique
Distribution of saccharides and salts on amphoteric ion-exchange resin
<p>An amphoteric ion-exchange resin hardly shrank in 550 and 300 g/L glucose and sodium chloride solutions, respectively; however, the bed packed with a cation-exchange resin shrank considerably. From the distribution coefficients of some saccharides, the swelling pressure of the amphoteric ion-exchange resin was estimated to be 2.0 MPa at 25 °C. The distribution coefficients of glucose, galactose, fructose, and mannose were independent of their concentration and were about 0.621. On the other hand, the apparent distribution coefficients of NaF, NaCl, NaBr, NaI, LiCl, KCl, and CsCl largely depended on concentration. A model for the distribution of salts on the amphoteric resin was proposed, assuming an interaction between the anion of the salt and the positively charged fixed ions with binding constant <i>B</i>. The <i>B</i> values of the chloride salts were nearly the same (1.69–2.94 L/mol), while the values of the sodium salts were largely different depending on the anion.</p