Grayanotoxin I variation across tissues and species of Rhododendron suggests pollinator-herbivore defence trade-offs

Fattorini, Róisín; Egan, Paul A.; Rosindell, James; Farrell, Iain W.; Stevenson, Philip C.

doi:10.1016/j.phytochem.2023.113707

Cited by 4 publications

(2 citation statements)

References 51 publications

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“…The literature shows another major toxic compound which appears to be found in Rhododendron species leaves—grayanotoxin I ( Figure 4 ) [ 65 ]. It is a cyclic diterpene with biological activity similar to the Veratrum alkaloids.…”

Section: Resultsmentioning

confidence: 99%

Phytochemical Profiling and Biological Activities of Rhododendron Subsect. Ledum: Discovering the Medicinal Potential of Labrador Tea Species in the Northern Hemisphere

Vengrytė,

Raudonė

2024

Plants

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Rhododendron subsect. Ledum is a distinct taxonomic subdivision within the genus Rhododendron, comprising a group of evergreen shrubs and small trees. This review will comprehensively analyse the phytochemical profiles and biological properties of the Rhododendron subsect. Ledum species subsect. Ledum consists of eight plant species indigenous to temperate and subarctic regions of the Northern Hemisphere, collectively known as Labrador tea. Recent investigations have concentrated on the phytochemical constituents of these plants due to limited data, emphasizing their evergreen nature and potential industrial significance. This review summarizes their major phytochemical constituents, including flavonoids, phenolic acids, and terpenoids, and discusses their potential biological activities, such as antioxidant, anti-inflammatory, antimicrobial, antitumor, hypoglycemic, hepatoprotective, neuroprotective, and cardioprotective effects. Traditional uses of these plant species align with scientific findings, emphasizing the significance of these plants in traditional medicine. However, despite promising results, gaps exist in our understanding of specific compounds’ therapeutic effects, necessitating further research for comprehensive validation. This review serves as a valuable resource for researchers, identifying current knowledge, uncertainties, and emerging trends in the study of the Rhododendron subsect. Ledum species.

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Section: Resultsmentioning

confidence: 99%

Phytochemical Profiling and Biological Activities of Rhododendron Subsect. Ledum: Discovering the Medicinal Potential of Labrador Tea Species in the Northern Hemisphere

Vengrytė,

Raudonė

2024

Plants

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“…The high variation of lethal doses might originate from the high interspecific variation of Grayanatoxins in leaves of Rhododendron spp. (Fattorini et al 2023 ). Symptoms are described to subside within one to two days after the end of exposure (Puschner 2003 ; Jansen et al 2012 ).…”

Section: Discussionmentioning

confidence: 99%

Rhododendron poisoning in alpacas (Vicugna pacos) in Northern Germany

Schregel,

Zdora,

Gerhauser

et al. 2024

Vet Res Commun

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Poisoning is often suspected to be the origin of disease in South American camelids (SACs) by owners, but only in a few cases this assumption can be confirmed. In small ruminants, rhododendron poisoning is a common emergency for livestock veterinarians. However, this condition has rarely been reported in SACs so far. This paper provides information regarding clinical findings, hematology, clinical chemistry, and treatment of four alpacas after presumed intake of rhododendron leaves including pathological findings of one of the animals. Rhododendron leaves contain grayanatoxins that lead to hyperpolarization of excitable cells. Clinical signs that were observed in the presented alpacas comprised: salivation, dehydration, decreased motility of compartment 1, uncoordinated regurgitation, and cardiac arrhythmia. Clinical chemistry revealed that rhododendron poisoning was associated with metabolic acidosis and azotaemia, hyponatremia and hyperkalemia. Most striking macroscopic and histopathological findings included gastric ulceration, and renal infarcts along with inflammatory changes. Leaves of Rhododendron spp. were identified in the forestomach content of this animal. Affected animals were treated symptomatically as there is no specific antidote in rhododendron poisoning. This included parenteral rehydration, treatment of metabolic acidosis (infusion of sodium bicarbonate solution), and oral administration of activated charcoal to bind potential toxins. In addition, antibiotic treatment might be necessary to prevent aspiration pneumonia in case of uncoordinated regurgitation. Of the four animals, the worst affected alpaca was euthanized, one had minimal signs and two responded to supportive care and recovered. In conclusion, rhododendron poisoning might be fatal for alpacas in individual cases and therefore rhododendron bushes should not be placed in the habitat of SACs.

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High toxin concentration in pollen may deter collection by bees in butterfly-pollinated Rhododendron molle

Feng,

Lv,

Yang

et al. 2024

Annals of Botany

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Backgrounds and Aims The hypothesis that plants evolve features that protect accessible pollen from consumption by flower visitors remains poorly understood. Methods To explore potential chemical defenses against pollen consumption, we examined the pollinator assemblage, foraging behaviour, visitation frequency and pollen transfer efficiency in Rhododendron molle, a highly toxic shrub containing Rhodojaponin III. Nutrient (protein and lipid) and toxic components in pollen and other tissues were measured. Key Results Overall in the five populations, floral visits by butterflies and bumblebees were relatively more frequent than visits by honeybees. All foraged for nectar but not pollen. Butterflies did not differ from bumblebees in the amount of pollen removed per visit, but deposited more pollen per visit. Pollination experiments indicated that R. molle was self-compatible, but both fruit and seed production were pollen limited. Our analysis indicated that the pollen was not protein-poor and had a higher concentration of the toxic compound Rhodojaponin III than petals and leaves, which compound was undetectable in nectar. Conclusion Pollen toxicity in Rhododendron flowers may discourage pollen robbers (bees) from taking the freely accessible pollen grains, while the toxin-free nectar rewards effective pollinators, promoting pollen transfer. This preliminary study supports the hypothesis that chemical defense in pollen would be likely to evolve in species without physical protection from pollinivores.

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Grayanotoxin I variation across tissues and species of Rhododendron suggests pollinator-herbivore defence trade-offs

Cited by 4 publications

References 51 publications

Phytochemical Profiling and Biological Activities of Rhododendron Subsect. Ledum: Discovering the Medicinal Potential of Labrador Tea Species in the Northern Hemisphere

Phytochemical Profiling and Biological Activities of Rhododendron Subsect. Ledum: Discovering the Medicinal Potential of Labrador Tea Species in the Northern Hemisphere

Rhododendron poisoning in alpacas (Vicugna pacos) in Northern Germany

High toxin concentration in pollen may deter collection by bees in butterfly-pollinated Rhododendron molle

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