Pregnane glycoside from Huernia saudi-arabica as latent schistosomicidal mediator.

Development of a novel agent for control of schistosomiasis is a mandate. In-vitro anti-schistosomal activity of the aerial parts of Huernia saudi-arabica were examined. Chromatographic investigations of the ethanol extract (EE) were afforded three compounds. Pregnane glycoside (CI) 12-ß-p-hydroxy-benzoyl-20-O-acetyl-boucerin-3-O-ß-D-glucopyranosyl-(1→4)-ß-D-cymaropyranosyl-(1→4)-ß-D-cymaropyranoside, in addition to two flavonoids (CII) luteolin-4'-O-ß-D-neohesperidoside and (CIII)quercetin-3-rutinoside were recognized via spectral analysis. The schistosomicidal effects were evaluated using scanning electron microscope (SEM). In-vitro bioassays on the viability (mobility, morphological changes and mortality) of Schistosoma mansoni adults, cercariae, miracidia and eggs at different concentrations 2.5, 5, 12.5, 25 and 50 µg/ml of EE and 2.6, 5.2, 13, 26 and 52 µM of CI in incubation times 1,2,4,6,12hrs were carried out. EE and CI evidenced in-vitro anti-schistosomal activity with a dose and incubation time-dependent fashion. The effect of EE and CI was evident by the topography damage showed by SEM. EE proved moderate in-vitro cytotoxicity with IC50 of 8.48 µg/ml.

A novel cell-free method to culture Schistosoma mansoni from cercariae to juvenile worm stages for in vitro drug testing.

BACKGROUND: The arsenal in anthelminthic treatment against schistosomiasis is limited and relies almost exclusively on a single drug, praziquantel (PZQ). Thus, resistance to PZQ could constitute a major threat. Even though PZQ is potent in killing adult worms, its activity against earlier stages is limited. Current in vitro drug screening strategies depend on newly transformed schistosomula (NTS) for initial hit identification, thereby limiting sensitivity to new compounds predominantly active in later developmental stages. Therefore, the aim of this study was to establish a highly standardized, straightforward and reliable culture method to generate and maintain advanced larval stages in vitro. We present here how this method can be a valuable tool to test drug efficacy at each intermediate larval stage, reducing the reliance on animal use (3Rs). METHODOLOGY/PRINCIPAL FINDINGS: Cercariae were mechanically transformed into skin-stage (SkS) schistosomula and successfully cultured for up to four weeks with no loss in viability in a commercially available medium. Under these serum- and cell-free conditions, development halted at the lung-stage (LuS). However, the addition of human serum (HSe) propelled further development into liver stage (LiS) worms within eight weeks. Skin and lung stages, as well as LiS, were submitted to 96-well drug screening assays using known anti-schistosomal compounds such as PZQ, oxamniquine (OXM), mefloquine (MFQ) and artemether (ART). Our findings showed stage-dependent differences in larval susceptibility to these compounds. CONCLUSION: With this robust and highly standardized in vitro assay, important developmental stages of S. mansoni up to LiS worms can be generated and maintained over prolonged periods of time. The phenotype of LiS worms, when exposed to reference drugs, was comparable to most previously published works for ex vivo harvested adult worms. Therefore, this in vitro assay can help reduce reliance on animal experiments in search for new anti-schistosomal drugs.

Schistosoma mansoni: Antiparasitic effects of orally administered Nigella sativa oil and/or Chroococcus turgidus extract.

Schistosoma mansoni is one of the parasites causing schistosomiasis, a disease which threatens millions of people all over the world. Traditional chemical drugs are not fully effective against schistosomaisis due to the evolving drug resistant worm strains, so exploring new remedies derived from natural products is a good way to fight schistosomiasis. In the present investigation two natural products, Nigella sativa oil and Chroococcus turgidus extract were used separately or in a combination to explore their effect on S. mansoni. The infected mice treated with Chroococcus turgidus extract or/and sativa seed oil showed a significant decrease in the total worm burden. The total number of deposited eggs by females of S. mansoni was significantly decreased in the liver of mice treated with Chroococcus turgidus extract or/and sativa seed oil. However, in the intestine, the number of eggs was significantly reduced in mice treated with algal extract and those treated with both algal extract and oil. Fecundity of female S. mansoni showed a significant decrease from mice treated with algal extract or/and sativa seed oil. According to SEM investigations the tegmental surface, oral and ventral suckers of worms also showed considerable changes; as the tubercles lost their spines, some are swollen and torn out. The suckers become edematous and enlarged while the tegmental surface is damaged due to the treatment with Chroococcus turgidus extract or/and sativa seed oil. In conclusion, the Nigella sativa oil and Chroococcus turgidus extract are promising natural compounds that can be used in fighting schistosomiasis.

