Our data are compatible with a scenario in which a population of the putative prohormones or proneuropeptides identified by Moroz and colleagues contains post-translationally modified, catecholic amino acids that would likely have gone undetected by assays designed to detect catechols
as solution-state small molecules.
The formation of catechol
as a byproduct of aniline biodegradation was detected at 270nm.
Thus, the oxidation mechanism for catechol
and hydroquinone on both surfaces is different.
The absorbance of the caffeic acid oxidation was monitored at 410 nm using different substrate concentrations (10-250 [micro]M); the catechol
oxidation absorbance was monitored at 390 nm with different substrate concentrations (100-1400 [micro]M); the gallic acid oxidation absorbance was monitored at 385 nm with different substrate concentrations (100-1400 [micro]M).
A Km increase accompanied with unmodified Vmax is characteristic of competitive inhibition, which usually occurs when the inhibitor has a chemical similarity with the substrate of the enzyme (catechol
in this case) and competes with the enzyme for the active site.
In the presence of an oxidant-generating environment, the phenolic hydroxyl group present at the C3 position of the A ring of estrogens or catechol
estrogens accepts electrons and gets oxidized by either accepting these electrons or losing a proton [12, 13].
Three flavonoids contain exclusively the catechol
group: (-)-epicatechin, (-)-epicatechin gallate, (+)-catechin, corresponding to 7.9% of the flavonoids.
A tyrosinase biosensor based on CB paste electrode showed remarkable analytical features toward catechol
biosensing, including a sensitivity of 625 nA [micro]mol [L.sup.-1] and a limit of detection of 8.0 x [10.sup.-9] mol [L.sup.-1].
The bands at 1640-1643 [cm.sup.-1] were assigned to the C=O stretching vibration of amide groups of free ligands, which shifted to 1588 [cm.sup.-1] in its corresponding complexes; meanwhile, the peaks at 1266 [cm.sup.-1] were attributed to the C-O stretching vibration of catechol
units shifted to 1256-1260 [cm.sup.-1] for their complexes, which indicated that oxygen atoms of phenolic hydroxyl take part in coordination with uranyl ion.
Most antioxidant studies on flavonoids have concluded that an ortho-dihydroxy (catechol
) structure in B ring is important for high scavenging activity [4, 5, 41-43].
They demonstrated several metabolic reactions in skin including glucuronidation, sulfation, N-acetylation, catechol
methylation, and glutathione conjugation.
Like olive oil, it also contains some vitamin E, along with small quantities of polyphenols such as caffeic acid, oleuropein, catechol