Thank you for raising this issue as I believe it is quite easy for active individuals to go low on specific micronutrients.
I would like to specify that the B-vitamin group does not directly contain any anti-oxidants. Also ingestion of antioxidants such as vitamin C is not recommended pre-workout either. http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.2014.279950/full
In reasonable amounts and post-workout or as far away as possible timewise should be fine since reactive oxygen species have already been released and done their "good" damage during the exercise.