Assessment of the antidiarrhoeal properties of the aqueous extract, the 80% methanol extract and its soluble fractions of the leaves of Alstonia congensis Engl. (Apocynaceae) in Wistar rats.

AIM OF THE STUDY: To evaluate the antidiarrhoeal properties of Alstonia congensis leaves claimed to be effective for the treatment of diarrhoea by traditional healers during our ethnopharmacological investigation conducted in Kinshasa, Democratic Republic of Congo. MATERIALS AND METHODS: The aqueous extract (decoction), and the 80% hot methanol extract (Soxhlet extraction) were obtained. This last extract was fractionated. The antidiarrhoeal activity was evaluated using castor oil and magnesium sulphate-induced diarrhoea in animals. The potential antibacterial activity of all samples was also assessed in vitro. RESULTS: At all oral doses of 100 and 200 mg/kg body weight, all A. congensis samples showed significant and dose-dependent antidiarrhoeal activity in treated Wistar rats characterised by significant increase of onset time and decrease of all other diarrhoeal parameters at various degrees compared to untreated groups in both models. At the highest oral dose of 200 mg/kg bodyweight, the 80% hot methanol and aqueous extracts produced 79.8 ± 2.1% and 78.6 ± 0.5%, and 75.0 ± 2.1% and 71.4 ± 2.1% inhibition of defecation and diarrhoea respectively against castor oil-induced diarrhoea, and 75.0 ± 1.2% and 73.3±1.2% inhibition of diarrhoea respectively against magnesium sulphate-induced diarrhoea. The 80% hot methanol and aqueous detannified extracts showed low activity (42-47% inhibition of defecation and/or diarrhoea in both tests) suggesting that tannins may be responsible for the observed activity. At the same oral doses, the total alkaloid extract, the chloroform soluble fraction rich in alkaloids, the 80% methanol and the alkaline aqueous soluble subfractions produced more than 50% inhibition of defecation and/or diarrhoea in both tests. From the antibacterial testing in vitro, results indicated that all A. congensis samples exhibited an antibacterial activity mainly against bacteria implicated in diarrhoea with MIC and MBC values in the range of 15.6-500 µg/ml. The most active samples were the aqueous (decoction) and the 80% hot methanol dried extracts, the chloroform subfraction rich in alkaloids and the total alkaloid extract (MIC: 15.7-125 µg/ml, MBC: 31.2-250 µg/ml). Proteus varibilis was found to be the most resistant microorganism. CONCLUSION: These reported results can partly support and justify the traditional use of extracts from Alstonia congensis leaves for the treatment of diarrhoea in tradittional medicine.

Rapid quantification of 14 saponins of Maesa lanceolata by UPLC-MS/MS.

Saponins are high molecular weight glycosides which are known for their broad range of biological activities. In case of Maesa lanceolata, a tree growing in African countries, the maesasaponins showed virucidal, haemolytic, molluscicidal and anti-angiogenic activity. Since the different activities are dependent on the structure of the saponins, a method was developed and validated for the analysis of the individual saponins in this plant. Since the saponins were only present in small amounts, it was necessary to develop a very sensitive analytical method. For the fast and sensitive analysis of the extracted and purified plant samples ultra-performance liquid chromatography was coupled to a triple quadrupole mass spectrometer for MS/MS detection. A method in positive ESI mode, using sodium acetate in the mobile phase, was developed. The sodium adduct ion was selected as the precursor ion since it provided better sensitivity and a better, more stable fragmentation compared to the deprotonated and protonated ions. The intensity of the signal obtained by fragmentation of the sodium adducts of the saponins, was optimized by the addition of different concentrations of sodium acetate to the mobile phase. Reference standards were not available for all 14 saponins. Therefore, a relative MS/UV response was calculated allowing the estimation of the saponins in real samples. alpha-Hederin was used as external standard. The method was linear over the investigated concentration range with a good correlation coefficient (>0.99). The intra- and inter-day precisions were below 15% for most maesasaponins with the exception of maesasaponin II, which showed a precision within 20%. The recoveries of the spiked pure compounds maesasaponin IV.1 and VII.1 were 96.6% and 85.5%, respectively. The validated method can be applied in the investigation of the content of 14 saponins in transgenic and non-transgenic plant material of M. lanceolata.

