Cryptostrobin and catechin isolated from Eugenia mattosii D. Legrand leaves induce endothelium-dependent and independent relaxation in spontaneously hypertensive rat aorta.

Considering the therapeutic potential of phenolic compounds, the purpose of the present study was to investigate the mechanisms involved in the relaxation induced by cryptostrobin and catechin, isolated from Eugenia mattosii D. Legrand leaves, in the aorta of spontaneously hypertensive rats (SHR).The thoracic aorta was isolated from SHR and kept in the organ bath system by recording contractile or relaxant responses.

The addition of cumulative concentrations of cryptostrobin and catechin induced endothelium-dependent and-independent relaxation in aorta rings from SHR, as well as both compounds were effective in reducing phenylephrine-induced contraction. Pretreatment of aortic rings with N_m-nitro-L-arginine methylester (L-NAME, an inhibitor of nitric oxide synthase) or 1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one (ODQ, an inhibitor of soluble guanylate cyclase), resulted in a significant change of relaxant effect induced by catechin, and a slight influence on cryptostrobin-induced relaxation. Muscarinic receptor and potassium channels are involved in catechin-induced relaxation as assessed using atropine (a muscarinic receptor antagonist), tetraethylammonium (a non-selective K⁺ channel blocker) and glibenclamide (an ATP-sensitive K⁺ channel blocker). Conversely, cryptostrobin, but not catechin, blunted the contraction induced by the addition of phenylephrine in a calcium-free solution. Besides that, cryptostrobin attenuated the contraction of rat aorta rings induced by internal Ca²⁺ release and external Ca²⁺ influx.

These findings indicated that cryptostrobin and catechin alter vascular smooth muscle reactivity, and this effect may be involved, at least in part, by enhancing the endothelium NO/cGMP pathway and potassium channels activation. In addition, cryptostrobin reduced the phenylephrine, KC1 and CaCl₂-induced contractions in a calcium-free solution.