Exp t 610 Isolation of Volatile Oils from Spices by Steam Distillation and Bioassay for Biological Activity Adapted from William H Miles Department of Chemistry Lafayette College Easton PA 18042 milesw mail lafayette edu and Patricia M Smiley Southern Lehigh High School 5800 Main Street Center Valley PA 18034 smileyp solehi k12 pa us J Chem Ed 2002 79 90 Introduction Activities You will use steam distillation to separate any volatile oils You will also carry out liquid liquid extraction of the steam distillate to separate the neutral acidic and basic components You may need to prepare sterile agar plates and inoculate them with Bacillus Cereus bacteria and incubate them to test biological activity Samples of the components you isolated will be tested for antibacterial activity You will use GC and GC MS to characterize your volatile oils Modeling the Drug Discovery Process Chemistry and Medicine Since ancient times humankind has sought medicines from nature Quinine the antimalarial from the bark of the cinchona tree and reserpine the antidepressant from the Indian plant Rauwolfia serpentina represent two of the more famous natural products used in modern medicine Today pharmaceutical companies use several approaches for the discovery of new compounds to treat human illness including the screening of natural products derived from bacteria fungi plants or animals No not puppies or even mice but animals like slugs or sponges simple multi cellular bottom dwelling animals called Porifera For example extraction of a marine sponge with an organic solvent can yield a complex mixture of organic compounds which can then be tested for biological activity or bioassayed If the mixture shows promising biological activity the components of the complex mixture may be separated and purified When further testing identifies the active component its chemical structure can be determined using modern spectroscopic techniques IR NMR Mass Spectrometry X ray crystallography Even if the new compound has side effects that render it unsuitable as a drug candidate the pharmaceutical chemists will use the compound as a guide for the synthesis of new drug candidates with similar structures The synthesis of organic compounds whether of natural products or of unnatural products compounds that are not found in nature has been a primary goal of organic chemists Some of the first synthetic compounds produced industrially were dyes fragrances and flavorings It was not until the twentieth century that synthetic drugs were successfully developed The synthesis of the antisyphilitic drug arsphenamine Compound 606 by Ehrlich in 1910 was a dramatic demonstration of the power of chemistry to attack a medical problem Yes arsphenamine contains arsenic Not good stuff but remember you re dying of syphilis so you can t be fussy Since then many new compounds including biologically active compounds found in nature have been synthesized in the laboratory and have become useful drugs For example Ritalin is used for the treatment of attention deficit disorder ADD 5 fluorouracil is a potent anti cancer drug and L DOPA is used to treat Parkinson s disease Distillation page 1 Essential oils which are isolated by steam distillation of volatile organic compounds present in plants and animals have a long and rich history in medicine Typically complex mixtures of organic compounds essential oils have been used to treat a variety of illnesses for thousands of years In some cases these essential oils do have therapeutic utility by modern medical standards The essential oils of cloves and thyme contain phenolic compounds organic molecules that have an OH group attached to an aromatic ring which are effective antiseptics germ killers Even before the establishment of the germ theory the antiseptic power of both thyme oil and clove oil was recognized Joseph Lister whose name is immortalized by the mouthwash Listerine used synthetic phenol carbolic acid to prevent infection during surgical procedures in the midnineteenth century revolutionizing the medical treatment of wounds He recognized that antiseptic chemicals can prevent infection and proved the value of some of the old herbal remedies Phenolic compounds both synthetic phenol and thyme oil were used as antiseptics until World War I The clove tree produces flower buds which when harvested and dried become the familiar spice of the same name It has long been known that cloves contain an ingredient with an anesthetic property that is particularly effective against dental pain Before modern medicine developed better remedies people often chewed on cloves to dull the pain of a toothache The active compound responsible for this effect is found in the essential oil of cloves which makes up approximately 16 18 of the clove by weight The major component of this oil is the compound eugenol Eugenol has a boiling point of 254 C It would be difficult to isolate this oil by simple distillation since this high temperature could lead to its decomposition as well as the decomposition of other components of the cloves However eugenol can be isolated relatively easily from cloves using the technique of steam distillation Once the aqueous distillate containing the clove oil has been obtained the oil can be separated from the water by extraction into the organic solvent dichloromethane The dried fruit of cumin Cuminum cynimum L a small shrub cultivated in eastern Europe and India is an important seasoning in curries goulashes and sausages It is also a major component of chili powder used in Mexican food The major volatile constituent of cumin is p isopropylbenzaldehyde cuminaldehyde Cumin oil also contains limonene and other compounds which contribute to the aroma of this condiment The Isolation of Organic Compounds As you know functional groups give the molecules distinctive chemical reactivity as well as play a role in the physical properties compounds have Different physical properties allow the separation of one organic molecule from another In some cases separations can be based on the solubility of the compound in a given organic solvent so that a compound can be recrystallized as you learned in the recrystallization technique experiment As you will learn in this techniques experiment organic compounds with appreciable vapor pressure can be separated by distillation at atmospheric pressure or if their vapor Distillation page 2 pressure is low steam distillation or vacuum distillation at reduced pressure