Antimalarial plant remedies from Burkina Faso: their potential for prophylactic use

The impact of anti-malarial markets on artemisinin resistance: perspectives from Burkina Faso

BACKGROUND

Widespread artemisinin resistance in Africa could be catastrophic when drawing parallels with the failure of chloroquine in the 1970s and 1980s. This article explores the role of anti-malarial market characteristics in the emergence and spread of arteminisin resistance in African countries, drawing on perspectives from Burkina Faso.

METHODS

Data were collected through in-depth interviews and focus group discussions. A representative sample of national policy makers, regulators, public and private sector wholesalers, retailers, clinicians, nurses, and community members were purposively sampled. Additional information was also sought via review of policy publications and grey literature on anti-malarial policies and deployment practices in Burkina Faso.

RESULTS

Thirty seven in-depth interviews and 6 focus group discussions were conducted. The study reveals that the current operational mode of anti-malarial drug markets in Burkina Faso promotes arteminisin resistance emergence and spread. The factors are mainly related to the artemisinin-based combination therapy (ACT) supply chain, to ACT quality, ACT prescription monitoring and to ACT access and misuse by patients.

CONCLUSION

Study findings highlight the urgent requirement to reform current characteristics of the anti-malarial drug market in order to delay the emergence and spread of artemisinin resistance in Burkina Faso. Four recommendations for public policy emerged during data analysis: (1) Address the suboptimal prescription of anti-malarial drugs, (2) Apply laws that prohibit the sale of anti-malarials without prescription, (3) Restrict the availability of street drugs, (4) Sensitize the population on the value of compliance regarding correct acquisition and intake of anti-malarials. Funding systems for anti-malarial drugs in terms of availability and accessibility must also be stabilized.

Contribution of Meliaceous plants in furnishing lead compounds for antiplasmodial and insecticidal drug development

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria remains one of the greatest threats to human life especially in the tropical and sub-tropical regions where it claims hundreds of thousands of lives of young children every year. Meliaceae represent a large family of trees and shrubs, which are widely used in African traditional medicine for the treatment of several ailments including fever due to malaria. The in vitro and in vivo antiplasmodial as well as insecticidal investigations of their extracts or isolated compounds have led to promising results but to the best of our knowledge, no specific review on the traditional uses, phytochemistry of the antiplasmodial, insecticidal and cytotoxic lead compounds and extracts of Meliaceae plants has been compiled.

AIMS

To review the literature up to 2021 on the Meliaceae family with antiplasmodial, insecticidal and cytotoxic activity.

MATERIALS AND METHODS

A number of online libraries including PubMed, Scifinder, Google Scholar and Web of Science were used in searching for information on antiplasmodial metabolites from Meliaceous plants. The keywords Meliaceae, malaria, Plasmodium, Anopheles and antiplasmodial were used to monitor and refine our search without language restriction.

RESULTS

The phytochemical investigations of genera of the family Meliaceae led to the isolation and characterization of a wide range of structural diversity of compounds, 124 of which have been evaluated for their antiplasmodial potency against 11 chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum strains. A total of 45 compounds were reported with promising insecticidal potentials against two efficient vector species, Anopheles stephensi Liston and A. gambiae Giles. Limonoids were the most abundant (51.6%) reported compounds and they exhibited the most promising antiplasmodial activity such as gedunin (3) which demonstrated an activity equal to quinine or azadirachtin (1) displaying promising larvicidal, pupicidal and adulticidal effects on different larval instars of A. stephensi with almost 100% larval mortality at 1 ppm concentration.

CONCLUSION

Studies performed so far on Meliaceae plants have reported compounds with significant antiplasmodial and insecticidal activity, lending support to the use of species of this family in folk medicine, for the treatment of malaria. Moreover, results qualified several of these species as important sources of compounds for the development of eco-friendly pesticides to control mosquito vectors. However, more in vitro, in vivo and full ADMET studies are still required to provide additional data that could guide in developing novel drugs and insecticides.

