In vitro anti-plasmodial and in vivo anti-malarial activity of some plants traditionally used for the treatment of malaria by the Meru community in Kenya

Potential of medicinal plants as antimalarial agents: a review of work done at Kenya Medical Research Institute

Background: Medicinal plants have traditionally been used as remedies against malaria. The present review attempted to compile data on scientific research evidence on antimalarial medicinal plants screened at Kenya Medical Research Institute (KEMRI), Center for Traditional Medicine and Drug (CTMDR) Research from January 2003 to December 2021. Methods: A systematic review was conducted using a predefined protocol based on PRISMA. Search was performed in Google Scholar and PubMed. One hundred and eight journal articles were identified 37 of which published on antimalarial/antiplasmodial work. Thirty journal articles with at least one author from KEMRI-CTMDR and accessible in full were selected for analysis. Relevant data was captured in MS Excel format and descriptive statistics, percentages and tables used to summarize the findings. Results: Assessment of individual plant species was considered as an independent study resulting in 1170 antiplasmodial/antimalarial tests done from 197 plant species. One hundred and fifty plant species were screened in vitro, one in vivo and 46 were both in vivo and in vitro. Three hundred and forty-four of tests reported good activity (IC50 < 10 μg/mL or parasite suppression rate of ≥50%), 414 moderate activity (IC50 values of 10-49 μg/mL or parasite suppression rate of 30%-49%) and 412 were reports of inactivity (IC50 ˃ 50 μg/mL or parasite suppression rate of <30%). Fuerstia africana and Ludwigia erecta were reported to have the highest activities, with IC50 < 1 μg/mL against Plasmodium falciparum D6 strain and chemosuppression in mice at an oral dose of 100 mg/kg, was reported as 61.9% and 65.3% respectively. Fifty five antimalarial/antiplasmodial active compounds isolated from eight plant species were reported with resinone (39) having the best activity (IC50 < 1 μg/mL). Conclusion: Though 344 of tests reported promising antimalarial activity, it was noted that there was limited evaluation of these plants in animal models, with only 9.0% (105/1170) studies and no clinical trials. This highlights an important research gap emphasizing the need for drug development studies that aim to progress study findings from preclinical to clinical studies. There is still need for extensive research on promising plant species aimed at developing new plant based antimalarial drugs.

Expression of the Fab enzymes (Fab I and Fab Z) from Plasmodium falciparum after exposure to Artemisia afra plant extracts and drugs screening

The emergence and spread of drug resistance of the malaria parasite to the main treatment emphasize the need to develop new antimalarial drugs. In this context, the fatty acid biosynthesis (FAS_II) pathway of the malaria parasite is one of the ideal targets due to its crucial role in parasite survival. In this study, we report the expression and the affinity binding of Fab_I and Fab_Z after exposure to the parasite with different extracts of the Artemisia afra. The parasites were exposed for 2 days to different extracts. Gene expression was done to determine the level of expression of the fab enzymes after treatments. A GCMS was run to determine the different compounds of the plant extracts, followed by a virtual screening between the fab enzymes and the active compounds using Pyrex. The results showed different expression patterns of the Fab enzymes. Fab_I expression was downregulated in the W2 and D6 strains by the ethanolic extract but was increased by Hexane and DCM extracts. A different expression pattern was observed for Fab_Z. It was all upregulated except in the D6 strain when exposed to the ethanolic and hexane extracts. Virtual screening showed an affinity with many compounds. Hits compounds with high binding energy were detected. 11alphaHydroxyprogesterone and Aspidospermidin-17-ol were found to have high binding energy with Fab_I respectively (- 10.7 kcal/mol; - 10.2 kcal/mol). Fab_Z shows also high affinity with 11alpha-Hydroxyprogesterone (- 10 kcal/mol) and Thiourea (- 8.4 kcal/mol). This study shows the potential of A. afra to be used as a new source of novel antimalarial compounds.

Artemisia annua and Artemisia afra tea infusions vs. artesunate-amodiaquine (ASAQ) in treating Plasmodium falciparum malaria in a large scale, double blind, randomized clinical trial

BACKGROUND AND OBJECTIVE

Prior small-scale clinical trials showed that Artemisia annua and Artemisia afra infusions, decoctions, capsules, or tablets were low cost, easy to use, and efficient in curing malaria infections. In a larger-scale trial in Kalima district, Democratic Republic of Congo, we aimed to show A. annua and/or A. afra infusions were superior or at least equivalent to artesunate-amodiaquine (ASAQ) against malaria.

