Impact of environmental factors on the antifungal efficacy of vapours released by Pëumus boldus Mol. and Lippia turbinata var. Intergrifolia (Griseb.) essential oils

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

Congreso; WMF meets IUPAC 2012; 2012

In Argentina, the large volume of peanuts entering the storage systems at the harvest time, exceed the storage capacity, which cannot be adequately dry or exposed to sunlight. Under these circumstances, the grains increase moisture and temperature due to biological activity, resulting in loss of quality and nutritional value, grain mold and accumulation of toxic metabolites such as aflatoxins. Keeping these facts in view, there are need effective control measures against fungal and mycotoxin contamination in order to enhance the shelf life of food items during postharvest processing. In view of the high efficacy as antifungal and aflatoxin inhibitors in vitro, boldo and poleo essential oils (EOs) may be used as ecofriendly alternatives to synthetic preservatives. Thus, this study was carried out in order to evaluate if boldo and poleo EOs have the ability to maintain their antifungal activity after subjecting them to environmental variations. Experiments were performed to determine the thermostable nature of the oils, and the stability during sunlight and UV exposure and storage time. Different glass vials containing 3 mL oil each were subjected: to different temperature treatments for 1 h in incubators already adjusted at 40, 60 and 80 °C; to sunlight during 30 and 60 min; to UV light (260 nm) during 15 and 30 min; and to storage during 6 months at 4 °C. The fungitoxicity of the treated oils from each set was tested against A. flavus and A. parasiticus strains at 2000 µL/L on peanut based medium. When boldo EO was exposed to UV light during 30 min, the inhibitory activity on A. flavus strains was reduced by 29.1% compared to the EO without treatment, and was not modify on A. parasiticus strains. Meanwhile, sunlight exposition reduced inhibitory capacity of this oil by 29.6 and 30.9% at 30 and 60 min, respectively. The thermostability of the oil was tested and it was found that at temperature ranging from 40 to 80 °C, its activity was not altered. Boldo EO showed a stable behavior during the first five storage months; however at six month its inhibitory activity was reduced by 48.4 and 66.5% on A. flavus and A. parasiticus strains, respectively. The volatile components activity of poleo EO was not altered when the oil was exposed to heat, sunlight and UV. However, a total loss of inhibitory activity was observed at sixth month of storage. In conclusion, our study demonstrated that the inhibitory ability of boldo and poleo oil volatile fractions remained stable against temperature changes, while the antifungal capacity of these oils was subjected to variations due to many factors related to the type system and storage time.