Comparative study of volatile compounds from genus Ocimum

American Journal of Applied Sciences, March, 2009 by S. Raseetha Vani, S.F. Cheng, C.H. Chuah

Essential oils found in Ocimum Basilicum belong to a variety of groups including monoterpene hydrocarbon, oxygenated monoterpenes (e.g., 1,8-cineole, L-camphor), sesquiterpene hydrocarbons (e.g., [beta]-cubebene, [gamma]-candinene) and aromatic compounds (e.g., methyl chavicol). From Table 1, the constituents from Ocimum Basilicum yielded methyl chavicol in abundance, supports previous findings (22), (24), (25), proving that this plant belongs to the phenolic chemotype. The amount of methyl chavicol, being high on April 2003, significantly decreased on June 2003, then increases gradually, until November 2003. Meanwhile, linalool was only present (April 2003) when methyl chavicol was relatively high.

The constituents obtained from Ocimum Sanctum (Table 2) were characterized by a high content of aromatic compounds, with methyl eugenol as the main constituent. As complementing the results with Ocimum Basilicum, the constituents found in Ocimum Sanctum belong to a significant group such as monoterpene hydrocarbon (limonene), oxygenated monoterpene (borneol), sesquiterpene hydrocarbons (e.g. [alpha]-copaene, [beta]-caryophyllene), oxygenated sesquiterpenes (elemol) and aromatic compounds (e.g. methyl chavicol, methyl eugenol). The composition of Ocimum Sanctum appears to be different from Ocimum Basilicum. Methyl chavicol is also present, but at very low percentage in all the months being investigated. The methyl eugenol content is high in September and October 2007 and then dropped extremely low on April and May 2008, then increases in June 2008. It is noticed that the amount of methyl eugenol and [beta]-caryophyllene are consistently vice-versa.

As indicated above, essential oils obtained from Ocimum Basilicum and Ocimum Sanctum species showed significant variability in their chemical composition. However, literature review showed variation between chemical compositions, depending of location, seasonal variation and stages of development. Ocimum Sanctum grown in India, in the field, under natural conditions (12) gave highest percentage of methyl eugenol in young leaves (5-10 days old). Previous publication suggests that essential oil may be isolated from Ocimum Sanctum (10) but with absolute seasonal variation. Eugenol is the main component of Ocimum Sanctum grown in Bangladesh (3), Germany (17), Cuba (18), Northeastern Brazil (19), methyl eugenol from India (11). Detailed morphological characters developed (20) can be used as reference to classify various types of Ocimum Sanctum. Meanwhile the essential oil of Ocimum Basilicum high during the winter season, giving high percentage of linalool (60.6%) (21), 52.6 and 58.26% estragole, from leaves and flowers, respectively, of Ocimum Basilicum (22). Higher solar irradiance level increased the contents of linalool and eugenol, whereas methyl eugenol was increased by lower irradiance in Ocimum Basilicum (23). Seven types of chemotypes presented by Isa Telci et al. (2006) also included methyl chavicol (68.3%) for Ocimum Basilicum varieties grown in Turkey (24). A research using three cultivars of Ocimum Basilicum conducted in Southern Italy (25) yielded high amount of methyl chavicol in Napoletano a foglia di lattuga type.