An Unusually Broad Series of Seven Cyclombandakamines, Bridged Dimeric Naphthylisoquinoline Alkaloids from the Congolese Liana Ancistrocladus ealaensis.

A series of seven unusual dimeric naphthylisoquinoline alkaloids was isolated from the leaves of the tropical liana Ancistrocladus ealaensis J. Léonard, named cyclombandakamine A (1), 1-epi-cyclombandakamine A (2), and cyclombandakamines A3-7 (3-7). These alkaloids have a chemically thrilling structural array consisting of a twisted dihydrofuran-cyclohexenone-isochromene system. The 1'″-epimer of 4, cyclombandakamine A1 (8), had previously been discovered in an unidentified Ancistrocladus species related to A. ealaensis. Both lianas produce the potential parent precursor, mbandakamine A (9), but only A. ealaensis synthesizes the corresponding cyclized form, along with a broad series of slightly modified analogs. The challenging isolation required, besides multi-dimensional chromatography, the use of a pentafluorophenyl stationary phase. Featuring up to six stereocenters and two types of chiral axes, their structures were elucidated by means of 1D and 2D NMR, HRESIMS, in combination with oxidative chemical degradation experiments as well as chiroptical (electronic circular dichroism spectroscopy) and quantum chemical calculations. Compared to the 'open-chain' parent compound 9, these dimers displayed rather moderate antiplasmodial activities.

Design, Synthesis, and Biological Evaluation of New 1-(Aryl-1 H-pyrrolyl)(phenyl)methyl-1 H-imidazole Derivatives as Antiprotozoal Agents.

We have designed and synthesized a series of new imidazole-based compounds structurally related to an antiprotozoal agent with nanomolar activity which we identified recently. The new analogues possess micromolar activities against Trypanosoma brucei rhodesiense and Leishmania donovani and nanomolar potency against Plasmodium falciparum. Most of the analogues displayed IC50 within the low nanomolar range against Trypanosoma cruzi, with very high selectivity toward the parasite. Discussion of structure-activity relationships and in vitro biological data for the new compounds are provided against a number of different protozoa. The mechanism of action for the most potent derivatives (5i, 6a-c, and 8b) was assessed by a target-based assay using recombinant T. cruzi CYP51. Bioavailability and efficacy of selected hits were assessed in a T. cruzi mouse model, where 6a and 6b reduced parasitemia in animals >99% following intraperitoneal administration of 25 mg/kg/day dose for 4 consecutive days.

Ancistrobrevines E-J and related naphthylisoquinoline alkaloids from the West African liana Ancistrocladus abbreviatus with inhibitory activities against Plasmodium falciparum and PANC-1 human pancreatic cancer cells.

From the roots of the West African liana Ancistrocladus abbreviatus (Ancistrocladaceae), ten new naphthylisoquinoline alkaloids (7a, 7b, 8a, 8b, and 9-14), displaying three different coupling types (5,1', 5,8', and 7,8'), were isolated, among them a series of five 5,1'-linked representatives and four metabolites belonging to the rare group of 7,8'-coupled alkaloids. Two of the alkaloids, the ancistrobrevines I (13) and J (14), are only the fourth and fifth examples of 7,8'-linked naphthyldihydroisoquinolines ever found in nature. The stereostructures of the new plant metabolites were determined by spectroscopic, chemical (oxidative degradation), and chiroptical (electronic circular dichroism) methods. For the assignment of the axial configuration of 13 and 14 relative to the stereocenter at C-3, which is too far away for significant NOE long-range interactions, these 7,8'-coupled naphthyldihydroisoquinolines were stereoselectively converted into the respective cis-configured tetrahydroisoquinoline analogs. The newly generated 'auxiliary' stereocenter at C-1 permitted decisive NOE interactions between the isoquinoline and the naphthalene parts, and thus a reliable attribution of the axial configuration of 13 and 14. In addition, five known compounds (3, 5, 16, 17, and 20), previously discovered in related African and Asian Ancistrocladus species, have now for the first time been identified in A. abbreviatus. All of these alkaloids are S-configured at C-3 and bear an oxygen function at C-6, and are, thus, typical Ancistrocladaceae-type compounds. Some of the alkaloids of A. abbreviatus exhibited promising activities against the malaria parasite Plasmodium falciparum and PANC-1 human pancreatic cancer cells.

