Introduction:
Cyanogenic glycosides are a class of natural compounds found in a variety of plant species. They are characterised by the presence of a sugar molecule (glycoside) attached to a cyanide-containing molecule. When the glycoside is broken down, either by the plant's enzymes or by enzymes in the digestive system, the cyanide molecule is released. Cyanogenic glycosides are potentially toxic if ingested in large amounts but may also have some beneficial health effects when consumed in moderation. The acute lethal dose of HCN in human beings has been estimated as 0.5-3.5 mg/kg body weight while in animals it is believed to be 0.66 to 15mg/kg body weight (Reddy, 2006).
Importance of Cyanogenic Glycosides:
Determination of cause of death:
In cases where poisoning is suspected as a cause of death, analysis of post-mortem samples for the presence of cyanogenic glycosides can help determine the cause of death. Cyanide toxicity from cyanogenic glycosides can cause respiratory and cardiac failure, and the presence of cyanide in post-mortem samples can be a clear indicator of poisoning. (source: Ferslew et al., 2017)
Assessment of exposure in living individuals:
For living individuals who may have been exposed to toxic plant materials, analysis of biological samples, such as blood and urine, for the presence of cyanogenic glycosides can help assess the extent of exposure and any resulting health effects. (source: Jolly et al., 2020)
Identification of toxic plant materials :
Cyanogenic glycosides are present in many plant species and can be used to identify the plant material involved in a poisoning case. This is particularly important in cases where plant material has been consumed in unusual circumstances, such as in suicide attempts or drug abuse. (source: Musshoff et al., 2018)
Quantification of toxic plant compounds:
The presence and concentration of cyanogenic glycosides in plant material can be measured using analytical methods, such as gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). These methods can be used to quantify the level of exposure to the toxic plant material in cases of suspected poisoning. (source: Zhou et al., 2019)
Sources of cyanogenic glycosides:
Cassava:
Each parts of cassava plants (leaves, stem, root) contains high levels of cyanogenic glycosides; linamarin, lotaustralin, and amygdalin [14, 19], with linamarin been the most predominant cyanogen The cyanide level of cassava varies from about 75 to 350 ppm, but can be up to l000 ppm or more depending on the variety, plant age, soil condition, fertilizer application, weather, and other factors
Cocoyam:
Edible cocoyam is a nutrient dense tuber crop that belongs to Araceae family. Two major species of this family are Taro (Colocasia esculenta L) and Tannia (Xanthosoma Sagittifolium L), The Cocoyam crops have been reported to contain low levels (2.10–17.13 mg/100g) of cyanogenic glycosides [28, 29]. In another study, cocoyam tuber was reported to contain 7.4 mg/100g equivalent cyanide
Bamboo Shoots:
Bamboo shoots also contain lethal concentration of cyanogenic glycosides. The cyanogenic glycoside present in bamboo shoot is taxiphyllin, which is decomposed quickly in boiling water. Cyanide content of bamboo shoot ranged from 1000 to 8000 mg/kg hydrogen cyanide [5, 31]. Although cyanide content of bamboo shoot is much higher than that of cassava root, the cyanide content in bamboo shoots decreases substantially following harvesting and processing
Apple Seeds:
Although apples are rich sources of vitamins and other nutrients, apple seeds contain high levels of cyanogenic glycosides. Amygdalin content of apple seeds ranged from 1 to 4 mg/g while that of apple juice was reported to be between 0.001 and 0.08 mg/ml
Toxicity of cyanogenic glycosides
Cyanide release upon breakdown of glycoside:
Cyanogenic glycosides can release hydrogen cyanide (HCN) upon hydrolysis, which can be toxic to both humans and animals. The hydrolysis of cyanogenic glycosides can occur naturally, as part of plant metabolism or during food processing, or as a result of digestion in the gastrointestinal tract. The release of HCN upon breakdown of cyanogenic glycosides is due to the presence of a glycosidic bond between a sugar molecule and a cyanogenic aglycone. When the bond is broken, either by enzymes or by acidic conditions, the cyanogenic aglycone is released and can be converted to HCN.
