In vitro antiplasmodial and antimicrobial potential of Tagetes erecta roots

Context: Among strategies to combat malaria, the search for newer antimalarial compounds is a priority. Traditionally, Tagetes erecta Linn. (Compositae) has been used for the treatment of various diseases and ailments including malaria.

Objective: Five successive extracts (petroleum ether, chloroform, ethyl acetate, methanol and aqueous) of the roots of T. erecta and a new bithienyl compound, 2-hydroxymethyl-non-3-ynoic acid 2-[2,2']-bithiophenyl-5-ethyl ester from the roots of the plant, were evaluated for in vitro antiplasmodial activity against chloroquine sensitive and resistant strains of Plasmodium falciparum. The extracts were also tested for in vitro antimicrobial activity against seven microbial strains.

Materials and methods: The antiplasmodial screening was carried out using the schizont maturation inhibition assay. Preliminary antimicrobial screening was carried out using the agar well assay followed by determination of minimum inhibitory concentration (MIC) using two-fold serial dilutions.

Results: Among all the extracts tested, the ethyl acetate fraction exhibited significant antiplasmodial efficacy with the 50% inhibitory concentrations (IC₅₀) of 0.02 and 0.07?mg/mL against the chloroquine sensitive and resistant strains of Plasmodium falciparum respectively. The new bithienyl compound also showed significant schizonticidal activity against both chloroquine sensitive and resistant strains of Plasmodium falciparum with the IC₅₀ values of 0.01 and 0.02?mg/mL. Additionally, all extracts exhibited significant antimicrobial activity against three Gram-positive and two Gram-negative bacterial and two fungal strains with MIC values ranging between 12.5-100 µg/mL.

Discussion: The new bithienyl compound was profoundly able to arrest the ring stages of the malarial parasites thereby exerting its antiplasmodial effect.

Conclusion: The observations provide support for the ethnobotanical use of the plant.     

Facile synthesis and in-vitro antimalarial activity of novel α-hydroxy hydrazonates

A series of previously unreported α‐hydroxy hydrazonates were synthesized and tested for their antimalarial properties. Structure optimization of the antiplasmodially active α‐hydroxy hydrazonate III furnished derivatives with strong in‐vitro antimalarial activity against 3D7 strains of Plasmodium falciparum with IC₅₀ values lower than 2.0 µM.     

Synthesis and antimalarial activity of ethylene glycol oligomeric ethers of artemisinin

Objectives The aim of this study was to synthesize a series of ethylene glycol ether derivatives of the antimalarial drug artemisinin, determine their values for selected physicochemical properties and evaluate their antimalarial activity in vitro against Plasmodium falciparum strains. Methods The ethers were synthesized in a one‐step process by coupling ethylene glycol moieties of various chain lengths to carbon C‐10 of artemisinin. The aqueous solubility and log D values were determined in phosphate buffered saline (pH 7.4). The derivatives were screened for antimalarial activity alongside artemether and chloroquine against chloroquine‐sensitive (D10) and moderately chloroquine‐resistant (Dd2) strains of P. falciparum. Key findings The aqueous solubility within each series increased as the ethylene glycol chain lengthened. The IC50 values revealed that all the derivatives were active against both D10 and Dd2 strains. All were less potent than artemether irrespective of the strain. However, they proved to be more potent than chloroquine against the resistant strain. Compound 8 , featuring three ethylene oxide units, was the most active of all the synthesized ethers. Conclusions The conjugation of dihydroartemisinin to ethylene glycol units of various chain lengths through etheral linkage led to water‐soluble derivatives. The strategy did not result in an increase of antimalarial activity compared with artemether. It is nevertheless a promising approach to further investigate and synthesize water‐soluble derivatives of artemisinin that may be more active than artemether by increasing the ethylene glycol chain length.     

Antiplasmodial activity of extracts of 25 cyanobacterial species from coastal regions of Tamil Nadu

Context: Marine cyanobacteria offer considerable potential to isolate new antimalarials to meet a pressing need of our times.

Objective: To explore the antiplasmodial properties of marine cyanobacteria.

