Other terpenoid pigments

Solvent extraction removes chlorophyll and other pigments to give a light-colored product but increases processing costs. Furthermore, solvent extraction removes p-carotene and reduces vitamin A activity (89) (see Terpenoids Vitamins). Supercritical CO2 extraction at 30 and 70 MPa (4,350 and 10,150 psi) and 40°C removed 90 and 70% carotene and lutein, respectively, from alfalfa LPC (96). This process avoids organic solvent residues and recovers valuable by-products. 

Over 20,000 terpenoids have been identihed (1), and more are being discovered continuously. Plant terpenoids are important in both primary and secondary (speciahzed) metabolism. Their importance in primary metabolism includes physiological, metabolic, and stmctural roles such as plant hormones, chloro-plast pigments, roles in electron transport systems, and roles in the posttranslational modihcation of proteins. In secondary metabolism, the roles of plant terpenoids are incredibly diverse but are associated most often with defense and communication of sessile plants interacting with other organisms. Examples include terpenoid chemicals that form physical and chemical barriers, antibiotics, phytoalexins, repellents and antifeedants against insects and other herbivores, toxins, attractants for pollinators or fruit-dispersing animals, host/nonhost selection cues for herbivores, and mediators of plant-plant and mycorrhiza interactions (2, 3). 

Other classes of organic materials, such as alkaloids, pigments, resins, sterols, terpenes, terpenoids, and waxes, and many simple organic compounds are often present in various biomass species, but are not discussed here because they are usually present in very small amounts. The peptides present in herbaceous biomass are also not discussed here because, although the nitrogen and sulfur contents of the biomass should be assessed for certain microbiological processes, the amino acids that make up the proteins are generally not important factors in conversion processes. 

More than 55,000 terpenes have been isolated, and this number has almost doubled each decade [9, 10]. The diverse functional roles of many terpenoids have been characterized. Eucalyptus, conifer wood, balm trees, cinnamon, cloves, citms fruits, coriander, ginger, lavender, lemongrass, lilies, carnation, caraway, peppermint species, roses, rosemary, sage, thyme, violet, and many other plants or parts of those (stems, leaves, blossoms, roots, rhizomes, fruits, seed) are well known to smell pleasantly, to taste spicy, or to exhibit specific pharmacological activities which chiefly are attributed to the presence of terpenes. Also, terpenes have shown to be useful as hormones (gibbereUins), photosynthetic pigments (phytol, carotenoids). 

Terpenoids, which include in particular tetraterpenoid and some other pigments derived from tetraterpenes, known as carotenoids, monoterpenic pigments iridoids and certain other coloured compounds. 

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