Analysis of the Essential Oil of Sweet Basil

Ocimum basilicum L. (Lamiaceae) also known as sweet basil or basil is commonly used as a spice and a typical ingredient of the healthy diet. It is cultivated in several regions Asia, Africa, South America, and the Mediterranean. The essential oils of this herb are an excellent source of many volatiles and aromatic chemical products extensively used in food, perfume products and cosmetics, as well as in the traditional medicine. Sweet basil essential oil, obtained from its leaves, has demonstrated to have antimicrobial, antifungal and insect-repelling, anticonvulsant, hypnotic, and antioxidant, activities. The researchers from different parts of world have reported chemical composition of the leaf essential oil of O. basilicum and several chemotypes have been reported. The huge diversity was recorded in sweet basil volatile profile from different regions; for instance linalool 1, 8-cineole and eugenol were main compounds in Egyptian sweet basil while in southern India, the main components were (E)-methyl cinnamate, linalool and camphor. However, sweet basil cultivated in the Mongolian desert, reported to possess linalool -bergamotene and methyl chavicol as major compounds.

The major compounds of Algeria basil leaves were linalool, linalyl acetate and elemol. On contrary Greece sweet basil enriched in 1, 8-cineole/ eucalyptol, α-pinene and camphor, while α-terpineol and β-caryophyllene were dominant volatiles in basil plants from Burkina Faso. Geraniol, and 1, 8-cineole were the major compounds reported from Oman basil, as well as Poland basil. Among 12 varieties of Ocimum from Colombia, ten were characterized by the presence of a high percentage of methyl cinnamate. Similarly (E)-methyl cinnamate and (Z)-methyl cinnamate were recorded as major compounds from French Polynesia basil leaf.

Another study on a germplasm collection of 18 Ocimum basilicum accessions from Spain, methyl chavicol and linalool were predominated. Methyl chavicol was also a main principal compound basils from Turkey, Iran, Thailand. Interestingly, Purkayastha reported that the camphor, followed by limonene and β-selinene were the major compounds in Northeast Indian sweet basil. In conclusion, sweet basil leaf contains main components viz. , terpenes (monoterpene and sesquiterpene) and phenylpropenes. The linalool and 1, 8 cineole are among major monoterpenes and germacrene D and R-bergamotene are predominating sesquiterpenes while the major phenylpropenes are eugenol and methylchavicol.

Various environmental factors are known to influence the essential oil content and composition in sweet basil including; tissue tested), phenophase, season, abiotic factors; salinity, water stress, Solar irradiance, light quality temperature, drying and storage methods and extraction methods. Fischer et al. (2011) analysed leaves from different positions on the main stem and found higher levels of eugenol in younger leaves while in older leaves methyl-eugenol levels predominated. In case of linalool was lower in mature leaves than in younger leaves. They reported that the sweet basil aroma is significantly affected by the position of the leaf rather than by the leaf age or maturation process. Furthermore, for better understanding of the molecular mechanisms that control volatile compounds differentiation in sweet basil, genes involved in the biosynthesis of various volatiles have been reported and characterized including eugenol; linalool, terpinolene, fenchol, β-Myrcene, cadinene, selinene, zingiberene, germacrene-D; methyl chavicol and methyl eugenol; geraniol; amyrin.

Sweet basil plants, synthesize phenylpropanoids and terpenes in the four-celled peltate glands found on both sides of the leaves and store these compounds in the sac surrounding the gland. The developmental regulation of phenylpropene pathway was reported by Gang et al. in sweet basil where they found higher level of chavicol O-methyltransferase, activity in younger leaves than mature, and basal regions of both young and mature tissues contained greater transcript levels than apical regions.