Antibacterial and antibiofilm activities of quercetin against clinical isolates of Staphyloccocus aureus and Staphylococcus saprophyticus with resistance profile

The aim of this study was to determine the antibacterial and antibiofilm properties of quercetin against clinical isolates of Staphyloccocus aureus and Staphylococcus saprophyticus with resistance profile. The antibacterial activity of quercetin was performed by the determination of the minimum inhibitory concentration (MIC) through the microdilution method according to the Clinical and Laboratory Standards Institute (CLSI). The percentage of inhibition of Staphylococcus spp. biofilm, after treatment with sub-inhibitory concentrations of quercetin (MIC/2 and MIC/4), was evaluated by the violet crystal assay. Quercetin showed an antimicrobial activity against clinical isolates of methicillin-susceptible S. aureus (MSSA) (MIC = 250 µg/ml), methicillin-resistant S. aureus (MRSA) (MIC = 500 µg/ml), vancomycin-intermediate S. aureus (VISA) (MIC = 125 and 150 µg/ml), S. saprophyticus resistant to oxacillin (MIC = 62.5 to 125 µg/ml), vancomycin-resistant S. aureus (VRSA) and S. saprophyticus resistant to oxacillin and vancomycin (MIC = 500 to 1000 µg/ml). At MIC/2 and MIC/4 the quercetin inhibit 46.5 ± 2.7% and 39.4 ± 4.3% of the S. aureus biofilm, respectively, and 51.7 ± 5.5% and 46.9 ± 5.5% of the S. saprophyticus biofilm, respectively. According to the results of this study, it was noticed that the quercetin presented an antibacterial activity against strains of Staphylococcus spp. with resistance profile and also inhibited the bacterial biofilm production even in sub-inhibitory concentrations

Validation of an UV spectrophotometric method for determining diffractaic acid from Usnea sp. in inclusion complexes with hydroxypropyl-β-cyclodextrin

Diffractaic acid (DA) presents several biological activities. The goal of this study was to develop and validate a UV spectrophotometric method for determining diffractaic acid in inclusion complexes with hydroxypropyl-β-cyclodextrin. Validation parameters were determined according to international guidelines for standardization. The linearity range of analytical curve was from 1 to 5 μg/mL and the regression equation: CDA = (Area - 0.0053)/0.1541 (r2 = 0.99998; n = 3). The intermediate precision indicated that the difference between the means was statistically insignificant (p < 0.05). Accuracy revealed a mean recovery percentage of diffractaic acid in inclusion complexes of 100.1 %. The method was robust and the formulation excipients did not interfere on diffractaic acid quantification. Limits of detection and quantification of diffractaic acid were 0.03 and 0.08 μg/mL, respectively. The proposed method proved to be accurate, precise and reproducible, thus being able to quantify diffractaic acid in raw material and inclusion complexes.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Validation of a UV spectrophotometric method for determining trans-dehydrocrotonin in inclusion complexes with hydroxypropyl-β-cyclodextrin

Trans-dehydrocrotonin (t-DCTN) is a 19-nor-clerodan diterpen with several important pharmacological properties, including hypoglycemic and antitumor activity. However the low water solubility and hepatotoxicity of t-DCTN limit its use in therapeutic applications. Drug inclusion complexes with cyclodextrins (CDs) can modify physicochemical properties of parent drugs, such as improving their aqueous solubility and reducing their toxicity. A UV method was therefore validated for determining t-DCTN in HP-β-CD inclusion complexes with a view to future applications in research and therapy. The regression equation of the analytical curve (1–20 μg/mL) was [t-DCTN] = absorbance + 0.00147/0.04214. The precision of the method was satisfactory, producing values of relative standard deviation less than 2 % for all samples analyzed. The accuracy was between 99.6 and 100.02 %. The content of t-DCTN in tDCTN:HP-β-CD was 99.8 %. The UV validated method developed is straightforward and suitable for use in the routine analysis of t-DCTN complexed with hydroxypropyl-β-cyclodextrin.Colegio de Farmacéuticos de la Provincia de Buenos Aire

