The paper presents the results of experiments to determine the influence of
selected physico-chemical factors – oxygen, visible light and temperature – on
the decomposition of (1) chlorophylls a, b and c, chlorophyll a derivatives
and β-carotene in acetone solution, and (2) chlorophyll a and β-carotene in
axenic cultures of the blue-green algae Anabaena variabilis. The results indicate
that both in acetone extracts and in blue-green algae cultures these pigments
were most sensitive to light and oxygen; temperatures of up to 25◦C had
no marked influence on these compounds. Under anoxia in acetone solution,
the stability towards light decreased in the order chlorophyll a, chlorophyll b,
chlorophylls c. Chlorophyll a, moreover, was less stable than its derivatives
– phaeophorbides, phaeophytins, pyrophaeophytins and steryl chlorins – but more
stable than β-carotene, in the last case also in the blue-green algae cultures.
Decomposition of all the pigments proceeded mainly via the breakdown of the
porphyrin macrocycle, since the decomposition products were not detected in the
VIS range. On the basis of these experiments one can state that while light and
oxygen may have a decisive direct influence on the distribution of chlorophylls and
β-carotene in sediments, in the natural environment, temperatures of up to 25◦ C
may have very little immediate effect.
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