Triterpenes from Momordica balsamina (African pumpkin): ABCB1 inhibition and synergistic interaction with doxorubicin in resistant cancer cells.

Aiming at overcoming multidrug resistance (MDR) in cancer, we have been studying Momordica balsamina, a vegetable known as African pumpkin. Five undescribed cucurbitane-type triterpenoids (balsaminaepoxide, balsaminatriol, balsaminoic acid, balsaminal, and balsaminol G) along with five known cucurbitacins were isolated from the methanol extract of Momordica balsamina aerial parts, whose structures were elucidated by spectroscopic data, mainly 1D and 2D NMR experiments. Compounds were evaluated for their ability as P-glycoprotein (P-gp/ABCB1) inhibitors in multidrug resistant human ABCB1-transfected mouse lymphoma cells (L5178Y, MDR) and resistant human colon adenocarcinoma cells (COLO 320), using the rhodamine-123 exclusion test, by flow cytometry. Several compounds, which were found to be non-cytotoxic, strongly inhibited P-gp efflux activity in a dose-dependent manner in both cell models. In MRD mouse lymphoma cells, balsaminol G and karavilagenin B were the most active, while in resistant colon adenocarcinoma cells, the strongest inhibitory activity was found for balsaminaepoxide, balsaminatriol and karavilagenin C, being several-fold more active than the positive control verapamil. In chemosensitivity assays, in a model of combination chemotherapy, selected compounds showed to interact synergistically with doxorubicin, thus substantiating their potential as MDR reversers. The strongest synergistic interaction was found for balsaminal and balsaminol G.

Triterpenoids from Momordica balsamina with a Collateral Sensitivity Effect for Tackling Multidrug Resistance in Cancer Cells.

The collateral sensitivity effect is among the most promising strategies for overcoming multidrug resistance in cancer. In this work, 28 cucurbitane-type triterpenoids (1: -28: ), previously isolated from the African medicinal plant Momordica balsamina and its derivatives, were evaluated for their collateral sensitivity effect on three different human cancer entities, gastric (EPG85-257), pancreatic (EPP85-181), and colon (HT-29), each with two different multidrug-resistant variants. One was selected for its resistance to daunorubicin (EPG85-257RDB, EPP85-181RDB, HT-29RDB) and the other was selected for its resistance to mitoxantrone (EPG85-257RNOV, EPP85-181RNOV, HT-29RNOV). On gastric cell lines, the best results were obtained for compounds 3: and 10: , which exhibited a collateral sensitivity effect together with high antiproliferative activity. In turn, on colon cancer cell lines, the best multidrug resistance-selective antiproliferative effects were observed for derivatives 11, 13: , and 15: , which showed collateral sensitivity effects against both resistant variants. Compounds 11: and 3: were also the most selective against the multidrug resistance pancreatic cells lines. Some compounds, such 6, 10, 11: and 15: , were previously found to be strong P-glycoprotein modulators, thus highlighting their potential as promising leads for overcoming multidrug resistance in cancer cells.

Bioactive compounds from the African medicinal plant Cleistochlamys kirkii as resistance modifiers in bacteria.

Cleistochlamys kirkii (Benth) Oliv. (Annonaceae) is a medicinal plant traditionally used in Mozambique to treat infectious diseases. The aim of this study was to find resistance modifiers in C. kirkii for Gram-positive and Gram-negative model bacterial strains. One of the most important resistance mechanisms in bacteria is the efflux pump-related multidrug resistance. Therefore, polycarpol (1), three C-benzylated flavanones (2-4), and acetylmelodorinol (5) were evaluated for their multidrug resistance-reverting activity on methicillin-susceptible and methicillin-resistant Staphylococcus aureus and Escherichia coli AG100 and AG100 A strains overexpressing and lacking the AcrAB-TolC efflux pump system. The combined effects of antibiotics and compounds (2 and 4) were also assessed by using the checkerboard microdilution method in both S. aureus strains. The relative gene expression of the efflux pump genes was determined by real-time reverse transcriptase quantitative polymerase chain reaction. The inhibition of quorum sensing was also investigated. The combined effect of the antibiotics and compound 2 or 4 on the methicillin-sensitive S. aureus resulted in synergism. The most active compounds 2 and 4 increased the expression of the efflux pump genes. These results suggested that C. kirkii constituents could be effective adjuvants in the antibiotic treatment of infections.

