Differential diagnosis of gallstones by using hypericin as a fluorescent optical imaging agent

Figure 6 HPLC chromatograms of dimethyl sulfoxide/2-propanol (50%:50%, v/v) extracts from hypericin pre-incubated gallstones with UV (204 nm) and fluorescence detection (excitation/emission wavelengths: 470/600 nm). Under UV, cholesterol and mixed stone extracts showed a main peak with a retention time (RT) of 19.99 ± 0.17 min corresponding to cholesterol. With fluorescence detection, a single peak of hypericin at 9.68 ± 0.06 min was observed. In pigment stone extracts, the UV showed a large peak at 1.41 ± 0.02 min representing other non-cholesterol components in this type of stone. The second small peak with an RT of 19.81 ± 0.11 min corresponding to cholesterol was also observed. Under fluorescence, pigment stone extracts showed a smaller peak of hypericin than that in cholesterol and mixed stones. FLU: Fluorescence units; mAu: Milli-absorbance units; HPLC: High performance liquid chromatography.