Reminiscences of research on the chemistry and biology of natural sterols in insects,plants and humans

Natural sterols often occur as a heterogeneous mixture of homologs, which had disturbed the progress of steroid research. Development and application of GC methodology overcame this difficulty and enabled us to obtain detailed sterol profiles. Together, fine synthesis of stereo-defined isomers and homologs of steroids having oxygenated side chains allowed us to compare them with natural samples as well as to investigate structure-activity relationship. Advance of HPLC technology also facilitated the determination of the stereochemical structure of naturally occurring steroidal compounds, which were obtained only in minute amounts. This review highlights three topics out of our steroid research that have been performed mainly at Tokyo Institute of Technology around 1970–1990. These are sterol metabolism in insects focusing on the mechanism of the conversion of plant sterols to cholesterol and ecdysone biosynthesis, the synthesis and biochemical research of active forms of vitamin D₃ derivatives, and the synthesis and microanalysis of plant hormone brassinosteroids.     

油菜素内酯对干旱胁迫下辣椒开花结果的影响

以辣椒品种湘研6号为材料,研究了干旱胁迫下0.05mg/L的油菜素内酯(BR)对辣椒开花结果的影响。结果表明,BR处理促进了正常生长条件下辣椒的开花和花粉在柱头上的萌发率,增加了辣椒的结果及产量;干旱胁迫导致辣椒开花数的下降和落花率的增加,显著抑制了花粉活力和花粉在柱头上的萌发率,引起结实数的下降和落果率的上升,最终降低了其产量;BR则显著促进了干旱胁迫下辣椒的开花、花粉活力以及花粉在柱头上的萌发率,有利于干旱胁迫下辣椒总产量、单果重和千粒重的增加,减缓了干旱胁迫对辣椒开花结果的抑制作用。     

油菜素甾族化合物对植物干旱适应性的影响及调控机理

总结了油菜素甾族化合物对植物渗透系统、保水性、抗氧化系统及生长和发育的生理效应的最新进展,并概括了这些现象的生理和分子调控机制.综述了BR调节植物干旱适应性的基因应答路径,这些路径与其他主要干旱胁迫激素(如脱落酸)之间存在复杂的"信号交互"效应,共同对植物生长发育起到系统调控作用.该方面的创新研究将是BR在生产应用上取得突破的理论基础.     

基于在线富集与原位衍生技术的植物组织中内源性油菜素甾醇的超高效液相色谱-串联质谱分析方法

油菜素甾醇是一类重要的植物激素,对植物的生长发育过程起显著调节作用。已报道的油菜素甾醇分析方法存在样品前处理过程复杂和灵敏度低等问题。本研究采用C18 PEEK管填充柱为富集柱,以4-N,N-二甲氨基苯硼酸为衍生试剂,搭建了基于双泵-双六通阀的在线管内固相微萃取-超高效液相色谱-串联质谱（UPLC-MS/MS）联用系统,对油菜素甾醇进行在线富集和原位衍生,实现植物组织中内源性油菜素甾醇的自动化分析。该系统程序化地控制了油菜素甾醇的进样、萃取、衍生、分离和检测过程,有效简化前处理过程,节省人力;在线富集步骤实现了样品溶液大体积进样,提高样品利用率;原位衍生改善了油菜素甾醇电喷雾的离子化效率,使油菜素甾醇的电喷雾质谱检出限降低至pg/mL。该系统可在300 mg鲜重植物组织中检测到内源性油菜素甾醇,已成功用于水稻、油菜中多种油菜素甾醇的定量分析。     

dst6,拟南芥中一个可能的新的det2等位基因突变株

在黑暗条件下筛选拟南芥滞绿突变体时,得到一株突变体,dst6,表现出典型的油菜素突变体的特征．遗传分析表明其是单基因隐性突变．利用简单序列多态性标记,将其定位于2号染色体的底部．粗定位的结果和形态学特征表明dst6可能是一个det2等位基因突变株．通过对(dst6中DET2基因的测序分析,证明了dst6可能是一个新的det2等位基因突变株．     

Luminescence of biologically active 24-epicastasterone and a model compound

Biologically active brassinosteroid 24-epicastasterone, ring B of which contains a C=O group and has the nπ*-configuration for a low-lying electronic excited state, exhibits rapid fluorescence. The wavelengths of the fluorescence maxima of the steroid dissolved in hexane and acetonitrile are equal to 332 and 394 nm, respectively. The fluorescence lifetime of the steroid dissolved in acetonitrile is τ = 9.9 nsec. Solutions of 24-epibrassinolide do not luminesce. The long-wavelength electronic absorption band λ_max^abs = 340 nm in the absorption spectrum of an ethanol solution of model compound 2, ring D of which contains a C=O group π*-conjugated with the C=C double bond of ring C, like in the spectrum of the steroid, has a low extinction coefficient. An ethanol solution of 2 does not fluoresce. 24-Epicastasterone at 77 K in ethanol solution exhibits phosphorescence with λ_max^phos = 447 nm. The phosphorescence decay is exponential with τ = 0.79 msec. Compound 2 also phosphoresces. The phosphorescence spectrum of its ethanol solution has a maximum at 490 nm. The phosphorescence decay is nonexponential in the early stage. The phosphorescence lifetime is 25 msec in the exponential decay region. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 182–186, March–April, 2008.     

Manifestation of structure and intermolecular interactions of biologically active brassinosteroids in infrared spectra

We have analyzed the IR spectra obtained for steroidal phytohormones 24-epibrassinolide, 24-epicastasterone, 28-homobrassinolide, and 28-homocastasterone. The characteristic frequencies of the stretching vibrations of the hydrocarbon groups CH₃, CH₂, and CH and also the C=O groups in the spectra of brassinolides are higher than in the spectra of castasterones, which makes it possible to identify them from the IR spectra. Study of the spectra of these brassinosteroids in different media (pressed samples in KBr, films, solutions in CHCl₃ and CDCl₃) allowed us to establish the presence of intermolecular interactions in which C=O and OH groups, OH-OH groups participate, and also the possible formation of intramolecular hydrogen bonds between the OH groups of the molecules. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 610–616, September–October, 2007.