3What’s a phenolic compound? A secondary product that contains a phenol group- a hydroxyl functional group on an aromatic ring.OHPhenolics are a chemically diverse group: manydifferent properties and functions.
4Biosynthesis of phenolics Shikimic acid pathway is most common in plants. Converts simple carbohydrates into aromatic amino acids. Not present in animals.PP13090.jpg
5Most 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 lightPALPP13090.jpg
6Major types of phenolics 1. Simple phenolics - e.g. coumarins2. Lignin - 2nd most abundant compound in plants3. Flavonoids - two aromatic rings, 2 pathwaysanthocyanins, flavones/flavonols4. Condensed tanninspolymerized flavonoids5. Hydrolyzable tanninsmade of phenolic acids and sugarssmaller molecules than condensed tannins
71. simple phenolics Fig. 13.10 Involved in defense against insect herbivoresand fungi, some mayhave allelopathicfunction.PP13101.jpg
8Simple phenolics Caffeic acid & ferulic acid implicated in allelopathy.Psoralen is oneof severalphototoxicfuranocoumarins,(UV activated)FigPP13111.jpg
9Furoanocoumarins can certain light wavelengths Furoanocoumarins can certain light wavelengths. (common in Umbelliferae family – celery, parsnip)Leaf rolling insectsInsects usually roll leaves for protection from predation and to create a habitatSometimes insects roll leaves to prevent furanocourmarins from being activated
10Furanocoumarins can bind to DNA or react with lipids and proteins
122. LigninSecond most abundant compound in plants.Highly branched polymer of phenylpropanoid groups (benzene-C3)
13often found in vessel elements, tracheids, and stems; confers structural support. Primary structural role!- Secondary role as a herbivore deterrent by reducing digestibility of plant matteralso difficult for microbes to degrade; its presence slows litter decomposition.
143. Flavonoids - basic structure is two aromatic rings joined by a 3C bridge.anthocyaninsflavonesflavonolsisoflavonoidsFigPP13102.jpg
16anthocyanins are pigments that give plant tissues FigFlavonoidsa) Anthocyanidins andanthocyanins are pigmentsthat give plant tissuesred, blue, and purplecolor.Pollinator attractionDisperser attractionPP13130.jpg
18Flavonoids continuedb & c) flavones and flavonolsUV absorbingprotection against UV ( nm)insect pollinator attractionHow we see the golden eyes…How honeybees see golden eyes…UV absorbing flavonols are present in the inner part of petals
19d) Isoflavonoidscommon in legumesantimicrobial propertiesalso involved in signallinge.g. attracting rhizobiaRhizobium is attracted to legumes through signaling by isoflavanoids released from roots.
20TanninsCondensed-formed by polymerization of flavonoid units-common in woody plantsHydrolyzable- contain phenolic acids: gallic acid, & simple sugars- smaller molecules than condensed tannins- more easily hydrolyzed and degradedTannins reduce growth and survival of many different kinds of herbivoresAlso act as antioxidants - eat your isoflavonoids Johnny!
21Many 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.
22Condensed tannins are polymerized flavonoids. PP13151.jpg
23Hydrolyzable tannins are made of phenolics and sugars. FigPP13152.jpg
24The 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.
25Care for a spot of milk in your tea? Tannins can reduce nutritional value of tissues by binding to proteins, making them less digestible.PP13161.jpgFigCare for a spot of milk in your tea?
27Creosote 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 herbivoresselect older leaves (less resin).
28Active 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 Mexicanherbal medicine
29Creosote 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
30After life effects of phenolic compounds. Plant litter decomposition, and release of nutrientsfrom decomposing litter, are strongly influenced bythe chemical composition of the litter.Litter higher in tannins and lignin decomposes more slowly.DecompositionrateLignin/Nitrogen ratio