The spasmolytic activity of extracts and some isolated compounds from the leaves of Morinda morindoides (Baker) Milne-Redh. (Rubiaceae).

AIM: The study was aimed to evaluate the in vitro antispasmodic activity of Morinda morindoides leaves aqueous extract, its soluble fractions and isolated compounds to provide the pharmacological basis for its use for the treatment of constipation and diarrhoea in traditional medicine. METHODS: The antispasmodic activity of each sample was evaluated on acetylcholine (ACh) and the depolarized KCl solution induced contractions on guinea-pig isolated ileum suspended in Tyrode's solution. RESULTS: At a test concentration of 40mug/ml in organ bath, the aqueous extract and its petroleum ether soluble fraction showed a spasmogenic effect on both agonists. The diethylether, ethyl acetate, n-butanol and residual aqueous phase soluble fractions from the partition of the aqueous extract exhibited spasmolytic activity producing 47-100% inhibition of contractions induced by both agonists with IC(50) values ranged from 6 to 15 microg/ml according to the case. In addition, the n-butanol and residual aqueous phase soluble fractions showed an inhibitory effect of 75 and 66% respectively on low high [K(+)] (25 mM) and 65 and 60% respectively on high [K+] (80 mM). Crude flavonoids showed spasmolytic on both agonists while crude saponins only showed spasmolytic activity on ACh and displayed spasmogenic effect on KCl. Quercetin, quercitrin and rutin exhibited significant antispasmodic effect with IC(50) values <0.1 microg/ml. Epoxygaertneroside and gaertneroside showed good antispasmodic activity on both agonists (4

Development and validation of an HPLC-method for the determination of alkaloids in the stem bark extract of Nauclea pobeguinii.

A new method was developed and validated for the quantification of strictosamide in the extract of the stem bark of Nauclea pobeguinii. This plant belongs to the Rubiaceae family and is widely used in the African traditional medicine against malaria and malaria-like symptoms. Alkaloids are suspected to be responsible for the antimalarial activity. One of these alkaloids is strictosamide, already reported to be the major constituent in the root bark of this plant. Because strictosamide was not commercially available another alkaloid, ajmalicine HCl, with comparable properties was used as a secondary standard. The samples of the dried 80% ethanol extract from the stem bark of N. pobeguinii were purified on C(18) solid phase extraction cartridges and analysed using HPLC-UV. The strictosamide used for the validation of the correction factor for response was isolated and purified by means of preparative HPLC and TLC. Although the relative standard deviation (R.S.D.) of 2.6% was still acceptable, the response factor was determined for every analysis based on the ratio of the peak area of strictosamide compared to the peak area of ajmalicine HCl in a concentration of 0.01 mg/ml. The precision of the method according to the time and the concentration, had a R.S.D. value of 2.2% and 2.6%, respectively. The recovery of the method was 92.2% (R.S.D. of 9.4%) which was acceptable. The method has been proven to be suitable for the determination of alkaloids in the extract of the stem bark of N. pobeguinii, according to the ICH guidelines on the validation of analytical methods.

Antiprotozoal and cytotoxic screening of 45 plant extracts from Democratic Republic of Congo.

