Chemical Constituents of the Essential Oil Extracted from Elsholtzia densa and Their Insecticidal Activity against Tribolium castaneum and Lasioderma serricorne

Abstract

Storage pests pose a great threat to global food security. Here, we found that the essential oil (EO) extracted from E. densa possesses obvious effects against the insects that threaten stored-products. In this work, we investigated the chemical constituents of the essential oil extracted from Elsholtzia densa, and their insecticidal (contact and fumigant) toxicity against Tribolium castaneum and Lasioderma serricorne. A total of 45 compounds were identified by GC-MS, accounting for 98.74% of the total EO. Meanwhile, 11 compounds were isolated from the EO, including limonene, β-caryophyllene, ρ-cymene, trans-phytol, α-terpineol, linalool, acetophenone, 1,8-cineole, ρ-cymen-7-ol, 1-O-cerotoylgly-cerol, and palmitic acid. Furthermore, acetophenone, ρ-cymen-7-ol, and 1-O-cerotoylgly-cerol were isolated for the first time from Elsholtzia spp. The results of the bioassays indicated that the EO had the property of insecticidal toxicity against T. castaneum and L. serricorne. All of the compounds showed different levels of insecticidal toxicity against the two species of insects. Among them, 2-ethyl-1H-imidazole had no insecticidal toxicity against T. castaneum, but possessed fumigant and obvious contact toxicity against L. serricorne. ρ-Cymen-7-ol had beneficial insecticidal toxicity against the two species of insects, and fumigant toxicity against L. serricorne. ρ-Cymen-7-ol (LD50 = 13.30 μg/adult), 1-octen-3-ol (LD50 = 13.52 μg/adult), and 3-octanol (LD50 = 17.45 μg/adult) showed significant contact toxicity against T. castaneum. Acetophenone (LD50 = 7.07 μg/adult) and ρ-cymen-7-ol (LD50 = 8.42 μg/adult) showed strong contact toxicity against L. serricorne. ρ-Cymene (LC50 = 10.91 mg/L air) and ρ-cymen-7-ol (LC50 = 10.47 mg/L air) showed powerful fumigant toxicity to T. castaneum. Limonene (LC50 = 5.56 mg/L air), acetophenone (LC50 = 5.47 mg/L air), and 3-octanol (LC50 = 5.05 mg/L air) showed obvious fumigant toxicity against L. serricorne. In addition, the EO and its chemical compounds possessed different levels of repellent activity. This work provides some evidence of the value of exploring these materials for insecticidal activity, for human health purposes. We suggest that the EO extracted from E. densa may have the potential to be developed as an insecticidal agent against stored product insect pests.

Behavioral Response, Fumigation Activity, and Contact Activity of Plant Essential Oils Against Tobacco Beetle (Lasioderma serricorne (F.)) Adults

“…Meanwhile, Table 3 shows that the LD 50 of the contact activity against L. serricorne adults of plant essential oils in rosemary, geranium, citronella, basil, and eucalyptus are 3.60, 3.49, 8.90, 6.70, and 7.80 μl/L, respectively, which are even better than those of Pirimiphos-methyl (15.45 μl/L) and Chlorantraniliprole (249.77 μl/L). In recent years, many research studies on the essential oils against L. serricorne have been performed, for example, Liang et al (2021) found that Elsholtzia densa essential oil possesses obvious contact activity (LD 50 = 24.29 mg/L) against L. serricorne . Meanwhile, Zhou et al (2018) reported that the Artemisia lavandulaefolia (Compositae) essential oil also exhibited good contact toxicity (LD 50 = 13.51 μg/L) to control L. serricorne .…”

Chemical Composition of Essential Oils from Three Rhododendron Species and Their Repellent, Insecticidal and Fumigant Activities

“…In addition, other Rhododendron plants had also been reported to have contact activity against these three insects. Such as the EO extracted from the R. thymifolium and its principal Germacrone had good contact activity against L. serricorn adults, larvae and T. castaneum larvae with LD 50 values of 29.15 μg/adult, 42.73 μg/larva, 19.65 μg/larva, respectively [22] …”

“…For example, EO of R. anthopogonoides have been reported to possess insecticide and fumigant activities against S. oryzae , and its main component 4‐Phenyl‐2‐butanone shows pronounced contact toxicity against S. oryzae [21] . The EO of R. thymifolium possessed the obvious repellent and contact activities against the T. castaneum and L. bostrychophila , and the presence of permafrost might be one of the key factors affecting the contact toxicity of R. thymifolium EO against T. castaneum and L. bostrychophila [22] . There four EOs from Rhododendron species, including R. capitatum , R. przewalskii , R. mucronulatum , and R. micranthum has been reported to have repellent activities against T. castaneum , L. serricorne and L. bostrychophila adults, and within a certain concentration range, the repellent activities show a certain stability [23] .…”

Investigation of insecticidal activity of two Rhododendron species on stored-product insects

“…Most of the chemical constituents detected in R. przewalskii EO reported in this paper were consistent with the previous studies (Bai et al 2019 ). Compared with the other Rhododendron plants, these two EOs were also found rich in terpenoids, while the types and contents of terpenoids were different; for example, the content of β-Elemenone was 0.84% in the specie of R. Rufum in this experiment, whereas β-Elemenone (35.17%) had a high content in the specie of R. thymifoliu (Liang et al 2021a , b ). Spathulenol (14.4%), one of the main components isolated in the EO of R. albiflorum leaves, is only 0.71% in the species of R. przewalskii (Schepetkin et al 2021 ).…”

“…In view of the above situations, a series of measures have been taken to prevent pest risks. The most commonly used method is the application of synthetic chemicals (Liang et al 2021a , b ). For example, phosphine fumigants and pyrethroids contact insecticides have been widely used for controlling insects in stored products worldwide (Nayak et al 2020 ; Campolo et al 2018 ).…”