Identification of Antifungal Bisphosphocholines from Medicinal Gentiana Species.

Gentiana species including G. crassicaulis, G. macrophylla, G. dahurica, and G. straminea are used in traditional Chinese medicine as "Qinjiao" for the treatment of rheumatism, hepatitis, and pain. Four antifungal bisphosphocholines [irlbacholine (2) and three new analogues, gentianalines A-C (1, 3, and 4)] were identified from G. crassicaulis by a bioassay-guided fractionation and structure elucidation approach. Subsequent chemical analysis of 56 "Qinjiao" samples (45 from G. crassicaulis, five from G. macrophylla, three from G. dahurica, and three from G. straminea) showed that bisphosphocholines were present in all four Gentiana species, with irlbacholine as the major compound ranging from 2.0 to 6.2 mg per gram of dried material. Irlbacholine exhibited potent in vitro antifungal activity against Cryptococcus neoformans, Aspergillus fumigatus, Candida albicans, and Candida glabrata with minimum inhibitory concentration (MIC) values of 0.63, 1.25, 10.0, and 5.0 µg/mL, respectively. Identification of the bisphosphocholines, a rare class of antifungal natural products, in these medicinal plants provides scientific evidence to complement their medicinal use. The bisphosphocholines carrying a long aliphatic chain possess amphiphilic molecule-like properties with a tendency of retention in both normal and reversed-phase silica gel column chromatography and thereby may be neglected in natural products discovery. This report may stimulate interest in this class of compounds, which warrant the further study of other biological activities as well.

Protocol for Identifying Natural Agents That Selectively Affect Adhesion, Thickness, Architecture, Cellular Phenotypes, Extracellular Matrix, and Human White Blood Cell Impenetrability of Candida albicans Biofilms.

In the screening of natural plant extracts for antifungal activity, assessment of their effects on the growth of cells in suspension or in the wells of microtiter plates is expedient. However, microorganisms, including Candida albicans, grow in nature as biofilms, which are organized cellular communities with a complex architecture capable of conditioning their microenvironment, communicating, and excluding low- and high-molecular-weight molecules and white blood cells. Here, a confocal laser scanning microscopy (CLSM) protocol for testing the effects of large numbers of agents on biofilm development is described. The protocol assessed nine parameters from a single z-stack series of CLSM scans for each individual biofilm analyzed. The parameters included adhesion, thickness, formation of a basal yeast cell polylayer, hypha formation, the vertical orientation of hyphae, the hyphal bend point, pseudohypha formation, calcofluor white staining of the extracellular matrix (ECM), and human white blood cell impenetrability. The protocol was applied first to five plant extracts and derivative compounds and then to a collection of 88 previously untested plant extracts. They were found to cause a variety of phenotypic profiles, as was the case for 64 of the 88 extracts (73%). Half of the 46 extracts that did not affect biofilm thickness affected other biofilm parameters. Correlations between specific effects were revealed. The protocol will be useful not only in the screening of chemical libraries but also in the analysis of compounds with known effects and mutations.

Antifungal Amide Alkaloids from the Aerial Parts of Piper flaviflorum and Piper sarmentosum.

Sixty-three amide alkaloids, including three new, piperflaviflorine A (1), piperflaviflorine B (2), and sarmentamide D (4), and two previously synthesized ones, (1E,3S)-1-cinnamoyl-3- hydroxypyrrolidine (3) and N-[7'-(4'-methoxyphenyl)ethyl]-2-methoxybenzamide (5), were isolated from the aerial parts of Piper flaviflorum and Piper sarmentosum. Their structures were elucidated by detailed spectroscopic analysis and, in case of 3, by single-crystal X-ray diffraction. Most of the isolates were tested for their antifungal and antibacterial activities. Ten amides (6-15) showed antifungal activity against Cryptococcus neoformans ATCC 90 113 with IC50 values in the range between 4.7 and 20.0 µg/mL.

Biological evaluation of phytoconstituents from Polygonum hydropiper.

