RE: Antioxidant activity of vitamin B6 delays homocysteine-induced atherosclerosis
The homocysteine lowering effects of certain B vitamins are well documented in the scientific literature, as you say Nige.
I guess this study is showing that elevated homocysteine, due to B6 deficiency, causes measurable, deleterious effects on arterial structure and function and therefore indicates that compromised B6 status is a risk factor for cardiovascular disease.
Interestingly, I conducted a pilot study on the effects of folate supplementation on measures of oxidative stress. While the homocysteine lowering properties of folate are well known, I was investigating whether it exerted an antioxidant effect, for which there is a little evidence (see papers by Hilary Powers for more info). Unfortunately, I could not demonstrate such an effect (in fact, there was a non significant pro-oxidant effect of folate supplementation!)
It is possible that B vitamins exert their effects on the cardiovascular system through methods in addition to homocysteine lowering. As ever, it needs more research.