natural products pdf

Question 1

what are cloves?

Answer 1

Cloves are dried unopened buds of the clove tree (Syzygium aromaticum) used as a spice.
Most of the cloves used in the United States are obtained from Zanzibar. These cloves are also the source of clove oil, which is used as a flavouring agent, as an ingredient of certain perfumes, and as a
medicine.

Question 2

what is eugenol?

Answer 2

Eugenol is the primary component of this essential oil that gives cloves their unique taste and odour.
The second major component is reported to be acetyl eugenol. Eugenol and related structures are classified as propylbenzene derivatives.

Question 3

in addition to eugenol and acetyl eugenol, trace amounts of —————- is also present in clove?

Answer 3

methyl n-pentyl ketone, methyl salicylate, and the terpene, carophyllene are also present.

Question 4

how are the the essential oil from cloves isolated?

and what is it composed of?

Answer 4

The essential oil from cloves is isolated by steam distillation. The oil is composed of a diverse range of compounds including terpenes, and isopropylbenzene and propylbenzene derivatives.

Question 5

what is the process of steam distillation?

Answer 5

Steam distillation – The plant material, suspended in a basket, is treated with steam. The oil is recovered at a lower temperature (< 100 oC) than its boiling point (usually in excess of 200 oC) by this method. Can only be used where significant amounts of oil are present and if the oil is not easily oxidised/hydrolysed. (See handout on Moodle for diagram of apparatus and collecting vessels for oils lighter and heavier than water.)

Question 6

Eugenol is expected to be soluble

in ___________

Answer 6

suitable organic solvents and may be removed by extraction.

Question 7

what is the METHOD FOR ISOLATION OF EUGENOL FROM CLOVE OIL

Answer 7

Weigh accurately approximately 2.0 g of clove oil in a sample vial. Dissolve the clove oil in aliquots of diethyl
ether (total 60cm3) and transfer to a separating funnel.

Extract the diethyl ether solution with three separate
20 cm3 portions of 5% NaOH (dilute the bench solution approx.). Save the ether solution that remains. A mass
spectral-gas chromatogram of the ether solution has been recorded for your analysis (LEE3.D).
Acidify the combined sodium hydroxide extracts with 6M HCl until blue litmus turns red. Extract the acidified
solution with three separate 20cm3 portions of dichloromethane. Combine the extracts and dry with
anhydrous sodium sulphate. Filter into a pre-weighed conical flask (100cm3
) and carefully evaporate the
solvent on a steam bath (place boiling stick in it) until there is no more evaporation taking place. Continue
heating for another 10 -15 minutes.
Determine the weight of final oil. Calculate the percentage (w/w) of eugenol in the clove oil provided.