Materials and methods: Cyanobacterial samples collected from the coastal regions of Tamil Nadu were identified using light microscopy, and the strains were cultivated in ASN-III medium. Organic extracts (0–100?µg?mL^?1) of 25 in vitro mass-cultivated cyanobacteria, prepared using methanol: chloroform mixture (1:1?v/v) were evaluated for their antiplasmodial activity against chloroquine-sensitive and -resistant strains of Plasmodium falciparum by fluorescence-based SYBR Green I assay where chloroquine was used as a control. To detect the toxic effects of cyanobacterial extracts against red blood cells, the invasion, maturation, and growth rate of malarial parasites in cyanobacterial extracts pre-treated versus untreated erythrocytes were quantified microscopically. Mammalian cell line (HeLa) was used to determine cyanobacterial extract toxicity using the MTT assay.

Results: The extracts of Lyngbya aestuarii Liebm. ex Gomont CNP 1005 (C12) Oscillatoria boryana BDU 91451 (C22) and Oscillatoria boryana Bory ex Gomont BDU 141071 (C18) showed promising antiplasmodial activity (IC₅₀?=?18, 18, and 51?μg?mL^?1 respectively) against Pf3D7. Pretreatment of red blood cells with IC₁₀₀ of C12, C18, and C22 (40, 100, and 40?µgmL^?1, respectively) did not significantly influence the invasion, maturation, and growth rate of malarial parasites in comparison with untreated RBC controls suggesting a lack of toxicity to host cells. MTT assay based IC₅₀ (>200?μg?mL^?1) of these extracts against HeLa cell line also indicates their high selectivity against the malaria parasite.

Discussion and conclusion: These exploratory studies suggest the possibilities of development of new antimalarial compounds from marine cyanobacteria.     

Antimalarial drug discovery: screening of Brazilian medicinal plants and purified compounds

Background: Malaria is the most important parasitic disease and its control depends on specific chemotherapy, now complicated by Plasmodium falciparum that has become resistant to most commonly available antimalarials. Treatment of the disease requires quinine or drug combinations of artemisinin derivatives and other antimalarials. Further drug resistance is expected. New active compounds need to be discovered. Objective/method: To find new antimalarials from medicinal and randomly collected plants, crude extracts are screened against P. falciparum in cultures and in malaria animal models, following bioassays of purified fractions, and cytotoxicity tests. Conclusion: For antimalarial research, screening medicinal plants is more efficient than screening randomly chosen plants. Biomonitored fractionation allows selection of new active molecules identified as potential antimalarials in multidisciplinary projects in Brazil; no new molecule is available for human testing. The advantages of projects based on ethnopharmacology are discussed.     

Patent Evaluation: Artemisinin Analogues as Potential Antimalarial Agents

Summary

Novelty: A process for synthesizing polyoxa heterocyles and, in particular, the antimalarial agent artemisinin and its analogues is disclosed. A new family of artemisinin analogues is disclosed.

Biology: In vitro IC₅₀ data for selected tricyclic artemisinin analogues in drug-resistant strains of P. falciparum are presented. For example, t-butylteperether has IC₅₀ values of 0.41 and 0.53 mg/ml against W-2 and D-6 clones, respectively.

Chemistry: The total synthesis by diastereo-selective silyation is described.     

Antimalarial,antiplasmodial and analgesic activities of root extract of Alchornea laxiflora

Context: Alchornea laxiflora (Benth.) Pax. &; Hoffman (Euphorbiaceae) root decoctions are traditionally used in the treatment of malaria and pain in Nigeria.

Objective: To assess the antimalarial, antiplasmodial and analgesic potentials of root extract and fractions against malarial infections and chemically-induced pains.

Material and methods: The root extract and fractions of Alchornea laxiflora were investigated for antimalarial activity against Plasmodium berghei infection in mice, antiplasmodial activity against chloroquine sensitive (Pf 3D7) and resistant (Pf INDO) strains of Plasmodium falciparum using SYBR green assay method and analgesic activity against experimentally-induced pain models. Acute toxicity study of the extract, cytotoxic activity against HeLa cells and GCMS analysis of the active fraction were carried out.

