In 1975, the Biological and Toxin Weapons Convention was ratified by several countries. In spite of the agreement, bioweapon threats from groups such as terrorist organizations and rogue states continue to worry public health authorities [71].
R. communis is widely used for medicinal purposes in traditional medicine [45], despite the highly toxic nature of ricin. Tyagi et al. [79] conducted an extensive review of the recent advances in ricin research and its potential therapeutic applications, especially as an anticancer agent.
1.10 Poisonous Plants as Carcinogens and Teratogens
Some plant species contain teratogenic substances, which can cause deformities or abnormalities in the developing fetus in animals when ingested by the mother. However, no species have been shown to be specifically responsible for malformations in humans. The teratogenicity of plants has been demonstrated when they are ingested by some animals as part of their fodder. Teratogens usually act early in the gestation period of an animal, making it hard to pinpoint the exact causative agent when the malformations manifest [80]. Some plant species and their respective or suspected teratogenic compounds have been demonstrated in laboratory animals at large doses not normally consumed by humans. These include alkaloids from Senecio spp., which are responsible for possible teratogenic effects in rats and in utero deaths of calves, and Nicotiana spp. and Lobelia spp., which are responsible for some skeletal deformations in pigs [21].
Some compounds have been shown to promote liver cancer in rats, although they occur naturally in very low concentrations, which are typically far below the toxic concentrations in products consumed by humans. Such carcinogenic compounds include alkenylbenzene and its derivatives, which are found in products such oils from Sassafras, star anise, and nutmeg [21].
Other carcinogens or co‐carcinogens are the betel quid and tigliane and daphnane derivatives and related diterpenes. Bracken (Pteridium aquilinum) is also carcinogenic and has been implicated in bovine poisoning. Aristolochic acid from Aristolochia spp. is both nephrotoxic and carcinogenic and has thus been banned in many countries.
1.11 Conclusion
Poisonous plants offer an exciting window of opportunity for the discovery of various biologically active substances that could find applications as novel drugs, biopesticides, or research tools. However, more research is needed to determine the actual toxicity of several medicinal plants used in traditional medicine, especially in Africa.
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