Concerning the Hypericin Sensitized Photooxidation of Bilirubin IXα

Abstract

In aerated protic solvents like ethanol or 80% aqueous ethanol, bilirubin IX was found to undergo a hypericin sensitized oxidative photodestruction. By means of quenching experiments it was deduced that this was mainly due to the sensitized production of singlet oxygen, but also to some extent to the sensitized formation of superoxide radicals which then react with bilirubin IX. In absence of oxygen, a photochemically induced disproportionation reaction of hypericin may lead to the oxidative degradation of bilirubin IX. Upon selective binding of the two pigments to human serum albumin the photosensitized bilirubin IX destruction was found to be compeletely retarded. Accordingly, the presence of bilirubin IX within the realm of hypericin assisted photodynamic therapy should have no adverse effects, and neonatal jaundice phototherapy would not bene®t from an administration of hypericin.

Concerning the Absorption and Photochemical Properties of an ω-4-Dimethylaminobenzal Hypericin Derivative

“…This is quite large compared with the only 5 nm of (3À) 1 [9]. However, hypericin sensitized photooxidation of bilirubin, which has been shown to provide a sensitive measure of the generation of sensitized active oxygen species ± in peculiar of singlet oxygen and superoxide radicals [10] ± revealed that (3À) 12 did not produce the sensitized singlet oxygen and superoxide species thought to be the most active agents in hypericin photodynamic therapy [1] (Fig. At this point the use of 12 as a photodynamic agent seemed even more promising since a low uorescence quantum yield could point to an enhanced intersystem crossing, which would be necessary to sensitize active oxygen species.…”

“…1 H and 13 C NMR, UV/ Vis,¯uorescence, and mass spectra were recorded using Bruker DRX 500 and DPX 200, Hewlett Packard 8453 UV/ Vis, Hitachi 4010F, and Hewlett Packard 59987 quadrupole instruments. [10]. The¯uorescence quantum yield was determined as described previously [9].…”

Cationic Hypericin Derivatives as Novel Agents with Photobactericidal Activity: Synthesis and Photodynamic Inactivation of Propionibacterium acnes

“…The production of singlet oxygen ⁄ oxidizing species by 11-14 was monitored by bilirubin-IXa-degradation according to Ref. (43). The long-wavelength ''hypericinic'' absorption band intensities of 1 and the four compounds were made equal by adjusting concentrations to provide comparable light absorptions for all compounds investigated.…”

Toward Hypericin-derived Potential Photodynamic Therapy Agents¶

“…Photodestruction of bilirubin IX␣. Following Hagenbuchner and Falk (11) irradiation of the thermostated (20.0 Ϯ 0.1ЊC) aerated solutions of sodium bilirubinate, together with 1 Ϫ or 2 Ϫ in 80% aqueous ethanol contained in SiO 2 cuvettes (d ϭ 1 cm), were performed by means of a 300 W tungsten lamp and a cut-off filter blocking light below 570 nm and measuring the UV-Vis spectra at intervals of 20 s (Fig. 1).…”

“…To test for an enhanced photochemical singlet oxygen/ superoxide radical formation of 2 in comparison to 1 we used the recently introduced photosensitized bilirubin IX␣ destruction method (11). As shown in Fig.…”