Ethnopharmacological evaluation of antioxidant, anti-angiogenic, and anti-inflammatory activity of some traditional medicinal plants used for treatment of cancer in Togo/Africa

ETHNOPHARMACOLOGICAL RELEVANCE

Cancer is a multistep disease and its management is exceedingly expensive. Nowadays medicinal plants are gaining more attention in drug discovery and approximately 70% of anticancer drugs were developed from natural products or plants. A strong candidate from medicinal plant with anticancer potential should have four major properties: antioxidant, anti-inflammatory, anti-angiogenic, and cytotoxic activities.

AIM OF THE STUDY

In order to assess Togolese traditional healer's claims about the anticancer potential of medicinal plants and obtain candidate plants for anticancer drug discovery, some species were selected from surveys and evaluated for their antioxidant, anti-inflammatory, anti-angiogenic and cytotoxic activities.

METHODS

Four species, Cochlospermum planchonii (CP), Piliostigma thonningii (PT), Paullinia pinnata (PP), and Securidaca longipedunculata (SL) were selected and analyzed to detect the phytochemical components. The mentioned bioactivities were evaluated using in vitro, ex vivo and in vivo assays.

RESULTS

Relative to SL extract, CP and PT have shown significantly high polyphenols and flavonoids content. The DPPH, FRAP, and TAC of the extracts revealed that CP, PT, and PP have a potent antioxidant effect compared to SL. MDA analysis revealed the same antioxidant activity as CP, PT and PP showed a minor MDA level. The egg albumin denaturation assay showed that IC50 of CP and PP was significantly higher than control (P < 0.05). In contrast, the Bovine Serum Albumin (BSA) results showed a nonsignificant effect (P > 0.05). Notably, SL extract was nonsignificant to control in both Egg Albumin and BSA. Furthermore, angiogenesis assay showed that SL at 50 μg/ml and PP at 100 μg/ml effectively reduced the number of blood vessels than control and showed a potent anti-angiogenic effect (2.7-fold and 2.5-fold, respectively, P < 0.05). No cytotoxicity on PBMC was reported for CP, PP, and PT up to 1000 μg/ml, whereas SL at 1000 μg/ml exhibit benign cytotoxicity (P < 0.0001).

CONCLUSION

This study provided in vitro evidence supporting further evaluation on cancer cell lines and tumors in vivo.

Natural-Product-Based Solutions for Tropical Infectious Diseases

About half of the world's population and 80% of the world's biodiversity can be found in the tropics. Many diseases are specific to the tropics, with at least 41 diseases caused by endemic bacteria, viruses, parasites, and fungi. Such diseases are of increasing concern, as the geographic range of tropical diseases is expanding due to climate change, urbanization, change in agricultural practices, deforestation, and loss of biodiversity. While traditional medicines have been used for centuries in the treatment of tropical diseases, the active natural compounds within these medicines remain largely unknown. In this review, we describe infectious diseases specific to the tropics, including their causative pathogens, modes of transmission, recent major outbreaks, and geographic locations. We further review current treatments for these tropical diseases, carefully consider the biodiscovery potential of the tropical biome, and discuss a range of technologies being used for drug development from natural resources. We provide a list of natural products with antimicrobial activity, detailing the source organisms and their effectiveness as treatment. We discuss how technological advancements, such as next-generation sequencing, are driving high-throughput natural product screening pipelines to identify compounds with therapeutic properties. This review demonstrates the impact natural products from the vast tropical biome have in the treatment of tropical infectious diseases and how high-throughput technical capacity will accelerate this discovery process.

Antiplasmodial, antimalarial activities and toxicity of African medicinal plants: a systematic review of literature

BACKGROUND

Malaria still constitutes a major public health menace, especially in tropical and subtropical countries. Close to half a million people mainly children in Africa, die every year from the disease. With the rising resistance to frontline drugs (artemisinin-based combinations), there is a need to accelerate the discovery and development of newer anti-malarial drugs. A systematic review was conducted to identify the African medicinal plants with significant antiplasmodial and/or anti-malarial activity, toxicity, as wells as assessing the variation in their activity between study designs (in vitro and in vivo).