In vitro evaluation of the schistosomicidal effect of the extracts, fractions and major 3-hydroxy-2,6-dialkyl-substituted piperidine alkaloids from the flowers of Senna spectabilis (Fabaceae).

In this work, we present the in vitro schistosomicidal activity evaluation of the most active dichloromethane fraction (FDm) (ED50=83.5µg/mL) and of a mixture of the major alkaloids ((-)-cassine/(-)-spectaline, C/E) (ED50=37.4µg/mL) from the flowers of Senna spectabilis against adult worms and cercariae. We also demonstrate other toxic effects including paralysis of the adult worms, inhibition of the secretory activity, tegument lesions and cercaricidal activity. In the association test of Praziquantel (PZQ)-C/E, we observed up to 80% mortality of Schistosoma mansoni in comparison to PZQ monotherapy. Due to the diversity of the toxic effects, the schistosomicidal activity of C/E is likely a result of a multitarget mechanism involving the tegument, secretory system and neuromotor action.

Schistosomicidal activity and docking of Schistosoma mansoni ATPDase 1 with licoflavone B isolated from Glycyrrhiza inflata (Fabaceae).

Schistosomiasis is one of the world's major public health problems, and its treatment is widely dependent on praziquantel (PZQ), the only available drug. Schistosoma mansoni ATP diphosphohydrolases are ecto-enzymes localized on the external tegumental surface of S. mansoni and considered an important target for action of new drugs. In this work, the in vitro schistosomicidal activity of the crude extract of Glycyrrhiza inflata roots (GI) and its isolated compounds echinatin, licoflavone A and licoflavone B were evaluated against S. mansoni adult worms. Results showed that GI (200 µg/mL) was active against adult schistosomes, causing 100% mortality after 24 h of incubation. Chromatographic fractionation of GI led to isolation of echinatin, licoflavone A and licoflavone B. Licoflavone B (25-100 µM) caused 100% mortality, tegumental alterations, and reduction of oviposition and motor activity of all adult worms, without affecting mammalian Vero cells. Confocal laser scanning microscopy showed tegumental morphological alterations and changes on the numbers of tubercles of S. mansoni worms in a dose-dependent manner after incubation with licoflavone B. Licoflavone B also showed high S. mansoni ATPase (IC50 of 23.78 µM) and ADPase (IC50 of 31.50 µM) inhibitory activities. Docking studies predicted different interactions between licoflavone B and S. mansoni ATPDase 1, corroborating with the in vitro inhibitory activity. This report demonstrated the first evidence for the schistosomicidal activity of licoflavone B and suggests that its mechanism of action involve the inhibition of S. mansoni ATP diphosphohydrolases.

Potent Schistosomicidal Constituents from Garcinia brasiliensis.

Praziquantel is the drug of choice for the treatment of schistosomiasis. However, several strains of Schistosoma mansoni are resistant to praziquantel, making it necessary to discover new drugs that might be used for its treatment. With this in mind, the properties of a schistosomicidal ethanolic extract of Garcinia brasiliensis Mart. epicarp, the fractions obtained by partitioning this extract, including the hexane fractions, ethyl acetate fraction, and the aqueous fraction, and the isolated compounds 7-epiclusianone, a major component from these fractions, and fukugetin were tested in vitro on adult worms of S. mansoni. Mortality, damage to membranes, and excretory system activity were observed at 100.0, 50.0, 75.0, and 14.0 µg/mL for the ethanolic extract of G. brasiliensis Mart. epicarp, its hexane fractions, the ethyl acetate fraction, and 7-epiclusianone, respectively. For 7-epiclusianone, these data were confirmed by fluorescent probe Hoechst 33 258 and resorufin. Additionally, the biocidal effect of 7-epiclusianone was even higher than the hexane fractions. Moreover, an inhibitory effect of 7-epiclusianone on the egg laying of female adult S. mansoni worms was observed in cercariae and schistossomula. Thus, 7-epiclusianone is a promising schistosomicidal compound; however, more studies are needed to elucidate its mechanism of toxicity and to evaluate the in vivo activity of this compound.

