Gao M

Cytotoxic biflavones from Stellera chamaejasme.

Bioassay-guided phytochemical studies on Stellera chamaejasme led to the isolation of two new biflavones, chamaejasmenin E (1) and chamaejasmin D (2), together with ten known compounds. The structures of new compounds were elucidated by extensive spectroscopic analyses and their absolute configurations on 2, 3, 2″ and 3″ were confirmed by TDDFT quantum chemical calculated ECD spectra combined with experimental ECD spectra. All isolated biflavones were evaluated for their cytotoxic activities against Bel-7402 and A549 tumor cell lines, and sikokianin D (3) was found to possess the most potential cytotoxic activities against both the two cell lines with IC50 values of 1.29 ± 0.21 and 0.75 ± 0.25 μM, respectively. Moreover, some structure-function relationships of these bioflavones for cytotoxic activities were explored and summarized.

A new diterpenoid from Rhizophora apiculata

A new diterpenoid, 15(S)-isopimar-7-en-1-oxo-15,16-diol (1), was isolated from the stems of mangrove plant Rhizophora apiculata. The structure of the new compound was elucidated by MS, IR, 1D, and 2D NMR techniques, including HMQC, HMBC, and NOESY correlations. In addition, seven known constituents were isolated from this plant for the first time.

Polarity, selectivity and performance of hydrophilic organic/salt-containing aqueous two-phase system on counter-current chromatography for polar compounds.

The essential attributes of a solvent system for separation polar compounds on CCC are polarity, selectively and performance. Here, hydrophilic organic/salt-containing aqueous two-phase system (HO/S TPS) was evaluated as an alternative solvent system for CCC separation of polar compounds. Polarity measurements based on Rohrschneider-Snyder parameter was developed as quantitative assessing the polarity of HO/S TPS and comparing with an organic/aqueous system. All investigated 1-butanol/ethanol/saturated ammonium sulfate solution/water (BEAsWat) and 1-butanol/ethanol/saturated dipotassium hydrogen phosphate solution/water (BEDhpWat) systems with polarity values of organic phase from 4.5 to 6.8, were more polar than chloroform/methanol/water (1/1/1). The considerable water content of BEAsWat and BEDhpWat (0/1/1/1/) was 45.4 and 42.6% (w%) of hydrophilic organic phase, and 66.4 and 51.2% (w%) of salt-containing aqueous phase, respectively, closed to conventional aqueous two-phase system. Therefore, the polarity of HO/S TPS is in the middle of organic/aqueous and aqueous two-phase system. The LogKC values of twenty four polar compounds as model mixture confirmed that the polarities of HO/S TPSs were matched to that of the polar compounds and shown to be a very selective technique capable of separating positional isomers. Moreover, BEAsWat and BEDhpWat systems can be easily retained in CCC column with suitable elution mode. The hydrodynamic behavior reversion of HO/S TPS on hydrodynamic CCC was observed and was tentatively explained based on the density difference. Finally, caffeoylquinic acid isomers and dihydroxybenzoic acid isomers were successfully separated with HO/S TPS on CCC, respectively. Those results demonstrate that HO/S TPS on CCC is a performant and stable way to separate polar compounds from natural products.

A novel preparative liquid chromatograph for repetitive enrichment and purification of low-abundance compounds

A novel recycle preparative HPLC system was developed to repeatedly enrich and purify low-abundance compounds from complex samples. The recycle separation involves injecting a large volume of the sample through a trap column, releasing the absorbed sample for preparative HPLC separation, and then capturing the target component in the same trap column for the next separation. After several cycles, the final purified target compound absorbed in the trap column is eluted with a small volume of solvent. The capture and recycle procedure was realized by adjusting the strength of the mobile phase using an auxiliary pump and switching the two valves connecting the trap and preparative columns. Compared with standard HPLC or existing recycle chromatography, this system not only reduces the solvent side-effects and sample volume overloading during injection but also avoids peak-broadening and sensitivity loss during the recycle runs. Moreover, the final purified products can be easily concentrated. With the aid of this system, a 10% polyphenol in extracts from Saussurea involucrata cultured cells reached >95% purity with more than 95% recovery after three recycle purifications, and a 1% unstable epimer impurity in the raw material of the drug silybin reached >95% purity with 75% recovery after a six-cycle separation.