Inhibition of Staphylococcus aureus TetK and MsrA efflux pumps by hydroxyamines derived from lapachol and norlachol.

The present study aimed to evaluate the in vitro efflux pump inhibitory capacity of hydroxyamines derived from lapachol and norlachol, where compounds 3, 4, and 5 were tested against the S. aureus strains: RN4220 carrying the pUL5054 plasmid; and IS-58, endowed with the PT181 plasmid. The substances were synthesized from 2-hydroxy-quinones, lapachol and nor-lapachol obtaining the corresponding 2-methoxylated derivatives via dimethyl sulfate alkylation in a basic medium, which then reacted chemoselectively with 2-ethanolamine and 3-propanolamine to form the corresponding amino alcohols. The antibacterial action of the substances was quantified by determining the Minimum Inhibitory Concentration (MIC), while a microdilution assay was carried out to ascertain efflux pump inhibition of Staphylococcus aureus strains carrying the MsrA macrolide and the TetK tetracycline efflux pumps with the substances at a sub-inhibitory concentration. The results were subjected to statistical analysis by an ANOVA test and Bonferroni post hoc test. The MIC from the substances exhibited a value ≥ 1024 µg/mL. However, a significant reduction (p < 0.0001) of the erythromycin, tetracycline and ethidium bromide MIC was demonstrated when these were in combination with the substances, with this effect being due to a supposed efflux pump inhibition. The tested substances demonstrated effectiveness at decreasing the MIC of erythromycin, tetracycline and ethidium bromide, potentially by inhibiting the MsrA macrolide and the TetK tetracycline efflux pumps present in the tested S. aureus strains.

Acute and repeated dose 28-day oral toxicity of Chrysobalanusicaco L. leaf aqueous extract.

Chrysobalanus icaco L. is a native plant of Brazil used as a food source and traditionally for the treatment of various diseases. The aim of study was performed the phytochemical analysis by UPLC-DAD-ESI-QTOF-MS/MS, and evaluated acute and repeated dose oral toxicities of the C. icaco L. leaf aqueous extract (AECi). The acute toxicity study was performed using a dose of AECi 2000 mg/kg, while the repeated dose toxicity study, the AECi was administered daily at doses of 100, 200 and 400 mg/kg, for 28 days. Behavior and mortality of animals were observed during the test period and body weight, as well water and eating consumption. Hematological, biochemical parameters and histopathological examinations were carried out. Phytochemical analysis of the AECi revealed the presence of flavonoids and tannins. Oral single dose of 2000 mg/kg of AECi resulted in no mortalities or abnormal clinical signs. Studies of repeated dose toxicity promoted a reduction in the body weight of treated animals and an increase of hepatic enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in both, males and females. Histopathological analyzes showed alterations in the livers of animals treated with AECi. Thus, this study recommends the population take care when using this species, especially during prolonged periods.

Alkene lactones from Persea fulva (Lauraceae): Evaluation of their effects on tumor cell growth in vitro and molecular docking studies.

The new alkene lactone, (3E)-5,6-dihydro-5-(hydroxymethyl)-3-docdecylidenefuran-3(4H)-one (1), named majoranolide B, and three alkene lactones known as majorenolide (2), majoranolide (3) and majorynolide (4) were obtained from the aerial parts of Persea fulva (Lauraceae). The structures were elucidated in light of extensive spectroscopic analysis, including 1D, 2D NMR (1H, 13C, 1H-1H-COSY, HMBC and HSQC) and HR-ESI-MS. These compounds were screened for their in vitro antiproliferative activity in rat C6 glioma and astrocyte cells using MTT assay and in silico by molecular docking against targets that play a central role in controlling glioma cell cycle progression. Majoranolide (3) is the most active compound with IC50 6.69 µM against C6 glioma cells, followed by the compounds 1 (IC50 9.06 µM), 2 (IC50 12.04 µM) and 4 (IC50 41.90 µM). The alkene lactones 1-3 exhibited lower toxicity in non-tumor cells when compared to glioma cells. Molecular docking results showed that majoranolide establishes hydrogen bonds with all targets through its α,ß-unsaturated-γ-lactone moiety, whereas the long-chain alkyl group binds by means of several hydrophobic bonds. In the present study, it can be concluded from the anti-proliferative activity of isolates against C6 glioma cells that lactone constituents from P. fulva could have a great potential for the control of C6 glioma cells.

