3. Plant pigments
Pigments - chemical compounds which reflect only certain
wavelengths of visible light
-appear "colorful“ (flowers, corals, animal skin contain pigments which give
them their colors)
-their reflection of light is the ability of pigments to absorb certain
wavelengths
Chlorophylls, carotenoids, anthocyanins
Plant pigments related to the light spectrum
4.
5. Chromatography
(from Greek χρῶμα chroma "color" and γράφειν graphein "to write")
= color separation
Paper chromatography
-> Pigments from plant tissues are separated
based on those chemical properties
(i.e., molecular size/solubility/polarity)
pigments
6. Photosynthetic Pigments - Chlorophylls
In most plants, two types are present:
Chlorophyll A and Chlorophyll B
Both types act as electron-transporters
in photosynthesis and give plants
their green color
Both are polar
7. Carotenoids and associated
xanthophylls:
- act as accessory pigments and trap
sunlight energy for photosynthesis.
- act as photo-protective agents,
protecting the plants from the effects
of excess energy build up that causes
the formation of toxins in plants
- anti-oxidants, precursor for vitamin
A formation, good for vision
maintenance
Carotenoids
9. Anthocyanin
Anthocyanins:
- generate colors in red to blue range for
plants
- protect plants against UV light and
damage caused by UV
- attract insects for pollination and provide
protection against predators
- positive effects against cancer, aging and
neurological diseases, inflammation,
diabetes, bacterial infection
- bacterial infections
10. Anthocyanins
- phenolic pigments
- are polar
- water soluble
Anthocyanins
11. Chromatography
(from Greek χρῶμα chroma "color" and γράφειν graphein "to write")
= color separation
Paper chromatography
-> Pigments from plant tissues are separated
based on those chemical properties
(i.e., molecular size/solubility/polarity)
pigments
12. Retention factor (Rf) values
of pigments
Rf =
𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒑𝒊𝒈𝒎𝒆𝒏𝒕 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅
𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒔𝒐𝒍𝒗𝒆𝒏𝒕 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅
=
𝒂
𝒃
Chromatography Background
a
b
13. Rf values of pigments
Carotene - 0.98; orange
Pheophytin - 0.81; olive green
Chlorophyll a - 0.59; blue-green
Chlorophyll b - 0.42; yellow-green
Anthocyanins - between 0.32 and 0.62; red, pink, purple
and blue colors
Xanthophyll 1 - 0.28, yellow
Xanthophyll 2 - 0.15, yellow
www.bioquest.org/summer2008/projectfiles/leafchromat
ography.doc
Chromatography Background
14. Chromatography Background
It is possible to measure the solubility of a pigment in a
solvent by measuring how far the pigment travels vs. how far
the solvent travels
This is called retention factor, or Rf value
Rf values are characteristic of specific pigments and can be
used to identify them
The higher the Rf value, the less polar the compound.
Thus, a compound not migrating from the origin would have
an Rf of 0, a compound migrating with the solvent front would
have an Rf of 1.0, and a compound migrating half as far as the
solvent front would have an Rf of 0.5.
