Isolation and Identification of the Principal Fungitoxic Component of Turmeric Essential Oil

Abstract

The essential oil of turmeric (Curcuma longa L.) rhizomes showed toxicity to seven fungi involved in deterioration of stored agricultural commodities. Depending upon the fungus, in vitro growth inhibition varied from 36%-77% at 0.1%. Aspergillus flavus, Fusarium semitectum, Colletotrichum gloeosporioides and C. musae were most sensitive with growth inhibition of over 70%. The bioautography of the oil produced only one antifungal band representing 40% of the total oil. The fractionation of this band by reverse phase preparative HPLC (high performance liquid chromatography) yielded two peaks, in the proportion of 57.9% and 42.1%. The larger peak had only one compound, which was identified as ar-turmerone by MS (mass spectrometry) and NMR (nuclear magnetic resonance) spectra. The smaller peak contained two compounds, in the proportion of 31% and 69%, which were identified as β-turmer-one and ar-turmerone, respectively. Thus ar-turmerone constituted 87% of the fungitoxic component of the oil. The purified ar-turmerone showed antifungal activity similar to the crude oil.