Dregamine and tabernaemontanine derivatives as ABCB1 modulators on resistant cancer cells.

Dregamine (1) and tabernaemontanine (2), two epimeric monoterpene indole alkaloids isolated in large amount from the roots of the African plant Tabernaemontana elegans, were derivatized, yielding ten imine derivatives, as previously described (3-12). In the present study, aiming at increasing the pool of analogues for establishing structure-activity relationships (SAR), compounds 1 and 2 were further submitted to several chemical transformations, yielding thirteen new derivatives (13-25). Their structures were assigned by spectroscopic methods, including 1D and 2D NMR experiments. Compounds 1-25 were evaluated for their effects on the reversion of multidrug resistance (MDR) in cancer cells mediated by P-glycoprotein (P-gp/ABCB1), through combination of functional and chemosensitivity assays, using a human ABCB1-transfected mouse T-lymphoma cell model. SAR analysis showed that different substituents at C-3 and at the indole nitrogen led to different ABCB1 modulatory effects. When compared to the parent compounds, a remarkable enhancement in MDR reversal activity was found for derivatives sharing a new aromatic moiety. Thus, the strongest ability as MDR reversers, and a manifold activity when compared to verapamil, was found for compound 8, the epimeric compounds 9 and 10, and compound 15, bearing pyrazine, bromo-pyridine, and methoxybenzyloxycarbonyl moieties, respectively. In drug combination assays, all compounds tested were revealed to interact synergistically with doxorubicin. Collectively, the results indicate that some of these derivatives may be promising leads for overcoming MDR in cancer.

Vobasinyl-Iboga Alkaloids from Tabernaemontana elegans: Cell Cycle Arrest and Apoptosis-Inducing Activity in HCT116 Colon Cancer Cells.

Phytochemical investigation of the roots of the African medicinal plant Tabernaemontana elegans led to the isolation of three new (1-3) and two known (4 and 5) bisindole alkaloids of the vobasinyl-iboga type. The structures of 1-3 were assigned by spectroscopic methods, mainly using 1D and 2D NMR experiments. All of the isolated compounds were evaluated for their cytotoxicity against HCT116 colon and HepG2 liver carcinoma cells by the MTS metabolism assay. Compounds 1-3 and 5 were found to be cytotoxic to HCT116 colon cancer cells, displaying IC50 values in the range 8.4 to >10 µM. However, the compounds did not display significant cytotoxicity against HepG2 cancer cells. The cytotoxicity of compounds 1-3 and 5 was corroborated using a lactate dehydrogenase assay. Hoechst staining and nuclear morphology assessment and caspase-3/7 activity assays were also performed for investigating the activity of compounds 1-3 and 5 as apoptosis inducers. The induced inhibition of proliferation of HCT116 cells by compounds 1 and 2 was associated with G1 phase arrest, while compounds 3 and 5 induced G2/M cell cycle arrest. These results showed that the new vobasinyl-iboga alkaloids 1-3 and compound 5 are strong inducers of apoptosis and cell cycle arrest in HCT116 colon cancer cells.

