Antihypertensive and Vasorelaxant Effects of Citric Acid and Lemon Juice in Spontaneously Hypertensive Rats: In Vivo and Ex Vivo Studies.

Hypertension is a key risk factor for heart, brain, and kidney disease development. Fruit consumption has been associated with a decrease in blood pressure. Lemon juice, which contains antihypertensive compounds, may exert antihypertensive effects. However, no research has verified the antihypertensive effects of citric acid, the most abundant ingredient in lemon juice. In the present study, we demonstrated the antihypertensive effects of citric acid and lemon juice by performing single oral administration tests and the aortic ring assay using spontaneously hypertensive rats (SHRs). Single oral doses of both agents markedly reduced the systolic and diastolic blood pressures in the SHRs. In addition, both these agents relaxed the thoracic aorta from the SHRs; however, these effects were notably attenuated by the removal of the aortic endothelium. Orally administered citric acid was rapidly absorbed and metabolized in vivo. Among the functional compounds in lemon juice, citric acid was identified as the primary antihypertensive component. Although more detailed studies are required to validate our findings, the novel functional attributes of citric acid can achieve the normalization of blood pressure when it is consumed via diet.

Effects of halide ions on the acceptor phase in spontaneous chemical oscillations in donor/membrane/acceptor systems.

The effects of halide ions on the acceptor phase in the chemical oscillation in donor/membrane/acceptor systems were examined. The transfer of cetyltrimethylammonium (CTA(+)) ions from the donor phase and their adsorption and desorption at the membrane/acceptor interface led to spontaneous, nonlinear oscillations of the electric potential. Chloride ions stabilized the adsorption of CTA(+) ions and gave rise to a large-amplitude, long-interval, and a long relaxation-time constant. On the contrary, iodide ions, which are more hydrophobic than chloride ions, demonstrated opposite results. This mechanism was proposed based on the simultaneous time-resolved measurements of the interfacial tensions at both the donor/membrane and membrane/acceptor interfaces and observation of the convective flow due to Marangoni instability.

Spontaneous oscillation mechanism by simultaneous time-resolved measurements of interfacial tensions of both the donor/membrane and membrane/acceptor phases.

The time courses of the interfacial tension of two interfaces and the electric potential between the donor/membrane/acceptor phases were simultaneously examined using a quasi-elastic laser scattering method, which monitors capillary wave frequencies. An aqueous solution of cetyltrimethylammonium bromide (CTAB), a nitrobenzene solution of tetrabutylammonium tetraphenylborate (TPATPB), and an aqueous solution of sodium chloride (NaCl) were used as the surfactant in the aqueous donor phase, the hydrophobic electrolyte in the organic membrane phase, and the electrolyte in the aqueous acceptor phase, respectively. It has been found that the oscillatory behavior of the potential is synchronized with that of the interface tension at the membrane/acceptor interface, which is caused by the feeding and the following rapid adsorption of CTA(+) surfactants to it due to the Marangoni effect. The dependence of the interfacial tension on a co-surfactant, 1-butanol, and the electrolyte, NaCl, was also examined in order to clarify the relationship among the interval and the amplitude in the oscillatory electric potential behavior.