Vasodilatation Produced by Orientin and Its Mechanism Study

Abstract

Bamboo leaves, Phyllostachys nigra (LODD. ex. lind-1 MUNRO. L), have been used as a Chinese medicament for thousands of years. Theses leaves have anti-free radical activity and are comparable with the leaf of Ginkgo bilabo, which is one potential resource for natural antioxidant and free radical scavenger. 1) Our previous investigation revealed that bamboo leaves have significant effects on protecting myocardial ischemia in rat, restraining blood platelet aggregation of rabbit, increasing coronal flow and have a vasorelaxant effect on rabbit thoracic aortic rings, and also reduce arterial blood pressure. Here, we further investigated the vasorelaxant effect of four flavonoid C-glycosyl compounds ( Fig. 1): Orientin (Luteolin-8-C-glucoside), Isoorientin (Luteolin-6-Cglucoside), Isovitexin (Apigenin-6-C-glucoside), and Vitexin (Apigenin-8-C-glucoside), first isolated from bamboo leaves, all of which are also found in numerous plants. 2,3) It is reported that these flavonoids possess anxiolytic properties 4,5) and that Orientin possesses antioxidative activity, 6) however, there is no information about the vasorelaxant effect of these compounds. In the present investigation, we examined the vasodilatation effects of these flavonoid C-glycosyl compounds and found only Orientin produced a vasorelaxant effect on rabbit aortic rings. The data from the present study suggested that Orientin relaxed thoracic aortic rings by the nitric oxide-guanosine 3,5-cyclic monophosphate (cGMP) pathway, and in the vascular smooth muscle inhibited the contraction induced by the activation of receptor-operating and voltage-dependent Ca 2ϩ channels. Cyclooxygenase pathway, potassium channels, b-receptors and adenosine-3Ј,5Ј-cyclic phosphoric acid (cAMP) pathway, on the other hand, had no apparent roles. The inhibition of both intracellular Ca 2ϩ release and extracellular Ca 2ϩ influx may be one of the main vasorelaxant mechanisms of Orientin. MATERIALS AND METHODS Animal

Changes in phenols contents from buckwheat sprouts during growth stage

“…These results suggest that we can harvest buckwheat sprouts containing high levels of phenols in a relatively short amount of time with our cultivation method as compared to the open field cultivation. It has been reported that orientin has a vasodepressor effect and antioxidant activity, isoorientin has avasorelaxant effect, and vitexin has antibacterial action (Fu et al 2005;Budzianowski et al 1991;Afifi et al 1999;Afifi et al 1997). These phenolic ingredients can afford protection and recuperation for those who have lifestylerelated diseases (Iwai et al 2006;Ojewole 2006).…”

Endothelium-Dependent Vasodilatory and Hypotensive Effects of Crotalaria Sessiliflora L. in Rats

“…In accordance with this hypothesis, orientin and vitexin, which are also contained in this plant, were demonstrated to have vasodilatory effect. 18,19) In the case of some flavonoid compounds, it has been shown that they induce an increase of [Ca 2ϩ ] i , which in turn, by activating the endothelial NOS, induces the synthesis/release of NO. 18,27,28) A similar mechanism may be involved in the relaxation observed in the present study.…”

“…17) Furthermore, flavonoids such as vitexin and orientin present in many plants are known to have vasodilatory effect. 18,19) Therefore the aim of the present study was to investigate the vasodilatory effect and underlying mechanism of extract from C. sessiliflora L. PE, L-NNA, methylene blue, ruthenium red, IBMX, atropine, and acetylcholine were dissolved in deionized water or sterilized physiological saline. PGF 2a was dissolved in ethanol and further diluted with deionized water.…”

Vasodilatory Effect of Wogonin on the Rat Aorta and Its Mechanism Study

“…Then the following experiments were done. [15][16][17][18][19][20][21] 1) To investigate the vasodilatory effect of wogonin, NE (1 µM) or KCl (60 mM) was used to contract the aortic rings. Once a stable contraction was achieved, wogonin (0.1-100 µM) was added cumulatively.…”