(3'R)-hydroxytabernaelegantine C: A bisindole alkaloid with potent apoptosis inducing activity in colon (HCT116, SW620) and liver (HepG2) cancer cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Tabernaemontana elegans Stapf. (Apocynaceae) is a medicinal plant traditionally used in African countries to treat cancer. AIMS OF THE STUDY: To discover new apoptosis inducing lead compounds from T. elegans and provide scientific validation of the ethnopharmacological use of this plant. MATERIALS AND METHODS: Through fractionation, (3'R)-hydroxytaberanelegantine C (1), a vobasinyl-iboga bisindole alkaloid, was isolated from a cytotoxic alkaloid fraction of the methanol extract of T. elegans roots. Its structure was identified by spectroscopic methods, mainly 1D and 2D NMR experiments. Compound 1 was evaluated for its ability to induce apoptosis in HCT116 and SW620 colon and HepG2 liver carcinoma cells. The cell viability of compound 1 was evaluated by the MTS and lactate dehydrogenase (LDH) assays. Induction of apoptosis was analyzed through Guava ViaCount assay, by flow cytometry, caspase-3/7 activity assays and evaluation of nuclear morphology by Hoechst staining. To determine the molecular pathways elicited by 1 exposure, immunoblot analysis was also performed. RESULTS: (3'R)-hydroxytaberanelegantine C (1) displayed strong apoptosis induction activity as compared to 5-fluorouracil (5-FU), the most used anticancer agent in colorectal cancer treatment. In the MTS assay, compound 1 exhibited IC50 values similar or lower than 5-FU in the three cell lines tested. The IC50 value of 1 was also calculated in CCD18co normal human colon fibroblasts. The lactate dehydrogenase assay showed increased LDH release by compound 1, and the Guava ViaCount assay revealed that 1 significantly increased the incidence of apoptosis to a further extent than 5-FU. Moreover, the induction of apoptosis was corroborated by evaluation of nuclear morphology by Hoechst staining and caspase-3/7 activity assays of 1 treated cells. As expected, in immunoblot analysis, compound 1 treatment led to poly(ADP-ribose) polymerase cleavage. This was accompanied by decreased anti-apoptotic proteins Bcl-2 and XIAP steady state levels in all three cancer cell lines tested. CONCLUSIONS: Compound 1 showed remarkable induction of apoptosis in HCT116, SW620 and HepG2 cells. Together, the results suggest that compound 1 is a promising lead structure for inducing apoptosis.

Triterpenoids from Momordica balsamina: Reversal of ABCB1-mediated multidrug resistance.

The ability as P-glycoprotein (P-gp, ABCB1) modulators of thirty (1-30) triterpenoids of the cucurbitane-type was evaluated on human L5178 mouse T-lymphoma cell line transfected with the human MDR1 gene, through the rhodamine-123 exclusion assay. Compounds (1-26, and 29, 30) were previously obtained from the African medicinal plant Momordica balsamina, through both isolation (1-15) and molecular derivatization (16-26 and 29, 30). Compounds 27-28 are two new karavilagenin C (34) derivatives having succinic acid moieties. Apart from 4, 6, 8, 10 and 11, most of the isolated compounds (1-15) displayed strong MDR reversing activity in a dose-dependent mode, exhibiting a many-fold activity when compared with verapamil, used as positive control. At the lowest concentration tested, compounds 2 and 7 were the most active. However, a decrease of activity was found for the acyl derivatives (16-30). In a chemosensitivity assay, the MDR reversing activity of some of the most active compounds (1-3, 5, 7, 12-15) was further assessed on the same cell model. All the tested compounds, excepting 15, corroborated the results of the transport assay, revealing to synergistically interact with doxorubicin. Structure-activity relationship studies, taking into account previous results, showed that different substitution patterns, at both the tetracyclic nucleus and the side chain, play important role in ABCB1 reversal activity. An optimal lipophilicity was also recognized.

Cleistochlamys kirkii chemical constituents: Antibacterial activity and synergistic effects against resistant Staphylococcus aureus strains.

