‘mapo’ tangelo essential oil
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FLAVOUR AND FRAGRANCE JOURNAL, VOL. 5,205-210 (1990)
Mapo Tangelo Essential Oil* Giacomo Dug0
Dipartimenfo di Chimica Organica e Biologica, Facofta di Scienze, Universita di Messina, Italy
Antonella Cotroneo, Antonella Verzera and Giovanni Dug0 Dipariimenio Farmaco-chimico, Facolta di Farmacia, Universita di Messina, 98168 Messina, Iial-v
Gianvincenzo Licandro Panagrum S.p.A., Giammoro, Messina, Italy
The volatile fraction of Mapo tangelo essential oil was studied using chromatography on a neutral alumina column and gas chromatography with a SE 52 capillary column. Its composition has been compared with that of the essential oils of mandarin and grapefruit.
The olfactory characteristics and the composition of the essential oil are in relation to the origin of tangelo which was obtained in Sicily by crossbreeding mandarin with grapefruit.
KEY WORDS Mapo tangelo Mandarin Grapefruit
The Mapo tangelo, first cultivated in 1950 by the Istituto Sperimentale per lAgrumicoltura at Acireale, is a hybrid obtained by crossbreeding grapefruit with mandarin.
Since then, the Mapo tangelo has been favour- ably accepted by the fresh fruit market because of its olfactory characteristic and because it ripens before the orange.
At present its cultivation is expanding and this could lead to future industrial interest. Because of this we thought it useful to carry out preliminary research on the composition of the volatile fraction of Mapo tangelo essential oil and to compare the results obtained with those of mandarin and grape- fruit essential oils.
Research was carried out on:
-three samples of Mapo tangelo essential oil extracted from fruits picked in October 1987
Essential oils Volatile fraction Composition
near Ragusa, Sicily, in a plantation where no pesticide treatment or chemical fertilizers are used;
-two samples of grapefruit essential oil, one ex- tracted from fruits picked in the plantation men- tioned above and the other from fruits picked on the plantation of the Stazione Sperimentale per 1Industria delle Essenze e dei Derivati Agrumari near Reggio Calabria, in December 1987.
Extraction of the essential oil was carried out in the laboratory by applying manual pressure on the rind so as to cause the breaking of the oil glands and the release of the essential oil itself which was collected and centrifuged.
All the samples were analysed by gas chromato- graphy on an instrument equipped with FID, split/ splitless injection system and a data processor using the following experimental conditions, pre- viously described for lemon and mandarin3 essen- tial oils: glass capillary columns coated with SE 52, 25 m x 0.32 mm id.; column temperature, 60C (8 min) to 100C at 3C/min, to 130C at 2.5C/ min, to 180C at 3C/min; injector and detector temperatures, 280C; carrier gas, H, 0.40 kg/cm;
*Twenty-sixth paper of the series On the genuineness of citrus essential oils originally presented at the 11th Congress of Essential Oils, Fragrances and Flavours, New Delhi, India, 1989.
0882-5734/90/040205-06 $05.00 0 I990 by John Wiley & Sons, Ltd.
Received 6 December 1989 Accepted 24 May I990
206 G. DUG0 ETAL.
injection mode, split; injection volume 0.5 pl; split ratio 1:200.
The tangelo essential oils were also fractionated into classes of substances by chromatography on neutral alumina columns4 using the following con- ditions: column, glass 1.6 cm i.d.; adsorbent, neu- tral alumina, grade I1 activity, 20 g; sample, 100 p1 essential oil. Eluents: fraction 1 (hydrocarbons), light petroleum (b.p. 30-50C); fraction 2 (esters), light petroleum-diethyl ether (97:3, v:v); fraction 3 (carbonyl compounds), light petroleum-diethyl ether (80:20); fraction 4 (alcohols), diethyl ether.
The fractions obtained were analysed by gas chromatography under the same conditions that were used for the essential oils themselves.
Use was also made of the average results from the analysis of 266 samples of mandarin essential oil previously effected in the context of a study on the composition of Italian mandarin essential 0 i 1 . ~ , ~
RESULTS AND DISCUSSION
The three samples of tangelo essential oil gave similar qualitative and quantitative results as did also the two samples of grapefruit essential oil.
Figure 1 shows the chromatograms of the vola- tile fraction of the Mapo tangelo essential oil and of the fractions obtained by separation on neutral alumina column. As can be seen from the indica- tions given, it has been possible to identify 34 components and to determine, according to the chromatographic behaviour on neutral alumina column, the class to which three unidentified com- ponents belong.
Tables 1 and 2 show respectively the composi- tion of the three samples of essential oil studied. The average percentages of the single components and of classes of substances are reported; the same tables show the composition of grapefruit and mandarin oils.
Figure 2 compares the chromatograms of the Mapo tangelo essential oil with those of the grapefuit and mandarin essential oils.
