In a recent study, gastric fluid was made artificially and adjusted to pH 1 (which is that of the actual gastric fluid) and CBD was dissolved in methanol. About 85% of the present CBD isomerized to a mixture of D9- and D8-THC.
Theoretically, because of similar chemical structure between CBD and THC, the possibility of CBD conversion to THC, using a series of acid treatments and extraction by chromatography techniques, remains valid. Indeed, a patent application has been filed describing the series of steps to accomplish this.
See the original article at RxLeaf