Comparative Evaluation of the Chemical Composition, Antioxidant and Antimicrobial Activities of the Volatile Oils of Hawk Tea from Six Botanical Origins.[Pubmed: 27472082]

In this study, volatile oils of six Hawk tea varieties were studied for their chemical composition, antioxidant and antimicrobial activities to screen the most suitable botanical origins of Hawk tea. A total of 72 components were separated and identified from the six oils. The major constituents of the volatile oils were: α-pinene, camphene, limonene, 1,8-cineole, linalool, cis-nerolidol, and germacrene B. Moreover, the volatile oils were evaluated for antioxidant potential and antimicrobial activities. The results showed that all volatile oils exhibited acceptable antioxidant and antimicrobial activities, which suggested that these volatile oils may serve as natural alternatives to synthetic antioxidants and preservatives to be applied in food and pharmaceutical industries. Principal component analysis results denoted that some major compounds may be closely related to the antioxidant and antimicrobial activities. It also showed that the volatile oils from Litsea coreana var. lanuginosa and Litsea pungens Hemsl. were characterized by positive values of first two principal components, indicating higher active chemical compounds and antioxidant and antimicrobial activities compared with other species. Thus, they were temporarily considered as good sources of Hawk tea.

Comparative toxicity of essential oils of Litsea pungens and Litsea cubeba and blends of their major constituents against the cabbage looper, Trichoplusia ni.[Pubmed: 19422220]

Contact toxicity of essential oils of Litsea pungens Hemsl. and L. cubeba (Lour.) Pers. (Lauraceae) and of blends of their major constituents was assessed against third-instar Trichoplusia ni larvae via topical application. Both oils showed moderate activity against T. ni larvae with LD(50) values of 87.1 and 112.5 microg/larva, respectively. 1,8-Cineole from the essential oil of L. pungens and gamma-terpinene from the oil of L. cubeba accounted for much of the toxicity of the oils to T. ni larvae. The toxicity of blends of selected constituents indicated a synergistic effect among putatively active and inactive constituents, with the presence of all constituents necessary for full toxicity of the natural oils. The results show that essential oils of L. pungens and L. cubeba and some of their constituents have potential for development as botanical insecticides.

[Population dynamics of endangered plant species Abies chensiensis].[Pubmed: 16422493]

In order to know the endangered status and causes of Abies chensiensis in Qinlin Mountains, a field investigation on 18 plots was conducted on its age structure, life table and fecundity, and its population dynamics were predicted by time sequence model. The analysis on the age structure of Abies chensiensis populations showed that there were fewer young individuals, but middle-aged and old individuals were relatively rich. The population D in Abies chensiensis-Indigofera amblyantha-Carex lanceolata association showed a relatively stable development tendency, while other four populations (A, B, C and E) in Abies chensiensis-Pinus tabulaeformis-Sinarundinaria nitida-Carex lanceolata association, Abies chensiensis-Quercus aliena var. acutserrata-Litsea pungens-Carex lanceolata association, Abies chensiensis-Betula albo-sinensis-Sinarundinaria nitida-Duchesnea indica association, and Abies chensiensis-Pinus tabulaeformis-Smilax stans-Carex lanceolata association all showed an obviously declining tendency. The analysis on the life tables and survival curves showed that the survival curve of Abies chensiensis populations belonged to Deevey III, and the death peak of different populations was in the period of 60--100 years old. The number difference among populations reflected the population habitat. Time sequence prediction indicated the numbers of old individuals would be increased at the beginning, and decreased finally in 20, 40, and 80 years. It was difficult to maintain the population stability. Analysis on 10 ecological factors showed that tree coverage, soil organisms and air humidity influenced population positively, and human disturbance and sunlight influenced population negatively. In situ conservation should be taken as the most important management countermeasure, and natural regeneration should be promoted. At the same time, artificial population should be expanded.