ETHNOPHARMACOLOGICAL RELEVANCE: Cleistochlamys kirkii (Benth) Oliv., (Annonaceae) is a medicinal plant traditionally used in Mozambique to treat infectious diseases. AIMS OF THE STUDY: To find antibacterial lead compounds from C. kirkii and provide scientific validation for its use in traditional medicine. MATERIALS AND METHODS: Through bioassay-guided fractionation, nine compounds (1-9), with different scaffolds, were isolated from the methanol extract of C. kirkii whose structures were identified by spectroscopic methods. Compounds 1-9 were evaluated for their in vitro antibacterial activity against a panel of eight Gram-positive, including five drug-resistant strains of Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, and two Gram-negative bacteria strains. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. A chemosensitization assay, using the checkerboard method, was also performed in order to evaluate the type of interaction of compounds with antibiotics/compounds against two S. aureus resistant strains (ATCC 9144 and CIP 106760) and a susceptible strain (ATCC 6538). RESULTS: Dichamanetin (3), a rare C-benzylated flavanone, was very active against all the Gram-positive strains tested, displaying MIC values in the range of 1-7.5 µg/mL. The C-benzylated flavanones chamanetin (1), isochamanetin (2), and the α,ß-unsaturated lactone (-)-cleistenolide (6) also showed relevant antibacterial activity against some of the Gram-positive strains assayed. Compounds 4, 5, and 7-9 have shown no significant activity at the concentration ranges tested. In the combination with antibiotics, polycarpol (8) (MIC 125 µg/mL) showed a strong synergistic effect against the methicillin-resistant S. aureus ATCC 9144. When combined with oxacillin (MIC 125 µg/mL), compound 8 reduced the MIC to 1.5 µg/mL (FICI=0.11). Similarly, it reduced the MIC of amoxicillin (MIC 250 µg/mL) to 7.5 µg/mL (FICI=0.18). Synergy was also obtained when this compound was combined with both ß-lactam antibiotics (FICI=0.30) and with vancomycin (FICI=0.24) against vancomycin-intermediate S. aureus (VISA) CIP 106760. Remarkable, compound 8 was also able to reduce synergistically the MIC value of dichamanetin (3) (FICI=0.18) against this strain. CONCLUSIONS: These results suggested that C. kirkii constituents may be valuable as a leads for restoring antibiotic activity against resistant S. aureus strains.

In vivo evaluation of isolated triterpenes and semi-synthetic derivatives as antimalarial agents.

The triterpenes balsaminoside B (1) and karavilagenin C (2) were isolated from the African medicinal plant Momordica balsamina L. Karavoates B (3) and D (4) were synthesized by diacylation of 2 with acetic and propionic anhydrides, respectively. In previous work, derivatives 3 and 4 exhibited submicromolar median inhibitory concentrations (IC50) in vitro against Plasmodium falciparum Welch (human malaria parasite) strains 20 to 25 times lower than those of natural product 2. The main objective of the present study was to explore structure-in vivo antimalarial activity relationships (SAR) for compounds 1-4 in Plasmodium berghei Vincke and Lips NK65-infected mice in the 4 day suppressive test. Semi-synthetic derivatives 3 and 4 exhibited greater in vivo antimalarial activity than isolates 1 and 2. Orally and subcutaneously administered karavoate B exhibited the greatest in vivo antimalarial activity (55.2-58.1% maximal suppression of parasitemia at doses of 50 mg kg(-1) day(-1)). Diacylation of natural isolate 2 with short chain carboxylic acid moieties yielded derivatives with enhanced maximal in vivo parasitemia suppression for both routes of administration. Maximal in vivo parasite suppression by diacetyl derivative 3 was roughly double that of natural precursor 2.

Enhancing activity of antibiotics against Staphylococcus aureus: Zanthoxylum capense constituents and derivatives.

Six compounds (1-6), isolated from the methanol extract of the roots of the African medicinal plant Zanthoxylum capense Thunb. (Rutaceae), and seven ester derivatives (7-13) were evaluated for their antibacterial activities and modulatory effects on the MIC of antibiotics (erythromycin, oxacillin, and tetracycline) and ethidium bromide (EtBr) against a Staphylococcus aureus reference strain (ATCC 6538). Using the same model, compounds 1-13 were also assessed for their potential as efflux pump inhibitors by a fluorometric assay that measures the accumulation of the broad range efflux pump substrate EtBr. Compounds 8 and 11 were further evaluated for their antibacterial, modulatory and EtBr accumulation effects against four additional S. aureus strains, which included two clinical methicillin-resistant S. aureus (MRSA) strains. Compounds (1-13) have not shown antibacterial activity at the concentration ranges tested. When evaluated against S. aureus ATCC 6538, oxychelerythrine (1) a benzophenanthridine alkaloid, showed the highest modulatory activity enhancing the susceptibility of this strain to all the tested antibiotics from two to four-fold. Ailanthoidiol diacetate (8) and ailanthoidiol di-2-ethylbutanoate (11) were also good modulators when combined with EtBr, increasing the bacteria susceptibility by four and two-fold, respectively. In the EtBr accumulation assay, using ATCC 6538 strain, the phenylpropanoid (+)-ailanthoidiol (6) and most of its ester derivatives (8-11) exhibited higher activity than the positive control verapamil. The highest effects were found for compounds 8 and 11 that also increased the accumulation of EtBr, using S. aureus ATCC 25923 as model. Furthermore, both compounds (8, 11) were able to enhance the ciprofloxacin activity against the MRSA clinical strains tested, causing a reduction of the antibiotic MIC values from two to four-fold. The EtBr accumulation assay revealed that this modulation activity was not due to an inhibition of efflux pumps mechanism. These results suggested that Z. capense constituents may be valuable as leads for restoring antibiotic activity against MRSA strains.