A new schistosomicidal and antioxidative phenylpropanoid from Astragalus englerianus.

A new phenylpropanoid, (E)-2,3,4-trimethoxy-5-(1-propenyl)phenol (1), along with five known aromatic compounds (2-6), was isolated from the methanol extract of roots of Astragalus englerianus. Their structures were elucidated based on the analyses of extensive spectroscopic data and comparison of their physicochemical properties. Compounds 1 and 2 were evaluated schistosomicidal activities, and all the isolated compounds were tested for their antioxidant activities in vitro. Compound 1 showed significant schistosomicidal activity with worm mortality rates of 66.7% and 83.3% within 12 and 24 h in a drug-containing (1.16 mM) RPMI 1640 medium, respectively. Also, compound 1 exhibited excellent antioxidant activity (2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl free radical-scavenging capability) with an IC50 value of 81.3 ± 1.3 µM.

Molluscicidal and antischistosomal activities of methanol extracts and isolated compounds from Eucalyptus globulus and Melaleuca styphelioides.

CONTEXT: Schistosomiasis is a parasitic disease that results in severe organ damage. Snail control is the best measure to control schistosomiasis. Plant-derived molluscicides have gained increasing attention for the control of schistosomiasis because they have low toxicity towards non-target organisms. Tannins are particularly suitable for snail control because they are less toxic than saponins to non-target organisms. OBJECTIVE: To identify the most toxic components of two plants belonging to the family Myrtaceae, namely Eucalyptus globulus Labill. and Melaleuca styphelioides Sm against the different developmental stages of Schistosoma mansoni and its snail host. MATERIALS AND METHODS: The 80% MeOH leaf extracts of the tested plants and their isolated compounds were screened for their molluscicidal activity (expressed as LC50 and LC90 after 24 h exposure) against the snail Biomphalaria alexandrina. The anti-schistosomal activity of the tested samples was determined at 20 ppm (after 1 or 2 h exposure) against the different developmental stages of S. mansoni, including the miracidia, cercariae and worms. Biochemical parameters were measured to determine the toxicity mechanisms of the treated snails. The structures of the isolated compounds were elucidated based on NMR, UV and HRESI-MS/MS data. RESULTS: Potent molluscicidal activity was observed for the ellagitannin dimer eucalbanin B (12), with an LC50 value of 55 ppm. Treatment of the snails with the LC25 of eucalbanin B (30.8 ppm) resulted in a significant decrease in the protein level by 22.7% and 25.8% in the snail tissues and hemolymph, respectively. The decreased protein content was attributed to destruction of the snail tissue and impairment in protein synthesis under stress conditions of intoxication with eucalbanin B. Alterations in the activities of the transaminases and phosphatases in the treated snails indicated destruction and intoxication of the snail tissues. A significant increase in the levels of the transaminases alanine aminotransferase (ALT) (57.8%) and aspartate aminotransferase (AST) (113.2%) in the snail hemolymph and a significant decrease in their tissue levels to 7.4 and 48.6%, respectively, were attributed to their release from the damaged tissue into the hemolymph. Alkaline phosphatase (ALP) was significantly increased by 38.5 and 181.4% in the hemolymph and tissues, respectively. Acid phosphatase (ACP) was also significantly increased by 48.4 and 21.2% in the hemolymph and tissues, respectively. The 80% MeOH extract of E. globulus together with mallophenol B (3), 2,2,8-trimethyl-6-formyl-chrom-3-ene-7-O-ß-d-glucopyranoside (5) and benzyl alcohol 7-O-(3',4',6'-tri-O-galloyl)-ß-d-glucopyranoside (10) exhibited miracidicidal activity with almost 100% toxicity at 20 ppm for the three compounds and 80% toxicity for the extract. Moreover, E. globulus extract showed cercaricidal and schistosomicidal activity with 100 and 40% mortality, respectively. CONCLUSION: E. globulus is a potential source for biocidal compounds against S. mansoni and its snail host. This is the first study to test the biocidal activity of the isolated compounds.

