Citronella Oil and Its Derivatives
There are two main types of Citronella Oil in the market where Ceylon Citronella Oil (inferior type) is made from Cymbopogon nardus plant and Java Citronella Oil (superior type) is made from Cymbopogon winterianus. Indonesia is the third largest world producer of citronella oil after China and Vietnam, with production of up to 350 tons per year, and this oil is considered as one of the 20 most important essential oils [1]. The global demand of Citronella Oil increases 3-5% annually, and the main countries that imported Indonesian Citronella Oil are USA, China, Singapore, Germany, Netherland, and Philippine [2].
The products of citronella grass that being sold are usually the oil of Citronellol, Citronellal, Geraniol, the ester of Citronellol and Geraniol, as well as Isopulegol which are contained in the Citronella Oil [1,2]. These components are being isolated or purified by physical or chemical to increase its value (the color, clarity, physicochemical properties, and purity of the content) [2]. Java Citronella Oil is reported to have a high content of Geraniol, Citronellol, and Citronellal (14-34%, 13-15%, and 12-47%, respectively). Java Citronella Oil is widely used in perfumery, aromatherapy, massage oil, cosmetic, and insect repellent agent because the Java type is more aromatic than the Ceylon type [2,3]. Higher content of Geraniol and Citronellal in Citronella Oil is preferred because it can be used to produce the hydroxy Citronellal, Geranyl Acetate, and Menthol which have a more stable properties and play an important role in floral perfume materials in fragrance industry [2,3].
Citronella oil product derivatives.
Rhodinol
Citronellal is classified as the monoterpene aldehyde which play an important role in the synthesis of terpene derivatives. The reduction of Citronellal to produce the monoterpene alcohol of Citronellol can be done by using good reducing agent like NaBH4 or naturally converted by using microorganism. The conversion of Citronellal in Citronella Oil resulting higher amount of Citronellol, and together with Geraniol, this oil is now called Rhodinol Oil (an oil that contain higher amount of Citronellol and geraniol) [4]. Rhodinol is known to have a much flowery rose odor than Citronellol, and it is widely used in the perfumery industry because of its deeper, longer-lasting rose note aroma [5].
Ester of Rhodinol
As the first derivative product of Citronella oil, Citronellol and Geraniol can be converted into its ester through an esterification process, named Citronellyl Esters and Geranyl Esters. The organoleptic characteristic of terpinyl alcohol ester like Citronellyl Acetate and Geranyl Acetate consists of a sweet fruity flavor and rose-lavender aroma, which can be used for food, fragrance, and cosmetic [4,6]. These esters can be chemically synthesized using strong acids or naturally by using lipase catalysis.
Isopulegol and p-menthane-3,8-diol (PMD)
Isopulegol and p-menthane-3,8-diol (PMD) can be derived from Citronellal. Isopulegol has a peppermint odor and being synthesized cyclization by isomerization of Citronellal using homogenous catalyst or solid acid catalyst [7]. As a stable intermediate, Isopulegol then can be transformed to PMD (an active insect repellent agent) by a hydration-acid catalysis process [8]. The reaction is described in figure below [8,9]:
3,7-dimethyl-1-octanol
3,7-dimethyl-1-octanol can be made from Citronellol using nickel catalyst (with hydrogenation-nickel catalyst if using Citronellal as starting material) in high temperature [2]. This compound has been used as fragrance ingredients in decorative cosmetics, fine fragrances, shampoos, toilet soaps and other toiletries as well as in non-cosmetic products as it has a floral-rosy odor [10].
Hydroxy citronellal
Citronellal can be derived to produce Hydroxy Citronellal which has a lily-like aroma and widely used in perfumery industry. This compound cannot be directly produced from Citronellal using acid since it will cyclize the Citronellal to Isopulegol. Hence, the aldehyde group in citronellal needs to be protected to make it unreactive using ethanolamine. The hydrolysis of enamine in alkali system can produce the Hydroxy Citronellal [2].
Menthol
Menthol can be derived from Isopulegol as the secondary product derivatives of Citronellal. This compound is widely used in food, cosmetic, also pharmaceutical industries. Menthol can be naturally extracted from Mentha arvensis plant, or chemically synthesized by isomerization of Citronellal to Isopulegol followed with hydrogenation to obtain menthol [1]. The reaction is described in figure below [2, 11]:
Mitra Ayu offers varieties of Citronella Oil and Its Derivates, such as Citronella Oil, Citronellal, Citronellol, Geraniol, and Rhodinol. For more information about Mitra Ayu products, please see our Product List here.
Stay tune for exciting new and innovative products from Citronella Oil Derivatives, such as PMD, Citronellyl Acetate and Geranyl Acetate.
If you have any question, please contact us here or email us at info@ptmitraayu.com
References
[1] MEV (lipi.go.id)
