9.
Abstract –The products of chlorophyll allomerization in methanol were isolated and analyzed by open column sucrose chromatography, liquid chromatography mass spectrometry (LCMS) and DAD-HPLC (diode-array high-performance liquid chromatography). Four main bands were found with molecular ions of (a) 908, (b) 938, (c) 938 and (d) 938, consistent with the structures (a) 13
2-hydroxy-chlorophyll a (II), (b) and (c) Mg(II)-3
1,3
2-didehydro-15
1-hydroxy-15
1-methoxy-rhodochlorin-15 acetic acid δ-lactone 15
2-methyl 17
3-phytyl ester and its epimer (III) and (d) Mg(II)-3
1,3
2-didehydro-rhodochlorin-15-glyoxylic acid 13
1,15
2-dimethyl 17
3-phytyl ester (IV), evidence enhanced by UV/visible spectroscopy, chromatographic coelutions and chemometrics. Chlorophyll a was degraded both in the dark and light, under O
2 and N
2. DAD-HPLC of the resultant degradation mixtures were analyzed using the chemometric heuristic-evolving latent projection method for resolution. Ultraviolet/visible spectra of II and III are reproducibly extracted from the mixtures after a short degradation time, whereas III and IV are the dominant compounds after longer degradation times. Changes in relative elution order of IV using open column chromatography and reverse-phase HPLC are established. A possible allomerization pathway is proposed.
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