Synthesis and biological evaluation of 12 novel (-)-camphene-based 1,3,4-thiadiazoles against Mycobacterium tuberculosis.

Aim: To evaluate the activity, cytotoxicity and efflux pumps inhibition of a series of 12 novels (-)-camphene-based 1,3,4-thiadiazoles (TDZs) against Mycobacterium tuberculosis (Mtb). Materials & methods: The minimum inhibitory concentration (MIC), cytotoxicity for three cell lines, ethidium bromide accumulation and checkerboard methods were carried out. Results: Compounds (6a, 6b, 6c, 6g, 6h and 6j) showed significant anti-Mtb activity (MIC 3.9-7.8 µg/ml) and no antagonism with anti-TB drugs already used in the TB treatment. Selectivity index (SI) was also determined, with values reaching 42.9 for H37Rv strain and 97.1 for clinical isolate. Five compounds also showed bacterial efflux pumps inhibition and one showed modulator effect with three drugs. Conclusion: These six TDZs should be considered as new scaffolds to develop anti-TB drugs.

Synthesis of novel (-)-Camphene-based thiosemicarbazones and evaluation of anti-Mycobacterium tuberculosis activity.

In this work the aim of study was the synthesis and evaluation of in vitro anti-Mycobacterium tuberculosis activity as well as the cytotoxicity in VERO cells of a series of 17 novel thiosemicarbazones derived from the natural monoterpene (-)-camphene by REMA and MTT methods. Overall, the majority of tested compounds exhibited considerable inhibitory effects on the growth of M. tuberculosis H37Rv, especially the derivatives 3, 4a-c, 4f, 4i, 4k, 5 and 6a-b. MIC values of 20 tested compounds ranged from 3.9 to > 250 µg/mL. It was found that when inserting new nitrogenous groups to the (-)-camphene increased the anti-M. tuberculosis activity of some compounds. The SI was calculated for all compounds that showed highly potent anti-M. tuberculosis activity and the best SI values were 21.36, 26.92 and 31.62 (4b, 6a and 6b), and may be considered potential candidates for future antituberculosis drugs.

Anti-inflammatory and antiproliferative activities of Ixora brevifolia Benth. (Rubiaceae).

The crude extract and fractions from the branches of Ixora brevifolia, a tree found in the Brazilian Cerrado, were tested for anti-inflammatory and in vitro antiproliferative effects. The crude extract and n-hexane fraction exhibited significant inhibition of ear oedema in mice, while n-hexane-precipitated and chloroform fractions strongly inhibited the myeloperoxidase activity in ear tissue. The n-hexane and n-hexane-precipitated fractions showed strong growth inhibition for glioma cell line and the hydromethanolic fraction inhibited the growth of leukaemia cell line.

Induction of Early Autophagic Process on Leishmania amazonensis by Synergistic Effect of Miltefosine and Innovative Semi-synthetic Thiosemicarbazone.

Drug combination therapy is a current trend to treat complex diseases. Many benefits are expected from this strategy, such as cytotoxicity decrease, retardation of resistant strains development, and activity increment. This study evaluated in vitro combination between an innovative thiosemicarbazone molecule - BZTS with miltefosine, a drug already consolidated in the leishmaniasis treatment, against Leishmania amazonensis. Cytotoxicity effects were also evaluated on macrophages and erythrocytes. Synergistic antileishmania effect and antagonist cytotoxicity were revealed from this combination therapy. Mechanisms of action assays were performed in order to investigate the main cell pathways induced by this treatment. Mitochondrial dysfunction generated a significant increase of reactive oxygen and nitrogen species production, causing severe cell injuries and promoting intense autophagy process and consequent apoptosis cell death. However, this phenomenon was not strong enough to promote dead in mammalian cell, providing the potential selective effect of the tested combination for the protozoa. Thus, the results confirmed that drugs involved in distinct metabolic routes are promising agents for drug combination therapy, promoting a synergistic effect.

Phenolic compounds and anticancer activity of commercial sugarcane cultivated in Brazil.

The cultivation of sugarcane hybrids (X Saccharum officinarum L.) is an important revenue source for the Brazilian economy. Herein it is reported the evaluation of the cytotoxic activity of mid-polarity sugarcane extracts against human cancer cell lines, as well as the isolation of steroids sitosterol, stigmasterol and campesterol, phenolic acids p-hydroxybenzoic, p-hydroxycinnamic, vanillic and ferulic acid, terpenoids α-tocopherol and ß-carotene and a novel substance in sugarcane, the flavonoid aglycone tricin (5,7,4-trihydroxy-3,5-dimethoxyflavone). The presence of large amounts of phenolic acids and the flavonoid tricin may explain the cytostatic activity observed for the mid-polarity crude extract and filtrates.

1,3,4-Thiadiazole derivatives of R-(+)-limonene benzaldehyde-thiosemicarbazones cause death in Trypanosoma cruzi through oxidative stress.

