Raimo Hiltunen and Yvonne Holm

Department of Pharmacy, P.O Box 56, FIN-00014 University of Helsinki, Finland

INTRODUCTION

The genus Ocimum belongs to the Lamiaceae family and consists of 50 to 150 species of herbs and shrubs. Plants of the genus Ocimum are collectively called basil (Simon et al., 1990). According to Hegnauer (1966) the genus Ocimum comprises 50-60 species. In 1983 Czikow and Laptiew reported that there exist 150 species in the genus Ocimum and one year later Ruminska reported that about 60 species have been classified as belonging to this genus (Suchorska and Osinska 1992).

Basil oil is one of the most widespread oils. Currently the oil production is 15 tons in India, 7 tons in Bulgaria, 5 tons in Egypt, 4.5 tons both in Pakistan and the Comores, 2 tons in Israel and smaller amounts in Yugoslavia (1 ton), USA (1 ton), Madagascar (1 ton), Réunion (0.5 ton), Albania (0.5 ton), Hungary (0.3 ton) and in Argentina (0.2 ton) (Lawrence 1992).

The market for basil oil is dominated by European and Egyptian basil oil. The European or sweet basil is cultivated and the oil produced in the Mediterranean region and in the United States. These two types of oil are considered to be of the highest quality and the ones which produce the finest odour. Sweet basil oil is characterized by high concentrations of linalool (30-90%) and methyl chavicol (50-90%). The other characteristic oil compounds are 1,8-cineole, eugenol and methyl eugenol. In addition to oxygenated monoterpenes and phenylpropanoids, also small amounts or at least traces of monoterpene and sesquiterpene hydrocarbons are typically present in both oils.

Reunion basil oil, also known as Comoro, African or exotic basil oil, is another type of basil oil traded on the international market. This type of basil is cultivated and the oil produced on Reunion, Madagascar, in many parts of Africa and occasionally on the Seychelles. Reunion basil oil is rich in methyl chavicol with a high content of camphor but low contents of linalool, 1,8-cineole and eugenol.

Basil is known to occur as several chemotypes or cultivars which differ in their essential oil composition. The variation in chemical composition of basil oils is thought to be mainly due to polymorphism in Ocimum basilicum L., which is caused by interspecific hybridization (Hasegawa et al., 1997). The morphological diversity within basil species has been accentuated by centuries of cultivation. Great variation in pigmentation, leaf shape and size and pubescence are seen (Simon et al., 1990).

ESSENTIAL OIL OF BASIL

The essential oils of basil are generally obtained by steam distillation or hydrodistillation from flowering tops (French sweet basil oils) and leaves of basil plants. The oil yield generally ranges from 0.2 to 1.0 but can be as high as 1.7%, depending on the source and phenological stage of the plants. Also whole fresh flowering herbs (American sweet basil oils) have been used as the starting material for the commercial production of volatile oils. Supercritical fluid extraction (SFE) has also been applied to the isolation of volatiles from basil (Manninen et al., 1990, Reverchon 1994, Pluhar et al., 1996, Lachowicz et al., 1997).

Volatiles in the essential oils of Ocimum species are mainly derived either from the phenylpropanoid or mevalonic acid metabolism. Biogenetic pathways and the formation of volatiles, such as terpenes from the isoprenoid metabolism and phenylpropanoids from the cinnamic acid metabolism, have been studied and discussed intensively during the last 30-40 years (Schreier 1984). The biosynthesis of the essential oil compounds of Ocimum species will not be discussed in this context.

CHEMICAL COMPOSITION

The chemical composition of essential oils of plants in the genus Ocimum, especially O.basilicum, have been the object of many studies since the 1930's. The older chemical data of Ocimum oils is summarized by Gunther (1949), Gildemeister and Hoffmann (1961), Hegnauer (1966) and Hoppe (1975). Especially Lawrence (1971, 1972, 1978, 1980, 1982, 1986a, 1986b, 1987, 1988, 1989, 1992a, 1992b, 1992c, 1995, 1997) has done a great work in summarizing and reporting the results of the chemical composition of basil oils published during the last 25 years. Also the studies made by Sobti et al. (1976), Gulati (1977), Gulati et al. (1977a, 1977b), Peter and Rémy (1978), Vernin et al. (1984), Nykânen (1987), Ekundayo et al. (1989), Gaydou et al. (1989), Fun and Baerheim Svendsen (1990) and particularly Zola and Garnero 1973, Nykânen 1987, Chien 1988, Lawrence 1988, Hasegawa et al. (1997) have increased our knowledge about the chemical composition of basil oils. Nowadays approximately 140 components of basil oil (O.basilicum) are known, including more than 30 monoterpenes, almost 30 sesquiterpenes, about 20 carboxylic acids, 11 aliphatic aldehydes, 6 aliphatic alcohols, about 20 aromatic compounds and about 20 compounds belonging to other groups than those mentioned above (Table 4.1).

