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1 PP13040.jpg


3 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.

4 Biosynthesis of phenolics
Shikimic acid pathway is most common in plants. Converts simple carbohydrates into aromatic amino acids. Not present in animals. PP13090.jpg

5 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

6 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

7 1. simple phenolics Fig. 13.10 Involved in defense against
insect herbivores and fungi, some may have allelopathic function. PP13101.jpg

8 Simple phenolics Caffeic acid & ferulic acid implicated in
allelopathy. Psoralen is one of several phototoxic furanocoumarins, (UV activated) Fig PP13111.jpg

9 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

10 Furanocoumarins can bind to DNA or react with lipids and proteins

11 Simple phenolics Fig PP13112.jpg

12 2. Lignin Second most abundant compound in plants. Highly branched polymer of phenylpropanoid groups (benzene-C3)

13 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.

14 3. Flavonoids - basic structure is two aromatic
rings joined by a 3C bridge. anthocyanins flavones flavonols isoflavonoids Fig PP13102.jpg


16 anthocyanins are pigments that give plant tissues
Fig Flavonoids a) Anthocyanidins and anthocyanins are pigments that give plant tissues red, blue, and purple color. Pollinator attraction Disperser attraction PP13130.jpg


18 Flavonoids continued b & c) flavones and flavonols UV absorbing protection against UV ( 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

19 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.

20 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!

21 Many foods contains tannins (e. g
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.

22 Condensed tannins are polymerized flavonoids.

23 Hydrolyzable tannins are made of phenolics and sugars.
Fig PP13152.jpg

24 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.

25 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 Care for a spot of milk in your tea?


27 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).

28 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

29 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

30 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

31 Bill Shakespeare, secondary chemist

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