Nitrogen nutrition and flavour compounds of carrots (Daucus carota L) cultivated in Mitscherlich pots

Carrots (Daucus carota L) of the cultivar ‘Nanthya’ F₁ were grown in Mitscherlich pots containing quartz sand with inorganic nitrogen fertilisation (five levels, four replications) and time‐controlled drip irrigation. The effect of different nitrogen uptake on the yield and on the amount and composition of essential oils, sugars and organic acids was investigated. Sucrose, glucose and fructose were extracted and analysed by HPLC; L ‐malic acid and citric acid were measured with an enzymatic test. Medium‐ and higher‐boiling flavour components were isolated as essential oils by simultaneous watersteam distillation and pentane extraction (SDE) and separated gas chromatographically (HRGC–FID). Thirteen essential oil components were identified by mass spectrometry as well as by comparison of retention times and quantified by external standards. The higher the supply of nitrogen, the higher was its uptake and as a consequence the higher were the nitrogen and nitrate contents of the leaves as well as the roots of the carrots. Carrots with lower nitrogen application had higher amounts of sucrose and essential oils but lower amounts of glucose and fructose. Fertilisation with nitrogen affected not only the total content but also the composition of the essential oils. A correlation between nitrogen nutrition and organic acids could not be found. © 2000 Society of Chemical Industry     

Sensory quality of ethylene‐exposed carrots (Daucus carota L,cv ‘Yukon’) related to the contents of 6‐methoxymellein,terpenes and sugars

Carrots were analysed for taste and odour and for contents of terpenes, 6‐methoxymellein and sugars during 3 weeks storage at 15 °C in an atmosphere containing ethylene (1 µl l⁻¹). The ethylene treatment caused an increase in 6‐methoxymellein and the conversion of higher amounts of sucrose to fructose and glucose compared to control carrots stored in air. This corresponded to higher sensory scores for bitterness and terpene flavour and a lower score for sweetness, as measured by an expert taste panel. Principal component analysis showed a more expressed bitter taste, earthy flavour, green flavour, terpene flavour and aftertaste in the ethylene‐treated carrots. Correlations were found between sweet taste and the content of sucrose (r = 0.91, p < 0.005) and between the contents of various terpenes (particularly γ‐terpinene, limonene and caryophyllene) and terpene flavour, green flavour, aftertaste and bitter taste (r ≥ 0.72, p < 0.05). In the air‐stored carrots these off‐flavours seemed to be masked by a high sucrose content. © 2000 Society of Chemical Industry     

Biosynthesis of sesquiterpenes by the fungus Fusarium verticillioides

The volatiles of the fungus Fusarium verticillioides were analysed by GC-MS. Sesquiterpenes dominated, with trichodiene as the principle component. Several other sesquiterpenes were detected in low amounts that were unambiguously identified from their mass spectra and retention indices. The absolute configurations of (R)-β-bisabolene, (R)-cuparene, (+)-β-barbatene, (-)-α-cedrene, (+)-β-cedrene, and (+)-α-funebrene originating from different key cationic intermediates, were determined by chiral GC-MS and proved to be related to the trichodiene stereostructure. The unusual compound (E)-iso-γ-bisabolene was also found corroborating a previously suggested mechanism for the cyclisation of the bisabolyl to the cuprenyl cation that is based on quantum mechanical calculations (Y. J. Hong, D. J. Tantillo, Org. Lett. 2006, 8, 4601-4604). These analyses resulted in a revised biosynthesis scheme to trichodiene and the side products of the responsible terpene cyclase, trichodiene synthase, an enzyme that is well characterised from Fusarium sporotrichioides. Feeding studies with several deuterated mevalonolactone isotopomers unravelled stereochemical aspects of the late cyclisations towards trichodiene.     

银根-额济纳旗盆地烃源岩特征及油气富集规律

基于对银根-额济纳旗盆地上古生界、侏罗系和白垩系烃源岩地球化学特征的系统评价,分析了盆地内各凹陷的油气来源和富集规律。盆地上古生界石炭系—二叠系暗色泥岩整体已达到过成熟阶段,中生界凹陷内已发生浅变质—变质作用,油气保存条件较差,油气资源和勘探潜力小;中—下侏罗统发育一套煤系烃源岩,在盆地腹部及南部凹陷中已达成熟阶段,具有一定生烃潜力;白垩系巴音戈壁组烃源岩的有机质丰度高、类型较好,是盆地的主力烃源岩层系,且油源对比结果证实,盆地已发现的油气均来源于该套烃源岩。银根-额济纳旗盆地的油气成藏过程可划分为早白垩世晚期油气成藏和早白垩世末期调整改造2个阶段,油气的富集主要受巴音戈壁组烃源岩的热演化程度和晚期构造活动强度共同控制。银根-额济纳旗盆地腹部是其油气富集的最有利区,中西部是油气勘探的有利区,中东部的油气成藏条件较差。     

Soldier defense secretions ofTrinervitermes bettonianus (Isoptera,Nasutitermitinae): Chemical variation in allopatric populations

The soldier defense secretions of major and minor soldiers of the East African nasute termiteTrinervitermes bettonianus were analyzed chromatographically and spectrometrically, and the diterpene and monoterpene constituents were determined for three allopatric populations. Incipient colonies from one population raised on food from a second population produced their population-specific terpene pattern independent of food source. Secretion compositions are thus genetically rather than nutritionally determined, in agreement with biosynthetic studies in other nasutes. A minor volatile constitutent, previously proposed to be 3-ethyl-2-octanol was re-identified as (R)-2-decanol.     

Chemical constituents and inhibitory activities of essential oils fromCyperus brevifolius andC. kyllingia

Cyperus brevifolius andC. kyllingia are two common weeds in Hawaii. The underground parts, including the rhizomes and roots, contain allelopathic essential oils, which may contribute to the aggressive spread of these weeds in grasslands and lawns. Although morphologically similar,C. kyllingia contains more essential oils thanC. brevifolius. Also, the former is rich in terpenes, including -cyperone, -selinene, and -humulene, while the latter is rich in C₁₇ to C₂₅ n-paraffins. These chemical differences agree with their inhibitory activities against indicator species and the general observation thatC. kyllingia is the more prevalent weed of the two.On leave from the Department of Agricultural Chemistry, Kinki University, Osaka, Japan.     

Chemical defense by termite soldiers

The chemistry of the defensive secretions of termite soldiers is reviewed. The structural variety of the chemical weapons, the uses of these substances in defense, and some potential biosynthetic interrelationships are discussed. Classification of the monoterpenes, sesquiterpenes, diterpenes, and various acetate-derived compounds according to termite subfamilies places the known defense substances in a phylogenetic perspective.     

荆条叶挥发油的气相色谱-质谱分析

利用气相色谱-质谱(GC/MS)联用技术分析荆条叶挥发油中的化学组成。结果表明:荆条叶挥发油中共分离出了36种组分,确定了29种成分的化学结构和相对含量,占总组分相对含量的94.68％。其中萜类及其衍生物22种,占89.13％。含量最高的成分是β-丁香烯(48.70％),其次是β-金合欢烯(15.52％)等。