Ricardo Machado Kuster

In vitro activity of Brazilian medicinal plants, naturally occurring naphthoquinones and their analogues, against methicillin-resistant Staphylococcus aureus.

Fourteen extracts from Brazilian traditional medicinal plants used to treat infectious diseases were used to look for potential antimicrobial activity against multiresistant bacteria of medical importance. Staphylococcus aureus strains were susceptible to extracts of Punica granatum and Tabebuia avellanedae. The minimum inhibitory concentrations (MICs) of the total extracts and of additional fractions of these plants were determined by employing strains of methicillin-resistant (MRSA) and -sensitive (MSSA) S. aureus, including isolates of the PFGE clone A, which is prevalent in Brazil and two ATCC reference strains. A mixture of ellagitannins isolated from P. granatum and two naphthoquinones isolated from T. avellanedae demonstrated antibacterial activity against all S. aureus strains tested. Semi-synthetic furanonaphthoquinones (FNQs) showed lower MICs than those exhibited by natural occurring naphthoquinones. The results indicate that these natural products can be effective potential candidates for the development of new strategies to treat MRSA infections.

Antimicrobial Ellagitannin of Punica granatum Fruits

The ethyl acetate extract of Punica granatum fruits was fractionated by chromatographic techniques to afford the ellagitannin punicalagin. The substance was found to be active against methicillin-resistant Staphylococcus aureus strains and was identified by HPLC/UV and 1HNMR. The antibacterial assays which guided the isolation of the tannin were conducted using the disc diffusion method. Minimum inhibitory concentration (MIC) was determined by the dilution method according to NCCLS (National Committee for Clinical Laboratory Standards) procedure.

Produtos naturais para o controle da transmissão da dengue: atividade larvicida de Myroxylon balsamum (óleo vermelho) e de terpenóides e fenilpropanóides

The bioassay-guided fractionation of the hexane extract obtained from the medicinal plant Myroxylon balsamum (red oil) was conducted in preparative thin layer chromatography on silica gel. The obtained fractions and some terpenoids and phenylpropanoids were assayed as larvicidal on third instar Aedes aegypti larvae, NPPN colony. The results indicate that the sesquiterpene nerolidol was the active constituent in the extract and that the sesquiterpenes were more active than the monoterpenes and phenylpropanoids utilized in this study. Lipophilicity seems to be an important property for the activity since the compounds with hydroxyl, carbonyl and methoxyl groups were less active. The results confirm also that essential oils can be a good tool for the control of dengue.

Biologically active flavonoids and kava pyrones from the aqueous extract of Alpinia zerumbet

From the aqueous extract of Alpinia zerumbet (Pers) B. L. Burttet Smith. (= Alpinia speciosa K. Schum.) flavonoids and kava pyrones were obtained. The flavonoids identified as rutin (1), kaempferol‐3‐O‐rutinoside (2), kaempferol‐3‐O‐glucuronide (3), (+)‐catechin (4) and (−)‐epicatechin (5) are well known substances that can contribute to the hypotensive, diuretic and antiulcerogenic activity of the aqueous extract of the plant, while the kava pyrones dihydro‐5,6‐dehydrokawain (6) and 5,6‐dehydrokawain (7) have been described as antiulcerogenic and antithrombotic. The compounds were identified from their UV, 1H‐ and/or 13C‐NMR, hydrolytic and co‐TLC data. The well known activity of these compounds, which have not been previously isolated from the leaves of Alpinia zerumbet, may explain the use of the plant in the treatment of hypertension.

Tabebuia avellanedae naphthoquinones: activity against methicillin-resistant staphylococcal strains, cytotoxic activity and in vivo dermal irritability analysis

