-linalool.gif){kind=small}
(+)-linalool
-linalyl_acetate.gif){kind=small}
(+)-linalyl acetate
bergaptene
Citrus aurantium var. bergamia (Rutaceae)
Bergamot oil, one of perfumery's most important essential oils, is expressed from the peel of the non-edible
fruits of Citrus aurantium var. bergamia, traditionally grown in the southern part of Calabria, Italy, where the soil and climatic conditions are very favourable for its cultivation. Bergamot oil is used extensively in perfumery for its sweet freshness.
Citrus oils are perfumery ingredients used in large amounts to impart fresh, sparkling notes without being overpowering. They are used at concentrations up to 25 % as a basis for the classical Eau de Colognes of the Maria Farina type like 4711 (Mülhens 1881), the modern 'Eau Fraiche'-types like Eau Sauvage (Dior 1966) or the modern classicals like Baldessarini (Boss 2002). Citrus oils harmonize very well with a large number of essential oils and synthetic odorants and are used in different proportions in nearly all modern creations. Perfumes of the so-called Chypre and Fougère types are not possible without bergamot oil [3]. Bergamot oil is also used for flavouring purposes, e.g. in Earl Grey tea and the so-called althea drops.
Bergamot oil is the only citrus oil in which (+)-limonene (26 %) is not the dominant component. The oil is rich in
(+)-linalool and (+)-linalyl acetate (> 50 %). The crude bergamot oil contains the photosensitizing furocoumarin bergaptene which must be removed before perfumery use [6].
alpha-betulenol
betulin
Birch
Betula pubescens, B. pendula, B. alba (Betulaceae)
The tender leaves of downy birch, B. pubescens, are protected
by a delicate balsam, endowing the birch moor with an enchanting fragrance
in the early springtime. Birch bud oil is rich in sesquiterpenes, among
them alpha-betulenol, alpha-betulol, germacrene D, alpha-copaene, beta-bourbonene
and aromadendrene [40] [41]. The oil has been extracted on a limited scale,
mainly for use in skin- and hair tonics.
The white colour of birch bark is due to air vacuoles in the thin-walled
cells and to the substance betulin
(up to 24 %), making the bark resistant to decay. Betulin has recently
gained interest as a chemical of potential medical applications.
The pleasant smell from burning birch wood is caused by specific compounds
from pyrolysis of betulin and birch lignins. The smell is somewhat reminiscent
of that of oakmoss.
Prunus padus (Rosaceae)
Bird cherry is a large bush or a small, rounded tree from northern Europe and Asia, growing in moist and humic soil on the edge of woods, etc. It blooms in early May with multitudes of sweetly scented flowers in racemes. The English name refers to the fruit, which is very astringent and bitter, unsuitable for human food, but readily eaten by birds, who do not taste astringency as unpleasant.
The brown bark of the young branches contains amygdalin, a cyanogenic glycoside common to most rosaceans. When the bark is crushed, the amygdalin is enzymatically transformed into benzaldehyde, hydrogen cyanide and beta-gentiobiose. Benzaldehyde is revealing itself by its odour, known from bitter almond. The bark was formerly a pharmacy item (Cortex Padi).
Prunus amygdalis var. amara (Rosaceae)
Bitter almonds (and other seeds of the rose family) contain amygdalin, a so-called cyanogenic glycoside. When the almonds are damaged (chewed), the amygdalin is enzymatically hydrolyzed to benzaldehyde, deadly hydrogen cyanide, and the disaccharide beta-gentiobiose. It is claimed that about 20 almonds are the lethal dose in adults, but you can't possibly eat (chew) even a single almond. The chokingly powerful benzaldehyde flavour and the stunning of the tongue by hydrogen cyanide make you spit it out at once! Oil of bitter almond was formerly used as a flavour, e.g. in marzipan, but has now been completely replaced by synthetic benzaldehyde.
examples of boronia odorants derived from carotene:
beta-ionone, 3a-hydroxymegastigm-7(E)-ene-9-one and megastigm-7(E)-ene-3,9-dione
Boronia megastigma (Rutaceae)
South-western Australia is the home of the shrubby boronia, a member of the rue family. It has 8-10 cm wide, chocolate-coloured, bell-shaped flowers emanating a fragrance somewhat between that of freesia and osmanthus. Boronia was unknown in classical European perfumery, but Tasmania now has a production of a so-called boronia absolute: The flowers are extracted with petroleum ether, yielding a waxy concentrate after evaporation. The concentrate is then extracted with alcohol, chilled, filtered and finally evaporated at reduced pressure (Rota-Vapor). Boronia absolute is used in fine perfumery and as an aroma fortifier. It has been known for several years that beta-ionone plays a major role in the fragrance of boronia. Lately it has been shown that it is followed by several similar compounds, all being metabolites of carotene. Moreover, methyl jasmonate seems to play a role in the overall fragrance [42].
4-methoxy-2-methylbutan-2-thiol
Ribes nigrum, R. sanguineum (Grossulariaceae) Black currant, Redflower currant
The young leaves, flower buds and berries of black currant carry strongly odoriferous glandular trichomes giving the plant a characteristic smell. An extract for use in flavours and fragrances has been marketed since the early 1960s as 'Bourgeons de Cassis'. It has a distinctive aroma with a fresh top note, an intensely cat urine-like nuance and a strong fruity background. Latrasse et al. in 1982 identified 4-methoxy-2-methylbutan-2-thiol as an important trace constituent of the black currant aroma [83] [84].
Redflower currant, a close relative to black currant, has the same olfactory characteristics. It is a native of the mountainous regions in California and Mexico, but is now grown in many temperate zones as an ornamental plant. In the photo on the right, the glandular hairs are just visible on the flower buds. Redflower currant blooms in the early springtime. Where the bushes form dense stands on sunny slopes, the air may be heavy with their distinctive scent. A black currant-like note is present in other plants too, e.g. in the leaves of the South African buchu.