A penta-substituted pyridine alkaloid from the rhizome of Jatropha elliptica (Pohl) Muell. Arg. is active against Schistosoma mansoni and Biomphalaria glabrata.

Jatropha elliptica is a shrub distributed throughout the north and west of Brazil and reputedly possesses a wide range of therapeutical properties. The roots of this plant possess molluscicidal activity and contain terpenoids, coumarin, lignoid, steroids and alkaloid. In the present study, we assessed the schistosomicidal, miracicidal and cercaricidal activities (against Schistosoma mansoni) and molluscicidal activities (against adults and egg masses of Biomphalaria glabrata) of the alkaloid diethyl 4-phenyl-2,6-dimethyl-3,5-pyridinedicarboxylate, isolated from the ethanol extract of the rhizome of J. elliptica, have been determined. The alkaloid was 100% lethal to adult schistosomes within 4 days at a concentration of 50 µg/mL. Alterations were observed in the schistosome tegument occasioned by treatment with the alkaloid, such as formation of vesicles and vacuolisation. The extent of tegumental damage of the worm was proportional to the time of incubation and to the concentration of compound. The alkaloid also exhibited a potent cercaricidal activity (LC100 = 2 µg/mL); it was totally ineffective against miracicidal forms of the parasite. Moreover, the alkaloid presented strong activity against adult snails (LC90 = 36.43 µg/mL) but was inactive against their egg masses. It is observed then the potential of this compound for the development of new therapies for the treatment of schistosomiasis.

Industrial Scale Isolation, Structural and Spectroscopic Characterization of Epiisopiloturine from Pilocarpus microphyllus Stapf Leaves: A Promising Alkaloid against Schistosomiasis.

This paper presents an industrial scale process for extraction, purification, and isolation of epiisopiloturine (EPI) (2(3H)-Furanone,dihydro-3-(hydroxyphenylmethyl)-4-[(1-methyl-1H-imidazol-4-yl)methyl]-, [3S-[3a(R*),4b]]), which is an alkaloid from jaborandi leaves (Pilocarpus microphyllus Stapf). Additionally for the first time a set of structural and spectroscopic techniques were used to characterize this alkaloid. EPI has shown schistomicidal activity against adults and young forms, as well as the reduction of the egg laying adult worms and low toxicity to mammalian cells (in vitro). At first, the extraction of EPI was done with toluene and methylene chloride to obtain a solution that was alkalinized with ammonium carbonate. The remaining solution was treated in sequence by acidification, filtration and alkalinization. These industrial procedures are necessary in order to remove impurities and subsequent application of the high performance liquid chromatography (HPLC). The HPLC was employed also to remove other alkaloids, to obtain EPI purity higher than 98%. The viability of the method was confirmed through HPLC and electrospray mass spectrometry, that yielded a pseudo molecular ion of m/z equal to 287.1 Da. EPI structure was characterized by single crystal X-ray diffraction (XRD), (1)H and (13)C nuclear magnetic resonance (NMR) in deuterated methanol/chloroform solution, vibrational spectroscopy and mass coupled thermal analyses. EPI molecule presents a parallel alignment of the benzene and the methyl imidazol ring separated by an interplanar spacing of 3.758 Å indicating a π-π bond interaction. The imidazole alkaloid melts at 225°C and decomposes above 230°C under air. EPI structure was used in theoretical Density Functional Theory calculations, considering the single crystal XRD data in order to simulate the NMR, infrared and Raman spectra of the molecule, and performs the signals attribution.

Antioxidant and schistosomicidal effect of Allium sativum and Allium cepa against Schistosoma mansoni different stages.

OBJECTIVE: The schistosomicidal properties of garlic (Allium sativum) and onion (Allium cepa) powder were tested in vitro against Schistosoma mansoni miracidia, schistosomula, cercaria and adult worms. Results indicate their strong biocidal effects against all stages of the parasite and also show scavenging inhibitory effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO). MATERIALS AND METHODS: In the present work, the in vivo effects of A. sativum and A. cepa on lipid peroxide and some antioxidant enzymes; thioredoxin reductase (TrxR), sorbitol dehydrogenase (SDH), superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) (as they have a crucial role in host protection against invading parasite) were also studied. RESULTS: The data demonstrate that, there was a significant inhibition in SOD, CAT, GR, TrxR and SDH in infected liver while, significant elevation was detected in lipid peroxide as compared to the normal control. The current resultS clearly revealed that, the used both edible plants enhance the host antioxidant system indicated by lowering in lipid peroxide and stimulation of SOD, CAT, GR, TrxR and SDH enzyme levels. CONCLUSIONS: Enhancement of such enzymes using A. sativum and A. cepa could in turn render the parasite vulnerable to damage by the host and may play a role in the antischistosomal potency of the used food ingredients.

