Photoreduction of Protochlorophyll and Its Derivatives

Abstract

Abstract—Photoreduction of protochlorophyll and a series of its derivatives (with gradual simplification of the structure) was studied in ascorbic acid‐propanol‐pyridine mixtures. Additions were introduced into the solutions to suppress some side processes. Conditions were found for the photoreduction of pigment on the 7,8‐linkage, with the formation of corresponding chlorins. Chlorin yields depended on the nature of the metal in the centre of the pigment molecule. The yield of chlorophyll upon photoreduction of protochlorophyll was 30 per cent, and the yields of Zn‐derivatives of protochphyll was about 35–80 per cent. Photochemically prepared chlorins were isolated by chromatography. Some differences were discovered between their electronic, infrared, and nuclear magnetic resonance spectra and those of natural chlorins. These differences result from chlorins with a cis arrangement of hydrogen atoms on the 7,8‐linkage being selectively formed upon photoreduction, while natural chlorins have the trans arrangement. The mechanism of the photoreduction reaction is discussed.

Phorbiplatin, a Highly Potent Pt(IV) Antitumor Prodrug That Can Be Controllably Activated by Red Light

“…Given the observations that the photoreduction process of phorbiplatin is much more efficient in the presence of ascorbate (Figures S21 and S22) and that ascorbate is able to reduce PPA analogs to its reduced forms including p radical anion under irradiation through PET, [46][47][48][49][50] we hypothesized that ascorbate might first reduce the PPA moiety within phorbiplatin, and then the reduced PPA further reduces the Pt(IV) center. To corroborate this hypothesis, we first investigated the photo-induced reduction of PPA in the presence of ascorbic acid.…”

Factors in Chloroplast Differentiation

“…At the transformation of protochlorophyll(ide) to chlorophyll(ide) a the pigment is reduced (two hydrogen atoms are added per molecule). Protochlorophyll(ide) dissolved in an organic solvent is not transformed into chlorophyll(ide) a by light, except under special conditions (Suboch et al 1974). From certain plants like bean and barley, it is, however, possible to extract with aqueous buffer a protochlorphyll(ide)-protein complex (protochlorophyll holochrome, Smith 1952) which is transformed by light to a chlorophyll(ide }-protein complex.…”

Photoreduction of tetraphenylporphyrins by amines in the visible. Photochemical syntheses of reduced tetraphenylporphyrins and the mechanism of photoreduction

“…4 Similar results have been reported on the photoreduction of Zn porphine,5 and of protochlorophyll and some of its derivatives with ascorbic acid. 6 In these studies it was indicated that addition of amines to the reaction mixture causes a catalytic effect on the reaction rate.…”