Abstract
Quercetin is proven to decrease arterial blood pressure when given orally. Its bioavailability is, however, low and, therefore, its metabolites could rather be responsible for this effect. In particular, the colonic metabolites of quercetin, 3,4-dihydroxyphenylacetic acid (DHPA), 4-methylcatechol (4MC), and 3-(3-hydroxyphenyl)propionic acid (3HPPA), have been previously shown to decrease the blood pressure in spontaneously hypertensive rats (SHR). Interestingly, the mechanisms of action of these three metabolites are different. The aim of this study is hence to investigate if these metabolites can potentiate each other and thus decrease blood pressure in reduced doses. Three double-combinations of previously mentioned metabolites were administered to SHR as infusions to mimic a real biological situation. All combinations significantly decreased the blood pressure in SHR but there were important differences. The effect of DHPA and 4MC was mild and very short. A combination of DHPA with 3HPPA caused more pronounced effects, which were also rather short-lived. The last combination of 3HPPA and 4MC caused a long-lasting effect. In conclusion, certain combinations of quercetin metabolites have a more pronounced antihypertensive effect than single metabolites.
Highlights
It is well known that some flavonoids administered orally can decrease arterial blood pressure [1,2]
There are some data on conjugates of flavonoids [6], colonic metabolites seem to be more active vasodilators, as was shown recently ex vivo as well as in vivo in spontaneously hypertensive rats (SHR) [7,8]
Previous pharmacodynamic studies were designed to test the effects of single metabolites
Summary
It is well known that some flavonoids administered orally can decrease arterial blood pressure [1,2].The bioavailability of parent flavonoids is low [3] and the observed effect could be mediated by their metabolites [4,5]. There are some data on conjugates of flavonoids [6], colonic metabolites seem to be more active vasodilators, as was shown recently ex vivo as well as in vivo in spontaneously hypertensive rats (SHR) [7,8]. 4-methylcatechol (4MC), and interestingly their mechanisms of action were different [7,8]. Data on their pharmacokinetics are limited, but available studies have shown that at least in the cases of 3HPPA and a sulfate conjugate of 4MC, their plasma levels can reach units of μM after administration of a polyphenol reach diet [9,10,11,12]. In continuation of our research, we decided to test three double-combinations of these most active metabolites in reduced doses to investigate whether they could produce a synergic vasodilatory effect
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