A new transdermal drug delivery system containing hydroquinone

Hydroquinone (HQ) is a drug reported to possess manifold biological activities. HQ is highly unstable into various topical vehicles, presenting low topical bioavailability and a relevant level of toxicity. The Pluronic® Lecithin Organogel (PLOme) is a phospholipidic microemulsion designed for transdermal purposes. The aim of this work was therefore to incorporate HQ into PLOme. We evaluated the stability, the kinetic profile and the antimicrobial activity of HQ- incorporated PLOme. No relevant pH variation was observed. Long-term stability test showed an HQ degradation which led to a short shelf life. HQ permeation rate obtained was lower from PLOme than from a gel matrix. Free and PLOme-encapsulated hydroquinone showed to have a great in vitro inhibitory potential against of S. aureus strains. The encapsulation of HQ due its unstable characteristics could be an alternative to optimize its therapeutic usage, and so further investigation is required on this pharmaceutical form before commercialization.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Effects of the encapsulation of usnic acid into liposomes and interactions with antituberculous agents against multidrug-resistant tuberculosis clinical isolates

Mycobacterium tuberculosis (Mtb) has acquired resistance and consequently the antibiotic therapeutic options available against this microorganism are limited. In this scenario, the use of usnic acid (UA), a natural compound, encapsulated into liposomes is proposed as a new approach in multidrug-resistant tuberculosis (MDR-TB) therapy. Thus the aim of this study was to evaluate the effect of the encapsulation of UA into liposomes, as well as its combination with antituberculous agents such as rifampicin (RIF) and isoniazid (INH) against MDR-TB clinical isolates. The in vitro antimycobacterial activity of UA-loaded liposomes (UA-Lipo) against MDR-TB was assessed by the microdilution method. The in vitro interaction of UA with antituberculous agents was carried out using checkerboard method. Minimal inhibitory concentration values were 31.25 and 0.98 µg/mL for UA and UA-Lipo, respectively. The results exhibited a synergistic interaction between RIF and UA [fractional inhibitory concentration index (FICI) = 0.31] or UA-Lipo (FICI = 0.28). Regarding INH, the combination of UA or UA-Lipo revealed no marked effect (FICI = 1.30-2.50). The UA-Lipo may be used as a dosage form to improve the antimycobacterial activity of RIF, a first-line drug for the treatment of infections caused by Mtb

Desenvolvimento e validação de método analítico em CLAE-UV para a quantificação de ácido retinóico em microcápsulas de alginato e quitosana

O ácido retinóico (AR) tem sido utilizado para o tratamento de acne severa, rugas, estrias e celulite, no entanto, provoca irritação na pele e sofre rápida degradação quando exposto à luz e ao calor. Métodos analíticos rápidos para quantificação do AR são, portanto, necessários para ensaios de cinética de liberação in vitro. Nesse contexto, o objetivo deste trabalho foi desenvolver e validar um método rápido e sensível para o doseamento do AR em microcápsulas de alginato/quitosana contendo óleo de babaçu dispersas em gel natrosol® por cromatografia líquida de alta eficiência associada à espectroscopia UV e aplicá-lo na avaliação do perfil de liberação in vitro dessas formulações. As análises foram realizadas em modo isocrático utilizando coluna C18 de fase reversa 150 x 4,6 mm (5 &#956;m) com detecção a 350 nm. A fase móvel foi constituída de metanol e ácido acético 1% (85:15 v/v) com vazão de 1,8 mL/minuto. A faixa de linearidade do método foi de 0,5 a 60 &#956;g/mL (r² = 0,999). O método validado mostrou-se sensível, específico, exato, preciso, de baixo custo e o tempo de retenção do AR foi de 5,8 ± 0,4 minutos sendo, desta forma, mais rápido do que os relatados na literatura.<br>Retinoic acid (RA) has been used in the treatment of severe acne, wrinkles and cellulite. However, it induces skin irritation and rapidly suffers degradation under light and high temperate exposure. Rapid analytical methods to quantify retinoic acid are therefore mandatory for in vitro drug release studies. In this framework, the aim of this study was to develop and validate a rapid and responsive method to quantify the RA in microcapsules of chitosan and alginate containing babassu oil dispersed in natrosol® hydrogel using high performance liquid chromatography (HPLC). Furthermore this method was used to quantify in vitro release kinetics of RA from microcapsules. The analyses have been carried through an isocratic HPLC-UV method using a reversed phase 150 x 4.6 mm C18 (5&#956;m) column, a mobile phase constituted of methanol and 1% acetic acid (85:15) at a flow rate of 1.8 mL/min and detection at 350 nm. The linearity range was 0.5-60 &#956;g/mL (r² = 0.999). The validated HPLC-UV method was responsive, specific, accurate, precise, and economic and the RA retention time was 5.8 ± 0.4 minutes, being therefore, faster than that previously reported