Food Toxicology and Flavonoids Overview
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Questions and Answers

Flavonoids are classified as a type of carbohydrates.

False (B)

The average diet in the Western world may include more than 1 g of flavonoids daily.

True (A)

Condensed tannins are identical to hydrolyzable tannins.

False (B)

Tannic acid is known to cause acute liver injury.

<p>True (A)</p> Signup and view all the answers

Quercetin is considered safe and non-carcinogenic in mammals.

<p>False (B)</p> Signup and view all the answers

Tea has the highest tannin content among beverages.

<p>True (A)</p> Signup and view all the answers

Coumarin is a type of mineral found in natural flavorings.

<p>False (B)</p> Signup and view all the answers

The phenolic substances identified include safrole and myristicin.

<p>True (A)</p> Signup and view all the answers

Milk can be contaminated with tremetone when animals ingest certain toxins.

<p>True (A)</p> Signup and view all the answers

The mortality rate from milk sickness ranges from 5% to 10%.

<p>False (B)</p> Signup and view all the answers

Algal blooms do not contribute to seafood poisoning.

<p>False (B)</p> Signup and view all the answers

Paralytic shellfish poisoning (PSP) is caused by eating shellfish contaminated with saxitoxin.

<p>True (A)</p> Signup and view all the answers

Symptoms of paralytic shellfish poisoning develop more than two hours after ingestion.

<p>False (B)</p> Signup and view all the answers

Diarrhetic shellfish poisoning (DSP) can be caused by eating mussels contaminated with okadaic acid.

<p>True (A)</p> Signup and view all the answers

Symptoms of DSP can include nausea and abdominal pain.

<p>True (A)</p> Signup and view all the answers

Natural toxins are chemicals that can have potentially toxic effects on humans due to their natural occurrence in food.

<p>True (A)</p> Signup and view all the answers

Red tide occurs due to a bloom of toxic diatoms.

<p>False (B)</p> Signup and view all the answers

Tetrodotoxin, a neurotoxin found in puffer fish, is commonly transmitted to the edible parts of the fish even with expert cleaning.

<p>False (B)</p> Signup and view all the answers

Chronic ingestion of natural toxins is often required to induce adverse effects.

<p>True (A)</p> Signup and view all the answers

Toxic phenolic substances are classified into groups based on their taste, color, and frequency of occurrence.

<p>True (A)</p> Signup and view all the answers

There are over 800 identified phenolic substances in plants, most of which are highly toxic.

<p>False (B)</p> Signup and view all the answers

Coumarin, safrole, and gossypol are examples of less toxic phenolic substances.

<p>False (B)</p> Signup and view all the answers

Endogenous toxins of plant origin can be classified based on common functional groups and physiological action.

<p>True (A)</p> Signup and view all the answers

Biogenic amines and central stimulants are forms of natural toxins that induce harmful effects immediately upon ingestion.

<p>False (B)</p> Signup and view all the answers

Cyanogenic glycosides can produce lethal doses of cyanide in humans.

<p>True (A)</p> Signup and view all the answers

Safrole is banned for food use in both the European Community and the US due to health risks.

<p>False (B)</p> Signup and view all the answers

Myristicin is primarily found in nutmeg and has been linked to potential toxicity.

<p>True (A)</p> Signup and view all the answers

American varieties of lima beans produce more cyanide than Asiatic varieties.

<p>False (B)</p> Signup and view all the answers

Cyanogenic glycosides consist of a saccharide moiety and an aglycone.

<p>True (A)</p> Signup and view all the answers

The degradation of linamarin does not produce any harmful substances.

<p>False (B)</p> Signup and view all the answers

Glycosidases and hydroxynitrile lyase enzymes are found in plant cells and become active when plant tissue is damaged.

<p>True (A)</p> Signup and view all the answers

Coumarin is harmful and does not occur in safe flavorings like lavender.

<p>False (B)</p> Signup and view all the answers

Caffeine is more potent than theophylline and theobromine.

<p>True (A)</p> Signup and view all the answers

Pyrrolizidine alkaloids can cause acute liver damage.

<p>True (A)</p> Signup and view all the answers

The primary source of caffeine in our diet is tea.

<p>False (B)</p> Signup and view all the answers

Contamination from mixing edible plants with toxic plants is a major source of natural contaminants.

<p>True (A)</p> Signup and view all the answers

Pyrrolizidine intoxication has been reported in Australia.

<p>False (B)</p> Signup and view all the answers

Consumption of meat contaminated with toxic substances from plants is very common.

<p>False (B)</p> Signup and view all the answers

Caffeine is found in cocoa beans but not in cola nuts.

<p>False (B)</p> Signup and view all the answers

The consumption of contaminated millet is linked to pyrrolizidine alkaloids.

