QSAR Study of Biologically Active Essential Oils against Beetles Infesting the Walnut in Catamarca, Argentina

Abstract

Essential oils from six species of aromatic plants collected in the Catamarca Province of Argentina were evaluated for their chemical composition and repellent and insecticidal activities against beetles of the genus Carpophilus (Coleoptera: Nitidulidae) and Oryzaephilus (Coleoptera: Silvanidae) that infest the local walnut production. Experimental data were analyzed using generalized estimating equations, with normal distribution and the identity link function. From the spectral information from the tested essential oils, we worked their molecular modeling as mixtures by developing mixture descriptors (D mix) that combined the molecular descriptor of each component in the mixture (d i ) and its relative concentration (x i ), i.e., D mix = f(d i , x i ). The application of chemoinformatic approaches determined that a combination of mixture descriptors related to molecular size, branchedness, charge distribution, and electronegativity were useful to explain the bioactivity profile against Carpophilus spp. and Oryzaephilus spp. The reported models were rigorously validated using stringent statistical parameters and essential oils reported with repellent activity against other beetle species from the Nitidulidae and Silvanidae families. This model confirmed each essential oil as a repellent with a comparable performance to the experimental reports.

Excito-repellent and Pesticide-Likeness Properties of Essential Oils on Carpophilus dimidiatus (Fabricius) (Nitidulidae) and Oryzaephilus mercator (L.) (Silvanidae)

“…Five repetition were performed for each treatment and replicated in triplicate. The number of beetles present on the treated ( N t ) and control ( N c ) areas after 2 and 4 h (repeated measurements in time) was used to compute excito-repellency percentage (ER) according to E R = true[ N C − N T N C + N T true] × 100 The mean ER value of each essential oil was calculated and assigned to ER classes from 0 to V: class 0 (ER < 0.1%), class I (ER = 0.1–20%), class II (ER = 20.1–40%), class III (ER = 40.1–60%), class IV 195 (ER = 60.1–80%), and class V (ER = 80.1–100%) …”

“…In order to characterize the chemical space of the tested essential oils, physicochemical properties of EOs as mixtures were determined according to. , Based on the descriptors of individual components of the mixture ( d i ), the corresponding 21 mixture descriptors dependent on the mixture qualitative composition were derived in two ways:…”

“…C. dimidiatus and O. mercator were obtained from a colony maintained in the LACBBI-CREAS-CONI-CET/UNCA. Both species were raised in glass flasks with an artificial diet by protocol, 6 in breeding chambers at controlled temperature, humidity, and photoperiod (25 °C, 70% HR and 12:12 h light/dark). The beetles used in all experiments were approximately 2 weeks old, after hatching as adults, and all in vitro bioassays were carried out in a climatic chamber maintained at 25 °C and 60−70% RH.…”

“…In order to characterize the chemical space of the tested essential oils, physicochemical properties of EOs as mixtures were determined according to. 6,19…”

“…The excito-repellent activity of the essential oils against C. dimidiatus and O. mercator was assessed following the method described in. 6 Essential oils were tested as acetone solutions at doses of 0.05, 0.10, 0.20, 0.40, and 0.60 μL/cm 2 . Ten unsexed adults were introduced in each experimental unit.…”