Antioxidant and Vasodilator Activity of Ugni molinae Turcz. (Murtilla) and Its Modulatory Mechanism in Hypotensive Response

Figure 5

Proposed model for the hypotensive mechanisms of Murtilla fruit extract. The phenolic compounds in Murtilla activate the vasorelaxation response partially by nitric oxide synthase (NOS)/guanylate cyclase when the tissue is exposed to low concentrations of the extract, while at high concentrations the effect is unspecific or vasodilation could be regulated by an alternative pathway. However, when the smooth muscle cell is blocked using a protein kinase G inhibitor, the effect is no longer dependent on eNOS; otherwise it is apparently modulated by an alternative pathway, as we did not observe an inhibitory effect upon stimulation with the extract. In the smooth muscle cell, there could be a hyperpolarization phenomenon leading to vasorelaxation when small-conductance channels are inhibited, probably because large-conductance channels remain active and enhance the vasodilator effects of the extract. In other words, this hyperpolarization in smooth muscle cells leads calcium channels to close, so decreasing the concentration of intracellular calcium and inducing vasodilation.