AIM OF THE STUDY: To evaluate in vitro the antiprotozoal and cytotoxic activities of 80% methanol extract from 45 medicinal plants collected in Sankuru (Democratic Republic of Congo) against Trypanosoma brucei brucei, Trypanosoma cruzi and the chloroquine-sensitive Ghanaian strain of Plasmodium falciparum, and MRC-5 cell lines respectively. MATERIAL AND METHODS: Different extracts were obtained by maceration of each plant part used with 80% methanol for 24h. The mixture was filtered and evaporated in vacuo to give corresponding dried extract. The activity against Trypanosoma brucei brucei and Trypanosoma cruzi were performed in 96 well tissue plates each containing 10 microl aqueous plant extract dilutions (100 to 0.01 microg/ml) with 10 microl of the parasite suspension cultured in Hirumi medium supplemented with 10% foetal calf serum, a solution of 2% penicillin/streptomycin (2% P/S) After 4 days incubation with Almar blueâ solution, fluorescence was measured at 500 nm emission and 530 nm excitation and results expressed as percentage reduction in parasite compared to control wells. The antiplasmodial activity of was assessed in vitro against the chloroquine-sensitive Ghanaian strain of Plasmodium falciparum cultured in RPMI-1640 medium by the lactate deshydrogenase assay in the presence of plant extracts (50 to 0.01 microg/ml). Cell-lines MRC-5 were cultured in MEM medium supplemented with 20mM l-glutamine, 16.5mM NaHCO(3), 5% foetal calf serum and 2% P/S solution. After 4h incubation, cell proliferation/viability was spectrophotomecally assessed at 540 nm after addition of MTT. In each assay, the IC50 value for each sample was derived by the drug concentration-response curves. RESULTS: The extracts from Alcornea cordifolia leaves, Momordica charantia whole plant, Omphalocarpum glomerata, root bark and Piptadia africanum stem bark showed good antiprotozoal activity against Trypanosoma brucei brucei with IC50 values from 0.7 to 7 microg/ml. Only Piptadenia africanum extract showed a pronounced antiprotozoal activity against Trypanosoma cruzi (IC50=4.0+/-06 microg/ml). The extracts from Alchornea cordifolia, Polyathia swaveleons stem bark, Sapium cornutum stem bark and Triclisia giletii stem bark exhibited a pronounced antiplasmodial activity against P. falciparum Ghanaian strain with IC50 values ranging from 0.5 to 3.0 microg/ml. Piptadenia africanum extract was the most cytotoxic sample (CC50=0.25 microg/ml) with poor selectivity against all selected protozoa (SI<10) while other active extracts did not show a significant cytotoxic effect against MCR-5 cell-lines with good selectivity according to the case. CONCLUSION: These active plant extracts are selected for extensive studies leading to the isolation of active constituents.

Ethnobotanical survey and antibacterial activity of some plants used in Guinean traditional medicine.

A total of 418 healers have been interviewed in Guinea, a coastal country of West Africa, ranging between 7 degrees 30 and 12 degrees 30 of northern latitude and 8 degrees and 15 degrees of western longitude. Plant species used by the local inhabitants to treat infectious diseases were identified using ethnobotanical, ethnographic and taxonomic methods. During these investigations, 218 plants were registered, of which the following were the most frequently used: Erythrina senegalensis, Bridelia ferruginea, Crossopteryx febrifuga, Ximenia americana, Annona senegalensis, Cochlospermum tinctorium, Cochlospermum planchonii, Lantana camara, Costus afer, Psidium guajava, Terminalia glaucescens, Uapaca somon and Swartzia madagascariensis. Most plants, and especially the leaves, were essentially used as a decoction. In order to assess antibacterial activity, 190 recipes were prepared and biologically tested, among which six showed activity (minimal inhibitory concentration<125 microg/ml) against Bacillus cereus, Mycobacterium fortuitum, Staphylococcus aureus, or Candida albicans, i.e., Entada africana, Chlorophora regia, Erythrina senegalensis, Harrisonia abyssinica, Uvaria tomentosa, and a mixture of six plants consisting of Swartzia madagascariensis, Isoberlinia doka, Annona senegalensis, Gardenia ternifolia, Terminalia glaucescens and Erythrina senegalensis.

Challenges and pitfalls in antioxidant research.

Over the last decade, much research has focused on the potential health benefits of antioxidants and indeed many synthetic and natural compounds have been evaluated for their antioxidant profile. However, in several studies only a limited number of assays, often poorly validated, are used and the techniques available frequently lack specificity. These limitations may incorrectly influence the results. This review will therefore focus on several pitfalls that may emerge in vitro and in vivo antioxidant research. First, different in vitro techniques to determine antioxidant potential are discussed, including radical scavenging assays and fingerprinting methods. As a rule, a panel of different assays is indispensable to characterize and establish in vitro antioxidant activity. Furthermore, as problems of absorption, distribution, metabolism and excretion are only accounted for by in vivo studies, the need for in vivo antioxidant research is pointed out. Several methods to characterize the in vivo activity of antioxidants, including major drawbacks and pitfalls of some assays, have been discussed. The availability of both a representative "oxidative stress" animal model and a battery of well-validated assays to assess the broad diversity of oxidative damage and antioxidative defence parameters, are crucial for antioxidant research in vivo.

