Abstract
Accidental and intended Ricinus communis intoxications in humans and animals have been known for centuries but the causative agent remained elusive until 1888 when Stillmark attributed the toxicity to the lectin ricin. Ricinus communis is grown worldwide on an industrial scale for the production of castor oil. As by-product in castor oil production ricin is mass produced above 1 million tons per year. On the basis of its availability, toxicity, ease of preparation and the current lack of medical countermeasures, ricin has gained attention as potential biological warfare agent. The seeds also contain the less toxic, but highly homologous Ricinus communis agglutinin and the alkaloid ricinine, and especially the latter can be used to track intoxications. After oil extraction and detoxification, the defatted press cake is used as organic fertilizer and as low-value feed. In this context there have been sporadic reports from different countries describing animal intoxications after uptake of obviously insufficiently detoxified fertilizer. Observations in Germany over several years, however, have led us to speculate that the detoxification process is not always performed thoroughly and controlled, calling for international regulations which clearly state a ricin threshold in fertilizer. In this review we summarize knowledge on intended and unintended poisoning with ricin or castor seeds both in humans and animals, with a particular emphasis on intoxications due to improperly detoxified castor bean meal and forensic analysis.
Highlights
The castor oil plant Ricinus communis, known as Palma(e) Christi or wonder tree, is a perennial scrub of the spurge family Euphorbiaceae (Figure 1a)
When reviewing case reports of ricin intoxications in humans, “effective” ricin doses that have been incorporated can only be estimated according to variations in the size, weight and moisture content of the seeds; cultivar, region, season and period of plant growth at the time of uptake as well as degree of mastication, stomach content, age and comorbidities which are obviously more heterogeneous compared to experimental poisoning of animals [111]
Ricinus communis is of economic interest for the production of castor oil and the numerous industrial, medical and cosmetic products derived thereof
Summary
The castor oil plant Ricinus communis, known as Palma(e) Christi or wonder tree, is a perennial scrub of the spurge family Euphorbiaceae (Figure 1a). Ricin is not the only toxic protein in the seeds, it shares a high degree of homology with R. communis agglutinin. Sophisticated sequence analysis methods have revealed that ricin and R. communis agglutinin are not single-copy genes Rather they are members of a ricin gene family encoding seven full-length ricin or ricin-like proteins and several potential shorter gene products of unknown expression and function, reflecting a much greater variability than previously anticipated [121,122]. Based on the variability described, it could be retrospectively assumed that the toxicity of ricin has mostly been determined with toxin preparations containing a mixture of differently glycosylated ricin isoforms (which might or might not contain R. communis agglutinin to a variable degree, especially in the older literature when chromatographic separation techniques were not as advanced as today). 1.36 and 1.40 mg/kg after intravenous injection [56,134]
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