Halostachine HCl is too hygroscopic.
Halostachine-theobromine did not work (ends up as simple mixture of halostachine and theobromine rather than new compound)
Halostachine itself may be unstable to oxidation, but would solve water-absorption problem.
3 possible solutions:
1) Halostachine salt such as the sulfate that happens to not be so hygroscopic
2) Halostachine HCl combined with an excipient that reduces the hygroscopic problem, for example an activated silica
3) Halostachine combined with an excipient protecting it against oxidation