A high-speed counter-current chromatography system (HPCCC) capable of rapid processing has been employed to separate seven flavonoids from a methanolic extract of the leaves of Oroxylum indicum by a one-step isocratic elution using a chloroform–methanol–water (9.5:10:5) two-phase system. LC, MS and NMR have identified the components from the extract as chrysin, baicalein, baicalein-7-O-glucoside, baicalein-7-O-diglucoside, chrysin-7-O-glucuronide, baicalein-7-O-glucuronide, and a chrysin-diglucoside. Baicalein-7-O-glucuronide and chrysin-7-O-glucuronide have been separated from this plant by HSCCC for the first time. The present study also reports a new chrysin-diglucoside from the leaf extract. The results demonstrate that HSCCC is a powerful separation tool and can contribute to identifying and quantifying plant ingredients.
Towards the synthesis of the novel natural product Agariblazeispirol C, (5aR*,11bR*)‐9‐methoxy‐3,8,11b‐trimethyl‐5,6,7,11b‐tetrahydro‐1H‐pentaleno[1,6a‐a]naphthalen‐4(2H)‐one, C20H24O2, has been prepared at a key stage of the preparative programme. The structure shows the desired stereochemical outcome of the central cyclization protocol, viz. a syn‐relationship between the aliphatic methyl group on the 11b‐position and the methylene group on the 5a‐position [C—C—C—C = −34.57 (18)°]. 相似文献
Two racemic fluoropyridine analogues 4 and 5 of the potent nicotinic agonist UB-165 have been synthesized. Halogenated pyridines 7 and 12 provided the organometallic reagents needed for the Negishi and Suzuki coupling reactions used for the preparation of 4 and 5, and the N-vinyloxycarbonyl protecting group of 8 and 15 was cleaved using a novel trifluoroacetic acid-mediated deprotection protocol. Analogue 4 retained high binding affinity at rat brain alpha4beta2 and alpha7 nicotinic receptors. 相似文献
A new synthesis of the peripheral benzodiazepine receptor ligand, PK11195 has been developed in only six-steps using a Heck-type reaction and a Suzuki coupling to effect the key transformations. The flexibility of this new approach is demonstrated by the synthesis of an iodo-analogue of PK11195 prepared from the corresponding bromide using a copper catalysed aromatic Finkelstein reaction. 相似文献
A fluorescein (Fl)-labeled DNA monolayer on Au was formed such that under applied potentials of -750 mV (vs. Ag/AgCl) and incident irradiation (473 nm, 4 mW cm(-2)) a photocurrent was generated that ultimately reduced NAD(P)+ to biologically active NAD(P)H. 相似文献
Three principal methods have been developed for measuring femtomoles of damage in nanogram quantities of non-radioactive DNA. Lesions which can be quantified include single and double strand breaks, alkali labile sites including apurinic and apyrimidinic sites, and pyrimidine dimers. The first in vitro method measures the conversion of supercoiled DNA to relaxed or linear molecules, and can detect up to four lesions per molecule. The second in vitro method (supercoil depletion) assesses the fraction of intact linear molecules of homogeneous length, and allows detection of 8 lesions/molecule. The third method, measurement of molecular length distributions of DNAs of heterogeneous length, reveals the extent of DNA damage and repair in vivo or in vitro. 相似文献