METHODS

Key health-related databases including Google Scholar, PubMed, PubMed Central, and Science Direct were searched for relevant literature on the antiplasmodial and anti-malarial activities of African medicinal plants.

RESULTS

In total, 200 research articles were identified, a majority of which were studies conducted in Nigeria. The selected research articles constituted 722 independent experiments evaluating 502 plant species. Of the 722 studies, 81.9%, 12.4%, and 5.5% were in vitro, in vivo, and combined in vitro and in vivo, respectively. The most frequently investigated plant species were Azadirachta indica, Zanthoxylum chalybeum, Picrilima nitida, and Nauclea latifolia meanwhile Fabaceae, Euphorbiaceae, Annonaceae, Rubiaceae, Rutaceae, Meliaceae, and Lamiaceae were the most frequently investigated plant families. Overall, 248 (34.3%), 241 (33.4%), and 233 (32.3%) of the studies reported very good, good, and moderate activity, respectively. Alchornea cordifolia, Flueggea virosa, Cryptolepis sanguinolenta, Zanthoxylum chalybeum, and Maytenus senegalensis gave consistently very good activity across the different studies. In all, only 31 (4.3%) of studies involved pure compounds and these had significantly (p = 0.044) higher antiplasmodial activity relative to crude extracts. Out of the 198 plant species tested for toxicity, 52 (26.3%) demonstrated some degree of toxicity, with toxicity most frequently reported with Azadirachta indica and Vernonia amygdalina. These species were equally the most frequently inactive plants reported. The leaves were the most frequently reported toxic part of plants used. Furthermore, toxicity was observed to decrease with increasing antiplasmodial activity.

CONCLUSIONS

Although there are many indigenous plants with considerable antiplasmodial and anti-malarial activity, the progress in the development of new anti-malarial drugs from African medicinal plants is still slothful, with only one clinical trial with Cochlospermum planchonii (Bixaceae) conducted to date. There is, therefore, the need to scale up anti-malarial drug discovery in the African region.

Malaria transmission-blocking drugs: implications and future perspectives

As the world gets closer to eliminating malaria, the scientific community worldwide has begun to realize the importance of malaria transmission-blocking interventions. The onus of breaking the life cycle of the human malaria parasite Plasmodium falciparum predominantly rests upon transmission-blocking drugs because of emerging resistance to commonly used schizonticides and insecticides. This third part of our review series on malaria transmission-blocking entails transmission-blocking potential of preclinical transmission-blocking antimalarials and other non-malaria drugs/experimental compounds that are not in clinical or preclinical development for malaria but possess transmission-blocking potential. Collective analysis of the structure and the activity of these experimental compounds might pave the way toward generation of novel prototypes of next-generation transmission-blocking drugs.

A review of the traditional use of southern African medicinal plants for the treatment of malaria

ETHNOPHARMALOGICAL RELEVANCE

Malaria is one of the most prevalent and deadly parasitic diseases globally, with over 200 million new cases and nearly 500,000 deaths reported annually. It is estimated that approximately half of the world's population lives in malaria endemic areas. Malaria is substantially less prevalent in South Africa than in other African regions and the disease is limited to some regions of the Limpopo, Mpumalanga and KwaZulu-Natal provinces. However, it still has a significant impact on the health of the populations living in those regions. Traditional medicines have long been used in South Africa by multiple ethic groups and many people continue to rely on these natural therapies for their healthcare. The usage of South African medicinal plants in several traditional healing systems to treat malaria have been documented (particularly for Zulu and Venda traditional medicine), although ethnobotanical investigations of other ethnic groups living in endemic malaria areas remains relatively neglected.

AIM OF THE STUDY

To document the use of South African medicinal plants known to be used traditionally to treat Plasmodium spp. infections. We also critically reviewed the literature on the therapeutic properties of these and other South African plants screened against Plasmodium spp. parasites with the aim of highlighting neglected studies and fostering future research in this area.

