Changes in essential oil, kava pyrones and total phenolics of Alpinia zerumbet (Pers.) B.L. Burtt. & R.M. Sm. leaves exposed to copper sulphate

Essential oils, total phenolics, dihydro-5,6-dehydrokawain (DDK) and antioxidant and antibacterial activities were investigated in Alpinia zerumbet (Pers.) B.L. Burtt. & R.M. Sm. plants, that had been sprayed with copper sulphate 24 h beforehand. Ethyl acetate extract of copper-treated plants contained increased levels of total phenolics, had higher antioxidant activity assayed by DPPH and β-carotene bleaching methods and exhibited higher antibacterial activity against Bacillus cereus than that of non-treated plants. Contents of DDK, vanillin and cinnamic acid were significantly higher in chloroform and ethyl acetate extracts of A. zerumbet plants following exposure to copper. Volatile components that increased after copper treatment include: 1,8-cineol, camphor, borneol, and terpinene-4-ol. Foliar application of copper sulphate may regulate the antioxidant compounds in A. zerumbet plants, influencing its antioxidant and antibacterial activities.