Screening for the P-glycoprotein inhibitory pump activity of plant extracts that are used in Tanzanian traditional medicine

An in vitro screening experiment of 45 methanolic plant extracts was carried out to investigate the inhibition of P-glycoprotein (P-gp) in MCF-7R cells. The investigation was carried out using standard functional assay with rhodamine 6G as the fluorescent probe and reserpine, a known inhibitor of P-glycoprotein pump, was used as a reference drug. The results revealed that out of the 45 plant extracts tested, 3 extracts i.e. Bauhinia thoningii, Clerodendrum myricoides and Rhus natalensis exhibited pronounced activity at the concentration of 100 µg/ml. In comparison to the negative control, B. thoningii, C. myricoides and R. natalensis extracts inhibited the pump by a factor of about 2.5, 4 and 4.3, respectively. The remaining 42 extracts did not show any activity. The reference drug reserpine (20 μM) inhibited the pump by a factor of about 11. These preliminary results indicate that the inhibition of P-gp in MCF-7R cells is through a concerted action of compounds present in the extracts and that if isolated might be effective P-gp pump inhibitors in the treatment of cancer. Keywords: plant extract, P-glycoprotein inhibition; rhodamine 6G; MCF-7R cells East and Central African Journal of Pharmaceutical Sciences Vol. 7 2004: 16-2

In vitro antimicrobial activity of flowering and non-flowering ocimum graveolens methanol extracts

Objective: To screen for in vitro antimicrobial activity of methanolic extracts of flowering and non-flowering parts of Ocimum graveolens. Methods: The methanolic extracts of flowering and non-flowering parts of the plant were dissolved in 5% dimethylsulfoxide and serially diluted to concentrations of 0.03-64.0mg/ml. The microdilution with modified [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]–(MTT) method was used for evaluation of antibacterial activity on four strains of reference microbes namely Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Staphylococcus aureus. A 30:1 ratio of culture medium/broth and sensitized microbial suspension with were added to each well. The microplates were aerobically incubated overnight at 37ºC. Five microlitres of MTT was added to each well and incubated for 4 hours prior to spectrophotometric determination of enzymatically converted MTT’s by-products (formazan, a purple/blue precipitate) at 550nm. Inhibition percentage of the extracts and antibiotics was determined by comparison with negative controls (untreated wells). Results: The antimicrobial effect of the extracts of non-flowering parts of O. graveolens exhibited a negative correlation with the extracts’ concentrations (r = -0.915, p = 0.01). The lowest and highest percentage inhibition for non-flowering methanolic was -62.3% and 38.2% on C. albicans and Pseudomonas spp respectively, at 64mg/ml which is the highest assayed extract’s concentration. The methanolic extract of flowering plant showed a positive correlation between extract’s concentrations and percentage inhibition (r =0.313, p= 0.005). The flowering plant extract exerted the highest mean inhibition of 98.06±2.17% (E. coli) and the least 91.04±7.13% (P. aeruginosa) at concentrations of 0.5-8.0mg/ml. The mean inhibition rates of the flowering extracts were comparable to that of control antibiotics: 71.70-100% and 73.9-100% respectively (p<0.05). The enzymatically formed formazan was detectable up to concentrations of 8.0mg/ml for flowering and more than 64mg/ml for non-flowering extracts, and up to 0.25 mg/ml for antibiotics. Conclusion: Methanolic extract of the flowering O. graveolens exhibited pronounced antimicrobial activity when compared with the positive controls and unlike the non-flowering extracts. Results obtained from the flowering O. graveolens plant can justify its traditional use for treatment of common disease conditions. However, further studies should be conducted to buttress these findings and isolation of active antimicrobial components.Key words: Flowering and non-flowering parts of Ocimum graveolen, antimicrobial activit

Anticancer Activity of Extracts from some Endemic Tanzanian Plants

Plants have shown to be good sources of a variety of drugs for human ailments including cancer. Tanzania is rich in plant species most of which have not been investigated for any biological activity. In the continuing effort to screen Tanzanian plants for anticancer activity, plants were collected from Lindi region and extracts tested for the activity using two cell lines namely RT112 (Human bladder transitional cell carcinoma) and HeLa (Human cervical carcinoma). Of the 52 extracts from 26 plants of different families tested, 5 demonstrated potential activity on the cells. Extract X13 had an exceptionally high activity on both cell lines while extract X29 was highly active on HeLa cells. Fractionation and isolation of constituents from the extracts that have shown anticancer activity in these cell lines is recommended. Keywords: Medicinal plants, extracts, anticancer activity, screeningEast and Central African Journal of Pharmaceutical Sciences Vol. 10 (3) 2007: pp. 63-6