MATERIALS AND METHODS

Books and ethnobotanical reviews were examined for medicinal plants used specifically for fever. Exclusion criteria were studies not involving southern African medicinal plants. Furthermore, while fever is a common symptom of malaria, if not accompanied by the term "malaria" it was not considered. Databases including PubMed, ScienceDirect, Scopus and Google Scholar were used to source research relevant to southern African plants and malaria. Exclusion criteria were those publications where full articles could not be accessed.

RESULTS

Eighty South African plant species were identified as traditional therapies for malaria. The majority of these species were documented in Zulu ethnobotanical records, despite malaria occurring in only a relatively small portion of the Zulu's traditional territory. Surprisingly, far fewer species were reported to be used by Venda, Ndebele, northern Sotho, Tsonga, Tswana, and Pedi people, despite them living in endemic malaria areas. Interestingly many of the identified species have not been investigated further. This review summarises the available ethnobotanical and laboratory research in this field, with the aim of promoting and focusing research on priority areas.

CONCLUSION

Although malaria remains a serious disease affecting millions of people, medicinal plants while used extensively, have not been given the attention warranted for further investigation.

Effects of Azadirachta indica seed kernel extracts on early erythrocytic schizogony of Plasmodium berghei and pro-inflammatory response in inbred mice

BACKGROUND

Medicinal plant research may contribute to develop new pharmacological control tools for vector borne diseases, such as malaria.

METHODS

The effects of methanol extracts (ME) obtained from seed kernel of ripe and unripe Azadirachta indica fruits were studied on erythrocytic proliferation of the rodent malaria parasite Plasmodium berghei strain ANKA and on mice pro-inflammatory response, as evaluated by measuring the matrix-metalloproteinase-9 (MMP-9) and tumour necrosis factor (TNF) plasma levels, in two mouse strains (C57BL/6 and BALB/c) which are considered as prototypical of Th1 and Th2 immune response, respectively.

RESULTS

ME obtained from seed kernel of unripe Azadirachta indica fruits decreased by about 30% the proportion of erythrocytes infected with the malaria parasite in C57BL/6 mice in the 4 days suppressive test. In this treatment group, MMP-9 and TNF levels were notably higher than those measured in the same mouse strain treated with the anti-malarial drug artesunate, Azadirachta indica kernel extracts from ripe fruits or solvent. In BALB/c mice, treatment with kernel extracts did not influence parasitaemia. MMP-9 and TNF levels measured in this mouse strain were notably lower than those recorded in C57BL/6 mice and did not vary among treatment groups.

CONCLUSIONS

The effects of the ME on the parasite-host interactions appeared to be mouse strain-dependent, but also related to the ripening stage of the neem fruits, as only the unripe fruit seed kernel extracts displayed appreciable bioactivity.

Comparing Medicinal Uses of Cochlospermaceae throughout Its Geographic Range with Insights from Molecular Phylogenetics

Species of the Cochlospermaceae, a small mostly pantropical plant family, were evaluated at a continental scale for medicinal uses in traditional medicine. This ethnobotanical information was placed in a phylogenetic framework to make informed predictions in the search for new medicines and bioactive compounds. Medicinal plant-use data were mapped onto a molecular phylogeny based on DNA sequences of nuclear and chloroplast markers. Associations of medicinal uses among closely related species occurring in different geographic regions and among diverse cultures were evaluated. The most common medicinal uses for these species are those used to treat skin ailments, gastro-intestinal problems, malaria, and liver issues. The plant species with the most numerous uses is Cochlospermum tinctorium, which occurs primarily in West Africa. Closely related species being used by cultural groups in different geographic regions to treat the same illnesses suggests the presence of bioactive compounds with potential biomedical value, since they may represent independent discoveries of similar medicinally-active compounds. This leads to the speculation that those closely related species not currently being used to treat these ailments may also contain identical or similar medicinally-active compounds and are worthy of laboratory investigations.