Characterisation of phenolic compounds by UPLC-QTOF-MS/MS of geopropolis from the stingless bee Melipona subnitida (jandaíra).

INTRODUCTION: Melipona subnitida Ducke (jandaíra) is a stingless bee native to north-eastern Brazil, which produces geopropolis, a mixture of beeswax, plant resins, pollens and earth that is used for sealing beehives. OBJECTIVE: To extend the knowledge on phenolic compounds in fractions obtained by C18-solid phase extraction (SPE) of nine geopropolis samples from Melipona subnitida collected at different times. METHODOLOGY: Chromatographic profiles of nine samples of geopropolis from jandaíra were analysed by ultra-performance liquid chromatography coupled with a diode array detector and quadrupole time-of-flight mass spectrometry (UPLC-DAD-QTOF-MS/MS) and combined with the use of data-independent acquisition (MSE) for the profiling and structural characterisation of the phenolic compounds. The isolated compound was identified by nuclear magnetic resonance of hydrogen and carbon (1 H- and 13 C-NMR). RESULTS: The present study with geopropolis of jandaíra resulted in the characterisation of 51 phenolics by UPLC-DAD-QTOF-MS/MS: four galloyl glucosides, one ellagic acid, 11 acyl-hexosides, 23 acyl-galloyl-hexosides and 12 flavonoids. The structures of two compounds (1,6-di-O-(E)-coumaroyl-2-O-galloyl-ß-d-glucopyranoside and 1-O-cinnamoyl-6-O-(E)-coumaroyl-2-O-galloyl-ß-d-glucopyranoside) were established by 1 H and the attached proton test (APT) experiments as well as high-resolution electrospray ionisation mass spectroscopy (HR-ESI-MS) analysis. CONCLUSION: The geopropolis of jandaíra showed phenolic compounds galloyl hexosides, ellagic acid, acyl-(cinnamoyl/coumaroyl)-hexosides, acyl-(cinnamoyl/coumaroyl)-galloyl-hexosides and flavonoids (aglycones and acylated-O-glycosides).

Alkaloids and Phenolic Compounds from Sida rhombifolia L. (Malvaceae) and Vasorelaxant Activity of Two Indoquinoline Alkaloids.

The follow-up of phytochemical and pharmacological studies of Sida rhombifolia L. (Malvaceae) aims to strengthen the chemosystematics and pharmacology of Sida genera and support the ethnopharmacological use of this species as hypotensive herb. The present work reports phytoconstituents isolated and identified from aerial parts of S. rhombifolia by using chromatographic and spectroscopic methods. The study led to the isolation of scopoletin (1), scoporone (2), ethoxy-ferulate (3), kaempferol (4), kaempferol-3-O-ß-d-glycosyl-6''-α-d-rhamnose (5), quindolinone (6), 11-methoxy-quindoline (7), quindoline (8), and the cryptolepine salt (9). The alkaloids quindolinone (6) and cryptolepine salt (9) showed vasorelaxant activity in rodent isolated mesenteric arteries.

New Polyprenylated Phloroglucinol and Other Compounds Isolated from the Fruits of Clusia nemorosa (Clusiaceae).

Clusia nemorosa has been widely used in folk medicine to treat various ailments, including headaches and inflammation. Investigation of the fruits of Clusia nemorosa (Clusiaceae) led to the isolation and characterization of a new phloroglucinol derivative, named 6S,8S,28S-nemorosic acid (1), together with seven known compounds: friedelin (2), ß-sitosterol (3), stigmasterol (4), ß-sitosterol glycoside (5), kaempferol (6), quercetin (7) and dimethyl citrate (8). The structures were determined by extensive 1D- and 2D-NMR, CD and MS spectroscopic analyses.

Assessment of mechanisms involved in antinociception produced by the alkaloid caulerpine.

