In vitro effects of Warburgia ugandensis, Psiadia punctulata and Chasmanthera dependens on Leishmania major promastigotes.

Plant extracts from Warburgia ugandensis Sprague (Family: Canellaceae), Psiadia punctulata Vatke (Family: Compositae) and Chasmanthera dependens Hoschst (Family: Menispermaceae) were tested for activity on Leishmania major promastigotes (Strain IDU/KE/83 = NLB-144) and infected macrophages in vitro. Plants were collected from Baringo district, dried, extracted, weighed and tested for antileishmanial activity. Serial dilutions of the crude extracts were assayed for their activity against Leishmania major in cell free cultures and in infected macrophages in vitro. Inhibitory concentrations and levels of cytotoxicity were determined. Warburgia ugandensis, Psiadia punctulata and Chasmanthera dependens had an IC(50) of 1.114 mg/ml, 2.216 mg/ml and 4.648 mg/ml, respectively. The cytotoxicity of the drugs on BALB/c peritoneal macrophage cells was insignificant as compared to the highly toxic drug of choice Pentostam(®). The supernatants from control and Leishmania infected macrophages were analyzed for their nitrite contents by Griess reaction and nitrite absorbance measured at 540 nm. Warburgia ugandensis (stem bark water extract), Chasmanthera dependens (stem bark water extract) and Psiadia punctulata (stem bark methanol extract) produced 112.3%, 94% and 88.5% more nitric oxide than the untreated infected macrophages respectively. Plant crude extracts had significant (p<0.05) anti-leishmanial and immunomodulative effects but insignificant cytotoxic effects at 1mg/ml concentration. All experiments were performed in triplicate. Statistical analysis of the differences between mean values obtained from the experimental group compared to the controls was done by students't test. ANOVA was used to determine the differences between the various treatment groups. The analysis program Probit was used to determine IC(50)s.

Tigliane diterpenoids from the stem bark of Neoboutonia macrocalyx.

Neoboutonia macrocalyx is a plant used by traditional healers among the Meru community in Kenya. Chromatographic fractionation of the petroleum ether and dichloromethane extracts of this plant yielded one known (1) and three new tigliane-type diterpenoids (2-4). The chemical structures of the isolated compounds were established through spectroscopic data interpretation.

Anti-viral activity of the extracts of a Kenyan medicinal plant Carissa edulis against herpes simplex virus.

Herpes simplex virus (HSV) infection is a major opportunistic infection in immunosuppressed persons. It is therefore a serious disease in high HIV/AIDS prevalence areas as in sub-Saharan Africa where infections due to HSV have risen significantly. The development of resistant strains of HSV to the available drugs for infection management, as is evident in the first drug of choice acyclovir, has further compounded this situation. There is therefore an urgent need to identify and develop new alternative agents for management of HSV infections, more so, for those due to resistant strains. We report here on an aqueous total extract preparation from the roots of Carissa edulis (Forssk.) Vahl (Apocynaceae), a medicinal plant locally growing in Kenya that has exhibited remarkable anti-HSV activity in vitro and in vivo for both wild type and resistant strains of HSV. The extract significantly inhibited formation of plaques in Vero E6 cells infected with 100PFU of wild type strains of HSV (7401H HSV-1 and Ito-1262 HSV-2) or resistant strains of HSV (TK(-) 7401H HSV-1 and AP(r) 7401H HSV-1) by 100% at 50 microg/ml in vitro with minimal cell cytotoxicity (CC(50)=480 microg/ml). When the extract was examined for in vivo efficacy in a murine model using Balb/C mice cutaneously infected with wild type or resistant strains of HSV, the extract at an oral dose of 250 mg/kg significantly delayed the onset of HSV infections by over 50%. It also increased the mean survival time of treated infected mice by between 28 and 35% relative to the infected untreated mice (p<0.05 versus control by Student's t-test). The mortality rate for mice treated with extract was also significantly reduced by between 70 and 90% as compared with the infected untreated mice that exhibited 100% mortality. No acute toxicity was observed in mice at the oral therapeutic dose of 250 mg/kg. These results suggest that this herbal extract has potent anti-viral agents against herpes simplex viruses that can be exploited for development of an alternative remedy for HSV infections.

Evaluation of the HIV-1 reverse transcriptase inhibitory properties of extracts from some medicinal plants in Kenya.

Extracts from twenty two medicinal plants popularly used in preparing traditional remedies in Kenya were screened for activity against the HIV-1 reverse transcriptase. The screening procedure involved the use of tritium labeled thymidine triphosphate as the enzyme substrate and polyadenylic acid.oligodeoxythymidylic acid [poly(rA).p(dT)12-18] as the template primer dimer. Foscarnet was used as a positive control in these experiments. At a concentration of 100 microg/ml, extracts from eight of these plants showed at least 50 per cent reverse transcriptase inhibition. This activity was arbitrarily considered as significant. This indicates that there is the probability that some antiretroviral compounds could be identified and isolated from materials from these plants.