Dual-stage triterpenoids from an African medicinal plant targeting the malaria parasite.

Sixteen triterpenoids (1-16), previously isolated from the aerial parts of the African medicinal plant Momordica balsamina or obtained by derivatization, were evaluated for their activity against liver stages of Plasmodium berghei, measuring the luminescence intensity in Huh-7 cells infected with a firefly luciferase-expressing P. berghei line, PbGFP-Luccon. Toxicity of compounds (1-16) was assessed on the same cell line through the fluorescence measurement of cell confluency. The highest activity was displayed by a derivative bearing two acetyl residues, karavoate B (7), which led to a dose-dependent decrease in the P. berghei infection rate, exhibiting a very significant activity at the lowest concentration employed (1 µM) and no toxicity towards the Huh-7 cells. It is noteworthy that, in previous studies, this compound was found to be a strong inhibitor of blood-stages of Plasmodium falciparum, thus displaying a dual-stage antimalarial activity.

Monoterpene bisindole alkaloids, from the African medicinal plant Tabernaemontana elegans, induce apoptosis in HCT116 human colon carcinoma cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Tabernaemontana elegans is a medicinal plant used in African traditional medicine to treat several ailments including cancer. The aims of the present study were to identify anti-cancer compounds, namely apoptosis inducers, from Tabernaemontana elegans, and hence to validate its usage in traditional medicine. METHODS AND MATERIALS: Six alkaloids, including four monomeric indole (1-3, and 6) and two bisindole (4 and 5) alkaloids, were isolated from the methanolic extract of Tabernaemontana elegans roots. The structures of these compounds were characterized by 1D and 2D NMR spectroscopic and mass spectrometric data. Compounds 1-6 along with compound 7, previously isolated from the leaves of the same species, were evaluated for in vitro cytotoxicity against HCT116 human colon carcinoma cells by the MTS metabolism assay. The cytotoxicity of the most promising compounds was corroborated by Guava-ViaCount flow cytometry assays. Selected compounds were next studied for apoptosis induction activity in HCT116 cells, by evaluation of nuclear morphology following Hoechst staining, and by caspase-3 like activity assays. RESULTS: Among the tested compounds (1-7), the bisindole alkaloids tabernaelegantine C (4) and tabernaelegantinine B (5) were found to be cytotoxic to HCT116 cells at 20 µM, with compound 5 being more cytotoxic than the positive control 5-Fluorouracil (5-FU), at a similar dose. In fact, even at 0.5 µM, compound 5 was more potent than 5-FU. Compounds 4 and 5 induced characteristic patterns of apoptosis in HCT116 cancer cells including, cell shrinkage, condensation, fragmentation of the nucleus, blebbing of the plasma membrane and chromatin condensation. Further, general caspase-3-like activity was increased in cells exposed to compounds 4 and 5, corroborating the nuclear morphology evaluation assays. CONCLUSIONS: Bisindole alkaloids tabernaelegantine C (4) and tabernaelegantinine B (5) were characterized as potent apoptosis inducers in HCT116 human colon carcinoma cells and as possible lead/scaffolds for the development of anti-cancer drugs. This study substantiates the usage of Tabernaemontana elegans in traditional medicine to treat cancer.

Apoptosis inducing activity of benzophenanthridine-type alkaloids and 2-arylbenzofuran neolignans in HCT116 colon carcinoma cells.

