Antiplasmodial and Antileishmanial Activities of a New Limonoid and Other Constituents from the Stem Bark of Khaya senegalensis.

Plasmodium falciparum and Leishmania sp. resistance to antiparasitic drugs has become a major concern in malaria and leishmaniasis control. These diseases are public health problems with significant socioeconomic impacts, and mostly affect disadvantaged populations living in remote tropical areas. This challenge emphasizes the need to search for new chemical scaffolds that preferably possess novel modes of action to contribute to antimalarial and antileishmanial research programs. This study aimed to investigate the antimalarial and antileishmanial properties of a methanol extract (KS-MeOH) of the stem bark of the Cameroonian medicinal plant Khaya senegalensis and its isolated compounds. The purification of KS-MeOH led to the isolation of a new ordered limonoid derivative, 21ß-hydroxybourjotinolone A (1a), together with 15 known compounds (1bc-14) using a repeated column chromatography. Compound 1a was obtained in an epimeric mixture of 21α-melianodiol (1b) and 21ß-melianodiol (1c). Structural characterization of the isolated compounds was achieved with HRMS, and 1D- and 2D-NMR analyses. The extracts and compounds were screened using pre-established in vitro methods against synchronized ring stage cultures of the multidrug-resistant Dd2 and chloroquine-sensitive/sulfadoxine-resistant 3D7 strains of Plasmodium falciparum and the promastigote form of Leishmania donovani (1S(MHOM/SD/62/1S). In addition, the samples were tested for cytotoxicity against RAW 264.7 macrophages. Positive controls consisted of artemisinin and chloroquine for P. falciparum, amphotericin B for L. donovani, and podophyllotoxin for cytotoxicity against RAW 264.7 cells. The extract and fractions exhibited moderate to potent antileishmanial activity with 50% inhibitory concentrations (IC50) ranging from 5.99 ± 0.77 to 2.68 ± 0.42 µg/mL, while compounds displayed IC50 values ranging from 81.73 ± 0.12 to 6.43 ± 0.06 µg/mL. They were weakly active against the chloroquine-sensitive/sulfadoxine-resistant Pf3D7 strain but highly potent toward the multidrug-resistant PfDd2 (extracts, IC50 2.50 ± 0.12 to 4.78 ± 0.36 µg/mL; compounds IC50 2.93 ± 0.02 to 50.97 ± 0.37 µg/mL) with selectivity indices greater than 10 (SIDd2 > 10) for the extract and fractions and most of the derived compounds. Of note, the limonoid mixture [21ß-hydroxylbourjotinolone A (1a) + 21α-melianodiol (1b) + 21ß-melianodiol (1c)] exhibited moderate activity against P. falciparum and L. donovani. This novel antiplasmodial and antileishmanial chemical scaffold qualifies as a promising starting point for further medicinal chemistry-driven development of a dually active agent against two major infectious diseases affecting humans in Africa.

Implementation and continued validation of the malaria Plasmodium falciparum lactate dehydrogenase-based colorimetric assay for use in antiplasmodial drug screening.

Antimalarial drug discovery has been facilitated by the development of various in vitro drug susceptibility testing methods suitable for medium-throughput or high-throughput campaigns. Among many, the Plasmodium falciparum lactate dehydrogenase (PfLDH) assay has acceptable demand on equipment, labour, technical skills and affordability and offers a good opportunity for scientists in low- and middle-income countries to participate in the global effort of discovering future antimalarial drugs. Hence, to enable our search for novel antimalarial drugs, we implemented and examined assay conditions and validated the PfLDH-based method in our laboratory using a reference set of standard antimalarial drugs with known activity against Plasmodium falciparum strains. The PfLDH assay revealed acceptable linearity profiles of R2 = 0.97 and 0.92 for Pf3D7 and PfDd2, respectively, achieved at 2% parasitaemia and 1% haematocrit. The detection and quantitation limits (DL and QL) of the PfLDH-based assay were 0.09% and 0.4% parasitemia, respectively. The assay showed an acceptable average Z-factor between 0.76 and 0.79 and was considerably robust. The average interassay reproducibility via percent coefficient of variation (%CV) was 5.47 between independent experiments. Overall, the PfLDH-based method produced a reliable and reproducible drug screening profile for in vitro assays in our setting. There were no significant interassay variability or hazards of other screening assays.

Scopolamine-Induced Memory Impairment in Mice: Neuroprotective Effects of Carissa edulis (Forssk.) Valh (Apocynaceae) Aqueous Extract.

