FLAVONOIDS Introduction Chem-465 12/9/201812/9/2018

What are flavonoids? Flavonoids are a group of plant metabolites thought to provide health benefits through cell signalling pathways and antioxidant effects. These molecules are found in a variety of fruits and vegetables. Flavonoids are polyphenolic molecules containing 15 carbon atoms and are soluble in water. Chem-465 12/9/201812/9/2018

Different types of flavonoids? The flavonoid family Flavones: These include luteolin and apigenin. Anthocyanidins: These include malvidin, pelargondin, peoidin and cyanidin. ... Flavonones: These include hesperetin, eriodictyol and naringenin. ... Isoflavones: This subgroup includes genistein, glycitein and daidzein. Chem-465 12/9/201812/9/2018

What are the benefits of flavonoids? Flavonoids provide a number of benefits to the human body. They: Act as antioxidants. Have a direct antitumor effect. Enhance immunity (citrus fruits). Chem-465 12/9/201812/9/2018

Flavonoids, polyphenolic compounds found in plants, have antioxidant powers that may provide important health benefits. Diets rich in flavonoids have been associated with reduced risk of a variety of diseases. However, further research is needed to determine whether flavonoids alone are responsible for these benefits rather than the whole foods that contain flavonoids. Flavonoid-rich foods include cocoa, apples, onions, cranberries, tea and red wine. Chem-465 12/9/201812/9/2018

Consist of Benzene ring (A) Pyran ring (C) Phenyl ring at position 2 of pyran ring (B) Chem-465 12/9/201812/9/2018

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What’s a phenolic compound? A secondary product that contains a phenol group - a hydroxyl functional group on an aromatic ring. OH Phenolics are a chemically diverse group: many different properties and functions. Chem-465 12/9/201812/9/2018

MEP mevalonate pathway The shikimate pathway(shikimic acid pathway) is a seven step metabolic route used by bacteria, fungi, algae, some protozoan parasites and plants for the biosynthesis of folates and aromatic amino acids (phenylalanine, tyrosine, and tryptophan). Chem-465 12/9/201812/9/2018

Biosynthesis of phenolics Shikimic acid pathway is most common in plants. Converts simple carbohydrates into aromatic amino acids. Not present in animals. PP13090.jpg Chem-465 12/9/201812/9/2018

Most plant phenolics are derived from cinnamic acid formed from phenylalanine by phenylalanine ammonia lyase (PAL) enzyme. PAL activity is inducible: fungal infection, low nutrient levels, high light PAL PP13090.jpg Chem-465 12/9/201812/9/2018

2. Lignin - 2nd most abundant compound in plants Major types of phenolics 1. Simple phenolics - e.g. coumarins 2. Lignin - 2nd most abundant compound in plants 3. Flavonoids - two aromatic rings, 2 pathways anthocyanins, flavones/flavonols 4. Condensed tannins polymerized flavonoids 5. Hydrolyzable tannins made of phenolic acids and sugars smaller molecules than condensed tannins Chem-465 12/9/201812/9/2018

1. simple phenolics Fig. 13.10 Involved in defense against insect herbivores and fungi, some may have allelopathic function. PP13101.jpg Chem-465 12/9/201812/9/2018

Simple phenolics Caffeic acid & ferulic acid implicated in allelopathy. Psoralen is one of several phototoxic furanocoumarins, (UV activated) Fig. 13.11 PP13111.jpg Chem-465 12/9/201812/9/2018

Furoanocoumarins can certain light wavelengths Furoanocoumarins can certain light wavelengths. (common in Umbelliferae family – celery, parsnip) Leaf rolling insects Insects usually roll leaves for protection from predation and to create a habitat Sometimes insects roll leaves to prevent furanocourmarins from being activated Chem-465 12/9/201812/9/2018

Furanocoumarins can bind to DNA or react with lipids and proteins Chem-465 12/9/201812/9/2018

Simple phenolics Fig. 13.11 PP13112.jpg Chem-465 12/9/201812/9/2018

Second most abundant compound in plants. 2. Lignin Second most abundant compound in plants. Highly branched polymer of phenylpropanoid groups (benzene-C3) Chem-465 12/9/201812/9/2018

often found in vessel elements, tracheids, and stems; confers structural support. Primary structural role! - Secondary role as a herbivore deterrent by reducing digestibility of plant matter also difficult for microbes to degrade; its presence slows litter decomposition. Chem-465 12/9/201812/9/2018

