Catherine Vonthron-Sénécheau

Leishmanicidal and Cholinesterase Inhibiting Activities of Phenolic Compounds from Allanblackia monticola and Symphonia globulifera

In a preliminary antiprotozoal screening of several Clusiaceae species, the methanolic extracts of Allanblackia monticola and Symphonia globulifera showed high in vitro leishmanicidal activity. Further bioguided phytochemical investigation led to the isolation of four benzophenones: guttiferone A (1), garcinol (2), cambogin (3) and guttiferone F (4), along with three xanthones: allanxanthone A (5), xanthone V1 (6) and globulixanthone C (7) as active constituents. Compounds 1 and 6 were isolated from S. globulifera leaves, while compounds 2-5 were obtained from A. monticola fruits. Guttiferone A (1) and F (4) showed particulary strong leishmanicidal activity in vitro, with IC50 values (0.2 microM and 0.16 microM, respectively) comparable to that of the reference compound, miltefosine (0.46 microM). Although the leishmanicidal activity is promising, the cytotoxicity profile of these compounds prevent at this state further in vivo biological evaluation. In addition, all the isolated compounds were tested in vitro for their anticholinesterase properties. The four benzophenones showed potent anticholinesterase properties towards acetylcholinesterase (AChE) and butylcholinesterase (AChE). For AChE, the IC50 value (0.66 microM) of garcinol (2) was almost equal to that of the reference compound galanthamine (0.50 microM). Furthermore, guttiferone A (1) and guttiferone F (4) (IC50 = 2.77 and 3.50 microM, respectively) were more active than galanthamine (IC50 = 8.5) against BChE.

Antiprotozoal Activities of Organic Extracts from French Marine Seaweeds

Marine macrophytes contain a variety of biologically active compounds, some reported to have antiprotozoal activity in vitro. As a part of a screening program to search for new natural antiprotozoals, we screened hydroalcoholic and ethyl acetate extracts of 20 species of seaweeds from three phyla (Rhodophyta, Heterokontophyta and Chlorophyta), sampled along the Normandy (France) coast. We tested them in vitro against the protozoa responsible for three major endemic parasitic diseases: Plasmodium falciparum, Leishmania donovani and Trypanosoma cruzi. The selectivity of the extracts was also evaluated by testing on a mammalian cell line (L6 cells). Ethyl acetate extracts were more active than hydroalcoholic ones. Activity against T. cruzi and L. donovani was non-existent to average, but almost half the extracts showed good activity against P. falciparum. The ethyl acetate extract of Mastocarpus stellatus showed the best antiplasmodial activity as well as the best selectivity index (IC50 = 2.8 μg/mL; SI > 30). Interestingly, a red algae species, which shares phylogenetic origins with P. falciparum, showed the best antiplasmodial activity. This study is the first to report comparative antiprotozoal activity of French marine algae. Some of the species studied here have not previously been biologically evaluated.

Antiprotozoal activities of some constituents of Markhamia tomentosa (Bignoniaceae)

Abstract Phytochemical investigation of an ethyl-acetate extract of the stem bark of Markhamia tomentosa (Bignoniaceae), which had good antimalarial activity in vitro, resulted in the isolation of eight known compounds: 2-acetylnaphtho[2,3-b]furan-4,9-dione (1), 2-acetyl-6-methoxynaphtho[2,3-b]furan-4,9-dione (2), oleanolic acid (3), pomolic acid (4), 3-acetylpomolic acid (5), tormentic acid (6), β-sitosterol (7) and β-sitosterol-3-O-β-D-glucopyranoside (8). The structures of these compounds were established by spectroscopic methods. Each of compounds 1, 2, 4 and 5 was evaluated in vitro for its antiprotozoal activities against the ring stages of two chloroquine-resistant strains of Plasmodium falciparum (K1 and W2), the amastigotes of Leishmania donovani, and the bloodstream trypomastigotes of Trypanosoma brucei rhodesiense (the species responsible for human malaria, visceral leishmaniasis and African trypanosomiasis, respectively). Although compounds 1 and 2 exhibited potent antiprotozoal activities, they also showed high toxicity against a mammalian (L-6) cell line.

