Well this is rather annoying, I wrote a nice long post detailing the chemicals in peppermint and whether they had any effect on the vascular system, but it seems my computer decided to crash. Anyway here it goes again.
Firstly, I looked up those chemicals that were in peppermint, and cross referenced this from a few different sources incase some had been missed out. Anyway I think I got a list of all the major ones in the end.
volatile oils (composed mainly of menthol, menthone, and menthylacetate, with smaller amounts of menthofuran, limonene, pulegone, cineole, bisabolene, isomenthol, neomenthol), flavonoids, phytol, tocopherols, carotenoids, betaine, choline, azulenes, rosma
There were also a few other chemicals from different sources but this seemed to be the most complete list. The others which occured enough to be worried about were pinene and germacrene, however I made sure to check these and found them to have no effect on cardiovascular system.
Anyway, I had a quick look at each chemical that came up to see if it had any obvious role on the cardovascular system and found that of those listed only menthol, neomenthol, flavanoids, and tocopherols had any action.
Rather importantly I suppose I should point out that flavanoids and tocopherols are groups of chemicals, and so there is a possibility that the actual chemicals present in peppermint act differently. However, I found that both of these groups have an effect on the cardiovascular system, but mainly vasoprotective properties. Basically keeping the heart and blood vessels healthy, and protecting from CHD. No obvious vasocontricting effects.
Then I took a deeper look at menthol and neomenthol, both of which only returned an account of vasodilating effects much like ethanol
Like Jasim said this is slightly confusing as it is plastered all over the internet of its vasoconstricting effects. However I can find no evidence that it is from it's chemical make up. Best bet is a medical paper stating its actual effects on the human body and why, but I doubt anyone wil bother to set up such an experiment for peppermint.
Sorry if that was a bit long and borring I just wanted to clear things up. Maybe there would be a way of taking varying doses of peppermint and somehow recording the vascular effects, such as recording blood pressure?