A new decomposition product of dihydroartemisinin.

After prolonged storage, samples of dihydroartemisinin were found to contain a decomposition product with a molecular weight of 238, as evidenced by MS analysis, the formation of which was accelerated by heating at 60 degrees C for several days. This decomposition product was isolated and identified as 2-(3-oxobutyl)-3-methyl-6-(2-propanal)-cyclohexanon, known to be formed by thermolysis of dihydroartemisinin at 190 degrees C. However, during work-up of this compound a hitherto unknown decomposition product of dihydroartemisinin with a molecular weight of 210 was obtained and identified by 1H, 13C and two-dimensional NMR spectroscopy as 2-(3-oxobutyl)-3-methyl-6-ethyl-cyclohexanon. Most probably this product was formed by oxidation of the aldehyde functionality of the former decomposition product and subsequent decarboxylation.

Cytotoxicity and in vitro susceptibility of Entamoeba histolytica to Morinda morindoides leaf extracts and its isolated constituents.

An aqueous decotion (dried extract), an 80% MeOH extract from Morinda morindoides leaves, and 10 flavonoids and 4 iridoids isolated from the 80% MeOH extract were evaluated in vitro for their potential antiamoebic activity and their cytotoxic effect against MT-4 cells. Results indicated that the aqueous decoction and the 80% MeOH extract exhibited an interesting antiamoebic activity with IC(50) values of 3.1 +/- 1.7 and 1.7 +/- 0.6 microg/ml, respectively. Apigenin-7-O-glucoside and luteolin-7-O-glucoside exhibited a moderate antiamoebic activity with IC(50) values of 22.3 +/- 3.2 and 37.4 +/- 2.7 microg/ml, respectively. Kaempferol (IC(50) = 10.3 +/- 2.3 microg/ml), apigenin (IC(50) = 12.7 +/- 4.3 microg/ml), and luteolin (IC(50) = 17.8 +/- 4.3 microg/ml) showed a more pronounced activity than their corresponding glycosides. All tested iridoids displayed a very good activity with IC(50) values less than 10 microg/ml. The most active iridoids were epoxygaertneroside (IC(50) = 1.3 +/- 0.4 microg/ml) and methoxygaertneroside (IC(50) = 2.3. +/- 0.7), followed by gaertneroside and gaertneric acid with IC(50) values of 4.3 +/- 1.8 and 7.1 +/- 1.4 microg/ml, respectively. Except quercetin and quercetin-7,4'-dimethylether which have shown a cytotoxic effect with IC(50) ranging from 14 to 22 microg/ml. No correlation could be deduced between the observed antiamoebic and cytotoxic activity of these tested samples. A structure-activity relationship for isolated compounds is discussed. These findings support the medicinal report for the traditional use of Morinda morindoides leaves for the treatment of amoebiasis.

Antimalarial activities and toxicities of three plants used as traditional remedies for malaria in the Democratic Republic of Congo: Croton mubango , Nauclea pobeguinii and Pyrenacantha staudtii.

