Oyindamola O. Abiodun

Antimalarial Ethnobotany: In Vitro. Antiplasmodial Activity of Seven Plants Identified in the Nigerian Middle Belt

Abstract Seven methanol extracts of seven plants from seven plant families were screened for antimalarial properties. The plants were identified and selected from Gboko and Kastina-Ala local government areas in the Tivland ethnobotany in the Middle Belt Zone of Nigeria. Methanol plant extracts were evaluated for in vitro. antimalarial properties using the lactate dehydrogenase technique, with a multiresistant strain of Plasmodium falciparum. K1. Quantification of activity was by estimation of the concentration of extracts that inhibited 50% growth of parasite (IC50) in µg/ml. Of the seven plants screened, Erythrina senegalensis. DC (Leguminosae), Pericopsis elata. Harms (Papilionaceae), and Bridelia micrantha. Benth (Fabaceae) had IC50 values of 99.7, 124.8, and 158.7 µg/ml, respectively. Nauclea latifolia. SM (Rubiaceae) extract exhibited the least activity in the assay with an IC50 value of 478.9 µg/ml.

Comparison of SYBR Green I-, PicoGreen-, and [3H]-hypoxanthine-based assays for in vitro antimalarial screening of plants from Nigerian ethnomedicine

The standard method for in vitro antimalarial drug screening is based on the isotopic assay which is expensive and utilizes radioactive materials with limited availability, safety, and disposal problems in developing countries. The use of non-radioactive DNA stains SYBR Green I (SG) and PICO green® (PG) for antimalarial screening had been reported. However, the use of the two DNA stains for antimalarial screening of medicinal plants has not been compared. Thus, this study compared SG, PG with the [3H]-hypoxanthine (HP) incorporation assays for in vitro antimalarial screening of medicinal plants. The 50% inhibitory concentration (IC50) values obtained using the three methods for antimalarial activity of medicinal plants and standard antimalarial drugs were similar. Data generated from this study suggests that the non-radioactive microflourimetric assay is sufficiently sensitive to reproducibly identify plant extracts with antimalarial activity from those lacking activity. The HP-based assay exhibited the most robust signal-to-noise ratio of 100, compared with signal-to-noise ratios of 7 for SG and 8 for PG. The SG-based assay is less expensive than the PG- and HP-based assays. SG appears to be a cost-effective alternative for antimalarial drug screening and a viable technique that may facilitate antimalarial drug discovery process especially in developing countries.

In vitro antiplasmodial activity and toxicity assessment of some plants from Nigerian ethnomedicine

Context: The emergence and spread of Plasmodium falciparum-resistant parasites to nearly all available antimalarial drugs pose a threat to malaria control and necessitates the need to continue the search for new effective and affordable drugs. Ethnomedicine has been shown to be a potential source of antimalarial compounds or source of template for the synthesis of novel antimalarial molecules. Objective: The antiplasmodial activity and toxicity assessment of 30 plant extracts from eight medicinal plants identified in Nigerian ethnomedicine for the treatment of febrile illnesses were evaluated. Materials and methods: In vitro antimalarial activity was evaluated using Plasmodium falciparum NF54 (sensitive to all antimalarial drugs) and K1 (chloroquine/pyrimethamine resistant) strains in the [3H]-hypoxanthine incorporation assay. Toxicity was determined against mammalian L6 cells using Alamar blue assay. Results: The ethyl acetate extract of leaves of Ocimum gratissimum Linn. (Labiatae) and hexane extract of stem bark of Trema orientalis (L.) Blume (Ulmaceae) showed the highest antiplasmodial activity (IC50 1.8-1.93 µg/mL) against P. falciparum K1 strain but elicited low cytotoxicity (selective index >10). However, hexane, ethyl acetate or methanol extracts of leaves of Terminalia catappa Linn. (Combretaceae), Jatropha curcas Linn. (Euphorbiaceae), Vitex doniana Sweet. (Verbenaceae) and stem bark of Vitex doniana displayed antiplasmodial activity (IC50 2.3-16.9 µg/mL) with good selectivity (21–120) for malaria parasites. Discussion and conclusion: The antiplasmodial activity of Terminalia catappa and Vitex doniana against P. falciparum K1 is being reported for the first time in Nigerian ethnomedicine and these plants could be potential source of antimalarial agents.