Fourteen compounds including vanicoside B (1), vanicoside F (2), vanicoside E (3) and 5,6-dehydrokawain (4), aniba-dimer-A (5), 6,6'-((1α,2α,3ß,4ß)-2,4-diphenylcyclobutane-1,3-diyl)bis(4-methoxy-2H-pyran-2-one) (6), (+)-ketopinoresinol (7), isorhamnetin (8), 3,7-dihydroxy-5,6-dimethoxy-flavone (9), isalpinin (10), cardamomin (11), pinosylvin (12), 2-desoxy-4-epi-pulchellin (13) and ß-sitosterol (14) were isolated from dichloromethane-soluble portion of Polygonum hydropiper. By using Alamar blue assay, compounds 2, 7, 8, 11 and 12 were found to be active against Trypanosoma brucei with IC50 values in the range of 0.49-7.77 µg/mL. Cardamomin (11) had most significant activity against T. brucei with IC50/IC90 values of 0.49/0.81 µg/mL compared to the positive control DFMO (IC50/IC90: 3.02/8.05 µg/mL). Furthermore, in antimalarial, antimicrobial, anti-inflammatory, PPAR and cytotoxic assays, some compounds have demonstrated moderate inhibitory potentials.

New ent-Clerodane and Abietane Diterpenoids from the Roots of Kenyan Croton megalocarpoides Friis & M. G. Gilbert.

The roots of the endangered medicinal plant Croton megalocarpoides collected in Kenya were investigated and twenty-two compounds isolated. Among them were twelve new ent-clerodane (1-12) and a new abietane (13) diterpenoids, alongside the known crotocorylifuran (4 a), two known abietane and four known ent-trachylobane diterpenoids, and the triterpenoids, lupeol and acetyl aleurotolic acid. The structures of the compounds were determined using NMR, HRMS and ECD. The isolated compounds were evaluated against a series of microorganisms (fungal and bacteria) and also against Plasmodium falciparum, however no activity was observed.

Diversity-oriented natural product platform identifies plant constituents targeting Plasmodium falciparum.

BACKGROUND: A diverse library of pre-fractionated plant extracts, generated by an automated high-throughput system, was tested using an in vitro anti-malarial screening platform to identify known or new natural products for lead development. The platform identifies hits on the basis of in vitro growth inhibition of Plasmodium falciparum and counter-screens for cytotoxicity to human foreskin fibroblast or embryonic kidney cell lines. The physical library was supplemented by early-stage collection of analytical data for each fraction to aid rapid identification of the active components within each screening hit. RESULTS: A total of 16,177 fractions from 1300 plants were screened, identifying several P. falciparum inhibitory fractions from 35 plants. Although individual fractions were screened for bioactivity to ensure adequate signal in the analytical characterizations, fractions containing less than 2.0 mg of dry weight were combined to produce combined fractions (COMBIs). Fractions of active COMBIs had EC50 values of 0.21-50.28 and 0.08-20.04 µg/mL against chloroquine-sensitive and -resistant strains, respectively. In Berberis thunbergii, eight known alkaloids were dereplicated quickly from its COMBIs, but berberine was the most-active constituent against P. falciparum. The triterpenoids α-betulinic acid and ß-betulinic acid of Eugenia rigida were also isolated as hits. Validation of the anti-malarial discovery platform was confirmed by these scaled isolations from B. thunbergii and E. rigida. CONCLUSIONS: These results demonstrate the value of curating and exploring a library of natural products for small molecule drug discovery. Attention given to the diversity of plant species represented in the library, focus on practical analytical data collection, and the use of counter-screens all facilitate the identification of anti-malarial compounds for lead development or new tools for chemical biology.

Antimicrobial and Antileishmanial Activities of Diterpenoids Isolated from the Roots of Salvia deserta.

