Davi Antas e Silva

Modulation of drug resistance in Staphylococcus aureus by a kaempferol glycoside from Herissantia tiubae (Malvaceae).

In an ongoing project to evaluate natural compounds isolated from plants from the Brazilian biodiversity as modulators of antibiotic resistance, kaempferol‐3‐O‐β‐d‐(6″‐E‐p‐coumaroyl) glucopyranoside (tiliroside), isolated from Herissantia tiubae (Malvaceae) was investigated using the strain SA‐1199B of Staphylococcus aureus, which overexpresses the norA gene encoding the NorA efflux protein which extrudes hydrophilic fluorquinolones and some biocides, such as benzalkonium chloride, cetrimide, acriflavine and ethidium bromide. The minimum inhibitory concentrations (MICs) of the antibiotics and biocides were determined by the microdilution assay in the absence and in the presence of sub‐inhibitory concentration of tiliroside. Although tiliroside did not display relevant antibacterial activity (MIC = 256 µg/mL), it modulated the activity of antibiotics, i.e. in combination with antibiotics a reduction in the MIC was observed for norfloxacin (16‐fold), ciprofloxacin (16‐fold), lomefloxacin (four‐fold) and ofloxacin (two‐fold), and an impressive reduction in the MICs for the biocides (up to 128‐fold). The results presented here represent the first report of a kaempferol glycoside as a putative efflux pump inhibitor in bacteria. The present finding indicates that H. tiubae (and broadly Malvaceae) could serve as a source of plant‐derived natural products that modulate bacterial resistance, i.e. a source of potential adjuvants of antibiotics. Copyright

Constituintes químicos, avaliação das atividades citotóxica e antioxidante de Mimosa paraibana Barneby (Mimosaceae)

The phytochemical study of Mimosa paraibana Barneby led to the isolation of its chemical constituents, through the usual chromatographic methods, and further structural identification, using 1H and 13C NMR spectroscopic methods based on one and two-dimensional techniques, in addition to comparison with literature data. From this pioneering investigation with M. paraibana, five constituents were isolated and identified from the chloroform extract: a mixture of β-sitosterol and stigmasterol, 151-hydroxy-phaeophytin A, 5,7-dihydroxyflavanone, ethyl 3,4,5-trihydroxybenzoate and p-coumaric acid. The antioxidant activity of the hexane, chloroform and ethyl acetate extracts of M. paraibana were measured using the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging assay and the results compared with standard ascorbic acid. The toxicity activity of the extracts were performed using the bioassay of Artemia salina.

Triterpenes and phenolic compounds isolated from the aerial parts of Herissantia tiubae and evaluation of 5,4′,-dihydroxy-3,6,7,8,3′-pentamethoxyflavone as a modulator of bacterial drug resistance

In our continuous study of the Malvaceae family, we describe here the isolation of four triterpenes (frideline, lupeol, cycloartenol, and cycloeucalenol), a steroid (β-sitosterol), and four phenolic compounds from the aerial parts of Herissantia tiubae (K. Schum.) Brizicky (i.e., a benzoic acid derivative, a coumarin and two flavonoids, kaempferol 7-O-α-l-rhamnopyranoside and 4′,5-dihydroxy-3,6,7,8,3′-pentamethoxyflavone). The structural identification of the compounds was made by comparison with literature data and spectral analysis, including two-dimensional NMR techniques. These compounds are reported here for the first time in genus Herissantia. The pentamethoxyflavone was assayed against strains of Staphylococcus aureus possessing efflux mechanisms of resistance to norfloxacin, tetracycline, and erythromycin. Although the compound did not display relevant antibacterial activity (MIC ≥ 512 μg/mL), it modulated the activity of antibiotics, i.e., in combination with antibiotics (at 128 μg/mL), a two-fold reduction in the MIC values for tetracycline and erythromycin, a 32-fold reduction in the MIC for norfloxacin were observed.

Bioassay-guided evaluation of antinociceptive effect of N-salicyloyltryptamine: a behavioral and electrophysiological approach.

