Chemical Compositions and Antioxidant Activity of Zingiber officinale Roscoe Essential Oils

Abstract

The aim of this research was to analyze the chemical compositions and antioxidant activity of essential oils from Thai immature ginger and mature ginger oils. Ginger was extracted by hydrodistillation and ethanol extraction. Both essential oils (hydrodistillation) and absolute (ethanol extraction) had the refractive index in the range of 1.348 to 1.500. Volatile compounds were identified by Gas ChromatographyMass Spectrometry (GC-MS). For hydrodistillation, zingiberene is the main compound found in essential oils from fresh immature and fresh mature gingers, with the relative peak areas of 16.52 and 20.30%, respectively. Essential oils from dried immature ginger and dried mature ginger are composed of camphene and geranial, respectively. For ethanolic extracts, the major compounds of dried immature ginger absolute and dried mature ginger absolute are zingiberene, with the relative peak areas of 31.81 and 36.50%, respectively. Moreover, more gingerol was found in dried immature ginger absolute than in dried mature ginger absolute. Essential oils from fresh mature ginger, dried mature ginger and dried mature ginger absolute exhibit antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical with the scavenging effect of 97.16, 88.79 and 84.81%, respectively. The anti-hydroxyl radical of the essential oil from dried mature ginger was 99.18%; this is followed by essential oils from fresh mature ginger (82.54%) and dried mature ginger absolute (76.00%). However, the essential oils and absolute from immature ginger are more than 80% effective against DPPH and hydroxyl radicals.