Presentation on theme: "Definition of secondary (2 o ) products/metabolism: -not essential & not found in all plants -primary functions of 2 o products- -defense against herbivores."— Presentation transcript:
Definition of secondary (2 o ) products/metabolism: -not essential & not found in all plants -primary functions of 2 o products- -defense against herbivores & pathogens -attraction of pollinator & seed/fruit dispersers (through scent, sight, and taste) -important to humans in medicine, industry, food & agriculture -most crop plants have been selected to make low levels of 2 o cmpds Plant Secondary Metabolism (aka, natural products chemistry)
-three major categories of 2 o cmpds 1)Isoprenoids (or terpenes) 2) Phenolics 3)Nitrogen-containing compounds
(1) terpenes (aka, isoprenoids): -largest category -built from 2C (acetyl CoA) & 5C (isoprene) compounds -isoprene subunits used to build larger molecules -some terpenes are primary metabolites (e.g., pigments, hormones) -2 o cmpds often localized to trichomes or resin ducts -examples: -monoterpenes (10C)- pyrethroids & oils (e.g., pine oil, lemon oil, menthol) -sesquiterpenes (15C)- gossypol -diterpenes (20C)- resins (e.g., in pines and euphorbs) -triterpenes (30C)- phytoecdysones (insect molting hormones), limonoids (in citrus rind), cardenolides (glycosidic triterpenes; e.g., digitalis & those in milkweeds) -polyterpenes (>40C)- natural rubber & latex
(2) phenolics: -produced via shikimic acid pathway in plants, fungi, & bacteria, but not in animals (which is why animals can't make tryptophan, phenylalanine, & tyrosine) -examples: -lignin (complex polymer built mostly from 3 kinds of phenolic-alchohol subunits) -flavonoids: -anthocyanins (pigments) -flavonols (eg, UV-absorbing cmpds found in flowers, UV-screening cmpds found in epidermal cells; these cmpds don't absorb 400-to- 700-nm light) -isoflavonoids (e.g., phytoalexins...anti-microbial cmpds) -tannins (several different categories...big and small; general toxins) -others (e.g., salicylic acid & coumarins) -others (e.g., salicyclic acid, coumarins)
History of coffee Native to E. Africa; used first in Ethiopia. Arabs were first to brew coffee (ca. 1300 AD) and use spread from Arabia to Egypt and then to Europe (ca. 1600). –Arabic origin: mocha, kava, coffee Coffee was particularly popular in England. Arabs monopolized trade by boiling seeds to kill them, but Dutch and French were able to obtain seeds and grow the trees themselves. Brazil and Columbia currently lead the world in coffee production. Second to oil, coffee is the most widely traded commodity.
Rust epidemic in coffee In 1868, Ceylon was the leading coffee producer (export of 100 million lbs); by 1890, no coffee could be exported leaf disease caused by a fungus, Hemileia vastatrix Java 1876; East Africa 1894; Brazil 1970 made worse by limited diversity; highly variable pathogen controlled by fungicides --> uneconomical in many regions, except where optimal climate genetic resistance: C. canephora (Robusta); lower quality used in cheap blends and instant coffee replace by other crops: e.g., tea
Views of coffee change through history hailed as a medicinal cure-all others condemned it as the devil's brew –usually for political or religious reasons mid 1900’s: research discovered caffeine & its relation to human health –in moderation, coffee consumption is usually not a health risk –can indeed confer some health benefits
Botanically Small evergreen tree or shrub with shiny, simple leaves. Traditionally a ‘shade’ tree. Fruit = berry (“cherry”). Each fruit contains 2 seeds = beans, mostly endosperm.mostly endosperm Coffee is best grown in tropical and subtropical high-land cool climates, with fertile soils and 60-100" rainfall, but requires dry season for flower development. Frost sensitive. Trees begin producing at 3 years and produce for 40 years.
Coffee species (of ca. 60 in genus) Coffea arabica - 90% of world's production –Only kind grown in Latin America, ca. 1% caffeine (on DW basis), milder than other species C. canephora -9% - Robusta coffee –Grown in Africa & Asia C. liberica - 1% - Liberian coffee –Grown in Africa The last two are hardier plants than C. arabica, and C. canephora produces more fruits, but C. arabica still predominates. C. arabica is a self-compatible polyploid, other are self-incompatibile diploids with a more bitter flavor.