3. Flavonoids - basic structure is two aromatic rings joined by a 3C bridge. anthocyanins flavones flavonols isoflavonoids Fig. 13.10 PP13102.jpg Chem-465 12/9/201812/9/2018

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anthocyanins are pigments that give plant tissues Fig. 13.13 Flavonoids a) Anthocyanidins and anthocyanins are pigments that give plant tissues red, blue, and purple color. Pollinator attraction Disperser attraction PP13130.jpg Chem-465 12/9/201812/9/2018

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b & c) flavones and flavonols UV absorbing Flavonoids continued b & c) flavones and flavonols UV absorbing protection against UV (280 - 320 nm) insect pollinator attraction How we see the golden eyes… How honeybees see golden eyes… UV absorbing flavonols are present in the inner part of petals Chem-465 12/9/201812/9/2018

antimicrobial properties also involved in signalling d) Isoflavonoids common in legumes antimicrobial properties also involved in signalling e.g. attracting rhizobia Rhizobium is attracted to legumes through signaling by isoflavanoids released from roots. Chem-465 12/9/201812/9/2018

-formed by polymerization of flavonoid units -common in woody plants Tannins Condensed -formed by polymerization of flavonoid units -common in woody plants Hydrolyzable - contain phenolic acids: gallic acid, & simple sugars - smaller molecules than condensed tannins - more easily hydrolyzed and degraded Tannins reduce growth and survival of many different kinds of herbivores Also act as antioxidants - eat your isoflavonoids Johnny! Chem-465 12/9/201812/9/2018

Tannins also make protein less digestible. Many foods contains tannins (e.g. tea, red wine) and have some healthy side effects for humans (e.g. disallowing constriction of blood vessels) Tannins also make protein less digestible. Animals can sense high levels of tannins in their food and opt for another food resource (e.g. mule deer, beavers). High levels of tannins in diet can actually kill some animals. Chem-465 12/9/201812/9/2018

Condensed tannins are polymerized flavonoids. PP13151.jpg Chem-465 12/9/201812/9/2018

Hydrolyzable tannins are made of phenolics and sugars. Fig. 13.15 PP13152.jpg Chem-465 12/9/201812/9/2018

tannins can bind digestion enzymes in the gut of herbivores. The term “tannin” is derived from the tanning process in which raw animal hides are preserved by rubbing tannins on them. The tannins help to complex the proteins and keep them from degrading. This protein-binding property of tannins lends them their toxicity to herbivores. tannins can bind digestion enzymes in the gut of herbivores. tannins also form complex polymers when bound to proteins which are difficult to digest, thus decreasing the nutritional value of the plant material. Chem-465 12/9/201812/9/2018

Care for a spot of milk in your tea? Tannins can reduce nutritional value of tissues by binding to proteins, making them less digestible. PP13161.jpg Fig. 13.16 Care for a spot of milk in your tea? Chem-465 12/9/201812/9/2018

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Creosote bush, Larrea tridentata Leaves are 10-25% phenolic resin. 40% of resin is NDGA (nordihydroguaiaretic acid), remainder is o-methylated flavones and flavonols. Deters insect herbivory. Mammalian herbivores select older leaves (less resin). Chem-465 12/9/201812/9/2018

Active compounds in creosote leaves. · NDGA and similar compounds. · Amino acids. · Flavonoids. · Volatile oils. · Triterpenes. · Saponins. USDA formerly used NDGA as an antioxidant to prevent rancidity in food. Now known to cause liver and kidney disease in lab animals. Creosote has long been used in traditional Native American and Mexican herbal medicine Chem-465 12/9/201812/9/2018

Creosote applications in herbal therapy · To dissolve urinary kidney stones. · Anti inflammatory for respiratory ailments (asthma) and arthritis · To eliminate gallstones · Against urinary infections · For the treatment of venereal disease · As an abortifacient · Against diabetes · Bronchitis and colds · Rheumatism · Against some types of cancer · As a mouthwash against tooth decay and halitosis Chem-465 12/9/201812/9/2018

Lignin/Nitrogen ratio After life effects of phenolic compounds. Plant litter decomposition, and release of nutrients from decomposing litter, are strongly influenced by the chemical composition of the litter. Litter higher in tannins and lignin decomposes more slowly. Decomposition rate Lignin/Nitrogen ratio Chem-465 12/9/201812/9/2018

Bill Shakespeare, secondary chemist 12/9/201812/9/2018