The Collaborative International Dictionary of English v.0.48:

Lactonic \Lac*ton"ic\, a. [From Lactone.] (Chem.)
   Of, pertaining to, or derived from, a lactone.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lactonic \Lac*ton"ic\, a. [From Lactose.] (Chem.)
   Pertaining to, or designating, an acid obtained by the
   oxidation of milk sugar (lactose).
   [1913 Webster]