Color, pigments tetrapyrrole

Bile Pigments. The oxidative degradation of heme yields open-chain tetrapyrrole as a waste product in humans and other higher animals. The yellow color of the skin in jaundice victims is caused by the presence of biluubin [635-65-4] (32, R = (CH2)2COOH). 

The phycobiliproteins are accessory photosynthetic pigments aggregated in cells as phycobilisomes that are attached to the thylakoid membrane of the chloroplast. The red phycobiliproteins (phycoerythrin) and the blue phycobiliprotein (phycocy-anin) are soluble in water and can serve as natural colorants in foods, cosmetics, and pharmaceuticals. Chemically, the phycobiliproteins are built from chro-mophores — bilins — that are open-chain tetrapyrroles covalently linked via thio-ether bonds to an apoprotein. ... 

Nuclear magnetic resonance spectroscopy (NMRS) has also been used to detect adulteration in olive oil (Mannina et al., 2003). To improve the color of virgin olive oil, chlorophyll molecules are sometimes added. This addition may be detected by NMRS because chlorophyll and pheophytin, the regular tetrapyrrole pigments of olive oil, give a different spectrum. 

A a,c,d B a,b,c,d C a. The bilin pigments are linear tetrapyrroles, structurally related to bilirubin and biliverdin, the pigments found in bruises and largely responsible for the yellow color of jaundiced skin. See pages 688 and 689 in the text to compare these structures. It may be easier to remember the terms phycoerythrobilin and phycocyanobilin if you know that in Greek erythro means red and cyano means blue. ... 

Tetrapyrroles. Name for natural products, most of which are colored, containing four pyrrole units in a cyclic or linear basic skeleton, e.g., chlorins, cor-rins, corphins, bile pigments, isobacteriochlorins, phycobilins, porphyrins, porphyiinogens. For nomenclature of the T., see L/r.. ... 

Other examples of linear tetrapyrrolic pigments have been encountered in the marine environment. Phycocyanobilin is partly responsible for the blue color of the coral Heliopora coerulea (Cnidaria Hexacorallia see Chapter 20), and Opisthobranch mollusks of the Aplysia genus emit a purplish ink, aplysioviolin, a methyl monoester of phycoerythrobilin whose structure was recently revised (Prota, 1980 Appleton, Babcock, and Copp, 2001 Jongaramruong et al, 2002). The red algae often constitute the majority of the food of these herbivorous mollusks, and we have here a first example (among many others) of a food web. ... 

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