Four diterpenes with biological activity were isolated from Salvia deserta roots. Taxodione was considered leishmanicidal with an IC50 value of 1.46 µM (0.46 mg/L) against Leishmania donovani and also exhibited antifungal and antimicrobial activities. Ferruginol displayed the greatest activity [24-h IC50 of 4.5 µM (1.29 mg/L)] against the fish pathogenic bacteria Streptococcus iniae. The crude extract fraction that contained the isolated compounds 7-O-acetylhorminone and horminone showed stronger in vitro antibacterial activity (1.3 mg/L for Staphylococcus aureus and 1.1 mg/L for methicillin-resistant S. aureus) than the compounds tested alone. 7-O-Acetylhorminone and horminone exhibited a synergistic effect against methicillin-resistant S. aureus (FIC of 0.2), and horminone had better activity against S. aureus with respect to other compounds isolated from S. deserta roots. In larvicidal bioassays, these extracts and isolated pure compounds did not show any activity at the highest dose of 125 mg/L against 1-d-old Aedes aegypti larvae.

Anti-vancomycin-resistant Enterococcus faecium and E. faecalis activities of (-)-gossypol and derivatives from Thespesia garckeana.

The root extract of Thespesia garckeana yielded three known oxidatively coupled sesquiterpenoids, namely (-)-gossypol (1) and two of its derivatives (-)-6-methoxygossypol (2) and (+)-6,6'-dimethoxygossypol (3), and the stem bark afforded (E)-docosyl-3-(3,4-dihydroxyphenyl) acrylate (4), stigmasterol (5) and betulinic acid (6). The structures of the isolated compounds were determined on the basis of full spectral data (1D and 2D NMR and HRMS) and comparison with literature values. Compound 1 showed potent antibacterial activity against vancomycin-resistant Enterococcus faecium (VRE) with IC50/MIC/MBC values of 1.71/4.82/19.31 µM, respectively, whereas the reference standard vancomycin was found to be inactive. The mono- and di-methoxylated derivatives of this compound, (-)-6-methoxygossypol (2) and (+)-6,6'-dimethoxygossypol (3), were less active with respective IC50/MIC/MBC values of 2.73/4.70/9.40 µM and 6.14/18.32/18.32 µM against this microbe. Compound 2 was more potent than 1 against the low level VRE strain with I50/MIC/MBC values of 4.34/9.40/9.40 µM (vs 5.23/19.31/19.3 µM for 1). This compound also showed interesting activities against Candida glabrata with an I50 value of 2.97 µM, but was less active against methicillin-resistant S. aureus (MRSA) exhibiting an IC50 value of 17.33 µM. Compound 1 demonstrated modest activity against the

Evaluation of three medicinal plant extracts against Plasmodium falciparum and selected microganisms.

BACKGROUND: A great revival of scientific interests in drug discovery has been witnessed in recent years from medicinal plants for health maintenance. The aim of this work was to investigate three Nigerian medicinal plants collected in Nigeria for their in vitro antiplasmodial and antimicrobial activities. MATERIALS AND METHODS: Extracts obtained from parts of Persea americana, Jatropha podagrica and Picralima nitida and their fractions were evaluated for in vitro antiprotozoal and antimicrobial activity. RESULT: The methanol extract of P. nitida demonstrated activity against chloroquine-sensitive and chloroquine-resistant P. falciparum clones with IC50 values of 6.3 and 6.0 µg/mL, respectively. Methanol and chloroform extracts of P. americana seed showed antifungal activity against Cryptococcus neoformans IC50 less than 8 and 8.211 µg/mL respectively. Finally, the petroleum ether extract of P. americana had activity against methicillin-resistant Staphylococcus aureus (MRSA) with an IC50 value of 8.7 µg/mL. CONCLUSION: The study revealed the antibacterial and antiplasmodial activities of the plants extracts at the tested concentrations.

Methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis and Enterococcus faecium active dimeric isobutyrylphloroglucinol from Ivesia gordonii.