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococcus infections are a worldwide concern. Currently, these isolates have also shown resistance to vancomycin, the last therapy used in these cases. It has been observed that quinones and other related compounds exhibit antibacterial activity. This study evaluated the antibacterial activity, toxicity and in vivo dermal irritability of lapachol extracted from Tabebuia avellanedae and derivatives against methicillin-resistant staphylococcal isolates. In addition, its mechanism of action was also analyzed.MethodsThe compounds β-lapachone, 3-hydroxy β N lapachone and α-lapachone were tested to determine the MIC values against methicillin-resistant S. aureus, S. epidermidis and S. haemolyticus strains, being the two last ones hetero-resistant to vancomycin. Experiments of protein synthesis analysis to investigate the naphthoquinones action were assessed. In vitro toxicity to eukaryotic BSC-40 African Green Monkey Kidney cell cultures and in vivo primary dermal irritability in healthy rabbits were also performed.ResultsThe compounds tested showed antibacterial activity (MICs of 8, 4/8 and 64/128 μg/mL to β-lapachone, 3-hydroxy β N lapachone and α-lapachone, respectively), but no bactericidal activity was observed (MBC > 512 μg/mL for all compounds). Although it has been observed toxic effect in eukaryotic cells, the compounds were shown to be atoxic when applied as topic preparations in healthy rabbits. No inhibition of proteins synthesis was observed.ConclusionOur results suggest that quinones could be used in topic preparations against wound infections caused by staphylococci, after major investigation of the pharmacological properties of the compounds. Studies about the use of these compounds on tumoral cells could be carried on, due to their effect in eukaryotic cells metabolism.

Hypoglycemic activity of two Brazilian Bauhinia species: Bauhinia forficata L. and Bauhinia monandra Kurz.

The hypoglycemic activity of aqueous extracts from Bauhinia forficata L. and Bauhinia monandra Kurz leaves (10% w/v) was evaluated in normoglycemic mice. Both extracts have shown hypoglycemic activity using this methodology. It was also possible to isolate two flavonoids from B. forficata L., 3,7-di-O-a-rhamnopyranosylquercetin and 3,7-di-O-a-rhamnopyranosylkaempferol (kaempferitrin), whose structures were elucidated by usual NMR techniques. Only the quercetin derivative was identified in B. monandra aqueous extract by HPLC.

Furocoumarins from the rhizomes of Dorstenia brasiliensis

Abstract A monoterpenoid substituted furocoumarin, 5-[3-(4,5-dihydro-5,5-dimethyl-4-oxo-2-furanyl)butoxy]-7H-furo[3-2-g][1]benzopyran-7-one, was isolated from the rhizomes of Dorstenia brasiliensis Lam. along with psoralen, bergapten, sitosterol, stigmasterol, 3- O -β-glucosylsitosterol and sucrose. Traces of a new unsaturated analogue, 5-[[3-(4,5-dihydro-5,5-dimethyl-4-oxo-2-furanyl-2-butenyl-] oxy]-7H-furo[3-2-g][1]benzopyran-7-one, were identified by mass spectrometry.

Chemical composition and antibacterial activity of Brazilian propolis essential oil

The present study aimed at investigating the chemical composition of essential oil extracted from Brazilian propolis and the susceptibility of Staphylococcus aureus, Staphylococcus epidermides, Streptococcus pyogenes and Escherichia coli to this substance. The essential oil was obtained by steam distillation of propolis and examined by gas chromatography/mass spectrometry (GC/MS). In addition, the agar diffusion method using filter paper disks was employed. Antibacterial activity was measured as equivalent diameters of inhibition zones (in millimeters) after incubation at 37o C for 24 hours. From the 26 identified constituents, β-caryophyllene (12.7%), acetophenone (12.3%) and β-farnesene (9.2%) were found to be major components. New components, namely linalool, methyl hydrocinnamate, ethyl hydrocinnamate, α-ylangene, γ-elemene and valencene, are reported for the first time to be present in propolis essential oil. This oil also exhibited antibacterial activity.

Potential use of Piper nigrum ethanol extract against pyrethroid-resistant Aedes aegypti larvae

Fractionation of Piper nigrum ethanol extract, biomonitored by assays on pyrethroid-resistant Aedes aegypti larvae yielded isolation of the larvicidal amides piperolein-A and piperine. Comparing LC50 values, the ethanol extract (0.98 ppm) was the most toxic, followed by piperolein-A (1.46 ppm) and piperine (1.53 ppm).

Flavonoids and a neolignan glucoside from Guarea macrophylla (Meliaceae)

This work describes the phytochemical study of the methanol extract obtained from leaves of Guarea macrophylla, leading to the isolation and identification of three flavonoid glycosides (quercetin 3-O-β-D-glucopyranoside, quercetin 3-O-b-D-galactopyranoside, kaempferol 7-O-β-D-glucopyranoside) and a neolignan glucoside, dehydrodiconiferyl alcohol-4-β-D-glucoside. All compounds were identified by a combination of spectroscopic methods (1H, 1D, 2D NMR, 13C and UV), ESI-MS and comparison with the literature data. This is the first report of flavonoids in the genus Guarea and of a neolignan glucoside in the Meliaceae family.