In vivo antimalarial activity of extracts of Tanzanian medicinal plants used for the treatment of malaria.

Plants used in traditional medicine have been the source of a number of currently used antimalarial medicines and continue to be a promising resource for the discovery of new classes of antimalarial compounds. The aim of this study was to evaluate in vivo antimalarial activity of four plants; Erythrina schliebenii Harms, Holarrhena pubescens Buch-Ham, Phyllanthus nummulariifolius Poir, and Caesalpinia bonducella (L.) Flem used for treatment of malaria in Tanzania. In vivo antimalarial activity was assessed using the 4-day suppressive antimalarial assay. Mice were infected by injection via tail vein with 2 × 10(7) erythrocytes infected with Plasmodium berghei ANKA. Extracts were administered orally, once daily, for a total of four daily doses from the day of infection. Chloroquine (10 mg/kg/day) and solvent (5 mL/kg/day) were used as positive and negative controls, respectively. The extracts of C. bonducella, E. schliebenii, H. pubescens, and P. nummulariifolius exhibited dose-dependent suppression of parasite growth in vivo in mice, with the highest suppression being by C. bonducella extract. While each of the plant extracts has potential to yield useful antimalarial compounds, the dichloromethane root extract of C. bonducella seems to be the most promising for isolation of active antimalarial compound(s). In vivo antimalarial activity presented in this study supports traditional uses of C. bonducella roots, E. schliebenii stem barks, H. pubescens roots, and P. nummulariifolius for treatment of malaria.

Cytotoxic and antimicrobial activities of substituted phenanthrenes from the roots of Combretum adenogonium Steud Ex A. Rich (Combretaceae).

AIM: The aim of this study was to isolate the bioactive compounds from the roots of Combretum adenogonium and assess for its antibacterial and cytotoxic properties. MATERIALS AND METHODS: The extract was obtained using 20% aqueous ethanol and further subjected to fractionation with 1:1 n-butanol/water. Chromatographic analyses of the n-butanol fraction led to the isolation of compounds (1-3). The compounds (1-3) were assayed for antibacterial activities using two-fold microdilution methods and cytotoxicity using brine shrimps lethality assay. RESULTS: Following spectroscopic analyses the compounds were established as 2,3,8-trihydroxy-4,6-dimethoxyphenanthrene (1a) and 2,3,8-trihydroxy-4,6-dimethoxy-9,10-dihydrophenanthrene (1ß). Compound 2 was derived from 2,3,8-trihydroxy-4,6-dimethoxyphenanthrene condensation with methyl acetate while Compound 3 was derived from 2,3,8-trihydroxy-4,6-dimethoxy-9,10-dihydrophenanthrene condensation with methyl propionate. These compounds (1-3) were active against Pseudomonas aeruginosa with minimal inhibitory concentration-value of 0.16 mg/ml. The compounds (1-3) also exhibited significant toxicity with LC50 (95% confidence interval [CI]) of 12.11 (7.32-20.05) µg/ml compared to standard anticancer drug, cyclophosphamide which had LC50 (95% CI) value of 16.37 (12.01-22.31) µg/ml. CONCLUSION: These compounds add for a novel structure that can be synthesized, further screened for in vitro and in vivo models and clinical trials in order to evaluate its potential for further development as new anticancer agent.

Antimicrobial activity, acute toxicity and cytoprotective effect of Crassocephalum vitellinum (Benth.) S. Moore extract in a rat ethanol-HCl gastric ulcer model.

BACKGROUND: A decoction of Crassocephallum vitellinum (Benth.) S. Moore (Asteraceae) is used in Kagera Region to treat peptic ulcers. This study seeks to evaluate an aqueous ethanol extract of aerial parts of the plant for safety and efficacy. METHODS: An 80% ethanolic extract of C. vitellinum at doses of 100, 200, 400 and 800 mg/kg body wt was evaluated for ability to protect Sprague Dawley rats from acidified ethanol gastric ulceration in comparison with 40 mg/kg body wt pantoprazole. The extract and its dichloromethane, ethyl acetate, and aqueous fractions were also evaluated for acute toxicity in mice, brine shrimp toxicity, and antibacterial activity against four Gram negative bacteria; Escherichia coli (ATCC 25922), Salmonella typhi (NCTC 8385), Vibrio cholera (clinical isolate), and Streptococcus faecalis (clinical isolate). The groups of phytochemicals present in the extract were also determined. RESULTS: The ethanolic extract of C. vitellinum dose-dependently protected rat gastric mucosa against ethanol/HCl insult to a maximum of 88.3% at 800 mg/kg body wt, affording the same level of protection as by 40 mg/kg body wt pantoprazole. The extract also exhibited weak antibacterial activity against S. typhi and E. coli, while its ethyl acetate, dichloromethane and aqueous fractions showed weak activity against K. pneumonia, S.typhi, E. coli and V. cholera. The extract was non-toxic to mice up to 5000 mg/kg body wt, and the total extract (LC50 = 37.49 µg/ml) and the aqueous (LC50 = 87.92 µg/ml), ethyl acetate (LC50 = 119.45 µg/ml) and dichloromethane fractions (88.79 µg/ml) showed low toxicity against brine shrimps. Phytochemical screening showed that the extract contains tannins, saponins, flavonoids, and terpenoids. CONCLUSION: The results support the claims by traditional healers that a decoction of C.vitellinum has antiulcer activity. The mechanism of cytoprotection is yet to be determined but the phenolic compounds present in the extract may contribute to its protective actions. However, the dose conferring gastro-protection in the rat is too big to be translated to clinical application; thus bioassay guided fractionation to identify active compound/s or fractions is needed, and use of more peptic ulcer models to determine the mechanism for the protective action.

