Psiadia punctulata major flavonoids alleviate exaggerated vasoconstriction produced by advanced glycation end products

Abstract

Exaggerated vasoconstriction plays important roles in vascular complication in aging and many diseases like diabetes. Here, we investigated the protective effect of Psiadia punctulata (PP) on advanced glycation end products (AGEs)-induced aggravated vasoconstriction. The effect of total methanol extract of PP leaves (PPT) on AGE-induced vascular injury was studied through bioassay-guided fractionation procedures in order to find the bioactive fraction and isolate the bioactive compounds. Vascular reactivity was studied using the isolated artery technique by adding cumulative concentrations of phenylephrine (PE) or acetyl choline (ACh). In addition, the antiglycating effect, as well as the effect on AGEs intermediates dityrosine and N`-formylkynurenine and their radical scavenging activity were measured. The results showed that PPT alleviated the AGEs-induced aggravated vasoconstriction in a concentration-dependent manner. The bioassay guided fractionation procedures suggested the chloroform fraction (Fr I) to be responsible for the activity. Chemical investigation of this fraction resulted in isolation of four major bioactive compounds that were identified as: umuhengerin (1), gardenin (2), luteolin-3`,4`-dimethyl ether (3), and 5,3`-dihydroxy-6,7,4`,5`-tetramethoxyflavone (4). The four compounds alleviated the exaggerated vasoconstriction in a dose dependent manner. In search for their mechanism of action, we observed that PPT, Fr. I and the isolated compounds did not improve the impaired vasodilation associated with AGEs exposure. PPT, Fr. I and the isolated compounds 1-4 inhibited AGEs formation and their protein oxidation intermediates. Furthermore, PPT, Fr. I and the isolated compounds 1-4 showed weak radical scavenging activity with compound 4 as the most potent. In conclusion, PPT appears to protect against AGEs-induced exaggerated vasoconstriction through antiglycation and radical scavenging activities.

Fig 1. Chemical structures of isolated compounds from P. punctulata.

Fig 2

Effect of one hour incubation of different concentrations of PPT (A), Fr. I (B), and isolated compounds 1–4 (C-F) on the AGEs-induced aggravated responsiveness to PE of aortae isolated from normal rats. #P < 0.05, compared with the corresponding control values; *P < 0.05, compared with MG group; by Tow Way ANOVA and Bonferroni post hoc test.

Fig 3

Effect of one-hour incubation of different concentrations of PPT (A), Fr. I (B), and isolated compounds 1–4 (C-F) on the AGEs-induced impaired vasorelaxant responsiveness to ACh of aortae isolated from normal rats. #P < 0.05, compared with the corresponding control values; *P < 0.05, compared with MG group; by Tow Way ANOVA and Bonferroni post hoc test.

Fig 4. Effect of different concentrations of PPT, bioactive fraction (Fr. I), and isolated compounds 1–4 on the formation of fluorescent AGEs when BSA is incubated with MG for one hour.

AG was used as standard anti AGEs drug. Results are expressed as mean ± SEM (n = 3). # p < 0.05 when compared to control group, * p < 0.05 when compared to MG group; by Two Way ANOVA and Bonferroni post hoc test.

Fig 5

Effect of different concentrations of PPT, bioactive fraction (Fr. I), and isolated compounds 1–4 on the formation of fluorescent dityrosine (A) and N`-formylkynurenine (NFK), (B) when BSA is incubated with MG for one hour. AG was used as standard anti AGEs drug. Results are expressed as mean ± SEM (n = 3). # p < 0.05 when compared to control group, * p < 0.05 when compared to MG group; by Two Way ANOVA and Bonferroni post hoc test.

Fig 6

Free radical scavenging activity of different concentrations of PPT (A), Fr. I (B), and isolated compounds 1–4 (C-F) by the DPPH radical assay. DPP^● radical (violet color) reacts with the extract, bioactive fraction or the isolated compounds to give the reduced form DPPH (pale yellow color) and the intensity of color decreases over time (10 minutes). Data are expressed as percentage decrease of the initial DPPH absorbance. *P < 0.05, compared with the control group; by Tow Way ANOVA and Bonferroni post hoc test.