The antimalarial activities of crude extracts and 17 fractions from the partition of 80%-methanolic extracts of three plants (the stem bark of Croton mubango, the stem bark of Nauclea pobeguinii and the leaves of Pyrenacantha staudtii) used as antimalarial remedies in the Democratic Republic of Congo were studied both in vitro (against Plasmodium falciparum) and in mice infected with Pl. berghei berghei. The toxic effects of dried aqueous extracts of the plants were also investigated, in uninfected mice. The most active crude extracts in vitro, with median inhibitory concentrations (IC(50)) of <1 microg/ml, were found to be the methanolic and dichloromethane extracts of C. mubango, and the dichloromethane extracts of N. pobeguinii and Py. staudtii. The aqueous extract with the most antimalarial activity in vitro was that of C. mubango (IC(50) = 3.2 microg/ml), followed by that of N. probeguinii (IC(50) = 5.3 microg/ml) and then that of Py. staudii (IC(50) = 15.2 microg/ml). Results from the in-vivo tests of antimalarial activity showed that, at a daily oral dose of 200 mg/kg, all the dichloromethane extracts, the petroleum-ether, chloroformic, ethyl-acetate and residual water-soluble fractions from C. mubango, and the chloroformic, ethyl-acetate and n-butanolic fractions from Py. staudtii produced >80% chemosuppression of the parasitaemias by day 4. The aqueous extracts of C. mubango and N. probeguinii produced a slightly lower but still significant inhibition of parasitaemia (60%-80%) whereas that of Py. staudtii only suppressed the day-4 parasitaemias by 37%. The dried aqueous extract of the stem bark of C. mubango showed some signs of toxicity in mice, with median lethal doses (LD(50)) of 350 mg/kg in the female mice and 900 mg/kg in the male. The extract significantly increased the serum concentrations of glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) in mice of both sexes, but had no effect on the blood levels of creatinine or urea. No significant toxic effect was observed for the dried aqueous extracts of N. pobeguinii and Py. staudtii (LD(50) >5 g/kg). Neither of these extracts affected the serum concentrations of GPT or the blood concentrations of creatinine and urea, although the N. pobeguinii extract did increase the serum concentration of GOT.

Isolation and NMR spectra of syringaresinol-beta-D-glucoside from Cressa cretica.

The isolation, (1)H-NMR and revised (13)C-NMR assignments of syringaresinol-beta-D-glucoside from Cressa cretica are reported.

In vitro antiplasmodial activity of callus culture extracts and fractions from fresh apical stems of Phyllanthus niruri L. (Euphorbiaceae): part 2.

The ethanolic extracts from fresh apical stems of Phyllanthus niruri L. (Euphorbiaceae) cultured on Murashige and Skoog (MS) medium supplemented with IBA/BAP/Coco nucifera L. milk for 1, 2, 4 and 6 months were phytochemically and biologically investigated and compared with intact plant part and whole plant extracts. Results from the in vitro antiplasmodial testing indicated that the EtOH extract of a 1-month-old callus culture (IC(50) = 16.3 +/- 2.5 microg/ml) exhibited a higher activity than the ethanolic extracts of the fresh apical stem (IC(50) = 18.2 +/- 2.4 microg/ml) and callus cultures of 2-, 4- and 6-months-old (25 microg/ml < IC(50) < 40 microg/ml). These activities were however lower than that displayed by the ethanolic extract of the whole plant (IC(50) < 3 microg/ml). The EtOH extract of 1-month-old callus culture (the most active) was fractionated with solvents of different polarities. Its CH(2)Cl(2) fraction rich in terpenic constituents (IC(50) = 9.2 +/- 3.4 microg/ml) exhibited a higher antiplasmodial activity than its isoamylic alcohol fraction obtained at pH 2-3 (IC(50) = 25.6 +/- 2.3 microg/ml) rich in flavonoids. The activity of these two fractions was lower than that displayed by the same fractions from the whole plant (2 microg/ml < IC(50) < 3 microg/ml). Alkaloidic fractions from the whole plant and 1-month-old callus culture of fresh apical stem were considered as inactive (IC(50) > 100 microg/ml).

Evaluation of bioactive saponins and triterpenoidal aglycons for their binding properties on human endothelin ETA and angiotensin AT1 receptors.

Different types of triterpenes including saponins and aglycons were evaluated for their ability to inhibit [3H] BQ-123 and [3H] angiotensin II binding to the human endothelin 1 ETA and angiotensin II AT1 receptors, respectively. Selectivity for only one of the two receptors was exhibited by asiatic acid and its saponins (ETA) and oleanolic acid (AT1). To a lesser extent betulinic acid, beta-amyrin and friedelin also showed selectivity for the ETA receptor. To address the question whether the effect of saponins on cell membranes might interfere with the normal binding of specific radioligands to their receptors, the activity of saponins with different haemolytic properties were compared. Highly haemolytic saponins such as alpha-hederin and beta-escine showed partial (60%) inhibition of radioligand-binding to the ETA receptor and complete inhibition (100%) to the AT1 receptor. Moreover, the haemolytically inactive kryptoescine, at the same concentration, caused complete inhibiton of radioligand-binding to both receptors, indicating that inhibition of receptor binding was not related to the membrane-interacting properties of saponins.

