Sesquiterpenes

Farnesane

2,6,10-Trimethyldodecane or farnesane, the parent compound of about 10 000 sesquiterpenes known to date.

The (E,E)-isomer of a-farnesene is a component of the flavors and natural coatings of apples, pears and other fruits. Associated with (E)-b-farnesene, it also occurs in several ethereal oils, for example those of camomile, citrus, and hops.

Chamomile

Aldehydes such as a- and b- sinensal derived from a- and b-farnesene contribute to the flavor of the oil of orange expressed from the fresh peel of ripe fruits of Citrus sinensis (Rutaceae); mandarin peel oil from Citrus reticulata and C. aurantium (Rutaceae) contains 0.2% of a-sinensal with the smell of oranges.

(S)-(+)-Nerolidol in the oil of neroli ( البرتقال (زهرobtained from orange flowers and found in many other flowers is used in perfumery, similar to farnesol from Acacia farnensiana (Mimosaceae) and the oils of bergamot, hibiscus, jasmine and rose, and pleasantly smelling blossoms such as lily of the valley.

Actinodaphne longifolia

Acacia farnensianaالسنط

Lily of the valley الوادي زنبق او المضعف

Monocyclic Farnesane Sesquiterpenes

Cyclofarnesanes and BisabolanesCyclofarnesanes formally arise when carbon

atoms C-6 and C-7 of farnesane close a ring. Abscisic acid, occurring in the leaves of cabbage, potatoes, roses, and young fruits of cotton. Abscisic acid acts as an antagonist of plant growth hormones and controls flowering, falling of fruits and shedding of leaves.

(+)-dihydroxy-g-ionylidene acetic acid are produced by the fungus Cercospora cruenta which is antibacterially active

Formally, C-1 and C-6 of farnesane close a cyclohexane ring in the bisabolanes, which represent a more prominent class of monocyclic sesquiterpenes. Additional cyclizations increase the diversity. More than 100 bisabolane derivatives of plant origin are known to date

Oil of ginger obtained from the rhizome of Zingiber officinalis (Zingiberaceae) consists predominantly of (-)-zingiberene (20-40%), b-sesquiphellandrene and (+)- - b bisabolene

Ginger rhizome

b-bisabolene also occurs in Chamaecyparis nootkatensis (Cupressaceae) and in the Sibirian pine tree Pinus sibirica (Pinaceae)

(+)-a- and (+)-b-bisabolol are fragrant sesquiterpenes found in the essential oils of various plants; they also contribute to the odors of camomile and of bergamot oil from unripe fruits of Citrus aurantium var. bergamia (Rutaceae) growing in southern Italy.

Schisandra chinensis

Germacranes and ElemanesGermacranes formally result from ring closure of C-1 and

C-10 of farnesane. 1(10),4-Germacradienes such as 1(10),4-germacradien-6-ol present as a glycoside in Pittosporum tobira may ungergo COPE rearrangements to elemadienes, exemplified by shyobunol from the oils of galbanum and kalmus, so that some isolated elemane derivatives are supposed to be artifacts arising from germacranes.

Pittosporum tobira

galbanum

kalmus

About 50 elemanes known to date comprise b-elemenone from the oil of myrrh, representing the COPE rearrangement product of germacrone, (-)-bicycloelemene from peppermint oils of various provenance (e.g. Mentha piperita or Mentha arvensis), and b-elemol which is not only a minor component of Javanese( ( جاوة جزيرة oil of citronella but is also foundمنin the elemi oil with an odor like pepper and lemon, expressed from the Manila elemi resin of the tree Canarum luzonicum (Burseraceae).

HumulanesRing closure of C-1 and C-11 of farnesane, not only

formally but also in biogenesis via farnesyldiphosphate, produces the sesquiterpene skeleton of more than 30 naturally occurring humulanes. Regioisomeric a- and b-humulene occur in the leaves of Lindera strychnifolia (Lauraceae).

Lindera strychnifolia

tree Canarum luzonicum (Burseraceae).

Mentha arvensis حقلي نعناع