Results: The root extract (75–225?mg/kg, p.o.) with LD₅₀ of 748.33?mg/kg exerted significant (p?P. berghei infection in suppressive, prophylactive and curative tests. The root extract and fractions also exerted moderate activity against chloroquine sensitive (Pf 3D7) and resistant (Pf INDO) strains of P. falciparum with the ethyl acetate fraction exerting the highest activity with IC₅₀ value of 38.44?±?0.89?μg/mL (Pf 3D7) and 40.17?±?0.78?μg/mL (Pf INDO). The crude extract was not cytotoxic to HeLa cells with LC₅₀ value >100?μg/mL. The crude extract and ethyl acetate fraction exerted significant (p?Discussion and conclusions: These results suggest that the root extract/fractions of A. laxiflora possess antimalarial, antiplasmodial and analgesic potentials and these justify its use in ethnomedicine to treat malaria and pain.     

Antimalarial and antiplasmodial activity of husk extract and fractions of Zea mays

Context: Zea mays L. (Poacae) husk decoctions are traditionally used in the treatment of malaria by various tribes in Nigeria.

Objective: To assess the antimalarial and antiplasmodial potentials of the husk extract and fractions on malaria parasites using in vivo and in vitro models.

Materials and methods: The ethanol husk extract and fractions (187–748?mg/kg, p.o.) of Zea mays were investigated for antimalarial activity against Plasmodium berghei using rodent (mice) malaria models and in vitro activity against chloroquine sensitive (Pf 3D7) and resistant (Pf INDO) strains of Plasmodium falciparum using the SRBR green assay method. Median lethal dose and cytotoxic activities against HeLa and HEKS cells were also carried out. The GCMS analysis of the most active fraction was carried out.

Results: The husk extract (187–748?mg/kg, p.o.) with LD₅₀ of 1874.83?mg/kg was found to exert significant (p?P. berghei infection in suppressive, prophylactive and curative tests. The crude extract and fractions also exerted prominent activity against both chloroquine sensitive (Pf 3D7) and resistant (Pf INDO) strains of P. falciparum with the ethyl acetate fraction exerting the highest activity with IC₅₀ values of 9.31?±?0.46?μg/mL (Pf 3D7) and 3.69?±?0.66?μg/mL (Pf INDO). The crude extract and fractions were not cytotoxic to the two cell lines tested with IC₅₀ values of?>100?μg/mL against both HeLa and HEKS cell lines.

Discussion and conclusion: These results suggest that the husk extract/fractions of Zea mays possesses antimalarial and antiplasmodial activities and these justify its use in ethnomedicine to treat malaria infections.     

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.     

Novel approaches in antimalarial drug discovery

Introduction: The development of new antimalarial drugs remains of the utmost importance, since Plasmodium falciparum has developed resistance against nearly all chemotherapeutics in clinical use. In an effort to contain the resistance of P. falciparum against artemisinins and to further eradication efforts, studies are ongoing to identify novel and more efficacious approaches to develop antimalarials.

Areas covered: The authors review the classical and new approaches to antimalarial drug discovery, with a special emphasis on the various stages of the parasite's life cycle and the different Plasmodium species. The authors discuss the methodologies and strategies for early efficacy testing that aim to narrow down the portfolio of promising compounds.

Expert opinion: The increased efforts in the discovery and development of new antimalarial compounds have led to the recognition of new promising hits. However, there is still major roadblock of selecting the most promising compounds and then further testing them in early clinical trials, especially in the current restricted economy. Controlled human malaria infection has much potential for speeding-up the early development process of many drug candidates including those which target the pre-erythrocytic stages.     

Antimalarial Effect of 3‐Methoxy‐1,2‐Dioxetanes on the Erythrocytic Cycle of Plasmodium falciparum

The antimalarial activity of peroxides most likely originates from their interaction with iron(II) species located inside the malaria parasite, which forms destructive radical species through a Fenton‐like mechanism. This article reports the first evaluation of the in vitro antimalarial activity of three peroxides of the class 1,2‐dioxetanes against Plasmodium falciparum; the results reveal that the studied 3‐methoxy‐1,2‐dioxetanes display significant antimalarial activity, at a similar level as artemisinin and also that their reactivity toward iron(II) correlate linearly with their antimalarial activity.     

Synthesis and antimalarial activity of dihydroperoxides and tetraoxanes conjugated with bis(benzyl)acetone derivatives

Dihydroperoxides and tetraoxanes derived from symmetrically substituted bis(arylmethyl)acetones were synthesized in modest to good yields using several methods. Three of these compounds exhibit an important in vitro antimalarial activity (1.0 μm ≤ IC₅₀ ≤ 5.0 μm ) against blood forms of the human malaria parasite Plasmodium falciparum.     

