Consider asking the authors of this paper: https://www.researchgate.net/publication/11476045_Absolute_Stereostructure_of_Potent_a-Glucosidase_Inhibitor_Salacinol_with_Unique_Thiosugar_Sulfonium_Sulfate_Inner_Salt_Structure_from_Salacia_reticulata

You will need to get some reference compound since you are using UV and compare to the retention time and UV-vis spectrum.

Article Absolute Stereostructure of Potent ??-Glucosidase Inhibitor,...

You have a 'tough job'.  From what I can see Salacinol has no Carbon double bonds which is the source of a good UV spectrum (>210 nm).  Dissolve a 'pure' reference standard in the solvent system given in the paper and scan in the UV.  If you do not obtain a wavelength maximum you will have to use a different detector like MS.

True about the potential lack of chromophore. ELSD (evaporative light scattering detector) would detect the compound, and is a lot less expensive than MS.

I would give the UV detector a try since dialkylsulfides absorb in the UV at 230nm, see link. I couldn't find much in the literature on the UV absorbance on the thionium ion which is present in Salacinol.

http://pubs.acs.org/doi/pdf/10.1021/ja01169a025