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Ylang-ylang (Cananga odorata (Lam.) Hook. & Thoms. var.
genuina) essential oils from Comoros Islands:
characterization and variability
Céline Benini a, Jean-Paul Wathelet b, Patrick du Jardin a, Marie-Laure Fauconnier a
a Plant
b General
Biology Unit, Gembloux Agricultural University, Gembloux, Belgium
and Organic Chemistry Unit, Gembloux Agricultural University, Gembloux, Belgium
1. Introduction
The Comoros Islands constitute an archipelago
composed of four main islands located in the
Mozambique Channel, between Madagascar and the
Eastern coast of Africa. These islands are divided in
two political entities: Union of Comoros,
independent, consisting in Grande Comore,
Anjouan and Moheli and Mayotte, the second entity,
a French collectivity.
The study of essential oils extracted from both floral morphotypes of ylang-ylang
(morphotype with broad petals and normal morphotype) shows that there is a very
clear difference between the two chemical profiles and their respective
physicochemical properties (Fig. 4). Thus, the optical rotation and the refractive
index of the morphotype with broad petals are better according to AFNOR than
those of the normal morphotype, the specific gravity and the ester number are worse
in terms of oil general quality.
3.3. Chemical composition
Fig. 1: Comoros Islands
The Union of the Comoros is the world’s biggest producer of ylang-ylang essential
oils, exporting forty tons of it per year. Comorian ylang-ylang also provides the most
valuable essential oil that can be found on international market. This product
represents a high percentage of Comoros’ annual currency .
Molecular stucture of
eugenol
Ylang-ylang is a tree belonging to Annonaceae familly. It grows in full or partial sun,
and prefers the acidic soils of its native rainforest habitat. The leaves are long, smooth
and glossy. The flower is greenish yellow, curly.
Ylang-ylang essential oil is obtained through hydrodistillation or steam distillation of
the flowers and separated into different grades (extra S; extra; I; II; III) according to
when the distillates are obtained which possess their own physicochemical properties .
Fig. 5: Broad petals morphotype chromatogram with eugenol framed
2. Material and methods
Essential oils were extracted by hydrodistillation during 10
hours at 100°C (Fig. 2). In this study they were not
fractionned into different grades.
The chemical characterization consists in the establishment of
physicochemical properties (specific gravity, optical rotation,
ester number and refractive index) following AFNOR norms
and the chemical profile was establish by gaz chromatography
/mass spectrometry with the following column HP5 MS and
the following temperature program:
45°C (0 min) ⇒ 85°C (0 min) ⇒ 285°C (10 min)
Fig. 2: hydrodistillation
material
20°C/min
5°C/min
3. Results
Fig. 6: Normal morphotype chromatogram
3.1. Biological observations
Within
ylang-ylang
Comorian
plantations, there are several tree whose
flowers presents different morphologies
These trees can coexist at short distances
from each others.
Two of these morphotypes were studied.
The fisrt one was called ‘Broad petals’
because it has larger petals than flowers
commonly found in plantations. This one
also shows larger leaves and the tree is
more twisted and bulkier. The other
mophotype called ‘Normal’ refers to the
flowers the most commonly found in
plantations.
Fig. 3: Two morphotypes of ylang-ylang
studied
3.2. Physicochemical properties
A
B
B
250
0,98
200
Specific gravity
Ester number (mg of KOH)
A
150
100
50
0
0,97
0,96
0,94
Normal
Broad petals
Morphotypes
-5
Broad petals
Normal
-10
-15
-20
-25
Normal
Morphotypes
0
DD
Refractive index
C
Optical rotation (Degree)
C
Generally, these chemical profiles show that the normal morphotype is richer in
ester whereas the ‘Broad petals’ morphotype is richer in sesquiterpenes.
But the most marked difference between the two chromatograms is the presence of
eugenol (Fig. 5) in the essential oil obtained from the normal morphotype whereas it
is present only at very low concentration in the other (Fig. 6).
4. Conclusions
The first results obtained showed that essential oils resulting from both floral
morphotypes are chemically and statistically different, both for their
physicochemical properties their chemical composition. However, it is difficult to
affirm that one of these oils is qualitively better than the other following the
disparity of the results observed for the physicochemical properties. Nevertheless,
the presence of esters in greater quantity in the oil of the ‘normal’ morphotype
tends to show that these oil would be qualitatively higher than the other.
It would be interesting to continue and look further into this study by in particular
separating ylang-ylang oil into different grades in order to characterize each
fraction individually. There is currently a thesis that is studying the variability at an
enlarge level. The experiment is carried on on four islands: Grande Comore,
Madagascar, Mayotte and Nosy Bé. The polymorphism is studied at morphological,
molecular and chemical levels. The final aim is to be able to clearly identify
particularly good producers of the best quality essential oils. This could lead to an
improvement and standardization of the production
0,95
0,93
Broad petals
Chemical analysis reveals that the two oils are chemically different. These
dissimilarities concerned mainly geraniol, α-humulene, germacrene D in which
morphotype ‘Broad petal’ is richer and benzyl acetate, l’α-farnesene and benzyl
salicylate, l’α-farnesene, benzyl salycilate and cinnamyl acetate in which normal
morphotype is the richest.
1,51
1,505
1,5
1,495
-30
-35
1,49
Morphotypes
Broad petals
Normal
Références
AFNOR (2000). Recueil de normes : les huiles essentielles. Tome 1. Echantillonnage et méthodes
d’analyse. AFNOR, Paris, 440 p.
AFNOR (2000). Recueil de normes : les huiles essentielles. Tome 2. Monographies relatives aux
huiles essentielles (H à Y). AFNOR, Paris, 661-663
Morphotypes
Fig. 4: Ester number (A), Specific gravity (B), Optical
rotation (C), Refractive index (D).
.