First off, the vast majority of plastics are immune to biological effects; that's why they're used in your body. That being said, it's possible to modify some plastics so they're biodegradable (my company does that for our doggie bags, so both the bag and the dog waste within will decompose in compost piles).
As it's been said before, it's contact with oxygen and UV radition in sunlight that causes the yellowing of plastics. I keep meaning to take some pics of the rollstock in my factory, you can clearly see where air was exposed to some parts and not others.
So no, rubbing alcohol wouldn't do anything to prevent yellowing.