Alzheimer's disease is first characterised by memory loss related to the central cholinergic system alteration. Available drugs provide symptomatic treatment with known side effects. The present study is aimed to evaluate the properties of Carissa edulis aqueous extract on a Scopolamine mouse model as an attempt to search for new compounds against Alzheimer's disease-related memory impairment. Memory impairment was induced by administration of 1 mg/kg (i.p.) of Scopolamine for 7 days, and mice were treated with Carissa edulis aqueous extract. Behavioural studies were performed using T-maze and novel object recognition task for assessing learning and memory and open field test for locomotion. Brain acetylcholinesterase enzyme (AChE) activity was measured to evaluate the central cholinergic system. The level of MDA, glutathione, and catalase activity were measured to evaluate the oxidative stress level. Administration of Scopolamine shows a decrease in learning and memory enhancement during behavioural studies. A significant decrease in the time spent in the preferred arm of T-maze, in the time spent in the exploration of the novel object, and in the discrimination index of the familiar object was also observed. The significant impairment of the central cholinergic system was characterised in mice by an increase of AChE activity to 2.55 ± 0.10 mol/min/g with an increase in oxidative stress. Treatment with the different doses of Carissa edulis (62.8, 157, 314, and 628 mg/kg orally administrated) significantly increased the memory of mice in T-maze and novel object recognition tests and also ameliorated locomotion of mice in the open field. Carissa edulis aqueous extract treatment also decreases the AChE activity and brain oxidative stress. It is concluded that administration of Carissa edulis aqueous extract enhances memory of mice by reducing AChE activity and demonstrating antioxidant properties. This could be developed into a novel therapy against memory impairment related to Alzheimer's disease.

Composition and cytotoxic activity of essential oils from Xylopia aethiopica (Dunal) A. Rich, Xylopia parviflora (A. Rich) Benth.) and Monodora myristica (Gaertn) growing in Chad and Cameroon.

BACKGROUND: Cancer has become a global public health problem and the search for new control measures is urgent. Investigation of plant products such as essential oils from Monodora myristica, Xylopia aethiopica and Xylopia parviflora might lead to new anticancer therapy. In this study, we have investigated the antineoplastic activity of essential oils from fruits of these plants growing in Chad and Cameroon. METHODS: The essential oils obtained by hydrodistillation of fruits of Monodora myristica, Xylopia aethiopica and Xylopia parviflora collected in Chad and Cameroon were analyzed by GC-FID and GC-MS and investigated for their antiproliferative activity against the breast cancer cell line (MCF7). RESULTS: Overall, monoterpenes were mostly found in the six essential oils. Oils from X. aethiopica and X. parviflora from Chad and Cameroon mainly contain ß-pinene at 24.6%, 28.2%, 35.7% and 32.9% respectively. Monodora myristica oils from both origins contain mainly α-phellandrene at 52.7% and 67.1% respectively. The plant origin did not significantly influence the chemical composition of oils. The six essential oils exerted cytotoxic activity against cancer (MCF-7) and normal cell lines (ARPE-19), with more pronounced effect on neoplastic cells in the majority of cases. The highest selectivity was obtained with the essential oils of X. parviflora from Chad and Cameroon (5.87 and 5.54) which were more cytotoxic against MCF-7 than against normal cell line (ARPE-19) with IC50 values of 0.155 µL/mL and 0.166 µL/mL respectively. CONCLUSIONS: Essential oils from fruits of Monodora myristica, Xylopia aethiopica and Xylopia parviflora have shown acceptable antineoplastic potency, and might be investigated further in this regard.

Ethnopharmacological survey of Annonaceae medicinal plants used to treat malaria in four areas of Cameroon.

ETHNOPHARMACOLOGICAL RELEVANCE: Malaria endemic countries have vital resources that are medicinal plants on which their traditional medicines depend. In some Cameroonian settings, in addition to the commonly used potions from plants like Alstonia boonei, Zanthoxylum macrophylla and Mangifera indica, other herbal species are being increasingly used to treat malaria. So, specialized traditional healers have developed alternative reasonably priced therapies, relying on the signs and/or symptoms of malaria. Within this framework, Annonaceae plants were found to be increasingly utilized and therefore, highlighting the need to document this traditional knowledge for better malaria control. MATERIALS AND METHODS: Interview approach was used to document indigenous knowledge, usage customs and practices of Annonaceae species in the treatment of malaria in four Cameroonian areas (Yaoundé and its surroundings, Ngoyang, Kon-Yambetta and Mbalmayo). RESULTS: A total of 19/30 users of plants accepted to share their experiences during a semi-structured survey. Twelve of the respondents were men and seven were women. Thirty recipes based on twenty-one plants were recorded. CONCLUSION: Annickia chlorantha was the only plant commonly found in the four study sites. Seven species of Annonaceae were found to be used to treat malaria, while 14 were used to treat symptoms that might be related to malaria.