Bioassay-guided fractionation of the chloroform soluble fraction of stem, leaf, and flower extracts of the American plant Ivesia gordonii led to the isolation of a new dimeric acylphloroglucinol, 3,3'-diisobutyryl-2,6'-dimethoxy-4,6,2',4'-tetrahydroxy-5,5'dimethyldiphenyl methane (1), to which we have assigned the trivial name ofivesinol (1), together with a known monomeric acylphloroglucinol, 1,5-dihydroxy-2-(2'-methylpropionyl)-3-methoxy-6-methylbenzene (2). The structures of the isolated compounds were characterized using 1D- and 2D- NMR spectroscopy, including COSY, HMQC, HMBC, and ROESYexperiments, as well as mass spectrometry. Ivesinol (1) showed potent activity against Staphylococcus aureus (SA) and methicillin-resistant S. aureus (MRSA) with IC50/MIC/MBC values of 0.10/1.25/>20 microg/mL and 0.05/0.31/>20 microg/mL, respectively (vs. IC50/MIC/MBC 0.13/0.5/1.0 microg/mL and 0.13/0.5/1.0 microg/mL of ciprofloxacin), while the corresponding monomer 2 was found to be less active. Compound 1 also demonstrated strong activity against vancomycin-resistant Enterococcus faecium (VRE) with IC50/MlC/MBC values of 0.22/1.25/>20 microg/mL, whereas the reference standard ciprofloxacin was found to be inactive against this strain. In addition, compound 2 showed moderate activity against two species of Candida and Cryptococcus neoformans, while 1 was inactive against these fungi. In order to evaluate the influence of the acyl group(s) in phloroglucinol (3) as a ligand, the mono- (4) and diacetylphloroglucinol (5) were prepared from 3, and evaluated for their in vitro SA, MRSA, and VRE activities; 2,4-diacetylphloroglucinol (5) showed potent activity, like 1, against SA, MRSA, and VRE (ATCC 700221) with IC50/MIC values of 0.3/2.5, 0.23/2.5, and 0.86/2.5 microg/mL, respectively, while 4 was inactive.

Phytochemical, Antimicrobial and Antiplasmodial Investigations of Terminalia brownii.

Phytochemical investigation of the ethyl acetate-soluble fraction of stem bark extract of an African medicinal plant Terminalia brownii led to the isolation of a new oleanane-type triterpenoid, along with seven known triterpenoids, seven ellagic acid derivatives, and 3-O-ß-D-glucopyranosyl-ß-sitosterol. The new compound was identified using spectroscopic methods, notably 1D- and 2D NMR, as 3ß,24-O-ethylidenyl-2α,19α-dihydroxyolean-12-en-28-oic acid. The isolated compounds were evaluated for their antimicrobial and antiplasmodial activities. Two compounds with a galloyl group (4 and 6) were found to be active against chloroquine sensitive (D6) and chloroquine resistant (W2) strains of Plasmodium falciparum, whereas three ellagic acid derivatives (5-7) were found active against three species of fungi and one species of bacteria.

Pentacyclic ingamine alkaloids, a new antiplasmodial pharmacophore from the marine sponge Petrosid Ng5 Sp5.

Two new pentacyclic ingamine alkaloids, namely 22(S)-hydroxyingamine A (2) and dihydroingenamine D (3), together with the known ingamine A (1), have been isolated from marine sponge Petrosid Ng5 Sp5 (family Petrosiidae) obtained from the open repository of the National Cancer Institute, USA. The structures of compounds 1-3 were determined using 1D and 2D NMR, and HRESIMS techniques. The absolute configuration of both the C9 and C22 of 2 was determined as (S) using a modified Mosher esterification method. Compounds 1 and 3 showed strong antiplasmodial activity against chloroquine-sensitive (D6) and -resistant (W2) strains of Plasmodium falciparum with IC50 values of 90 and 78 ng/mL and 72 and 57 ng/mL, respectively, while 2 was found to be less active (IC50 values of 200 and 140 ng/mL, respectively). Compounds 1-3 were found to be devoid of in vitro cytotoxicity against human solid tumor cells of breast (BT-549), ovary (SK-OV-3), and epidermoid (KB) carcinomas and skin melanoma (SK-MEL), as well as against noncancerous monkey kidney fibroblasts (VERO) and pig kidney epithelial (LLC-PK11) cells, up to a maximum concentration of 10 µg/mL. Compounds 1-3 also displayed weak antimicrobial and moderate antileishmanial activities against Leishmania donovani promastigotes. These polycyclic ingamine alkaloids represent the first example of antiplasmodial leads without a ß-carboline ring, which is known to be responsible for the cytotoxicity of the well-known manzamine class of marine alkaloids related to 1-3.