Thirteen compounds belonging to different classes of alkaloids (1-9) and lignans (10-13), isolated from the methanol extract of roots of the African medicinal plant Zanthoxylum capense, were assayed for their ability as apoptosis inducers in HCT116 colon carcinoma cells. The cytotoxicity of these compounds was evaluated in HCT116 colon carcinoma cells by the MTS assay. Out of the tested compounds, three benzophenanthridine alkaloids (1, 4, and 7), a dibenzyl butyrolactone lignan (10), and two 2-arylbenzofuran neolignans (12 and 13) displayed significant cytotoxicity to HCT116 cells, confirmed by the Guava ViaCount viability assay. The selected compounds (1, 4, 7, 10, 12, and 13) were further tested for apoptosis induction activity in HCT116 cells, by evaluation of nuclear morphology following Hoechst staining, and by caspase-3 like activity assays. Morphologic evaluation of HCT116 nuclei following Hoechst staining and fluorescence microscopy revealed that compounds 1, 4, 7, 10, 12, and 13 induced apoptosis in HCT116 colon carcinoma cells, producing similar, or higher, apoptosis levels when compared with 5-fluorouracil (5-FU), the cornerstone cytotoxic used in colon cancer treatment for several decades. In fact, HCT116 cells developed morphological changes characteristic of apoptosis, including chromatin condensation, nuclear fragmentation and formation of apoptotic bodies. Importantly, compounds 4 and 13 at 20 µM were the most promising in this study, inducing respectively ∼11- and 7-fold increases in apoptotic cells as compared to vehicle control, whereas 5-FU increased apoptosis by ∼2-fold. Apoptosis induction for compounds 4 and 13 was further confirmed by caspase-3-like activity assays, which showed respectively ∼2- and 1.5-fold increases in caspase-3-like activity compared to vehicle control. These results suggested that specific benzophenanthridine alkaloids and 2-arylbenzofuran neolignans isolated from Zanthoxylum capense show strong anticancer activity in HCT116 colon carcinoma cells.

Zanthoxylum capense constituents with antimycobacterial activity against Mycobacterium tuberculosis in vitro and ex vivo within human macrophages.

ETHNOPHARMACOLOGICAL RELEVANCE: Zanthoxylum capense Thunb. (Rutaceae) is a medicinal plant traditionally used in Mozambique to treat tuberculosis. AIMS OF THE STUDY: The main aim of the study was to find antimycobacterial lead compounds from Zanthoxylum capense. Another goal was to provide scientific validation for the use of this plant in traditional medicine. METHODS AND MATERIALS: By bioassay-guided fractionation, 16 compounds were isolated and screened for their in vitro antimycobacterial activity against two different strains of Mycobacterium tuberculosis. Their in vitro cytotoxicity to human THP-1 macrophages was also assessed. The compounds with favourable selectivity index values (SI>10) were further investigated for their ability to inhibit the growth of Mycobacterium tuberculosis H37Rv in an intracellular macrophage model of infection. RESULTS: The best results were obtained for a benzophenanthridine alkaloid, decarine (1), and an N-isobutylamide, N-isobutyl-(2E,4E)-2,4-tetradecadienamide (15), which showed high activity against Mycobacterium tuberculosis H37Rv (MIC of 1.6 µg/ml), and a low macrophage cytotoxicity (IC50>60 µg/ml), indicating considerable selective activity. The benzophenanthridine alkaloid 6-acetonyldihydronitidine (6) revealed cytotoxicity (IC50 1.7 µg/ml), despite the determined MIC of 6.2-12.5 µg/ml. In infected macrophages, decarine (1) was able to reduce bacterial survival by almost two log units at a concentration of 6.2 µg/ml 5 days post-drug exposure. Compound 15 exhibited an intermediate activity at drug concentrations ranging from 6.2 to 25 µg/ml. CONCLUSIONS: The high antimycobacterial activity of decarine found, both in vitro and ex vivo against mycobacteria, and the low cytotoxicity towards human macrophages indicate that it may be valuable as a lead scaffold for the development of anti-TB drugs.

In vitro schistosomicidal activity of balsaminol F and karavilagenin C.