Antischistosomal effect of holothurin extracted from some Egyptian sea cucumbers.

CONTEXT: Holothuria polii (H. polii) Linnaeus (Holothuriidae), Actinopyga mauritiana (A. mauritiana) Quoy & Gaimard (Holothuriidae) and Bohadschia vitiensis (B. vitiensis) Semper (Holothuriidae) are sea cucumbers inhabiting the coasts of Egypt. Their tegument and the cuvierian gland contained a substance called holothurin that was used in traditional medicine. These three species are abundant in the Egyptian coast, however there are no reports about their efficacy as antiparasitic agent. OBJECTIVE: The antischistosomal effect of the holothurin extracted from the three species of sea cucumber is investigated. MATERIALS AND METHODS: The ethanol extract was made from the tegument of both H. polii and A. mauritiana while it was made from the cuvierian gland of B. vitiensis. The body wall (or cuvierian gland) of the sea cucumber was blended with 95% ethanol in a volume = 4 × tissue weight. Extraction was done at room temperature for one day then filtered. The ethanol was removed by evaporation using Rotavapour (BÜCHI 461 water bath REIII) at 40°C. Later the aqueous residue was placed in a vacuum oven at 20°C for about 48 h to remove water. The resulting dried mass was then stored at -4°C until use. The percentage yield and the LD50 were calculated for each extract. Each extract was administered orally to Shistosoma mansoni infected mice in acute and chronic phases of infection. The dose of one-tenth of LD50 of each extract was administrated to mice (5.4, 62.2, and 10 mg/kg body weight/mouse for H. polii extract (HPE), A. mauritiana extract (AME), and cuvierian gland of B. vitiensis, respectively) for 24 h. The effects of each extract on the worm burden and total egg count was studied. The effects of each extract on the worm tegument using scanning electron microscope (SEM) were investigated in vivo and in vitro. RESULTS: The percentage yield of cuvierian gland extract (CGE) was higher (70%) than the tegument AME (33.4%) and HPE (9.3%). The 24 h LD50 of investigated sea cucumber ethanol extracts were 54.46, 627, and 100 mg/kg body weight/mouse for HPE, AME, and CGE. Oral administration of HPE caused decrease in male and female worm burden of 30-day infected mice to reach 60 and 90%, respectively. HPE decreased the egg count significantly in those mice with 30-day (1.75 egg counts/g tissue, p < 0.05) and 45-day (3.25 egg counts/g tissue, p < 0.05) infections. SEM studies of recovered worms from treated mice with all extracts showed different tegumental changes like formation of blebs, wrinkling, formation of numerous pores, and rupturing of some tubercles. These effects were more pronounced in those worms treated in vitro represented by severe shrinkage of the tegument, deformation of spines, rupturing, and collapsing of tubercles. DISCUSSION AND CONCLUSION: Results support the hypothesis that holothurin is a promising antischistosomal agent.

Schistosomicidal evaluation of flavonoids from two species of Styrax against Schistosoma mansoni adult worms.

