Pyrrolic and Dipyrrolic Chlorophyll Degradation Products in Plants and Herbivores.

Marcel Ritter,Daniel Schulze,Matthias Westerhausen,Katrin Muetzlaff,Helmar Görls,Raphael A Seidel,Wilhelm Boland,Vincensius S P Oetama,Georg Pohnert,Anja K Meents

doi:10.1002/chem.201905236

Marcel Ritter, Daniel Schulze + Show 8 more

Open Access

https://doi.org/10.1002/chem.201905236

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Abstract

The degradation of chlorophyll, the omnipresent green pigment, has been investigated intensively over the last 30 years resulting in many elucidated tetrapyrrolic degradation products. With a comparison to the degradation of the structurally similar heme, we hereby propose a novel additional chlorophyll degradation mechanism to mono‐ and dipyrrolic products. This is the first proof of the occurrence of a family of mono‐ and dipyrrols in leaves that are previously only known as heme degradation products. This product family is also found in spit and feces of herbivores with specific metabolomic patterns reflecting the origin of the samples. Based on chromatographic and mass spectrometric evidence as well as on mechanistic considerations we also suggest several tentative new degradation products. One of them, dihydro BOX A, was fully confirmed as a novel natural product by synthesis and comparison of its spectroscopic data.

Highlights

Chlorophyll (Chl) as a major pigment in plants, bacteria, and algae, is produced and degraded annually on a 1012 kilogram scale.[1]
H in red circle marks the products found in heme degradation and C in green circle marks the products that we found in leaves and/or spit/feces of herbivores (ROS = reactive oxygen species, PDPs = propentdyopents, MM = methyl maleimide, MEM = methyl ethyl maleimide, MVM = methyl vinyl maleimide, HA = hematinic acid, BOX = bilirubin oxidation end product)
To verify if the identified chlorophyll degradation products are found in the spit of insects and if their formation is continued during digestion, we investigated a well-established plant/herbivore combination

Summary

Introduction

Chlorophyll (Chl) as a major pigment in plants, bacteria, and algae, is produced and degraded annually on a 1012 kilogram scale.[1]. As known from chlorophyllin, the additional five-ring E of Chl can be oxidized and cleaved resulting in a formic acid group This would lead to the formyl PDPs. For three of the proposed PDP species (dihydro, aldehyde and acid PDPs) the highest amounts were found in the leaves and not in spit or feces (data not shown). The Chl content in the sweet potato leaves was reported in low mg mgÀ1 dry mass.[44] Similar to the observations made during the Chl a in vitro degradation, once the macrocycle is opened, the reactivity for further oxidative transformations is higher, potentially resulting in faster further reactions. Herbivore spit contained significantly higher amounts of PDPs and BOX C compared to leaves (Figure 2) This fits to the overall idea of a stepwise degradation, since those products can only occur after at least one breakage of a five-membered ring. The feces of H. armigera showed no significant differences to S. littoralis whereas C. alterans had overall higher amounts of degradation products indicating a certain species specificity (Figure 2)

Conclusions

Materials and methods

Findings

Conflict of interest