Abstract
In the present study, protohypericin was synthesised in order to compare
its intrinsic photocytotoxicity with that of hypericin. The experimental work
was performed in specific filtered light conditions that prevented both an
unintended photoconversion of protohypericin and photosensitization of the
cells. Assessing the photocytotoxicity as a function of irradiation time,
it was found that the photocytotoxicity of both compounds converged after
a long irradiation time (i.e., 15 min), while the difference between
the photocytotoxicities was maximal after a short irradiation time (i.e.,
1 min). Since this could not be accounted for by a redistribution of
protohypericin during irradiation, and the different irradiation times corresponded
to different degrees of photoconversion of protohypericin into hypericin,
the results clearly suggest that protohypericin exhibits intrinsically a dramatically
lower photoactivity as compared to hypericin.
Key words
Protohypericin - hypericin -
Hypericum
- Clusiaceae - photocytotoxicity - photosensitizer