METHODS

A double blind, randomized clinical trial with 957 malaria-infected patients had two treatment arms: 472 patients for ASAQ and 471 for Artemisia (248 A. annua, 223 A. afra) remained at end of the trial. ASAQ-treated patients were treated per manufacturer posology, and Artemisia-treated patients received 1 l/d of dry leaf/twig infusions for 7 d; both arms had 28 d follow-up. Parasitemia and gametocytes were measured microscopically with results statistically compared among arms for age and gender.

RESULTS

Artemisinin content of A. afra was negligible, but therapeutic responses of patients were similar to A. annua-treated patients; trophozoites cleared after 24  h, but took up to 14 d to clear in ASAQ-treated patients. D28 cure rates defined as absence of parasitemia were for pediatrics 82, 91, and 50% for A. afra, A. annua and ASAQ; while for adults cure rates were 91, 100, and 30%, respectively. Fever clearance took 48  h for ASAQ, but 24  h for Artemisia. From D14-28 no Artemisia-treated patients had microscopically detectable gametocytes, while 10 ASAQ-treated patients remained gametocyte carriers at D28. More females than males were gametocyte carriers in the ASAQ arm but were unaffected in the Artemisia arms. Hemoglobin remained constant at 11 g/dl for A. afra after D1, while for A. annua and ASAQ it decreased to 9-9.5  g/dl. Only 5.0% of Artemisia-treated patients reported adverse effects, vs. 42.8% for ASAQ.

CONCLUSION

A. annua and A. afra infusions are polytherapies with better outcomes than ASAQ against malaria. In contrast to ASAQ, both Artemisias appeared to break the cycle of malaria by eliminating gametocytes. This study merits further investigation for possible inclusion of Artemisia tea infusions as an alternative for fighting and eradicating malaria.

Bioassay-guided isolation and identification of gametocytocidal compounds from Artemisia afra (Asteraceae)

BACKGROUND

Optimal adoption of the malaria transmission-blocking strategy is currently limited by lack of safe and efficacious drugs. This has sparked the exploration of different sources of drugs in search of transmission-blocking agents. While plant species have been extensively investigated in search of malaria chemotherapeutic agents, comparatively less effort has been channelled towards exploring them in search of transmission-blocking drugs. Artemisia afra (Asteraceae), a prominent feature of South African folk medicine, is used for the treatment of a number of diseases, including malaria. In search of transmission-blocking compounds aimed against Plasmodium parasites, the current study endeavoured to isolate and identify gametocytocidal compounds from A. afra.

METHODS

A bioassay-guided isolation approach was adopted wherein a combination of solvent-solvent partitioning and gravity column chromatography was used. Collected fractions were continuously screened in vitro for their ability to inhibit the viability of primarily late-stage gametocytes of Plasmodium falciparum (NF54 strain), using a parasite lactate dehydrogenase assay. Chemical structures of isolated compounds were elucidated using UPLC-MS/MS and NMR data analysis.

RESULTS

Two guaianolide sesquiterpene lactones, 1α,4α-dihydroxybishopsolicepolide and yomogiartemin, were isolated and shown to be active (IC50 < 10 μg/ml; ~ 10 μM) against both gametocytes and intra-erythrocytic asexual P. falciparum parasites. Interestingly, 1α,4α-dihydroxybishopsolicepolide was significantly more potent against late-stage gametocytes than to early-stage gametocytes and intra-erythrocytic asexual P. falciparum parasites. Additionally, both isolated compounds were not overly cytotoxic against HepG2 cells in vitro.

CONCLUSION

This study provides the first instance of isolated compounds from A. afra against P. falciparum gametocytes as a starting point for further investigations on more plant species in search of transmission-blocking compounds.

Treatment of malaria and related symptoms using traditional herbal medicine in Ethiopia

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants have always been an integral part of different cultures in Ethiopia in the treatment of different illnesses including malaria and related symptoms. However, due to lack of proper documentation, urbanization, drought, acculturation and deforestation, there is an increased risk of losing this traditional knowledge. Hence, the use of the indigenous knowledge should be well documented and validated for potential future use.

AIM OF THE STUDY

To gather and document information on medicinal plants which are used in the traditional treatment of malaria and related symptoms in Ethiopia.

MATERIALS AND METHODS

First, an ethnomedicinal survey of plants was conducted in 17 districts of Jimma zone, the Oromia national regional state of Ethiopia. Jimma zone is malarious and rich in natural flora. A total of 115 traditional healers were interviewed using a semi-structured questionnaire containing personal data of the respondents, and information on medicinal plants used to treat malaria and related symptoms. In addition, a literature search using Medline/PubMed, Google Scholar, ScienceDirect and HINARI was conducted on the indigenous use, in-vitro/in-vivo anti-malarial activity reports, and the chemical characterization of medicinal plants of Ethiopia used against malaria.