In previous works we showed that oral administration of caulerpine, a bisindole alkaloid isolated from algae of the genus Caulerpa, produced antinociception when assessed in chemical and thermal models of nociception. In this study, we evaluated the possible mechanism of action of this alkaloid in mice, using the writhing test. The antinociceptive effect of caulerpine was not affected by intraperitoneal (i.p.) pretreatment of mice with naloxone, flumazenil, l-arginine or atropine, thus discounting the involvement of the opioid, GABAergic, l-arginine-nitric oxide and (muscarinic) cholinergic pathways, respectively. In contrast, i.p. pretreatment with yohimbine, an α2-adrenoceptor antagonist, or tropisetron, a 5-HT3 antagonist, significantly blocked caulerpine-induced antinociception. These results suggest that caulerpine exerts its antinociceptive effect in the writhing test via pathways involving α2-adrenoceptors and 5-HT3 receptors. In summary, this alkaloid could be of interest in the development of new dual-action analgesic drugs.

Antiviral Activity of Flavonoids from Geopropolis of the Brazilian Jandaira Bee against Zika and Dengue Viruses.

Arthropod-borne viruses within the Flaviviridae family such as Zika (ZIKV) and dengue (DENV) are responsible for major outbreaks in tropical countries, and there are no specific treatments against them. Naringenin and 7-O-methyl naringenin are flavonoids that can be extracted from geopropolis, a natural material that the Brazilian Jandaira stingless bee (Melipona subnitida Ducke) produces to protect its nest. Here, these flavonoids were tested against ZIKV and DENV using Vero cells as a cellular model to perform a cytotoxicity assay and to define the effective concentrations of TCID50 as the readout method. The results demonstrated the antiviral activity of the compounds against both viruses upon the treatment of infected cells. The tested flavonoids had antiviral activity comparable with 6-methylmercaptopurine riboside (6-MMPr), used here as a positive control. In addition, to identify the possible action mechanism of the antiviral candidates, we carried out a docking analysis followed by a molecular dynamics simulation to elucidate naringenin and 7-O-methyl naringenin binding sites to each virus. Altogether, these results demonstrate that both flavonoids have potent antiviral effects against both viruses and warrant further in vivo trials.

Role of synthetical amynoquinone ethyl 2-(1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) acetate in inhibition of Ehrlich's tumor.

Quinones are naturally or synthetically occurring secondary metabolites that have various bio-dynamics, highlighting their antitumor potential. This has been explored through their selective cytotoxicity, and studies in medicinal chemistry about the relation between biological activity versus chemical structure may lead to the solution of the toxicity problems associated with quinones. In this context, the antitumor effect of a synthetic naphthoquinone, named Ethyl 2-(1,4-Dioxo-1,4-Dihydronaphthalen-2-Ylamino) Acetate, was tested using mice transplanted with Ehrlich ascitic tumor as an experimental model. The acute toxicity test was performed using 30 mice that received the aminoquinone at doses of 100, 200, 300, and 600 mg/kg. After evaluation of the clinical findings in the spontaneous activity tests, the LD50 calculation for the test substance showed low levels of toxicity at doses lower than 244.11 ± 23.29 mg/kg. Thus, three experimental groups were established, where animals transplanted with tumor cells received NaCl vehicle solution (control, n = 6), and the others were treated with 71.7 mg/kg of Methotrexate (n = 6) or 20 mg/kg of Aminoquinone (n = 6). All administrations were intraperitoneal, in a single dose. Three days after the implantation of the tumor cells the animals were weighed daily and evaluated for tumor biometry and development. The treatments occurred five days after the implantation of the tumor cells and were extended for 7 more days. At the end of the 12-day experimental period, all animals were euthanized for biochemical and histopathological analyses of the tumors and vital organs. The spontaneous activity test showed that the amount of responses associated with the nervous system tends to increase with the increase in dosage, highlighting the excitatory effect on the central nervous system in almost all dosages employed, followed by depressant activities on this system. There was a significant tumor reduction, both in animals treated with methotrexate (71.7 %) and in those treated with aminoquinone (91.6 %) in the control group. There was no significant difference in tumor volume between the animals treated with aminoquinone or methotrexate. The histopathological analysis revealed that in both treatments there were fewer mitoses in the tumor mass compared to the control group. However, there was apparent toxicity to the liver, heart, and left kidney in the treatment with methotrexate compared to aminoquinone. The significant capacity for tumor reduction presented by aminoquinone allows pointing it as a promising alternative for the development of a more efficient drug to control tumor development, being necessary for the development of new studies to deepen the knowledge about its mechanisms of action.

