First of all, DOMS is an independent result of muscle damaging exercise (meaning it does its own thing and isn't readily affected by treatment that affects other indicators of muscle damaging exercise). The same volume/intensity will not affect everyone the same, including similarly matched novice exercisers. DOMS isn't strongly related to other indicators of muscle damage, but we know it will decrease with repeated training bouts. Fact is, exercise is going to leave you sore when you start something new--new rep scheme, new exercises, etc--and when you really push it, especially to failure. NSAIDS--natural or otherwise--might take the edge off the pain, but other indicators will be there (decreased force output, swelling, increased CK, etc), especially if you fit into one of the categories I already mentioned.
Further, while free radicals may play a role in exercise fatigue, fatigue != DOMS. Fatigue is a combination of neuromuscular and biochemical factors not worth getting into here. Suffice to say, a great many things play a role in exercise fatigue.
Finally, free radicals may have a role in DOMS, but the jury's still out. A quick Google Scholar search netted me a few recent articles on the matter, the most promising being "Eccentric exercise, isokinetic muscle torque and delayed onset muscle soreness: the role of reactive oxygen species." Interestingly enough, the researchers found that ROS (free radicals) peaked after pain and decreases in muscular function had already subsided. Also, the researchers went as far to say that the increase in ROS may aid in the removal of damaged cells to allow for regeneration to occur! I skimmed many of the articles that cite this study, and the consensus seems to be that DOMS is what I originally called it: an independent result of muscle damaging exercise that is unaffected by treatment.