In vivo antimalarial activities of glycoalkaloids isolated from Solanaceae plants

Context: Malaria is one of the most common and serious protozoan tropical diseases. Multi-drug resistance remains pervasive, necessitating the continuous development of new antimalarial agents.

Objective: Many glycosides, such as triterpenoid saponins, were shown to have antimalarial activity against Plasmodium falciparum in vitro. This study was to elucidate the ability of five glycoalkaloids against Plasmodium yoelii and develop new antimalarial lead compounds.

Materials and methods: Glycoalkaloids were isolated from three kinds of Solanaceae plants: chaconine and solanine were isolated from Solanum tuberosum L. sprouts, solamargine and solasonine from Solanum nigrum L. fruit, tomatine from Lycopersicon esculentum Mill. fruit. The five isolated glycoalkaloids were evaluated against Plasmodium yoelii 17XL in mice with 4-day parasitemia suppression test in different concentrations.

Results: Chaconine showed a dose-dependent suppression of malaria infection, ED50, 4.49?mg/kg; therapeutic index (TI), ≈9. At a dose of 7.50?mg/kg, the parasitemia suppressions of chaconine, tomatine, solamargine, solasonine and solanine were 71.38, 65.25, 64.89, 57.47 and 41.30%, respectively. At 3.75?mg/kg, the parasitemia suppression of chaconine was 42.66%, but the derivative, chaconine-6-O-sulfate, appeared to show no antimalarial activity. Simultaneous administration of chaconine and solanine in 1:1 did not show any synergistic effects.

Discussion and conclusion: The results showed that the glycoalkaloids with chacotriose (chaconine and solamargine) were more active than those with solatriose (solanine and solasonine). Chaconine was the most active among the five glycoalkaloids. We propose that the activity is dependent upon non-specific carbohydrate interactions. The 6-OH of chaconine is important for antimalarial activity.     

Antiprotozoal screening of the Cuban native plant Scutellaria havanensis

Context: Scutellaria havanensis Jacq. (Lamiaceae) is a native medicinal herb with a history of use in Cuba.

Objective: This study screens the antiprotozoal activity of S. havanensis.

Materials and methods: Chloroform and methanol extracts from leaves and stems were evaluated in vitro at doses between 0.015 and 200?μg/mL against protozoan parasites: Plasmodium berghei, Trichomonas vaginalis and Leishmania amazonensis. Chloroform and methanol extracts were characterized by GC/MS. Cytotoxicity against mouse peritoneal macrophages was tested in parallel.

Results: Scutellaria havanensis extracts exhibited IC₅₀ values between 7.7 and 32.2?μg/mL against trophozoites of P. berghei and T. vaginalis; while the extracts were inactive against L. amazonensis promastigotes. Trichomonicidal activity of methanol extract exhibited the best selectivity but chloroform extract showed the highest antiplasmodial, trichomonicidal and cytotoxic activity. The majority of compounds in the chloroform extract were hydroxy and/or methoxyflavones (77.96%), in particular, wogonin (48.27%). In methanol extract, wogonin (5.89%) was detected. Trichomonicidal effect of wogonin was moderate (IC_50?=_?56?μM) and unspecific with respect to macrophages (SI?=?2). On the contrary, antiplasmodial activity of wogonin were particularly active (IC_50?=_?15?μM) demonstrating a higher selectivity index (SI?=?7.4).

Conclusions: Wogonin is an active principle compound of the chloroform extract of S. havanensis against P. berghei and T. vaginalis trophozoites, whereas the methanol extract of S. havanensis should be investigated more deeply as a trichomonicide. Our findings suggest that wogonin is potentially useful for the development of antimalarial alternative treatments.     

Plants used to treat skin diseases in northern Maputaland,South Africa: antimicrobial activity and in vitro permeability studies

Context: Ethnobotanical claims of medicinal plants used in northern Maputaland are limited.

Objectives To establish scientific validity for a selection of the plants used in Maputaland to treat skin diseases.