Five cucurbitane-type triterpenes (1-5), previously isolated from the African medicinal plant Momordica balsamina, along with five ester derivatives (6-10) of karavilagenin C (2), were evaluated for their potential schistosomicidal activity against Schistosoma mansoni adult worms. The natural compounds were isolated from the ethyl acetate-soluble fraction of the methanol extract of the aerial parts of M. balsamina. In a preliminary study, a significant schistosomicidal activity was observed for both the crude methanol extract and the ethyl acetate fraction. The compounds responsible for the activity were found to be balsaminol F (1) and karavilagenin C (2) with LC50 values of 14.7 ± 1.5 and 28.9 ± 1.8 µM, respectively, after 24 h of incubation (positive control praziquantel, LC50 = 1.2 ± 0.1 µM). Both compounds (1, 2), at 10-50 µM, induced significant reductions in the motor activity of the worms and significantly decreased the egg production. Furthermore, they were able (at 10-100 µM) to separate the adult worm pairs into male and female after 24 h. Compounds 3-5, bearing a sugar moiety as a substituent, and the acylated derivatives of karavilagenin C (6-10) were inactive, suggesting that the presence of free hydroxyl groups in the tetracyclic skeleton might be important for the activity. A correlation between activity and the molecular volume/weight of compounds was also found.

Antibacterial benzofuran neolignans and benzophenanthridine alkaloids from the roots of Zanthoxylum capense.

Two new 2-arylbenzofuran neolignans and a new benzophenanthridine alkaloid, together with six known benzophenanthridine alkaloids, namely, decarine, norchelerythrine, dihydrochelerythrine, 6-acetonyldihydrochelerythrine, tridecanonchelerythrine, and 6-acetonyldihydronitidine, have been isolated from the MeOH extract of the roots of Zanthoxylum capense. Their structures were elucidated by means of spectroscopic techniques including 2D NMR experiments. All the isolated compounds were evaluated for their in vitro antibacterial activity against gram-positive and gram-negative bacteria. Some compounds showed significant inhibitory activity against Staphylococcus aureus ATCC 6538 with MIC values ranging from 12.5 to 50 µg/mL.

Antibacterial activity of some African medicinal plants used traditionally against infectious diseases.

CONTEXT: Plants are known to play a crucial role in African traditional medicine for the treatment of infection diseases. OBJECTIVES: To investigate the claimed antimicrobial properties of plants traditionally used in African countries, providing scientific validation for their use. MATERIALS AND METHODS: Eighty-three polar and non-polar extracts from 22 medicinal plants were screened for their antibacterial activity against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae) and Mycobacterium smegmatis using the broth microdilution method. RESULTS AND DISCUSSION: In vitro antibacterial activity against one or more tested bacteria was shown by 83% of the extracts. The highest activity was obtained with the methanol extracts of the aerial parts of Acacia karroo Hayne (Fabaceae) and Anacardium occidentale L. (Anacardiaceae) and the roots of Bridelia cathartica G. Bertol (Euphorbiaceae), against S. aureus (minimum inhibitory concentration (MIC) = 7.5 µg/mL). The same MIC values were exhibited against E. faecalis by the methanol extract of A. occidentale, the dichloromethane and methanol extracts of B. cathartica and the ethyl acetate extract of Momordica balsamina l. (Curcubitaceae) leaves. Gram-negative bacteria were less sensitive; the growth of P. aeruginosa was significantly inhibited (MIC = 31 µg/mL) by the n-hexane and methanol extracts of Gomphocarpus fruticosus (l.) Ait. (Asclepiadaceae) fruits and by the dichloromethane extract of Trichilia emetica Vahl (Meliaceae) seeds. Most of the active extracts were rich in fenols/flavonoids. CONCLUSION: This study supports the use of most of the studied plants in traditional medicine, for the treatment of infectious diseases. Some of them are worthy of further investigation.

Antimycobacterial evaluation and preliminary phytochemical investigation of selected medicinal plants traditionally used in Mozambique.

