Modulation of Drug Resistance by Limonene: Inhibition of Efflux Pumps in Staphylococcus aureus Strains RN-4220 and IS-58.

AIMS: This study aimed to investigate the potential of limonene as an efflux pump (EP) inhibitor in Staphylococcus aureus strains, RN-4220 and IS-58, which carry EPs for erythromycin (MrsA) and tetracycline (TetK), respectively. BACKGROUND: The evolution of bacterial resistance mechanisms over time has impaired the action of most classes of antibiotics. Staphylococcus aureus is a notable bacterium, with high pathogenic potential and demonstrated resistance to conventional antibiotics. Considering the importance of discovering novel compounds to combat antibiotic resistance, our group previously demonstrated the antibacterial properties of limonene, a compound present in the essential oils of several plant species. OBJECTIVE: This study aimed to investigate the potential of limonene as an efflux pump (EP) inhibitor in Staphylococcus aureus strains RN-4220 and IS-58, which carry EPs for erythromycin (MrsA) and tetracycline (TetK), respectively. METHODS: The minimum inhibitory concentrations (MIC) of limonene and other efflux pump inhibitors were determined through the broth microdilution method. A reduction in the MIC of ethidium bromide was used as a parameter of EP inhibition. RESULT: While limonene was not shown to exhibit direct antibacterial effects against EP-carrying strains, in association with ethidium bromide and antibiotics, this compound demonstrated enhanced antibacterial activity, indicating the inhibition of the MrsA and TetK pumps. CONCLUSION: In conclusion, this pioneering study demonstrated the effectiveness of limonene as an EP inhibitor in S. aureus strains, RN-4220 and IS-58. Nevertheless, further studies are required to characterize the molecular mechanisms associated with limonene-mediated EP inhibition.

Inhibition of Efflux Pumps by Monoterpene (α-pinene) and Impact on Staphylococcus aureus Resistance to Tetracycline and Erythromycin.

INTRODUCTION: Infectious diseases have been responsible for an increasing number of deaths worldwide. Staphylococcus aureus has been recognized as one of the most notable causative agents of severe infections, while efflux pump (EP) expression is one of the main mechanisms associated with S. aureus resistance to antibiotics. OBJECTIVE: This study aimed to investigate the potential of α-pinene as an efflux pump inhibitor in species of S. aureus carrying the TetK and MrsA proteins. METHODS: The minimum inhibitory concentrations (MIC) of α-pinene and other efflux pump inhibitors were assessed using serial dilutions of each compound at an initial concentration above 1024 µg/mL. Solutions containing culture medium and bacterial inoculums were prepared in test tubes and subsequently transferred to 96-well microdilution plates. The modulation of ethidium bromide (EtBr) and antibiotics (tetracycline and erythromycin) was investigated through analysis of the modification in their MICs in the presence of a subinhibitory concentration of α-pinene (MIC/8). Wells containing only culture medium and bacterial inoculums were used as negative control. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) was used as a positive control. RESULTS: The MIC of ethidium bromide against S. aureus strains RN-4220 and IS-58 was reduced by association with α-pinene. This monoterpene potentiated the effect of tetracycline against the IS-58 strain but failed in modulating the antibacterial effect of erythromycin against RN-4220, suggesting a selective inhibitory effect on the TetK EP by α- pinene. CONCLUSION: In conclusion, α-pinene has promising effects against S.aureus strains, which should be useful in the combat of antibacterial resistance associated with EP expression. Nevertheless, further research is required to fully characterize its molecular mechanism of action as an EP inhibitor.

In silico and In vivo Toxicological Evaluation of Cissampelos Sympodialis Secondary Metabolites in Rattus Norvegicus.

Cissampelos sympodialis is a plant in northeastern Brazil used by the populace for treating respiratory diseases. Several studies have shown that ethanol leaf extracts have immunomodulatory and anti-inflammatory activities. Infusions are widely used, popular, and an ancient technique in traditional medicine, using hot water alone as the means of extraction. This study aimed to investigate acute toxicological potential of leaf infusions of Cissampelos sympodialis, when applied orally at a dose of 2000mg/kg to Rattus norvegicus, combined with an in silico study of 117 alkaloids present in the Cissampelos genus; five (5) of which were determined to have high toxicity (21, 8, 93, 32 and 88), and five (5) having both low toxicity (57, 77, 28, 25 and 67) and low liver metabolism. The in vivo toxicological evaluation showed that male water consumption decreased, and the feed intake decreased in both sexes. Yet, the figures as to change in weight gain of the animals were not statistically sufficient. As for the biochemical parameters, there was an increase in urea, and decreases in uric acid and AST in males. In females, there was a decrease in albumin and globulin which consequently leads to a total protein decrease. Despite biochemical changes suggestive of kidney damage, the histological sections revealed no kidney or liver changes. The results therefore indicate that despite presenting alkaloids which may be toxic, the genus Cissampelos, or leaf infusions of Cissampelos sympodialis, when applied orally at a dose of 2000mg/kg present low toxicity.