CONTEXT: Schistosomiasis is a major health problem worldwide. Thus, the search for new schistosomicidal agents from natural sources can provide prototypes for drug discovery. OBJECTIVE: The present study investigated the chemical composition of the EtOAc fractions of Styrax pohlii Pohl (Styracaceae) (EF-SP) aerial parts and S. camporum A. DC. leaves (EF-SC), as well as schistosomicidal activities against Schistosoma mansoni adult worms, which have not yet been studied. MATERIALS AND METHODS: The crude ethanol extracts of S. camporum leaves and S. pohlii aerial parts (EE-SC and EE-SP) were partitioned with n-hexane, EtOAc, and n-BuOH. The EtOAc fractions were purified by preparative HPLC. The crude extracts, EtOAc fractions and pure compounds were tested against S. mansoni adult worms in vitro. RESULTS: The purification procedure resulted in the isolation of kaempferol-3-O-(2'',4''-di-O-(E)-p-coumaroyl)-ß-d-glucopyranoside (1), kaempferol-3-O-(2'',6''-di-O-(E)-p-coumaroyl)-ß-d-glucopyranoside (2), quercetin (3), and kaempferol (4). The bioassay results indicated that EE-SC, EF-SC, EF-SP, and compounds 2 and 4 are able to separate coupled S. mansoni adult worms. Additionally, EE-SC, EF-SP, and compound 4 killed the adult schistosomes in vitro at 100 µg/mL and 100 µM. DISCUSSION AND CONCLUSION: This is the first time that the presence of compounds 1-2 in S. pohlii and 3-4 in S. camporum has been reported. Additionally, biological results indicated that S. pohlii and S. camporum have great potential as a source of active compounds.

Contribution to in vitro screening of Egyptian plants for schistosomicidal activity.

CONTEXT: This study is a continuation of our previous work in which a bioassay screening of 346 methanol extracts from 281 Egyptian plant species was carried out for in vitro schistosomicidal activity. OBJECTIVE: Another 309 methanol extracts from 278 plant species were subjected to the bioassay screening using the same technique on viable Schistosoma mansoni Sambon (Schistosomatidae) mature worms in specialized culture medium (Roswell Park Memorial Institute medium 1640) in a trial to discover a source for a schistosomiasis drug from Egyptian flora. MATERIAL AND METHODS: The methanol plant extracts were tested in vitro against viable S. mansoni mature worms in culture medium. Viability of worms was examined after exposure to 100 µg/ml of the extract in the medium for 24 h. Negative (dimethyl sulfoxide) and positive (praziquantel) controls were simultaneously used. Extracts showing schistosomicidal activity were further subjected to determination of their (Lethal concentration) LC50 and LC90 values. RESULTS: Confirmed in vitro antischistosomal activity was found in 42 extracts. Of these, 14 plant species possessed considerably high antischistosomal activity (LC50 ≤ 15 µg/ml), viz. Callistemon viminalis (Soland. Ex Gaertn) Cheel, C. rigidus R.Br., C. speciosus (Sims.) DC, C. citrinus Stapf, Eucalyptus citriodora Hook, E. rostrata Dehnh., Eugenia edulis Vell, E. javanica Lam syn. Syzygium samarangense (Blume) Merril, Melaleuca leucadendron (L.) L., M. stypheloides Sm. (all belong to Myrtaceae), Cryptostegia grandiflora R.Br. (Asclepiadaceae), Zilla spinosa (L.) Prantl (Cruciferae), Ficus trijuja L. (Moraceae) and Fagonia mollis Delile (Zygophylacae). DISCUSSION AND CONCLUSION: These species may represent additional natural sources of bioactive material that deserve further investigation for drug discovery against schistosomiasis.

Chemical composition and in vitro schistosomicidal activity of the essential oil of Plectranthus neochilus grown in Southeast Brazil.

The chemical composition and the in vitro schistosomicidal effects of the essential oil of Plectranthus neochilus (PN-EO) grown in Southeast Brazil was studied. ß-Caryophyllene (1; 28.23%), α-thujene (2; 12.22%), α-pinene (3; 12.63%), ß-pinene (4; 6.19%), germacrene D (5; 5.36%), and caryophyllene oxide (6; 5.37%) were the major essential oil constituents. This chemical composition differed from that previously reported for specimens harvested in Africa. Concerning the in vitro schistosomicidal activity against adult Schistosoma mansoni worms, PN-EO was considered to be active, but less effective than the positive control praziquantel (PZQ) in terms of separation of coupled pairs, mortality, decrease in the motor activity, and tegumental alterations. However, PN-EO caused an interesting dose-dependent reduction in the number and the percentage of developed S. mansoni eggs. These results suggest that PN-EO might be very promising for the development of new schistosomicidal agents.

Isolation and identification of some steroidal glycosides of Furcraea selloa.