Eleganolone, a diterpene from the french marine alga Bifurcaria bifurcata inhibits growth of the human pathogens Trypanosoma brucei and Plasmodium falciparum

Organic extracts of 20 species of French seaweed have been screened against Trypanosoma brucei rhodesiense trypomastigotes, the parasite responsible for sleeping sickness. These extracts have previously shown potent antiprotozoal activities in vitro against Plasmodium falciparum and Leishmania donovani. The selectivity of the extracts was also evaluated by testing cytotoxicity on a mammalian L6 cell line. The ethyl acetate extract of the brown seaweed, Bifurcaria bifurcata, showed strong trypanocidal activity with a mild selectivity index (IC50 = 0.53 µg/mL; selectivity index (SI) = 11.6). Bio-guided fractionation led to the isolation of eleganolone, the main diterpenoid isolated from this species. Eleganolone contributes only mildly to the trypanocidal activity of the ethyl acetate extract (IC50 = 45.0 µM, SI = 4.0). However, a selective activity against P. falciparum erythrocytic stages in vitro has been highlighted (IC50 = 7.9 µM, SI = 21.6).

In vitro antileishmanial, antiplasmodial and cytotoxic activities of a new ventiloquinone and five known triterpenes from Parinari excelsa

Context: Parinari excelsa Sabine (Chrysobalanaceae) is an indigenous tree from West and Eastern Africa. This tree is used in Ivory Coast as an antimalaria remedy. Objective: The in vitro antiplasmodial and antileishmanial activities of the stem bark, the leaf and the major compounds from the stem bark were investigated. Materials and methods: The leaves and stem bark from P. excelsa were separately collected, air-dried and powdered. Two extracts (methylene chloride and methanol) were realized for both powders. Every extract was tested for its antiplasmodial and antileishmanial activities. Only the stem bark crude extracts were fractionated by column chromatography and their major components were analyzed by NMR, HRESIMS and IR methods. The compounds were tested for their antiplasmodial and antileishmanial activities. Results: The comparison of the IC50 values of the crude extracts were in this ordrer: 3.41 (IC50 of PeBMc) <4.10 (IC50 of PeBMc) <4.42 (IC50 of PeLMe) against P. falciparum and 5.19 (IC50 of PeBMc) <12.32 (IC50 of PeBMe) <19.33 (IC50 of PeLMc) <32.37 (IC50 of PeLMe) against L. donovani. The stem bark crude extracts were the most active against both parasites. Their fractionation leaded to a new ventiloquinone, five triterpenes and one chlorogenic acid. All these compounds were isolated for the first time from P. excelsa. High activities were observed with (3β)-3-hydroxyolean-12-en-28-oic acid (IC50 = 8.2 µM) and 3β-hydroxyolean-5,12-dien-28-oic acid (IC50 = 7.7 µM) against L. donovani. With the antiplasmodial activity, the best activity was observed with 16β-hydroxylupane-1,20(29)-dien-3-one (IC50 = 28.3 µM). Discussion and conclusion: These findings demonstrated that the constituents of P. excelsa stem bark have in vitro antiplasmodial and antileishmanial activities.

