Composition of the Essential Oils from Flowers and Leaves of Vervain [Aloysia triphylla (L'Herit.) Britton] Grown in Portugal

Journal of Essential Oil Research: JEOR, Jan/Feb 2005 by Santos-Gomes, Paula C, Fernandes-Ferreira, Manuel, Vicente, Ana M S

Abstract

A total of 63 compounds were identified in hydrodistillates from flowers and leaves of vervain plants [Aloysia triphylla (L'Herit.) Britton] grown in Portugal. The three main essential oil compounds present either in flowers or in leaves were geranial (26.8-38.3%), neral (20.8-29.6%), and limonene (5.7-20.6%). 1-Octene, 1-octen-3-ol, p-cymene, (Z)-β-ocimene, and trans-carveol, identified in the flower oil, were not found in the leaf oil of the same plant. However, p-cymene and trans-carveol were found in the leaf oils of young cultivated plants. On the other hand, β-citronellene, β-pinene, neryl acetate, and trans-calamenene, present in the leaf oils, were not found in the flower oils. The main compound groups and percentages found in oils were monoterpene hydrocarbons (29.9 and 22.3%), oxygen-containing monoterpenes (56.9 and 59.0%), sesquiterpene hydrocarbons (6.5 and 6.8%), and oxygen-containing sesquiterpenes (3.0 and 4.8%) (flowers and leaves, respectively). The percentage of the total oxygen-containing monoterpenes, especially aldehydes, in the leaf oils of young cultivated plants, increased from July to December in inverse correlation with that of monoterpene hydrocarbons. The comparison with previous studies performed by other authors points to a significant variation in the chemical composition of vervain oil depending from the origin of the plants.

Key Word Index

Aloysia triphylla, Verbenaceae, lemon verbena, vervain, essential oil composition, limonene, neral, geranial.

Introduction

Vervain- or lemon verbena [Aloysiatriphylla (L'Herit.) Britton, A. citriodora (Cav.) Ort.,Lippia citriodora (Ort.) HBK, L. triphylla O. Kze., Verbena citriodora Cav., V. triphylla L'Herit.] ( Verbenaceae)- grows spontaneously in South America (Chile, Argentina, Uruguay and Peru) and was introduced in Europe at the end of the 17th century. Since then, it has been cultivated in some countries of southern Europe, namely Spain and Italy, and countries in North Africa, namely Morocco and Tunisia, and India as well. In these areas, the leaves are largely used in herbal teas for their aromatic, digestive and antispasmodic properties. In the United States, vervain is listed as Generally Regarded As Safe (GRAS) for human consumption in alcoholic beverages.

The traditional ethnobotanical applications of vervain include the respective uses as folk remedy in treatments of asthma, spasms, cold, fever, flatulence, colic, diarrhoea, indigestion, insomnia, and anxiety (1-3). In a recent review on the traditional uses, chemistry and pharmacology of the Lippia genus, vervain was reported as being used as analgesic, antiinflammatory and/or antipyretic remedies (4). Other applications of vervain include the uses of the respective leaves for flavoring of beverages and as seasoning for food preparations (4). The analgesic activity of vervain was confirmed by pharmacological assays and the respective active compound was isolated by methanol extraction, followed by partitioning with ethyl acetate, and identified as being acteoside (verbascoside) which additionally exhibited a weak sedation by the oral administration (5). This compound was found as one of the habitual main polyphenolic constituents from the vervain tea, together with some essential oil constituents (6). However, the sedative and anxiolytic activities of vervain infusions were not confirmed in clinic trials (4 and references therein).

The Good Manufacturing Practices on Medicinal Plants requires higher and higher quality control, based on chemical characterization, either the raw materials or the finished products. The chemical characterization of vervain is made, in some Pharmacopoeias (7), by the TLC detection of citral (mixture of the isomers neral and geranial). However, neral and geranial are widespread in medicinal and aromatic plants and are among the major compounds in essential oils of different plant species. On the other hand in some European countries, medicinal and aromatic plants are often sold as mixtures. Therefore, to guarantee the genuine vervain origin of a given sample of plant biomass or respective products, the search for citral is insufficient. A suitable quality control requires that raw materials of each species and respective products must be characterized not by one chemical marker but by the highest possible number of chemical compounds or a genuinely unique combination of several marker compounds.

Flavonoid compounds are good candidates as chemical markers and some of them have been described (2) and identified in vervain raw material and derived products (6,8-10). However, as vervain is cultivated and commercialized mainly to be used as aromatic in herbal teas, due to their agreeable scent, the most suitable chemical markers may continue to be based in the composition of the essential oils obtained from the respective raw material, such as it is used in the preparation of the infusions. The chemical composition of the oils from A. trlphylla has been studied and reviewed (11-13). However, notwithstanding the repeated reference to the presence of some major compounds namely, neral, geranial, limonene, 1,8-cineole, geraniol, β-caryophyllene, and spathulenol (6) different lists of oil compounds from this species have been reported (6,14,15) making difficult the definition of a standard quality profile. Most of the composition studies have been done with oils isolated from dried leaves as mentioned in the French Pharmacopoeia (7). However, according to some authors, other than leaves vervain parts can be used, namely flowering tops (2).