Fifteen crude extracts prepared from seven Ethiopian medicinal plants used to treat various infectious diseases were assessed for their ability to inhibit the growth of Mycobacterium tuberculosis. A preliminary screening of the crude extracts against M. tuberculosis typus humanus (ATCC 27294) was done by dilution assay using Löwenstein-Jensen medium. None of the tested extracts except the acetone fraction obtained from the stem bark of Combretum molle (R. Br. ex G. Don.) Engl & Diels (Combretaceae) showed significant inhibitory action against this strain. The acetone fraction of the stem bark of C. molle caused complete inhibition at concentrations higher than 1 mg/mL. Phytochemical analysis of the bioactive fraction led to the isolation of a major tannin and two oleanane-type pentacyclic triterpene glycosides. The tannin was identified as the ellagitannin, punicalagin, whilst the saponins were characterized as arjunglucoside (also called 4-epi-sericoside) and sericoside. All the pure compounds were further tested against the ATCC strain. Punicalagin was found to inhibit totally growth of the ATCC and also of a patient strain, which was fully sensitive to the standard antituberculosis drugs, at concentrations higher than 600 microg/mL and 1.2 mg/mL, respectively. On the other hand, the saponins failed to show any action on the ATCC strain. It appears that our findings are the first report of tannins exhibiting antimycobacterial activity.
The 74 samples of six HYPERICUM species (H. PERFOROTUM, H. HIRSUTUM, H. MACULATUM, H. TETRAPTERUM, H. MONTANUM, AND H. HUMIFUSUM) were collected around Slovenia and analysed for the content of ten substances (rutin, hyperoside, isoquercetin, quercitrin, quercetin, I3,II8-biapigenin, amentoflavone, pseudohypericin, hypericin, and hyperforin). The flowers were analysed separately from the green parts of the plants (herbs). The highest content of most of the substances was found in the flowers of H. PERFOROTUM. Among the herbal samples (without flowers), H. MONTANUM and H. HIRSUTUM contained significantly higher levels of amentoflavone (average 3-fold and 2.5-fold higher, respectively), than the herbs of H. PERFOROTUM. In the herbal part of H. PERFOROTUM the contents of all constituents strongly correlate with the contents of the same compound in flowers, except for the content of amentoflavone, which is independent in these two parts. Rutin and hyperoside are in positive correlation, and quercitrin is in negative correlation with the altitude of the growing site.
Suspension cultures were established from the shoots of sterile germinated seeds of various provenances of seven Hypericum (H.) species in a half strength modified Murashige and Skoog liquid medium. In most strains of H. perforatum (18 provenances) and all strains of H. maculatum (6 provenances) as well as in the cultures of H. tomentosum, H. bithynicum, H. glandulosum and H. balearicum, hypericin and pseudohypericin could be proven, however, in extremely varying amounts. In general, the pseudohypericin content was significantly higher than that of hypericin. The flavonoid patterns, comprising monomeric quercetin derivatives and dimeric apigenin derivatives, varied among strains over a wide range.
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