Clove essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS) on an Agilent 7890 instrument with split stream injector at 270°C. The HP-5 capillary column was 30 m × 0.32 mm with a 0.25 mm film of a cross-linked methyl (95%) phenyl (5%) polysiloxane stationary phase. The initial oven temperature was held at 60°C for 1 min and increased at 10°C/min to 180°C held for 1 min and then ramped at 20°C/min to 280°C maintained for 15 min. The injection volume was 1µl (diluted 1:100 in acetone), and the split ratio was 1:10.