tannins and Poisoning

Plants have been used for medicinal purposes for centuries. Health-oriented individuals are turning to herbal teas as alternatives to caffeinated beverages such as coffee, tea, and cocoa and for low-caloric supplements. The popularity of herbal tea consumption has increased significantly during the past two decades in the U.S. Hundreds of different teas made up of varied mixtures of roots, leaves, seeds, barks, or other parts of shrubs, vines, or trees are sold in health food stores. Although chemists have been characterizing toxic plant constituents for over 100 years, toxicological studies of herbal teas have been limited and, therefore, the safety of many of these products is unknown. Plants synthesize secondary metabolites that are not essential in the production of energy and whose role may be in the defense mechanisms as plant toxins to their interactions with other plants, herbivores, and parasites. Pyrrolizidine alkaloids (PAs) were among the first naturally occurring carcinogens identified in plant products, and their presence in herbal teas is a matter of public health significance. Some herbal tea mixtures and single-ingredient herbal teas have been analyzed for toxic/mutagenic potential by bioassay and chromatographic techniques. Numerous human and animal intoxications have been associated with naturally occurring components, including pyrrolizidine alkaloids, tannins, and safrole. Thus, the prevention of human exposure to carcinogens or mutagens present in herbal tea mixture extracts is crucial. Preparation of infusion drinks prepared from plants appears to concentrate biologically active compounds and is a major source of PA poisoning. The quantity and consumption over a long period of time is of major concern. It is recommended that widespread consumption of herbal infusions should be minimized until data on the levels and varieties of carcinogens, mutagens, and toxicants are made available.

Topics: Beverages; Humans; Plants, Medicinal; Poisoning; Public Health; Pyrrolizidine Alkaloids; Safrole; Tannins; World Health Organization

Ruminants consuming either tannic acid or hydrolysable tannins from the Australian yellow-wood tree (Terminalia oblongata) and the Indonesian shrub Clidemia hirta are intoxicated by simple phenolics liberated in the gut. The affinity of these tannins and of the simple phenolic gallic acid for the two proteins casein and pepsin, polyvinylpyrolidone (PVP), activated charcoal and Ca(OH)2 was examined in vitro. The studies were undertaken to predict the effect of these phenolics on digestion and to identify substances that would act as antidotes by precipitating phenolics. Tannins but not gallic acid were precipitated as stable complexes with both pepsin and casein at pH 3-5. Optimal complexing of tannin with protein occurred at a weight ratio of 1:1. Ionic strength and temperature did not affect the amount of tannin precipitated from solution with protein. The precipitation of tannins with PVP and Ca(OH)2 was unaffected by pH within the range 2-8 while maximum binding with activated charcoal occurred between pH 3 and 7. In contrast to protein, the other substances complexed with gallic acid; only gallic acid-PVP complexes were affected by pH. Calcium hydroxide bound more tannin and gallic acid on a weight basis than PVP and charcoal. Both Ca(OH)2 and activated charcoal should complex with phenolics in the forestomach, abomasum and intestines. The reaction of hydrolysable tannins and proteins at the pH found in the abomasum suggests that hydrolysable tannins would interfere with enzyme function and protein digestion post-ruminally rather than in the forestomach.

Topics: Animals; Antidotes; Calcium Hydroxide; Caseins; Charcoal; Dietary Proteins; Hydrogen-Ion Concentration; Pepsin A; Plant Extracts; Plants, Toxic; Poisoning; Povidone; Tannins

Topics: Acacia; Animals; Antelopes; Poisoning; South Africa; Tannins

Topics: Animal Feed; Animals; Body Weight; Calcium Hydroxide; Carbonates; Chickens; Enzymes; Food Additives; Poisoning; Povidone; Surface-Active Agents; Tannins

Topics: Animals; Charcoal; Poisoning; Rats; Tannins

Topics: Alkaloids; Analgesics; Animals; Antidotes; Charcoal; Humans; Hypnotics and Sedatives; Insecticides; Magnesium Oxide; Mice; Poisoning; Tannins

Topics: Animals; Anterior Hypothalamic Nucleus; Hypothalamus; Poisoning; Rats; Tannins

Topics: Adrenal Cortex; Drug-Related Side Effects and Adverse Reactions; Endocrine Glands; Poisoning; Poisons; Psychoses, Substance-Induced; Tannins