Blue transition metal complexes of a natural bilin-type chlorophyll catabolite

Abstract

Natural pink degradation products of chlorophyll occur in de-greened leaves. They form blue transition metal complexes, some of which show intensive red fluorescence and may serve as highly sensitive reporters of transition metals in plants.

Stereo‐ and Regioselective Phyllobilane Oxidation in Leaf Homogenates of the Peace Lily (Spathiphyllum wallisii): Hypothetical Endogenous Path to Yellow Chlorophyll Catabolites

“…YCCs, in turn, are readily oxidized to PiCCs, a process that occurs spontaneously in the presence of air, and which is assisted by biologically relevant metal ions, such as Zn II ions. [17] PiCCs appear to undergo various further, still uncharacterized reactionsa preliminary observation that is under investigation in our labs.…”

“…Such "oxidized" phyllobilanes (as well as the persistent hmFCCs [10] ) feature structures and chromophores that may also enable them to function as new molecular tools for "non-invasive studies" of senescence processes in leaves and fruit. [17] Furthermore, the chromophores of such "oxidized" phyllobilanes resemble those of some bilins, pigments from heme breakdown with important biological functions, [19] thus calling for attention as to the still elusive biological functions of phyllobilins, [3b] the growing class of bilin-type tetrapyrroles derived from chlorophyll.…”

In Search of Bioactivity – Phyllobilins, an Unexplored Class of Abundant Heterocyclic Plant Metabolites from Breakdown of Chlorophyll

“…In the absence of light, the PxB 12 is generated in leaf extracts in the 15 Z ‐form exclusively (but isomerizes to the E ‐form by light) . The PxB 12 is easily oxidized further, furnishing the pink colored Chl catabolite (PiCC) 13 , the first known example of a natural phylloroseobilin (PrB) . The unsaturated π‐conjugated system of the PrB 13 now stretches over rings B to D and features E ‐configuration at the unsaturated C10 meso position.…”

“…Hence, the (hardly luminescent 15Z‐form of the) PxB 12 behaved as a bidentate ligand for zinc‐ions, furnishing an orange‐yellow 2 : 1 Zn(II)‐complex (Scheme ) that emitted green fluorescence . The weakly luminescent PrB 13 behaved similarly, and behaved as a tridentate ligand for a variety of divalent transition metal ions . Such metal ions were bound in blue colored metal complexes after conversion of 13 from its stable 10 E ,15 Z ‐arrrangement into its (instable and elusive) 10 Z ,15 Z ‐form.…”

Von Chlorophyll abstammende gelbe Phyllobiline höherer Pflanzen als umgebungsgesteuerte, chirale Photoschalter

“…Phylloxanthobiline (PxBs), wie auch die verwandten rosafarbenen Phylloroseobiline, [33] sind natürliche Pigmente,die Sonnenlicht absorbieren, als Sonnenschutz fungieren und zur Pigmentierung seneszenter Blätter beitragen. [2,11,21] Derartige Phyllochromobiline sind recht hydrophob und daher vermutlich weitgehend protein-oder membrangebunden, was ihnen mçglicherweise eine effektive Rolle als Inhibitoren bei der Autoxidation verleiht.…”