Antiparasitic and antimicrobial indolizidines from the leaves of Prosopis glandulosa var. glandulosa.

A new indolizidine alkaloid, named Δ¹,6-juliprosopine (1), together with previously known indolizidine analogs (2- 6), was isolated from the leaves of Prosopis glandulosa var. glandulosa, collected from Nevada, USA; while two other known indolizidines, juliprosopine (6) and juliprosine (7), were isolated from P. glandulosa leaves collected in Texas, USA. The structures of compound 1 and 7 were determined using a combination of NMR and MS techniques. Compound 7 exhibited potent antiplasmodial activity against Plasmodium falciparum D6 and W2 strains with IC (50) values of 170 and 150 ng/mL, respectively, while 1 was found to be less active (IC50 values 560 and 600 ng/mL, respectively). Both compounds were devoid of VERO cells toxicity up to a concentration of 23 800 ng/mL. The antileishmanial activity of indolizidines was evaluated against Leishmania donovani promastigotes, axenic amastigotes, and amastigotes in THP1 macrophage cultures. When tested against macrophage cultures, the tertiary bases (1, 3, 6) were found to be more potent than quaternary salts (2, 5, 7), displaying IC50 values between 0.8-1.7 µg/mL and 3.1-6.0 µg/mL, respectively. In addition, compound 7 showed potent antifungal activity against Cryptococcus neoformans and antibacterial activity against Mycobacterium intracellulare, while 1 was potent only against C. neoformans and weakly active against other organisms.

Antiparasitic and antimicrobial isoflavanquinones from Abrus schimperi.

The EtOH extract of Abrus schimperi (Fabaceae), collected in Kenya, demonstrated significant activity against Leishmania donovani promastigotes with IC50 value of 3.6 microg/mL. Bioassay-guided fractionation of CHCl3 fraction using Centrifugal Preparative TLC afforded two antiparasitic isoflavanquinones, namely amorphaquinone (1) and pendulone (2). They displayed IC50 values of 0.63 microg/mL and 0.43 microg/mL, respectively, against L. donovani promastigotes. Both the compounds were also evaluated against L. donovani axenic amastigotes and amastigotes in THPI macrophage cultures. In addition, compounds 1 and 2 showed antiplasmodial activity against Plasmodium falciparum D6 and W2 strains, while 2 displayed antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus (each IC50 1.44 microg/mL). The 1H and 13C data of 1, not fully assigned previously, were unambiguously assigned using 1D and 2D NMR HMBC and HMQC experiments. In addition, the absolute stereochemistry of the isolated compounds 1 and 2 was revised as C-(3S) based on Circular Dichroism experiments. This appears to be the first report of amorphaquinone (1) and pendulone (2) from the genus Abrus.

Steroidal saponins from fresh stems of Dracaena angustifolia.

Six new steroidal saponins (1-6), angudracanosides A-F, were isolated from fresh stems of Dracaena angustifolia, together with eight known compounds. The structures of compounds 1-6 were determined by detailed spectroscopic analyses and chemical methods. Antifungal testing of all compounds showed that 6 and 7 were active against Cryptococcus neoformans with IC(50)s of 9.5 and 20.0 µg/mL, respectively.

Antimicrobial and antiparasitic abietane diterpenoids from the roots of Clerodendrum eriophyllum.

