FIGURE 6.4 Benzopyran derivatives. The R groups are commonly H, OH, and CH3.

also provide color to fungi and lichens (yellow, orange, or browns), sea urchin (brilliant red, purple, or blues), and some insects (coccid and aphids). Some fungi produce large quantities of quinones, as metabolic by-products, and different colorations are observed such as yellow, red, or brown. The fungus Polyporus rutilans accumulates up to 23% dry weight (d.w.) of polyporic acid, a terpenyl quinone of bronze color, and Helminthosporium gramineum produces up to 20% d.w. of quino-nes (islandicin, crisophanol, emodin). In addition, some bacteria produce good quantities of quinones; Streptomyces coelicor accumulates up to 15% d.w. Moreover, salts of quinones show purple, blue, or green color.1,7,13

Some quinones have shown importance at the industrial level: alizarin, xantho-purpurin, rubiadin, and purpurin from Rubia tinctoreum L.; the 3-hydroxy-2-methyl-anthraquinone, methyl-ether of rubiadin, and lucidin from the peel of Coprosoma acerosa A.; and the most important quinones for the food industry, the anthraquino-nes carminic acid (from the insect Dactylopuis coccus) and carmesic acid (from the insect Laccifer lacca Kerr).13

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