The Hypotensive and Vasodilatory Effects Observed in Rats Exposed to Chiranthodendron pentadactylon Larreat Flowers Can Be Attributed to Cyanidin 3- O-Glucoside

Abstract

Chiranthodendron pentadactylon Larreat is a tree native to southeastern Mexico and Guatemala. Its flower is used in Mexican folk medicine to treat a variety of diseases, including conditions of blood pressure. However, scientific information on its usefulness in this pathology is lacking. The present study evaluates the effect of a methanolic extract (ME) from the flower and its active constituents on heart rate (HR) and mean arterial pressure (MAP) in anesthetized rats (MAPHR). The study also analyzed the effects on rat-isolated aortic rings (RIAR) and the rat mesenteric arterial bed (MABR). Active fractions were chromatographed, which led to the isolation of cyanidin 3-O-glucoside (C3G) identified through HPLC. The Chiranthodendron pentadactylon flowers produced hypotensive and vasorelaxant effects associated with C3G. The vasorelaxant effect is a mechanism underlying the synthesis and release of nitric oxide (NO). Neither cholinergic receptors nor prostaglandins are involved. ME and C3G cause cardiovascular depression in anesthetized rats via cholinergic and prostanoid mechanisms. Our research expands the scientific understanding of the flowers on the rat cardiovascular system. This amplifies the appreciation of the flower's ethnomedicine employed to control blood pressure. However, researchers need to conduct toxicity studies to determine the safety of this plant.

Keywords: Chiranthodendron pentadactylon; Wistar rat; antihypertensive; cyanidin 3-O-glucoside; vasorelaxant.

Figure 1

The UV-Vis spectrum of purified C3G dissolved in acidified methanol (0.01% v/v) with HCl.

Figure 2

HPLC chromatogram of C3G isolated from Chiranthodendron pentadactylon flowers and the C3G standard.

Figure 3

Calibration curve of the C3G standard.

Figure 4

Effect of increased ME, C3G, and ACh doses on the MAP (A) and HR (B) of rats under anesthesia. ACh shows the functionality of the experimental model’s reactivity. The abscissae correspond to the incremented doses of the treatments, with a sample size of six for each treatment. ACh is quantified in µg, while ME and C3G are measured in mg. The ordinates show changes in MAP or HR. The symbols represent the mean ± SEM (standard error of the mean) of six experiments. ✱ shows the significant difference between the control MAP and ME values, and # shows the significant difference between the control HR and C3G values. p < 0.05 ANOVA post hoc Dunnett’s test.

Figure 5

Effects of a single dose of 56 mg/kg of whole ME and its active principle C3G on MAP (A) and HR (B) of anesthetized rats. The control group receives normal saline (NS). The abscissas correspond to the recorded time of each treatment, with a sample size of six for each treatment, and the ordinates show changes in MAP or HR. The symbols represent the mean ± SEM of six experiments. ✱ shows the significant difference between the control and C3G values, and # shows the significant difference between the control and ME values. p < 0.05 ANOVA post hoc Dunnett’s test.

Figure 6

Effect of 15 mg/kg i.v. of the aqueous and ethyl acetate extracts on the MAP and HR of anesthetized rats. Both extracts were obtained from the whole ME of the Chiranthodendron pentadactylon flowers. The abscissas correspond to the treatments administered, with a sample size of six for each treatment, and the ordinates show changes in the MAP or HR. The bars represent the mean ± SEM of six experiments. ✱ shows the significant difference between the control MAP and ethyl acetate extract values, and # shows the control versus NS (normal saline) values. p < 0.05 ANOVA post hoc Dunnett’s test. In HR, there were no significant differences.

Figure 7

Effects of pretreatments with either atropine, indomethacin, or L-NAME on the changes induced by C3G in the MAP (A) and HR (B) of anesthetized rats. Abscissae corresponds to increased C3G doses in different pretreatments with a sample size of six for each treatment, and the ordinates show changes in MAP or HR. The symbols represent the mean ± SEM of six experiments. ✱ Shows significant differences between the control and C3G + atropine values, # the control versus C3G + Indomethacin values, and ∞ the control versus C3G + L-NAME values (A,B). p < 0.05 ANOVA post hoc Dunnett’s test.

Figure 8

Effects of ME (A) or C3G (B) extracted from the Chiranthodendron pentadactylon flowers on the RIAR system. Abscissae correspond to increased concentration in different pretreatments, with a sample size of eight for each treatment, and the ordinates show relaxation in percent changes. The symbols represent the mean ± SEM of eight experiments. ✱ shows a significant difference between the vasorelaxant effect produced by the control versus ME values with Endothelium (E) < 20%; # shows the control versus ME E > 80% (A); and ✱ shows a significant difference between the vasorelaxant effect produced by the control and C3G E < 20% (B). p < 0.05 ANOVA post hoc Dunnett’s test.

Figure 9

Effects of pretreatments with either atropine, indomethacin, ACh, or L-NAME on the vasorelaxant effect produced by ME (A) or C3G (B) in the RIAR system. The abscissae correspond to an increased concentration. Ordinates show changes in the vasorelaxant effect caused by ME (A) or C3G (B) with several pretreatments, with a sample size of eight for each treatment. The symbols represent the mean ± SEM of eight experiments. ✱ shows a significant difference between control and ME + L-NAME values (A) and between control and C3G + L-NAME values (B). p < 0.05 ANOVA post hoc Dunnett’s test.

Figure 10

Effect of ME (A) or C3G (B) on the concentration-response curve produced by NE in mesenteric vascular beds from rats. The abscissae show increases in NE concentration. Ordinates show changes in mm Hg of the perfusion pressure caused by several treatments, with a sample size of six for each treatment. The symbols represent the mean ± SEM of six experiments. ✱ shows a significant difference between the control and NE + ME values and # the control versus NE + prazosin values (A); and ✱ control versus NE + C3G values and # control versus NE + prazosin values (B). p < 0.05 Student’s t-test for two related samples.

Figure 11

Effect of C3G in the presence or absence of L-NAME on the concentration-response curve produced by NE in mesenteric vascular beds from rats. The abscissae show increases in NE concentration. Ordinates show changes in mm Hg of the perfusion pressure caused by several treatments, with a sample size of eight for each treatment. The symbols represent the mean ± SEM of six experiments. ✱ shows a significant difference between the control and NE + C3G values. p < 0.05 Student’s t-test for two paired samples.