Abstract

Hypericin (Figure 1) is a naturally occurring polycyclic quinone that has received recent notoriety for its antiviral capacity-in particular its ability to deactivate the human immunodeficiency virus (HIV) [1]. The antiviral activity of hypericin requires light [2]. Hypericin is also very closely related, both structurally and spectrally, to the chromophore of the photoreceptor complexes of the protozoan ciliates [3]. Optical excitation of hypericin produces both singlet oxygen [4] and a pH decrease [5] and gives rise to transient species of picosecond duration. The following observations indicate that excited-state, intramolecular proton transfer occurs in hypericin.

© 1994 Optical Society of America