ETHNOPHARMACOLOGICAL RELEVANCE: Several medicinal plants are traditionally used in Mozambique to treat tuberculosis and related symptoms. AIMS OF THE STUDY: It was aimed to assess the in vitro antimycobacterial activity of crude extracts from fifteen medicinal plants and to reveal main classes of compounds which may account for the activity of extracts. METHODS AND MATERIALS: The plant materials were sequentially extracted by n-hexane, dichloromethane, ethyl acetate, and 70% ethanol. Decoction of each plant material was also prepared according to traditional use. Broth microdilution method was employed to screen extracts against two mycobacterial species: Mycobacterium smegmatis ATCC 607 and Mycobacterium tuberculosis H37Rv. The extracts with minimum inhibitory concentration(s) (MIC) below 125 µg/mL were considered active and further tested against different mycobacterial species and strains, namely Mycobacterium tuberculosis H37Ra, Mycobacterium bovis BCG ATCC 35734, Mycobacterium smegmatis mc(2) 155, Mycobacterium avium DSM 44156 and DSM 44157. Cytotoxic effect was evaluated against human macrophages from the monocytic THP-1 cells. Main classes of compounds in these active extracts were proposed from their (1)H NMR spectroscopic characterizations. RESULTS: n-Hexane extracts of Maerua edulis and Securidaca longepedunculata, ethyl acetate extract of Tabernaemontana elegans and dichloromethane extract of Zanthoxylum capense were found to possess considerable activity against Mycobacterium bovis BCG and Mycobacterium tuberculosis H37Ra with MIC 15.6-62.5 µg/mL. Tabernaemontana elegans ethyl acetate extract displayed strong activity against Mycobacterium tuberculosis H37Rv (MIC 15.6 µg/mL). Except for Tabernaemontana elegans ethyl acetate extract which presented potent cytotoxic effects in THP-1 cells (IC(50)<4 µg/mL), the other three plant extracts showed moderate to none toxicity. Based on (1)H NMR spectroscopic analysis, major components in both Maerua edulis and Securidaca longepedunculata n-hexane extracts were linear chain unsaturated fatty acids. Zanthoxylum capense dichloromethane extract contained more complex constituents (mostly phenolic compounds). In the most potent extract, Tabernaemontana elegans ethyl acetate extract, the prominent compounds were identified as indole alkaloids. CONCLUSIONS: The pronounced antimycobacterial activity of the medicinal plants Maerua edulis, Securidaca longepedunculata, Zanthoxylum capense, and Tabernaemontana elegans suggested that they might provide compounds which could be potential anti-TB drug leads.

Substrates and modulators of the multidrug transporter Cdr1p of Candida albicans in antifungal extracts of medicinal plants.

The effective treatment of infections caused by the most frequent human fungal pathogens Candida albicans and Candida glabrata is hindered by a limited number of available antifungals and development of resistance. In this study, we identified new extracts of medicinal plants inhibiting the growth of C. glabrata, a species generally showing low sensitivity to azoles. The methanolic extract of Anacardium occidentalis with an MIC of 80 microg ml(-1) proved to be the most active. In contrast to higher azole sensitivity, C. albicans showed increased resistance to several extracts. Investigation of the possible contribution of the multidrug transporter of the ATP-binding cassette superfamily Cdr1p of C. albicans to extract tolerance revealed a differential response upon overproduction of this protein in Saccharaomyces cerevisiae. Whereas the growth inhibitory activity of many extracts was not affected by CDR1 overexpression, increased sensitivity to some of them was observed. In contrast, extracts showing no detectable anticandidal activity including the ethyl acetate extract of Trichilia emetica were detoxified by Cdr1p. The presence of a non-toxic Cdr1p-mediated ketoconazole resistance modulator accompanying growth-inhibitory Cdr1p substrates in this extract was revealed by further fractionation experiments.

Induction of apoptosis in HuH-7 cancer cells by monoterpene and beta-carboline indole alkaloids isolated from the leaves of Tabernaemontana elegans.

Three known (1-3) and a novel (4) monoterpene indole alkaloids have been isolated from the methanol extract of leaves of Tabernaemontana elegans and their structures were elucidated by a series of spectroscopic experiments, involving NMR, MS, UV, and IR techniques. The isolated monoterpene indole alkaloids along with previously described beta-carbolines (5-7) from the same specimen were studied for their apoptosis induction activity in human hepatoma HuH-7 cells. Methodology for apoptosis induction studies included cell viability assays, nuclear morphology assessments, and general caspase-3-like activity assays. The monoterpene indole alkaloids, tabernaemontanine (1) and vobasine (3) showed the most promising apoptosis induction profile in HuH-7 cells.