" Cyanogenic glycosides: physiology and regulation of synthesis "

Flaxseed’s role as the "nutraceutical food of the 21st century" is enhanced by its potential effect on breast and colon cancer prevention, according to Dr. Lilian Thompson, Professor, Department of Nutritional Sciences, Faculty of Medicine, University of Toronto. Dr. Thompson was part of the symposium "Flaxseed in Human Nutrition" at the 16th International Congress of Nutrition in Montreal in July 1997. Dr. Thompson presented data on flaxseed and its effect on breast and colon cancer prevention. Flaxseed is the richest plant source of lignan precursors — important because the lignans that mammals produce from this food precursor have been shown to be protective against breast and colon cancer. In animal studies, Dr. Thompson found that flaxseed affects all three stages of cancer development — initiation, tumour development and tumor growth and spread. "Human studies are needed to confirm, but flaxseed has tremendous potential to positively affect our health," Dr. Thompson said.

Flaxseed contains Secoisolariciresinol diglucoside (SDG), a potent antioxidant and a known precursor of the mammalian lignans, enterolactone and enterodiol. These compounds have other pharmacological properties including phytoestrogen properties similar to isoflavones. Studies performed in the Department of Physiology, College of Medicine, University of Saskatchewan, have shown that SDG prevents the development of hypercholesterolemic atherosclerosis, reduces total cholesterol and LDL-cholesterol, and has a tendency to raise HDL-cholesterol in animal models. In addition, SDG has shown the ability to lower blood pressure, and has demonstrated that it is effective in preventing diabetes mellitus (Type I and Type II) and endotoxic shock.

New (soft) technologies (as pioneered by Gaia Research) can produce products that extend the nutraceutical properties ascribed to flaxseed while minimizing drawbacks associated with the consumption of whole flaxseed, which are usually consumed associated with baked goods, which damages the EFA’s and other healthful components. Correctly processed raw flaxseed can have reduced levels of the strong laxative/purgative effects normally associated with the high cyanogenic glycoside mucilage component of flaxseed, which otherwise releases toxic hydrogen cyanide via auto-hydrolysis in the presence of water in the gut. Although this is associated with a non-targeted additional laetrile-type of anti-cancer effect, it strongly limits the amount of the most healthful SDG, which could otherwise be consumed. A typical concentration of SDG in oil-free flaxseed is around 1.5%. Careful processing can concentrate the SDG, whilst reducing the glycosides, allowing for a much-reduced gastric challenging serving size suitable for an optimal daily dosage.

Cyanogenic glycosides and cyanohydrins in plant tissues.

 Facile synthesis of cyanogen glycosides (R)-prunasin, linamarin and (S)-heterodendrin

Biosynthesis of cyanogenic glycosides.

Although ingestion of the cyanogenic glycoside was associated with a significant teratogenic response, the effects occurred only at doses that elicited signs of maternal intoxication (Frakes et al., 1985).

“A novel cytotoxic flavonoid glycoside from .” 2001 Aug.

During cassava starch production, large amounts of cyanoglycosides are released and hydrolysed by plant-borne enzymes, leading to cyanide concentrations in wastewater as high as 200 mg/litre (Siller & Winter, 1998).

Cyanogenic Glycosides: Synthesis, Physiology, …

Persistent use or abuse of anthraquinone glycosides medications, beside its strong anti-bacterial, antioxidant and anti-diabetic activities, could elicit fluid and electrolyte loss, rhabdomyolysis, renal failure and acute hepatic failure (; ; ). Cardiac glycosides derivatives of digitalis and strophanthus such as ouabain are notable inhibitor of Na+/K+-ATPase activity of biomembranes (; ). Similarly, cardiac glycosides have been linked with hyperkalaemia (). The diterpenoid glycosides or atractylosides and other analogues from beans are naturally present in many plants of ethnomedicinal importance and animal grazing forage in Europe, Africa, South America and Asia. Fatal outcomes following the consumption of diterpenoid glycosides include renal proximal tubule necrosis and/or centrilobular hepatic necrosis in man and farm animals (). Also, of diterpenoid glycosides is associated with competitive inhibition of adenine nucleoside carrier and thus blocks oxidative phosphorylation in isolated mitochondria cocktail (). By their chemical nature, cyanogenic glycosides are β-linked glycosides of α-hydroxynitriles. Cyanogenic glycosides are biosynthesized from at least 2, 650 species of plants (). The L-s are biosynthetic precursors of the cyanogenic glycosides. According to the s are first hydroxylated to yield N-hydroxyls, which are converted to aldoximes and subsequently to nitriles. Next, the hydroxylation of nitriles yields α-hydroxynitriles, which are then glycosylated to yield cyanogenic glycosides. Consumption of cyanogenic glycosides containing plants results to the release of hydrogen cyanide into systemic circulation, which inactivates cytochrome oxidase in the mitochondrial electron transport chain of cells and thereby engenders decreased utilization of oxygen in peripheral tissues. Long-term exposure to cyanide toxicity causes upper motor neuron characterized by irreversible paralytic disorder, tropical ataxic neuropathy, optical atrophy, angular stomatitis; sensory gait ataxia; and neurosensory deafness, goitre and cretinism. Cyanogenic glycosides are present in species of (rose family) in particular in spp., cassava (Crantz), Cherry (), as well as other species such as peach (), plum (), almond () and apricot () (; ; ). Some notable cyanogenic glycosides present in edible parts of plants include: amygdalin (almonds), dhurrin (sorghum), linamarin (cassava, lima beans), lotaustralin (cassava, lima beans), prunasin (stone fruit) and taxiphyllin (bamboo shoots) ().

Ap lit open ended essays - Cyanogenic glycoside synthesis

Anthraquinone glycosides are present in fairly limited distribution in plants. In traditional Chinese medicine, anthraquinone glycosides from (rhubarb) in the non-boiled form are administered when catharsis was the desired outcome (; ). Aglycone anthraquinone are anti-fungal, impede renal tubular proliferation and ameliorate inflammations by partial inhibition of the cyclooxygenase pathway (). Notable plants containing cardiac glycosides include: Dogbane (sp.), Lily of the Valley (sp.), Foxglove (sp.), Oleander (Yellow Oleander (spp.) and Milkweeds ( sp.) (). Cardiac glycosides all contain steroids as the aglycone. Cardiac glycosides from foxglove (sp.), sond, as well as lanoxin derivative from number of plants in low doses serve as medication for cardiac disorders in humans (; ; ).

A Review of Cyanogenic Glycosides in Edible Plants

Glycosides: Glycosides are found in virtually every and have vast therapeutic efficacy and, certain cases, toxic effect depending on the plant of origin and the dose of plant product ingested. They are glycosylated bioactive principles in which the aglycone moieties are constituted of the alkaloids, vitamins, polyphenols, steroids, terpenoids or antibiotics etc. bound to a mono- or oligosaccharide or to uronic acid (). Glycobiology has revealed that the glycosidic residue is crucial for bioactivity; in other circumstances, glycosylation improves pharmacokinetic parameters and may serve as leads to the development of new and more active drugs, as typified by the recently developed antibiotics-vancomycin (). A precise overview of physiologic role of glycosyl residue in bioactive principles as well as the structure/activity relationship has been described (). The most encountered glycosides of medicinal and toxicological importance are the vitamins glycosides, polyphenolic glycosides (anthraquinone glycosides), alkaloid glycosides, glycosides in the group of antibiotics (streptomycin), glycopeptides, cardiac glycosides, steroid and terpenoid glycosides, cyanogenic glycosides etc. (; ; ; ; ; ).