Specific Distribution of Pyrrolizidine Alkaloids in Floral Parts of Comfrey (Symphytum officinale) and its Implications for Flower Ecology

Abstract

Pyrrolizidine alkaloids (PAs) are a typical class of plant secondary metabolites that are constitutively produced as part of the plant's chemical defense. While roots are a well-established site of pyrrolizidine alkaloid biosynthesis, comfrey plants (Symphytum officinale; Boraginaceae) have been shown to additionally activate alkaloid production in specialized leaves and accumulate PAs in flowers during a short developmental stage in inflorescence development. To gain a better understanding of the accumulation and role of PAs in comfrey flowers and fruits, we have dissected and analyzed their tissues for PA content and patterns. PAs are almost exclusively accumulated in the ovaries, while petals, sepals, and pollen hardly contain PAs. High levels of PAs are detectable in the fruit, but the elaiosome was shown to be PA free. The absence of 7-acetyllycopsamine in floral parts while present in leaves and roots suggests that the additional site of PA biosynthesis provides the pool of PAs for translocation to floral structures. Our data suggest that PA accumulation has to be understood as a highly dynamic system resulting from a combination of efficient transport and additional sites of synthesis that are only temporarily active. Our findings are further discussed in the context of the ecological roles of PAs in comfrey flowers.

Analysis of Pyrrolizidine Alkaloids in Queensland Honey: Using Low Temperature Chromatography to Resolve Stereoisomers and Identify Botanical Sources by UHPLC-MS/MS

“…In individual honeys, lycopsamine (3) was detected at up to ≈3100 ng/g, indicine (2) at up to 1700 ng/g, with the highest total PA content in any individual honey of ≈3300 ng/g which contained mainly a mixture of lycopsamine (3) and lycopsamine N-oxide (6). (2) and lycopsamine N-oxide (6).…”

“…Plants containing pyrrolizidine alkaloids are globally distributed and PAs provide a chemical defence for plants against herbivores. PA biosynthesis has been found to be dependent on many factors, with implications for plant/animal/insect interactions [3]. Various food products can contain toxic PAs either directly from plant origin (certain herbs, herbal medicines) or indirectly through natural transfer from floral nectar and pollen (e.g., some honey, pollen dietary supplements) or inadvertent cross-contamination (e.g., grains, herbs, teas) [4].…”

Discriminant analysis of pyrrolizidine alkaloid contamination in bee pollen based on near-infrared data from lab-stationary and portable spectrometers

“…Indeed, both the PA/PANO concentration and composition depend on the botanical taxon, geographical origin [35] and developmental stage of the plants. Moreover, synthesis of PAs/ PANOs by plants is influenced by many other agronomic and environmental factors such as soil fertility, water availability and climate conditions [36][37][38]. Since most bee pollen samples analysed were from Italy and other European countries, possible sources of the lycopsaminetype PAs/PANOs could be plants from the genus Echium (e.g., E. vulgare), which is known to produce high levels of echimidine and its N-oxide, and Borago officinalis and Eupatorium cannabinum that synthesise lycopsamine, lycopsamine N-oxide and their isomers.…”

Chemotaxonomic Investigation of Apocynaceae for Retronecine-Type Pyrrolizidine Alkaloids Using HPLC-MS/MS

“…PA accumulation often has a distinctly organ and developmental stage specific pattern that is variable among species (Hartmann and Zimmer, 1986;Irmer et al, 2015;Stegemann et al, 2018). In…”