Viniferone A, an oxidative derivative of catechin, together with viniferone B and C, presumably the oxidative derivatives of epicatechin, were isolated from grape seeds. Their structures were elucidated by spectroscopic methods. The X-ray structure of viniferone A is presented.

Separation of the water-soluble fraction of peanut skins led to the isolation of five proanthocyanidins. Based on the spectroscopic investigation and partial acid catalyzed degradation, their structures were determined to be epicatechin-(2β→O→7, 4β→6)-[epicatechin-( 4β→8)]-catechin (1), epicatechin-(2β→O→7, 4β→8) epicatechin-(4β→8)-catechin-(4a→8)-epicatechin (2), and procyanidins B2 (3), B3 (4) and B4 (5). The absolute configuration of the new compounds was determined from their circular dichroism curves and the 1H NMR spectra of analysis of flavan-3-ols formed by thiolytic degradation of 1 and 2 in the presence of a chiral dirhodium complex (dirhodium tetra-(R)-(trifluoromethyl) phenyl acetate).

From Peucedanum praeruptorum, one new khellactone ester (3′R)-O-acetyl-(4′S)-O-angeloylkhellactone (3), as well as four known angular dihydropyranocoumarins (1, 2, 4, 5) have been isolated. On the basis of NMR spectra and X-ray crystallography, their structures were determined. We have elucidated their absolute configuration by either chiral separation of their alkaline hydrolysis products with Rp-18 HPLC eluted with 5% hydroxypropyl-b-cyclodextrin (β-HCD) or by measurement of their CD spectra. A general rule relating the position and absolute stereochemistry of the khellactone esters to the sign of their Cotton effects in CD curves is proposed.

A separation method for the hepatoprotective drug silybin and its metabolites by RP-HPLC was described. Based on this separation, the stereoselectivity of the metabolism of silybin was investigated by incubation of the drug and its two diastereoisomers with bovine liver microsomes. Information about the structures of these metabolites was obtained, using UV, HPLC/MS and NMR spectra. Four major metabolites (M1, M4 of silybin A and M2, M5 of silybin B), were prepared by preparative HPLC, and their configurations were accomplished by NMR spectra. A HPLC method was used to quantify the metabolites. The results showed that silybin was extensively metabolized and the major sites for glucuronidation were the C-20, C-7, at phenolic OH groups. Furthermore, the results obtained reveal that there was significant stereoselectivity in the glucuronidation process of silybin. Silybin B was glucuronidated at a more efficient rate than its diastereoisomer, and glucuronidation of silybin B was much preferred at the 20 position, while that of silybin A was similar at both 7 and 20 position.

Abioanalytical method using liquid chromatography-tandem mass spectrometrywas developed for the analysis of fluconazole in Candida albicans after incubation with phenolic compounds, which have been proved possessing antifungal properties and have synergetic activity against C. albicans when in combination with fluconazole. Samples of C. albicans thallus obtained by centrifuging the mixed culture after 24h incubation were saponified and centrifuged. The supernatant was evaporated to dryness, reconstituted, and injected on a C18 column using an organic-aqueous mobile phase. The chromatographic run time was 3.5min per injection, with retention times of 2.4min for fluconazole. The detection was by monitoring fluconazole at m/z 305→191. The standard curve range was 1.0-100.0ng ml−1 with a mean correlation coefficient 0.9992. The precision and accuracy of the quality control (QC) samples were R.S.D.<5.5%, R.E.<3% for intra-day and R.S.D.<6.2%, R.E.<4% for inter-day. The concentration of fluconazole in C. albicans was found to be increased with the increment of the tested compounds concentration when they were in combination.