TLC Bioautographic Assay Research Articles

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.

Four chromones from Eriosema tuberosum

Four new prenylated chromones have been isolated from a dichloromethane extract of the roots of Eriosema tuberosum. Their structures were elucidated by spectroscopic methods. Eriosematin A exhibited antifungal activity against Cladosporium cucumerinum and Candida albicans in TLC bioautographic assays.

Cinnamate esters of catalpol from Westringia fruticosa and Westringia viminalis

Two cinnamate esters of catalpol were isolated from Westringia fruticosa and Westringia viminalis. They were identified as 6- O-([ Z]-4-methoxycinnamoyl)-catalpol and 6- O0([ E])-3,4-dimethyoxycinnamoyl) catalpol by spectroscopic methods. The former appears to be novel. Each exhibited antifungal activity against the plant pathogenic fungus Cladosporium cucumerinum. Minimum inhibitory doses were 10 and 25 μg, respectively, with activity persisting for 48 h in the direct TLC bioautography assay. The concentration of 6- O-([ Z]-4-methoxycinnamoyl) catalpol in the two species of Westringia was variable but detectable in all samples. Concentrations were significantly greater (P<0.05) in W. fruticosa but there was overlap between the two taxa.

Antibacterial phloroglucinols and flavonoids from Hypericum brasiliense

Three known phloroglucinols (japonicine A, uliginosin A and isouliginosin B) and a new phloroglucinol (hyperbrasilol 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 13C NMR, 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.

New procedure for direct bioautographic TLC assay as applied to a tincture of Ranunculus bulbosus

A new procedure for TLC bioautographic assay using a flooding method to inoculate the developed plates is described. Details about several microbiological parameters allow good reproducibility for this method which appears rapid, easy to perform and requiring no specialized equipment. Significantly results obtained with a commercial tincture of Ranunculus bulbosus illustrate this method which can be extented to complex mixtures of natural products in order to isolate active fractions.