Anthraquinones (AQs) rubiadin (1), 1-rubiadin methyl ether (2), soranjidiol (3), 1-soranjidiol methyl ether (4) and 5-5`-bisoranjidiol (5) isolated from Heterophyllaea pustulata are type I and/or II photosensitizers. Previously, we have demonstrated that (1), (2), (3) have photodynamic activity (PA) on human cancer cells. In this work, we evaluated the uptake of AQs into cancerous cells and its subcellular localization. Indeed, the PA of (4) and (5) was assessed. To determine the incorporation and localization of (1), (2) and (3) the cells were incubated with each AQ. For uptake, the analysis of AQs in each fraction (extracellular/ intracellular) was realized by HPLC whereas the intracellular pattern was observed by fluorescence microscopy. To evaluate the PA, cells were loaded with the AQs (4) and (5) and immediately exposed to 1 J/cm2. The cellular viability was analyzed by MTT. Controls without AQs were processed under same conditions.
The results showed that AQs (1), (2) and (3) were incorporated in the cancer cells and localized mainly in the cytoplasm. The AQs (4)-(5) caused outstanding PA. According to the obtained, these AQs tested might be possible candidates for future studies in photodynamic therapy.