Sesquiterpene Lactones from Vernonia cinerascens Sch. Bip. and Their in Vitro Antitrypanosomal Activity.

In the endeavor to obtain new antitrypanosomal agents, particularly sesquiterpene lactones, from Kenyan plants of the family Asteraceae, Vernonia cinerascens Sch. Bip. was investigated. Bioactivity-guided fractionation and isolation in conjunction with LC/MS-based dereplication has led to the identification of vernodalol (1) and isolation of vernodalin (2), 11ß,13-dihydrovernodalin (3), 11ß,13-dihydrovernolide (4), vernolide (5), 11ß,13-dihydrohydroxyvernolide (6), hydroxyvernolide (7), and a new germacrolide type sesquiterpene lactone vernocinerascolide (8) from the dichloromethane extract of V. cinerascens leaves. Compounds 3-8 were characterized by extensive analysis of their 1D and 2D NMR spectroscopic and HR/MS spectrometric data. All the compounds were evaluated for their in vitro biological activity against bloodstream forms of Trypanosoma brucei rhodesiense and for cytotoxicity against the mammalian cell line L6. Vernodalin (2) was the most active compound with an IC50 value of 0.16 µM and a selectivity index of 35. Its closely related congener 11ß,13-dihydrovernodalin (3) registered an IC50 value of 1.1 µM and a selectivity index of 4.2.

Antiprotozoal Sesquiterpene Lactones and Other Constituents from Tarchonanthus camphoratus and Schkuhria pinnata.

In continuation of a search for new antiprotozoal agents from plants of the family Asteraceae, Tarchonanthus camphoratus and Schkuhria pinnata have been investigated. By following the promising in vitro activity of the dichloromethane extracts from their aerial parts, bioassay-guided chromatographic isolation yielded two known sesquiterpene lactones (1 and 2) from T. camphoratus and 20 known compounds of this type from S. pinnata. From the latter, a new eudesmanolide, (1R*,5S*,6R*,7R*,8R*,10R*)-1-hydroxy-8-[5″-hydroxy-4'-(2″-hydroxyisovaleroyloxy)tigloyloxy]-3-oxoeudesma-11(13)-en-6,12-olide (3), and two new germacranolides, 3ß-(2″-hydroxyisovaleroyloxy)-8ß-(3-furoyloxy)costunolide (14) and 1(10)-epoxy-3ß-hydroxy-8ß-[5'-hydroxy-4'-(2″-hydroxyisovaleroyloxy)tigloyloxy]costunolide (16), were obtained. Additionally, the flavonoid pectolinarigenin (24) and 3-hydroxy-4,5-dimethoxybenzenepropanol (25) were also isolated from S. pinnata. The compounds were characterized by analysis of 1D and 2D NMR spectroscopic and HR/MS data. In vitro antitrypanosomal activity and cytotoxicity against mammalian cells (L6 cell line) were evaluated for all the compounds. Santhemoidin A (13) and 3ß-(2″-hydroxyisovaleroyloxy)-8ß-(3-furoyloxy)costunolide (14) were the most active compounds found in this study, with IC50 values of 0.10 and 0.13 µM against Trypanosoma brucei rhodesiense trypomastigotes and selectivity indices of 20.5 and 29.7, respectively.

Terpenoids from the Oleo-Gum-Resin of Boswellia serrata and Their Antiplasmodial Effects In Vitro.

