The
off-flavor produced after thermal stabilization of mandarin
(Citrus reticulata, Blanco) juices
has limited the production of commercial juices. Methanethiol, a putrid-smelling
sulfur volatile, has been identified for the first time in heated
mandarin juices. Identification was achieved using a combination of
capillary gas chromatography with two dissimilar columns and a dual
sulfur-specific pulsed flame photometric detector and selected ion
mass spectrometry detection. Static headspace solid-phase microextraction
quantitation found that average odor activity values (OAVs) in heated
juices were 25.5 for methanethiol compared to 10.8 for dimethyl sulfide.
OAVs for methanethiol and dimethyl sulfide in fresh juices were ND
(not detected) and 5.5, respectively. Hydrogen sulfide, carbonyl sulfide,
carbon disulfide, and dimethyl disulfide were also identified and
quantitated. Thermal decomposition studies of nonvolatile sulfur-containing
potential precursors indicated that methionine was the major source
of methanethiol. Additional heating studies with model juices demonstrated
that ascorbic acid greatly accelerated the formation of methanethiol
and methional, as well as dimethyl di and tri sulfides.
Abstract:The prophylactic effects of the polymethoxyflavones (PMFs) in long-leaf orange peel oil (OPO) were determined using an N ω -nitro-L-arginine-induced hypertensive rat model. The OPO contained eight PMF components, namely sinensetin, hexamethoxyflavone, tetramethyl-Oisoscutellarein, nobiletin, tetramethyl-O-scutellarein, heptamethoxyflavone, 5-demethylnobiletin and tangeretin. After treatment with OPO, the SP (systolic pressure) and DP (diastolic pressure) in hypertensive rats were reduced. The NO (nitric oxide) contents in serum, heart, liver and kidney of OPO-treated N ω -nitro-L-arginine (L-NNA)-induced hypertensive rats were higher than those in untreated hypertensive rats, but the MDA (malondialdehyde) contents in OPO-treated rats were lower than those of the control rats (untreated hypertensive rats). ET-1 (endothelin-1), VEGF (vascular endothelial growth factor) and E-selectin serum levels in hypertensive rats could be reduced, but the CGRP (calcium gene-related peptide) level could be increased by OPO treatment. The results of the qPCR assay showed that OPO upregulated HO-1 (heme oxygenase-1), nNOS (neuronal nitric oxide synthase) and eNOS (endothelial nitric oxide synthase) mRNA expression and downregulated ADM (adrenomedullin), RAMP2 (receptor activity modifying protein 2) and iNOS (inducible nitric oxide synthase) expression in hypertensive rats. The Western blot results also proved that OPO upregulated nNOS and eNOS protein expression and downregulated iNOS expression in hypertensive rats. Based on this study, we could conclude that OPO showed good antihypertensive effects, and the effect was concentration dependent.
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