The Collaborative International Dictionary of English v.0.48:

Dextro- \Dex"tro-\
   A prefix, from L. dexter, meaning, pertaining to, or toward,
   the right; (Chem. & Opt.) having the property of turning the
   plane of polarized light to the right; as, dextrotartaric
   acid.
   [1913 Webster]