Hydroethanolic Extracts of Erigeron floribundus and Azadirachta indica Reduced Plasmodium berghei Parasitemia in Balb/c Mice

Malaria is one of the most important infectious diseases in Africa especially in Cameroon. The nonaccessibility to current treatments for poor people and the appearance of drug-resistant Plasmodium falciparum parasites stimulate the search for alternative treatments. The aim of this study was to evaluate the antimalarial activity and the safety of hydroethanolic extracts from Erigeron floribundus and Azadirachta indica. The crude hydroethanolic extracts of E. floribundus (HEEF) and A. indica (HEAI) were prepared via maceration of the whole plant powder of E. floribundus and the leaves of A. indica in 70% ethanol. The antimalarial activity was determined according to Peter's 4-day suppressive test using the murine model Plasmodium berghei/Balb C mice, while the acute and subacute toxicity tests were assessed according to the OECD 425 and 407 guidelines, respectively. The results indicate a reduction of parasitemia ranging from 49.75 ± 3.64 to 69.28 ± 1.36% for HEAI and from 30.46 ± 4.30 to 62.36 ± 2.32% for HEEI. Overall, HEEF and HEAI at doses of 60, 120, and 240 mg/kg b.w. and 75, 150, and 300 mg/kg b.w., respectively, showed a significant (p≤0.001) parasitemia reduction on P. berghei infecting BALB/c mice. HEEF and HEAI caused a significant (p<0.001) attenuation of body temperature drop in mice compared to negative control, except for the 150 mg/kg b.w. dose in the female group. Moreover, there was no mice mortality observed with these extracts even at 5000 mg/kg, while the aspartate amino transferase (ASAT) level of mice treated with 300 mg/kg b.w. of HEAI extract increased when compared with the control. The results of this study support the traditional use of these plants species extracts against malaria infection in rural zones of Northern Cameroon, therefore confirming their potential as sources for the development of efficient phytomedicines for malaria-poverty disease alleviation.

Neemazal ® as a possible alternative control tool for malaria and African trypanosomiasis?

BACKGROUND

Research efforts to identify possible alternative control tools for malaria and African trypanosomiasis are needed. One promising approach relies on the use of traditional plant remedies with insecticidal activities.

METHODS

In this study, we assessed the effect of blood treated with different doses of NeemAzal ® (NA, neem seed extract) on mosquitoes (Anopheles coluzzii) and tsetse flies (Glossina palpalis gambiensis) (i) avidity to feed on the treated blood, (ii) longevity, and (iii) behavioural responses to human and calf odours in dual-choice tests. We also gauged NeemAzal ® toxicity in mice.

RESULTS

In An. coluzzii, the ingestion of NA in bloodmeals offered by membrane feeding resulted in (i) primary antifeedancy; (ii) decreased longevity; and (iii) reduced response to host odours. In G. palpalis gambiensis, NA caused (i) a knock-down effect; (ii) decreased or increased longevity depending on the dose; and (iii) reduced response to host stimuli. In both cases, NA did not affect the anthropophilic rate of activated insects. Overall, the most significant effects were observed with NA treated bloodmeals at a dose of 2000 μg/ml for mosquitoes and 50 μg/ml for tsetse flies. Although no mortality in mice was observed after 14 days of follow-up at oral doses of 3.8, 5.6, 8.4 and 12.7 g/kg, behavioural alterations were noticed at doses above 8 g/kg.

CONCLUSION

This study revealed promising activity of NA on A. coluzzii and G. palpalis gambiensis but additional research is needed to assess field efficacy of neem products to be possibly integrated in vector control programmes.

Quality assessment and antiplasmodial activity of West African Cochlospermum species