<p>True (A)</p> Signup and view all the answers

Cassava is low in starch and is not an important food source in Africa.

<p>False (B)</p> Signup and view all the answers

The process of preparing cassava involves grating, soaking, and fermenting to reduce cyanogen content.

<p>True (A)</p> Signup and view all the answers

Consumption of dry, unfermented cassava is safe and does not affect health.

<p>False (B)</p> Signup and view all the answers

Glucosinolates are actively toxic rather than their hydrolysis products.

<p>False (B)</p> Signup and view all the answers

Isothiocyanates have been identified as non-toxic in embryonic studies involving rats.

<p>False (B)</p> Signup and view all the answers

Acetylcholinesterase inhibitors are primarily found in members of the Solanaceae family, such as potatoes.

<p>True (A)</p> Signup and view all the answers

Nitriles formed from glucosinolates are considered safe and have no known risks.

<p>False (B)</p> Signup and view all the answers

Thiocyanate is a metabolite formed from cyanide in the presence of rhodanase.

<p>True (A)</p> Signup and view all the answers

Flashcards

Natural Toxins

Chemicals found naturally in food that can have harmful effects on humans.

Tetrodotoxin

A neurotoxin found in pufferfish that can be fatal if not handled properly.

Chronic Ingestion

Regularly consuming a substance over a long period of time, which can lead to health problems.

Endogenous Toxins

Toxins naturally produced by plants.

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Toxic Phenolic Substances

A group of natural toxins found in plants, many of which contribute to the bitter taste and flavor of foods.

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Widespread Phenolic Substances

Commonly found in foods and beverages, usually present in small amounts.

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More Heterogeneous Group

A varied group of phenolic substances that are highly toxic even in small amounts.

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Gossypol

A highly toxic phenolic substance found in cottonseed.

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Flavonoids

Plant pigments that are widely present in human food. They are polyhydroxy-2-phenylbenzo-γ-pyrone derivatives, occurring as aglycones, glycosides and methyl ethers.

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Flavone

A subgroup of flavonoids, these are yellow pigments often found in citrus fruits.

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Quercetin

A flavonoid that has been shown to be carcinogenic in mammals after oral administration.

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Tannins

A diverse group of polyhydric phenols of plant origin with a molecular weight higher than 500. They are broadly distributed in plants.

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Hydrolyzable Tannins

Tannins that can be broken down by hydrolysis. They are gallic, digallic, and ellagic acid esters of glucose.

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Condensed Tannins

Tannins that are polymers of leukoanthocyanidins. They are a type of flavonoid.

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Coumarin

A naturally occurring toxin found in some flavorings. It is a chroman derivative.

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Safrole and Myristicin

Both methylenedioxyphenyl substances, these are naturally occurring toxins found in flavorings.

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Cyanogenic Glycosides

Glycosides that release cyanide when broken down by enzymes.

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Hydrolytic Enzymes

Enzymes that break down molecules using water.

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Cyanide Toxicity

Cyanide poisoning occurs when cyanide is absorbed into the body, disrupting cellular respiration.

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Lima Beans and Cassava

These plants contain cyanogenic glycosides, potentially posing a health risk if not properly processed.

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Lethal Dose of Cyanide

The amount of cyanide that can cause death varies depending on body weight, but small amounts can be lethal.

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Breeding Low-Cyanide Varieties

Scientists have developed some plant varieties with lower levels of cyanogenic glycosides.

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Saccharide Moiety

A sugar molecule that forms part of a cyanogenic glycoside.

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Aglycone

The non-sugar part of a cyanogenic glycoside, containing the cyanide-releasing group.

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Gari

A fermented cassava product where cyanogenic glycosides are reduced to safe levels. It is a common food source in parts of Africa.

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Goiter

An enlargement of the thyroid gland caused by iodine deficiency. Consuming high levels of cyanide from cassava can contribute to goiter.

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Glucosinolates

These compounds are found in cruciferous vegetables like cabbage and turnips. They are not toxic themselves but their breakdown products can be harmful.

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Isothiocyanates

Harmful breakdown products of glucosinolates. They have been linked to potential embryo toxicity in rats.

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Acetylcholinesterase Inhibitors

These compounds interfere with the breakdown of important chemicals in the nervous system. Found in various fruits and vegetables.

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Solanine

A potent inhibitor of acetylcholinesterase found in potatoes. It can be toxic if consumed in high quantities.

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Solanaceae Family

A group of plants including potatoes, eggplants, and tomatoes. These plants contain various amounts of acetylcholinesterase inhibitors.

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Methylxanthines

A group of naturally occurring compounds found in coffee, tea, and cocoa, known for their stimulating effects on the central nervous system.

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Caffeine

A methylxanthine found in coffee, tea, and other beverages. It's the primary source of caffeine in our diet, stimulating the central nervous system and potentially affecting animal growth and aging.