In vitro antiplasmodial activity of extracts and fractions from seven medicinal plants used in the Democratic Republic of Congo.

The in vitro antiplasmodial activity of seven EtOH extracts and twenty fractions from the partition of the initial ethanolic extracts from seven African medicinal plants used in the Democratic Republic of Congo (DR Congo) for the treatment of malaria was evaluated. The most active EtOH extracts (IC50 < 3 microg/ml) were those from Cassia occidentalis leaves, Euphorbia hirta whole plant, Garcinia kola stem bark and Phyllanthus niruri whole plant. Their respective petroleum ether soluble fractions also exhibited an antiplasmodial activity with IC50 < 3 microg/ml. EtOH extracts from Vernonia amygdalina leaves (5 < IC50 < 10 microg/ml), Tetracera poggei leaves (10 < IC50 < 50 microg/ml) and Morinda morindoides leaves (50 < IC50 < 100 microg/ml) were less active, but their petroleum ether fractions exhibited a pronounced antiplasmodial activity (IC50 < 3 microg/ml). The same observation could also be made for the petroleum ether fraction from Cassia occidentalis, Euphorbia hirta, Garcinia kola and Phyllanthus niruri. Isoamyl alcohol fractions from Euphorbia hirta, Phyllanthus niruri and Vernonia amygdalina showed IC50) values less than 3 microg/ml, and from Cassia occidentalis, Garcinia kola, Morinda morindoides and Tetracera poggei between 10 and 50 microg/ml. The observed antiplasmodial activity may be related to the presence of terpenes, steroids, coumarins, flavonoids, phenolic acids, lignans, xanthones and anthraquinones.

Proanthocyanidins in health care: current and new trends.

Polyphenolic compounds are widely distributed in higher plants and are an integral part of the human diet. Recent interest in these substances has been stimulated by their potential health benefits, which are believed to arise mainly from their antioxidant activity. In the past years, the antioxidant activity of flavonoids has been studied in detail. An important but often overlooked group of polyphenols is that of the proanthocyanidins. Therefore, the present review is focused mainly on the antioxidant activity of proanthocyanidins and its relevancy in vivo. The three most important mechanisms of their antioxidant action will be discussed, i.e. free radical scavenging activity, chelation of transition metals, and inhibition of enzymes. In addition, the protective role of proanthocyanidins against lipid peroxidation and peroxynitrite, as well as their antimicrobial properties will be discussed. To study the in vivo relevancy of the proanthocyanidin activities, the knowledge of their pharmacokinetic parameters is crucial. Although bioavailability and metabolism data on polyphenols in general and proanthocyanidins in particular are still largely unavailable, the first reports indicate that at least monomers and smaller oligomeric procyanidins are absorbed. There is also considerable scientific and public interest in the important role that antioxidants may play in health care, e.g. by acting as cancer chemopreventive and anti-inflammatory agents and by reducing risk of cardiovascular mortality. Each of these aspects will be discussed, with special attention to the role of proanthocyanidins on apoptosis, gene expression and transcription factors, such as NF-kappa B.

Medicinal plants in Suriname: hypotensive effect of Gossypium barbadense.

In traditional medicine Gossypium barbadense L. is used against hypertension. Looking for a scientific basis for this use, the blood-pressure-lowering effect of the decoction of the leaves was confirmed. Fraction II (frII) of the crude extract of G. barbadense showed a dose-dependent hypotensive effect in anaesthetized rats. In hexamethonium-treated rats, the blood-pressure-lowering effect of frII was almost abolished. A small decrease of the blood-pressure-lowering effect was followed by an increase in the blood pressure. Phentolamine antagonized the increase in blood pressure in hexamethoniumtreated rats. High doses of atropine (4 mg/rat) suppressed both depressor and heart effects. In-vitro experiments revealed that atropine did not antagonize the contraction of the ileum of the rat. Tripelennamine in a concentration of 100 microg could not influence the contraction either, whereas 300 microg did. In the guinea-pig ileum 10 microg tripelennamine did not reduce the contraction significantly. In the mechanism of action of frII, acetylcholine receptors could be involved, but not histaminergic or adrenergic receptors. Although it is still not known which compound(s) in G. barbadense is (are) the active substance(s), the results obtained may explain the use of this plant in traditional medicine in Suriname.

