ISOLATION OF CAFFEINE FROM TEA LEAVES

Botanical: Camellia thea

Synonyms---Thea sinensis (Sims). Thea veridis. Thea bohea. Thea stricta Jassamica. Camellia theifera (Griff.).

http://www.botanical.com/botanical/mgmh/t/tea---08.html$$

---Constituents---Caffeine (theine), tannin (10 to 20 per cent gallotannic acid), boheic acid, volatile oil, aqueous extract, protein wax, resin, ash and theophylline.

Green tea, black tea, and oolong tea are all derived from the same plant. http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-black_tea.html

White teas? These are less processed tea and contain more antioxidants than black teas and oolongs, which fall midway between green and black teas.

TIME December 3, 2007 p 41 “India Brews A Stronger Cup”

Black tea is a source of caffeine, a methylxanthine

It stimulates the central nervous system, relaxes smooth muscle in the airways to the lungs (bronchioles), stimulates the heart,and acts on the kidney as a diuretic (increasing urine).

N

N N

N

O

O

H3C

CH3

CH3

1,3,7-trimethyl-2,6-dioxopurine

Green Tea: Chinese Tea, Unfermented Tea, Sencha

Active Ingredients:1.Polyphenols (Catechins) (10-25%): epigallocatechin-3-gallate, epicatechin, epicatechin-3-gallate, epigallocatechin2.Purine Alkaloids (Methyl Xanthines): caffeine((2.9-4.2%)3.Inorganic Ions: fluoride (130-160 mg/kg), potassium, aluminum4.Other Ingredients: flavonoids, caffeic acid derivatives, triterpene saponins, volatile oils

Oolong Tea, the tea that represents China, is produced in the province of Fujian. The tea consists of several kinds of leaves that goes through different production processes giving different flavours and aromas.

http://www.oolongtea.org/e/welcome/04.html

Caffeine is not only in coffee, tea, cola, even in chocolates!Caffeine-infused gum, lip balm, mints, beer, candy, sunflower seeds, even soap!

How does it work?

Caffeine crosses the blood-brain barrier, dampening neurotransmitters that would normally make you sleepy, improving temporarily, cognitive function and even athletic performance.

A typical cup of coffee has 80 to 150mg caffeine;Softdrinks have 34 mg to 50 mg per can;Energy drinks may pack from 75 mg to 300 mg per serving.

TIME October 1, 2007 p.38 “The Caffeine Habit”

One cup of tea contains approximately 50 milligrams of caffeine, depending on the strength and size of cup (as compared to coffee which contains 65 to 175 milligrams of caffeine per cup).

Tea also contains polyphenols (catechins, anthocyanins, phenolic acids), tannin, trace elements, and vitamins.

Caffeine is a stimulant of the central nervous system, and may cause insomnia in adults, children, and infants (including nursing infants of mothers taking caffeine). Caffeine acts on the kidneys as a diuretic (increasing urine and urine sodium/potassium levels, and potentially decreasing blood sodium/potassium levels), and may worsen urge incontinence. Caffeine-containing beverages may increase the production of stomach acid, and may worsen ulcer symptoms. Tannin in tea can cause constipation. Caffeine in doses of 250 to 350 milligrams can increase heart rate and blood pressure, although people who consume caffeine regularly do not seem to experience these effects in the long-term. http://www.mayoclinic.com/health/green-tea/NS_patient-green_tea

TECHNIQUES

1. Extraction1.1 Solid-Liquid Extraction1.2 Liquid-Liquid Extractiono Single Extractiono Multiple Extraction

2. Sublimation/Recrystallization3. Characterization by Melting Point Determination

SOLID-LIQUID EXTRACTION

Solvents for extraction:1. Non-toxic2. Easily removed3. Desired constituent is soluble4. Non-reactive

Extract with Na2CO3 in

BOILING WATER

MARC HOT WATER EXTRACTNa-Tannate Extract is BROWN in color due to flavonoids, tannins and its oxidation products.

EXTRACTION – the removal of a desired compound from a solid or liquid mixture by a solvent.

- transferring a solute from one solvent to another Types:

SOLID-LIQUID EXTRACTIONLIQUID-LIQUID EXTRACTION

http://naturalhealthcare.ca/medical_terms.phtml?term=decoction. Taken 02 Dec 2007

SOLID-LIQUID EXTRACTION

DECOCTION – the act or process of boiling anything in a watery fluid to extract its virtues; an extract from a body by boiling it in water

http://www.epicurious.com/tools/fooddictionary/entry?id=3033. Taken 02 Dec 2007

INFUSION – is the flavour that’s extracted from an ingredient such as tea leaves, herbs or fruit by steeping (soaking) them in a liquid (usually hot), such as water, for tea.

CONTINUOUS EXTRACTION PROCESS

BATCH EXTRACTION PROCESS

Most frequently used.Separation of a neutral organic compound in an aqueous medium, by shaking with an organic solvent in which the compound is soluble but is immiscible with water.