RESULTS

From ethnomedicinal survey, a total of 28 species of plants used in the traditional treatment of malaria and related symptoms in Jimma Zone were collected, identified and documented. In addition, the literature search revealed that 124 medicinal plant species were reported to be traditionally used in the treatment of malaria in Ethiopia. From both ethnomedicinal survey and the literature search, Asteraceae and Fabaceae were the most represented families and Allium sativum L., Carica papaya L., Vernonia amygdalina Del., Lepidium sativum L. and Croton macrostachyus Del. were the most frequently reported plant species for their anti-malarial use. The dominant plant parts used in the preparation of remedies were leaves. About 54% of the medicinal plants documented in the survey have been reported as an anti-malarial plant in the literature search. Furthermore, the in-vitro and in-vivo anti-plasmodial activity reports of extracts from some of plant species were found to support the traditional claim of the documented plants. Moreover, literatures indicate that several secondary metabolites isolated from certain plant species that are traditionally used for the treatment of malaria and related symptoms in Ethiopia demonstrate strong anti-plasmodial activity.

CONCLUSIONS

The result of the current study showed that traditional knowledge is still playing an important role in the management of malaria and related symptoms in Ethiopia. Allium sativum L., Carica papaya L., Vernonia amygdalina Del., and Lepidium sativum L. are the most commonly reported species as anti-malarial plants and the traditional claim of some species was supported by known anti-plasmodial activity and bioactivity reports. The finding of this study is important in the rational prioritization of plant species which are potentially used for investigating new compounds, which could be efficacious for malaria treatment.

Artemisinin-based antimalarial research: application of biotechnology to the production of artemisinin, its mode of action, and the mechanism of resistance of Plasmodium parasites

Malaria is a worldwide disease caused by Plasmodium parasites. A sesquiterpene endoperoxide artemisinin isolated from Artemisia annua was discovered and has been accepted for its use in artemisinin-based combinatorial therapies, as the most effective current antimalarial treatment. However, the quantity of this compound produced from the A. annua plant is very low, and the availability of artemisinin is insufficient to treat all infected patients. In addition, the emergence of artemisinin-resistant Plasmodium has been reported recently. Several techniques have been applied to enhance artemisinin availability, and studies related to its mode of action and the mechanism of resistance of malaria-causing parasites are ongoing. In this review, we summarize the application of modern technologies to improve the production of artemisinin, including our ongoing research on artemisinin biosynthetic genes in other Artemisia species. The current understanding of the mode of action of artemisinin as well as the mechanism of resistance against this compound in Plasmodium parasites is also presented. Finally, the current situation of malaria infection and the future direction of antimalarial drug development are discussed.

Cytotoxicity of 91 Kenyan indigenous medicinal plants towards human CCRF-CEM leukemia cells

ETHNOPHARMACOLOGICAL RELEVANCE

Plants from Kenyan flora are traditionally used against many ailments, including cancer and related diseases. Cancer is characterized as a condition with complex signs and symptoms. Recently there are recommendations that ethnopharmacological usages such as immune and skin disorders, inflammatory, infectious, parasitic and viral diseases should be taken into account when selecting plants that treat cancer.

AIM

The present study was aimed at investigating the cytotoxicity of a plethora of 145 plant parts from 91 medicinal plants, most of which are used in the management of cancer and related diseases by different communities in Kenya, against CCRF-CEM leukemia cell line.

MATERIALS AND METHODS

Extracts from different plant parts (leaves, stems, stem bark, roots, root barks, aerial parts and whole herb) were obtained by cold percolation using different solvent systems, such as (1:1v/v) dichloromethane (CH2Cl2) and n-hexane (1), methanol (MeOH) and CH2Cl2 (2); neat MeOH (3), 5% H2O in MeOH (4) and with ethanol (EtOH, 5); their cytotoxicities were determined using the resazurin reduction assay against CCRF-CEM cells.

RESULTS

At a single concentration of 10μg/mL, 12 out of 145 extracts exhibited more than 50% cell inhibition. These include samples from the root bark of Erythrina sacleuxii (extracted with 50% n-hexane-CH2Cl2), the leaves of Albizia gummifera, and Strychnos usambarensis, the stem bark of Zanthoxylum gilletii, Bridelia micrantha, Croton sylvaticus, and Albizia schimperiana; the root bark of Erythrina burttii and E. sacleuxii (extracted with 50% CH2Cl2-MeOH), the stem bark of B. micrantha and Z. gilletii (extracted using 5% MeOH-H2O) and from the berries of Solanum aculeastrum (extracted with neat EtOH). The EtOH extract of the berries of S. aculeastrum and A. schimperiana stem bark extract displayed the highest cytotoxicity towards leukemia CCRF-CEM cells, with IC50 values of 1.36 and 2.97µg/mL, respectively. Other extracts having good activities included the extracts of the stem barks of Z. gilletii and B. micrantha and leaves of S. usambarensis with IC50 values of 9.04, 9.43 and 11.09µg/mL, respectively.