Chromatographic separation of the roots of a Kenyan medicinal plant, Clerodendrum eriophyllum, led to the isolation of ten abietane diterpenoids (1-10), one of which (1) was isolated for the first time from a natural source. Using spectroscopic data, the structure of 1 was determined to be 12-hydroxy-8,12-abietadiene-3,11,14-trione. Circular dichroism (CD) spectra showed that the stereochemistry of compounds 1, 3, and 6-8 belongs to the normal series of abietane diterpenes, which confirmed the absolute stereochemistry of the isolated compounds. Compounds 1-10 were evaluated for their in vitro antiplasmodial, antileishmanial, antifungal and antibacterial activities. Compounds 3 and 7 exhibited potent antifungal activity (IC50/MIC 0.58/1.25 and 0.96/2.5 microg/mL, respectively) against C. neoformans, whereas 3, 6 and 7 showed strong antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus with IC50/MIC values between 1.33-1.75/2.5-5 and 0.96-1.56/2.5 microg/mL, respectively. In addition, compounds 3 and 9 exhibited potent antileishmanial activity (IC50 0.08 and 0.20 microg/mL, respectively) against L. donovani, while 3 and 7 displayed weak antimalarial activity against Plasmodium falciparum, but 9 was inactive.

Phytochemical investigation of Cycas circinalis and Cycas revoluta leaflets: moderately active antibacterial biflavonoids.

Chemical examination of the methanolic extract of the leaflets of CYCAS CIRCINALIS L. led to the isolation of one new biflavonoid, (2 S, 2'' S)-2,3,2'',3''-tetrahydro-4',4'''-di- O-methylamentoflavone (tetrahydroisoginkgetin; 2), and 15 known compounds, 11 of which are reported for the first time from C. CIRCINALIS. Chromatographic separation of the chloroform extract of C. REVOLUTA Thunb. leaflets afforded 12 compounds, seven of which are reported for the first time from this species. The isolated compounds from both species include 14 biflavonoids, three lignans, three flavan-3-ols, two flavone- C-glucosides, two NOR-isoprenoids, and one flavanone. This is the first report of NMR and CD data of 2,3,2'',3''-tetrahydro-4'- O-methyl- and 2,3-dihydro-4'- O-methyl-amentoflavone ( 6) and ( 7). The effect of O-methylation on the chemical shifts of the neighboring carbons in the (13)C NMR spectra of the dihydro- and tetrahydro-amentoflavone skeletons provides a tool to identify the location of the methoxy groups. Compounds 2, 6, and 18 displayed moderate antibacterial activity against STAPHYLOCOCCUS AUREUS (IC (50) values of 3.9, 9.7, and 8.2 microM, respectively) and methicillin-resistant S. AUREUS (MRSA; IC (50) values of 5.9, 12.5, and 11.5 microM, respectively).

Antimicrobial, antiparasitic and cytotoxic spermine alkaloids from Albizia schimperiana.

Albizia schimperiana Oliv. (Leguminosae) is a tree distributed in the highland of Kenya, where it is used as a traditional medicine for the treatment of bacterial and parasitic infections, notably pneumonia and malaria, respectively. Bioassay guided isolation of the CH2Cl2-MeOH 1:1/ MeOH-H20 9:1 (mixed) extract of A. schimperiana afforded the new bioactive macrocyclic spermine alkaloid, namely 5,14-dimethylbudmunchiamine L1 (1) and three known budmunchiamine analogs 2-4. The structures of the compounds 1-4 were determined by 1D and 2D NMR data, including COSY, HMQC, and HMBC experiments, and ESI-HRMS. Compounds 1 and 3 exhibited significant in vitro antimicrobial activity against a panel of microorganisms, including C neoformans, methicillin-resistant S. aureus, E. coli, M. intracellulare, and A. fumigatus. In Saddition, they demonstrated strong in vitro antimalarial activities against chloroquine-susceptible (D6) and -resistant (W2) strains of Plasmodium falciparum with IC50s ranging from 120-270 ng/mL. Compounds 1-4 were also evaluated for cytotoxic activity against selected human cancer cell lines and mammalian kidney fibroblasts (VERO cells). It was observed that hydroxyl substitution of the side chain of the budmunchiamines dramatically reduced the cytotoxicity and antimicrobial activity of the alkaloids 2 and 4 without decreasing antimalarial activity.