Safety assessment of Bauhinia cheilantha Bong. Steud leaves extract: acute, sub-acute toxicity, antioxidant, and antihemolytic evaluations.

Bauhinia cheilantha (Fabaceae), known popularly as pata-de-vaca and mororó has been largely recommended treating several diseases in folk medicine. However, information on safe doses and use is still scarce. The goal was to evaluate in-vitro antioxidant and antihemolytic and also acute and sub-acute toxicity effects of hydroalcoholic extract from B. cheilantha leaves (HaEBcl). The identification of the compounds in the HaEBcl was performed by ultra-performance liquid chromatography coupled with a diode array detector and quadrupole time-of-flight mass spectrometry. Antioxidant and hemolytic activity of HaEBcl was evaluated in vitro. To study acute toxicity, female mice received HaEBcl in a single dose of 300 and 2.000 mg/kg. Later, sub-acute toxicity was introduced in both female and male mice by oral gavage at 300, 1000, or 2000 mg/kg for 28 consecutive days. Hematological and biochemical profiles were created from the blood as well as from histological analysis of the liver. HaEBcl is rich in flavonoids (quercitrin and afzelin), has no hemolytic effects and moderate antioxidant effects in vitro. Acute toxicity evaluation showed that lethal dose (LD50) of HaEBcl was over 2000 mg/kg. Sub-acute toxicity testing elicited no clinical signs of toxicity, morbidity, or mortality. The hematological and biochemical parameters discounted any chance of hepatic or kidney toxicity. Furthermore, histopathological data did not reveal any disturbance in liver morphology in treated mice. Results indicate that HaEBcl has no hemolytic and moderate antioxidant effects in vitro. In addition, HaEBcl dosage levels up to 2000 mg/kg are nontoxic and can be considered safe for mammals.

Leismanicidal Activity of Propolis Collected in the Semiarid Region of Brazil.

Objective: The aim of the current study is to investigate the chemical composition, cytotoxic effect, and leishmanicidal activity of propolis collected in the semi-arid region of Bahia, Brazil. Methods: EtOH extract, hexane, EtOAc and MeOH fractions from propolis were analyzed by ultra-performance liquid chromatography coupled with diode array detector and quadrupole time-of-flight mass spectrometry. The identification was based on the exact mass, general fragmentation behaviors and UV absorption of the flavonoids. The in vitro cytotoxic effect and leishmanicidal activity of ethanolic extract, hexane, ethyl acetate, and methanolic fractions of propolis were evaluated. Results: Five triterpenes and twenty-four flavonoids were identified. The propolis did not present toxicity to the host cell up to the maximum concentration tested. In addition, all tested samples showed statistically significant activity against promastigotes of Leishmania chagasi and Leishmania amazonensis. Regarding the activity against amastigote forms of L. amazonensis, the hexane fraction, presented statistically significant activity with IC50 of 1.3 ± 0.1 µg/ml. Conclusion: The results support the idea that propolis can be used for future antileishmania studies.

Identification of flavonoids in Hymenaea martiana Hayne (Fabaceae) by HPLC-DAD-MSn analysis.

