PHOTOCHEMICAL RING‐OPENING IN <i>meso‐</i>CHLORINATED CHLOROPHYLLS

Struck, A.; Cmiel, Edmund; Schneider, Siegfried; Scheer, Hugo

doi:10.1111/j.1751-1097.1990.tb01706.x

Cited by 26 publications

(7 citation statements)

References 33 publications

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“…Such a screening cannot replace more thorough investigations using direct techniques to detect and quantitate the different ROS as well as the excited states and the degradation products of the sensitizers, but it promptly provides valuable and relevant preliminary information. The system may also be useful for an analysis of the BChl degradation products, about which relatively little information exists (23,(32)(33)(34)(35), in contrast to those from Chl (reviewed by Gossauer and Engel [36] and Kräutler and Matile [37]) and carotenoids (reviewed by Biswal [38] and Topalov and Kishi [39]). The rather unexpected speed and complexity of carotenoid reactions already attest to its potential (16).…”

Section: Discussionmentioning

confidence: 99%

Photodynamics of the Bacteriochlorophyll–Carotenoid System. 2. Influence of Central Metal, Solvent and β-Carotene on Photobleaching of Bacteriochlorophyll Derivatives¶

Fiedor¹,

Fiedor²,

Kammhuber³

et al. 2002

Photochem Photobiol

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Bacteriochlorophyll (BChl) derivatives (with central Mg replaced by metal "M") ([M]-BChl with M = 2H, Mg, Zn, Pd, Cu) have been investigated for their photodynamic capacity and stability toward photodegradation in organic solvents and aqueous micellar solution. A protocol has been developed for screening new sensitizers. BChl and [Zn]-BChl are efficient sensitizers, but they are also quickly degraded by the reactive oxygen species (ROS) produced by autosensitization, as well as by hetero-sensitization with 17(4)-methyl-13(2)-demethoxycarbonyl-pheophorbide a (MPP). Photostable [Cu]-BChl is a poor sensitizer, whereas [Pd]-BChl and bacteriopheophytin a are not only very efficient sensitizers but are also very stable toward ROS. beta-Carotene is no efficient physical quencher of ROS in the system; rather, it acts as a photochemical quencher that competes with [M]-BChl and undergoes photooxygenation at high rates. Photolability seems to depend on the pigment oxidation potential and, in parallel, on the presence of central metals preferring coordination numbers higher than 4, whereas photodynamic capacity depends on long excited state life-times of the pigment or efficient intersystem crossing (or both).

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Section: Discussionmentioning

confidence: 99%

Photodynamics of the Bacteriochlorophyll–Carotenoid System. 2. Influence of Central Metal, Solvent and β-Carotene on Photobleaching of Bacteriochlorophyll Derivatives¶

Fiedor¹,

Fiedor²,

Kammhuber³

et al. 2002

Photochem Photobiol

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“…Indeed, the light intensity of the broad‐spectrum light is significantly higher than that of normal lighting. Struck and others () demonstrated that chlorinated chlorophylls degrade into open ring tetrapyrroles which may not be detected with our HPLC methodology.…”

Section: Resultsmentioning

confidence: 77%

Contribution of Chlorophyll to Photooxidation of Soybean Oil at Specific Visible Wavelengths of Light

Bianchi

Duncan

Webster

et al. 2015

Journal of Food Science

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Photosensitizers in foods and beverages are important considerations when selecting packaging materials. Chlorophyll is found at low concentrations in many food products. The objective of this study was to determine the photosensitizing effect of chlorophyll on soybean oil (SO) using broad-spectrum light and 3 visible wavelength regions of light. SO with added chlorophyll (0, 1, or 2 μg chlorophyll added/mL SO) was exposed to 5 light conditions, using a photochemical reactor (10 °C; 4 h). Light treatments included broad-spectrum (BS; no filter; 157.6 ± 4.7 mW intensity), 430 nm (10 nm; 1.8 ± 0.7 mW), and 660 nm (10 nm; 0.332 ± 0.05 mW) wavelengths compared to a no-light control. Chlorophyll a (but not b) absorbs light in the selected visible wavelength regions. Chlorophyll degradation was evaluated. Oxidative changes in SO were assessed by peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) assay, which measures malondialdehyde (MDA). Chlorophyll was completely degraded at BS and 430 nm conditions and degraded to 36% of original concentration at 660 nm wavelength. PV and MDA concentration significantly increased with chlorophyll addition (1 μg/mL) at BS and 430 nm wavelengths compared to no-light control. Lower light intensity at 660 nm initiated oxidation reactions as measured by PV, but not significantly. There were differences in PV (BS, 430 nm) and TBARS (BS) between the no-light and light-exposed SO without chlorophyll added. There was very little effect at 450 nm. This study suggests that broad-spectrum light and at least light wavelengths at or near 430 nm and 660 nm excite chlorophyll, resulting in initiation of oxidation reactions. Packaging material selection for foods and beverages should consider blocking excitation wavelengths of photosensitizing molecules, including chlorophyll, to protect product quality.

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“…The photooxidation of magnesium complexes corresponding to 4a and 4b has been investigated recently by Struck et al (1990). On the basis of spectroscopic data, structures related to 2 and 3 have been anticipated by these authors for the reaction products which have not however been unequivocally characterized.…”

Section: Resultsmentioning

confidence: 99%

Formation of Oxoniachlorins on Photooxidation of 20‐trifluoroacetoxy‐ and 20‐chloro‐chlorophyll Derivatives*

Iturraspe

Gossauer

1991

Photochem & Photobiology

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Zinc complexes of both 20‐trifiuoroacetoxy‐ and 20‐chloro‐pheophorbide‐a methyl ester yield the same isolable 20‐oxonia‐pheophorbide (2b) on irradiation with visible light in methylene chloride for 90 and 10 min, respectively. In the case of the 20‐chloro derivative, the yield amounts to40–50% along with 30% of starting material. Zinc complexes of 20‐trifluoroacetyl‐ and 20‐chloro‐pyropheophorbide‐a methyl ester behave likewise. In aqueous solution, the expected dihydro‐biliverdin derivatives 2 are obtained among other products, some of them display a strong red fluorescence. In the presence of nucleophiles the oxoniachlorin macrocycle is readily cleaved, yielding the corresponding linear tetrapyrroles. Particularly, reaction with cyanide ions leads to biline derivatives, which could serve as intermediates for the synthesis of natural occurring luciferins from bioluminescent plankton. The possible role of some of the above mentioned reactions in connection with chlorophyll catabolism is discussed.

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PHOTOCHEMICAL RING‐OPENING IN meso‐CHLORINATED CHLOROPHYLLS

Abstract: Abstract-Irradiation of 20-chloro-chlorophylls of the a-type with visible light produces long-wavelength shifted photoproducts, which transform in the dark to linear tetrapyrroles (bile pigments). The possible significance for chlorophyll degradation is discussed.

Cited by 26 publications

References 33 publications

Photodynamics of the Bacteriochlorophyll–Carotenoid System. 2. Influence of Central Metal, Solvent and β-Carotene on Photobleaching of Bacteriochlorophyll Derivatives¶

Photodynamics of the Bacteriochlorophyll–Carotenoid System. 2. Influence of Central Metal, Solvent and β-Carotene on Photobleaching of Bacteriochlorophyll Derivatives¶

Contribution of Chlorophyll to Photooxidation of Soybean Oil at Specific Visible Wavelengths of Light

Formation of Oxoniachlorins on Photooxidation of 20‐trifluoroacetoxy‐ and 20‐chloro‐chlorophyll Derivatives*

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