In Vitro and In Vivo Antimalarial Activity of Ficus thonningii Blume (Moraceae) and Lophira alata Banks (Ochnaceae), Identified from the Ethnomedicine of the Nigerian Middle Belt

Drug resistance in Plasmodium falciparum requires that new drugs must be developed. Plants are a potential source for drug discovery and development. Two plants that used to treat febrile illnesses in Nigeria were tested for in vitro and in vivo antimalarial activity and cytotoxicity in cancer cell lines. Methanol, hexane, and ethyl acetate leaf extracts of Ficus thonningii and Lophira alata were active in in vitro assays against P. falciparum NF54 (sensitive) and K1 (multiresistant) strains. Hexane extracts of F. thonningii and L. alata were the most effective extracts in in vitro assays with IC50 of 2.7 ± 1.6 μg/mL and 2.5 ± 0.3 μg/mL for NF54 and 10.4 ± 1.6 μg/mL and 2.5 ± 2.1 μg/mL for K1 strain. All extracts were nontoxic in cytotoxicity assays against KB human cell line with IC50 of over 20 μg/mL, demonstrating selectivity against P. falciparum. In vivo analysis shows that hexane extracts of both plants reduced parasitaemia. At the maximum dose tested, L. alata had a 74.4% reduction of parasitaemia while F. thonningii had a reduction of 84.5%, both extracts prolonged animal survival in mice infected with P. berghei NK65 when compared with vehicle treated controls. The antiplasmodial activity observed justifies the use of both plants in treating febrile conditions.

In vitro interaction of artemisinin derivatives or the fully synthetic peroxidic anti-malarial OZ277 with thapsigargin in Plasmodium falciparum strains.

BackgroundSemi-synthetic artemisinin derivatives are powerful peroxidic drugs in artemisinin-based combination therapy (ACT) recommended as first-line treatment of Plasmodium falciparum malaria in disease-endemic countries. Studies by Eckstein-Ludwig and co-workers showed both thapsigargin and artemisinin specifically inhibit the sarcoplasmic reticulum Ca2+−ATPase of Plasmodium falciparum (PfATP6). In the present study the type of interaction between thapsigargin and artemisinin derivatives as well as the ozonide OZ277 (RBx11160 or arterolane) was evaluated in parasite cultures. The latter compound is an adamantane-based peroxide and the first fully synthetic clinical candidate recently registered in India by Ranbaxy Laboratories Ltd. for anti-malarial combination therapy.MethodsDrug interaction studies were performed using a previously described fixed ratio method and anti-malarial activity measured using the [3H] hypoxanthine incorporation assay.ResultsThe sum 50% and 90% fractional inhibitory concentration (∑FIC50, 90) of the interaction of thapsigargin with OZ277, artemether or artesunate, against NF54 and K1 strains of P. falciparum ranged from 0.9 to 1.4.ConclusionThe interaction of thapsigargin with OZ277, artesunate or artemether was additive, data consistent with previous observations indicating that activity of anti-malarial peroxides does not derive from reversible interactions with parasite targets.

Cajachalcone: An Antimalarial Compound from Cajanus cajan Leaf Extract.

Cajanus cajan L, a member of the family Fabaceae, was identified from the Nigerian antimalarial ethnobotany as possessing antimalarial properties. The bioassay-guided fractionation of the crude methanol extract of C. cajan leaves was done in vitro using the multiresistant strain of Plasmodium falciparum (K1) in the parasite lactate dehydrogenase assay. Isolation of compound was achieved by a combination of chromatographic techniques, while the structure of the compound was elucidated by spectroscopy. This led to the identification of a cajachalcone, 2′,6′-dihydroxy-4-methoxy chalcone, as the biologically active constituent from the ethyl acetate fraction. Cajachalcone had an IC50 value of 2.0 μg/mL (7.4 μM) and could be a lead for anti-malarial drug discovery.

Antiinflammatory and immunomodulatory activity of an ethanolic extract from the stem bark of Terminalia catappa L. (Combretaceae): In vitro and in vivo evidences

ETHNOPHARMOCOLOGICAL RELEVANCE Terminalia catappa Linn (Combretaceae) is a medicinal plant with anti-inflammatory, anti-diarrhoeal and antioxidant properties, frequently found in tropical regions. Considering its characteristics, it could be useful for the treatment of inflammatory bowel disease, which is associated with inflammation, oxidative stress and an immune dysfunction. Thus this study evaluates the immunomodulatory properties and the intestinal anti-inflammatory effect of an ethanolic extract of the stem bark of T. catappa (ETCB) both in vitro (in RAW 264.7 macrophages) and in vivo, in the trinitrobenzenesulfonic acid (TNBS) model of rat colitis. MATERIALS AND METHODS The phenolic compounds in ETCB were identified and quantified using HPLC-DAD-qTOF-MS. The immunomodulatory activity ETCB was tested in vitro by determining the macrophage production of IL-1β and nitrites. In vivo studies were performed in the TNBS model of rat colitis. ETCB was given (25, 50 and 100mg/kg/day) orally for two days prior to colitis induction and thereafter for 7 days. Response to treatment was assessed by scoring the gross appearance of the colon, and determining myeloperoxidase activity, gene expression of pro-inflammatory cytokines like TNF-α, IL-23 and IL-6, chemokines, inducible nitric oxide synthase and proteins crucial in the maintenance of the intestinal mucosal barrier integrity like mucins (MUC-2, MUC-3) and villin. RESULTS ETCB was able to inhibit IL-1β and nitrite production in vitro in RAW 264.7 macrophages. Moreover, treatment of TNBS colitic rats with ETCB resulted in a decreased colonic damage score and weight/length ratio. It also reduced the colonic neutrophil infiltration indicated by a lower myeloperoxidase activity and prevented the depletion of colonic glutathione levels in colitic rats. In addition, treatment with ETCB down-regulated the gene expression of pro-inflammatory mediators (TNF-α, IL-23, IL-6 and CINC-1) and iNOS in colitic rats. Moreover, the gene expression of mucosal barrier proteins like MUC-2, MUC-3 and villin were up-regulated in colitic rats treated with ETCB. The dose of ETCB that produced the most significant beneficial effect was 100mg/kg. Regarding the chemical composition of ETCB, 31 phenolic compounds were identified, including ellagic acid, catalagin and gallic acid. CONCLUSION The beneficial effect of ETCB in the TNBS induced colitis in rats could be related to its antioxidant, immunomodulatory and anti-inflammatory activities, which could be attributed to the phenolic compounds identified.