Processing coffee Seeds are separated from fruit, fermented and roasted Light roast-to-Dark Roasts (stronger flavor due to roasting at higher temperature; beans are oily-appearing because high temperature brings oils to surface). Most coffees sold in U.S. are light- and medium- roasted.
Famous coffee types Light roast –Pronounced nut-like flavor, high coffee acidity Medium roast –Pronounced caramel like flavor, full coffee flavor, with some loss of acidity Full roast –Full coffee flavor, good balance of acidity and sugar Vienna –Dark roast flavor French Roast –Bitter, smoky taste and pungent aroma Espresso Dark –Burnt flavor that is strong and sweet Kona Coffee –the only coffee found in the Hawaiian Islands –Full coffee flavor, balance of acidity and sugar
Coffee preparation Expresso –Pressurized hot water quickly forced through finely, ground & densely packed, dark roasted arabica beans Latte –Expresso with steamed milk Mocha –Latte with less steamed milk, but with chocolate syrup added Cappuccino –Expresso with less steamed milk than a latte, but with large cap of foamed milk
Secondary processing Instant coffee –ground beans brewed under pressure, dehydrate brew by freezing or spraying Decaffeination –before roasting, when beans are still 'green', –removing about 97-98% –Solvent - methylene chloride or ethyl acetate is used to remove caffeine, solvent is removed (hopefully) during roasting. Caffeine is removed from solvent with water and crystallized. –Water - green beans are percolated with water that contains all water-soluble compounds found in coffee with exception of caffeine, which diffuses out; more expensive than solvent extraction.
caffeine Chemical name, 1,3,7-trimethylxanthine; an alkaloid dimethylxanthine derivatives, theophylline and theobromine, are also found in a variety of plants occurs naturally in the leaves, seeds, or fruit of more than 60 plant species; coffee beans are ca. 1-2% caffeine by weight discourages grazing animals 75% of purified caffeine (2 million pounds) is used in soft drinks, rest in headache and cold medicines
Caffeine continued readily absorbed into the blood and body tissues half-life of approximately four hours (1-10) rapidly metabolized and excreted smokers break down caffeine more quickly than non-smokers contraceptive pill & pregnancy slow the rate of caffeine metabolism
Stimulant Effects range from mild alertness to heightened anxiety and body tension. Medically, caffeine is useful as a cardiac stimulant, and also as a mild diuretic. Recreationally, it is used to provide a "boost of energy" or a feeling of heightened alertness. Temporary increase in the metabolic rate and the rate of fat breakdown (lipolysis).
Diuretic minor diuretic under normal consumption beverages containing caffeine should not be used to promote fluid replacement during prolonged exercise
Habituation Caffeine's effects are more mild than amphetamines, cocaine, and heroin, but it is manipulating many of the same channels. Some regular users who stop consuming caffeine may experience withdrawal symptoms, including: drowsiness, headaches, irritability, nausea and vomiting, and depression.
Amounts of caffeine per item (mg)Typical Coffee (150ml cup) Brewed, drip method Brewed, percolator Instant Decaffeinated Espresso (30ml cup) 115 80 65 3 40 Teas (150ml cup) Brewed, major brands Instant Iced (240ml glass) 40 30 45 Some soft drinks e.g. cola (180ml)18 Chocolate milk beverage (240ml)5 Milk Chocolate (30g)6 Dark chocolate, semi-sweet (30g)20 Cooking chocolate (30g)26
Caffeine & related stimulants Alkaloid: methylxanthines CompoundSourceeffect Caffeine Coffee, tea, cola nuts Stimulant of central nervous system, cardiac muscle, and respiratory system, diuretic TheophyllineTeaCardiac stimulant, smooth muscle relaxant, diuretic, vasodilator Theobrominecocoa bean, cola nuts & tea Diuretic, smooth muscle relaxant, cardiac stimulant, vasodilator
printed labels from a Japanese Tea Box ( antique mall in Grand Island, Nebraska)
The Cup of TeaThe Cup of Tea. Mary Cassatt, 1880, oil on canvas. American. Impressionist.
The Tea CupThe Tea Cup. Jackson Pollock, 1946, oil on canvas. American. Abstract Expressionist
Tea World’s most popular beverage, next to water –Every day, 800 million cups or glasses of tea are consumed globally. Camellia sinensis - native to China/India/Tibet/Burma area; cultivation and use of tea originated in Asia (China or India, probably 4-5000 years ago). Portuguese & Dutch introduced tea to Europe inca. 1600; tea was important trade item in Europe by 1700. Colonial Americans were fond of tea and were angered by tea tax imposed by British, which resulted in the Boston Tea Party.
