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2 February 2024 Changes in Mortality, Heart Rate, and Gene Response in Daphnia magna Exposed to Concentrated and Homeopathic Kalmia latifolia Distillates
Jeremy D. Rentsch, Cody B. Collier, Michael P. Jordan
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Kalmia latifolia, the mountain laurel, contains dangerous diterpene grayanotoxins, which make all parts of the plant toxic. Human consumption of honey made from Kalmia and Rhododendron nectar, so-called ‘mad honey,’ can result in serious poisoning. Despite this, homeopathic Kalmia latifolia tincture is available for purchase online. Here, we test a concentrated Kalmia latifolia tincture produced in the laboratory against a commercially available homeopathic Kalmia latifolia tincture. To evaluate outcomes, we treat Daphnia magna with these tinctures and evaluate changes to mortality, heart rate, and the differential expression of several genes related to detoxification and stress response. We find that the concentrated Kalmia latifolia tincture contains cytotoxic compounds beyond the ethanol solvent alone. This is evidenced by lower heart rates in daphnids 24 hours after treatment, and by the upregulation of Hsp90, a stress response gene, when compared to other treatment types. However, ethanol alone was found to cause higher mortality at both 24 and 48 hours than either Kalmia-based tincture. We believe, despite poor solubility, some level of the hydrophobic grayanotoxins dissolve in the ethanol solvent used to create the distillation and are present in the final concentrated tincture making the final tincture likely far less potent than one performed using a strong organic solvent. Ethanol is a poor solvent for grayanotoxins and the final level of cytotoxins in the concentrated tincture is likely quite low. We find relatively little evidence for acute cytotoxicity in daphnids exposed to a concentrated Kalmia latifolia tincture.

Jeremy D. Rentsch, Cody B. Collier, and Michael P. Jordan "Changes in Mortality, Heart Rate, and Gene Response in Daphnia magna Exposed to Concentrated and Homeopathic Kalmia latifolia Distillates," Castanea 88(2), 231-240, (2 February 2024).
Received: 17 August 2023; Accepted: 24 November 2023; Published: 2 February 2024
Alcohol Distillation
Kalmia latifolia
Mountain laurel
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