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Theophylline

A methylxanthine found in tea, less potent than caffeine but also stimulates the central nervous system.

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Theobromine

The primary alkaloid of cocoa beans, also present in tea and cola nuts, a methylxanthine that's relatively inactive compared to others.

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Pyrrolizidine Alkaloids

Toxic compounds produced by plants like Senecio, Crotalaria, and Heliotropium, affecting the liver and potentially causing cancer.

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Contamination of Cereals

Mixing of edible plants with toxic plants, like those producing pyrrolizidine alkaloids, resulting in contamination of cereals.

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Contamination of Meat

Contamination of meat with toxic substances of plant origin, usually occurring when animals ingest toxic plants before being consumed.

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Milk and Aquatic Organisms Contamination

Contamination of milk and aquatic organisms can originate from the feed that animals consume, potentially carrying toxins of plant origin.

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Milk Sickness

A disease caused by consuming milk contaminated with plant toxins, especially tremetone. Symptoms include weakness, abdominal pain, muscle tremors, and potentially death.

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Tremetone

A toxic compound found in certain plants, responsible for causing 'Milk Sickness' when ingested by lactating animals.

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Phycotoxins

Toxins produced by algae, particularly during algal blooms. These can contaminate seafood and cause health problems.

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Algal Bloom

A rapid increase in the population of algae in a body of water, often caused by excess nutrients. This can lead to the production of harmful toxins.

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Paralytic Shellfish Poisoning (PSP)

A type of seafood poisoning caused by consuming shellfish contaminated with saxitoxin. Symptoms include tingling, numbness, and respiratory paralysis.

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Saxitoxin

A powerful neurotoxin produced by certain types of algae, which can accumulate in shellfish and cause PSP.

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Diarrhetic Shellfish Poisoning (DSP)

A type of seafood poisoning caused by consuming shellfish contaminated with toxins like okadaic acid. Symptoms include diarrhea, nausea, and vomiting.

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Red Tide

A phenomenon caused by an algal bloom that turns the ocean water reddish-brown. These blooms often produce toxins that can harm marine life and humans.

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Study Notes

Natural Toxins

  • Natural toxins are chemicals found in food that can be harmful to humans.
  • Typically, these toxins aren't acutely toxic but can cause problems with chronic ingestion or allergic reactions.
  • Some natural toxins are more dangerous to animals and some are acutely toxic to animals too.
  • The expert cleaning of puffer fish prevents transmission of tetrodotoxin to the edible parts (tetradotoxin is a neurotoxin). However accidents still occur each year.

Natural Toxins Include

  • Endogenous toxins of plant origin
  • Contaminants of natural origin
  • Toxins of microbial origin

Endogenous Toxins of Plant Origin

  • No single method for classifying the toxic components of plants
  • Classified by functional groups: toxic phenolic substances, cyanogenic glycosides, glucosinolates
  • Classified by physiological action: acetylcholinesterase inhibitors
  • Classified by type of effect: biogenic amines and central stimulants

Toxic Phenolic Substances

  • More than 800 phenolic substances have been found in plants.
  • Many contribute to taste, flavor, and color of foods.
  • Divided into two groups based on frequency of occurrence, structural relationship, and relative toxicity

Widespread Phenolic Substances

  • Widely used in food and beverages (e.g., caffeic acid, ferulic acid, gallic acid, flavonoids)
  • Usually, not acutely toxic at the levels they're found in food.

More Heterogeneous Group of Highly Toxic Phenolic Substances

  • Coumarin, safrole, myristicin, phenolic amines (catecholamines), and gossypol.
  • These are highly toxic.

Flavonoids

  • A class of plant pigments found in human food.
  • Present as ẞ-glucosides
  • Include derivatives like aglycones , glycosides , and methyl ethers
  • Classified into six subgroups.

Flavones

  • Group of yellow pigments occurring abundantly in foods (e.g., nobiletin, tangeretin)
  • Investigated for mutagenicity.
  • Quercetin the only flavonoid shown to be carcinogenic after oral administration.

Tannins

  • Heterogeneous group of broadly distributed plant substances.
  • Includes all polyhydric phenols with molecular weights exceeding 500.
  • Two types: hydrolyzable (gallic, digallic, and ellagic acid esters of glucose) and condensed (polymers of leukoanthocyanidins)
  • Found in numerous foods (e.g., tropical fruits, tea, coffee, cocoa).
  • High concentration found in black tea – up to 450 mg/cup.

Coumarin, Safrole, and Myristicin

  • Examples of natural toxins found in various flavorings such as cassis, lavender, and lovage
  • Coumarin can be found in citrus oils and some edible fruits.
  • Safrole can cause liver tumors in rats and is prohibited in the US
  • Myristicin may contribute to the toxicity of nutmeg and can cause tachycardia, failing salivation, central nervous system excitation.