Comparative study of eight well-known polyphenolic antioxidants.

Eight antioxidants from five different polyphenolic classes (cinnamic acids, benzoic acids, flavonoids, proanthocyanidins and stilbenes), and the water-soluble vitamin E derivative trolox were examined for their antioxidant activity in-vitro. In addition, the compounds were tested for their cytotoxicity on growing fibroblasts and their inhibition of the classical pathway of the complement system. Procyanidin C1 was shown to be a good scavenger of both DPPH(*) and HO(*), and a strong inhibitor of lipid peroxidation and the classical pathway of the complement system. Consequently, procyanidin C1 was classified as the most promising antioxidant in-vitro of all compounds tested. In contrast, genistein exhibited a very low antioxidant activity in both the lipid peroxidation and the DPPH(*) scavenging assay, a high cytotoxicity and a low complement-inhibiting activity.

Complement modulating activity of Rwandan medicinal plants.

Forty-two ethanolic extracts of thirty-six Rwandan medicinal plants were investigated for their influence on complement-mediated hemolysis. The plants were selected on the base of their ethnomedicinal use in infections and autoimmune diseases. Eight plant extracts showed an inhibitory activity against the classical pathway of the complement system and ten plant extracts against the alternative pathway. Three plant extracts exhibited an interesting activity against both pathways, i.e. Aspilia pluriseta, Coleus kilimandschari, and Macaranga kilimandscharica (leaves and stem). Further study indicated that the complement inhibitory activity was not caused by chelation of bivalent cations or by direct action on the target erythrocytes.

Antiviral activity of Rwandan medicinal plants against human immunodeficiency virus type-1 (HIV-1).

Selected plants used in Rwandan traditional medicine for the treatment of infections and/or rheumatoid diseases were investigated for antiviral activity in vitro against human immunodeficiency virus type-1 (HIV-1). Of the 38 tested 80% ethanolic extracts, belonging to plants of 21 different families only the extracts from the leaves of Aspilia pluriseta (Asteraceae) and Rumex bequaertii (Polygonaceae) had interesting selectivity indices (SI = ratio of the 50% cytotoxic concentration to the 50% effective antiviral concentration) higher than 1. Further fractionation of the initially antivirally inactive ethanolic extract of Tithonia diversifolia, however, led to an aqueous fraction with a high anti-HIV-1 activity (SI > 461), indicating that the cytotoxicity of some plant components may mask the antiviral properties of the active plant substances in total plant extracts.

Further evaluation of Rwandan medicinal plant extracts for their antimicrobial and antiviral activities.

A total of 45 Rwandan plant extracts, belonging to 37 different plant species out of 21 families, were investigated for their antibacterial, antifungal, and antiviral properties. The plants were selected on the base of their ethnomedicinal use against infections and autoimmune diseases. From all the plant extracts tested, only Clematis hirsuta (leaves) showed a pronounced antifungal activity against Candida albicans and the dermatophytes Trichophyton rubrum, Epidermophyton floccosum, and Microsporum canis. Seven plant extracts showed a high antiviral activity against the DNA-virus Herpes simplex type 1, while five and three plant extracts were highly active against the RNA-viruses Coxsackie and Polio, respectively. Only Macaranga kilimandscharica (leaves) showed an interesting anti-measles activity, whereas Eriosema montanum (leaves) and Entada abyssinica (leaves) were highly active against Semliki forest virus. Some plant extracts showed an antibacterial activity against Gram-positive bacteria and Mycobacterium fortuitum, but none of them were active against the Gram-negative bacteria tested.