Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

3-19-1997

Journal or Book Title

Journal of the American Chemical Society

Volume

119

Issue

11

First Page

2763

Last Page

2764

DOI

10.1021/ja962923t

Abstract

Hypocrellin and its analog, hypericin (Figure 1), are naturally occurring quinones that have been used for centuries as folk medicines in the orient and the occident and that have attracted much interest because of their light-induced toxicity toward the human immunodeficiency virus (HIV).1The structural similarities of hypocrellin and hypericin would seem to suggest that hypocrellin exhibits excited-state and antiviral behavior similar to that of hypericin. Although they both execute excited-state proton or atom transfer2,3between the keto and enol oxygens (Figure 1), there are many important differences between them. Hypocrellin absolutely requires oxygen for antiviral activity whereas hypericin does not.3 Hypocrellin does not provide a light-induced pH drop of its surroundings under conditions in which hypericin does.4 Here we discuss two other important differences. First, whereas in hypericin the excited-state photophysics depend only negligibly on solvent,2b in hypocrellin there is a very pronounced dependence on the solvent, which is related to bulk viscosity and to polarity in primary alcohols and, perhaps, nitriles. Second, the excited-state transfer process in hypocrellin occurs on a time scale at least 10 times longer than the analogous event in hypericin.2 The elucidation of these primary photophysical processes provides a basis for understanding the different modes of activity of hypocrellin and hypericin and will be significant in the exploitation of their properties against viruses and tumors and in the design of other analogous systems.

Comments

Reprinted (adapted) with permission from Journal of the American Chemical Society 119 (1997): 2763, doi: 10.1021/ja962923t. Copyright 1997 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

Included in

Chemistry Commons

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