Larvicidal, antimicrobial and brine shrimp activities of extracts from Cissampelos mucronata and Tephrosia villosa from coast region, Tanzania.

BACKGROUND: The leaves and roots of Cissampelos mucronata A. Rich (Menispermaceae) are widely used in the tropics and subtropics to manage various ailments such as gastro-intestinal complaints, menstrual problems, venereal diseases and malaria. In the Coast region, Tanzania, roots are used to treat wounds due to extraction of jigger. Leaves of Tephrosia villosa (L) Pers (Leguminosae) are reported to be used in the treatment of diabetes mellitus in India. In this study, extracts from the roots and aerial parts of C. mucronata and extracts from leaves, fruits, twigs and roots of T. villosa were evaluated for larvicidal activity, brine shrimps toxicity and antimicrobial activity. METHODS: Powdered materials from C. mucronata were extracted sequentially by dichloromethane followed by ethanol while materials from T.villosa were extracted by ethanol only. The extracts obtained were evaluated for larvicidal activity using Culex quinquefasciatus Say larvae, cytotoxicity using brine shrimp larvae and antimicrobial activity using bacteria and fungi. RESULTS: Extracts from aerial parts of C. Mucronata exhibited antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Vibrio cholera, Bacillus anthracis, Streptococcus faecalis and antifungal activity against Candida albicans and Cryptococcus neoformans. They exhibited very low toxicity to brine shrimps and had no larvicidal activity. The root extracts exhibited good larvicidal activity but weak antimicrobial activity. The root dichloromethane extracts from C. mucronata was found to be more toxic with an LC50 value of 59.608 µg/mL while ethanolic extracts from root were not toxic with LC50>100 µg/mL). Ethanol extracts from fruits and roots of T. villosa were found to be very toxic with LC50 values of 9.690 µg/mL and 4.511 µg/mL, respectively, while, ethanol extracts from leaves and twigs of T. villosa were found to be non toxic (LC50>100 µg/mL). CONCLUSION: These results support the use of C. mucronata in traditional medicine for treatment of wounds. Extracts of C. mucronata have potential to yield active antimicrobial and larvicidal compounds. The high brine shrimp toxicity of T. villosa corroborates with literature reports that the plant is toxic to both livestock and fish. The results further suggest that T. villosa extracts have potential to yield larvicidal and possibly cytotoxic compounds. Further studies to investigate the bioactive compounds responsible for the observed biological effects are suggested.

Antibacterial and cytotoxic activities of Terminalia stenostachya and Terminalia spinosa.

Plants that belong to the Combretaceae family have long history of use in the traditional medicine systems of Africa and Asia for treatment of diseases and conditions associated with HIV/AIDS-opportunistic infections. The objective of this study was to investigate the biological activities of extracts of Terminalia stenostachya Engl. & Diels and Terminalia spinosa Engl. (Combretaceae), to verify the rationale for their use by traditional health practitioners in the treatment of HIV/AIDS patients in Tanzania. Extracts of the leaves, stem barks and roots of T. stenostachya and extracts of stem barks and roots of T. spinosa have all shown strong activity against a number of standard microbial strains including Mycobacterium madagascariense and Mycobacterium indicus pranii, Streptococcus faecalis, Staphylococcus aureus, Vibrio cholera, Bacillus anthracis, Bacillus subtilis, Klebsiella pneumoniae, Salmonella typhi, Pseuodomonas aeruginosa and Escherichia coli. All extracts from the two plant species showed strong antimycobacterial activity against test organisms. The stem and root bark extracts were more active than leaves against both gram positive and negative bacteria. With the exception of two extracts from stem barks of T. spinosa, all other extracts from T. stenostachya and T. spinosa that were tested exhibited less activity against brine shrimp larvae with LC50 values ≥ 100 µg/mL compared to cyclophosphamide, a standard anticancer drug. These results provide an indication that these plants may possess therapeutically potent antimicrobial compounds worth further development.