滇产薄荷的化学研究

研究了滇产３８个薄荷样品,测定了样品的得油率及化学成分。滇产薄荷的得油率在０．１８％￣０．５２％之间。从挥发油中鉴定出了１００多种化学成分,主要含醇、酮、酯、萜烯类化合物。栽培的家薄荷挥发油富含香芹酮、柠檬烯,其化学分类属于香芹酮系列。野生薄荷挥发油富含薄荷醇和薄荷酮,属于薄荷酮系列;部分野薄荷样品,富含香芹酮、环氧辣薄荷烯酮或芳樟醇,属于混合系列。     

Structural investigation of amylose complexes with small ligands: inter- or intra-helical associations?

Highly crystalline amylose complexes with menthone (1) and linalool (2) were analysed by wide-angle X-ray diffraction and solid-state nuclear magnetic resonance (NMR). The complexes, after partial water desorption in a controlled atmosphere (a_w = 0.75), displayed a typical V–isopropanol structure, showing the presence of ligand inside or between the helices in the crystalline domains. Sequential washing of the powdered complexes with ethanol before and after desorption permitted probing the intra- and inter-helical inclusions. High resolution magic angle spinning (HRMAS) recordings were used to compare the chemical shifts of free and bound aroma which allowed a proposal that some hydrogen bonding is involved in the amylose complexing. Moreover, it showed that free aroma was completely removed by ethanol washing. Using cross polarization magic angle spinning (CPMAS) and X-ray scattering experiments, it was demonstrated that the V–isopropanol type was retained for linalool whatever the treatment used. On the contrary, the measurement shifts toward the V–6I amylose hydrate (V–h) type for menthone after ethanol washing before the desorption step, reflecting the disappearance of inter-helical associations between menthone and amylose. The stability of the complex prepared with linalool shows that this ligand is more strongly associated to amylose helices. The discrepancies observed in the chemical shifts attributed to carbons C1 and C4 in CPMAS spectra of V–isopropanol and V–h forms could be attributed either to a deformation of the single helix (with possible inclusion of the ligand inside) or to the presence of the ligand between helices (only water molecules are present in the V–h form).     

Intraspecific variation in essential oil composition of Eremophila longifolia F. Muell. (Myoporaceae): Evidence for three chemotypes

Volatile oils of Eremophila longifolia F. Muell. (Myoporaceae) leaves were obtained by hydrodistillation and analysed using GC-MS. A total of 33 compounds were identified in the oils examined and a high degree of intraspecific variability in chemical composition between specimens occurring in separate geographic localities was found. Multivariate statistical analysis of chemical composition of volatile oils enabled classification of three chemotypes in this species.     

Changes in composition of essential oils and volatile emissions of Minthostachys mollis, induced by leaf punctures of Liriomyza huidobrensis

Plant defensive mechanisms against herbivores include chemical changes following damage. Effects of feeding punctures produced by Liriomyza huidobrensis (pea leafminers) adult females on the plant's dominant monoterpenes, pulegone and menthone were assessed by monitoring essential oil composition at 24, 48, and 120 h; emission of volatiles was also measured 24 and 48 h after wounding. We studied such changes in Minthostachys mollis, a Lamiaceae species native to Central Argentina with medicinal and aromatic uses. Leaf puncturing resulted in reduced menthone throughout the experiment and increased pulegone concentration in M. mollis essential oil during the first 48 h. The adjacent undamaged leaves showed similar changes, suggesting a systemic response. Composition of volatiles released from damaged leaves was also altered, most noticeably by increasing pulegone and diminishing menthone emissions. Such herbivore-induced chemical changes in aromatic plants are economically relevant, since the quality of essential oils and volatile emissions are altered.     

Variation of the chemical composition of essential oils in Brazilian populations of Cunila menthoides Benth. (Lamiaceae)

Cunila menthoides Benth. is characterized as a xilopodiferous subshrub with strong and pleasant smell. This species is commonly used in South Brazilian folk medicine. Air-dried samples of four Brazilian populations of C. menthoides were extracted by steam distillation and analyzed using GS and GS–MS. A total of 15 volatile compounds were detected and identified. Two groups, which can be considered as chemotypes, were formed by the average linkage cluster analysis. The first group was characterized by high concentrations of pulegone, with some individuals showing variations to menthone; and the second group was characterized by high concentrations of linalool.