CONCLUSIONS

The results of this study provided information related to the possible use of some Kenyam medicinal plants, and mostly S. aculeastrum, A. schimperiana, C. sylvaticus, Z. gilletii, B. micrantha and S. usambarensis in the treatment of leukemia. The reported data helped to authenticate the claimed traditional use of these plants. However, most plants are used in combination as traditional herbal concoctions. Hence, the cytotoxicity of corresponding plant combinations should be tested in vitro to authenticate the traditional medical practitioners actual practices.

Plants as antimalarial agents in Sub-Saharan Africa

Although the burden of malaria is decreasing, parasite resistance to current antimalarial drugs and resistance to insecticides by vector mosquitoes threaten the prospects of malaria elimination in endemic areas. Corollary, there is a scientific departure to discover new antimalarial agents from nature. Because the two antimalarial drugs quinine and artemisinin were discovered through improved understanding of the indigenous knowledge of plants, bioprospecting Sub-Saharan Africa's enormous plant biodiversity may be a source of new and better drugs to treat malaria. This review analyses the medicinal plants used to manage malaria in Sub-Saharan Africa. Chemical compounds with antiplasmodial activity are described. In the Sub-Saharan African countries cited in this review, hundreds of plants are used as antimalarial remedies. While the number of plant species is not exhaustive, plants used in more than one country probably indicate better antimalarial efficacy and safety. The antiplasmodial data suggest an opportunity for inventing new antimalarial drugs from Sub-Saharan-African flora.

Medicinal plants used by traditional healers for the treatment of malaria in the Chipinge district in Zimbabwe

ETHNOPHARMACOLOGICAL RELEVANCE

Because about 50% of the Zimbabwean population is at risk of contracting malaria each year, the majority of people, especially in rural areas, use traditional plant-based medicines to combat malaria. This explorative ethnobotanical survey was undertaken to document how malaria is conceptualized and diagnosed by traditional healers, and to record the medicinal plants used in the prevention and treatment of malaria, their mode of preparation and administration.

MATERIALS AND METHODS

The research was conducted in three villages in Headman Muzite׳s area and in Chiriga village. These villages are located in the Chipinge district in the Manicaland Province in Zimbabwe.Traditional healers were selected with the assistance of the headman of the Muzite area and a representative of the Zimbabwe National Traditional Healers Association. Semi-structured interviews were conducted with 14 traditional healers from four villages in the Chipinge district in Zimbabwe.

RESULTS

In total, 28 plants from 16 plant families are used by the healers who manage malaria with medicinal plants. The most cited plant is Cassia abbreviata Oliv. (Leguminosae) followed by Aristolochia albida Duch (Aristolociaceae) and Toddalia asiatica (L.) Lam. (Rutaceae). Roots (55.3%) are the most common part used. Most of the plant parts used to treat malaria are stored as dried powders in closed bottles. The powders are soaked in hot or cold water and the water extract is taken as the active medicine. The healers consider their medicinal knowledge as a spiritual family heritage. Only 25% of the healers refer the malaria patients that do not respond to their treatment to hospital - they believe evil spirits cause their remedies to failure and they would rather try a different plant or perform a cleansing ceremony.

CONCLUSIONS

Local knowledge of medicinal plants in the treatment of malaria still exists in all four villages surveyed and traditional healers appear to play an important role in primary health care services in this remote rural area in Zimbabwe. This explorative survey underscores the need to preserve and document traditional healing for managing malaria and for more future scientific research on the plants to determine their efficacy and their safety. This could improve their traditional anti-malarial recipes and might contribute to a better integration of Zimbabwean traditional medicine into the national health system in the future.

Ornamental exterior versus therapeutic interior of Madagascar periwinkle (Catharanthus roseus): the two faces of a versatile herb

Catharanthus roseus (L.) known as Madagascar periwinkle (MP) is a legendary medicinal plant mostly because of possessing two invaluable antitumor terpenoid indole alkaloids (TIAs), vincristine and vinblastine. The plant has also high aesthetic value as an evergreen ornamental that yields prolific blooms of splendid colors. The plant possesses yet another unique characteristic as an amiable experimental host for the maintenance of the smallest bacteria found on earth, the phytoplasmas and spiroplasmas, and serves as a model for their study. Botanical information with respect to synonyms, vernacular names, cultivars, floral morphology, and reproduction adds to understanding of the plant while the geography and ecology of periwinkle illustrate the organism's ubiquity. Good agronomic practices ensure generous propagation of healthy plants that serve as a source of bioactive compounds and multitudinous horticultural applications. The correlation between genetic diversity, variants, and TIA production exists. MP is afflicted with a whole range of diseases that have to be properly managed. The ethnobotanical significance of MP is exemplified by its international usage as a traditional remedy for abundant ailments and not only for cancer. TIAs are present only in micro quantities in the plant and are highly poisonous per se rendering a challenge for researchers to increase yield and reduce toxicity.