Antiplasmodial and anti-inflammatory effects of an antimalarial remedy from the Wayana Amerindians, French Guiana: Takamalaimë (Psidium acutangulum Mart. ex DC., Myrtaceae)

ETHNOPHARMACOLOGICAL RELEVANCE Field investigations highlighted the use of Psidium acutangulum Mart. ex DC (syn. P. persoonii McVaugh), a small tree used by the Wayana Amerindians in Twenke-Taluhwen and Antecume-Pata, French Guiana, for the treatment of malaria, and administered either orally in the form of a decoction or applied externally over the whole body. This use appears limited to the Wayana cultural group in French Guiana and has never been reported anywhere else. Our goal was to evaluate the antimalarial and anti-inflammatory activities of a P. acutangulum decoction to explain the good reputation of this remedy. MATERIALS AND METHODS Interviews with the Wayana inhabitants of Twenke-Taluhwen and Antecume-Pata were conducted within the TRAMAZ project according to the TRAMIL methodology, which is based on a quantitative and qualitative analysis of medicinal plant uses. A decoction of dried aerial parts of P. acutangulum was prepared in consistency with the Wayana recipe. In vitro antiplasmodial assays were performed on chloroquine-resistant FcB1 ([(3)H]-hypoxanthine bioassay) and 7G8 (pLDH bioassay) P. falciparum strains and on chloroquine sensitive NF54 ([(3)H]-hypoxanthine bioassay) P. falciparum strain. In vitro anti-inflammatory activity (IL-1β, IL-6, IL-8, TNFα) was evaluated on LPS-stimulated human PBMC and NO secretion inhibition was measured on LPS stimulated RAW murine macrophages. Cytotoxicity of the decoction was measured on L6 mammalian cells, PBMCs, and RAW cells. A preliminary evaluation of the in vivo antimalarial activity of the decoction, administered orally twice daily, was assessed by the classical four-day suppressive test against P. berghei NK65 in mice. RESULTS The decoction displayed a good antiplasmodial activity in vitro against the three tested strains, regardless to the bioassay used, with IC50 values of 3.3µg/mL and 10.3µg/mL against P. falciparum FcB1 and NF54, respectively and 19.0µg/mL against P. falciparum 7G8. It also exhibited significant anti-inflammatory activity in vitro in a dose dependent manner. At a concentration of 50µg/mL, the decoction inhibited the secretion of the following pro-inflammatory cytokines: TNFα (-18%), IL-1β (-58%), IL-6 (-32%), IL-8 (-21%). It also exhibited a mild NO secretion inhibition (-13%) at the same concentration. The decoction was non-cytotoxic against L6 cells (IC50>100µg/mL), RAW cells and PBMC. In vivo, 150µL of the decoction given orally twice a day (equivalent to 350mg/kg/day of dried extract) inhibited 39.7% average parasite growth, with more than 50% of inhibition in three mice over five. The absence of response for the two remaining mice, however, induced a strong standard deviation. CONCLUSIONS This study highlighted the in vitro antiplasmodial activity of the decoction of P. acutangulum aerial parts, used by Wayana Amerindians from the Upper-Maroni in French Guiana in case of malaria. Its antioxidant and anti-inflammatory potential, which may help to explain its use against this disease, was demonstrated using models of artificially stimulated cells.

Phytochemical Study and Antiprotozoal Activity of Compounds Isolated from Thalia geniculata.

Abstract Thalia geniculata. L. (Marantaceae) is an African medicinal plant traditionally used in Benin to treat malaria and other parasitic diseases. There is little ethnobotanical and almost no chemical information available for this species. The phytochemical analysis of the aerial parts of the plant led to the isolation of five compounds, identified as sitoindoside I [β-sitosterol-(6-O.-hexadeca-noyl)-3-O.-β-d-glucoside] (1), daucosterol β-sitosterol-3-0-β-d-glucoside (2), stigmasterol (3), β-sitosterol (4), and geranylfarnesol (5). The structural elucidation was achieved using spectrometric methods and by comparison with the literature. Biological activity was evaluated against Plasmodium falciparum, Trypanosoma rhodesiense, Trypanosoma cruzi.,and Leishmania donovani.. Geranylfarnesol (5) showed significant antiprotozoal activity against P. falciparum. and L. donovani., with IC50 values of 12.7 and 13.2 μM, respectively.

