Reactions of p-coumaric acid with nitrite: product isolation and mechanism studies.
p-Coumaric acid (1) is an abundant plant phenolic acid, a dietary chemoprotectant, and an antioxidant. The chemoprotective properties of 1 were demonstrated in vitro by its reaction with NaNO(2) in H(2)O over a range of pH values. The reaction pathway of 1 with nitrite is dependent on pH. 4-Hydroxybenzaldehyde (3, 16%), 1',4-dihydroxybenzeneacetaldehyde oxime (5, 59%), and 4-hydroxy-1'-oxo-benzeneacetaldehyde aldoxime (7, 26%) and 7-hydroxy-1,2(4H)-benzoxazin-4-one (11, 6%) were each formed at pH 2, whereas 4-(2-oxido-1,2,5-oxadiazol-3-yl)phenol (13) was formed at pH 3 (6%) and pH 7 and 10 (both 1%). Products were isolated and characterized by NMR and MS spectral analyses. Formation of benzoxazinone (11) requires the 4-phenolic functional group and the conjugated propenoic acid side chain of p-coumaric acid. The mechanism for nitrosation at pH 2 was examined by reacting 1 in H(2)(18)O/NaNO(2).
Torres y Torres
J L
JL
Division of Medicinal and Natural Products Chemistry and Center for Biocatalysis and Bioprocessing, College of Pharmacy, University of Iowa, Iowa City, IA 52242, USA.
Rosazza
J P
JP
D000975:Antioxidants / Q000737:chemistry; D003373:Coumaric Acids / Q000737:chemistry*; D004032:Diet; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D009573:Nitrites / Q000737:chemistry*; D011422:Propionates
D000975:Antioxidants; D003373:Coumaric Acids; D009573:Nitrites; D011422:Propionates; C495469:p-coumaric acid