Hymenaea martiana is a native tree known in Brazil as 'jatobá' and used in folk medicine to treat pain and inflammation. The aim of this work was to identify the flavonoids present in the crude ethanolic extract and ethyl acetate fraction using HPLC-DAD and LC-MSn analysis. The ethanolic extract was partitioned to obtain the ethyl acetate fraction. The analysis of astilbin content also was carried out by HPLC analysis. HPLC-DAD-ESI/MSn analysis of the ethanolic extract and ethyl acetate fraction revealed the presence of eleven peaks in the chromatograms, and all these peaks were identified: taxifolin, eucryphin, astilbin and 3 diastereoisomers, engeletin and 2 diastereoisomers, quercitrin and 2,6,3',4'-tetrahydroxy-2-benzylcoumaran-3-one. The ethyl acetate fraction had a higher astilbin concentration (151.87 µg/mL) than the ethanolic extract (40.13 µg/mL). In conclusion, the species could be considered a good source of flavonoids, which can be related to the main chemotaxonomic markers for the genus Hymenaea.

Oceanapia magna Sponge Presents Dual Effect on the Gastrointestinal Motility of Rodents: In Vitro and In Vivo Assays.

Oceanapia magna Santos-Neto, Nascimento, Cavalcanti and Pinheiro sponges are distributed across tropical worldwide seas. Some studies of marine products have shown interesting activities in smooth muscle models. Hence, we assessed the effect of the ethanolic extract of Oceanapia magna. (OC-EtOH) on acute toxicity and gastrointestinal motility (in vitro and in vivo) in rodent models. On guinea pig ileum, OC-EtOH induced a concentration dependent contraction on basal tonus, which was not inhibited by atropine, but in the presence of pyrilamine or verapamil, the effect was antagonized. Contrastingly, on KCl- or histamine-induced contractions, OC-EtOH presented a transient contraction followed by a concentration-dependent relaxation. Moreover, OC-EtOH presented a relaxant profile on cumulative curves to CaCl2 and tonic contraction induced by S-(-)-BayK8644, through Cav blockade. The acute toxicity assay showed that OC-EtOH (2,000 mg/kg, p.o.) did not present any sign of toxicity in female mice. Additionally, OC-EtOH presented antidiarrheal effect in mice, increased the intestinal normal transit and reduced the castor oil-induced intestinal transit. Thus, OC-EtOH presented a dual effect on guinea pig ileum promoting contraction through activation of H1 and CaV, and relaxation through CaV blockade, besides the effect on upper gastrointestinal transit in mice, showing a potential medicinal use of this sponge in intestinal diseases such as diarrhea.

Evaluation of acute oral toxicity, embryotoxicity and cytotoxicity of the polar fraction of Parkinsonia aculeata aerial parts extract.

Ethnopharmacobotanical information reports that Parkinsonia aculeata infusion is used to control diabetes-related complications and dyslipidemia. However, few studies are reported on the safe use of this species. The aim of this study is to evaluate the acute toxicity, embryotoxicity and cytotoxicity of a polar fraction obtained from hydroethanolic extract of P. aculeata (PfrHEPA). For the acute toxicity test, we considered the Up and Down method which the guidelines are described by the Organization for Economic Cooperation and Development (OECD N°425). The animals were treated with PfrHEPA (2000 mg/kg) or with distilled water (10 ml/kg) by gavage and observed from Day 1 to14. For embryotoxicity assay, zebrafish embryos were exposed to PfrHEPA (100 mg/L) and toxicity parameters were observed during four consecutive days. The cytotoxicity of PfrHEPA (5, 10, 25, 50, 75 and 100 µg/ml, respectively) was performed on normal cell lines (mesenchymal stem cells, African green monkey renal cells and mouse pre-adipocytes 3 T3-L1 using the MTT salt reduction assay. In the acute toxicity test, no mortality was observed in mice treated with PfrHEPA (2000 mg/kg), as well as behavioral changes, histopathological abnormalities and hematological and biochemical variables. In the embryotoxicity test, no abnormal changes related to the toxicological parameters were observed in the period of 96 h. Regarding the cytotoxicity assay, PfrHEPA showed no cytotoxic effect on the normal cell lines tested, with an IC50 value > 100 µg/ml. These results suggest the safe use of P. aculeata, however, more trials are needed for PfrHEPA to be presented as new safe therapeutic proposal for the control of metabolic disorders.