Indolizidine, antiinfective and antiparasitic compounds from Prosopis glandulosa var. glandulosa.

A new potent antiinfective and antiparasitic 2,3-dihydro-1H-indolizinium chloride (1) was isolated from Prosopis glandulosa var. glandulosa. Three additional new (2-4) and one known (5) indolizidines were also isolated, and the dihydrochloride salts of 1-3 (compounds 6, 7, and 8) were prepared. Structures were determined by 1D and 2D NMR and mass spectra. Compound 1 showed potent in vitro antifungal activity against Cryptococcus neoformans and Aspergillus fumigatus (IC(50) values = 0.4 and 3.0 microg/mL, respectively) and antibacterial activity against methicillin-resistant Staphylococcus aureus and Mycobacterium intracellulare (IC(50) values of 0.35 and 0.9 microg/mL, respectively). The remarkable in vitro fungicidal activity of 1-4 against C. neoformans (MFCs = 0.63-1.25 microg/mL) and 2, 3, and 5 against A. fumigatus (MFCs = 0.63-2.5 microg/mL) were similar to amphotericin B, but >2-4-fold more potent than 6-8. Prosopilosidine (1) showed potent in vivo activity at 0.0625 mg/kg/day/ip for 5 days in a murine model of cryptococcosis by eliminating approximately 76% of C. neoformans infection from brain tissue compared to approximately 83% with amphotericin B at 1.5 mg/kg/day. Compounds 1 and 4 exhibited potent activity and high selectivity index (SI) values against chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum, with IC(50) values of 39 and 95 ng/mL and 42 and 120 ng/mL, respectively (chloroquine, IC(50) = 17 and 140 ng/mL). Prosopilosine (1) also showed in vivo antimalarial activity, with an ED(50) value of approximately 2 mg/kg/day/ip against Plasmodium berghei-infected mice after 3 days of treatment.

Potent in vitro antifungal activities of naturally occurring acetylenic acids.

Our continuing effort in antifungal natural product discovery has led to the identification of five 6-acetylenic acids with chain lengths from C(16) to C(20): 6-hexadecynoic acid (compound 1), 6-heptadecynoic acid (compound 2), 6-octadecynoic acid (compound 3), 6-nonadecynoic acid (compound 4), and 6-icosynoic acid (compound 5) from the plant Sommera sabiceoides. Compounds 2 and 5 represent newly isolated fatty acids. The five acetylenic acids were evaluated for their in vitro antifungal activities against Candida albicans, Candida glabrata, Candida krusei, Candida tropicalis, Candida parapsilosis, Cryptococcus neoformans, Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Trichophyton mentagrophytes, and Trichophyton rubrum by comparison with the positive control drugs amphotericin B, fluconazole, ketoconazole, caspofungin, terbinafine, and undecylenic acid. The compounds showed various degrees of antifungal activity against the 21 tested strains. Compound 4 was the most active, in particular against the dermatophytes T. mentagrophytes and T. rubrum and the opportunistic pathogens C. albicans and A. fumigatus, with MICs comparable to several control drugs. Inclusion of two commercially available acetylenic acids, 9-octadecynoic acid (compound 6) and 5,8,11,14-eicosatetraynoic acid (compound 7), in the in vitro antifungal testing further demonstrated that the antifungal activities of the acetylenic acids were associated with their chain lengths and positional triple bonds. In vitro toxicity testing against mammalian cell lines indicated that compounds 1 to 5 were not toxic at concentrations up to 32 muM. Furthermore, compounds 3 and 4 did not produce obvious toxic effects in mice at a dose of 34 mumol/kg of body weight when administered intraperitoneally. Taking into account the low in vitro and in vivo toxicities and significant antifungal potencies, these 6-acetylenic acids may be excellent leads for further preclinical studies.