Definition of secondary (2o) products/metabolism:-not essential & not found in all plants-primary functions of 2o 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 2o cmpds

Plant Secondary Metabolism(aka, natural products chemistry)

-three major categories of 2o 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)-2o 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)

(3) N-containing cmpds:

-many different kinds

-examples:-alkaloids (N-containing ring, often basic)-glycosides

-mustard glycosides-cyanogenic glycosides

-non-protein amino acids & oligopeptides (e.g., defensins, thionins)-proteins; e.g., proteinase inhibitors, lectins ((CH2O)n-binding

proteins, a.k.a. agglutinins), cytochrome P450 monooxygenases, etc.

Stimulating beverages

Coffee, tea, cocoa

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.• 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 methodBrewed, percolatorInstantDecaffeinatedEspresso (30ml cup)

11580653

40

Teas (150ml cup)Brewed, major brandsInstantIced (240ml glass)

403045

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 stimulantsAlkaloid: methylxanthines

Compound Source effect

Caffeine Coffee, tea, cola nuts

Stimulant of central nervous system, cardiac muscle, and respiratory system, diuretic

Theophylline Tea Cardiac stimulant, smooth muscle relaxant, diuretic, vasodilator

Theobromine

cocoa 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 Tea.  Mary Cassatt, 1880, oil on canvas. American.  

Impressionist.

The 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

http://www.charlestonteagardens.com/

Charleston, SC Tea Plantation

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

Chocolate

The “Food of the Gods”?

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.

Processing of Chocolatehttp://www.fmnh.org/Chocolate/manufacture_interactive/manufacture.html

• Growth

• Harvest

• Ferment

• Dry

• Ship

• Roast

• Crack, fan, winnow

• Grind

• Mix

• Refine

• Conch

• Temper

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.

http://www.hersheys.com/discover/chocolate.asp

Chocolate factory tours

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.