Biological Activity of Humulus Lupulus (L.) Essential Oil and Its Main Components Against Sitophilus granarius (L.).

Gianluca Paventi,Marco Pistillo,Antonio De Cristofaro,Giacinto S Germinara,Laura De Acutis,Giuseppe Rotundo

doi:10.3390/biom10081108

Gianluca Paventi, Marco Pistillo + Show 4 more

Open Access

https://doi.org/10.3390/biom10081108

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Journal: Biomolecules	Publication Date: Jul 25, 2020
Citations: 18	License type: CC BY 4.0

Affiliation: University of Molise, University of Foggia

Abstract

Besides its use in the brewing industry, hop cones appear as a powerful source of biologically active compounds, already checked for their putative anticancer, antimicrobial, and other bioactivities. Conversely, hop use in pest control remains to date under-investigated. Therefore, the biological activity of hop essential oil (EO) and its main constituents was investigated here against Sitophilus granarius. Adult contact toxicity was found 24 h after treatment with hop EO (LD50/LD90 13.30/40.23 µg/adult), and its three most abundant components, α-humulene, β-myrcene, and β-caryophyllene (LD50/LD90 41.87/73.51, 75.91/126.05, and 138.51/241.27 µg/adult, respectively); negligible variations at 48 h, except for α-humulene (LD50/LD90 26.83/49.49 µg/adult), were found. The fumigant toxicity of the EO and terpenes was also checked: in the absence of wheat grains, β-myrcene showed the highest inhalation toxicity (LC50/LC90 72.78/116.92 mg/L air), whereas α-humulene, β-caryophyllene, and the EO induced similar values (LC50/LC90 about 130/200 mg/L air); with the exception for EO, the wheat presence increased (30–50%) LC50/LC90 values. Moreover, EO and terpenes were perceived by insect antennae and elicited repellent activity. Only β-caryophyllene showed an anticholinesterase effect, this suggesting that different mechanisms of action should be responsible for hop EO toxicity. Therefore, hop EO appears suitable for developing control means against this pest.

Highlights

Hop, Humulus lupulus (L.), is a flowering and perennial plant belonging to Cannabacea family, whose female flowers, clustered in inflorescences, are used in the brewing process of beer
Aromatic plants appear to be a remarkable source of biologically active compounds, among which some are already used as natural insecticides [21,22]
In order to characterize the wild hop ecotype used in this study, the essential oil (EO) composition was investigated by means of Gas Chromatography-Mass Spectrometry (GC-MS) analysis

Summary

Introduction

Humulus lupulus (L.), is a flowering and perennial plant belonging to Cannabacea family, whose female flowers, clustered in inflorescences, are used in the brewing process of beer. Highlighted activities of hop against detrimental fungi [12], mites [13], and insects [14,15] This aspect appears extremely urgent since, as known, the traditional control of stored-product insect pests has relied primarily on synthetic insecticides like organochlorines, organophosphates, methyl bromide, and phosphine [16]. The preimaginal stages of some pests, such as Sitophilus granarius (L.) (Coleoptera, Curculionidae), develop within grains, limiting the efficacy of these pesticides and leading to a more intense application [20] For these reasons, the development of alternative strategies to synthetic chemicals is very important in pest control, especially in this latter case. Aromatic plants appear to be a remarkable source of biologically active compounds, among which some are already used as natural insecticides [21,22]

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