We investigated the antinociceptive and nerve excitability effects of the N-salicyloyltryptamine (NST) NST-treated mice exhibited a significant decrease in the number of writhes when 100 and 200 mg/kg (i.p.) were administered (i.p.). This effect was not antagonized by naloxone (1.5 mg/kg, i.p.). NST inhibited the licking response of the injected paw when 100 and 200 mg/kg were administered (i.p.) to mice in the first and second phases of the formalin test. Because the antinociceptive effects could be associated with neuronal excitability inhibition, we performed the single sucrose gap technique and showed that NST (3.57 mM) significantly reduced (29.2%) amplitude of the compound action potential (CAP) suggesting a sodium channel effect induced by NST. Our results demonstrated an antinociceptive activity of the NST that could be, at least in part, associated to the reduction of the action potential amplitude. NST might represent an important tool for pain management.

Flavonoids from Herissantia tiubae.

ABSTRACT Four known flavones, 5-hydroxyauranetin, araneosol, calycopterin and sarothrin, were isolated from the aerial parts of Herissantia tiubae. (K. Schum) Brizicky (Malvaceae). Their structures were identified by the use of spectroscopic methods such as IR, UV, and mainly nuclear magnetic resonance, which included two-dimensional techniques (1H-1H COSY, NOESY, HETCOR, and HMBC). This is the first reported isolation of these compounds from the genus Herissantia..

Biological activity of Herissantia crispa (L.) Brizicky

The crude methanol extract (EMeOH) of the aerial parts of Herissantia crispa (L.) Brizicky, plant riches in flavonoids and without pharmacological studies, was tested to value its activity under the behaviour parameters and to determine the lethal dose (LD50) in mice; antimicrobial and antiulcerogenic activities. The EMeOH (5,000 mg/kg, v.o. or 2,000 mg/kg i.p.) did not alter the behaviour parameters and there were not mice deaths. The extract inhibited the bacterial growth. The EMeOH (750 mg/kg) showed anti-diarroeal activity. The EMeOH (250, 500 and 750 mg/kg) decreased the gastric lesions induced by 0.3 M HCl/ethanol 60% in mice. In conclusion, the EMeOH presents anti-ulcerogenic activity;, however it is necessary to value the antiulcerogenic activity in more specific models and to study the action mechanism by which the vegetable sample protects the gastric mucosa.

Anticonvulsant evaluation of Rauvolfia ligustrina Willd. ex Roem. & Schult., Apocynaceae, in rodents

O presente estudo buscou avaliar os efeitos do extrato etanolico das raizes de Rauvolfia ligustrina Willd. ex Roem. & Schult., Apocynaceae, (EER) e sua possivel atividade anticonvulsivante em roedores. No teste das convulsoes induzidas pelo pentilenotetrazol (PTZ) os animais tratados com EER, 250 mg/kg (i.p.), apresentaram aumento significativo (p<0,05) da latencia para o aparecimento das convulsoes (328,9±47,5) quando comparado aos do grupo controle (103,5±21,8) e reduziu o numero de obitos. Esse efeito foi bloqueado pela administracao do flumazenil. O EER produziu aumento significativo (p<0,05) na latencia nos testes da picrotoxina (PIC) e da estricnina (EST), nas maiores doses. No modelo do eletrochoque auricular o EER nao produziu alteracoes significativas em nenhum dos parâmetros avaliados. Entretanto, no modelo do abrasamento induzido pelo PTZ, a administracao com o EER produziu um efeito protetor, atenuando de forma significativa (p<0,05) o desenvolvimento e a severidade das crises convulsivas. Os resultados, sugerem que o EER induziu efeito anticonvulsivante em roedores e que o sistema GABAergico pode estar envolvido nessa resposta.

Anticonvulsant property of N-salicyloyltryptamine: evidence of enhance of central GABAergic neurotransmission

AIM: In the present study we verified the anticonvulsant properties of the new tryptamine analogue, N-salicyloyltryptamine (NST), in rodents. METHODS AND RESULTS: In the evaluation of the anticonvulsant activity, NST protected the animals from the incidence of seizures induced by pentylenetetrazole (PTZ) and picrotoxin (PIC), in doses of 100 and 200 mg/kg. NST (100 and 200 mg/kg, i.p.) significantly eliminated the extensor reflex of maximal electric-induced seizure tests in 40% of the experimental animals. However, in the PTZ model FLU (10 mg/kg, i.p.), an antagonist of the benzodiazepine (BZD) site in the GABAA-BZD receptor complex, inhibited the prolongation of seizure latency induced by NST. CONCLUSION: Our results demonstrated an anticonvulsant activity of the new analogue that could be, at least in part, associated to the involvement of the GABAergic mechanism.