các carotenoid trong trái cây
e d i t e d by:
MICHAEL SLABAUGH
R.
Weber State College
Ogden. Utah 8440s
The Chemical Pigments of Plants
Joy Alkema and Spencer L. Seagerl
Box 2503, Weber State C o l l e g e , O g d e n , UT 84408
Each spring the predominantly drab colors of wintering plants give way to a sudden display of bright hues. The prevalent color of spring is of course green in a variety of shades.
But, in addition, splashes of yellow, red, pink, and magenta are seen in the foliage of some plants. As time passes, nature 's chromatic display continues. Flowers bloom and exhibit practically every color and shade that can he imagined. Fruits and berries rinen. and in so doing thev undereo dramatic color
. .
- . changes from the green characteristic of their unripe condition. During the autumn. much of the ereen foliaee changes color to become some shade of yellow, orange, red, scarlet, magenta, or purple, which finally is replaced by brown as winter approaches.
Interestinelv. most of these colors and color chances result from the production, interaction, and breakdown of three classes of substances: porphyrins, carotenoids, and flavonoids.
In Table 1 the types of compoundsincluded in each of these three classes are aiven toaether with the colors they produce in plants. The coyors depend in some instances up& factors such as pH or upon chemical interactions.
u
PORPH IN
-
Porphyrins
Porphyrins are derivatives of porphin, which consists of four nitrogen-containing heterocyclic rings linked by four methene bridges in an alternating double-bond ring system. Many porphyrins have intense colors; the one of interest in this discussion is the dark green plant pigment chlorophyll. Plants contain both chlorophyll a and chlorophyll b, which have slightly different structures, but chlorophyll a predominates. o and a In Fieure 1 the structures of .o r ~ h i n chloro~hvll are shown. It is apparent that chlorophyll a has the characteristic
worohin
MICHAEL SLABAUGH
R.
Weber State College
Ogden. Utah 8440s
The Chemical Pigments of Plants
Joy Alkema and Spencer L. Seagerl
Box 2503, Weber State C o l l e g e , O g d e n , UT 84408
Each spring the predominantly drab colors of wintering plants give way to a sudden display of bright hues. The prevalent color of spring is of course green in a variety of shades.
But, in addition, splashes of yellow, red, pink, and magenta are seen in the foliage of some plants. As time passes, nature 's chromatic display continues. Flowers bloom and exhibit practically every color and shade that can he imagined. Fruits and berries rinen. and in so doing thev undereo dramatic color
. .
- . changes from the green characteristic of their unripe condition. During the autumn. much of the ereen foliaee changes color to become some shade of yellow, orange, red, scarlet, magenta, or purple, which finally is replaced by brown as winter approaches.
Interestinelv. most of these colors and color chances result from the production, interaction, and breakdown of three classes of substances: porphyrins, carotenoids, and flavonoids.
In Table 1 the types of compoundsincluded in each of these three classes are aiven toaether with the colors they produce in plants. The coyors depend in some instances up& factors such as pH or upon chemical interactions.
u
PORPH IN
-
Porphyrins
Porphyrins are derivatives of porphin, which consists of four nitrogen-containing heterocyclic rings linked by four methene bridges in an alternating double-bond ring system. Many porphyrins have intense colors; the one of interest in this discussion is the dark green plant pigment chlorophyll. Plants contain both chlorophyll a and chlorophyll b, which have slightly different structures, but chlorophyll a predominates. o and a In Fieure 1 the structures of .o r ~ h i n chloro~hvll are shown. It is apparent that chlorophyll a has the characteristic
worohin
Cited: (1) Hss8.H. B., Chrmtfch,525 (Sept. 1977). (3) Winkelman, C., u r l i ~ u l i v i e46.39 (1968). (6) Asen. S.. Stewart. R. N.,and N0rrir.K. H.,Phhyturhem..14,9677 (19751. W,"Chemiatryand Biochemistry of Plant Pigments,"U.S. ed., Academic Press, New York, 1965. Presa, New York, 1970. (9) Harliurne, J. B., "Comparative Biochemistry of the Flrvonaids," U S . ed., Academic Presl, New York, 1967.