Cyanogenic Glycosides
Dongyou Liu in Handbook of Foodborne Diseases, 2018
Glycoside is a molecule composed of a sugar (known as glycone, either single [monosaccharide] or multiple [oligosaccharide]) and a functional, nonsugar group (known as aglycone or genin) connected via a glycosidic bond. The glycone and aglycone portions of a glycoside can be separated by hydrolysis in the presence of acid or alkali, or cleaved by specific enzymes (e.g., glycoside hydrolases, and glycosyltransferases). A glycoside containing a glucose (fructose or glucuronic acid) in its glycone group is known as glucoside (fructoside or glucuronide). According to the chemical nature of the aglycone group, glycoside is classified into alcoholic glycoside, anthraquinone glycoside, coumarin glycoside, chromone glycoside, cyanogenic glycoside, flavonoid glycoside, phenolic glycoside, saponin glycoside (or saponin), steroidal glycoside (or cardiac glycoside), steviol glycoside, iridoid glycoside, and thioglycoside. The linkage between the glycone and aglycone groups in glycoside may be an O- (O-glycoside), N- (glycosylamine), S- (a thioglycoside), or C- (C-glycoside) glycosidic bond. In addition, depending on whether the glycosidic bond lies “below” or “above” the plane of the cyclic sugar molecule, glycoside may be referred to as α-glycosides (hydrolyzed by α-amylase) or β-glycosides (hydrolyzed by β-glucosidase or emulsin). Characterized by the presence of D-glucose or gentiobiose in its glycone group, cyanohydrin in its aglycone group (which, like other cyanides, contains the –C≡N group in its structure), and O-β-glycosidic bond, cyanogenic glycoside is made by a number of plants and stored in inactive forms in the vacuole that prevents from self-damage under normal conditions. When the plant is attacked (or macerated), cyanogenic glycoside is released and its sugar part is removed by enzymes found in the cytoplasm. Subsequent collapse of the cyanohydrin structure releases toxic hydrogen cyanide (HCN) in a process known as cyanogenesis, which deters herbivores and insects, and causes cyanide poisoning in animals and humans [1].
Phytochemicals: Some Basics
Scott Mendelson in Herbal Treatment of Major Depression, 2019
Carbohydrates are found in all plants and share the basic chemical formula of C(HO). They can be found as simple sugars or as the complex interconnected sugar molecules of polysaccharides, starches, and cellulose. They serve as structural elements of plant cells and tissues, as well as primary sources of energy for metabolism in both plants and animals. Simple sugars may bind to non-sugar phytochemicals, thus forming glycosides. Some glycosides have important medicinal properties, with the cardiac glycosides, such as digoxin, being perhaps the best known and most important of this class. Inside the plant, the bound sugars may compartmentalize and control the activity of the glycosidic phytochemical, often inactivating it, with release of the active component by enzymatic, hydrolytic splitting. In herbal medicines, glycosides have different pharmacokinetics and bioavailabilities than the aglycone molecules. For example, most flavonoids, discussed below, exist naturally as glycosides. The glycosidic forms can have different pharmacological properties than the aglycone forms. Flavonoid glycosides often produce higher plasma levels and have longer halflives than those of aglycones. Carbohydrates themselves have not generally been seen as possessing significant pharmacological effects. There have been reports of various carbohydrates affecting glucose metabolism, though often through simple mechanisms, such as inhibiting gastrointestinal α-amylase and α-glucosidase activities to slow glucose absorption and improve its metabolism. There are exceptions. The oriental medicinal herb, fuzi, or Aconitum carmichaeli, has for centuries been used to treat chronic wounds, poor circulation, spasms, and mood disorders.
General pharmacology
Fazal-I-Akbar Danish, Ahmed Ehsan Rabbani in Pharmacology in 7 Days for Medical Students, 2018
Cardiac glycosides: Like digoxin, digitoxin, gitoxin.
Oral microemulsion based delivery system for reducing reproductive and kidney toxicity of Tripterygium glycosides
Published in Journal of Microencapsulation, 2019
Jiemin Wang, Chuanbang Wang, Junyong Wu, Yongjiang Li, Xiongbin Hu, Jing Wen, Jiaxin Cai, Shilin Luo, Xinyi Liu, Daxiong Xiang
Aim: To reduce the toxic effects and achieve efficiency of Tripterygium glycosides, an oral microemulsion was designed. Method: After estimating its stability and characterisation, an animal experiment was held to evaluate its toxicity in vivo, using male and female Sprague Dawley rats. Result: The maximum loading amount of microemulsion to Tripterygium glycosides was 18.87 mg/ml. And comparing to control, the Tripterygium glycoside microemulsion can maintain a normal level of the number of sperms, the weight of testicle, testosterone (∼2.5 ng/mL) and BUN (∼5 mmol/L) to male rats. For female rats, it can prevent the ovary to be atrophy and keep FSH to be stable (>2100 ng/L). The weaker injury induced by drug-loaded microemulsion to rats also could be observed in histological sections to kidney and reproductive organs. Conclusions: Although the blank microemulsion had slight toxicity, it mitigated the toxicity of Tripterygium glycosides to kidney and reproductive system.
Decomposition of α-Tocopheryl Glycosides in Rat Tissues
Published in Toxicology Mechanisms and Methods, 2008
Małgorzata Knaś, Piotr Wałejko, Jadwiga Maj, Agnieszka Hryniewicka, Stanisław Witkowski, Małgorzata Borzym-Kluczyk, Danuta Dudzik, Krzysztof Zwierz
Background: The aim of our investigation was to estimate the stability of α-tocopheryl O-glycosides in relation to activity of exoglycosidases in selected rat tissues. Material and Methods: Acetylated glycosides were obtained in glucosidation of α-tocopherol using the Helferich method. The activity of exoglycosidases was determined by the Zwierz et al. method. Protein concentrations were determined by the biuret method. The concentration of released α-tocopherol was determined with the HPLC method. Results: The comparison of the amount of released α-tocopherol with the amount of released p-nitrophenol shows that glycoside bound in 2a–5a derivatives of α-tocopherol undergoes hydrolysis significantly harder than in appropriate 2b–5b p-nitrophenyl derivatives. Conclusion: The results indicate that tocopheryl O-glycosides are more resistant to enzymatic hydrolysis than appropriate p-nitrophenol O-glycosides 2a–5a. Among examined tocopheryl O-glycosides, galactoside 4 is the only compound that caused the significant increase in tocopherol concentration, as compared to its endogenic content.
A research on the genotoxicity of stevia in human lymphocytes
Published in Drug and Chemical Toxicology, 2018
Aslı Uçar, Serkan Yılmaz, Şemsigül Yılmaz, Mustafa Sefa Kılıç
Stevia extracts are obtained from Stevia rebaudiana commonly used as natural sweeteners. It is ∼250–300 times sweeter than sucrose. Common use of stevia prompted us to investigate its genotoxicity in human peripheral blood lymphocytes. Stevia (active ingredient steviol glycoside) was dissolved in pure water. Dose selection was done using ADI (acceptable daily intake) value. Negative control (pure water), 1, 2, 4, 8 and 16 μg/ml concentrations which were equivalent to ADI/4, ADI/2, ADI, ADI × 2 and ADI × 4 of Stevia were added to whole-blood culture. Two repetitive experiments were conducted. Our results showed that there was no significant difference in the induction of chromosomal aberrations and micronuclei between the groups treated with the concentrations of Stevia and the negative control at 24 and 48 h treatment periods. The data showed that stevia (active ingredient steviol glycosides) has no genotoxic activity in both test systems. Our results clearly supports previous findings.
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