*3.1. Oral Toxicity*

In humans, most intoxications occurred accidentally or voluntarily with the ingestion of castor seeds; only a few cases of intentional absorption of castor bean extracts have been documented in suicide attempts [76]. Whole-ingested beans can pass intact through the gastrointestinal tract, whereas chewing facilitates ricin release. Also, it has been reported that the seed can act as 'timed-release' capsule for the toxin, allowing its release in the lower bowel, where it causes more damage [72]. After ingestion, vomiting, diarrhea, and abdominal pain are common symptoms. Massive gastrointestinal fluid and electrolyte loss are described, often complicated by hematemesis or melaena. Finally, hypovolemic shock and multiorgan failure occur, which particularly involves the spleen, liver, and kidney [77,78].

Despite the high number of intoxicated subjects with castor beans, it is quite di fficult to calculate LD values for ricin in humans. In fact, the e ffective ingested ricin dose can only be supposed, because of ricin content variations depending on the size, weight, and moisture of the seeds, as well as on cultivar, region, season, and plant growth stage. Moreover, in intoxicated subjects, it must be taken into account the degree of mastication, stomach content, age, and comorbidities, parameters that are obviously more heterogeneous compared to experimental poisoning of animals. Considering all these parameters, the fatal oral dose of ricin in humans has been estimated to range from 1 to 20 mg/kg (approximately 5 to 10 beans) [70,79].