In general basil oils are characterized by oxygenated monoterpenes (Table 4.2) and phenylpropane derivatives (Tables 4.3-4.9). In addition to oxygenated monoterpenes almost all of the known monoterpene hydrocarbons are found in basil oils (Table 4.1). Usually their concentrations are marginal except for the ocimenes, y-terpinene and p-cymene in the oil of O.gratissimum.

An oil of O.basilicum var. hispidum had an exceptional chemical composition containing an acyclic monoterpene ketone, dihydrotagetone, as its main compound (82.3%) and smaller amounts of compounds structurally related to it, including ipsenone (0.2%), cis-tagetone (0.5%) and trans--tagetone (0.2%) (Ruberto et al., 1991).

ESSENTIAL OIL OF OCIMUM Table 4.1 Chemical constituents of basil oils

Monoterpene Hydrocarbons

3-carene

^>-cymene limonene myrcene

«V-a/Zo-ocimene trans- «//<?-ocimene a-phellandrene

ß-phellandrene a-pinene

ß-pinene sabinene a-terpinene y-terpinene terpinolene a-thujene

Oxygenated Monoterpenes borneol bornyl acetate camphor

1,8-cineole citronellal citronellol citronellyl acetate

^>-cymen-8-ol fenchone fenchyl acetate a-fenchyl acetate fenchyl alcohol geranial geraniol geranyl acetate isobornyl acetate linalool linalool oxide or-linalool oxide trans-Unalool oxide linalool oxide (futanoid)

linalool oxide (pyranoid)

linalyl acetate menthol menthone

myrtenal

6-guaiene

neral

ß-gurjunene

nerol

y-gurjunene

neryl actate

ß-himachalene

trans-ocimene oxide

a-humnlene

perilla aldehyde

isocaryophyllene

terpinen-4-ol

ledene

a-terpineol

OC-muurolene

a-terpinyl acetate

ß-patchoulene

a-thnjone

Ot-santalene

ß-thujone

a-selinene

ar-sabinene hydrate

ß-selinene

ftmr-sabinene hydrate

ß-sesquiphellandrene

viridifloral

Sesquiterpene Hydrocarbons

a-amorphene

Oxygenated Sesquiterpenes

or-a-bergamotene

a-bisabolol

¿ra«.r-a-bergamotene

ß-bisabolol

bicyclogermacrene

bulnesol

bicycloelemene

T-cadinol

CX-bisabolene

10-epi-a-cadinol

ß-bisabolene

/ra»i-cadinol

ß-bourbonene

ß-caryophyllene oxide

E-bulgarene

cedrol

CX-cadinene

cubenol

8-cadinene

elemol

y-cadinene

ß-eudesmol

calamenene

y-eudesmol

ß-caryophyllene

farnesol

a-caryophyllene

nerolidol

ß-cedrene

ledol

2-fö/-a-cedrene

spathulenol

a-copaene

ß-copaene

a-cubebene

Others

ß-cubebene

cydosativene

^»-methoxy acetophenone

ß-elemene

wo-amvl alcohol

ö-elemene

benzene

y-elemene

butanal

(elixene)

ß-damascenone

a-farnesene

ß-damascone

E-ß-farnesene

2,4-decadienal

germacrene-D

decanol

germacrene-B

dodecanol

a-guaiene

5-dodecalide

Table 4.1 (Continued)