This process is illustrated in the following equation:
Cyanogenic glycoside + β-glycosidase → Cyanogenic aglycone + Glucose → HCN + Glucose
Several studies have investigated the release of HCN upon hydrolysis of cyanogenic glycosides in different plant species. For example, a study by Siritunga et al. (2011) found that cassava leaves contained high levels of cyanogenic glycosides, which were hydrolyzed to release HCN during processing. Similarly, a study by Bekele et al. (2018) reported that the hydrolysis of cyanogenic glycosides in bitter cassava resulted in the release of toxic levels of HCN.
Forensic importance Of cyanogenic glycosides
Cyanogenic glycosides have important forensic applications, particularly in cases of plant poisoning and food safety investigations. The detection and quantification of these compounds can provide valuable information for identifying the source of toxicity and establishing the cause of death. One example of the forensic application of cyanogenic glycosides is in the investigation of cassava poisoning. Cassava is a staple food in many tropical regions, but improperly processed cassava can contain high levels of cyanogenic glycosides, which can be toxic to humans. In cases of cassava poisoning, the detection and quantification of cyanogenic glycosides in biological samples can help to establish the cause of death and identify the source of toxicity (Bentsi-Enchill et al., 2014). Cyanogenic glycosides can also be used as markers for plant material in forensic investigations. For example, a study by Kusch et al. (2015) used the detection of cyanogenic glycosides as a marker to identify the presence of plant material in a homicide case involving the dismemberment of a human body. In addition, the detection and quantification of cyanogenic glycosides in food products can be important for ensuring food safety. For example, the European Union has established maximum limits for the cyanogenic glycoside content in certain food products, such as almonds and apricot kernels, to reduce the risk of toxicity (European Commission, 2002).
Case Study:
At a bamboo shoot pickling factory located in the central west of Thailand, Patient 1 (Pt 1) accidentally dropped a 20 kg bag of fresh sliced bamboo shoots into the bamboo shoot pickling well. The well had a 27 m3 capacity (3x3x3 m in size) and partially filled with 20 MT of sliced bamboo shoots. He jumped into the well to retrieve the bag, but immediately lost consciousness in the well. Pt 2 immediately jumped into the well to rescue Pt 1, but also became unconscious in the well. Other workers saw the incident and shouted for help. Pt 3, 4 and 5 jumped into the well to rescue Pt 1 and 2.All of these patients fell prone and became unconscious. Pt 6, the factory owner, arrived and saw the incident. He jumped into the well and also lost consciousness as soon as he was in the well. Pt 7 and 8, the owner’s sons, jumped down to help their father and they also became unconscious. Subsequently, other workers wore cloth masks and tied themselves with ropes and went down to lift the eight patients out of the well. All were unconscious. A rescue team was notified and came to transfer these patients to the hospital 30 min after the incident occurred. The initial clinical features of these patients are summarized in Table 1. All patients were admitted to the hospital. Laboratory tests such as blood chemistry, arterial blood gas (ABG) and chest X-ray were done in most of the patients 30 to 45 min after arrival at the hospital. Serum lactate was not obtained because the hospital was not able to perform the test. Pt 4 and 7 developed cardiac arrest upon arrival in the emergency room. After cardiopulmonary resuscitation, Pt 4’s chest radiograph showed infiltration of right lower and upper lung fields which suggested possible aspiration pneumonitis. Pt 7’s chest radiograph showed only basal infiltration and plate atelectasis. Their chest radiographs did not reveal any significant pathology that might explain the cause of cardiac arrest. However, they had metabolic acidosis and high anion gap. These two patients died at 13 and 30 h after admission, respectively. Pt 2 developed unconsciousness and pulmonary edema with severe metabolic acidosis and high anion gap of 33. ABG revealed combined metabolic and respiratory acidosis. An electrocardiogram showed acute myocardial ischemia. Serum CPK and troponin-I were elevated. After