The present study focuses on development of phytochemical methods for quality assessment of two West-African Cochlospermum species (Cochlospermum planchonii and Cochlospermum tinctorium) traditionally used for malaria treatment in Burkina Faso. Antimalarial activity of preparations from dried rhizomes (decoction) was tested against the chloroquine-sensitive Plasmodium strain 3D7 using the histidine-rich protein II (HRP2) drug susceptibility assay and compared with extract preparations using organic solvents of different polarity. Two main apocarotenoids were isolated from rhizomes of C. planchonii and unambiguously identified as dihydrocochloxanthine and cochloxanthine by spectroscopic methods. Comparative HPLC analyses of thirty-nine (39) samples from markets and from collections in natural habitats of both species showed a high variability in the accumulation of cochloxanthines and related carotenoids which were proven to be characteristic for rhizomes of both species and generally absent in leaves. Furthermore, content of total phenolics and antioxidant activities (DPPH and FRAP) as well as haemolytic activity of various extracts was tested. The HPLC method presented here was validated and provides a good separation of both compounds including 10 minor carotenoids. Extracts from both species and pure cochloxanthine offered pronounced antioxidant activities and weak haemolytic activity while, in contrast, dihydrocochloxanthine had a strong haemolytic effect at the highest concentration analysed. However, cochloxanthine as well as dihydrocochloxanthine showed erythroprotective effects against the haemolytic activity of the reference saponin. Moderate antiplasmodial activity between 16 and 63 μg/ml were observed with all tested extracts, and lower IC50 values were obtained with pure dihydrocochloxanthine (IC50=6.9 μg/ml), cochloxanthine (IC50=6.8 μg/ml), the DCM fraction (IC50=2.4 μg/ml) and the ethyl acetate fraction (IC50=11.5μg/ml) derived from a methanolic extract of C. planchonii. This study shows a major variability of carotenoid content and antiplasmodial activity of both C. planchonii and C. tinctorium. The high haemolytic activity of dihydrocochloxanthine (at 100 μg/ml) should be considered as a selection criterion for choosing species phenotypes for treatment.

Impact of repeated NeemAzal-treated blood meals on the fitness of Anopheles stephensi mosquitoes

BACKGROUND

Herbal remedies are widely used in many malaria endemic countries to treat patients, in particular in the absence of anti-malarial drugs and in some settings to prevent the disease. Herbal medicines may be specifically designed for prophylaxis and/or for blocking malaria transmission to benefit both, the individual consumer and the community at large. Neem represents a good candidate for this purpose due to its inhibitory effects on the parasite stages that cause the clinical manifestations of malaria and on those responsible for infection in the vector. Furthermore, neem secondary metabolites have been shown to interfere with various physiological processes in insect vectors. This study was undertaken to assess the impact of the standardised neem extract NeemAzal on the fitness of the malaria vector Anopheles stephensi following repeated exposure to the product through consecutive blood meals on treated mice.

METHODS

Batches of An. stephensi mosquitoes were offered 5 consecutive blood meals on female BALB/c mice treated with NeemAzal at an azadirachtin A concentration of 60, 105 or 150 mg/kg. The blood feeding capacity was estimated by measuring the haematin content of the rectal fluid excreted by the mosquitoes during feeding. The number of eggs laid was estimated by image analysis and their hatchability assessed by direct observations.

RESULTS

A dose and frequency dependent impact of NeemAzal treatment on the mosquito feeding capacity, oviposition and egg hatchability was demonstrated. In the 150 mg/kg treatment group, the mosquito feeding capacity was reduced by 50% already at the second blood meal and by 50 to 80% in all treatment groups at the fifth blood meal. Consequently, a 50 - 65% reduction in the number of eggs laid per female mosquito was observed after the fifth blood meal in all treatment groups. Similarly, after the fifth treated blood meal exposure, hatchability was found to be reduced by 62% and 70% in the 105 and 150 mg/kg group respectively.

CONCLUSIONS

The findings of this study, taken together with the accumulated knowledge on neem open the challenging prospects of designing neem-based formulations as multi-target phytomedicines exhibiting preventive, parasite transmission-blocking as well as anti-vectorial properties.

Transmission blocking activity of Azadirachta indica and Guiera senegalensis extracts on the sporogonic development of Plasmodium falciparum field isolates in Anopheles coluzzii mosquitoes

BACKGROUND

Targeting the stages of the malaria parasites responsible for transmission from the human host to the mosquito vector is a key pharmacological strategy for malaria control. Research efforts to identify compounds that are active against these stages have significantly increased in recent years. However, at present, only two drugs are available, namely primaquine and artesunate, which reportedly act on late stage gametocytes.

