MPLC fractionation

General Experimental Procedures MPLC fractionation was performed using an Isco CombiFlash, and HPLC isolation was performed using Shimadzu pumps and detector and YMC-Pack ODS-AQ C18 column. 

In order to reduce the time-consuming open-column chromatographic processes, conventional methods of hydrocarbon-group-type separation have been replaced by MPLC and HPLC. Flash column chromatography is a technique less commonly applied than open-column version, but several applications have been described [2,24—27]. The common technique version is to use a silica-gel-filled column for example, 230 to 400 mesh 20 X 1 cm column size with a back pressure of 1.5 X 10 Pa of an ambient gas such as nitrogen. Solvents are similar to the ones apphed in the case of open-column chromatography fractionations. 

Studies on HPLC with iridoids of Apoc)maceae focus mainly on the separation of components from extracts or fraction. The chromatography profile, the identification and quantification of these terpenes in the extracts are described. Table 4 shows the principal references on iridoids isolated from Apoc)maceae by HPLC, MPLC and LPLC. 

MPLC and HPLC 30% acetonitrile in water to 50% acetonitrile (45 X 3.5 cm) and Shimpack C-18 (10[im,45 cm x Himatanthus sucuuba/latex fraction and fractions from this 15-demethylisoplumieride, 15-demethylplumieride, plumieride and isoplumieride [70]... 

The checkers found that MPLC can be replaced by ordinary flash chromatography (30% EtOAc-hexane eluant, 6-cm I.D. column, - 200-240 g of flash-grade silica gel 230-400 mesh, 250-mL fractions). The crude product was dissolved in Cl Clg to which was added several grams of silica gel. This mixture was concentrated under reduced pressure and the resulting solid was applied to the top of the column. 

It was found that root bark, containing egg cavities with feces, were avoided by the pine weevil H. abietis, so its feces were investigated in an attempt to find ways to control the weevil. After fractionation by medium-pressure liquid chromatography (MPLC) and analysis with gas chromatography-mass spectroscopy (GC-MS)... 

Sample preparation. For the study of trace compounds we used two different sample preparation procedures SPI and SPII for wine no. 1 and wine no. 2, respectively. The first flavor extract SP I was obtained by liquid-liquid extraction with fluorochloromethane and dichloromethane (9+1) from 45 L Scheurebe wine. For further analysis a portion of 1/3 was used. After separation on silica gel (pentane/diethyl ether) 6 fractions were analyzed. For the second flavor extract SP II we started from 200 L wine stripping off volatile compounds with vapour in a spinning cone column (SCC) system (5). The condensate was sequentially collected in two main portions of 8 and 2 L, respectively. The first condensate was discarded. The second condensate (2 L) was subjected to liquid-liquid extration with fluorochloromethane and dichloromethane (9+1). After separation on silica gel (pentane/diethyl ether) using medium pressure chromatography (MPLC) 4 fractions were analyzed. 

It is very useful to have the mplc system linked to a fraction collector, -r.y kind of fraction collector will work, but we use a Gilson computer... 

A uv or refractive index detector can also be incorporated into the stem, or the fractions can simply be analysed by tic, as for flash. "omatography. If the conditions are kept constant the results from mplc 133 very consistent, so if you wish to repeat separations of the same iixture, it is very easy to predict which fractions will contain each rmponent... 

A standard methodology was used for the fractionation of these. Thus, the MeOH extract of aerial parts of B. rigidum was partitioned between n-BuOH and water. The w-BuOH soluble fraction was chromatographed over a silica gel column, followed by repeated MPLC purification to give seven pure compounds. 

Reaction of benzaldehyde with Bu AlTeBu (typical procedure) In a flame-dried flask equipped with an Ar inlet and a rabber septum was placed n-BuTeTeBu-n (185 mg, 0.5 mmol). After BU2AIH (1 N in hexane, 1 mL) was added under Ar, the solution was stirred at 25°C for 1 h and then 2 mL of THF was added. The solution was cooled to -23°C and 2 mmol of benzaldehyde and 0.5 mL of EtjAlCl (1 N in hexane) were injected. The mixture was gradually warmed to 25°C, stirred for another 1 h and poured into saturated NH Cl solution. Products were extracted with EtjO (3X30 mL), dried over MgS04 and concentrated in vacuo. Medium pressure liquid chromatography (MPLC) of the residue gave pure Te-butyl tellurobenzoate in 71% yield (205 mg) in a hexane/Et20 (100 1) fraction. 

The MeOH extract of the freshly collected whole plant of S. officinalis was suspended in water and partitioned successively with EtOAc and n-BuOH. The aqueous part, on chromatography over Diaion HP-20 followed by repeated MPLC and HPLC purification afforded two major triterpenoid saponins, saponariosides A and B. Similarly, the -BuOH soluble fraction afforded six triterpenoid saponins designated as saponariosides C-H. Investigation of the plant material collected from different geographical locations led to the isolation of previously reported saponariosides C, E, F and G along with five more new saponins, saponariosides I-M (Fig. 7), from which two new sapogenins have been characterized as VIII and XII (Fig. 1). However, saponarioside D, the major constituent of the -BuOH soluble fraction as reported previously by us [21], could not be detected. 

Rock samples were extracted using methylene chloride and a Soxhlet apparatus and the resulting extract was further fractionated by a semi-quantitative SARA separation. After asphaltenes were removed from the concentrated extract by precipitation with excess pentane, the pentane soluble portion of the sample was separated by medium-pressure liquid chromatography (MPLC) using a deactivated silica gel precolumn and an activated silica gel main column by eluting the saturate and aromatic hydrocarbon fractions from the activated silica column with hexane in the forward and back-flush modes respectively. Polar nonhydrocarbons were backflushed from the precolumn with methylene chloride-methanol. Carbon isotopes were done on a subset of hydrocarbon fractions at Coastal Sciences Labs, Austin, TX (Table 3). 

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