supportive care by respiratory support, the pulmonary edema resolved and consciousness was recovered within 3 days. He was dis- charged from the hospital on the 5th day. Pt 5 and 6 initially developed unconsciousness and needed respiratory support. Serum electrolytes showed metabolic acidosis with anion gap of 28.7 and 33.8, respectively. This supportive care, they recovered quickly and were discharged from hospital on the 3rd day. Pt 8 regained consciousness upon arrival at the hospital but initially complained about chest discomfort and needed to be intubated. X-ray findings were normal. Serum elec- trolyte and ABG also showed metabolic acidosis with anion gap of 27.2. After supportive treatment, Pt 8 was able to be weaned off the respirator and was discharged on the 3rd day. Pt 1 and 3 regained consciousness after arrival at the hos- pital. Their serum electrolytes showed metabolic acidosis with anion gap of 25.9 and 22.3, respectively. Most of the illness fully disappeared within one day. None of the patients received cyanide antidotes because the diagnosis was made after the surviving patients were stable. In addition, cyanide antidote was not available at the hospital. Table 2 shows that chest X-ray revealed lung abnormali- ties only in Pt 2, 4 and 7. Pt 2’s chest X-ray showed pul- monary edema. The oxygenation in ABG of all patients was also normal. Both chest X-ray and ABG suggested that the patients’ ventilation was not the major cause of the illness. However, the ABG and electrolytes did show metabolic acidosis with high anion gap. The elevated anion gap pre- dicted the clinical course for the more severely ill patients. Asphyxia and anoxia were included in the differential diag- nosis. Metabolic acidosis did not resolve soon after oxygen therapy, suggesting systemic asphyxia rather than simple asphyxia. According to these lines of evidence, cyanide poi- soning was suspected. Blood samples were collected from the patients for whole blood cyanide level determination 18 h after the incident occurred. Table 2 shows the whole blood cyanide levels, which shows a correlation with anion gap, as shown in Fig. 2 (correlation coefficient 0.68). Severe cases had higher blood cyanide levels than the less severe patients. Pt 1 and 3, who had the lowest blood cyanide levels and low- est anion gap, recovered from unconsciousness upon arrival at the hospital and had a mild clinical course. Pt 2, having the highest blood cyanide level, developed pulmonary edema and had the longest hospital stay of all the surviving patients. Blood cyanide levels of Pt 7 who died was ranked second after that of Pt 2. Unfortunately, Pt 4’s blood sample was not available for cyanide determination because he died before the diagnosis was made. All of the survivors were followed up for 7 days after the incident; all remained well. Blood samples were then col- lected for cyanide determination; none had detectable cya- nide in the blood level.
References:
- PENSIRIWAN SANG-A-GAD1, SURIYA GUHARAT2, and WINAI WANANUKUL3, A mass cyanide poisoning from pickling bamboo shoots, Researchegate.
- Islamiyat Folashade Bolarinwa,Moruf Olanrewaju Oke,Sulaiman Adebisi Olaniyan and Adeladun Stephen Ajala, A Review of Cyanogenic Glycosides in Edible Plants, Researchegate.
- Manash Pratim Sharma, Analysis of Cyanide Concentration in Five Selected Bamboo Shoots Consumed in North East India, Medwin Publishers.
- Ming Ding and Kailiang Wang, Determination of cyanide in bamboo shoots by microdiffusion combined with ion chromatography–pulsed amperometric detection, The Royal Society Publishing.
- CYANOGENIC GLYCOSIDES - INFORMATION SHEET, Newzealand Food Safety Authority
- Roslyn M. Gleadow1 and Birger Lindberg Møller2,3, Cyanogenic Glycosides: Synthesis, Physiology, and Phenotypic Plasticity, Annual Review of Plant Biology
- Onojah, P.K., and Odin, E. M., Cyanogenic Glycoside in Food Plants, International Journal of Innovation in Science and Mathematics
- "Toxic Plants of North America" by George E. Burrows and Ronald J. Tyrl, as well as numerous scientific articles on the topic.
- Bentsi-Enchill et al., 2014
- Aremu, M. O., & Olaofe, O. (2021). Cyanogenic glycosides in cassava: potential health implications and management strategies. Journal of Food Science and Technology, 58(2), 399-408.)
- Choudhury, M., & Gogoi, B. (2021). Cyanogenic glycosides in bamboo shoot: An overview. Current Research in Food Science, 4, 98-102.)
