Phylloxanthobilins are Abundant Linear Tetrapyrroles from Chlorophyll Breakdown with Activities Against Cancer Cells

Linear tetrapyrroles, called phyllobilins, are obtained as major catabolites upon chlorophyll degradation. Primarily, colorless phylloleucobilins featuring four deconjugated pyrrole units were identified. Their yellow counterparts, phylloxanthobilins, were discovered more recently. Although the two...

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Bibliographic Details
Published in:European journal of organic chemistry 2020-08, Vol.2020 (29), p.4499-4509
Main Authors: Karg, Cornelia A., Wang, Pengyu, Kluibenschedl, Florian, Müller, Thomas, Allmendinger, Lars, Vollmar, Angelika M., Moser, Simone
Format: Article
Language:English
Subjects:
Biological activity
Cancer
Cell cycle
Cell death
Chlorophyll
Esterification
Esters
Mass spectrometry
Natural products
Phylloxanthobilins
Tetrapyrroles
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Summary:Linear tetrapyrroles, called phyllobilins, are obtained as major catabolites upon chlorophyll degradation. Primarily, colorless phylloleucobilins featuring four deconjugated pyrrole units were identified. Their yellow counterparts, phylloxanthobilins, were discovered more recently. Although the two catabolites differ only by one double bond, physicochemical properties are very distinct. Moreover, the presence of the double bond seems to enhance physiologically relevant bioactivities: in contrast to phylloleucobilin, we identified a potent anti‐proliferative activity for a phylloxanthobilin, and show that this natural product induces apoptotic cell death and a cell cycle arrest in cancer cells. Interestingly, upon modifying inactive phylloleucobilin by esterification, an anti‐proliferative activity can be observed that increases with the chain lengths of the alkyl esters. We provide first evidence for anti‐cancer activity of phyllobilins, report a novel plant source for a phylloxanthobilin, and by using paper spray MS, show that these bioactive yellow chlorophyll catabolites are more prevalent in Nature than previously assumed. The major chlorophyll catabolites are colorless phyllobilins with four deconjugated pyrrole units. Their yellow oxidation products, are getting more and more in the spotlight due to their interesting physicochemical properties and potential bioactivities. Although studies on physiologically relevant activities of phyllobilins are in early stages, it already becomes evident that when it comes to bioactivities, yellow beats colorless.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.202000692