Citronella is a joint name of more than 55 aromatic plants in the Cymbopogon family. Nearly all of them share a typical fresh lemon fragrance and is called lemongrass. It has long been cultivated in India and Malaysia, used as an indispensable flavoring for curries, soups and liquors in Southeast Asia. Except for direct use in cooking, the derivatives of citronella are used in a wide range of products.
The direct product of citronella is citronella oil which is distilled from the whole grass of citronella by steam distillation. Cymbopogon winteranus jowitt and Cymbopogon nardus growing in tropical areas are the two main sources used in fragrance synthesis. The high value and demand make countries like Java, Sri Lanka and India grow them massively and commercially.
Citronella oil has distinctive benefits for human beings in daily care. The best-known effect is mosquito repellent. According to research published in 2011 on Tropical Medicine & International Health, the oil can provide protection against mosquitoes for 2-3 hours. Another notable value of citronella oil lies in its powerful anti-fungal property which leads it to the pharmaceutical world. Largely due to the properties of its natural compounds, such as isoeugenol methyl ether, citronella oil helps prevent fungal growth, heal wounds and reduce infections in colon, bladder and kidneys. It is also commonly used in aromatherapy as it helps to relieve anxiety and gives a sense of relief. Further, citronella oil can be used in the extraction of citronellal, citronellol, geraniol, citral and their acetate.
Geranyl Formate and Geranyl Butyrate
Derived from geraniol, geranyl formate and geranyl butyrate have a similar fresh green rosy notes. Geranyl formate plays a role in plants as alarm pheromone that warms other individuals of the coming danger, which is probably the reason why its fragrance lasts up to 24 hours. Both of them are employed in flavor and fragrance formulation for lemon, rose, neroli and other spices in cosmetics, soaps and other daily care products.
Geranyl formate is produced by esterification. Using formic acid and geraniol as raw materials, the esterification process is carried out in the presence of anhydrous calcium chloride and obtained by neutralization, washing and drying. However, the synthesized aroma is strong and irritant that usually only a small dosage is recommended.
Compared to geranyl formate, geranyl butyrate gets some fruity odor which brings it wider use in the food industry to create banana and grape flavor. In industrial production, it is obtained by direct esterification of geraniol and butyric acid in the azeotropic state.
Citronellyl formate is derived from citronellol. It is obtained by the esterification of formic acid and citronellol. With sweet rose and bay leaf-like aroma, the market of citronellyl formate is driven mainly by the perfumery and personal care industry. It also finds application in food and beverage industry as flavor agent for fruity, peach, berry and apple flavors. Over the past few years, the demand of citronellyl formate is rising as it is considered a relatively healthy additive for edible products. What’s more, researches like Studies on the Chemical Components and Anti-Tumour Action of the Volatile Oils From Pelargonium Graveoleus determine the anti-tumor and anti-fungal properties of citronellyl formate, which helps it entering new medical field.
Isomethyl Ionone and Beta-Ionone
Isomethyl ionone and beta-ionone are produced from citral, the former by reaction with butanone under the strong base and high temperature and the latter by the condensation reaction of with acetone using potassium hydroxide as agent. With their characteristic fragrance, they are applied as edible spices allowed in the preparation of raspberry flavor and other berry flavors. In addition to the application in food and perfumery, both of them find greater value in pharmaceutics as intermediate. Beta-ionone is mainly applied as an important raw material in the procedure, especially for the production of vitamin A, vitamin E and carotene. Some recent researches demonstrate the anti-proliferative, anti-metastatic and apoptosis induction properties of beta-ionone in vitro and in vivo that can probably be used in cancer care or even treatment in the near future.
Elemol is a sesquiterpene found in the citronella oil and olive oil from Java and can be extracted from them. Like other derivatives of citronella, it is widely used in cosmetic, personal care and household products as a fixative or dressing agent. Besides, pharmaceutical use of it is expanding as well. Present studies suggest that elemol may have therapeutic potential in the treatment of atopic dermatitis owe to its immunosuppressive effects. The experiments of taking it as tick repellent and mosquito repellent also help exploited new way for its application.
As more efficacies of citronella derivatives have been discovered, for example, antibacterial, antispasmodic, digestive stimulant, anti-inflammatory, antifungal, insecticide, the main effective components of citronella are applied in food, cosmetic, pharmaceutical etc., showing enormous vitality in different fields.