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1.  Isolation and identification of an antiparasitic triterpenoid estersaponin from the stem bark of Pittosporum mannii (Pittosporaceae) 
Objective
To screen for antiparasitic properties of Pittosporum mannii Hook (Pittosporaceae) through in vitro bioassay tests and to identify the bioactive compound(s).
Methods
The stem bark of Pittosporum mannii was harvested in Bali Nyonga in January 2007. The CH2Cl2 and MeOH extracts were tested in vitro for antiparasitic activity. NF54 (an airport strain of unknown origin and sensitive to all known drugs) and K1 (a clone originating from Thailand and resistant to chloroquine/pyrimethamine) strains were used for the antiplasmodial screening while Leishmania donovani MHOM-ET-67/L82 was used for antileishmanial testing. 1H and 13C NMR spectra were recorded on a Bruker AMX-500 spectrometer using CDCl3 as solvent. EIMS were recorded on a double-focusing mass spectrometer (Varian MAT 311A) while HREIMS were recorded on a JEOL HX 110 mass spectrometer.
Results
The MeOH extract was active on both the chloroquine-resistant (K1) strain (IC50=4.3 µg/mL) and on the macrophages of Leishmania donovani (IC50=8.6 µg/mL). The CH2Cl2 extract was considered inactive on both parasites (IC50>5.0 µg/mL and 21.7 µg/mL respectively). Compound 1, a constituent that precipitated from the MeOH extract, showed pronounced activity on both Plasmodium falciparum and Leishmania donovani parasites (IC50=1.02 and 1.80 µg/mL respectively) with artemisinin and miltefosine included as reference drugs. Its structure was identified as 1-O-[apha-L-(Rhamnopyranosyl]-23-acetoxyimberbic acid 29-methyl ester, a pentacyclic triterpenoid estersaponin.
Conclusions
The present study constitutes the first report on the antiparasitic activity of this plant and provides some support for the traditional use of the plant in the treatment of malaria. The plant has therefore been identified as a potential source for the discovery of antiparasitic lead compounds.
doi:10.1016/S2222-1808(13)60089-4
PMCID: PMC4027329
Phytochemical; Pittosporum; Antiplasmodial; Triterpenoid; Saponins
2.  Bioassay-guided discovery of antibacterial agents: in vitro screening of Peperomia vulcanica, Peperomia fernandopoioana and Scleria striatinux 
Background
The global burden of bacterial infections is high and has been further aggravated by increasing resistance to antibiotics. In the search for novel antibacterials, three medicinal plants: Peperomia vulcanica, Peperomia fernandopoioana (Piperaceae) and Scleria striatinux (Cyperaceae), were investigated for antibacterial activity and toxicity.
Methods
Crude extracts of these plants were tested by the disc diffusion method against six bacterial test organisms followed by bio-assay guided fractionation, isolation and testing of pure compounds. The minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations were measured by the microdilution method. The acute toxicity of the active extracts and cytotoxicity of the active compound were performed in mice and mammalian cells, respectively.
Results
The diameter of the zones of inhibition (DZI) of the extracts ranged from 7–13 mm on Escherichia coli and Staphylococcus aureus of which the methylene chloride:methanol [1:1] extract of Scleria striatinux recorded the highest activity (DZI = 13 mm). Twenty-nine pure compounds were screened and one, Okundoperoxide, isolated from S. striatinux, recorded a DZI ranging from 10–19 mm on S. aureus. The MICs and MBCs indicated that the Peperomias had broad-spectrum bacteriostatic activity. Toxicity tests showed that Okundoperoxide may have a low risk of toxicity with an LC50 of 46.88 μg/mL.
Conclusions
The antibacterial activity of these plants supports their use in traditional medicine. The pure compound, Okundoperoxide, may yield new antibacterial lead compounds following medicinal chemistry exploration.
doi:10.1186/1476-0711-11-10
PMCID: PMC3403929  PMID: 22549052
Resistance; Medicinal plants; Antibacterial compound; Toxicity
3.  Selective activity of extracts of Margaritaria discoidea and Homalium africanum on Onchocerca ochengi 
Background
The current treatment of onchocerciasis relies on the use of ivermectin which is only microfilaricidal and for which resistant parasite strains of veterinary importance are increasingly being detected. In the search for novel filaricides and alternative medicines, we investigated the selective activity of crude extracts of Margaritaria discoidea and Homalium africanum on Onchocerca ochengi, a model parasite for O. volvulus. These plants are used to treat the disease in North West Cameroon.
Methods
Sixteen crude extracts were prepared from various parts of M. discoidea and H. africanum using different organic solvents. The filaricidal activities were determined in vitro. Cytotoxicity of the active extracts was assessed on monkey kidney epithelial cells in vitro and the selectivity indices (SI) of the extracts determined. Acute toxicity of the promising extracts was investigated in mice.
Results
Four out of the 16 extracts showed microfilaricidal activity based on motility reduction, whereas, none showed macrofilaricidal activity based on the MTT/formazan assay. The methylene chloride extract of H. africanum leaves (HLC) recorded the lowest IC50 of 31.25 μg/mL and an IC100 of 62.5 μg/mL. The SI for the active extracts ranged from 0.5 - 2.63. No form of acute toxicity was observed in mice. Phytochemical analysis revealed the presence of anthraquinones, sterols and terpenoids in the promising extracts.
Conclusions
The non-polar extracts of M. discoidea and H. africanum are potential sources of new microfilaricidal lead compounds, and the results support their use in traditional medicine.
doi:10.1186/1472-6882-10-62
PMCID: PMC2987330  PMID: 21029456

Results 1-3 (3)