Ethnobotanical survey on medicinal plants used by Guinean traditional healers in the treatment of malaria

ETHNOPHARMACOLOGICAL RELEVANCE

The objective of the present study was to collect and document information on herbal remedies traditionally used for the treatment of malaria in Guinea.

MATERIALS AND METHODS

The survey was carried out from May 2008 to September 2010 and targeted traditional medical practitioners and herbalists. The questionnaire and oral interviews were based on the standardized model which was prepared by the "Centre de Recherche et de Valorisation des Plantes Médicinales (CRVPM) - Dubréka".

RESULTS AND DISCUSSION

A total of 258 people (141 males and 117 females) from which 150 traditional healers and 108 herbalists were interviewed. The age of informants ranged from 28 to 82 years old. 57% (149/258) of the interviewees were more than 50 years old. The respondents had good knowledge of the symptoms of malaria, and a fairly good understanding of the causes. One hundred thirteen plant species were recorded, out of which 109 were identified. They belonged to 84 genera and 46 families. The most frequently cited plants were Vismia guineensis, Parkia biglobosa, Nauclea latifolia, Harungana madagascariensis, Terminalia macroptera, Crossopteryx febrifuga, Terminalia albida, Annona senegalensis, and Nauclea pobeguinii. The leaves were most frequently used (80/113 species), followed by stem bark (38/113 species) and roots (4/113 species). The remedies were mostly prepared by decoction (111 species), followed by maceration (seven species). Only one species was prepared by infusion.

CONCLUSION

The present study showed that traditional healers in Guinea have a consistent knowledge of antimalarial plants. Further research should be carried out to compare the anti-malarial activity of the different species, and to check if their use against malaria can be scientifically validated.

Antimicrobial, Antioxidant, and Wound Healing Properties of Kigelia africana (Lam.) Beneth. and Strophanthus hispidus DC

Microbial infections of various types of wounds are a challenge to the treatment of wounds and wound healing. The study was to investigate antimicrobial and antioxidant properties of methanol leaf and stem bark extracts of Kigelia africana and methanol leaf and root extracts of Strophanthus hispidus and also to determine wound healing properties of the extracts. The antimicrobial activities of the methanol extracts were determined against two Gram-positive and two Gram-negative bacteria and a fungus using agar diffusion and micro-dilution methods. The antioxidant activity was determined using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) method. The influence of the extracts on rate of wound closure was investigated using the excision wound model and histopathological investigation of treated and untreated wound tissues performed. The MICs of leaf extract of K. africana against test organisms were 2.5-7.5 mg/mL and stem bark extract were 2.25-7.5 mg/mL. The leaf extract of S. hispidus had MIC range of 2.5-7.5 mg/mL and 2.5-10 mg/mL for root extract. The IC50 of leaf and stem bark extracts of K. africana were 56.9 and 13.7  μ g/mL, respectively and leaf and root of S. hispidus were 49.8 and 45.1  μ g/mL, respectively. K. africana extracts (7.5% w/w) showed significant (P < 0.05) wound contraction at day 7 with 72% of wound closure whiles significant (P < 0.05) wound contractions were observed on day 11 for stem bark of K. africana, leaf and root extracts of S. hispidus. Wound tissues treated with the extracts showed improved collagenation, re-epitheliazition and rapid granulation formation compared with untreated wound tissues. The extracts were found to contain alkaloids, saponins, tannins, flavonoids, carbohydrates, and sapogenetic glycosides. The HPLC finger-printing of the extracts were developed. The leaf, stem bark and root extracts of K. africana and S. hispidus exhibited antimicrobial, antioxidant, and enhanced wound healing properties and these may justify the medicinal uses of the plants for treatment of microbial infections and wounds.

Comparative functional analysis of CYP71AV1 natural variants reveals an important residue for the successive oxidation of amorpha-4,11-diene

Artemisinin is an antimalarial sesquiterpenoid isolated from the aerial parts of the plant Artemisia annua. CYP71AV1, a cytochrome P450 monooxygenase was identified in the artemisinin biosynthetic pathway. CYP71AV1 catalyzes three successive oxidation steps at the C12 position of amorpha-4,11-diene to produce artemisinic acid. In this study, we isolated putative CYP71AV1 orthologs in different species of Artemisia. Comparative functional analysis of CYP71AV1 and its putative orthologs, together with homology modeling, enabled us to identify an amino acid residue (Ser479) critical for the second oxidation reaction catalyzed by CYP71AV1. Our results clearly show that a comparative study of natural variants is useful to investigate the structure-function relationships of CYP71AV1.