METHODS

In this study, we assessed the antiplasmodial effects of 5 extracts obtained from the neem tree Azadirachta indica and Guiera senegalensis against the early vector stages of Plasmodium falciparum, using field isolates. In an ex vivo assay gametocytaemic blood was supplemented with the plant extracts and offered to Anopheles coluzzii females by membrane feeding. Transmission blocking activity was evaluated by assessing oocyst prevalence and density on the mosquito midguts.

RESULTS

Initial screening of the 5 plant extracts at 250 ppm revealed transmission blocking activity in two neem preparations. Up to a concentration of 70 ppm the commercial extract NeemAzal completely blocked transmission and at 60 ppm mosquitoes of 4 out of 5 replicate groups remained uninfected. Mosquitoes fed on the ethyl acetate phase of neem leaves at 250 ppm showed a reduction in oocyst prevalence of 59.0% (CI₉₅ 12.0 - 79.0; p < 10-4) and in oocyst density of 90.5% (CI₉₅ 86.0 - 93.5; p < 10-4 ), while the ethanol extract from the same plant part did not exhibit any activity. No evidence of transmission blocking activity was found using G. senegalensis ethyl acetate extract from stem galls.

CONCLUSIONS

The results of this study highlight the potential of antimalarial plants for the discovery of novel transmission blocking molecules, and open up the potential of developing standardized transmission blocking herbal formulations as malaria control tools to complement currently used antimalarial drugs and combination treatments.

In vitro antiplasmodial activity of some medicinal plants of Burkina Faso

Malaria remains a major public health problem due to the emergence and spread of Plasmodium falciparum drug resistance. There is an urgent need to investigate new sources of antimalarial drugs which are more effective against Plasmodium falciparum. One of the potential sources of antimalarial drugs is traditional medicinal plants. In this work, we studied the in vitro antiplasmodial activity of chloromethylenic, methanolic, and MeOH/H2O (1/1) crude extracts and decoction obtained from eight medicinal plants collected in Burkina Faso and of total alkaloids for five plants. Extracts were evaluated in vitro for efficacy against Plasmodium falciparum strain K1, which is resistant to chloroquine, pyrimethamine and proguanil using the fluorescence-based SYBR Green I assay. The antiproliferative activity on human-derived hepatoma cell line HepG2 and Chinese hamster ovary (CHO) cells was evaluated using the 3-[4,5-dimethylthyazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test in order to determine the selectivity index. Among the plant extracts tested for in vitro antiplasmodial activity, 16 were considered to be inactive (with IC50 > 10 μg/ml), six showed a moderate activity (5 < IC50 ≤ 10 μg/ml), and six were found to have a good in vitro activity with IC50 value ≤ 5 μg/ml. The highest antiplasmodial activity was found for extracts from: the alkaloid leaf extract and the chloromethylenic extracts of Combretum fragrans (IC50 = 3 μg/ml, IC50 = 5 μg/ml), the total alkaloids and the chloromethylenic leaf extracts of Combretum collinum (IC50 = 4 μg/ml), the MeOH/H2O leaf extract of Terminalia avicennioides (IC50 = 3.5 μg/ml), and the alkaloid leaf extract of Pavetta crassipes (IC50 = 5 μg/ml). Three other extracts showed moderate antiplasmodial activity (5 < IC50 ≤ 10 μg/ml): Terminalia avicennioides and Combretum fragrans methanolic extracts and Acacia kirkii alkaloid leaf extract (IC50 = 6.5, 9 and 10 μg/ml respectively). The Terminalia avicennioides crude MeOH/H2O (80:20 v/v) extract of the leaves was submitted to a successive liquid/liquid extraction with ethylacetate and n-butanol respectively. The extracts were investigated for in vitro antiplasmodial activity and antioxidant properties using DPPH(·), ABTS(+) and FRAP methods. The ethylacetate extract showed the best antiplasmodial activity (7 μg/ml) and the active constituent was isolated as ellagic acid by bioguided fractionation with an IC50 = 0.2 μM on Plasmodium falciparum and SI = 152. Besides, Terminalia avicennioides leaf extract and ellagic acid showed a good antioxidant activity. Our finding confirms the importance of investigating the antimalarial activity of plant species used in traditional medicine. Overall, two plants belonging to the Combretaceae family, Combretum fragrans and Combretum collinum appeared to be the best candidates and will be further investigated for their antiplasmodial properties, in order to isolate the molecules responsible for the antiplasmodial activity.

