The spread of drug resistant pathogens is one of the most serious threats to successful treatment of microbial diseases. Down the ages essential oils and other extracts of plants have evoked interest as sources of natural products. They have been screened for their potential uses as alternative remedies for the treatment of many infectious diseases [1
]. World Health Organization (WHO) noted that majority of the world's population depends on traditional medicine for primary healthcare. Medicinal and aromatic plants which are widely used as medicine and constitute a major source of natural organic compounds.
Essential oils have been shown to possess antibacterial, antifungal, antiviral insecticidal and antioxidant properties [2
]. Some oils have been used in cancer treatment [4
]. Some other oils have been used in food preservation [5
], aromatherapy [6
] and fragrance industries [7
]. Essential oils are a rich source of biologically active compounds. There has been an increased interest in looking at antimicrobial properties of extracts from aromatic plants particularly essential oils [8
]. Therefore, it is reasonable to expect a variety of plant compounds in these oils with specific as well as general antimicrobial activity and antibiotic potential [9
Essential oils (also called volatile oils) are aromatic oily liquids obtained from plant materials (flowers, buds, seeds, leaves, twigs, bark, herbs, wood, fruits and roots). They can be obtained by expression, fermentation or extraction but the method of steam distillation is most commonly used for commercial production. An estimated 3000 essential oils are known, of which 300 are commercially important in fragrance market [7
]. Essential oils are complex mixers comprising many single compounds. Chemically they are derived from terpenes and their oxygenated compounds. Each of these constituents contributes to the beneficial or adverse effects.
Essential oils such as aniseed, calamus, camphor, cedarwood, cinnamon, citronella, clove, eucalyptus, geranium, lavender, lemon, lemongrass, lime, mint, nutmeg, orange, palmarosa, rosemary, basil, vetiver and wintergreen have been traditionally used by people for various purposes in different parts of the world (Table ). Cinnamon, clove and rosemary oils had shown antibacterial and antifungal activity [10
]; cinnamon oil also possesses antidiabetic property [11
]. Anti-inflammatory activity has been found in basil [12
]. Lemon and rosemary oils possess antioxidant property [13
]. Peppermint and orange oils have shown anticancer activity [15
]. Citronella oil has shown inhibitory effect on biodegrading and storage-contaminating fungi [17
]. Lime oil has shown immunomodulatory effect in humans [16
]. Lavender oil has shown antibacterial and antifungal activity; it was also found to be effective to treat burns and insect bites [18
List of selected essential oils and their properties.
In spite of all the information available on the 21 oils selected for this study, we were not able to find antibacterial activity for all those oils. Hence this study was undertaken with the intention of finding out the efficacy of these essential oils as antimicrobial agents for commercial purposes.