X-ray structure of floridoside isolated from the marine red algae Dilsea carnosa

The natural floridoside (2-O-alpha-d-galactopyranosylglycerol) was isolated from Dilsea carnosa, and its structure has been determined by single-crystal X-ray diffraction analysis. The solved structure is in agreement with the previously solved crystal structure of floridoside [Simon-Colin, C.; Michaud, F.; Léger, J.-M.; Deslandes E. Carbohydr. Res.2003, 338, 2413-2416] and demonstrates for the first time the presence of floridoside in the red algae Dilsea carnosa.

Wayanin and guaijaverin, two active metabolites found in a Psidium acutangulum Mart. ex DC (syn. P. persoonii McVaugh) (Myrtaceae) antimalarial decoction from the Wayana Amerindians

ETHNOPHARMACOLOGICAL RELEVANCE Psidium acutangulum Mart. ex DC is a small tree used by the Wayana Amerindians from the Upper-Maroni in French Guiana for the treatment of malaria. AIM OF THE STUDY In a previous study, we highlighted the in vitro antiplasmodial, antioxidant and anti-inflammatory potential of the traditional decoction of P. acutangulum aerial parts. Our goal was then to investigate on the origin of the biological activity of the traditional remedy, and eventually characterize active constituents. MATERIALS AND METHODS Liquid-liquid extractions were performed on the decoction, and the antiplasmodial activity evaluated against chloroquine-resistant FcB1 ([(3)H]-hypoxanthine bioassay) and 7G8 (pLDH bioassay) P. falciparum strains, and on a chloroquine sensitive NF54 ([(3)H]-hypoxanthine bioassay) P. falciparum strain. The ethyl acetate fraction (D) was active and underwent bioguided fractionation. All the isolated compounds were tested on P. falciparum FcB1 strain. In vitro anti-inflammatory activity (IL-1β, IL-6, IL-8, TNFα) of the ethyl acetate fraction and of an anti-Plasmodium active compound, was concurrently assessed on LPS-stimulated human PBMC and NO secretion inhibition was measured on LPS stimulated RAW murine macrophages. Cytotoxicity of the fractions and pure compounds was measured on VERO cells, L6 mammalian cells, PBMCs, and RAW cells. RESULTS Fractionation of the ethyl acetate soluble fraction (IC50 ranging from 3.4 to <1µg/mL depending on the parasite strain) led to the isolation of six pure compounds: catechin and five glycosylated quercetin derivatives. These compounds have never been isolated from this plant species. Two of these compounds (wayanin and guaijaverin) were found to be moderately active against P. falciparum FcB1 in vitro (IC50 5.5 and 6.9µM respectively). We proposed the name wayanin during public meetings organized in June 2015 in the Upper-Maroni villages, in homage to the medicinal knowledge of the Wayana population. At 50µg/mL, the ethyl acetate fraction (D) significantly inhibited IL-1β secretion (-46%) and NO production (-21%), as previously observed for the decoction. The effects of D and guiajaverin (4) on the secretion of other cytokines or NO production were not significant. CONCLUSIONS The confirmed antiplasmodial activity of the ethyl acetate soluble fraction of the decoction and of the isolated compounds support the previous results obtained on the P. acutangulum decoction. The antiplasmodial activity might be due to a mixture of moderately active non-toxic flavonoids. The anti-inflammatory activities were less marked for ethyl acetate fraction (D) than for the decoction.

(10E,12E,14E)-9,16-Dioxoocta-deca-10,12,14-trienoic acid.

The title octadecatrienoic acid derivative, C18H26O4, was isolated from Silene maritima With. (Caryophyllaceae), the first time this natural compound has been found in the Caryophyllales order. This fatty acid has an 18-carbon backbone with three double bonds on trans (E) conformation and two carbonyl. In the crystal, molecules are linked via pairs of O—H⋯O hydrogen bonds, forming inversion dimers.