Chlorophyll fluorescence

Detection and result The chromatogram was dried in a stream of warm air. Blood-red fluorescent chlorophyll zones were visible in the region of the solvent front. In the case of Orthosiphon leaf extract there was an intense pale blue fluorescent sinensetin zone OiRf 90-95) immediately below this, followed by a series of usually weaker blue fluorescent zones extending right down to the start zone (Fig. lA). 

RCC is very unstable and rapidly reduced to a primary fluorescent chlorophyll catabolite (pFCC) by red chlorophyll catabolite reductase (RCCR). In subsequent steps pFcc is converted to different fluorescent chlorophyll catabolites (FCCs). These chemically rather labile compounds are further converted into colorless nonfluorescing chlorophyll catabolites (NCCs) by a nonenzymatic deconjugation of the four... 

Miihlecker, W. et ah. Tracking down chlorophyll breakdown in plants Elucidation of the constitution of a fluorescent chlorophyll catabohte, Angew. Chem. Int. Ed. Engl, 36, 401, 1997. 

Oberhuber, M. and Krautler, B., Breakdown of chlorophyll electrochemical bilin reduction provides synthetic access to fluorescent chlorophyll catabolites, Chembio-chem, 3, 104, 2002. 

FIGURE 4.1.1 Possible chlorophyll degradation pathways in plant tissues or in processed foods. Pheophorbide a monooxygenase is specific for pheophorbide a. RCC = red chlorophyll catabolite. FCC = fluorescent chlorophyll catabolite. NCC = non-fluorescent chlorophyll catabolite. 

Despite the difficulties in extracting and identifying colorless catabolic products that are extremely labile and detectable only in trace amounts, several of the mysteries of chlorophyll catabolism have been revealed and about 14 non-fluorescent chlorophyll catabolytes (NCCs) from higher plants, mainly in senescent leaves, have been detected and analyzed structurally. Among them, NCCs from rapeseed (Bms-sica napus) from Liquidambar styraciflua, from Cercidiphyllum japonicum, five NCCs from degreened leaves of spinach Spinacia oleracea) and, more recently, two NCCs from tobacco Nicotiana rusticd) and five NCCs from Arabidopsis thaliana have been identified. 

Berghold, J. et al., Chlorophyll breakdown in tobacco on the structure of two non-fluorescent chlorophyll catabolites, Chemistry Biodiversity, 1, 657, 2004. 

M. Adachi, K. Nakabayashi, R. Azuma, H. Kurata, Y.Takahashi and K. Shimokawa, The ethylene-induced chlorophyll catabolism of radish (Raphanus sativus L.) cotyledons production of colorless fluorescence chlorophyll catabohte (FCC) in vitro. J. Japan Soc. Hort. Sci. 68 (1999) 1139-1145. 

Fluorescent Chlorophyll Catabolites from Enzymatic Reduction... 

Transformation of Fluorescent Chlorophyll Catabolites to Non-fluorescent Colourless Chlorophyll Catabolites. 22... 

Scheme 1. Overview of chlorophyll breakdown in senescent higher plants (2). The chlorophylls (Chi a, la (R = CH3) or Chi b, lb (R = CH=0) are degraded via pheophorbide a (Pheo a, 5a), red chlorophyll catabolite (RCC, 11), the primary fluorescent chlorophyll catabolites (pFCCs, 10) to non-fluorescent chlorophyll catabolites (NCCs), such as //v-NCC-1 (2, also called RP-14)...

Discovery and Structure Analysis of Fluorescent Chlorophyll Catabolites... 

Scheme 5. In higher plants pheophoibide a (5a) is degraded to the primary fluorescent chlorophyll catabolite (pFCC, 10) and to its C(l)-epimer epi-10 (epi-pFCC)...

The red chlorophyll catabolite RCC (11) is bound strongly to PaO and inhibits it. In an in vitro assay, the soluble reductase from oilseed rape converted 11 to the primary fluorescent chlorophyll catabolite pFCC (10, 31,32-didchydro-1,4,5,10,17,18,20-(22//)-octahydro-132-(mcthoxy-carbonyl)-4,5-dioxo-4,5-seco-phytoporphyrin) (62, 83). The reductase, which was named red chlorophyll catabolite reductase (RCC-reductase) (68, 80, 83), introduced the chiral center C(l) via a stereo-selective reduction step. However, early studies with oilseed rape and sweet pepper indicated a remarkable stereo-dichotomy of the respective reductases (see above) (67, 68, 69). Screening of a variety of plant species for their type of primary FCC revealed the broad existence of two classes of the RCC-reductases , whose stereo-selectivity was species specific (84). At present, the (absolute or relative) configuration at C(l) in the two pFCCs (10 and epi-10) is not yet established (2). Indeed, the existence of the two epimeric pFCCs (10 and epi-10) (see Scheme 6) indicated the absolute configuration at the newly generated chiral center to have no apparent functional relevance (67, 68, 69). 

The constitution of f/v-NCC-1 (2, 31,32,82-trihydroxy-l,4,5,10,15,20-(22//,24//)-octahydro-132-(methoxycarbonyl)-4,5-dioxo-4,5-seco-phyto-porphyrinate (see Scheme 2) gave first clues on the basic transformations involving the Chl-chromophore (1, 2, 4, 10). When, in addition, the structure of the fluorescent chlorophyll catabolite pFCC (10) was revealed, an isomerization of the chromophore of the FCCs into that of... 

The fluorescent chlorophyll catabolites, such as pFCC (10), were observed not to accumulate during chlorophyll breakdown in senescent leaves (24). The indicated further transformation of the FCC chro-mophore to those of non-fluorescent chlorophyll catabolites (NCCs) was suggested to possibly be the result of a non-enzymic isomerization (56, 62). In analogy to the results of studies on the tautomerization chemistry of a range of hydro-porphinoids (91), the isomerization of the chromo-phore of FCCs into that of NCCs was judged to be rather favorable, thermodynamically. The complete de-conjugation of the four pyrrolic units, characteristic of the tetrapyrrolic NCCs, thus may occur in the course of natural chlorophyll breakdown under rather mild and, possibly, even without catalysis by (an) enzyme(s) (56). 

Scheme 12. Constitution of non-fluorescent chlorophyll catabolites (NCCs) from higher...

Muhlecker W, Ongania KH, Krautler B, Matile P, Hortensteiner S (1997) Tracking Down Chlorophyll Breakdown in Plants Elucidation of the Constitution of a Fluorescent Chlorophyll Catabolite. Angew Chem Int Ed 36 401... 

Miihlecker W, Krautler B, Moser D, Matile P, Hortensteiner S (2000) Breakdown of Chlorophyll A Fluorescent Chlorophyll Catabolite from Sweet Pepper (Capsicum annuum). Helv Chim Acta 83 278... 

Oberhuber M, Krautler B (2002) Breakdown of Chlorophyll Electrochemical Bilin Reduction Provides Synthetic Access to Fluorescent Chlorophyll Catabolites. Chem BioChem 3 104... 

Hg. 23A Boldo folium. The alkaloid extract (1) is characterized in UV-.365iim by the two violet fluorescent zones In the R( range of the boldine test Tl, as well as varioins red-orange fluorescent chlorophyll zones in the upper R, range. 

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