Chun Lei

Study on solid phase extraction and graphite furnace atomic absorption spectrometry for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent.

A solid phase extraction and graphite furnace atomic absorption spectrometry (GFAAS) for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent was studied. Trace amounts of chromium, nickel, silver, cobalt, copper, cadmium and lead were reacted with 2-(2-quinolinil-azo)-4-methyl-1,3-dihydroxidobenzene (QAMDHB) followed by adsorption onto MCI GEL CHP 20Y solid phase extraction column, and 1.0molL(-1) HNO(3) was used as eluent. The metal ions in 300mL solution can be concentrated to 1.0mL, representing an enrichment factor of 300 was achieved. The recoveries of analytes at pH 8.0 with 1.0g of resin were greater than 95% without interference from alkaline, earth alkaline and some metal ions. When detected with graphite furnace atomic absorption spectrometry, the detection limits in the original samples were 1.4ngL(-1) for Cr(III), 1.0ngL(-1) for Ni(II), 0.85ngL(-1) for Ag(I), 1.2ngL(-1) for Co(II), 1.0ngL(-1) for Cu(II), 1.2ngL(-1) for Cd(II) and 1.3ngL(-1) for Pb(II). The validation of the procedure was performed by the analysis of the certified standard reference materials, and the presented procedure was applied to the determination of analytes in biological, water and soil samples with good results (recoveries range from 89 to 104%, and R.S.D.% lower than 3.2%. The results agreed with the standard value or reference method).

Compounds from Kadsura heteroclita and related anti-HIV activity.

Phytochemical investigation of the stems of Kadsura heteroclita led to isolation of 16 compounds, including the triterpenoid named longipedlactone J (2), and two dibenzocyclooctadiene type lignans named heteroclitin I and J (3, 4). Compounds 8-10, 14, and 15 were weakly active as anti-HIV agents, whereas compounds 6 and 12 exhibited moderate anti-HIV activity with EC50 values of 1.6 microg/mL, and 1.4 microg/mL, therapeutic index (TI) values of 52.9, and 65.9, respectively. Their structures were established by spectroscopic methods, including application of 2D NMR techniques and CD spectra.

Lignans with Anti-HIV Activity from Schisandra propinqua var. sinensis

Fourteen new lignans, tiegusanins A-N (1-14), together with 13 known compounds were isolated from the aerial parts of Schisandra propinqua var. sinensis. The structures and absolute configurations of 1-13 were established using a combination of spectroscopic techniques. Compound 14 was obtained as a racemate. When evaluated for inhibitory activity against HIV-1, tiegusanin G (7) showed anti-HIV-1 activity with an EC(50) value of 7.9 microM and a therapeutic index (TI) of more than 25.

Propindilactones E-J, Schiartane Nortriterpenoids from Schisandra propinqua var. propinqua

Six new nortriterpenoids, propindilatones E-J (1-6), and two known (7, 8) schiartane-type nortriterpenoids were isolated from the stems of Schisandra propinqua var. propinqua. Their structures were elucidated by extensive spectroscopic analyses, and the structure of compound 4 was confirmed through single-crystal X-ray diffraction. The absolute configuration of compounds 1-3 was established using CD methods. Compounds 4-6 were noncytotoxic against K562, A549, and HT-29 human cancer cells.

Structure Elucidation and Theoretical Investigation of Key Steps in the Biogenetic Pathway of Schisanartane Nortriterpenoids by Using DFT Methods

Rubrifloradilactone C (4), a novel bioactive nortriterpenoid, along with four other nortriterpenoids (1-3, 5) were isolated from Schisandra rubriflora. The structure of 4 was determined by extensive NMR spectral analysis, computational evidence by using the GIAO method at the B3LYP/6-311++G(2d,p)//B3LYP/6-31G(d) levels, and X-ray analysis. DFT at the B3LYP/6-311+G(d,p) level was selected to clarify the key mechanistic steps in the formation of 1 and 4 through transition-state (TS) investigations. The effect of enzymes on the TS barriers was considered by using the polarized continuum model. Other possible products based on the new mechanism were predicted.

Schisanartane Nortriterpenoids with Diverse Post-modifications from Schisandra propinqua

Twenty-one highly oxygenated nortriterpenoids with a schisanartane skeleton were isolated from the stems of Schisandra propinqua var. propinqua. These nortriterpenoids featured a polycyclic framework composed of 7/8/5 consecutive carbocycles, which were organized by similar 5/5/7/5/7/5 rings A-F and varied oxygen-containing rings G and H. A biosynthetic classification of these compounds is proposed on the basis of their diverse post-modifications.

Intermedins A and B; New metabolites from Schisandra propinqua var. intermedia

A new dibenzocyclooctadiene lignan, intermedin A (1), and a new natural bisabolane sesquiterpenoid, intermedin B (2), were isolated from the aerial parts of Schisandra propinqua var. intermedia. Their structures were elucidated on the basis of extensive spectroscopical analysis.

Bisnortriterpenoids Possessing an 18-Nor-schiartane Skeleton from Schisandra propinqua var. propinqua

Six C (28) triterpenoids with an 18-nor-schiartane framework were isolated from the aerial parts of SCHISANDRA PROPINQUA var. PROPINQUA. The new compounds, propindilactones P-S ( 1- 4), were structurally characterized by extensive spectroscopic methods. New compounds 2 and 3, together with known wuweizidilactones B and H ( 5- 6), were evaluated for their anti-HBV activity.

Propinic lactones A and B, two new triterpenoids from Schisandra propinqua var. propinqua and the significance in biosythesis pathway.

Abstract Aim To study the chemical constituents of the aerial parts of Schisandra propinqua var. propinqua . Method Silica gel, C 18 reversed phase silica gel and HPLC were used. The structures were elucidated by extensive spectroscopic methods. Result Two new triterpenoids, propinic lactone A ( 1 ) with 3, 4- seco -cycloartane skeleton, and propinic lactone B ( 2 ) possessing 3, 4:9, 10- seco -cycloartane skeleton, together with a known typical cycloartane triterpenoid, schizandronic acid ( 3 ), have been isolated and identified. Conclusion These two new triterpenoids serve as two important bridge intermediates from cycloartane triterpenoids to Schisandra nortriterpenoids biogenetically.

ent-Kaurane Diterpenoids from Isodon japonicus

Two new 6,7-seco-ent-kaurane diterpenoids, isojaponins A (1) and B (2), together with 18 known ent-kaurane diterpenoids were isolated from the aerial parts of Isodon japonicus. The structures of the two new compounds were elucidated by extensive 1D- and 2D-NMR spectroscopic methods in combination with MS experiments.