cumin aldehyde

3-octanal

ethyl acetate

2,4-octadienal

2-ethyl furan

3-octanone

2-methyl furan

octanol

ethyl-2-methyl butyrate

3-octanol

methyl-2-methyl butyrate

trans- 2-octen-l-al

furfural

l-octen-3-ol

heptanal

octyl acetate

hexanol

1 -octen-3-yl acetate

oj-hex-3-en-l-ol

pentanal

5-methyl-2-heptanone

2-methyl-3-methoxy

6-methyl-5-hepten-2-one

pyrazine

6-methyl-3-heptanone

tetra-methyl pyrazine

ar-3-hexenol

quinoline

3-hexenyl acetate

undecylaldehyde

fj>-3-hexenyl acetate

Aromatic Compounds

ar-3-hexenyl benzoate

methyl isovalerate

ar-anethole

methyl jasmonate

taBj-anethole

methyl epi-jasmonate

anisaldehyde

ar-jasmone

benzaldehyde

//»»¿-jasmone

benzyl alcohol

dibutyl octanediotate

benzyl acetate

benzyl formiate benzyl benzoate /»-methoxybenz aldehyde chavicol methyl chavicol (= estragóle)

cinnamyl acetate

(E) -methyl ciimamate

(Z) -methyl cinnamate

/>-methoxycinnamyl-

alcohol coumarin methyl eugenol j&-methoxy-cinnamaldehyde eugenol acetyl eugenol isoeugenol phenyl ethyl alcohol phenyl ethyl acetate a-p-dimethyl styrene methyl salicylate methyl thymol thymol vanillin

Chemical compounds in essential oils are found either as free terpenoids and phenylpropanoids or bound to sugar moieties. Lang and Hörster (1977) studied the production and accumulation of essential oil in O.basilicum callus and suspension cultures. They found that both free and sugar bound monoterpenoid and phenylpropanoid substances existed in morphologically undifferentiated callus-suspension cultures. However, the sugar bound form seemed to be the preferred accumulation form of the studied substances.

MAIN AND MAJOR COMPOUNDS IN OCIMUM OILS

In the following the main and some major compounds detected in the essential oils of Ocimum are discussed. In this connection the main compounds are those which represent 50% or more of the total oil. However, a relative percentage of 50% does not mean that the absolute amount of the compound is 50% of the total oil. The percentage composition of an essential oil is usually based on gas chromatographic analysis and on the assumption that the detector response is the same for all the involved compounds. This assumption is, of course, false. The major compounds are all the constituents, whose relative percentages are somewhere between 20-50% of the total oil. Ocimum oils generally consist of one or two, seldomly more than four compounds, with a proportional share of

ESSENTIAL OIL OF OCIMUM Table 4.2 Predominant oxygenated monoterpenes in basil oils

Constituent

Ocimum spp.

References1

linalool

0. basilicum

see Table 3

camphor

0. canum

Hegnauer 1966, Ntezurubanza et al., 1986, Xaasan and Cabdulraxmaan 1981

0. basilicum var. glabratum

Gupta 1994

0. kilimandscbaricum

Prasad et al., 1986

1,8-cineole

0. canum

0. kilimandscbaricum

Ntezurubanza et al, 1984

0. micranthum

Charles et al., 1990

0. keniense

Mwangi et al., 1994

0. basilicum

Holm etal., 1989

O. gratissimum2

Cheng and Liu 1983

geraniol

O. canum

Sobti and Pushpangadan 1982

O. basilicum

Sobti and Pushpangadan 1982

citral

O. citriodorium

Simon etal., 1990

neral

0. citriodorium

Grayer et al., 1996

geranial

O. x ätriodorium'

Grayer et al., 1996

thymol

0. gratissimum

El-Said etal, 1969, Sobti 1979,Janssen etal, 1989, Thomas 1989, Hegnauer 1966, Gildemeister and Hoffmann 1961, Sofowora 1970, Sainsbury and Sofowora 1971, Ntezurubanza et al., 1987, Pino et al., 1996

0. basilicum

Fatope and Takeda 1988

0. viride

Ekundayo 1986

1 see also Guenther 1949, Gildemeister and Hoffmann 1961.

2 1,8-cineole as the major compound in the stem oil.

3 a hybrid between O. basilicum and O. americanum.

1 see also Guenther 1949, Gildemeister and Hoffmann 1961.

2 1,8-cineole as the major compound in the stem oil.

3 a hybrid between O. basilicum and O. americanum.

the total oil greater than 20%. Therefore, also smaller compounds (5-10%) can be considered to be major compounds.

Aromatherapy Natural Scents that Help and Heal

Aromatherapy Natural Scents that Help and Heal

You have probably heard the term Aromatherapy and wondered what exactly that funny word, „aromatherapy‟ actually means. It is the use of plant oils in there most essential form to promote both mental and physical well being. The use of the word aroma implies the process of inhaling the scents from these oils into your lungs for therapeutic benefit.

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