Photostability of bacteriochlorophyll a and derivatives: potential sensitizers for photodynamic tumor therapy.
The photostabilities of bacteriochlorophyll a and several of its derivatives, which are of interest as potential sensitizers in photodynamic tumor therapy, were investigated. The pigments were irradiated with light >630 nm in organic solvents (acetone, tetrahydrofuran, pyridine, methanol, ethanol, n-propanol, 2-propanol and toluene) and in aqueous detergent solutions (cetyl-trimethyl-ammonium bromide [CTAB], lauryldimethyl-aminoxide [LDAO] or sodium dodecyl-sulfate [SDS] and Triton X-100 [TX100]). Their stabilities in these different solvents were determined in the presence and absence of an external sensitizer (pyromethyl-pheophorbide a), oxygen, sodium ascorbate and inert gas (Ar) or vacuum. The photodegradation products of bacteriochlorophyll a in acetone solution were isolated, purified by HPLC and analyzed by their absorption spectra and mass spectroscopy. Besides the well-known dehydrogenation products, such as [3-acetyl]-chlorophyll a, which were obtained as by-products, the major products had low absorption in the visible-near infrared spectral range. The spectral signature of the major component of these products was characteristic of linear open-chain tetrapyrroles, but they lacked the characteristic protonation-deprotonation behavior and reactivity of bilins with Zn(++).
Limantara
Leenawaty
L
Department Biologie I, Bereich Botanik, Ludwig Maximilians Universität München, Germany.
Koehler
Peter
P
Wilhelm
Brigitte
B
Porra
Robert J
RJ
Scheer
Hugo
H
D001429:Bacteriochlorophylls / Q000528:radiation effects*; D008027:Light; D009369:Neoplasms / Q000628:therapy; D010777:Photochemistry; D010778:Photochemotherapy / Q000379:methods; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000528:radiation effects
D001429:Bacteriochlorophylls; D017319:Photosensitizing Agents