| Many Cinnamomum plants not only have beautiful appearance with leaves green and luxuriant, exuberant foliage, but also have multiple ecological functions such as noise-suppression, dust-proofing and air purification. Therefore, Cinnamomum plants have been widely planted as gardening trees in south China. There are abundant Cinnamomum plants in Chongqing, China. For full exploitation of the local resources,in this study, we selected four Cinnamomum plants which are common plants in Chongqing area as the research objects. Essential oils from the four Cinnamomum plants, Cinnamomum camphora(L.) Presl., Cinnamomum japonicum Sieb.,Cinnamomum szechuanense Yang and Cinnamomum subavenium Miq., were extracted by hydrodistillation, their chemical compositions were analyzed by Gas Chromatography-Mass Spectrometry(GC-MS). The total antioxidant capacity, DPPH free radicals and hydroxyl free radicals scavenging of the four essential oils were evaluated, and also the larvicidal activities of these essential oils were evaluated by immersion method against the larvae of Anopheles sinensis. The results are as follows:1. Essential oils from the four Cinnamomum plants were extracted by hydrodistillation. Extraction yields of the four essential oils were respectively 0.625%(C.camphora), 0.516%(C. japonicum), 0.600%(C. szechuanense) and 0.579%(C.subavenium). The difference of the extraction results was not significant.2. The chemical compositions of the four essential oils were analyzed by GC-MS.Results showed that 45 chemical compounds were detected from C. camphora essential oil, of which 42 chemical constituents were identified. The main constituents of C.camphora essential oil were 1,8-cineole(40.9147%), linalool(20.6623%), α-terpineol(9.5843%) and β-phellandrene(9.5259%). 42 chemical constituents were identified from C. japonicum essential oil, it’s major components were borneol(25.1613%),1,8-cineole(24.6174%), O-cymene(12.4607%), α-terpineol(9.5843%) andα-phellandrene(6.4985%). 55 chemical compounds were detected from C.szechuanense essential oil, of those 53 chemical constituents were identified, the majoringredients were 1,8-cineole(42.8964%), α-pinene(12.3536%), camphene(7.8123%),O-cymene(7.5873%) and bomyl acetate(6.5332%). 49 chemical compounds were detected from C. subavenium essential oil, and 47 chemical constituents were identified,the most abundant compounds in C. subavenium essential oil was eugenol(67.7290%),and followed with engenol acetate(13.1856%), α-pinene(4.1845%) and ocimene(3.0017%). 9 components were commonly detected from the four essential oils, which were α-pinene, β-pinene, camphene, myrcene, o-cymene, 1,8-cineole, δ-Terpinene,caryophyllene, and bornyl acetate. Among them, 1,8-cineole has the highest content, it’s content in the four essential oils were 40.9147%(C. camphora), 24.6174%(C.japonicum), 42.8964%(C. szechuanense) and 1.9208%(C. subavenium), respectively.Cluster analysis also showed that the chemical compositions of C. subavenium essential oil was quite different from those of C. camphora, C. szechuanense and C. Japonicum.3. The total antioxidant capacity, DPPH free radicals and hydroxyl free radicals scavenging of the four essential oils were evaluated. The results showed that both of the four essential oils had certain antioxidant activities, and the total antioxidant capacities was gradually strengthening with the increasing of the essential oils’ concentrations.Among them, C. subavenium essential oil’ total antioxidant capacity was the strongest.At concentrations of 0.1-0.3 mg/m L, its total antioxidant activity was significantly higher than that of synthetic antioxidant BHA(P < 0.05). The order of the total antioxidant capacity was C. Subavenium > C. Szechuanense > C. japonicum > C.camphora. A concentration-dependent DPPH free radicals scavenging activity was found in the four essential oils. The EC50 values of the C. subavenium essential oil was less than 1.0 mg/m L. The other three essential oils’ EC50 values were 23.86 mg/m L(C.camphora), 34.11 mg/m L(C. japonicum) and 11.99 mg/m L(C. szechuanense),respectively. At low concentrations(1.0-2.0 mg/m L), C. subavenium essential oil’s DPPH radical scavenging activity was comparable to that of synthetic antioxidant BHA.The order of the DPPH radical scavenging activity was C. subavenium > C.szechuanense > C. japonicum > C. camphora. Under the experimental concentrations,all of the four essential oils exhibited higher OH radical scavenging activities, and the activities showed a slight enhencing with concentrations. At low concentrations(1.0×10-5-2.0×10-5 mg/m L), only C. subavenium essential oil’ OH radical scavenging activity was lower than BHA significantly. The order of the OH radical scavenging activity was C. szechuanense > C. japonicum > C. camphora > C. subavenium.Generally speaking, among the four essential oil, C. subavenium essential oil has thebest total antioxidant capacity and free radical scavenging abilities, indicating that it has the potential to be developed as the natural antioxidants.4.The larvicidal activity of the four essential oils and four major components against the larvae of An. sinensis was tested by immersion method. All of the four essential oils produced certain larvicidal activities against An. sinensis larvae in a dose-dependent manner. Among the four essential oils, C. subavenium essential oils have the strongest larvicidal activities with the LC50 value of 79.63 μg/m L. The other three essential oils’ LC50 values against An. sinensis larvae were 109.401 μg/m L(C.camphora), 117.802 μg/m L(C. japonicum), and 96.808 μg/m L(C. szechuanense),respectively. The order of larvicidal activity of the four essential oils was C.subavenium > C. szechuanense > C. camphora > C. japonicum. The four major compounds also have larvicidal activities against the larvae of An. sinensis. The LC50 of eugenol, linalol, borneol and 1,8-cineole was 154.40 μg/m L, 227.87 μg/m L, 251.73μg/m L and 450.00 μg/m L, respectively. Among them, eugenol has the best larvicidal activities against An. sinensis larvae.The study shows that essential oil of C. subavenium not only have preferable antioxidant capacity and free radical scavenging abilities, but also has better lavicidal activities against the larvae of An. sinensis. Therefore, C. subavenium essential oil has the potential of being developed as natural antioxidants and botanical insecticides. |
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