The effects of defatted safflower seed extract and its phenolic constituents, serotonin derivatives, on atherosclerosis were studied. Ethanol-ethyl acetate extract of safflower seeds (SSE) inhibited low-density lipoprotein (LDL) oxidation induced in vitro by an azo-containing free-radical initiator V70 or copper ions. Two serotonin derivatives [N-(p-coumaroyl)serotonin, CS; N-feruloylserotonin, FS] and their glucosides were identified as the major phenolic constituents of the extract. The study with chemically synthesized materials revealed that a majority of the antioxidative activity of SSE was attributable to the aglycones of these two serotonin derivatives. Orally administered CS and FS suppressed CuSO(4)-induced plasma oxidation ex vivo. Long-term (15 week) dietary supplementation of SSE (1.0 wt %/wt) and synthetic serotonin derivatives (0.2-0.4%) significantly reduced the atherosclerotic lesion area in the aortic sinus of apolipoprotein E-deficient mice (29.2-79.7% reduction). The plasma level of both lipid peroxides and anti-oxidized LDL autoantibody titers decreased concomitantly with the reduction of lesion formation. Serotonin derivatives were detected as both intact and conjugated metabolites in the plasma of C57BL/6J mice fed on 1.0% SSE diet. These findings demonstrate that serotonin derivatives of SSE are absorbed into circulation and attenuate atherosclerotic lesion development possibly because of the inhibition of oxidized LDL formation through their strong antioxidative activity.
We previously demonstrated that safflower seed extract (SSE) and its major antioxidant constituents, serotonin hydroxycinnamic acid amides, suppressed LDL oxidation in vitro, decreased plasma autoantibody titres to oxidized LDL and attenuated atherosclerotic lesion formation in apoE-deficient mice. In this report, we examined whether SSE, rich in serotonin derivatives, could affect markers of oxidative stress, inflammation and aortic stiffness in healthy human subjects. Twenty Japanese male volunteers were studied at baseline, after 2·1 g SSE supplementation daily (providing 290 mg serotonin derivatives/d) for 4 weeks, and after a 4-week washout period. Significant reductions in circulating oxidized LDL, autoantibody titres to malondialdehyde-modified LDL, the soluble form of vascular cell adhesion molecule-1 (sVCAM-1), and urinary 8-isoprostane were observed after a 4-week intervention. Although there were no statistically significant differences in blood pressure or brachial-ankle pulse wave velocity (baPWV), an index of arterial stiffness, baPWV was lower than baseline in eleven of twenty subjects and was accompanied by a reduction in blood pressure. Statistically significant negative correlations were observed between the extent of initial cardiovascular risk markers (autoantibody titres, 8-isoprostane, sVCAM-1 and baPWV) and the effect of intervention. This suggested that individuals with elevated oxidative stress, inflammation, and/or arterial stiffness may receive more benefit from SSE supplementation.
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