Chemical Composition and Insecticidal Activities of the Essential Oil from Fruits of Euonymus schensianus

Abstract

The genus Euonymus (Celastraceae), distributed in the subtropical and temperate regions, with only a few species extending northward to the frigid temperate zone, consists of 220 species of vines, shrubs, and small trees. The genus Euonymus has been widely used to treat bruises and rheumatic arthralgia; it is also used to promote blood circulation, as an insecticidal, and for detoxification in traditional Chinese medicines [1]. Research shows that the compounds in the genus Euonymus have pharmaceutical activity, such as cytotoxicity, immunosuppression, antitumor, antidiabetes, anti-inflammatory, antibacterial, antiviral, and insecticidal [2–4]. To the best of our knowledge, the composition of the essential oil from Euonymus schensianus Maxim. fruits and its insecticidal activity are reported for the first time. The composition of the essential oil was determined by GC-MS. The yield of essential oil was 0.26% (v/w). A total of 74 components was identified, accounting for 100.0% of the total (Table 1). The main compounds were n-hexadecanoic acid (23.24%), linoleic acid (14.99%), petroselinic acid (8.72%), and benzyl nitrile (5.38%) followed by tromacaps (4.85%) and cis-vaccenic acid (3.83%). The essential oil of E. schensianus fruits showed strong fumigant toxicity against Tribolium castaneum and Sitophilus zeamais with LC50 values of 1.282 and 1.760 mg/L, respectively (Table 2). Compared with the positive control, methyl bromide (MeBr), the essential oil was three times less toxic to S. zeamais. However, the essential oil showed roughly the same fumigant toxicity to T. castaneum. The essential oil of E. schensianus fruits also possessed strong contact toxicity against T. castaneum (LD50 = 1.913) and S. zeamais (LD50 = 1.529). Compared with the famous botanical insecticide pyrethrum extract, the essential oil was six times less active against T. castaneum. Howerver, it exhibited three times greater activity to S. zeamais (Table 3). Plant Material and Isolation of Essential Oil. The fresh fruits of E. schensianus Maxim (20 kg) were collected from Qinling Mountains, Shaanxi Province, China and identified by Prof. Jian-Chun Qin, College of Plant Sciences, Jilin University. Voucher specimens (No. SXWM 20150828) were deposited in the laboratory herbarium. Dried fruits were submitted to hydrodistillation for 4 h using a Clevenger-type apparatus. The obtained essential oil was filtered and dried over anhydrous sodium sulfate, stored at 4°C. GC-MS Analysis. GC-MS (70 eV) data analysis of the essential oil was carried out on a Thermo TRACE Gc Agilent 5975 chromatograph, equipped with an HP-5 ms capillary column (30 m × 0.25 mm, 0.25 μm film thickness). The temperature was programmed from 60°C to 280°C at 8°/min, held isothermal at 60°C for 3 min and at 280°C for 20 min. The temperature of the injector was kept at 280°C; sample injection volume, 1 μL; split ratio was 30:1. The carrier gas was helium at a flow rate of 1 mL/min. MS source temperature at 230°C; MS quadrapole temperature at 150°C; interface temperature at 280°C; mass scan, 20–450 amu (atomic mass units).