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Finocchio fennel is closely related to sweet and bitter fennel commercially produced for either the seed, which is used as a spice, or the essential oil extracted from the seed. The essential oil of sweet fennel is used in cosmetics, pharmaceuticals, perfumery, and as a food additive. Extensive research has been conducted on the chemical composition of volatile oils of sweet fennel, var. dulce (Karlsen et al. 1969; Tsvetkov 1970; Ashraf and Bhatty 1975; Ravid et al. 1983; Akgul 1986; Katsiotis 1988); and bitter fennel, var. vulgare (Rothbacher and Kraus 1970; Trenkle 1972; Kraus and Hammerschmidt 1980; Arslan et al. 1989).
Karlsen et al. (1969) reported the major constituents of sweet fennel (var. dulce) and bitter fennel (var. vulgare) to include anethole, estragole, and fenchone plus an additional 18 compounds extracted in the monoterpene fraction of the fruit. The minor constituents accounted for 1 to 5% of the total oil of the volatile oil and included: alpha-pinene, camphene, ß-pinene, alpha-phellandrene, myrcene, limonene, ß-phellandrene, gamma-terpinene, cis-ocimene, terpinolene, and p-cymene (listed in order of elution). Significant differences in oil composition between var. dulce and vulgare were noted (Karlsen et al. 1969). Katsiotis (1988) reported that the major oil constituent of sweet fennel fruit was trans-anethole (>83%), followed by relative minor amounts of estragole, fenchone, p-anisaldehyde and limonene (at relative concentrations from <1 to <5%) with only minor amounts of cis-anethole (<1.0%). The degree of comminution rather than the hydrodistillation period or distillation rate was found to influence the oil composition of sweet fennel fruit (Katsiotis 1988). Seed oil composition was reported to be influenced by growing region (Arslan et al. 1989).
Despite the extensive information on sweet and bitter fennel, little information is available on the chemical composition of finocchio fennel and the differences, if any, between the bulbs and the foliage which can be marketed separately in the fresh green form. Here, we report the chemical composition of the volatile oils from the bulbs of 16 commercially available cultivars of Finnochio fennel.
Plants were placed into a randomized block design with three replications consisting of single row plots (3 m length, rows 1 m apart, plants 9 cm apart). A single harvest (July 17) was taken after all cultivars had begun to flower. Essential oils from the bulbs and foliage were extracted by hydrodistillation (1 h) with a modified clevenger trap (Charles and Simon 1990). The essential oil content was determined on a volume to fresh weight basis. Essential oil constituents were identified on the basis of retention time and coinjection with authentic compounds using a Varian 3700 gas chromatograph (GC) equipped with FID and an electronic 4270 integrator. A fused silica capillary column (12 m x 0.2 mm i.d) with an OV 101 (Varian, polydimethylsiloxane) bonded phase was used. Direct injection of 0.5 ul samples with He as a carrier gas and oven temperature held isothermal at 80°C for 2 min, and then programmed to increase at 3°C/min, to 160°C gave complete elution of all peaks (sensitivity 1010; attenuation 16). The injector and detector temperatures were 180° and 300°C, respectively. Identification of all compounds were verified by analyzing both standards (alpha-pinene, myrcene, limonene, gamma-terpinene, fenchone, methyl chavicol, fenchyl acetate, and anethole) and essential oil samples by GC/mass spectroscopy as previously described (Simon and Quinn 1988; Charles et al. 1990). The mass spectroscopy conditions were as follows: ionization voltage, 70 eV; emission current, 40 µA; scan rate, 1 scan/s, mass range, 40 to 500 Da; ion source temperature, 160°C.
The major essential oil constituents in the bulbs of finocchio fennel were anethole and limonene, comprising >80% of the oil (Table 1). In most cultivars, anethole was higher than limonene, except in 'Zefa fino' and 'Mantovano' where limonene was higher. Other chemical constituents in the bulb oil included alpha-pinene, myrcene, gamma-terpinene, fenchone, methyl chavicol, and fenchyl acetate. The composition of essential oil from the foliage was similar to that found in the bulbs but, limonene was always higher than anethole in the foliage (Table 2).
The compounds present in the essential oils obtained from finocchio fennel bulbs and foliage are similar to those reported for sweet and bitter fennel but, the relative percentages of compounds such as anethole and limonene differ. Arslan et al. (1989) reported the percentage of anethole to be 86 to 88% in sweet fennel oil and 74% in bitter fennel oil while limonene was only 4 and 2% respectively in sweet and bitter fennel oil. Embong et al. (1977) working with Foeniculum vulgare var. dulce reported anethole as 69% in fruit oil and 39% in herb oil, the relative percentage of limonene being 8 and 20% in the fruit and herb oil. Finnochio fennel appears to contain lower anethole and higher limonene concentrations compared to sweet fennel and bitter fennel oil extracted from seeds and fruit. The bulbs and foliage of finocchio fennel also contain relatively higher concentrations of fenchyl acetate compared to the fruit of sweet fennel. This finocchio fennel oil could be designated as limonene-enriched, as suggested by Toth (1967) rather than a sweet or bitter oil.
While finocchio fennel bulbs contain higher concentrations of anethole, than that reported from sweet fennel foliage (Embong et al. 1977), the foliage of finocchio fennel is also highly aromatic. As foliage of sweet fennel is marketed as a fresh herb, called fennel weed or fennel herb, the possibility of marketing both the bulb and the fresh-cut foliage from the same plant of finocchio fennel remains an intriguing yet unexplored possibility.
|Essential oil constituentsz (% total essential oil)|
|Fenchone||Methyl chavicoly||Fenchyl acetate||Anethole|
|Firenze grosso dolce||1.41||1.05||39.03||1.30||0.78||1.35||4.59||42.90|
|Parma sel. Fucino||1.50||1.08||37.96||1.62||0.15||1.45||5.08||47.80|
|Romanesco sel Urbe||1.12||0.89||41.18||0.98||0.12||1.44||4.37||46.99|
|Essential oil constituentsz (% total essential oil±SD)|
|Cultivar (source)||alpha- |
|Fenchone||Methyl chavicoly||Fenchyl acetate||Anethole|
|Grossissimo Mammuth (FM&C)x||1.62±1.0||1.34±0.12||66.1±2.7||0.66±0.26||0.6±0.2||0.9±0.11||1.8±0.4||24.8±3.3|
|Zefa Fino (JS)||0.97±0.62||0.94±0.10||62.7±2.8||0.14±0.2||0.3±0.23||1.1±0.27||2.8±0.9||28.1±12.7|