In vitro antiproliferative activity of alkaloids isolated from Tabernaemontana catharinensis A.DC (Apocynaceae).

In this work, four alkaloids from the stem bark of T. catharinensis were isolated, namely: voacangine (1); ethyl apovincaminate (2); affinisine (3) and voachalotine (4). The alkaloids were tested in vitro for antiproliferative capacity in eight tumor cell lines: U251 (glioma), MCF-7 (breast), NCI-ADR/RES (drug resistant ovary), 786-0 (kidney), NCI-H460 (lung), HT-29 (colon), K562 (leukemia) and PC-3 (prostate) and a non-tumor keratinocyte cell line (HaCat). Antiproliferative activity was observed after 48 hours and results expressed as the concentration needed to induce 50% growth inhibition (GI50) in µM. The chemotherapy drug Doxorubicin was used as a standard. The alkaloid affinisine (3) was the most promising, showing moderate inhibition rates in addition to the cytotoxic and cytocidal effect against all strains tested. It also proved to be a very promising compound, showing high selectivity rates when compared to the non-tumor keratinocyte cell line (HaCat).

First report on the production of phytotoxic metabolites by Mycoleptodiscus indicus under optimized conditions of submerged fermentation.

An alternative to controlling weeds resistant to conventional herbicides is the isolation of new active principles. Fungi can produce phytotoxic metabolites that may be used in the development of new herbicides. The objectives of this study were: (1) isolate, select, and identify a fungus producer of phytotoxic metabolites and (2) optimize the culture conditions of this fungus in a low-cost culture medium, with the aim of increasing the phytotoxic effects of their metabolites in weeds and commercial plants. Fungi were isolated from the leaves of Conyza sp. with disease symptoms and selected according to the production of phytotoxic metabolites in solid and submerged fermentation in a low-cost culture medium. A Plackett-Burman Design and Central Composite Rotational Design were used to optimize the conditions of temperature, agitation, pH, and concentrations of glucose and yeast extract in submerged fermentation. The phytotoxic metabolites produced under optimal conditions were tested on 10 commercial plants and weeds that are difficult to control. Of the nine fungi isolated, Mycoleptodiscus indicus UFSM54 produced higher leaf lesions. The production of phytotoxic metabolites was optimized when the fungus was cultivated at 35°C, 50 rpm, and 1.5 g L-1 of glucose in submerged fermentation. The metabolites of M. indicus caused severe phytotoxic effects on germination and seedling growth, and enhanced lesion development on detached plant leaves. The present study is the first to report on the production of phytotoxic metabolites by M. indicus, a potential producer of bioherbicides.

Achyrocline flaccida essential oil from Brazil: phytochemical composition, genotoxicity, protective effects on Caenorhabditis elegans, and antimycobacterial activity.

Achyrocline flaccida (Weinm) DC. essential oil was obtained by hydrodistillation of wild flowers from southern Brazil. We explored, for the first time, the phytochemical composition, toxicity, resistance to oxidative stress in Caenorhabditis elegans, and antimycobacterial activities of A. flaccida essential oil. Twenty-four compounds were identified by GC-FID-MS and the major constituents identified were α-pinene (41.10%) and caryophyllene (30.52%). The essential oil showed no signs of genotoxicity in the comet assay and presented relevant antioxidant capacity since it prevented ROS production in the C. elegans model. Furthermore, the minimal inhibitory concentrations (MIC) results showed that M. abscessus, M. massiliense, and M. fortuitum had their growth inhibited by A. flaccida essential oil. Therefore, the essential oil of this plant is a promising alternative in the search for new compounds capable of decreasing oxidative stress and treating mycobacteriosis.

Antibacterial activity of Discaria americana Gillies ex Hook (Rhamnaceae).