Secondary Metabolites from Cissampelos, A Possible Source for New Leads with Anti-Inflammatory Activity.

The genus Cissampelos comprises of 21 species which have a wide global distribution and various pharmacological activities such as analgesic and antipyretic, antiinflammatory, anti-allergic, bronchodilation, and immunomodulation among others. Several compounds, mainly alkaloids with differing biological activities have been isolated from this genus. We will highlight antipyretic activities, anti-inflammatory, antiallergic, bronchodilatory, and immunomodulatory activities. In addition, we applied ligand-based-virtual screening associated with structure-based-virtual screening of a small dataset of 63 secondary metabolites from the Cissampelos genus of an in-house data bank, in order to select compounds with potential anti-inflammatory activity. Affinities were observed for hayatine (26), isochondrondendrine (30), pelosine (52), sepeerine (59), and warifteine (63) to the inhibiting enzymes MAPK p38 alpha, PKC beta, PKC theta and PKC zeta. The cissampeloflavone compound (8) alone showed no potential inhibitory activity for PKC zeta, or affinity for the PKC alpha. The compounds can be used as starting points for further studies on structures with potential anti-inflammatory activity.

Multi-Target Drugs for Neglected Diseases.

BACKGROUND: Diseases perceived as neglected tropical infections are generally caused by parasites which reach poor, underserved populations (primarily infrastructure), cause serious damage to health, and many deaths. AIDS and tuberculosis, (although not classified as neglected by WHO), are discriminated against infections which cause great social damage. The drugs currently used to treat these diseases do not have the desired effectiveness, enable the emergence of resistant strains, and in most cases are difficult to obtain. Few pharmaceutical companies are investing in new drug research for neglected diseases, for lack of financial return. This review reports the major neglected diseases, AIDS, tuberculosis, their targets, and research on multi-target drugs. METHODS: The studies for new drugs against these infections involve in silico methods, synthesis, structural determinations, analytical analysis and other experimental assays. RESULTS: A new single compound, forecasting possible pharmacodynamic and pharmacokinetic interactions becomes a simpler process; it is also believed that these drugs are safer and more efficient, since they act with synergism on different targets. It occurs but the emergence of new resistant strains and side effects. CONCLUSION: Multi-target drugs represent a new alternative to find new lead compounds. A ligand that targets two or more receivers may be seen as a potential drug, combating infection by different routes.

Antinociceptive and anti-inflammatory properties of 7-hydroxycoumarin in experimental animal models: potential therapeutic for the control of inflammatory chronic pain.

OBJECTIVES: In the present study we investigated the antinociceptive, anti-inflammatory and antipyretic effects of 7-hydroxycoumarin (7-HC) in animal models. METHODS: The effects of oral 7-HC were tested against acetic acid-induced writhing, formalin test, tail flick test, complete Freund's adjuvant (CFA)-induced hypernociception, carrageenan-induced paw oedema, lipopolysaccharide-induced fever and the rota rod test. KEY FINDINGS: 7-HC (3-60 mg/kg) produced a dose-related antinociception against acetic acid-induced writhing in mice and in the formalin test. In contrast, treatment with 7-HC did not prevent thermal nociception in the tail flick test. A single treatment with 7-HC, 60 mg/kg, produced a long-lasting antinociceptive effect against CFA-induced hypernociception, a chronic inflammatory pain stimulus. Notably, at 60 mg/kg per day over 4 days the administration of 7-HC produced a continuous antinociceptive effect against CFA-induced hypernociception. 7-HC (30-120 mg/kg) produced anti-inflammatory and antipyretic effects against carrageenan-induced inflammation and lipopolysaccharide-induced fever, respectively. Moreover, 7-HC was found to be safe with respect to ulcer induction. In the rota rod test, 7-HC-treated mice did not show any motor performance alterations. CONCLUSIONS: The prolonged antinociceptive and anti-inflammatory effects of 7-HC, in association with its low ulcerogenic activity, indicate that this molecule might be a good candidate for development of new drugs for the control of chronic inflammatory pain and fever.

ent-Trachylobane diterpenoids from Xylopia langsdorffiana.

Two new diterpenes of the ent-trachylobane type were isolated from the stems of Xylopia langsdorffiana, ent-7alpha-acetoxytrachyloban-18-oic acid (1) and ent-7alpha-hydroxytrachyloban-18-oic acid (2). The structures of these isolates were deduced by spectroscopic data interpretation. X-ray crystallography of 1 was used to confirm its structure. The cytotoxic activity of 1 against V79 fibroblasts and rat hepatocytes was investigated.