A novel hypocrellin B derivative designed and synthesized by taking consideration to both drug delivery and biological photodynamic activity

For making hypocrellins clinically applicable for phototherapy to vascular diseases, it is mainly focused onto finding a derivative which can be transported fluently in blood system but without serious loss of the inherent activity of its parents. Based on this consideration, a novel 17-3-amino-1-propane-sulfonic acid-HB Schiff-base (NSHB) was designed and synthesized in this work. As expected, NSHB is readily dissolved in phosphate buffered saline (PBS) or any other aqueous solvent in a concentration which is suitable for intravenous injection, while the quite higher partition coefficient (5:1) is beneficial to the affinity to biological targets. Based on EPR measurements, it is proved that the photosensitization activity of NSHB to photo-generate semiquinone anion radicals and superoxide anion radical (O2-) is even higher than its parent HB, while the ability to generate singlet oxygen (1O21O2) is not seriously reduced. In addition, nearly comparable PDT activity to A549 cells for NSHB and HB confirms that the molecular design is successful and NSHB is readily delivered into target tissues via blood circulation after intravenous injection. Furthermore, the quantum yield of 1O21O2 for NSHB is as 12.5 times as that for HB under red light (600–700 nm), which is beneficial to phototherapy to solid tumors.