Phytochemical, antioxidant, and antibacterial analysis of essential oils from <i>Zingiber officinale Roscoe</i>(Ginger) and <i>Curcuma long Linn.</i>(Turmeric)

Abstract

This study was conducted to characterize and compare the phytochemistry, antibacterial and antioxidant activities of essential oils extracted from the rhizomes of <i>Zingiber officinale Roscoe</i> (ginger) and <i>Curcuma longa Linn. </i>(turmeric). Percent yields in the steam distillation of ginger and turmeric were 0.42±0.02% and 0.43± 0.02%, respectively. Qualitative phytochemical screening showed that both essential oils are positive for flavonoids, phenols, saponins, terpenoids, tannins, and quinones. Antibacterial activity was tested against Gram-positive <i>Staphylococcus aureus</i> and Gram-negative <i>Escherichia coli</i> using 100%, 75%, 50%, and 25% (v/v) essential oil in ethanol with positive control tetracycline and negative control ethanol. It was determined that <i>C. longa</i> did not have antibacterial activity against both bacteria while <i>Z. officinale</i> had “moderately inhibitory” to “strongly inhibitory” activity against <i>S. aureus</i> with zone of inhibition (ZOI) from 17.67±1.53 mm to 23.67±0.58 mm and “weakly inhibitory” to “moderately inhibitory” activity against <i>E. coli</i> (ZOI from 12.33±1.15 mm to 15.67±2.08 mm). The standard antibiotic tetracycline also showed “moderately inhibitory” activity against both <i>S. aureus</i> (ZOl = 19.00±0.89 mm) and <i>E. coli</i> (ZOI = 17.33±1.21 mm). Antioxidant activity was determined by DPPH free radical inhibition. Highest % DPPH free radical inhibition was exhibited by the standard antioxidant ascorbic acid (92.98%), followed by <i>C. longa</i> essential oil (88.74%), and <i>Z. officinale</i> (76.30%).