Botanically Cultivation: has not been grown very successfully in New World, except Argentina: most tea is grown in Asia. Plants are small evergreen trees, which prefer abundant rainfall and warm-to-cool temperatures (but no frost). Trees are pruned to force bush-like growth. Picking is by hand, youngest leaves and terminal bud only are picked; plants can be picked once a week. Tips are orange pekoe; larger leaves are souchong and pekoe. Tea bags were initially used as samples.
Fermentation & additives affects color, flavor and aroma Non-fermented: e.g., Green Tea, Lungching (Dragonwell), Pilochun, Chencha Semi-fermented: Oolong Light: Chinchua, White tea + Flowers: Jasmine tea + Bergamot oil: Earl Gray Fully-fermented: Black or ‘red’ tea –95% of tea consumed in US
Essential oils and tannins Essential oil: theol Tannin –Discourage herbivores –Used as stains, dyes, inks, tanning agents
Benefits of drinking tea? Improving immune system and preventing cancers Slowing down aging process Preventing loss of bone calcium Alleviating blood lipoid, cholesterol, blood pressure, and arteriosclerosis Helping sterilization and reinforcing teeth and intestine Reducing urine hyperacidity and gout Eliminate body fat Preventing sunburn and resisting UV
Some other plants used for “tea” Sassafras albidum - aromatic bark used to make medicinal tea; may be carcinogenic. Herb teas - made from a huge variety of fragrant plants (chamomile, chicory, etc.) Ginseng - Panax quinquefolium - use roots roots to make tea, straight tea does not taste very good so is usually used with honey or herb tea. Thought to have many positive affects, especially by Asians. Ephedra species – “Mormon” tea
Cacao Theobroma cacao - chocolate and cacao New World origin in eastern Andes, "Food of the Gods" to Mayans, Mayan drink included cacao, red pepper, vanilla and other spices. Sweet hot chocolate became very popular in Europe by 1650 (introduced ca. 1500). Spanish, then Dutch, then Germans, became involved in establishment of cacao plantations. W. Africa and Brazil are now world's largest producers.
Botanically Cacoa plants are small trees grown in shade, in warm wet tropical climates. The pods contain 20-50 seeds, are broken open and cleaned by hand. Seeds are fermented, which changes their white color to purple. Seeds are very bitter at this point. Seeds are then roasted, cracked to remove seed coats to yield nibs (cotyledons), nibs are ground, making enough heat to melt fat and produce chocolate liquor which can be molded into baking chocolate.
Processing Cocoa is made by pressing out fat (cocoa butter), dry powder is treated with alkali to produce Dutch cocoa. Milk chocolate is produced by continuous stirring of a mixture of chocolate liquor + cocoa butter + sugar + condensed milk.
What chemicals does chocolate contain? Caffeine and theobromine are both considered alkaloids (or methylxanthines). Phenylethylamine is an anti-depressive and anti-stress agent. Serotonin is a hormone which is also produced naturally by the brain. Various flavonoids
different types of chocolate Unsweetened or Baking : –chocolate liquor that has been cooled and hardened. Dark or Bittersweet Chocolate: –must contain a minimum of 34 percent cacao solids. Semi-sweet Chocolate –chocolate with extra cocoa butter and sugar added. German Chocolate: –sweeter and richer than semi-sweet chocolate, and is a special blend of chocolate, sugar and cocoa butter. Milk –creamy sweet chocolate that has extra cocoa butter, sugar, milk, and vanilla.
Cocoa –chocolate liquor with the cocoa butter having been removed, creating a fine bitter tasting powder. Dutch Process Cocoa –special process used to neutralize the natural acids in cocoa powder. White chocolate: –cocoa butter without the cocoa, and is therefore not considered chocolate. –cheap imitations that substitute vegetable oil for cocoa butter. Decorator’s or Confectioner’s Chocolate –a chocolate flavored candy.
Other beverages: Coca-Cola Kola tree- Cola nitida - relative of cacao; native to W. Africa. original Coca Cola had seeds cleaned and allowed to ferment, then dried and pulverized to a powder. seeds contain caffeine and kolanin (heart stimulant) and appetite suppressant. Since 1903, the cocaine has been removed before the coca extracts are added.
Other beverages, cont. Root beer - carbonated, sweetened beverage flavored by extracts (caramel, sarsaparilla, wintergreen). Teas (e.g., mate) made from various species with caffeine (e.g., Ilex species) are common in S. & C. America.