INTRODUCTION
Almost everybody knows the odour of freshly cut grass, which is due to the chemical compounds cis- or (Z)-3-hexenol and trans- or (E)-2-hexenal, also called leaf alcohol and leaf aldehyde respectively. Less known, however, is the scent of hay, which is due to the compounds coumarin and dihydrocoumarin. These compounds are formed from coumarinic acid derivatives during drying of the grass. In the northern hemisphere we know a grass species called "scenting grass", which also possesses the characteristic coumarin odour. Furthermore, in our hemisphere we don't know a lot of odoriferous grasses, in contrary to the tropical countries, where various scenting grasses exist.
DISCUSSION
The plant family of the grasses, the Poaceae, formerly called the Gramineae, is one of the most extensive plant families in the world. This family consists of more than 500 genera with over 5000 species. To this family belongs a group of aromatic tropical grasses of the genus Cymbopogon, which comprises about 40 species. Some of the Cympobogon species are important for the production of essential oils.
The most important essential oils isolated from the Cymbopogon species are:
Citronella oils from Cympobogon nardus (L.) Rendle and from Cymbopogon winterianus Jowitt.
The oil from Cympobogon nardus is commercially known as Ceylon-type citronella oil and the oil from Cymbopogon winterianus is called Java citronella oil. Ceylon citronella oil consists of ± 60% monoterpene alcohols (calculated as geraniol) and of ± 10% aldehydes. The oil has a warm floral, woody odour with a rose nuance and a fresh topnote of citronellal, more pleasant than the Java type. Ceylon-type oil is useful in fresh floral compounds for all purposes. Java citronella oil contains not less than 35% monoterpene alcohols and a minimum of 35% aldehydes, mainly citronellal. Java-type oil has a fresh, citrusy, somewhat lemon-like odour; it has the image of a cheap perfumery product for household soap, but in low dosage it can impart freshness even in high-class perfume compounds.
Jamrosa oil from the hybrid Cymbopogon nardus var. confertiflorus x Cymbopogon jwarancusa.
Jamrosa oil consists of ± 75% of geraniol and ± 20% of geranyl acetate. The oil has a rosy-grassy odour with a terpenic bynote, which is not so sweet rosy as palmarosa oil. Nevertheless jamrosa oil is useful in perfume compounds with a rose character.
Lemongrass oil from Cymbopogon citratus (DC) Stapf or Cymbopogon flexuosus Stapf.
Lemongrass oil contains ± 70% citral (geranial and neral). Lemongrass oil has a fresh, strongly citrusy, lemon-like, and pungent odour with herbal and leafy aspects; it is applied in all citrusy perfume compounds, especially for household products.
Palmarosa oil from Cymbopogon martinii (Roxb.) Stapf var. motia, also known as Cymbopogon martinii (Roxb.) Wats var. martinii.
Palmarosa oil consists for ± 80% of geraniol. Palmarosa oil has a sweet floral, rose- and geraniol-like odour with herbal aspects. It has also a note of rye bread, tea and clary sage. The oil is an excellent extender in all floral, rose-like, perfume compounds.
Gingergrass oil from Cymbopogon martinii Stapf., var. sofia.
Gingergrass oil contains ± 35% monoterpene hydrocarbons, mainly limonene, and ± 50% menthadienols. Gingergrass oil has a harsh, terpeny, somewhat fatty, herbal and cumin-like odour with a rose nuance and a woody undertone. The oil is useful in herbal compounds for cosmetic purposes, such as shampoos.
Reprinted by Leffingwell & Associates, 2006, with Permission