Metabolism of ricinine in the castor plant

Can omic tools help generate alternative newer sources of edible seed oil?

There are three pathways for triacylglycerol (TAG) biosynthesis: De novo TAG biosynthesis, phosphatidylcholine-derived biosynthesis, and cytosolic TAG biosynthesis. Variability in fatty acid composition is mainly associated with phosphatidylcholine-derived TAG pathway. Mobilization of TAG-formed through cytosolic pathway into lipid droplets is yet unknown. There are multiple regulatory checkpoints starting from acetyl-CoA carboxylase to the lipid droplet biogenesis in TAG biosynthesis. Although a primary metabolism, only a few species synthesize oil in seeds for storage, and less than 10 species are commercially exploited. To meet out the growing demand for oil, diversifying into newer sources is the only choice left. The present review highlights the potential strategies targeting species like Azadirachta, Callophyllum, Madhuca, Moringa, Pongamia, Ricinus, and Simarouba, which are not being used for eating but are otherwise high yielding (ranging from 1.5 to 20 tons per hectare) with seeds having a high oil content (40-60%). Additionally, understanding the toxin biosynthesis in Ricinus and Simarouba would be useful in developing toxin-free oil plants. Realization of the importance of cell cultures as "oil factories" is not too far into the future and would soon be a commercially viable option for producing oils in vitro, round the clock.

[Sebotropic drug eruption after ingestion of bee pollen]

INTRODUCTION

The medical literature contains five cases of exanthema with sebaceous tropism induced by consumption of kava-kava extract filed under the name of sebotropic drug reaction. Herein we report a new case following consumption of bee pollen.

PATIENTS AND METHODS

A 37-year-old man consulted for erythemato-papular and fixed plaques of the face, upper trunk and shoulders present for 3 days. Standard blood tests were normal except for neutrophil leukocytosis at 9.8 G/l and eosinophilia at 1.4 G/l. Cutaneous biopsy of a facial plaque revealed folliculocentric lesions with necrosis of sebocytes in the sebaceous gland, associated with an eosinophil-rich infiltrate. The patient had begun consuming bee-pollen granules 3 weeks before the onset of symptoms. The rash regressed within 3 weeks of cessation of pollen consumption. Patch tests (ICDRG battery, propolis 1% Vaseline dilution and bee pollen provided by the patient, both pure and in a 30% dilution in Vaseline) were negative at 48 and 72h.

DISCUSSION

The clinical-pathological correlation was consistent with a diagnosis of sebotropic drug reaction induced by the consumption of bee pollen. The diagnosis was based on papular exanthema of the seborrheic zones occurring 2 to 3 weeks after initial intake of the offending substance, with histological evidence of inflammatory necrosis of the sebaceous glands.

CONCLUSION

We report what is to our knowledge the first case of sebotropic drug reaction following ingestion of bee pollen.

Evaluation of ricinine, a ricin biomarker, from a non-lethal castor bean ingestion

A case is presented of the attempted suicide of a 58-year-old man using castor beans. The patient came to the emergency room complaining of nausea, vomiting and diarrhea for nine hours following the ingestion of six castor beans. Urine samples were taken throughout the hospital stay and submitted to the Centers for Disease Control and Prevention for analysis of ricinine, a castor bean component. The samples were found to be positive for ricinine, with a maximum concentration of 674 µg/g-creatinine excreted approximately 23 h post-exposure. Subsequent samples demonstrated lower ricinine concentrations, with the final sample taken at 62 h post-exposure at a concentration of 135 µg/g-creatinine of ricinine. The estimated urinary excretion half-life was approximately 15 h and the recovery of ricinine in the urine over the three days was estimated to be less than 10%. The patient fully recovered with supportive care and was discharged from the hospital six days after admission.

Suicidal death after injection of a castor bean extract (Ricinus communis L.)

The castor bean plant (Ricinus communis L.) or wonder tree is cultivated in many countries as an ornamental annual plant in gardens. The highest concentration of the lectin ricin is present in the seeds and pods. Ricin is considered as one of the most toxic natural poisons. Ricinine is a piperidine alkaloidal toxin present in castor bean and is described as a biomarker for the exposure to ricin. A case report is presented of a 49-year-old man who committed suicide by intravenous and subcutaneous injection of a castor bean extract. He was brought to the emergency department 24 h after injecting himself. On admission, the patient was conscious and he presented with a history of nausea, vomiting, diarrhoea, dyspnoea, vertigo and muscular pain. Despite symptomatic and supportive intensive care, the man died 9 h after admission due to multiorgan failure. A body external examination was performed. Blood, urine, vitreous humour and the castor bean extract were submitted to the laboratory for toxicological analysis. The identification of ricinine in the extract was performed by solid phase extraction in combination with full-scan gas chromatography/mass spectrometry, high-performance liquid chromatography with photodiode array detection and liquid chromatography/mass spectrometry operated in the full-scan mode, respectively. An extraction procedure with Oasis HLB solid phase extraction cartridges was applied. Chromatography was achieved using a Symmetry C18 column using a gradient mode with 0.15% formic acid and 0.15% formic acid in acetonitrile as mobile phase. Exposure to the castor bean extract was confirmed by identification of the biomarker ricinine in blood, urine and vitreous humour using solid phase extraction and liquid chromatography tandem mass spectrometry with electro spray source in positive ionization mode. Multiple reaction monitoring was used for specific detection. To the authors' knowledge, it is the first time that ricinine has been identified in vitreous humour in a case of castor bean poisoning. Based on the clinical symptoms and the results of the toxicological analysis, we concluded that death was caused by intoxication with plant toxins originated from R. communis L.

Metabolism of the alpha-Pyridone Ring of Ricinine in Ricinus communis L

Chemically synthesized ricinine-3,5-(14)C was used to study the metabolism of this alkaloid in the plant which produces it, Ricinus communis L. In a time course study, ricinine-3,5-(14)C was administered to a series of castor plants (Ricinus communis L.) and the radioactivity recovered in the ricinine samples showed a decrease with increase in time. It was also observed that the alkaloid was translocated to the seed. The in vivo conversion of ricinine-3,5-(14)C to respiratory (14)CO(2) occurred in both light and dark and indicated that the alpha-pyridone ring of ricinine could be degraded.In a comparison of the ricinine content of the various tissues it was observed that in the yellow leaf only a trace amount of the alkaloid was present. Preliminary results indicated that the yellow leaf can also metabolize ricinine-3,5-(14)C to (14)CO(2).

Evidence for metabolic turnover of monoterpenes in peppermint

Two types of experimental evidence are presented which suggest that the monoterpenes of peppermint (Mentha piperita L.) are subject to metabolic turnover. In kinetic studies with (14)CO(2), peppermint cuttings rapidly incorporate label into the monoterpenes and then lose most of the label from the monoterpenes, without corresponding changes in the amount of monoterpenes present. When peppermint plants are grown in a controlled environment (16-hr photoperiod, 24 degrees day, 8 degrees night) and analyzed at intervals leaf pair by leaf pair, there is a steady increase in monoterpenes until the time of floral initiation, followed by a rapid decrease. It is suggested that monoterpenes may serve as substrates for energy metabolism in the secretory cells after other stored substrates have been depleted.