Літсея кубеба

Litsea cubeba is a species of evergreen tree in the family Lauraceae. It produces a fruit which is processed for its lemony essential oil. The plant is a shrub that grows up to 5-12 meters high. The genus Litsea has about 622 species, of which 74 grow in China. The oil's main component is citral, at 70-85% of the oil.

Terroir and Sourcing

The tree is native to Assam, Bangladesh, Borneo, Cambodia, Taiwan, Thailand and Vietnam, among other places. The oil is mainly produced in China from plantations. China is a major producer of the oil, with an annual output of 1500-2000 tonnes. Chinese customs reported that the total export volume of the oil from 2019 to 2023 reached 1682 tonnes. The highest yield of essential oil is from the fruit. The oil can also be extracted from the leaf, but this is considered to be lower in quality.

Composition

Citral is an acyclic monoterpene aldehyde made of two geometric isomers, geranial and neral. Analysis of fruit oils from eight regions of China identified 59 compounds, the dominant components being monoterpenes (94.4-98.4%). The 59 compounds comprised 41 monoterpenes, 15 sesquiterpenes and three non-terpene compounds. Neral and geranial together made up 78.7% to 87.4% of the oil. Neral and geranial are cis-trans isomers of citral, and neral always occurred in higher quantities than geranial. D-limonene was a lesser constituent, at 0.7-5.3% of the oil. The composition varied significantly between regions, and even oils from the same province differed. In Litsea cubeba, the alcohol dehydrogenases LcADH28 and LcADH29 are important for citral accumulation, and the transcription factor LcMYB44 is a negative regulator of citral biosynthesis. LcADH28 shows higher activity against geraniol and LcADH29 against nerol.

Uses and Trade

In China, the Ministry of Health has approved the oil for use as a food additive in accordance with standard GB 2760-2007. Litsea cubeba is used extensively as a spice by the aboriginal peoples of Taiwan. The fresh green fruit is also eaten in salads, chutneys and pickles. Extracts of the bark, leaf, root and fruits have been used in traditional Chinese medicine for various diseases. The timber is sometimes used for making furniture and crafts. The oils are mostly exported to European and American countries for further purification and synthesis in value-added functional products. After solvent-free microwave extraction the peel can be removed completely, leaving kernels that are pressed for an oil used as a medium-chain saturated fatty acid feedstock.

Beyond Fragrance

The chemical industry uses the oil as a raw material for the synthesis of vitamin A and violet-like fragrances. Citral is a precursor in the industrial production of vitamin A, vitamin E and vitamin K. Citral is also a precursor to lycopene, ionone and methylionone. Condensed with acetone in an alkaline medium, citral gives pseudoionone, which is cyclized to ionone under acidic conditions. Citral usually serves as a recognized standard to evaluate the economic value of the oil in international trade.