Definitions for "Pro-oxidant"
Any chemical compound that enhances oxidation. Under some conditions, some phytochemicals have been shown to act as pro-oxidants, one reason scientists wave people off supplements. Americans often assume - wrongly - that if a little of something is good, a lot must be better. If you're talking spinach, you probably can't (or won't) eat too much; if you're talking milligrams of sulphorophane in a capsule, you might do harm. With the exception of vitamin E, too little is known about most phytochemicals to mega-dose.
a substance which causes the production of free radicals
Compounds or agents capable of generating toxic oxygen species.