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We developed a general HPLC method for the discrimination of (D,L)-monosaccharide components from natural products. The reaction involves the preparation of L-cysteine (3-nitrophenyl) methyl ester hydrochloride, which reacts with aldoses leading to thiazolidine derivatives. Direct HPLC analysis with reversed-phase column and UV detection, discriminated enantiomeric D- and L-monosaccharides in a highly sensitive manner. This method was applied for the determination of the absolute configurations of monosaccharides in the natural poliumoside B, a tetraglycoside obtained from Teucrium polium.

Three new furostanol saponins named capsicoside E (1), capsicoside F (2), and capsicoside G (5) were obtained from the seeds of Capsicum annuum L. var. acuminatum along with known oligoglycosides (3, 4, and 6-10). On the basis of chemical and spectroscopic analyses, the structures of these new furostanol oligoglycosides were elucidated as 26-O-beta-D-glucopyranosyl-22-O-methyl-5alpha-furost-25(27)-en-2alpha,3beta,22xi,26-tetraol-3-O-beta-D-glucopyranosyl(1-->3)-beta-D-glucopyranosyl(1-->2)-[beta-D-glucopyranosyl(1-->3)]-beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside (1), 26-O-beta-D-glucopyranosyl-(25R)-5alpha-furost-20(22)-en-2alpha,3beta,26-triol-3-O-beta-D-glucopyranosyl (1-->3)-beta-D-glucopyranosyl(1-->2)-[beta-D-glucopyranosyl(1-->3)]-beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside (2), and 26-O-beta-D-gluco-pyranosyl-(25R)-5alpha-furosta-3beta,22xi,26-triol-3-O-beta-D-glucopyranosyl(1-->3)-beta-D-glucopyranosyl(1-->2)-[beta-D-glucopyranosyl(1-->3)]-beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside (5). The isolated saponins showed higher antimicrobial activity against yeasts than against common fungi. Data indicated that the antiyeast activity was related to the combination of the oligosaccharide chain (S1, S2, or S3) with an O-methyl group at R(3) and the presence of a hydroxyl group at the C-2 position.

In the present study, the chemical composition and antioxidant activities of Teucrium polium L. (Lamiaceae) were assessed. Fractionation of methanol extract obtained from the aerial parts of T. polium yielded one new phenylethanoid glycoside, named poliumoside B, together with four known flavonoids, two iridoid glycosides and a known poliumoside. The structures of all of these compounds were elucidated on the basis of spectroscopic data from 1D and 2D NMR experiments and MS spectral analyses. The antioxidant activities of the crude extracts and of the isolated compounds were evaluated through tests such as DPPH radical-scavenging capability, reducing power, xanthine oxidase inhibitory effect and inhibition of linoleic acid peroxidation. The highest antioxidant activity was found in the n-butanol extract, which also contained active polyphenols, thus suggesting that this plant could be used as a source of natural molecules, to provide safe antioxidant additives and nutraceuticals. The structure–activity relationships of the isolated compounds are also discussed.

A new phenolic glycoside ( E )-4-hydroxycinnamyl alcohol 4- O -(2′- O -β- d -apiofuranosyl)(1″ → 2′)-β- d -glucopyranoside ( 1 ) was isolated and identified from Cucumis melo seeds together with benzyl O -β- d -glucopyranoside ( 2 ), 3,29- O -dibenzoylmultiflor-8-en-3α,7β,29-triol ( 3 ) and 3- O - p -amino-benzoyl-29- O -benzoylmultiflor-8-en-3α,7β,29-triol ( 4 ). Their structures were elucidated by extensive NMR experiments including 1 H– 1 H (COSY, TOCSY, ROESY) and 1 H– 13 C (HSQC and HMBC) spectroscopy and chemical evidence. The multiflorane triterpene esters were identified as new melon constituents.

A phytochemical analysis of Aster sedifolius has led to the isolation of three novel triterpenoid saponins, based on an oleane-type skeleton and named astersedifolioside A (1), B (2) and C (3). On the basis of chemical, and 2D NMR and mass spectrometry data, the structures of the new compounds were elucidated as 3-O-[alpha-L-rhamnopyranosyl (I --> 2)-beta-D-glucopyranosyl] echinocystic acid 28-[O-alpha-L-rhamnopyranosyl (I --> 2)-alpha-L-arabinopyranoside] (1), 3-O-[alpha-L-rhamnopyranosyl (1 --> 2)-beta-D-glucopyranosyl] echinocystic acid 28-[O-beta-D-xylopyranosyl (1 --> 4)-O-alpha-L-rhamnopyranosyl (1 --> 2)-alpha(-L-arabinopyranoside] (2) and 3-O-[alpha-L-rhamnopyranosyl (I --> 2)-beta-D-glucopyranosyl (I --> 2)-alpha-D-glucopyranosyl] echinocystic acid 28-[O-beta-D-xylopyranosyl (I 4)-O-alpha-L-rhamnopyranosyl (I --> 2)-alpha-L-arabinopyranoside] (3). The isolated compounds showed antiproliferative effect in KiMol, a transformed thyroid cell line. (C) 2004 Published by Elsevier Ltd.

Investigation of polar extracts from ripe fruits of Capsicum annuum L. var. acuminatum yielded three new glycosides, capsosides A (1) and B (2) and capsianoside VII (3), along with seven known compounds (4-10). The chemical structures were elucidated mainly by extensive nuclear magnetic resonance methods and mass spectrometry, and the biological activities of icariside E(5) (4) were tested by different assays. Icariside E(5), in contrast to capsaicin, neither induces an increase in the intracellular levels of reactive oxygen species nor affects the mitochondria permeability transition, and it does not signal through the vanilloid receptor type 1. Interestingly, this compound protects Jurkat cells from apoptosis induced by the oxidative stress mediated by serum withdrawal. These results suggest that icariside E(5) may have antioxidant properties that strengthen the importance of peppers in the Mediterranean diet.