This work evaluated the in vitro and in vivo activity of TDZ 2 on Trypanosoma cruzi amastigotes and determined the possible mechanism of action of this compound on T. cruzi death. TDZ 2 inhibited T. cruzi proliferation in vitro and had low haemolytic potential. It also induced morphological and ultrastructural alterations. We observed a reduction of cell volume, the depolarization of the mitochondrial membrane, an increase in ROS production, lipoperoxidation of the cell membrane, lipid bodies formation and production of nitric oxide, a decrease in reduced thiols levels and, presence of autophagic vacuoles. The in vivo study found a reduction of parasitemia in animals treated with TDZ 2 alone or combined with benznidazole. Altogether, the alterations induced by TDZ 2 point to an oxidative stress condition that lead to T. cruzi cell death.

Acyl-homoserine Lactone from Saccharum × officinarum with Stereochemistry-Dependent Growth Regulatory Activity.

Acyl-homoserine lactones (AHLs) are a class of compounds produced by Gram-negative bacteria that are used in a process of chemical communication called quorum sensing. Much is known about how bacteria use these chemical compounds to control the expression of important factors; however, there have been few reports about the presence and effects of AHLs in plants. In this study, the phytochemical study of leaves and culms of sugar cane (Saccharum × officinarum) led to the identification of N-(3-oxo-octanoyl)homoserine lactone. Since the absolute configuration of the natural product could not be determined, both R and S enantiomers of N-(3-oxo-octanoyl)homoserine lactone were synthesized and tested in sugar cane culms. The enantiomers caused changes in the mass and length of buds and roots when used at micromolar concentrations. Using the sugar cane RB96-6928 variety, the S enantiomer increased sprouting of roots more effectively than the R enantiomer. Furthermore, scanning electron microscopy showed that both the R and S enantiomers led to more stretched root cells compared with the control.

Acute toxicity, antiedematogenic activity, and chemical constituents of Palicourea rigida Kunth.

The phytochemical study of the leaves, roots, and flowers of Palicourea rigida led to the isolation of the triterpenes betulinic acid (1) and lupeol (2), the diterpene phytol (3), and the iridoid glycosides sweroside (4) and secoxyloganin (5). These compounds were identified using NMR 1H and 13C and comparing the spectra with published data. We studied the antiedematogenic activity of crude extracts from the organs, and of different fractions, in mice and found that the n-hexane fraction of the leaf extract significantly inhibited the ear edema resulting from croton oil administration. The crude extract from leaves was not acutely toxic to the mice.

Bioguided identification of antifungal and antiproliferative compounds from the Brazilian orchid Miltonia flavescens Lindl.

The Orchidaceae family is appreciated worldwide for the beauty of its flowers, and hundreds of species of this family occur in Brazil. Yet little is known about the potential of orchids for therapeutic application. We have investigated bioactive compounds produced by the South Brazilian orchid Miltonia flavescens Lindl. Bioguided studies with the fungus Cladosporium herbarum allowed the identification of hydrocinnamic acid as the active antifungal compound. In addition, the chloroform fraction exhibited an interesting activity against human cancer cells, and 5,7-dihydroxy-6,4'-dimethoxyflavone isolated from this fraction was found to be active against seven human cancer cell lines, including NCI/ADR-RES ovary sarcoma, with an IC50 value of 2.6 microg/mL. This is the first report on the cytostatic activity of this flavone against human ovary sarcoma.

Cytotoxic activity of Guettarda pohliana Müll. Arg. (Rubiaceae).

The cytotoxic activity of crude extracts and their fractions from leaves and roots of G. pohliana was assessed against nine human cancer cell lines: melanoma (UACC-62), breast (MCF-7), breast expressing the multidrug resistance phenotype (NCI-ADR), lung (NCI-460), prostate (PCO-3), kidney (786-0), ovarian (OVCAR), colon (HT-29) and leukaemia (K-562). The hexane fraction from leaves (HL) and ethyl acetate (EAR), chloroform (CR) and hydromethanolic (HMR) fractions from roots were the most active fractions against K-562 with GI50 values being lower than 1 µg mL⁻¹. Also, CR and HMR fractions were active against UACC-62 cell line in the same order of magnitude. The phytochemical study of the CR fraction allowed identifying the known iridoids secoxyloganin, sweroside and loganin.

Antiproliferative activity of Luehea candicans Mart. et Zucc. (Tiliaceae).

Luehea candicans Mart. et Zucc. (Tiliaceae) is known as 'açoita-cavalo' and is one of the most important medicinal plants found in the Brazilian cerrado. The crude methanolic extracts of the branches and leaves and their fractions were evaluated using the following cancer cell lines: MCF-7 (breast), NCI-ADR (breast expressing the multidrug resistance phenotype), NCI-460 (lung), UACC-62 (melanoma), 786-0 (kidney), OVCAR (ovarian), PCO-3 (prostate), HT-29 (colon) and K-562 (leukaemia). The crude methanolic extracts from the branches (B) and leaves (L) were able to inhibit the growth of the K-562 and 786-0 cell lines in a dose-dependent manner, with GI(50) values of 8.1 and 5.4 µg mL(-1), respectively. The hexane (L1), chloroform (L2) and methanol (L4) fractions derived from extract L showed a high selectivity and pronounced cytostatic activity against 786-0 (GI(50) ~ 40 µg mL(-1)). A significant amount of lupeol was isolated from fraction L2. The chloroform (B2) and methanol (B3) fractions derived from extract (B) exhibited less selectivity, showing the highest cytostatic activity against K-562, NCI-ADR, OVCAR, MCF-7 and NCI-460 cells, with GI(50) values between 27 and 40 µg mL(-1). Lupeol, betulin, a mixture of steroids, (-)-epicatechin, vitexin and liriodendrin were isolated from these active fractions.

