What it is
Methyl cinnamate is the methyl ester of cinnamic acid. Its IUPAC name is methyl (E)-3-phenylprop-2-enoate. In basil, methyl cinnamate has a biosynthetic origin from cinnamic acid, whereas linalool and 1,8-cineol follow another pathway from mevalonic acid. Its molecular formula is C₁₀H₁₀O₂ and its molecular weight is 162.18 g/mol. It is classed as an alkyl cinnamate and a methyl ester, and it has roles as an insect attractant, a volatile oil component, a flavouring agent, a fragrance and an anti-inflammatory agent.
The parent acid
Cinnamic acid, from which the ester derives, is an organic compound with the formula C₆H₅-CH=CH-COOH. It is a white crystalline unsaturated carboxylic acid that occurs naturally in a number of plants, and it exists as a cis and a trans isomer, the trans form being the more common. The acid is obtained from oil of cinnamon or from balsams such as storax, and it has a honey-like odor. The oldest commercially used route to the acid is the Perkin reaction, and it can also be made by the Knoevenagel condensation of benzaldehyde with malonic acid.
Natural occurrence
Methyl cinnamate is found naturally in a variety of plants, including in fruits, like strawberry, and some culinary spices, such as Sichuan pepper and some varieties of basil. It is found naturally in the essential oils of Alpinia and in basil leaf oil. Eucalyptus olida has the highest known concentrations of methyl cinnamate (98%), with a 2-6% fresh weight yield in the leaf and twigs. This eucalypt is restricted to the Gibraltar Range National Park and nearby Timbarra Plateau.
In a study of twelve basil varieties grown in Colombia, ten had a high percentage of methyl cinnamate (35-80%), which defined their chemotype. In the basil varieties 'cinnamon', 'purple lovingly', 'sweet castle' and 'purple long-legged', methyl cinnamate made up more than 62% of the total essential oil. Methyl cinnamate was present in all twelve varieties, at 9-80%. Four essential oil chemotypes have been established for Ocimum basilicum: methyl chavicol, linalool, methyl eugenol and methyl cinnamate. Bulgarian or cinnamon basil oil, one of the distinct types of basil oil on the international market, is rich in methyl cinnamate.
Essential oils from galangal (Alpinia galanga) flowers collected in two regions of India contained (E)-methyl cinnamate at 19.7% and 7.1%. Methyl cinnamate is known to attract males of various orchid bees, such as Aglae caerulea.
In the two Indian flower oils, (E)-methyl cinnamate stood among the dominant components beside β-pinene (12.8 and 10.5%) and 1,8-cineole (18.4 and 9.4%). A flower oil from Yulin City in Guangxi, China, instead had farnesene as its most abundant component, at 64.3%.
Methyl cinnamate has also been reported in Alpinia hainanensis and Alpinia mutica, in three Xanthorrhoea species, and as a metabolite of Saccharomyces cerevisiae.
The basils 'purple ruffles', 'little virgin' and 'purple virgin' belong to the methyl cinnamate > linalool subtype. The 'large green leaves' variety, with linalool at 33% and methyl cinnamate at 25.2%, belongs to the linalool chemotype with a linalool > methyl cinnamate subtype. A cinnamon basil oil made by hydrodistillation had methyl cinnamate and linalool as main components in a 1:1 ratio, with small amounts of methyl chavicol and 1,8-cineol.
Eucalyptus olida is a tree that typically grows to a height of 20-30 m and forms a lignotuber. It has thick, rough, fibrous and flaky bark on the trunk and larger branches, lance-shaped to curved adult leaves, white flowers and a woody, barrel-shaped or bell-shaped fruit. It grows in forest and woodland in shallow soil derived from granite. Extracts of its leaves in hexane, methanol and ethyl acetate show high anti-oxidant activity.
Basil cultivars and isolation
In a comparison of 31 basil accessions and seven cultivars, the cultivar 'Cinnamon' stood out with 31% methyl cinnamate, a constituent with a cinnamon aroma. In a trial of 15 basil genotypes, the cultivars 'Anise', 'Fahéj illatú' and 'Licorice' held (E)-methyl cinnamate at 28.7%, 34.8% and 42.7%, beside linalool at 12.2%, 28.1% and 19.3%. In the same work methyl cinnamate inhibited a CTX-M β-lactamase, with an IC50 of 11.6 μg/mL against 8.1 μg/mL for clavulanic acid. Other plants that contain it include Ocotea quixos, the Ecuadorian cinnamon called ishpingo, the orchid Stanhopea embreei and vanilla. E-methyl cinnamate has applications in the flavouring area, and Eucalyptus olida provides an alternative to the methyl cinnamate chemotype of basil.
Safety
Methyl cinnamate is moderately toxic by ingestion. The oral LD50 for rats is 2610 mg/kg. It carries the GHS signal word Warning and the hazard statement H317. As a liquid it is combustible, and when heated to decomposition it emits acrid smoke and irritating fumes.
In the United States it appears among the substances added to food as a flavoring agent or adjuvant. Its FEMA number is 2698 and its JECFA number is 658.
Explore all seven extraits in the Discovery Set.