Medicinal plants used in the management of chronic joint pains in Machakos and Makueni counties, Kenya

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional medicines play an important role in the management of chronically painful and debilitating joint conditions, particularly in the rural Africa. However, their potential use as sources of medicines has not been fully exploited. The present study was carried to find the medicinal plants traditionally used to manage chronic joint pains in Machakos and Makueni counties in Kenya.

MATERIALS AND METHODS

To obtain this ethnobotanical information, 30 consenting traditional herbal medical practitioners were interviewed exclusively on medicinal plant use in the management of chronic joint pains, in a pre-planned workshop.

RESULTS AND DISCUSSION

In this survey, a total of 37 plants belonging to 32 genera and 23 families were cited as being important for treatment of chronic joint pains. The most commonly cited plant species were Pavetta crassipes K. Schum, Strychnos henningsii Gilg., Carissa spinarum L., Fagaropsis hildebrandtii (Engl.) Milve-Redh. and Zanthoxylum chalybeum Engl. Acacia mellifera (Vahl) Benth., Amaranthus albus L., Balanites glabra Mildbr. & Schltr., Grewia fallax K. Schum., Lactuca capensis, Launaea cornuta (Oliv. & Hiern) O. Jeffrey, Lippia kituiensis Vatke, Pappea capensis Eckl. & Zeyh. and Pennisetum glaucum (L.) R. Br. are documented for the first time as being important in the management of chronic joint pains.

CONCLUSIONS

The findings of this study show that a variety of medicinal plants are used in the management of chronic joint pains and the main mode of administration is oral.

Traditional herbal antimalarial therapy in Kilifi district, Kenya

AIM OF STUDY

To identify plant species used by the traditional health practitioners (THPs) in treatment of malaria, carry out cytotoxicity and efficacy evaluation of the identified plants and to evaluate combination effects.

MATERIALS AND METHODS

Thirteen plants were selected through interviews with traditional healers. In vitro antiplasmodial testing was done by measuring ability of the test sample to inhibit the incorporation of radio-labelled hypoxanthine into the malaria parasite. The extracts were tested singly and then in combination using the standard fixed ratio analysis to evaluate synergism. In vivo bioassay was done in mice using Peter's 4-days suppressive test and cytotoxicity evaluated in vitro using Vero E6 cells.

RESULTS

Of the plants tested in vitro, 25% were highly active (IC(50)<10 μg/ml), 46% moderately active (IC(50) 10-50 μg/ml), 16% had weak activity of 50-100 μg/ml while 13% were not active IC(50) >100 μg/ml. Methanolic extracts of Azadirachta indica, Premna chrysoclada and Uvaria acuminata were the most active (IC(50)<10μg/ml) against both the chloroquine (CQ) sensitive (D6) and the CQ resistant (W2) Plasmodium falciparum clones. When tested in vivo in a mouse model, Azadirachta indica, Rhus natalensis and Grewia plagiophylla depicted the highest percent parasite clearance and chemo suppression of 89%, 82% and 78%, respectively. Evaluating effect of combining some of these extracts with one another against a multi-drug resistant Plasmodium falciparum (W2) clone revealed synergism among some combinations. The highest synergy was between Uvaria acuminata and Premna chrysoclada. The interaction between Grewia plagiophylla and Combretum illairii was largely antagonistic. Impressive cytotoxicity results were obtained with most of the plants tested revealing high selectivity indices an indication of enabling achievement of therapeutic doses at safe concentrations. Uvaria acuminata was, however, toxic to the cultured cells. Mild cytotoxicity was also observed in Hoslundia opposita and Lannea schweinfurthii (CC(50) 37 and 76 μg/ml, respectively).

CONCLUSIONS

This study identified plants with low IC(50) values, high percent chemo suppression and low cytotoxicity thus potential sources for novel antiplasmodial agents. The findings remotely justify use of combined medicinal plants in traditional medicine practices as synergy among some plant species was demonstrated.

Whole plant extracts versus single compounds for the treatment of malaria: synergy and positive interactions

Background

In traditional medicine whole plants or mixtures of plants are used rather than isolated compounds. There is evidence that crude plant extracts often have greater in vitro or/and in vivo antiplasmodial activity than isolated constituents at an equivalent dose. The aim of this paper is to review positive interactions between components of whole plant extracts, which may explain this.

Methods

Narrative review.

