Olivier Potterat

Goji (Lycium barbarum and L. chinense): Phytochemistry, pharmacology and safety in the perspective of traditional uses and recent popularity.

Since the beginning of this century, Goji berries and juice are being sold as health food products in western countries and praised in advertisements and in the media for well-being and as an anti-aging remedy. The popularity of Goji products has rapidly grown over the last years thanks to efficient marketing strategies. Goji is a relatively new name given to Lycium barbarum and L. chinense, two close species with a long tradition of use as medicinal and food plants in East Asia, in particular in China. While only L. barbarum is officinal, the fruit (fructus Lycii) and the root bark (cortex Lycii radicis) of both species are used in the folk medicine. We review here the constituents, pharmacology, safety, and uses of L. barbarum and L. chinense with consideration to the different parts of the plant. Investigations of the fruit have focused on proteoglycans, known as Lycium barbarum polysaccharides, which showed antioxidative properties and some interesting pharmacological activities in the context of age related diseases such as atherosclerosis and diabetes. As to the root bark, several compounds have demonstrated a hepatoprotective action as well as inhibitory effects on the rennin/angiotensin system which may support the traditional use for the treatment of hypertension. While there are no signs of toxicity of this plant, two cases of possible interaction with warfarin point to a potential risk of drug interaction. In view of the available pharmacological data and the long tradition of use in the traditional Chinese medicine, L. barbarum and L. chinense certainly deserve further investigation. However, clinical evidences and rigorous procedures for quality control are indispensable before any recommendation of use can be made for Goji products.

Antibacterial phloroglucinols and flavonoids from Hypericum brasiliense

Three known phloroglucinols (japonicine A, uliginosin A and isouliginosin B) and a new phloroglucinol (hyperbrasiol A) have been isolated from a petrol extract of the leaves and flowers of Hypericum brasiliense. Their structures were established by spectroscopic methods (UV, DCI-MS, 1H and 13CNMR, including SINEPT, HMBC, HSQC, DQFCOSY experiments). The substitution pattern of hyperbrasilol A was confirmed by X-ray crystallography. All four phloroglucinols were antibacterial against Bacillus subtilis in a TLC bioautographic assay. The flavonoids, kaempferol, luteolin, quercetin, quercitrin, isoquercitrin, hyperoside and guaijaverin, were isolated from a methanol extract of the same organs.

Xanthones from Hypericum roeperanum

Four new xanthones have been isolated from the roots of Hypericum roeperanum. Their structures have been established by a combination of spectroscopic and chemical methods as 1,6-dihydroxy-5-methoxy-4,5-dihydro-4,4,5-trimethylfurano- (2,3:3,4)-xanthone (5-O-methyl-2-deprenylrheediaxanthone B), 1,6-dihydroxy-5-methoxy-6,6-dimethylpyrano-(2,3:3,4)-xanthone (5-O-methylisojacareubin), 1,3,5,6-tetrahydroxy-2-(2,2-dimethyl-4-isopropenyl)-cyclopen tanylxanthone (5-O-demethylpaxanthonin) and 1,3,5,6-tetrahydroxy-4-trans-sesquilavandulylxanthone (roeperanone). In addition, 2-hydroxyxanthone, 5-hydroxy-2-methoxyxanthone, 1,5-dihydroxy-2-methoxyxanthone, 2-deprenyl rheediaxanthone B, isojacareubin and calycinoxanthone D have been isolated and characterized. Some of the isolated xanthones exhibited antifungal activity against Candida albicans.

More phloroglucinols from Hypericum brasiliense

Three new phloroglucinols (hyperbrasilols B and C, and isohyperbrasilol B) have been isolated from a petrol extract of the leaves and flowers of Hypericum brasiliense. Their structures were established by spectroscopic methods including two-dimensional-NMR heteronuclear correlations. EI and D/Cl-mass spectral, NMR, IR and UV data are reported. All three phloroglucinols were antibacterial against Bacillus subtilis in a TLC bioautographic assay.

A stilbene and dihydrochalcones with radical scavenging activities from Loiseleuria procumbens.