In the course of our ongoing search for new natural products as leads against protozoal diseases, the dichloromethane extract of Indian frankincense, the oleo-gum-resin obtained from Boswellia serrata, showed in vitro activity against Plasmodium falciparum. Bioactivity-guided fractionation led to the isolation of eight diterpenes: (1S,3E,7E,11R)-verticilla-3,7,12(18)-triene (1), cembrene A (2), serratol (3), 1S,3E,7R,8R,11E-7,8-epoxy-cembra-3,11-dien-1-ol (4), incensole oxide (5), rel (1S,3R,7E,11S,12R)-1,12-epoxy-4-methylenecembr-7-ene-3, 11-diol (6), isoincensole oxide (7), and isodecaryiol (8). Furthermore, 10 triterpenes, namely, oleanolic acid (9), 11-keto-ß-boswellic acid (10), 3-epi-neoilexonol (11), uvaol (12), ß-boswellic aldehyde (13), 5α-tirucalla-8,24-dien-3α-ol (14), isoflindissone lactone (15), isoflindissol lactone (16), rel (8R,9S,20R)-tirucall-24-ene-3ß,20-diol (17), and rel (3α,8R, 9S,20R,24S)-20,24-epoxytirucalla-3,25-diol (18) as well as the sesquiterpene ß-bourbonene (19), the monoterpene carvacrol (20) and the phenyl propanoids methyleugenol (21), and p-methoxycinnamaldehyde (22) were isolated. All compounds were identified by mass spectrometry and nuclear magnetic resonance spectroscopic measurements. Compounds 6, 11, and 16-18 are described for the first time. Compounds 13 - 15 are isolated as natural products for the first time, compound 8 for the first time from a plant. Antiplasmodial IC50 values and cytotoxicity against L6 rat skeletal myoblasts were determined. Isoflindissone lactone (15) was the most active compound with an IC50 of 2.2 µM against P. falciparum and a selectivity index of 18.

Antiplasmodial Ealapasamines A-C,'Mixed' Naphthylisoquinoline Dimers from the Central African Liana Ancistrocladus ealaensis.

Three unusual heterodimeric naphthylisoquinoline alkaloids, named ealapasamines A-C (1-3), were isolated from the leaves of the tropical plant Ancistrocladus ealaensis J. Léonard. These 'mixed', constitutionally unsymmetric dimers are the first stereochemically fully assigned cross-coupling products of a 5,8'- and a 7,8'-coupled naphthylisoquinoline linked via C-6' in both naphthalene portions. So far, only two other West and Central Ancistrocladus species were known to produce dimers with a central 6,6″-axis, yet, in contrast to the ealapasamines, usually consisting of two 5,8'-coupled monomers, like e.g., in michellamine B. The new dimers 1-3 contain six elements of chirality, four stereogenic centers and the two outer axes, while the central biaryl axis is configurationally unstable. The elucidation of the complete stereostructures of the ealapasamines was achieved by the interplay of spectroscopic methods including HRESIMS, 1D and 2D NMR (in particular ROESY measurements), in combination with chemical (oxidative degradation) and chiroptical (electronic circular dichroism) investigations. The ealapasamines A-C display high antiplasmodial activities with excellent half-maximum inhibition concentration values in the low nanomolar range.

Antileukemic ancistrobenomine B and related 5,1'-coupled naphthylisoquinoline alkaloids from the Chinese liana Ancistrocladus tectorius.

A striking feature of the metabolite pattern of the Southeast Asian liana Ancistrocladus tectorius (Ancistrocladaceae) is the predominance of 5,1'-coupled naphthylisoquinoline alkaloids. About 20 alkaloids of this coupling type have so far been discovered in this plant species. Here, we report on the isolation of four new 5,1'-linked naphthylisoquinolines from the twigs and stems of A. tectorius. Two of them, the ancistrobenomines B (5) and C (6), belong to the very rare group of alkaloids with a fully dehydrogenated isoquinoline portion. Likewise unusual for naphthylisoquinoline alkaloids is the presence of a hydroxymethylene group at C-3. Within the large class of meanwhile ca. 180 such natural products, this structural peculiarity had so far been known only from two other representatives isolated from the Malaysian species A. benomensis, and from one single naphthalene-devoid 3-hydroxymethyleneisoquinoline from A. tectorius. Seven further 5,1'-linked alkaloids, previously isolated from related Asian and African Ancistrocladus species, have now been identified for the first time in A. tectorius. Their structural elucidation was achieved by spectroscopic analysis including HRESIMS, 1D and 2D NMR, and by chemical (oxidative degradation) and chiroptical (electronic circular dichroism) methods. Ancistrobenomine B (5) exhibited moderate effects against Plasmodium falciparum and Trypanosoma brucei rhodesiense in vitro, and it was found to display strong cytotoxic activities against drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and their multidrug-resistant subline, CEM/ADR5000.