Results

There is evidence for several different types of positive interactions between different components of medicinal plants used in the treatment of malaria. Pharmacodynamic synergy has been demonstrated between the Cinchona alkaloids and between various plant extracts traditionally combined. Pharmacokinetic interactions occur, for example between constituents of Artemisia annua tea so that its artemisinin is more rapidly absorbed than the pure drug. Some plant extracts may have an immunomodulatory effect as well as a direct antiplasmodial effect. Several extracts contain multidrug resistance inhibitors, although none of these has been tested clinically in malaria. Some plant constituents are added mainly to attenuate the side-effects of others, for example ginger to prevent nausea.

Conclusions

More clinical research is needed on all types of interaction between plant constituents. This could include clinical trials of combinations of pure compounds (such as artemisinin + curcumin + piperine) and of combinations of herbal remedies (such as Artemisia annua leaves + Curcuma longa root + Piper nigum seeds). The former may enhance the activity of existing pharmaceutical preparations, and the latter may improve the effectiveness of existing herbal remedies for use in remote areas where modern drugs are unavailable.

Antiplasmodial activity of botanical extracts against Plasmodium falciparum

The absence of a vaccine and the rampant resistance to almost all antimalarial drugs have accentuated the urgent need for new antimalarial drugs and drug targets for both prophylaxis and chemotherapy. The aim of the study was to discover effective plant extracts against Plasmodium falciparum. In the present study, the hexane, chloroform, ethyl acetate, acetone, and methanol extracts of Citrus sinensis (peel), Leucas aspera, Ocimum sanctum, Phyllanthus acidus (leaf), Terminalia chebula (seed) were tested for their antimalarial activity against chloroquine (CQ)-sensitive (3D7) strain of P. falciparum which was cultured following the candle-jar method. Antimalarial evaluations of daily replacement of culture medium containing CQ and different plant crude extracts were performed on 96-well plates at 37°C for 24 and 48 h. Parasitemia was determined microscopically on thin-film Giemsa-stained preparations. Plant extracts were tested for their cytotoxicity using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay on human laryngeal cancer cell line (HEp-2) and normal cell line (Vero). Out of the 25 extracts tested, six showed good (IC(50) 4.76-22.76 μg/mL), 15 exhibited moderate (IC(50) 31.42-88.03 μg/mL), while four displayed mild (IC(50) > 100 μg/mL) antiplasmodial activity. The leaf ethyl acetate and methanol extracts of L. aspera; ethyl acetate, acetone, and methanol extracts of P. acidus; and seed acetone extract of T. chebula had good antiplasmodial activity (IC(50) = 7.81, 22.76, 9.37, 14.65, 12.68, and 4.76 μg/mL) with selectivity indices 5.43, 2.04, 4.88, 3.35, 3.42, and 9.97 for HEp-2 and >5.79, >2.20, >11.75, >3.41, >3.94, and >7.38 for Vero cells, respectively. These analyses have revealed for the first time that the components present in the solvent extracts of L. aspera, P. acidus, and T. chebula have antiplasmodial activity. The high antiplasmodial activity observed make these plants good candidates for isolation of anti-protozoal compounds which could serve as new lead structures for drug development.

Bioactive guanidine alkaloids from two Caribbean marine sponges

Seven new guanidine alkaloids (1-7) together with the known batzelladines A, F, H, and L, ptilomycalin A, and fromiamycalin were isolated from the Caribbean marine sponges Monanchora arbuscula and Clathria calla. Molecular structures were assigned on the basis of detailed analysis of 1D and 2D NMR spectra and mass spectrometry data, and bioactivities of the alkaloids were evaluated against human cancer cell lines and malaria protozoa.

Anti-plasmodial activity of the extracts of some Kenyan medicinal plants

ETHNOPHARMACOLOGICAL RELEVANCE

The spread of drug resistant Plasmodium falciparum strains necessitates search for alternative newer drugs for use against malaria. Medicinal plants used traditionally in preparation of herbal medicines for malaria are potential source of new anti-malarial drugs.

AIM OF THE STUDY

To identify the anti-plasmodial potential of twelve plants used in preparing herbal remedies for malaria in Kilifi and Tharaka districts of Kenya.

MATERIALS AND METHODS

Twelve plants used traditionally for anti-malarial therapy in Kilifi and Tharaka districts were extracted with water/methanol yielding twenty-three extracts. The extracts were tested against chloroquine sensitive (NF54) and resistant (ENT30) P. falciparum strains in vitro using (3)Hypoxanthine assay.

