Here is a review article on plant based anticancer molecules. You can check if any of these molecules has antioxidant property by searching the literature or databases such as Dr. Duke's phytochemical database.
My comment here might come little immature as I am not giving this opinion after considering a huge data set, but relying on an abstract concept.
Now coming to the point, I think Flavonoid group of compounds are more often reported to have an anti-oxidant property/ free radical scavenging activity. Although Flavonoids are also reported to have anti-cancer activity, but in my assumption Glycosides & Terpenes (some times alkaloids also) are more frequently reported to have an anticancer activity.