Antibacterial Activity of Some Essential Oils Sophon Roengsumran*, Amorn Petsom*, Suthep Thaniyavarn**, Surachai Pompakakul*, and Suntree Khantahiran*. Chemistry Department, Faculty of Science, Chulalongkom University, Bangkok 10330, Thailand... Microbiology Department, Faculty of Science, Chulalongkom University, Bangkok 10330, Thailand.
INTRODUCTION Historically, medicinal plants or herbs were widely used in traditional medicine and as spices or seasonings. Medicinal plants have also played an important role in the development of modem medicines. Despite the development of antibiotics, bacterial infections are still of medical concern: the fact that drug resistant strains (Le., via drug resistant transfer factor) are commonly observed, especially in the case of nosocomial infections, still poses a major problem in infectious medicine. Antibiotics are not the only available agent for combating infectious agents; in fact chemicals, especially those from natural products (herbal medicine) have been extensively used for this purpose since ancient times. The latter are of progressively greater interest due to their availability and fewer side effects or toxicity in comparison to available antibiotics. Furthermore, these compounds can be used advantageously without fear of the development of drug resistance as in antibiotics. Essential oils of various medicinal plant parts have also been used as fragrance in perfumes, soaps and other personal care products. These oils might have antibacterial activity in addition to their primary function of providing a pleasant odor. Previously, the antibacterial activity of essential oils has been reported rather extensively.i The present study provides data on antibacterial activity of various essential oils isolated from various parts of thirty-one medicinal plants or herbs that are available in Thailand. This paper also reports the chemical constituents of some essential oils which show antibacterial activity. EXPERIMENTAL Plant Materials Materials from most plant parts were used in this study: fruit, peel, bark, leaves, wood, seeds, dried fruits, flowers and roots. Most plants were collected from the central part of Thailand, except cinnamon, oregano and summer thyme which were collected from the Royal Project, Doy Angkhang, Chiangmai province, Thailand. Isolation Procedure The plant materials (3OOg)were mixed with a suitable amount of water and hydrodistilled in glass apparatus for about 3 hours. The oil was separated, dried over anhydrous sodium sulfate and.stored in a refrigerator until ready for investigation. Some essential oils were gifts from the collection of KM. Interlab Co. Cinnamaldehyde and thymol were obtained from Fluka and were distilled before use. Analytical Procedure The constituents of the essential oils were analyzed using a Fisons GC 8000 IMS Trio 2000 with a DB-WAX fused silica column (30 m x 0.22 mm) as a stationary phase with helium carrier gas and a flow rate of 46 cm/s. The oven temperature was held at 60 C for 5 minutes and increased to 240 C for 20 minutes while the injector and GCI MS interface were kept at 250 C. The mass spectrum of each component was taken at 70 ev under EI mode. The scanning speed was 400 amul see with a 0.1 s interscan time. The mass range was monitored from 25 to 650 amu. Identification of individual compounds was achieved using u.s. National Institute for Standards and Technology (NIST) library search software. The NIST registry of mass spectral data was used together with mass spectra from 71 standard compounds acquired under the same conditions. The compositions of cinnamon oil, oregano oil and summer thyme oil were analyzed and the results are presented in Table 2. Microbiological Procedure, Cultures Test organisms employed in the study, Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa, were clinically isolated at Chulalongkorn Hospital while Streptococcus pyogenes and Salmonella typhi were obtained from.. the National Institute of Health, Ministry of Health. All organisms were maintained on either BHI or. nutrient agar. Agar Diffusion Test Tests were performed by the standard method recommended by Bauer.2 Results are expressed in terms of the inhibition zone surrounding the 6 mm disc. (Inhibition zone = diameter in mm of the zone from the center ofdisc - diameter in mm of disc) Minimum Inhibition Concentration The MIC tests were carried out by the macrodilution broth method. Briefly, 10% (v Iv) of essential oil in Tween80 was diluted into a 1%
RESULTS AND DISCUSSION