The principal component of the volatile fraction of the Mapo tangelo essential oil, like all other citrus essential oils, is limonene which represents about 73% of the total; among the other monoter- penes, considerable quantities of y-terpinene, about 17%, are present. Caryophyllene is the main sesqui- terpene and the ester fraction is almost completely made up by methyl N-methylanthranilate. Among
the oxygenated compounds the alcohol fraction is the most plentiful, while that of carbonyl com- pounds is the least.
The total monoterpenes have the same value (Table 2) in the three essential oils considered, but the composition of this fraction is very similar for tangelos and mandarins, while that of the grape- fruit is very different. In grapefruit essential oils, in fact, limonene content is about 93% while that of mandarin and tangelo is about 70%.
In grapefruit essential oil, with the exception of myrcene and cis- and trans-j?-ocimene, lower quan- tities of all other monoterpenes are found if com- pared with that of tangelo and mandarin. On the whole, in fact, the composition of the monoterpene fraction of grapefruit essential oil is very similar to that of the sweet orange.
In tangelo essential oil, there are more sesquiter- penes than in mandarin essential oil; these are comparable to those of the grapefruit essential oil. The qualitative composition of this fraction in the tangelo is, however, much nearer to that of the mandarin than that of the grapefruit, in which a higher number of components can be found.
The ester fraction, as for the mandarin, is almost exclusively made up of methyl N-methylanthrani- late. It is to be noted that the tangelo essential oil is the only citrus essential oil, extracted from fruits, having a higher content of this ester than mandarin essential oil. In the grapefruit essential oil, methyl N-methylanthranilate is absent, the ester content is clearly lower and a larger number of components are present.
The total carbonyl components are present in similar quantities in tangelo and mandarin essen- tial oils; however, in the mandarin essential oil the most prevalent carbonyl compound is sinensal which is absent in tangelo essential oil. This is probably the most significant qualitative difference between tangelo and mandarin essential oil.
In grapefruit essential oil, the total carbonyl compound content is about double that of the other two essential oils considered and the qualit- ative composition is very similar to that of the tangelo, if components present in very small quan- tities are excluded.
The total alcohol content in the Mapo tangelo essential oil is about double that of mandarin and grapefruit essential oils. The qualitative composi- tion of this fraction and the relationship between the various components are, however, more or less identical in tangelo and mandarin essential oils; on the contrary, in grapefruit essential oil, cis-sabinene
'MAPO' TANGELO ESSENTIAL OIL 207
Fig. I. Chromatogram of 'Mapo' tangelo essential oil and of the fractions obtained from its separation on a neutral alumina column. (A) Essential oil. (B) Hydrocarbons. (C) Esters. (D) Carbonyl compounds. (E) Alcohols. ( 1 ) a-Thujene. (2) a-Pinene. (3) Camphene. (4) Sabinene. (5) 8-Pinene. (6) Myrcene. (7) Octanal. (8) a-Phellandrene. (9) a-Terpinene. (10) p-Cymene. (1 1) Limonene. (12) cis-/?- Ocimene. ( 1 3) trans-b-Ocimene. (14) y-Terpinene. (15) cis-Sabinene hydrate. (16) Terpinolene. (17) trans-Sabinene hydrate. (18) Linalol. (19) Nonanal. (20) Citronellal. (21) Terpinen-4-01, (22) a-Terpineol. (23) Decanal. (24) Nerol + Citronellol. (25) Neral. (26) Geranial. (27) Thymol. (28) Citronellyl acetate. (29) Neryl acetate. (30) Geranyl acetate. (31) Methyl N-methylanthranilate. (32)
Caryophyllene. (33) Humulene. (34) Farnesene
Table 1. Composition, in percentage of single components, of Mapo tangelo, mandarin and grapefruit essential oil
Mapo tangelo (average of 3
samples extracted in laboratory)
1 a-Thujene 2 a-Pinene 3 Camphene 4 Sabinene 5 8-Pinene 6 Myrcene 7 Octanal + a-phellandrene 8 a-Terpinene 9 p-Cymene
10 Limonene 1 I cis-8-Ocimene 12 trans-8-Ocimene 13 y-Terpinene 14 cis-Sabinene hydrate 15 Octanal 16 Terpinolene 17 trans-Sabinene hydrate 18 Linalol 19 Nonanal 20 Monoterpene 21 Ester 22 Citronella1 23 Terpinen-4-01 24 Monoterpene + ester 25 Ester 26 a-Terpineol 27 Decanal 28 Ester 29 Nerol 30 Carbonyl compound 31 Neral 32 Geraniol 33 Geranial
34 Alcohol 35 Thyrnol 36 Undecanal 37 Ester 38 Ester 39 Citronellyl acetate 40 Neryl acetate