ETHNOPHARMACOLOGY RELEVANCE: Discaria americana Gillies ex Hook (sin. Discaria febrifuga and Discaria longispina) (Rhamnaceae) is a plant native from Rio Grande do Sul (Southern Brazil), Uruguay and Argentine, and has been used in Brazilian traditional medicine as antipyretic agent, and for stomach disorders. In Rio Grande do Sul, Uruguay and Argentine, the roots, in decoction, are used as tonic and febrifuge. Although it is a plant widely used by the population, there are no studies proving this popular use. MATERIAL AND METHODS: The crude neutral methanol extract, and pure isolated alkaloids, were investigated in vitro for antimicrobial activities against four Gram-positive bacteria: Staphylococcus aureus, Bacillus subtillis, Bacillus cereus, Enterococcus faecium; and five Gram-negative bacteria: Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa. RESULTS: The crude neutral methanol (CME) extract of the root bark of Discaria americana showed antibacterial activity, ranging from 62.5 to 250 µg mL-1 (MIC), against the tested bacteria. From the fractions obtained from the crude extract, the basic ethereal fraction (BEF) showed to be more effective, with MICs between 31.5 and 125 µg mL-1 against the tested bacteria. The bioassay-guided fractionation of the ethyl ether basic fraction yielded eight cyclopeptide alkaloids: frangufoline (1), frangulanine (2), adouetine Y' (3), discarine A (4) discarine B (5), discarine C (6), discarene C (7) and discarine D (8). When evaluated against the Gram-positive bacteria Enterococcus faecium, discarine B (5) proved to be the most active alkaloid with a MIC/MLC = 0.77/1.55 µg mL-1, near the most active antibacterial agent levofloxacin (MIC/MLC = 0.77/0.77 µg mL-1). Moreover, discarine C (6) was the more active alkaloid against Salmonella enterica serovar Typhimurium, with a MIC/MLC = 3.1/6.2 µg mL-1, the same observed for the antibacterial agent azithromycin. Kinetic measurements of the bacteriolytic activities of discarine B (5) against Enterococcus faecium (Gram-positive), and of discarine C (6) against Salmonella enterica serovar Typhimurium (Gram-negative) were determined by optical density based on real time assay, suggesting that both mode of action are partially bacteriolytic. CONCLUSION: In conclusion, five 14-membered cyclopeptide alkaloids isolated from Discaria americana Gillies ex Hook (Rhamnaceae) showed promising antibacterial activity, making this metabolites a class of scientific interest. The good activity presented by the extract and the alkaloids against the Gram-positive bacteria Enterococcus faecium and against the Gram-negative bacteria Salmonella enterica serovar Typhimurium, Enterobacter. aerogenes and Escherichia coli, corroborate with the popular use of this plant for stomach disorders and as antifebrile.

Cyclopeptide alkaloids from Scutia buxifolia Reiss.

Scutianene E (1), 3,4,28-tris-epi-scutiaene E (2), 28-epi-scutianene E (3) and scutianene L (4), four neutral cyclopeptide alkaloids, were isolated from Scutia buxifolia Reiss, together with four known cyclopeptide alkaloids, scutianines B, C, D and E. Scutianenes 1-3 are diastereoisomeric compounds, with 3-hydroxyleucine as a ß-hydroxy amino acid unit, which is connected to the styryl fragment via an ether bridge, ß-phenylserine, as a common ring-bonded amino acid residue. Attached to the amino group of ß-hydroxyamino acid is a side chain [trans-CH=CH-Ph]. The structures of the peptides were elucidated by means of spectroscopic analysis, including extensive 2D NMR studies. The stereochemistry for the diastereomeric 3,4,28-tris-epi-scutiaene E and 28-epi-scutianene E was confirmed by X-ray diffraction analysis of their O-acetyl derivatives.

Composition and antibacterial activity of the essential oils from Zanthoxylum rhoifolium.

The essential oils from the aerial parts of leaves, fruits and flowers of Zanthoxylum rhoifolium of Southern Brazil (Rio Grande do Sul), were analysed by GC, GC/MS, and chiral phase gas chromatography (CPGC). Forty-eight compounds were identified from the essential oils. The major constituents of the essential oil of the leaves were germacrene D (34 %) and bicyclogermacrene (23 %) and of the fruits, menth-2-en-1-ol (46.2 %), beta-myrcene (30.2 %), (-)-linalool (15 %) and (-)-alpha-terpineol (8.45 %). beta-Myrcene (65 %) and menth-2-en-1-ol (5.4 %) dominate the essential oil of the flowers. The oils of the leaves and fruits were bioactive with antibacterial activity against Staphylococcus aureus (Gram positive), and Klebsiella pneumoniae and Salmonella setubal bacteria (Gram negative) microorganisms, while the essential oil of the flowers was inactive.