Steroid Alkaloids from Holarrhena africana with Strong Activity against Trypanosoma brucei rhodesiense.

In our continued search for natural compounds with activity against Trypanosoma brucei, causative agent of human African trypanosomiasis (HAT, "sleeping sickness"), we have investigated extracts from the leaves and bark of the West African Holarrhenaafricana (syn. Holarrhena floribunda; Apocynaceae). The extracts and their alkaloid-enriched fractions displayed promising in vitro activity against bloodstream forms of T. brucei rhodesiense (Tbr; East African HAT). Bioactivity-guided chromatographic fractionation of the alkaloid-rich fractions resulted in the isolation of 17 steroid alkaloids, one nitrogen-free steroid and one alkaloid-like non-steroid. Impressive activities (IC50 in µM) against Tbr were recorded for 3ß-holaphyllamine (0.40 ± 0.28), 3α-holaphyllamine (0.37 ± 0.16), 3ß-dihydroholaphyllamine (0.67 ± 0.03), N-methylholaphyllamine (0.08 ± 0.01), conessimine (0.17 ± 0.08), conessine (0.42 ± 0.09), isoconessimine (0.17 ± 0.11) and holarrhesine (0.12 ± 0.08) with selectivity indices ranging from 13 to 302. Based on comparison of the structures of this congeneric series of steroid alkaloids and their activities, structure-activity relationships (SARs) could be established. It was found that a basic amino group at position C-3 of the pregnane or pregn-5-ene steroid nucleus is required for a significant anti-trypanosomal activity. The mono-methylated amino group at C-3 represents an optimum for activity. ∆5,6 unsaturation slightly increased the activity while hydrolysis of C-12ß ester derivatives led to a loss of activity. An additional amino group at C-20 engaged in a pyrrolidine ring closed towards C-18 significantly increased the selectivity index of the compounds. Our findings provide useful empirical data for further development of steroid alkaloids as a novel class of anti-trypanosomal compounds which represent a promising starting point towards new drugs to combat human African trypanosomiasis.

Alkamides from Anacyclus pyrethrum L. and Their in Vitro Antiprotozoal Activity.

In our ongoing study to evaluate the antiprotozoal activity of alkamides from Asteraceae, a dichloromethane extract from the roots of Anacycluspyrethrum L. showed a moderate in vitro activity against the NF54 strain of Plasmodium falciparum and against Leishmaniadonovani (amastigotes, MHOM/ET/67/L82 strain). Seven pure alkamides and a mixture of two further alkamides were isolated by column chromatography followed by preparative high performance liquid chromatography. The alkamides were identified by mass- and NMR-spectroscopic methods as tetradeca-2E,4E-dien-8,10-diynoic acid isobutylamide (anacycline, 1), deca-2E,4E-dienoic acid isobutylamide (pellitorine, 2), deca-2E,4E,9-trienoic acid isobutylamide (3), deca-2E,4E-dienoic acid 2-phenylethylamide (4), undeca-2E,4E-dien-8,10-diynoic acid isopentylamide (5), tetradeca-2E,4E,12Z-trien-8,10-diynoic acid isobutylamide (6), and dodeca-2E,4E-dien acid 4-hydroxy-2-phenylethylamide (7). Two compounds-undeca-2E,4E-dien-8,10-diynoic acid 2-phenylethylamide (8) and deca-2E,4E-dienoic acid 4-hydroxy-2-phenylethylamide (9)-were isolated as an inseparable mixture (1:4). Compounds 3, 4, and 5 were isolated from Anacycluspyrethrum L. for the first time. While compounds 4 and 5 were previously known from the genus Achillea, compound 3 is a new natural product, to the best of our knowledge. All isolated alkamides were tested in vitro for antiprotozoal activity against Plasmodium falciparum, Trypanosomabruceirhodesiense, Trypanosomacruzi, and Leishmaniadonovani and for cytotoxicity against L6 rat skeletal myoblasts.