The antischistosomal impact of different extracts of the leaves of Furcraea selloa C. Koch (Family Agavaceae) were screened against adult Schistosoma mansoni worms in vitro using well established culture media. The methanol extract of the plant showed the highest activity as S. mansoni worms recorded 100% mortality at 50 microg/ml after 24 h (EC50 = 29.78 and 29.41 microg/ml for female and male worm respectively). Owing to the high potency of the crude butanolic extract (100% mortality at 20 microg/ ml; EC50 = 10.42 and 8.94 microg/ml for female and male worm respectively) obtained from the methanolic extract, it was submitted to chromatographic separation and isolation using silica gel and Sephadex columns as well as preparative thin layer chromatography. Three steroidal glycosides (saponins) (I-III) were isolated and their structures were elucidated using some spectroscopic and chemical methods. The structure of the three compounds was formulated as 6-O-beta-glucopyranosyl-(1-->4)-beta-D-glucopyranoside chlorogenin (I), 3-O-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranoside crestagenin (II) and 3-O-beta-D-glucopyranosyl-(1-->3)-beta-D-glucopyranosyl-(1-->3)-beta-D-xylopyranoside gloriogenin (III). Only compound III at 5 micro/ml led to 100% mortality of the S. mansoni (EC50 = 2.25 and 1.91 microg/ml for female and male worm respectively) whereas compounds I and II did not show any activity up to 50 microg/ml.

Characterization of cysteine proteases in Malian medicinal plants.

Extracts form 10 different Malian medicinal plants with a traditional use against schistosomiasis were investigated for their possible content of proteolytic activity. The proteolytic activity was studied by measuring the hydrolysis of two synthetic peptide substrates Z-Ala-Ala-Asn-NHMec and Z-Phe-Arg-NHMec. Legumain- and papain-like activities were found in all tested crude extracts except those from Entada africana, with the papain-like activity being the strongest. Cissus quadrangularis, Securidaca longepedunculata and Stylosanthes erecta extracts showed high proteolytic activities towards both substrates. After gel filtration the proteolytic activity towards the substrate Z-Ala-Ala-Asn-NHMec in root extract of Securidaca longepedunculata appeared to have Mr of 30 and 97kDa, while the activity in extracts from Cissus quadrangularis was at 39kDa. Enzymatic activity cleaving the substrate Z-Phe-Arg-NHMec showed apparent Mr of 97 and 26kDa in extracts from roots and leaves of Securidaca longepedunculata, while in Cissus quadrangularis extracts the activity eluted at 39 and 20kDa, with the highest activity in the latter. All Z-Phe-Arg-NHMec activities were inhibited by E-64 but unaffected by PMSF. The legumain activity was unaffected by E-64 and PMSF. The SDS-PAGE analysis exhibited five distinct gelatinolytic bands for Cissus quadrangularis extracts (115, 59, 31, 22 and 20kDa), while two bands (59 and 30kDa) were detected in Securidaca longepedunculata extracts. The inhibition profile of the gelatinolytic bands and that of the hydrolysis of the synthetic substrates indicate the cysteine protease class of the proteolytic activities. Several cysteine protease activities with different molecular weights along with a strong variability of these activities between species as well as between plant parts from the same species were observed.

Molluscicidal and antischistosomal activities of Zingiber officinale.

Experiments were conducted to study the major constituents of Zingiber officinale responsible for its molluscicidal activity and the effect of the active component on different stages of Schistosoma mansoni. Gingerol and shogaol exhibited potent molluscicidal activity on Biomphalaria glabrata. Gingerol (5.0 ppm) completely abolished the infectivity of Schistosoma mansoni miracidia and cercariae in B. glabrata and mice, respectively, indicating that the molluscicide is capable of interrupting schistosome transmission at a concentration lower than its molluscicidal concentrations.

On the use of plants and plant-derived compounds for the control of schistosomiasis.

The rising costs of chemotherapy and synthetic molluscides have led to an increasing interest in plants which are lethal to the intermediate host of schistosomiasis (bilharzia). Over one thousand species have been tested but only a few have been phytochemically examined. Approximately fifty molluscicidal compounds have so far been isolated from plants, including saponins, terpenoids, flavonoids, naphthoquinones and tannins. The saponins from Phytolacca dodecandra are the most active and have been successfully employed in field tests. The latest results in this area and the problems involved in the use of plants and natural products for the control of schistosomiasis are discussed here.