Used when the organic compound is more soluble in water than in the organic solvent

Tea Leaves 1CELLULOSE, 2CAFFEINE, 3TANNINS

1 Glucose polymer, not soluble in water

1CELLULOSE

2 Alkaloid compound; soluble in water but more soluble in dichloromethane (DCM, CH2Cl2)

N

N N

N

O

O

H3C

CH3

CH3

2CAFFEINE

3 Phenolic compounds; all are potentially soluble in water and some are hydrolyzed in water.

3TANNINS

TANNINS – refers to a class of compounds which are PHENOLICS hydrolyzable tannins found in tea generally yield glucose

and gallic acid

O

OR

H

RO

H

RO

H

RO

CH2O C

O

OHOH

O C

OOH

OH

OH

ESTER OF GALLIC ACID AND GLUCOSE

H

undergo hydrolysis in water

O

H

OR

H

RO

H

RO

H

RO

CH2OH

OHOH

OHHOOC

+

Non-hydrolyzable tannins are condensation polymers of catechins; these polymers are not uniform in structures

OHO

OH

OH

OHOH

catechin

Overview

• Tannins that are hydrolyzed when mixed with H2O produce glucose + gallic acid.

• Adding Na2CO3 makes the acidic solution basic & converts tannins & gallic acid to H2O-soluble sodium salts.

• This opens the door for a separation of caffeine from the other components via extraction by adding CH2Cl2 to the aqueous solution.

• Crude caffeine can then be isolated by evaporating off the CH2Cl2 solvent and further purified by sublimation or crystallization.

Na2CO3

Hot WATER EXTRACT

CoolExtract with 20 mL dichloromethane ( 3x)

AQUEOUS EXTRACT DCM EXTRACT ( Organic)

LIQUID-LIQUID EXTRACTION

Choice of solvent for liquid-liquid extraction:1. Solvent must be able to dissolve compound of interest2. Solvent must not be very soluble in water3. Solvent must be low boiling so that it can be easily

removed by distillation or evaporation4. Solvent must have a density that is different from water

LIQUID-LIQUID EXTRACTION – is use for separation of complex mixtures by selective partitioning between two phases, between two immiscible liquids.

Extraction are carried out in two immiscible solvents, usually one aqueous andone organic.

AQUEOUS EXTRACT DCM EXTRACT

Hydolyzable tannins Caffeine

Non-hydrolyzable tannins Chlorophylls

Sugars, minerals, acids Some flavonoids,waxes

Sodium salts of tannins Condensed tannins (non-hydrolyzable)

DCM EXTRACT

Wash with 6M NaOH

AQUEOUS EXTRACT DCM EXTRACT

DISTRIBUTION COEFFICIENT (Partition Coefficient)

Ratio of the concentrations of the solute in each

solvent at a particular temperature is constant

It is independent of the total concentration and the actual amounts of the two solvents mixed.

K = concentration in solvent 2

concentration in solvent 1

It is ALWAYS better to use several small amounts of the second solvent than to make a single extraction with a large portion.

For example a compound A is soluble in diethylether to the extent of 20g/100mL at 200C and soluble in water to the extent of 5.0g/100mL at the same temperature.

What is the distribution coefficient of compound A?

We will calculate how much compound will be extracted by single extraction.

If for example we have a solution containing 5.0 g of compound A in 100 mL water. If we shake this with 100 mL diethylether, how much a will be extracted by the ether? Concentration of A in diethyl ether = X gms

100mLConcentration of A in water = (5.0 – X) gms 100 mL

Substitution,

K = concentration in diethyl ether concentration in water X= Because a solute distributes itself between two solvent, a single extraction may not be very efficient.

The 100 mL of ether maybe divided into three portions of approximately 33 mL each.

X after three extractions =

EMULSION

A colloidal suspension of one liquid in another caused by vigorous shaking.

How to breakup emulsions?

(1) if one of the solvents is water, adding a saturated aqueoussodium chloride solution

(2) gentle swirling of the liquid in the flask and gentle stirring

MELTING POINT DETERMINATION

MELTING POINT is the temperature at which solid changes to liquidAt 1 atmosphere of pressure.

MELTING RANGE, the melting point of a solid is reported in range

Effect of Impurities

a PURE ORGANIC COMPOUND usually has a SHARP melting point SHARP MELTING POINT melts within a range of 1-2o

an IMPURE ORGANIC COMPOUND exhibits a broader range and depressed melting point from that of pure compound

OTHER MELTING POINT BEHAVIORS:

1.Decomposition – observed as darkening. All organic compounds decompose when heated at sufficient temperature.

2. Polymorphs – different crystalline forms of the same compound causes different intermolecular attractions.

3.Hydrates – some compounds can crystallize with water or other solvents in their crystal lattice in a definite proportion by weight. Hydrates would have different temperatures from anhydrous.

4.Racemic Mixtures – a pair of nonsuperposable mirror image isomers called enantiomers would behave like a pure compound.

5.Liquid Crystals – intermediate between solid phase and liquid phase formed by heat causes some pure compounds not to exhibit sharp melting point