Plants essential oils

The separation capacity of a TLC method can be easily improved by use of a two-dimensional high performance TLC technique (2D HPTLC). Various plant essential oils (menthae, thymi, anisi, lavandulae, etc.) have been analysed by 2D TLC with florisil (magnesium silicate) as the adsorbent, using dichloromethane/ -heptane (4 6) in the first direction and ethyl acetate/n-heptane (1 9) in the second direction (69). 

Chemically, plant essential oils consist largely of mixtures of compounds known as terpenoids —small organic molecules with an immense diversity of structure. More than 35,000 different terpenoids are known. Some are open-chain molecules, and others contain rings some are hydrocarbons, and others contain oxygen. Hydrocarbon terpenoids, in particular, are known as terpenes, and all contain double bonds. For example ... 

Numerous additional examples of the evaluation of plant essential oils as insect repellents exist in the literature however, rarely are bioassay-guided fractionations performed to determine the constituents responsible for the activity of these plant essential oils. When attempts are made to identify active constituents, they are often of a non-systematic manner and usually focus on those constituents that are commercially available or the major constituents. Such approaches have the potential of missing unusual or novel structural types which could be highly active compounds with the potential for commercial development. 

Zhu J, Zeng XY, Liu T, Qian K, Han Y, Xue S, Tucker B, Schultz G, Coats J, Rotvley W, Zhang A, Adult repellency and larvicidal activity of five plant essential oils against moscgmocs, J Amer Mosquito Control Assoc 22-3 b— b22, 2006. 

Artemisia gmelini Weber ex Stechmann Bai Lian Guo (Levant wormseed) (whole plant) Essential oils, borneol, cineole, camphor, azulene, isovaleric acid, umbelliferone, scopoletin, genkwanin.48 Treat liver diseases, stop bleeding, arthritis, bronchitis. 

Centipeda minima (L.) A. Braun, et Ascherison Shi Wu Tou (Centipeda) (whole plant) Essential oil, myriogynine, alkaloids, glycosides, saponin.60 Antidotal, treat conjunctivitis, piles, malaria. 

Dracocephalum integrifolium L. Quao Ye Ging Lan (aerial plant) Essential oil, flavone glucoside.33 Antitussive, antiasthmatic, antiphlogistic, antibacterial. 

Elsholtzia argyi Lev. E. cristata Willd. E. feddei Lev. E. souliei Lev. E. splendens Nakai Xiang Xu (Aromatic madder) (whole plant) Essential oils, elsholtzia ketone, elsholtzianic acid, furylmethyl ketone, furylpropyl ketone, furylisobutyl ketone, furane, pinene, terpene.49 Stomachic, carminative, diuretic. 

Lysimachia barystachys Bunge. L. christinae Hance L. clethroides Duby L. davurica Ledeb. L. davurica Ledeb. f. latifolia Korsh. Jin Qian Chao (Loosestrife) (whole plant) Essential oils, 1-pinocamphone, 1-menthone, 1-pinene, limonene, 1,8-cineol, p-cymene.33 Diuretic, a choleretic agent, antibacterial. 

Aquatic plant essential oils from Lepidium meyenii TBA A,A,I,S,S (Tellez et al., 2002)... 

Halcon, L. L. (2002). Aromatherapy Therapeutic applications of plant essential oils. Minnesota Med. 85, 42-46. 

Dorman, H.J.D., Surai, P. and Deans, S.G. (2000) In vitro antioxidant activity of a number of plant essential oils and phytoconstituents. Journal of Essential Oil Research 12(2), 241-248. 

Park, K.I., Park, J.Y., Kim, K.H., Choi, K.S., Choi, I.H., Kim, C.S. and Shin, S.C. (2005) Nematicidal activity of plant essential oils and components from garlic (Allium sativum) and cinnamon (Cinnamomum verum) oils against the pine wood nematode (Bursaphelenchus xylophilus). Nematology 7, 767-774. 

Deans, S.C. and Ritchie, C. (1 987) Antibacterial properties of plant essential oils. International Journal of Food Microbiology 5, 1 65-1 80. 

Smith Palmer, A., Stewart, J. and Fyfe, L. (1998) Antimicrobial properties of plant essential oils and essence against five important food born pathogens. Letters in Applied Microbiology 26, 11 8-1 22. 

Yang, Y.C., Lee, S.H., Clark, J.M. and Ahn, Y.J. (2003a) Insecticidal activity of plant essential oils against Pediculus humanus capitis (Anoplura Pediculidae). Journal of Medical Entomology 41,699-704. 

Dorman, H.J.D., Deans, S.C., Noble, R.C. and Surai, P. (1995) Evaluation of in vitro plant essential oil as natural antioxidants. Journal of Essential Oil Research 7, 645-651. 

Pascual Villalobos (2003) found the potential of plant essential oils against stored-product beetle pests. Coriander oil (10 pi) showed activity against the bruchid Callosobruchus maculates, the cereal storage pest. 

Gamiz-Gracia, L. and de Castro, M.D.L. (2000) Continuous subcritical water extraction of medicinal plant essential oil comparison with conventional techniques. Talanta 51(6), 1179-1185. 

Friedman, M., Henika, P.R. and Mandrell, R.E. (2002) Bactericidal activities of plant essential oils and some of their isolated constituents against Campylobacter jejuni, Escherichia coli, Listeria monocytogenes and Salmonella enterica. Journal of Food Protection 65(1 0), 1 545-1 560. 

It has been known for centuries that rodistillation of many plant materials with steam, a tochnuiue called steam cfisttlfalion, produce a fragrant mature of liquids called plant essential oils. For thousands of years, such... 

McNair J. B. (1932) The interrelation between substances in plants essential oils and resins, cyanogen and oxalate. Am. J. Bot. 19, 255 - 272. 

The structures of some terpenes isolated from plant essential oils. 

Lis-Balchin, M. and Deans, S.G., Bioactivity of selected plant essential oils against Listeria monocytogenes, J. Appl. Microbiol., 82, 759, 1997. 

Extraction of Essential Oils from Plants. Essential oils are aromatic substances widely used in the perfume industry, the pharmaceutical sector, and the food and human nutrition field. They are mixtures of more than 200 compounds that can be grouped basically into two fractions a volatile fraction, which constitutes 90-95% of the whole oil, and a nonvolatile residue, which constitutes the remaining 5-10%. The isolation, concentration, and purification of essential oils have been important processes for many years, as a consequence of the widespread use of these compounds. The common methods used are mainly based on solvent extraction and steam distillation. SFE has been used for the extraction of essential oils from plants, in an attempt to avoid the drawbacks linked to conventional techniques (57). Such is the case with the extraction of flavor and fragrance compounds, such as those from rose (58), rosemary (59), peppermint (60), eucalyptus (61), and guajava (62). The on-line coupling of the extraction and separation ietermi-nation steps (by SFE-GC-FID) has been proposed successfully for the analysis of herbs (63) and for vetiver essential oil (64). 

The isoprenoids consist of terpenes and steroids. Terpenes are an enormous group of molecules that are found largely in the essential oils of plants. (Essential oils are plant extracts used for thousands of years in perfumes and medicines.) Steroids are derivatives of the hydrocarbon ring system of cholesterol. 

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