Materials and methods: Aqueous and dichloromethane–methanol extracts were prepared from 37 plant species which were collected from four rural communities in Maputaland. Antimicrobial screening was performed on extracts against 12 dermatological relevant pathogens using the micro-titre plate dilution assay. Their combined effect was evaluated by determining the sum of the fractional inhibitory concentrations (ΣFICs). Chemical analysis was undertaken using reverse-phase high-performance liquid chromatography (RP-HPLC) and investigated in vitro across excised intact porcine skin using the ILC07 automated system.

Results: The organic extract of Garcinia livingstonei T. Anderson (Clusiaceae) was found to be the most antimicrobially active displaying an average broad-spectrum MIC value of 270?μg/mL. The combination of Sclerocarya birrea (A. Rich.) Hotsch. (Anacardaceae) with Syzygium cordatum Hochst. ex C. Krauss (Myrtaceae) displayed synergistic effects. The four antimicrobially active organic extracts were found to possess mainly anthraquinones, flavonoids, tannins and saponins. The organic extracts of Kigelia africana (Lam.) Benth. (Bignoniaceae) and S. cordatum were found to have more compounds capable of permeating intact skin after 10?min of exposure.

Conclusion: More than 80% of the organic extracts tested displayed a correlation between the antimicrobial efficacy and the reported traditional uses of the plants. Furthermore, the traditional use of topically applied plant preparations is validated as some compounds from the active plants are capable of permeating the skin in vitro.     

Antimalarial activity of newly synthesized chalcone derivatives in vitro

Twenty‐seven novel chalcone derivatives were synthesized using Claisen‐Schmidt condensation and their antimalarial activity against asexual blood stages of Plasmodium falciparum was determined. Antiplasmodial IC₅₀ (half‐maximal inhibitory concentration) activity of a compound against malaria parasites in vitro provides a good first screen for identifying the antimalarial potential of the compound. The most active compound was 1‐(4‐benzimidazol‐1‐yl‐phenyl)‐3‐(2, 4‐dimethoxy‐phenyl)‐propen‐1‐one with IC₅₀ of 1.1 μg/mL, while that of the natural phytochemical, licochalcone A is 1.43 μg/mL. The presence of methoxy groups at position 2 and 4 in chalcone derivatives appeared to be favorable for antimalarial activity as compared to other methoxy‐substituted chalcones. Furthermore, 3, 4, 5‐trimethoxy groups on chalcone derivative probably cause steric hindrance in binding to the active site of cysteine protease enzyme, explaining the relative lower inhibitory activity.     

Cytotoxic and antioxidant activities of selected Lamiales species from Mexico

Context: Methanol extracts obtained from eight species belonging to four families of the Lamiales order native to Mexico were investigated for biological action.

Objective: Cytotoxicity and antioxidant activity of methanol extracts have been investigated.

Materials and methods: Cytotoxic activity was evaluated by the sulphorhodamine B protein staining assay against KB (nasopharyngeal), HEp-2 (larynx), HF-6 (colon), MCF7 (breast), PC-3 (prostate), and Ca Ski (cervix) carcinoma cell lines. To analyze the antioxidant activity, common stable radicals chromogens, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS^·+) and DPPH (1,1-diphenyl-2-picrylhydrazyl) were used. The ferric reducing antioxidant power (FRAP) and the total phenolic content of the samples were also determined.

Results: Some of the extracts, such as Limosella aquatica L. (Scrophulariaceae), Mimulus glabratus Kunth. (Phrymaceae), Pedicularis mexicana Zucc. ex Benth. (Orobanchaceae), and Penstemon campanulatus (Cav.) Willd. (Plantaginaceae) displayed remarkably selective cytotoxic activity. However, the extract from Veronica americana (Raf.) Schwein (Plantaginaceae) showed the highest activity with IC₅₀ values of 1.46 and 0.169 μg/mL on PC-3 and HF-6 cells, respectively. With the exception of M. glabratus, all the extracts showed different degrees of antioxidant activity with IC₅₀ values from 0.89 up to 1.8 in the ABTS assay; from 0.49 up to 1.25?mg/mL in the DPPH assay and with the FRAP evaluation, 36 to 68 equivalents in mM of FeSO₄. V. americana also showed the highest antoxidant activity with IC₅₀ values from 0.491 and 0.892?mg/mL, on DPPH and ABTS assays, respectively.

Discussion and conclusion: These findings demonstrated that the species studied have great potential cytotoxic and antioxidant activity.     

