Light absorption carotenoids

The maximum absorption wavelengths in different solvents of many carotenoids can be found in the literature, and the % III/II values are also available for some carotenoids. It is common to find variations of 1 to 3 nm in for the same carotenoid in the same solvent cited in different publications. No identification based simply on the matching of recorded UV-Vis spectra with tabulated data can be done without considering the relationships of structures and the factors influencing light absorption. The principal factors that influence carotenoid UV-Vis absorption spectra are discussed below. 

In both treatments, the in vivo light absorption characteristics were invariable over the day (data not shown). Maximum values in the chlorophyll-specific absorption coefficient were observed near 675 nm (Chi a), 470 nm (carotenoids) and 430 nm (Chi a) (Fig. 4). The absorption cross section was 0.057 m2 mg Chi a 1 under iron limitation and... 

New Structures and Stereochemistry.—New Carotenoid Structures. A mutant strain of Rhizobium lupini contains a new nor-carotenoid, 2, 3 -trans-dihydroxy-2-nor-/3,/3-carotene-3,4-dione (1)." The wild-type R. lupini, when cultured in the presence of the cyclization inhibitors nicotine or CPTA, produced three new monocyclic carotenoids, 2,3-h-ans-dihydroxy-/3,-caroten-4-one (2), 3-hydroxy-/3,(/ -caroten-4-one (3), and p,tf/-carotene-2,3-trans-dio (4)," which were characterized by m.s. and n.m.r. The light absorption and mass spectra of a carotenoid from Rhodopseudomonas capsulata allowed its identification" as demethylspheroidenone [l-hydroxy-3,4-didehydro-l,2,7, 8 -tetrahydro- /f,(/f-caroten-2-one (5)]. 

New Structures.—Monocyclic Carotenoids. A poly-cw-isomer of y-carotene carotene (1)], isolated from Tangerine tomato fruits, may be similar to pro-y-carotene from Pyracantha angustifolia. Two compounds from the Delta tomato mutant have been identified as l, 2 -epoxy-r,2 -dihydro-j8, /f-carotene (2) and l, 2 -epoxy-l, 2 -dihydro-e,j/ -carotene (3), epoxides of y- and 5-carotene respectively. Evidence has been presented for the structure (4) (r-methoxy-3, 4 -didehydro-l, 2 -dihydro-jS, / -carotene) for a minor carotenoid of Rhodomicrobium vannielii. On the basis of its light absorption spectrum and chemical reactions, a minor compound from the yeast Phaffia rhodozyma has been assigned structure (5), 3-hydroxy-3, 4 -didehydro-j8, / -caroten-4-one. ... 

Electronic Absorption Spectroscopy. Extensive tables of light absorption maxima and extinction coefficients for naturally occurring carotenoids are included in the review by Davies. ... 

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