RESULTS

Seven (30%) extracts showed activity against P. falciparum with IC(50) values below 20 microg/ml. The remaining 16 extracts showed low or no activity. The most active extracts were from Zanthoxylum chalybeum (Rutaceae) with an IC(50) value of 3.65 microg/ml, Cyperus articulatus (Cyperaceae) with 4.84mug/ml, and Cissampelos pareira (Menispermaceae) with 5.85 microg/ml.

CONCLUSIONS

This study revealed plants, that are potential sources of anti-malarial compounds. Anti-plasmodial activities of extracts of T. simplicifolia, C. pareira, and C. articulatus are reported for the first time.

Investigating South African plants as a source of new antimalarial drugs

Based on the historical success of natural products as antimalarial drugs and the urgent need for new antimalarials, a number of South African medicinal plants have been evaluated for their antimalarial properties. This paper reviews the major studies conducted and their findings. Overall three ethnobotanical screening programmes have been conducted on South African plants while there have been a few studies adopting a more direct approach, where plants within a particular genus were screened for antiplasmodial activity. The paper also summarizes the bioactive molecules identified from selected plants having antiplasmodial activity. Overall the results of all studies conducted to date confirm the potential of South African medicinal plants in antimalarial drug discovery and identified a number of promising taxa and compounds for further investigation as plant-based antimalarial agents.

A broad review of commercially important southern African medicinal plants

AIMS OF THE STUDY

Commercially important indigenous medicinal plants of southern Africa are reviewed in the context of fundamental knowledge about their ethnobotany, phylogeny, genetics, taxonomy, biochemistry, chemical variation, reproductive biology and horticulture. The aim is to explore the rapidly increasing number of scientific publications and to investigate the need for further research.

MATERIALS AND METHODS

The Scopus (Elsevier) reference system was used to investigate trends in the number of scientific publications and patents in 38 medicinal plant species. Fifteen species of special commercial interest were chosen for more detailed reviews: Agathosma betulina, Aloe ferox, Artemisia afra, Aspalathus linearis, Cyclopia genistoides, Harpagophytum procumbens, Hoodia gordonii, Hypoxis hemerocallidea, Lippia javanica, Mesembryanthemum tortuosum, Pelargonium sidoides, Siphonochilus aethiopicus, Sutherlandia frutescens, Warburgia salutaris and Xysmalobium undulatum.

RESULTS

In recent years there has been an upsurge in research and development of new medicinal products and new medicinal crops, as is shown by a rapid increase in the number of scientific publications and patents. Despite the fact that an estimated 10% of the plant species of the world is found in southern Africa, only a few have been fully commercialized and basic scientific information is often not available.

CONCLUSIONS

The limited available information indicates that some of the plants display remarkable regional variation in morphological, genetic and chemical characters that should be more thoroughly investigated. Basic biological information is needed to guide the rapidly accelerating commercialization process, especially the selection of superior clones, the development of new cultivars and the standardization of raw materials.

The in vitro anti-plasmodial and in vivo anti-malarial efficacy of combinations of some medicinal plants used traditionally for treatment of malaria by the Meru community in Kenya

The use of herbal drugs as combinations has existed for centuries in several cultural systems. However, the safety and efficacy of such combinations have not been validated. In this study, the toxicity, anti-plasmodial and antimalarial efficacy of several herbal drug combinations were investigated. Lannea schweinfurthii, Turraea robusta and Sclerocarya birrea, used by traditional health practitioners in Meru community, were tested for in vitro anti-plasmodial and in vivo anti-malarial activity singly against Plasmodium falciparum and Plasmodium berghei, respectively. Methanolic extract of Turraea robusta was the most active against Plasmodium falciparum D6 strain. Aqueous extracts of Lannea schweinfurthii had the highest anti-plamodial activity followed by Turraea robusta and Sclerocarya birrea. D6 was more sensitive to the plant extracts than W2 strain. Lannea schweinfurthii extracts had the highest anti-malarial activity in mice followed by Turraea robusta and Sclerocarya birrea with the methanol extracts being more active than aqueous ones. Combinations of aqueous extracts of the three plants and two others (Boscia salicifolia and Rhus natalensis) previously shown to exhibit anti-plasmodial and anti-malarial activity singly were tested in mice. Marked synergy and additive interactions were observed when combinations of the drugs were assayed in vitro. Different combinations of Turraea robusta and Lannea schweinfurthii exhibited good in vitro synergistic interactions. Combinations of Boscia salicifolia and Sclerocarya birrea; Rhus natalensis and Turraea robusta; Rhus natalensis and Boscia salicifolia; Turraea robusta and Sclerocarya birrea; and Lannea schweinfurthii and Boscia salicifolia exhibited high malaria parasite suppression (chemo-suppression >90%) in vivo when tested in mice. The findings are a preliminary demonstration of the usefulness of combining several plants in herbal drugs, as a normal practice of traditional health practitioners.