Vasoactive Effect Associated With Calcium Channel Blockade Through a Pitaya Juice Concentrate (Stenocereus Huastecorum): Identification of Bioactive Compounds.

OBJECTIVES: The aim is to evaluate the vasodilator effect of pitaya juice concentrate (PJC) in isolated rat aortic rings and to identify the responsible vasoactive compounds, as well as their mechanism of action. METHODS: The juice was obtained from S. huastecorum fruit. First, the fruit juice was centrifuged to obtain 1200 mL of PJC, 600 mL were frozen until use and 600 mL were lyophilized (LyPJC). LyPJC was fractionated by reverse phase chromatography. he profiling of the LyPJC was analyzed by HPLC-PAD and nuclear magnetic resonance (NMR). The vasoactive effect of PJC was evaluated in rings with (n = 5) and without endothelium (n = 5), pre-contracted with 10 mM phenylephrine (Phe). Next, 40 mg/mL of LyPJC was added, during 30 min. In separate experiments, the effect of 20 mM of tetraethylammonium ion (TEA, potassium channel blocker), or 200 nM of nifedipine (Nph, calcium channel blocker) was tested. Furthermore, the LyPJC fractions were evaluated in thoracic aorta rings and by patch clamp technique. RESULTS: The profiling of LyPJC by HPLC-PAD showed 16 types of betalains and 31 types of phenolic compounds. The NRM showed a type of betalain as the main compound of PJC. The LyPJC administration exhibited 4-fold greater vasodilation effect versus physiological solution (54.3% ± 14.1 vs 6.7% ± 3.7), endothelium independent. The TEA did not modify the vasodilator effect of LyPJC in rings. However, with Nph, the vasodilator effect was blocked. Finally, the 8 fractions obtained from LyPJC were evaluated in rings, only the first fraction (H(2)O: HOAc 1% without methanol) showed a vasodilatory effect. Patch clamp experiments showed that the LyPJC first fraction relaxing effect may be the result of its inhibitory effect on L-type calcium channels. CONCLUSIONS: PJC contains betalains and phenolic compounds, with a vasodilatory effect associated with calcium channel blockade in isolated rat aortic rings. The first fraction will be purified and analyzed by mass spectrometry and the exact compound will be determined. FUNDING SOURCES: Consejo Nacional de Ciencia y Tecnología (CONACYT- FORDECYT 296,354)-Instituto Potosino de Investigación Científica y Tecnológica A.C. (IPICYT).