Anti-Streptococcus mutans efficacy of Thai herbal formula used as a remedy for dental caries

Context: Traditional knowledge of herbal remedies plays an important role in the search for more effective alternative treatment of a variety of disorders. The ethnobotanical surveys in southern Thailand have revealed that 35 Thai herbal formulas have been used by Thai traditional healers against dental caries. However, the scientific evaluation to confirm their rational uses is scarce.

Objective: To test in vitro anti-Streptococcus mutans activity of Thai herbal formulas used against dental caries (THF-DC).

Materials and methods: Ethanol extracts of Thai herbal formulas were evaluated for antibacterial activity against S. mutans. Agar disc diffusion was employed as a preliminary screening assay, followed by broth microdilution assay to assess minimum inhibitory concentration (MIC). Furthermore, medicinal plants contained in the most active THF-DC were investigated for their phytochemicals.

Results: Eleven THF-DC extracts exhibited clear inhibition zones of 7.0–22.5?mm against S. mutans. Subsequent determination of their MIC revealed that the formula containing Albizia myriophylla Benth. (Leguminosae), Alpinia galanga (L.) Willd. (Zingiberaceae), Avicennia marina (Forssk.) Vierh. (Acanthaceae), and Ocimum sanctum L. (Lamiaceae) was the most active, with MIC at 250 µg/mL. Among these medicinal plants, A. myriophylla gave the strongest activity with MIC at 3.9 µg/mL, followed by A. marina with MIC at 62.5 µg/mL. Various classes of bioactive phytochemicals including tannins, flavonoids, alkaloids, and terpenoids were found in these extracts.

Conclusion: Anti-S. mutans activity of THF-DC extracts was established. Further investigations may be required for the isolation and chemical characterization of the active ingredients in A. myriophylla.     

Evaluation of antidiarrheal and in vitro antiprotozoal activities of extracts of leaves of Alocasia indica

Context: Alocasia indica Schott (Araceae) is used in several regions of India, especially in rural communities, by traditional medicine practitioners to treat diarrhea. However, no scientific data are available to justify the traditional potentials of the plant species in gastrointestinal disorders.

Objective: To evaluate the antidiarrheal and in vitro antiprotozoal activities of extracts of leaves of Alocasia indica using various pharmacological models.

Materials and methods: In vitro antidiarrheal activity of aqueous and ethanol extracts of Alocasia indica was evaluated against Escherichia coli, Salmonella typhimurium, Shigella flexneri and Staphylococcus aureus by agar well diffusion method. In vivo antidiarrheal activity of the extracts was studied against recinolic acid-induced diarrhea and magnesium sulfate-induced diarrhea. The effect of the extracts on normal intestinal transit, recinolic acid-induced intestinal transit, recinolic acid-induced intestinal fluid accumulation (enteropooling) and gastric emptying was assessed. In vitro antiprotozoal activity of aqueous and ethanol extracts of Alocasia indica was studied against Entamoeba histolytica and Giardia intestinalis.

Results: The aqueous and ethanol extracts exhibited significant in vitro antidiarrheal activity compared to the standard drug ciprofloxacine (10 µg/mL). The plant extracts showed significant (P <0.05) and dose-dependent antidiarrheal activity comparable to that of the reference drug, loperamide (10?mg/kg). The plant extracts exhibited significant in vitro antiprotozoal activity against both protozoa compared to the standard amebicidal and giardicidal drugs, metronidazole and emetine.

Discussion and conclusion: The results showed that the extracts of Alocasia indica have significant antidiarrheal and in vitro antiprotozoal activities which support its use in traditional herbal medicine practice.     

青蒿素类似物的研究——Ⅰ、还原青蒿素的醚类、羧酸酯类及碳酸酯类衍生物的合成

青蒿素是当前治疗抗恶性疟疾的首选药物。为克服它的近期复燃率高的缺点,我们以还原青蒿素为中间体,在酸或碱的催化下与各种醇、羧酸酐或酰氯、氯甲酸酯反应,合成了它的醚类,羧酸酯类和碳酸酯类衍生物47个。经鼠疟(P.berghei)抗氯喹原虫株筛选,发现其中大多数化合物的抗疟效果超过青蒿素;以SD₉₀)作比较标准,超过青蒿素十倍左右的化合物有12个。