Anti-inflammatory and antinociceptive activities of the leaf methanol extract of Miconia minutiflora (Bonpl.) DC. and characterization of compounds by UPLC-DAD-QTOF-MS/MS.

Some species of the genus Miconia are used in Brazilian folk medicine as analgesic and anti-inflammatory; however, several species of this genus are still poorly studied. Therefore, the aims of this study were to investigate the phytochemistry characterization by UPLC-DAD-QTOF-MS/MS, acute toxicity, anti-inflammatory and antinociceptive properties of Miconia minutiflora (Bonpl.) DC. The methanol extract of M. minutiflora (Mm-MeOH) was subjected to ultra-high-performance liquid chromatography (UPLC-DAD-QTOF-MS/MS) for the identification of the main phytocompounds. The anti-inflammatory properties of the extracts were studied using several inflammation models induced by carrageenan and acetic acid-induced vascular permeability. Antinociceptive effects of Mm-MeOH were assessed in nociception induced by intraperitoneal acetic acid or subplantar formalin injection. The role of α-adrenergic, cholinergic, and opioid receptors in modulating the extract's antinociceptive activity was determined. Analyses by UPLC-DAD-QTOF-MS/MS revealed the presence of ellagic acid, gallotannin, and terpenes in the methanol extract. Mm-MeOH (100 mg/kg) reduced carrageenan-induced paw edema and vascular permeability and inhibited leukocyte migration toward the air pouch and pleural cavity. Furthermore, Mm-MeOH decreased tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) levels. Administration of Mm-MeOH reduced the number of writhes by 58.9% and increased the pain threshold in the formalin test. The anti-inflammatory action mechanism of Mm-MeOH is associated with inhibition of proinflammatory cytokines TNF-α and IL-1ß, whereas the antinociceptive actions involve peripheral and central mechanisms with participation of α2-adrenergic receptors. These effects may be attributed to the presence of polyphenolics in the extract.

ß-Lapachone and its iodine derivatives cause cell cycle arrest at G2/M phase and reactive oxygen species-mediated apoptosis in human oral squamous cell carcinoma cells.

ß-Lapachone is a natural naphthoquinone originally obtained from the bark of the purple Ipe (Tabebuia avellanedae Lor, Bignoniaceae) and its therapeutic potential in human cancer cells has been evaluated in several studies. In this study, we examined the effects of ß-lapachone and its 3-iodine derivatives (3-I-α-lapachone and 3-I-ß-lapachone) on cell proliferation, cell death, and cancer-related gene expression in human oral squamous cell carcinoma cells. ß-Lapachone and its 3-iodine derivatives showed potent cytotoxicity against different types of human cancer cell lines. Indeed, treatment with these compounds induced cell cycle arrest at G2/M phase, followed by internucleosomal DNA fragmentation, and caused significant increases in phosphatidylserine externalization, caspase-8 and -9 activation, mitochondrial membrane depolarization, reactive oxygen species (ROS) production, and apoptotic cell death morphology. The apoptosis induced by the compounds was prevented by pretreatment with a pan-caspase inhibitor (Z-VAD-FMK) and an antioxidant (N-acetyl-l-cysteine). In vivo, ß-lapachone and its 3-iodine derivatives significantly reduced tumor burden and did not alter any of the biochemical, hematological, or histological parameters of the animals. Overall, ß-lapachone and its 3-iodine derivatives showed promising cytotoxic activity due to their ability to induce cell cycle arrest at G2/M phase and promote caspase- and ROS-mediated apoptosis. In addition, ß-lapachone and its 3-iodine derivatives were able to suppress tumor growth in vivo, indicating that these compounds may be new antitumor drug candidates.

Antioxidant and Antihypertensive Effects of a Chemically Defined Fraction of Syrah Red Wine on Spontaneously Hypertensive Rats.