Antitrypanasomal activity of novel benzaldehyde-thiosemicarbazone derivatives from kaurenoic acid.

A series of new thiosemicarbazones derived from natural diterpene kaurenoic acid were synthesized and tested against the epimastigote forms of Trypanosoma cruzi to evaluate their antitrypanosomal potential. Seven of the synthesized thiosemicarbazones were more active than kaurenoic acid with IC50 values between 2-24.0 mM. The o-nitro-benzaldehyde-thiosemicarbazone derivative was the most active compound with IC50 of 2.0 mM. The results show that the structural modifications accomplished enhanced the antitrypanosomal activity of these compounds. Besides, the thiocyanate, thiosemicarbazide and the p- methyl, p-methoxy, p-dimethylamine, m-nitro and o-chlorobenzaldehyde-thiosemicarbazone derivatives displayed lower toxicity for LLMCK2 cells than kaurenoic acid, exhibing an IC50 of 59.5 mM.

Flavonoides e atividade antioxidante em Palicourea rigida Kunth, Rubiaceae / Flavonoids and antioxidant activity in Palicourea rigida Kunth, Rubiaceae

A atividade antioxidante, avaliada pelo método DPPH (1,1-difenil-2-picrilidrazila), e o teor em compostos fenólicos totais do extrato bruto metanólico e frações das folhas da espécie Palicourea rigida Kunth, Rubiaceae, foram quantificadas neste trabalho. Apesar da baixa atividade apresentada pelo extrato bruto (500 ppm), a fração acetato de etila apresentou atividade moderada (192 ppm) e o maior teor de fenólicos totais dentre as frações ensaiadas. Assim, a fração acetato de etila foi submetida a procedimentos cromatográficos o que resultou no isolamento dos flavonoides quercetina 3-O-β-D-glicosídeo, quercetina 3-O-soforosídeo e isoraminetina 3-glicosídeo, cujas estruturas foram elucidadas por análise espectroscópica, incluindo RMN (1D e 2D) e comparação com os dados da literatura.

The antioxidant activity, evaluated by DPPH (1,1-difenil-2-picrilidrazila) method, and the determination of the total phenolic compounds of the crude methanolic extract and fractions of the Palicourea rigida Kunth, Rubiaceae, leaves were quantified in this work. Despite weak activity exhibited by crude extract (500 ppm), the fraction ethyl acetate showed moderate activity (192 ppm), and the largest value for the phenolic compounds among all the assayed fractions. Then, the ethyl acetate fraction was submitted to the chromatography procedures which led to the isolation of the flavonoid quercetin 3-O-D-glicoside, quercetin 3-O-sophoroside and isorhamnetin 3-glicoside, which had the structures elucidated by spectroscopy analysis, including RMN (1D and 2D) and comparison with literature data.

Antitumor activity of (-)-alpha-bisabolol-based thiosemicarbazones against human tumor cell lines.

A series of thiosemicarbazones deriving from the natural sesquiterpene (-)-alpha-bisabolol were synthesized and tested against a panel of eight human tumor cell lines to evaluate their anti-tumor potential. Some of the compounds exhibited inhibitory effects on the growth of a wide range of cancer cell lines, but myeloid leukemia cells (K-562) were especially sensitive to all tested thiosemicarbazones (GI(50) 0.01-4.22 microM). Among the analogues, the ketone derivative 3l was the most active, exhibiting potent antitumoral activity (GI(50) 0.01 microM) and high selectivity for K-562 cells (deltaTGI 505). It also demonstrated high cytotoxicity, with an LC(50) of 1.55 microM for the K-562 cells, but it showed only moderate selectivity (deltaLC(50) 38.5 microM). Through structure-activity relationship studies, we identified some structural requirement for the antitumoral activity exhibited by these promising compounds.

Amaiouine, a cyclopeptide alkaloid from the leaves of Amaioua guianensis.

Amaiouine, a cyclopeptide alkaloid, was isolated from the ethanolic extract of the leaves of Amaioua guianensis. The structure was elucidated by NMR spectroscopy and confirmed by X-ray crystallography.

A tetrahydro beta-carboline trisaccharide from Palicourea coriacea (Cham.) K. Schum.

A new tetrahydro beta-carboline alkaloid that has an oligosaccharide unit was isolated from the root extracts of the Palicourea coriacea. The structure was elucidated using spectral methods, including 2D NMR: COSY, HMQC, HMBC and NOESY.