5%, respectively ( Table 1 and Table 2). Statistical analysis showed that the essential oil exhibited a higher antiaflatoxigenic activity compared to curcumin in AFB1 and AFB2-producing A. flavus (AFB1 = 45.75 and 35.75 μg/mL for essential oil and curcumin, respectively; AFB2 = 45.5 μg/mL and 34.5 μg/mL for essential oil and curcumin, respectively). Table 3 and Fig. 2 show the major components of essential oil: ar-turmerone (33.2%), α-turmerone Caspase inhibitor (23.5%) and β-turmerone (22.7%). Similar results were obtained by Singh et al., 2002 and Jayaprakasha et al., 2005 and Péret-Almeida et al. (2008). Dhingra et al. (2007) showed that ar-turmerone, which is one of the main components of the
oil, mediates the fungitoxic component of essential oil. Gill, Delaquis, Russo, and Holley (2002) showed that essential oils, as a whole, exhibit higher antimicrobial activity than their major compounds individually. This finding suggested that minor compounds might have an important
additive or synergistic role. Therefore, additional studies on the components of the essential oil of C. longa will be necessary to elucidate its antiaflatoxigenic action. The mechanism of inhibition effect of the essential oil of C. longa L. and curcumin for aflatoxins production may be related to inhibition of the ternary steps of aflatoxins biosynthesis involving lipid peroxidation and oxygenation. Hua, Grosjean, and Baker (1999) showed that phenolic compounds exhibit inhibitory activity on AFB1 biosynthesis by A. flavus. It is clear that phenolic compounds have inhibited one or more early, rather than late, steps in the aflatoxins PLX4032 price biosynthesis pathway. According to Farag, Daw, Hewedi,
Edoxaban and El-Baroty (1989) the presence of phenolic groups to form hydrogen bonds with the active sites of target enzymes was capable of increasing antimycotoxigenic activity. Jayashree and Subramanyam (1999) reported that phenolic compounds inhibited aflatoxin production without any significant effect on growth of the organism. Turmeric (C. longa) has many biological activities, such as the antioxidant properties demonstrated by Zaeoung, Anuchit, and Niwat (2005) and Singh et al. (2010). Zjalic et al. (2006) and Kim et al. (2008) showed that aflatoxins biosynthesis is related to oxidative stress and peroxidation of fungal cells. These studies showed an ability of phenolic compounds to inhibit lipid peroxidation without changes in growth or primary metabolism. Thus, the antioxidant property of C. longa could be important to the inhibition of aflatoxin production. Because essential oils are easily acquired and employed, are cheap to produce, lack the problems that are inherent in synthetic chemical products, have low mammalian toxicity and are biodegradable and non-persistent in the environment, developing them for use in crop protection may be an attractive option. However, further studies need to be conducted to evaluate the cost and efficacy of these essential oils for fungal control programs.