Investigation of fractions present in the stem bark of Annickia kummeriae on their P-glycoprotein inhibitory pump activity.

Using MCF-7R cells and rhodamine 6G as the fluorescent probe, a bioassay-targeted purification process was pursued in order to isolate the active P-gp inhibitory fractions from Annickia kummeriae. Of 24 fractions obtained in the first preparative liquid chromatography (p-LC) run, only fraction 1 exhibited activity. Further p-LC fractionation led to the separation of fraction 1 into fractions 1.1-1.8. Fractions 1.4, 1.5 and 1.6 proved to be active by inducing a significant accumulation of rhodamine 6G by 3.3-, 4.5- and 4.9-fold at 10 microg/mL, and by 5.3-, 6.3- and 6.8-fold at 100 microg/mL, respectively. Fraction 1.6 was separated into several fractions by using an analytical liquid chromatography (a-LC) system. Fractions 1.6.18, 1.6.19 and 1.6.20 were active and they induced an accumulation of rhodamine 6G by 3.0-, 1.8- and 3.5-fold at 1x microg/mL and by 4.8-, 6.7- and 6.8-fold at 10x microg/mL, respectively. Afterwards, 28.3 mg of fraction 1.6 was processed by a-LC, and fractions 1.6.18, 1.6.19 and 1.6.20 were collected separately and dried. The amounts of materials recovered were 6.2, 7.4 and <1 mg, corresponding to 21.9%, 26.1% and <3.5% of fraction 1.6, respectively. From the total amount injected and the relative masses represented by these fractions, it can be calculated that the 1x microg/mL level corresponded to ca. 35, 42 and <5 microg/mL, respectively. Fluorescence microscopy revealed that incubation of the cells with rhodamine 6G alone did not show any fluorescence, whereas cells which were incubated in medium containing rhodamine 6G together with fraction 1.4, 1.6 or reserpine, clearly indicated accumulation of the dye intracellularly. This is an indication that the active compounds effected high intracellular fluorescence by inducing accumulation of the dye in the cells through inhibition of the P-gp pump.

Screening of Tanzanian plant extracts for their potential inhibitory effect on P-glycoprotein mediated efflux.

For years, many efforts have been made to discover new drugs using plants as natural screening libraries. In this study, extracts of 43 Tanzanian medicinal plants were screened for their potential inhibitory effect on P-gp, using the secretory transport of Cyclosporin A (CsA) in the Caco-2 system as a measure of the functionality of P-gp efflux. Two out of these 43 plant extracts (extracts of Annickia kummeriae and Acacia nilotica) appeared to have a modulatory effect on P-gp related efflux carriers. In presence of the extract of Annickia kummeriae, a concentration dependent decrease on the polarity in transport of CsA was observed; the inhibitory effect of this extract on P-gp was comparable to that of valspodar, a known P-gp inhibiting agent. The exact nature of the active components of these botanicals remains to be identified.

Cytotoxicity of some medicinal plant extracts used in Tanzanian traditional medicine.

Using the ethnomedical data approach, some Tanzanian plants that are used in Tanzanian traditional medicine for cancer or non-cancer diseases were collected and evaluated for cytotoxic activity. The antiproliferative effect of the methanolic extracts (10 and 100 microg/ml) of 47 plants was evaluated in vitro on three human cell lines (HeLa, cervical carcinoma; HT29, colon adenocarcinoma; and A431, skin carcinoma). From the nine plants that are used to treat cancer, two plants (22%) exhibited pronounced cytotoxic effect (<25% cell proliferation) at least in one of the tested cell lines. For the 38 plants that are used to treat non-cancer diseases, 14 plants (37%) exhibited pronounced cytotoxic effect (<25% cell proliferation). Cell type cytotoxic specificity was observed in some extracts. Overall, the A431 cells were much more sensitive to most of the extracts than the other cell lines. For the plants that are used as anticancer herbal drugs, our results indicate that there is no correlation between the reported use of these plants and their cytotoxic activity obtained in this study. However, plants that have shown pronounced cytotoxic activity will be evaluated further for the possible isolation of active antitumor compounds.

Brine shrimp bioassay for biological activity of medicinal plants used in traditional medicines in Tanzania.

A method utilizing Brine Shrimp (Artemia salina Leach) has been used to screen medicinal plants for biological activity. A number of twenty eight medicinal plants were collected from eastern part of Tanzania and their ethnobotanical uses obtained from traditional healers. Biological activity using the Brine Shrimp bioassay was recorded as a lethal concentration (LC 50) that kills 50% of the larvae within 24 hours of contact with the methanol plant extract. Of the 28 plant extracts tested eight gave an LC 50 of activity of less than 20 mu g/ml when compared with controls treated with 10% dimethylsulphoxide (DMS0) in water as solvent. Uvaria acuminata (Annonaceae) root extract was found to be the most active. The Brine Shrimp bioassay was found to be reliable, inexpensive and a convenient method for assessment of biologically active medicinal plants.