Anti-Trypanosomatid Elemanolide Sesquiterpene Lactones from Vernonia lasiopus O. Hoffm.

Sleeping sickness or human African trypanosomiasis (HAT) is a neglected tropical disease (NTD) threatening millions of peoples' lives with thousands infected. The disease is endemic in poorly developed regions of sub-Saharan Africa and is caused by the kinetoplastid "protozoan" parasite Trypanosoma brucei. The parasites are transmitted to humans through bites of infected tsetse flies of the genus Glossina. The few available drugs for treatment of this disease are highly toxic, difficult to administer, costly and unavailable to poor rural communities bearing the major burden of this infection. Therefore, the search for new efficacious, safe and affordable drugs is of high importance. Vernonia lasiopus O. Hoffm., an indigenous African plant of the Asteraceae family, has been extensively reported to be used ethno-medicinally as a treatment for malaria. Its crude extracts obtained with solvents of different polarity were screened in vitro for anti-protozoal activity and the dichloromethane extract was found to be particularly active against Trypanosoma brucei rhodesiense (IC50 = 0.17 µg/mL). Bioassay-guided chromatographic fractionation of the dichloromethane extract led to the isolation and identification of six elemanolide type sesquiterpene lactones: 8-desacylvernolide, vernolepin, vernomenin, vernodalol, vernodalin and 11,13-dihydrovernodalin. All these elemanolide sesquiterpene lactones showed in vitro anti-trypanosomal activity. They were also tested for cytotoxicity against mammalian cells (L6 cell line). Vernolepin, the main component in the extract, was also the most potent with an IC50 value of 0.05 µg/mL against T.b. rhodesiense trypomastigotes. This compound showed a selectivity index of 14.5, which makes it an interesting candidate for in vivo tests and determination of its mechanism of action.

Cyclombandakamines A1 and A2, Oxygen-Bridged Naphthylisoquinoline Dimers from a Congolese Ancistrocladus Liana.

Cyclombandakamines A1 (1) and A2 (2), both with an unprecedented pyrane-cyclohexenone-dihydrofuran sequence and six stereocenters and two chiral axes, are the first oxygen-bridged dimeric naphthylisoquinoline alkaloids. They were isolated from the leaves of an as yet unidentified Congolese Ancistrocladus species. Their stereostructures were established by spectroscopic, chemical, and chiroptical methods in combination with DFT and TDDFT calculations. They apparently originate from a cascade of oxidative cyclization reactions of "open-chain" naphthylisoquinoline dimers and exhibit significant antiprotozoal activities.

Ancistectorine D, a naphthylisoquinoline alkaloid with antiprotozoal and antileukemic activities, and further 5,8'- and 7,1'-linked metabolites from the Chinese liana Ancistrocladus tectorius.

From the twigs and stems of the Chinese liana Ancistrocladus tectorius (Ancistrocladaceae), two new 5,8'-coupled naphthylisoquinolines, ancistectorine D (5) and its 6-O-demethyl derivative 6, were isolated, along with two new 7,1'-linked alkaloids, 6-O-methylancistectorine B1 (7) and ancistectorine B2 (8). Two further compounds, ancistroealaine A (4) and 6-O-demethyl-8-O-methyl-7-epi-ancistrobrevine D (10), already known from related Asian and African Ancistrocladus species, were discovered for the first time in A. tectorius. The structure elucidation was achieved by spectroscopic analysis including HRESIMS, 1D and 2D NMR, and by chemical (oxidative degradation) and chiroptical (circular dichroism) methods. Chemotaxonomically remarkable, 5,8'-coupled naphthylisoquinolines have as yet been found quite rarely in Asian Ancistrocladus species, where only two examples have so far been detected, while alkaloids with this coupling type represent the by far the largest group of constituents in African taxa. Ancistectorine D (5) shows promising activities against the protozoan parasites Trypanosoma cruzi and Leishmania donovani, and it was likewise found to display strong cytotoxic activities against human leukemia (CCRF-CEM) and multidrug-resistant tumor cells (CEM/ADR5000).

Antiprotozoal Activity Profiling of Approved Drugs: A Starting Point toward Drug Repositioning.

