Antifungal and anti-aflatoxigenic activity by vapour contact of Pëumus boldus (Mol.) and Lippia turbinata var. intergrifolia (Griseb.) essential oil mixtures

PASSONE, M. A., GIRARDI, N. S., ETCHEVERRY, M

rotterdam

Congreso; WMF meets IUPAC 2012; 2012

Aspergillus flavus and A. parasiticus are the best adapted fungal species to peanut storage with ability to produce the major significant mycotoxins, the aflatoxins. Aflatoxins in general and specially aflatoxin B1 (AFB1) is a mutagenic, teratogenic and hepatocarcinogenic secondary metabolite. The vegetative growth and subsequent aflatoxin by A. flavus and A. parasiticus were found to be sensitive to 1000 µL/L of EOs extracted from Pëumus boldus (Mol.) (boldo) and Lippia turbinata var. integrifolia (Griseb.) (poleo) leaves in contact and volatile assays. Therefore, the aim of this work was evaluate the antifungal and antiaflatoxigenic properties of boldo and poleo mixtures present in the headspace of peanut extract medium at three water activity levels (0.98, 0.95, 0.93 aW). The study was conducted in order to determine the existence of additive and/or synergistic effects that can increase the effectiveness of oils, to achieve inhibitory effects at lower concentrations. The treatments were the following: B-P mixtures (250 + 500 µL/L), (250 + 1000 µL/L), (250 + 1500 µL/L), (500 + 500 µL/L), (500 + 1000 µL/L), (500 + 1500 µL/L), (750 + 500 µL/L), (750 + 1000 µL/L), (750 + 1500 µL/L). At all aW assayed the mixtures with B750-P1000 and B750-P1500 were able to produce a significant increase in lag phase. The increase of poleo concentrations from 500 to 1500 µL/L only showed a significant effect (p = 0.05) on Aspergillus growth when this oil was combined with 750 µL/L of boldo, resulting in growth inhibition increases in the order of 24.2 and 40.3% at 0.98 and 0.95 aW, respectively. Meanwhile, at 0.93 aW and in presence of B500-P1500 and mixtures that contained the highest dose of boldo (750 µL/L) the strains were not able to growth. In 11-day-old Aspergillus cultures and treated with 750 µL/L of boldo, AFB1 accumulation was reduced by 84.9 and 99.8% at 0.98 and 0.95 aW, respectively. While the highest AFB1 inhibition levels were observed at 0.93 aW; the mixtures with 500 and 750 µL/L of boldo EO produced 100% inhibition. Although the vapor released by the treatments that contained 500 µL/L of poleo EO significantly reduced (p < 0.001) AFB1 accumulation; the increasing concentrations of this EO (1000-1500 µL/L) did not show major inhibitory effects. In conclusion, boldo appears to be the EO most effective, this suggests that the volatile fraction of this oil at doses >750 µL/L is an effective potential compound for inhibition of Aspergillus section Flavi growth and AFB1 production over a range of environmental conditions in peanut based medium.