Abstract:
The present study was conducted to evaluate the antibacterial and antioxidant activities of essential oil obtained by steam distillation, hydrodistillation and two solvent extractions (petroleum ether and ethanol) from five Zingiberaceae species; ginger (Zingiber officinale Roscoe.), galanga (Alpinia galanga Sw.), turmeric (Curcuma longa L.), kaempferia (Boesenbergia pandurata Holtt.) and
bastard cardamom (Amomum xanthioides Wall.). Volatile compounds of all extracts were analyzed by gas chromatography-mass spectrometry (GC-MS). Major compositions of ginger were zingiberene and farnesene and of turmeric were turmerone and curlone. In galanga and bastard cardamom, methyl chavicol was the major compound, extracted by hydrodistillation and fraeseol and anethole were major compounds, extracted by ethanol. Kaempferia essential oil obtained from hydrodistillation and solvent extraction, consisted of ?-terpinene and geraniol as major compounds, respectively. Although ethanol extraction was the best extraction procedure to extract essential oil from all ginger family, petroleum ether was good for extract the essential oil from bastard cardamom. Effectiveness of essential oil on radical-scavenging was tested by and DPPH (2,2-diphenyl-1- picrylhydrazyl) free radical scavenging method. It was found that ginger extracted by ethanol (ginger-ED) and waste ginger extracted by ethanol (ginger-EW) showed a high scavenging effect to free radical at 23.75 and 23.01, respectively. It was also found that the high concentration of plant extracted, the high scavenging effect to free radical. When antioxidant properties were tested by ?-carotene bleaching method, results showed that turmeric extracted (turmeric-ED) and waste turmeric extracted by ethanol (turmeric-EW) had a high antioxidant activity at 86.2 and 78.21, respectively. Total phenolic compounds were found high in turmeric-EW, turmeric-ED, ginger-ED and ginger-EW at 38.41, 29.62, 24.22 and 23.55 mg/ g of extracted, respectively. Antibacterial property of essential oil against four bacteria, Escherichia coli, Staphylococcus
aureus, Bacillus cereus and Listeria monocytogenes was performed. Results showed that essential oil obtained by hydrodistillation extraction of kaempferia and bastard cardamom could inhibit growth of all tested bacteria. The other 18 essential oils did not have an activity against E. coli. Essential oil of ginger by hydrodistillation had the highest efficiency against three positive strains
of bacteria (S. aureus, B. cereus and L. monocytogenes). Furthermore, antioxidant activity by measuring peroxide value and TBA value, was studied in soybean oil at 98?C. It was found that turmeric-ED could inhibit at highest activity of primary product of free radical measured as peroxide value of 32 milliequivalentperoxide/1 kg of soybean oil. However, it was not found an
inhibition of secondary product of antioxidant activity in soybean oil.