Cyanogenic Glycosides

  • Glycosides from which cyanide is formed.
  • Widely spread in plants such as lima beans and cassava
  • Lethal doses can be reached after consuming cyanogenic foods.
  • Quantities vary between Asiatic and American varieties of lima beans
  • Lower-cyanide varieties of lima beans are being bred. Beta-hydroxynitrile

Glycosidases and Hydroxynitrile Lyase

  • Present in plant cells, becoming available when the tissue is damaged.
  • Removal of cyanogenic glycosides for safer food preparation. Example, "gari," a fermented cassava preparation.

High Consumption of Dry Cassava

  • High cyanogen levels in unfermented cassava can lead to goiter.
  • Cyanide can be metabolized into thiocyanate.

Glucosinolates

  • Group of substances in cruciferous plants(e.g., cabbage, turnips) that can be antinutritive.
  • Their hydrolysis products (isothiocyanates, thiocyanate, and nitriles) are the toxic agents.
  • Isothiocyanates can be embryotoxic to rats.
  • Nitriles are precursors to nitroso compounds.

Acetylcholinesterase Inhibitors

  • Alkaloids found in various edible fruits and vegetables.
  • Includes broccoli, Valencia oranges, sugar beet, cabbage, pepper, carrot, strawberry, apple, lima bean, and radish.
  • Found in potato, eggplant, and tomato

Solanine

  • The most potent acetylcholinesterase inhibitor in potatoes.
  • Found primarily in the skin of potatoes.
  • Heat-stable and insoluble; cooking doesn't remove solanine.
  • 20mg / 100g fresh weight considered unsafe.

Chaconine and Tomatine

  • Glycoalkaloids found in potatoes, with biological properties similar to solanine.
  • Symptoms of potato poisoning are likely due to combined actions of the alkaloids.

Biogenic Amines

  • Certain amines found in plants and microorganisms.
  • Important examples in plants include dopamine, epinephrine, norepinephrine, serotonin, and tyramine.

Dietary Intake of Biogenic Amines

  • Could pose risks; especially when combined with MAO inhibitors.
  • MAO (monoamine oxidase) inhibitors block oxidative deamination.

Central Stimulants

  • Include methylxanthines (caffeine, theophylline, theobromine).
  • Found in coffee, tea, cocoa beans, and cola nuts.

Caffeine and Methylxanthines

  • Caffeine stimulates the peripheral and central nervous systems.
  • Caffeine is more potent than theophylline and theobromine.

Natural Contaminants

  • Contamination from mixing edible plants with toxic nonnutritive plants (e.g., pyrrolizidine alkaloids).
  • Contamination resulting from animal intake of toxic substances (e.g., milk sickness caused by tremetone).
  • Contamination of seafood with phycotoxins (e.g., Paralytic Shellfish Poisoning (PSP), Diarrhetic Shellfish Poisoning (DSP)).

Red Tide

  • Dinoflagellate bloom causes discoloration of the sea.
  • High toxicity of shellfish during red tide.
  • Strict regulations and awareness are important to prevent seafood contamination.

Effect of Thermal Processing on Phycotoxins

  • Cooking moderately reduces phycotoxin concentrations in mollusks.

Toxins of Microbial Origin

  • Microorganisms are ubiquitous.
  • Their absence indicates unusual or special conditions in an environment.
  • Foodborne diseases are either infections or intoxications.
  • Toxins can be produced by bacteria, fungi, algae, and the toxic metabolites such as biogenic amines and ethyl carbamate

Bacterial Toxins

  • Classified based on how they work on the human body.
  • Sub-unit toxins (e.g., Clostridium botulinum toxins)
  • Membrane-affecting toxins (e.g., Staphylococcus aureus toxins)
  • Lesion-causing toxins (e.g., Clostridium perfringens and Bacillus cereus toxins)
  • Immuno-active endotoxins (e.g., Gram-negative bacteria toxins)

Mycotoxins

  • Secondary metabolites of fungi.
  • Cause acute and chronic toxins in animals/humans.
  • Aspergillus, Penicillium, and Fusarium (examples of fungi that produce mycotoxins)
  • Environmental conditions affect mycotoxin production.

Toxic Microbial Metabolites

  • Biogenic amines (e.g., dopamine, epinephrine, norepinephrine, serotonin, and tyramine) which are produced by Enterobacteriacea and Enterococci
  • Ethyl carbamate (urethane)

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Test your knowledge of food toxicology and the effects of flavonoids in this quiz. Key topics include tannins, shellfish poisoning, and the safety of various food substances. Dive into the science behind these compounds and their implications for health and nutrition.

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