Neglected tropical diseases cause significant morbidity and mortality and are a source of poverty in endemic countries. Only a few drugs are available to treat diseases such as leishmaniasis, Chagas' disease, human African trypanosomiasis and malaria. Since drug development is lengthy and expensive, a drug repurposing strategy offers an attractive fast-track approach to speed up the process. A set of 100 registered drugs with drug repositioning potential for neglected diseases was assembled and tested in vitro against four protozoan parasites associated with the aforementioned diseases. Several drugs and drug classes showed in vitro activity in those screening assays. The results are critically reviewed and discussed in the perspective of a follow-up drug repositioning strategy where R&D has to be addressed with limited resources.

Search for Antiprotozoal Activity in Herbal Medicinal Preparations; New Natural Leads against Neglected Tropical Diseases.

Sleeping sickness, Chagas disease, Leishmaniasis, and Malaria are infectious diseases caused by unicellular eukaryotic parasites ("protozoans"). The three first mentioned are classified as Neglected Tropical Diseases (NTDs) by the World Health Organization and together threaten more than one billion lives worldwide. Due to the lack of research interest and the high increase of resistance against the existing treatments, the search for effective and safe new therapies is urgently required. In view of the large tradition of natural products as sources against infectious diseases [1,2], the aim of the present study is to investigate the potential of legally approved and marketed herbal medicinal products (HMPs) as antiprotozoal agents. Fifty-eight extracts from 53 HMPs on the German market were tested by a Multiple-Target-Screening (MTS) against parasites of the genera Leishmania, Trypanosoma, and Plasmodium. Sixteen HMPs showed in vitro activity against at least one of the pathogens (IC50 < 10 µg/mL). Six extracts from preparations of Salvia, Valeriana, Hypericum, Silybum, Arnica, and Curcuma exhibited high activity (IC50 < 2.5 µg/mL). They were analytically characterized by UHPLC/ESI-QqTOF-MSMS and the activity-guided fractionation of the extracts with the aim to isolate and identify the active compounds is in progress.

Antiprotozoal Effect of Artemisia indica Extracts and Essential Oil.

Diverse solvent extracts of Artemisia indica leaves originating from the West Bengal region (India) were assessed for the content of artemisinin and characteristic Artemisia polymethoxyflavonoids, namely eupatin (1), casticin (2), chrysoplenetin (3), cirsilineol (4), chrysophenol-D (5), and artemetin (6). HPLC-DAD and HPLC-MS were used to investigate the extracts macerated by solvents of increasing polarity, i.e., petroleum ether, n-hexane, dichloromethane, acetone, MeOH, or EtOH (either 96, 80, or 60 % v/v), and hot water. Artemisinin was absent in all extracts. The acetone and EtOH extracts comprised the highest levels of polymethoxyflavonoids, whereas no flavonoid could be detected in the infusion. None of the remaining extracts contained chryosphenol-D (5) or artemetin (6), while chrysoplenetin (3) was found in all extracts. The essential oil of the plant was also obtained by hydrodistillation and analysed by gas chromatography and gas chromatography-mass spectrometry simultaneously. Of the 92 compounds detected in the oil, camphor (13.0 %) and caryophyllene oxide (10.87 %) were the major components. All solvent extracts and the volatile oil showed in vitro antimalarial activity, plus a potential malaria prophylactic effect by inhibiting at least two recombinant plasmodial fatty acid biosynthesis (PfFAS-II) enzymes. Except for the infusion, all extracts were also active against other parasitic protozoa and displayed low cytotoxicity against mammalian cells. This is the first detailed study investigating both artemisinin and polymethoxyflavonoid content as well as in vitro malaria prophylactic and detailed antiprotozoal potential of A. indica extracts against a panel of protozoan parasites. This is also the first report of antiparasitic activity of the essential oil of the plant.

PLS-Prediction and Confirmation of Hydrojuglone Glucoside as the Antitrypanosomal Constituent of Juglans Spp.