A particularly phenolic-rich fraction extracted from red wine from the São Francisco valley (Northeastern Brazil) was chemically characterized and its hypotensive and antioxidant effects on spontaneously hypertensive rats were studied both in vitro and in vivo. The liquid-liquid pH dependent fractionation scheme afforded a fraction with high content of bioactive phenolics such as flavonols, flavonol glycosides, phenolic acids and anthocyanins, whose identities were confirmed by liquid chromatography coupled to mass spectrometry analysis. Pretreatment of spontaneously hypertensive rats with this wine fraction at doses of 50 and 100 mg/kg by gavage. for 15 days was able to decrease mean arterial pressure and heart rate as well as decrease serum lipid peroxidation. The fraction at concentrations of 0.01-1000 µg/mL induced concentration-dependent relaxation of isolated rat superior mesenteric artery rings pre-contracted with phenylephrine and this effect was not attenuated by endothelium removal. Our results demonstrate it is possible for phenolic constituents of red wine that are orally bioavailable to exert in vivo hypotensive and antioxidant effects on intact endothelial function.

Molluscicidal activity of Solanum species of the Northeast of Brazil on Biomphalaria glabrata.

Seven species of Solanum were screened for their molluscicidal properties against Biomphalaria glabrata, the intermediated host of Schistosoma mansoni, Solanum agrarium, S. jabrense, S. melissarum, S. megalonyx, S. paludosum, S. paraibanum and S. stipulaceum. Four extracts showed molluscicidal activity with LC(50) from 22 to 56 microg/ml.

Isoflavone formononetin from red propolis acts as a fungicide against Candida sp.

A bioassay-guided fractionation of two samples of Brazilian red propolis (from Igarassu, PE, Brazil, hereinafter propolis 1 and 2) was conducted in order to determine the components responsible for its antimicrobial activity, especially against Candida spp. Samples of both the crude powdered resin and the crude ethanolic extract of propolis from both locations inhibited the growth of all 12 tested Candida strains, with a minimum inhibitory concentration of 256µg/mL. The hexane, acetate and methanol fractions of propolis 1 also inhibited all strains with minimum inhibitory concentration values ranging from 128 to 512µg/mL for the six bacteria tested and from 32 to 1024µg/mL for the yeasts. Similarly, hexane and acetate fractions of propolis sample 2 inhibited all microorganisms tested, with minimum inhibitory concentration values of 512µg/mL for bacteria and 32µg/mL for yeasts. The extracts were analyzed by HPLC and their phenolic profile allowed us to identify and quantitate one phenolic acid and seven flavonoids in the crude ethanolic extract. Formononetin and pinocembrin were the major constituents amongst the identified compounds. Formononetin was detected in all extracts and fractions tested, except for the methanolic fraction of sample 2. The isolated isoflavone formononetin inhibited the growth of all the microorganisms tested, with a minimum inhibitory concentration of 200µg/mL for the six bacteria strains tested and 25µg/mL for the six yeasts. Formononetin also exhibited fungicidal activity against five of the six yeasts tested. Taken together our results demonstrate that the isoflavone formononetin is implicated in the reported antimicrobial activity of red propolis.

Antibiotic-modifying activity of riachin, a non-cyanogenic cyanoglycoside extracted from Bauhinia pentandra.

BACKGROUND: The search for new active compounds from the Brazilian flora has intensified in recent years, especially for new drugs with antibiotic potential. Accordingly, the aim of this study was to determine whether riachin has antibiotic activity in itself or is able to modulate the activity of conventional antibiotics. METHODS: A non-cyanogenic cyanoglycoside known as riachin was isolated from Bauhinia pentandra, and was tested alone and in combination with three antibiotics (clindamycin, amikacin, and gentamicin) against multiresistant bacterial strains (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus). RESULTS: Riachin did not show significant antibiotic activity when tested alone against any strain (P>0.05). However, when combined with conventional antibiotics, it showed drug-modifying activity against strains of S. aureus exposed to clindamycin (P<0.001) as well as against P. aeruginosa exposed to amikacin (P<0.001). Although riachin did not show direct antibiotic activity, it had synergistic activity when combined with amikacin or clindamycin. The mechanism of action of this synergism is under investigation. CONCLUSION: The results of this work demonstrate that some substances of natural origin can enhance the effectiveness of certain antibiotics, which means a substantial reduction in the drug dose required and possibly in consequent adverse events for patients.