Blood pressure synephrine effects

In 1937 Arnow showed that tyrosine could be converted into DOPA by ultraviolet radiation51 and that the DOPA produced in this manner was subsequently destroyed by further irradiation, the solutions becoming red-brown in color (presumably due to the formation of dopachrome).51 In 1939 Konzett and Weis reported that the blood pressure-raising effect of adrenaline solutions was lost on ultraviolet irradiation and that the solutions became colored and fluorescent the initial red color fades to reddish yellow.62 This phenomenon suggests the initial formation of adrenochrome, followed by its isomerization to adrenolutin, both of these compounds being virtually void of pressor activity. Similarly to the radiation-induced hydroxylation of tyrosine mentioned above, synephrine was first... 

There are limited animal and human data on the cardiovascular effects of C. aurantium. When administered to rats, C. aurantium and synephrine both raised blood pressure in a dose-dependent manner (31). In another study in rats, repeated oral C. aurantium extract led to dose-dependent cardiovascular toxicity and mortality (32). Two studies using synephrine or C. aurantium in rats with induced portal hypertension (by portal vein ligation) have been conducted (31,33). In these studies, both synephrine and C. aurantium significantly reduced portal venous pressure. Interestingly, C. aurantium had a greater effect on portal hypertension than synephrine alone. 

Several studies have recorded poor binding affinity of p-synephrine to a- and p-1- and P-2-adrenoreceptors (Brown et al. 1988 Jordan et al. 1987 Ma et al. 2010), which provides a mechanistic explanation for the lack of observed effects on blood pressure and heart rate in numerous animal and human studies (Stohs et al. 2011). 

Stohs, S.J., H.G. Preuss, S.C. Keith, PL. Keith, H. MiUer, and G.R. Kaats. 2011b. Effects of p-synephrine alone and in combination with selected bioflavonoids on resting metabolism, blood pressure, heart rate, and self-reported mood changes. Int.. Med. Sci. 8 295-301. 

Tyramlne Tyrosine Dopamine, epinephrine, norepinephrine, synephrine, hordenine Precursor of dopamine, local tissue hormone, increases blood pressure, effect on smooth muscle contraction... 

Many reports of adverse effects due to the use of bitter orange, as a replacement for ephedra, in weight-loss dietary supplements have reeently emerged. Some of the reported effects include ischemic colitis, angina, elevated blood pressure, and other cardiovascular effects. " Synephrine and/or octopamine are speculated to play a role in the advent of such effects. ... 

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