Naphthoquinones (NQs) occur naturally in a large variety of plants. Several NQs are highly active against protozoans, amongst them the causative pathogens of neglected tropical diseases such as human African trypanosomiasis (sleeping sickness), Chagas disease and leishmaniasis. Prominent NQ-producing plants can be found among Juglans spp. (Juglandaceae) with juglone derivatives as known constituents. In this study, 36 highly variable extracts were prepared from different plant parts of J. regia, J. cinerea and J. nigra. For all extracts, antiprotozoal activity was determined against the protozoans Trypanosoma cruzi, T. brucei rhodesiense and Leishmania donovani. In addition, an LC-MS fingerprint was recorded for each extract. With each extract's fingerprint and the data on in vitro growth inhibitory activity against T. brucei rhodesiense a Partial Least Squares (PLS) regression model was calculated in order to obtain an indication of compounds responsible for the differences in bioactivity between the 36 extracts. By means of PLS, hydrojuglone glucoside was predicted as an active compound against T. brucei and consequently isolated and tested in vitro. In fact, the pure compound showed activity against T. brucei at a significantly lower cytotoxicity towards mammalian cells than established antiprotozoal NQs such as lapachol.

Evaluation of the in vitro trypanocidal activity of methylated flavonoid constituents of Vitex simplicifolia leaves.

BACKGROUND: Trypanosomiasis is a neglected tropical disease with complex clinical manifestations, tedious diagnosis, and difficult treatments. The drugs available for the treatment of this endemic disease are old, expensive, and associated with other problems including safety and drug resistant parasites. Therefore, there is an urgent need for the development of new, effective, cheap, and safe drugs for its treatment. Plants are potentially rich sources of leads for new drugs against trypanosomiasis. Vitex simplicifolia (Verbenaceae) is used traditionally for the treatment of tooth ache, edema, skin diseases, gout and trypanosomiasis in Nigeria. In a preliminary study, the methanol extract of Vitex simplicifolia was shown to exhibit a pronounced trypanocidal activity against T. b. rhodesiense. The present study was undertaken to investigate the active component responsible for the acclaimed activity of the leaves of Vitex simplicifolia in the traditional treatment of trypanosomiasis in Nigeria and other African countries. Our investigations aim at assessing the plant as a new source of potential trypanocidal compounds. METHODS: The crude extracts were prepared from the dried leaves using methanol, successive extraction with hexane, dichloromethane, ethylacetate and butanol was also done. The ethylacetate fraction was further fractionated and compounds isolated using preparative chromatographic technique and their structures were elucidated by NMR, mass spectrometry and comparison with literature data. Trypanocidal activities and cytotoxicity, using rat skeletal myoblast (L6) cells were investigated and their selectivity indices were determined. RESULTS: The chromatographic separations of the methanol extracts gave rise to seven compounds. The isolated compounds 2, 3, 6 and 7 exhibited promising trypanocidal activity with IC50 values ranging from 4.7-12.3 µg/ml and cytotoxicity in the range of 1.58- 46.20 µg/ml. Compound 6, however, showed the most selective trypanocidal activity with a selectivity index of 9.8. This is the first report of trypanocidal activity of flavonoids from this plant genus. CONCLUSIONS: The isolated compounds from Vitex simplicifolia exhibited noteworthy trypanocidal activities and hence may provide a source of new antitrypanosomal agents. These results also support the traditional use of Vitex simplicifolia in the treatment of trypanosomiasis. This is the first report of trypanocidal effect of flavonoids from this plant genus.

Anti-trypanosomal cadinanes synthesized by transannular cyclization of the natural sesquiterpene lactone nobilin.

Acid-catalyzed transannular cyclization of the germacrene-type sesquiterpene lactone nobilin 1 was investigated with the aim of obtaining new anti-trypanosomal cadinane derivatives. The reaction was regiospecific in all tested reaction conditions. Compounds were fully characterized by spectroscopic and computational methods, and the anti-trypanosomal activity was evaluated and compared to nobilin (IC50 3.19±1.69µM). The tricyclic derivative 11 showed most potent in vitro activity against Trypanosoma brucei rhodesiense bloodstream forms (IC50 0.46±0.01µM). Acid-catalyzed transannular cyclization of natural cyclodecadienes is an efficient strategy to generate new natural product derivatives with anti-protozoal activity.