Do centrifugal juicers destroy vitamins through friction?
Short answer is no. Vitamins are organic compounds (that is, compounds based on a carbon skeleton) which are pretty small: most of them are formed by 20-30 atoms, not more than that.

Mechanical stress, as well as thermic stress, can indeed interfere with the structure of big organic compounds such as proteins or DNA, which are called macromolecules and are formed by thousands or even millions of atoms connected in complex 3D structures. However, this is not the case for vitamins.

So, in substance, continue to drink your orange juice and you'll be fine!

EDIT: standing what I wrote, it is also interesting to consider that certain vitamins can be enzymatically degraded. This is for instance the case of vitamin C: this article demonstrates how vitamin C degradation could happen when processing broccoli at &lt;60°C, due to the action of an enzyme called vitamin C oxydase. Of course this does not necessarily apply to other vegetables/fruit or to other vitamins.

Personally, I think that the passage of a fruit in a juicer is sufficiently fast that I really doubt there would be enough time for the vitamins to degrade. Would be an interesting experiment to do though.