Ethnobotanical survey of malaria prophylactic remedies in Odisha, India

AIM OF THE STUDY

To investigate the plants traditionally used for prevention of malaria in Cuttack, Gajapati and Koraput districts of Odisha state, eastern India.

MATERIALS AND METHODS

An ethnobotanical survey was carried out among 20 traditional healers who were sampled based on recommendations of local elders and local non-government organizations. Data were collected through semi-structured interview.

RESULTS

The study revealed the use of 16 traditional plant species belonging to 12 families for prevention of malaria. Andrographis paniculata, Azadirachta indica, Nyctanthes arbor-tristis, Ocimum sanctum, Piper nigrum, Zingiber officinale were the most commonly reported plants for their malaria prophylactic use by the healers of three districts of Odisha. Most of the remedies were used in decoction form.

CONCLUSIONS

Findings of this study provide a lead to explore traditional plants for malaria preventive potential through further pre-clinical and clinical studies.

Anti-plasmodial activity of Dicoma tomentosa (Asteraceae) and identification of urospermal A-15-O-acetate as the main active compound

Background

Natural products could play an important role in the challenge to discover new anti-malarial drugs. In a previous study, Dicoma tomentosa (Asteraceae) was selected for its promising anti-plasmodial activity after a preliminary screening of several plants traditionally used in Burkina Faso to treat malaria. The aim of the present study was to further investigate the anti-plasmodial properties of this plant and to isolate the active anti-plasmodial compounds.

Methods

Eight crude extracts obtained from D. tomentosa whole plant were tested in vitro against two Plasmodium falciparum strains (3D7 and W2) using the p-LDH assay (colorimetric method). The Peters’ four-days suppressive test model (Plasmodium berghei-infected mice) was used to evaluate the in vivo anti-plasmodial activity. An in vitro bioguided fractionation was undertaken on a dichloromethane extract, using preparative HPLC and TLC techniques. The identity of the pure compound was assessed using UV, MS and NMR spectroscopic analysis. In vitro cytotoxicity against WI38 human fibroblasts (WST-1 assay) and haemolytic activity were also evaluated for extracts and pure compounds in order to check selectivity.

Results

The best in vitro anti-plasmodial results were obtained with the dichloromethane, diethylether, ethylacetate and methanol extracts, which exhibited a high activity (IC₅₀ ≤ 5 μg/ml). Hot water and hydroethanolic extracts also showed a good activity (IC₅₀ ≤ 15 μg/ml), which confirmed the traditional use and the promising anti-malarial potential of the plant. The activity was also confirmed in vivo for all tested extracts. However, most of the active extracts also exhibited cytotoxic activity, but no extract was found to display any haemolytic activity. The bioguided fractionation process allowed to isolate and identify a sesquiterpene lactone (urospermal A-15-O-acetate) as the major anti-plasmodial compound of the plant (IC₅₀ < 1 μg/ml against both 3D7 and W2 strains). This was also found to be the main cytotoxic compound (SI = 3.3). While this melampolide has already been described in the plant, this paper is the first report on the biological properties of this compound.

Conclusions

The present study highlighted the very promising anti-plasmodial activity of D. tomentosa and enabled to identify its main active compound, urospermal A-15-O-acetate. The high anti-plasmodial activity of this compound merits further study about its anti-plasmodial mechanism of action. The active extracts of D. tomentosa, as well as urospermal A 15-O-acetate, displayed only a moderate selectivity, and further studies are needed to assess the safety of the use of the plant by the local population.