Amodiaquine–Ciprofloxacin: a potential combination therapy against drug resistant malaria

Emergence of malaria parasites resistant to artemisinin necessitates the need for development of new antimalarial therapies. Ciprofloxacin (CFX) a second generation quinolone antibiotic possesses some antimalarial activities. We investigated the in vivo antimalarial activities of CFX in combination with amodiaquine in mice infected with chloroquine-resistant Plasmodium berghei ANKA. Animals were treated orally with 80 or 160 mg kg-1 body weight of CFX alone given twice daily or in combination with amodiaquine (AQ) 10 mg kg-1 body weight. Parasitological activity and survival of the animals were assessed over 21 days. Peak parasitaemia in the untreated control group was 72.51%. Treatment with AQ alone resulted in clearance of parasitaemia by day 4 while treatment with CFX 80 and 160 mg kg-1 alone suppressed parasitaemia by 13.94-54.64% and 35.6-92.7%, respectively. However, the combination of CFX with AQ significantly enhanced response of infection in the animals to treatment (P < 0.05) resulting in complete resolution of parasitaemia throughout follow up period with CFX 160 mg kg-1, delayed recrudescence time with CFX 80 mg kg-1 and significant increase in survival rate of the animals. The results demonstrate beneficial interaction between AQ and CFX which may provide a clinically relevant antimalarial/antibiotic therapeutic option in the management of malaria.

The effect of lopinavir/ritonavir on the antimalarial activity of artemether or artemether/lumefantrine in a mouse model of Plasmodium berghei

Abstract The possibility of drug–drug interactions occurring during the treatment of malaria infection in human immunodeficient virus (HIV) patients receiving antiretroviral drugs is very high and limited data are available. This study reports the effect of lopinavir/ritonavir (LR) an antiretroviral drug on the antimalarial activity of standard dose of artemether/lumefantrine (AL) or artemether (AM) in a mouse model of Plasmodium berghei. The 50% effective dose (ED50) of AM alone (0·80±0·15 and 2·18±0·75 mg/kg) or in combination with LR (0·88±0·40 and 3·53±1·09 mg/kg) on days 4 and 5 post-infection was similar. In addition, treatment with a standard dose of AL alone or in combination with LR resulted in complete suppression of parasite growth. However, co-administration of LR with AL appears to be toxic resulting in lower survival of experimental animals in comparison to those treated with standard dose of AL alone.

In vivo Antimalarial Activities of Russelia Equisetiformis in Plasmodium Berghei Infected Mice.

The rising problem of resistance to most commonly used antimalarials remains a major challenge in the control of malaria suggesting the need for new antimalarial agents. This work explores the antiplasmodial potential of ethanol extract of Russelia equisetiformis in chloroquine Plasmodium berghei infected mice. Swiss albino mice were intraperitoneally infected with chloroquine-resistant P. berghei (ANKA). Experimental mice were treated for four days consecutively with graded doses of plant extracts and standard antimalarial drugs (artesunate and chloroquine) at a dose of 10 mg/kg body weight used as control. The extract showed a dose-dependent activity in the chemosuppression of P. berghei parasites by 31.6, 44.7, 48.4 and 86.5% at doses of 100, 200, 400 and 800 mg/kg, while chloroquine (10 mg/kg) and artesunate produced 59.4 and 68.4%, respectively. The extract showed a significant decrease in parasitaemia (P<0.05). The level of parasitemia and decrease in weight in all the treated groups was significantly lower (P<0.05) compared with the infected but untreated mice. The plant extract was devoid of toxicity at the highest dose tested (5000 mg/kg). The study concluded that the ethanol extract of R. equisetiformis possesses antimalarial effect, which supports the folk medicine claim of its use in the treatment of malaria.