A new dihydrochalcone, 6-acetylphloridzosid, was isolated from the whole plant of Loiseleuria procumbens (L.) Desv. and identified as 2-O-(6-O-acetylglucopyranosyl)-4,4,6-trihydroxydihydrochal cone by spectroscopic methods. In addition, one stilbene and three other dihydrochalcones were identified as (E)-piceid, phloretin (2,4,4,6-tetrahydroxydihydrochalcone), phloridzosid (2-O-glucopyranosyl-4,4,6-trihydroxydihydrochalcone) and asebotin (2-O-glucopyranosyl-4-methoxy-4,6-dihydroxydihydrochalcone), respectively. Some of these compounds showed scavenging properties towards the 2,2-diphenyl-1-picrylhydrazyl radical and antioxidant properties in a test with lysozyme.

Flavonoids and phenylpropanoid derivatives from Campanula barbata

Four new phenylpropanoid derivatives, barbatosides A-D, and a new catechin, barbatoflavan, were isolated from the whole plant of Campanula barbata L. (Campanulaceae) and identified as wahlenbergioside-3-O-glucoside, wahlenbergioside-3-O-(2-(p-methoxycinnamoyl))-glucoside, wahlenbergioside-3-O-(4-(trans-p-coumaroyl))-glucoside, wahlenbergioside-3-O-(4-(cis-p-coumaroyl))-glucoside and 3-acetyl-5-methoxy-7,3,4-trihydroxy-8-O-glucoside-flavan-3-ol, respectively, by spectroscopic methods. In addition, four flavonols were isolated and identified as kaempferol-3-O-glucoside, kaempferol-3-O-rutinoside, quercetin-3-O-glucoside and quercetin-3-O-rutinoside. Barbatoflavan demonstrated scavenging properties towards the DPPH radical.

Four iridoid glucosides and a phenylpropanoid glycoside from Sesamum angolense

Abstract A new iridoid glucoside, sesamoside, isolated from Sesamum angolense (Pedaliaceae), has been assigned the structure methyl antirrinoside-4-carboxylate. It was accompanied by the known iridoid glucosides phlomiol, pulchelloside-I and 6β-hydroxyipolamiide, and by the phenylpropanoid glycoside verbascoside. The identities of these compounds were deduced by spectroscopic methods. The structure of sesamoside was confirmed by conversion into its pentaacetate and diisopropylidene derivatives.

Library-based discovery and characterization of Daphnane diterpenes as potent and selective HIV inhibitors in Daphne gnidium

Despite the existence of an extended armamentarium of effective synthetic drugs to treat HIV, there is a continuing need for new potent and affordable drugs. Given the successful history of natural product based drug discovery, a library of close to one thousand plant and fungal extracts was screened for antiretroviral activity. A dichloromethane extract of the aerial parts of Daphne gnidium exhibited strong antiretroviral activity and absence of cytotoxicity. With the aid of HPLC-based activity profiling, the antiviral activity could be tracked to four daphnane derivatives, namely, daphnetoxin (1), gnidicin (2), gniditrin (3), and excoecariatoxin (4). Detailed anti-HIV profiling revealed that the pure compounds were active against multidrug-resistant viruses irrespective of their cellular tropism. Mode of action studies that narrowed the site of activity to viral entry events suggested a direct interference with the expression of the two main HIV co-receptors, CCR5 and CXCR4, at the cell surface by daphnetoxin (1).

Flavonol glycosides from Vernonia galamensis ssp. nairobiensis

Abstract A new flavonol glycoside has been isolated from the leaves of Vernonia galamensis ssp. nairobiensis . Its structure has been established as isorhamnetin 3-O-β- d -apio- d -furanosyl (1→2)-β- d -galactopyranoside on the basis of spectral data (UV, 1 H and 13 C NMR, D/CIMS) and by acid hydrolysis. Characterization of the peracetate derivative confirmed the configuration of the apiosyl moiety. In addition, the known flavonol glycosides; quercetin 3-galactoside, quercetin 3-apiosyl(1→2)galactoside and quercetin 3-rhamnosyl(1→6)galactoside have been isolated and identified.

A new potent antifungal 'quinone methide' diterpene with a cassane skeleton from Bobgunnia madagascariensis.

A new quinone methide diterpene with a cassane skeleton was isolated from the root bark of Bobgunnia madagascariensis (DESV.) J.H. KIRKBR. et WIERSEMA (Leguminosae). Its structure was established as (4bS,8aS)-4b,5,6,7,8,8a-hexahydro-4-hydroxy-2-(2-hydroxyethyl)-1,4b,8,8-tetramethylphenathrene-3,9-dione by spectroscopic methods including single-crystal X-ray analysis. This compound showed strong antifungal properties towards human pathogenic fungi, in particular the yeast Candida albicans.