Antimicrobial activity and composition profile of grape (Vitis vinifera) pomace extracts obtained by supercritical fluids.

The possibility of increasing the aggregated value of the huge amount of residues generated by wineries around the world foment studies using the grape pomace - the residue from the wine production, composed by seed, skin and stems - to obtain functional ingredients. Nowadays, consumers in general prefer natural and safe products mainly for food and cosmetic fields, where the supercritical fluid extraction is of great importance due to the purity of the extracts provided. Therefore, the objective of this work is to evaluate the global extraction yield, the antimicrobial activity and the composition profile of Merlot and Syrah grape pomace extracts obtained by supercritical CO2 (SC-CO2) and CO2 added with co-solvent at pressures up to 300 bar and temperatures of 50 and 60 °C. The results were compared with the ones obtained by Soxhlet and by ultrasound-assisted leaching extraction methods. The main components from the extracts, identified by HPLC, were gallic acid, p-OH-benzoic acid, vanillic acid and epicatechin. The antibacterial and antifungal activities of the extracts were evaluated using four strains of bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa) and three fungi strains (Candida albicans, Candida parapsilosis, Candida krusei). Despite lower extraction yield results, the supercritical fluid extracts presented the highest antimicrobial effectiveness compared to the other grape pomace extracts due to the presence of antimicrobial active compounds. Syrah extracts were less efficient against the microorganisms tested and Merlot extracts were more active against Gram-positive bacteria.

Chemical composition and antibacterial activity of Cordia verbenacea extracts obtained by different methods.

The present study describes the chemical composition and the antibacterial activity of extracts from Cordia verbenacea DC (Borraginaceae), a traditional medicinal plant that grows widely along the southeastern coast of Brazil. The extracts were obtained using different extraction techniques: high-pressure operations and low-pressure methods. The high-pressure technique was applied to obtain C. verbenacea extracts using pure CO(2) and CO(2) with co-solvent at pressures up to 30MPa and temperatures of 30, 40 and 50 degrees C. Organic solvents such as n-hexane, ethyl acetate, ethanol, acetone and dichloromethane were used to obtain extracts by low-pressure processes. The antibacterial activity of the extracts was also subjected to screening against four strains of bacteria using the agar dilution method. The extraction yields were up to 5.0% w/w and up to 8.6% w/w for supercritical fluid extraction with pure CO(2) and with ethyl acetate as co-solvent, respectively, while the low-pressure extraction indicates yields up to 24.0% w/w in the soxhlet extraction using water and aqueous mixture with 50% ethanol as solvents. The inhibitory activity of the extracts in gram-positive bacteria was significantly higher than in gram-negative. The quantification and the identification of the extracts recovered were accomplished using GC/MS analysis. The most important components identified in the extract were artemetin, beta-sitosterol, alpha-humulene and beta-caryophyllene, among others.

Antifungal activity of coumarins.

The antifungal activity of 40 coumarins was tested against the fungal strains: Candida albicans (ATCC 14053), Aspergillus fumigatus (ATCC 16913) and Fusarium solani (ATCC 36031), using the broth microdilution method. Osthenol showed the most effective antifungal activity among all the compounds tested, with a MIC value of 125 microg/ml for Fusarium solani and 250 micro/ml for Candida albicans and Aspergillus fumigatus. The antifungal potential of this prenylated coumarin can be related to the presence of an alkyl group at C-8 position.

Screening methods to determine antibacterial activity of natural products

The emergence of new infectious diseases, the resurgence of several infections that appeared to have been controlled and the increase in bacterial resistance have created the necessity for studies directed towards the development of new antimicrobials. Considering the failure to acquire new molecules with antimicrobial properties from microorganisms, the optimization for screening methods used for the identification of antimicrobials from other natural sources is of great importance. The objective of this study was to evaluate technical variants used in screening methods to determine antibacterial activity of natural products. Thus, a varied range of natural products of plant, fungi and lichen origin were tested against two bacterial species, Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922, by two variants of the agar diffusion method (well and disc), two variants of the bioautographic method (direct and indirect) and by microdilution assay. We concluded that the well-variant of the diffusion method was more sensitive than the disc-variant, whilst the direct-variant of the bioautographic method exhibited a greater sensitivity if compared to indirect-variant. Bioautographic and diffusion techniques were found to have similar sensitivity; however the latter technique provided more suitable conditions for the microbial growth. In this study, we also discussed the best conditions for the determination of minimal inhibitory concentration.

Com o surgimento de novas doenças infecciosas, o reaparecimento de várias infecções que pareciam ter sido controladas, e o aumento da resistência bacteriana houve a necessidade de pesquisas dirigidas ao desenvolvimento de novos antimicrobianos. Levando em consideração a dificuldade de aquisição de novas moléculas com atividades antimicrobianas, a otimização de métodos de triagem usados na identificação de antimicrobianos de fontes naturais é de grande importância. O objetivo deste estudo foi avaliar variantes técnicas, usadas em métodos de triagem para determinar atividade antibacteriana de produtos naturais. Assim, vários produtos naturais, oriundos de plantas, fungos e líquens foram testados contra duas espécies bacterianas, Staphylococcus aureus ATCC 25923 e Escherichia coli ATCC 25922, por duas variantes do método de difusão em ágar (poço e disco), duas variantes do método bioautográfico (direto e indireto) e por testes de microdiluição. Concluímos que a variante do método de difusão variante poço foi mais sensível do que a variante disco, enquanto que a variante direta do método bioautográfico exibiu uma sensibilidade maior, comparada com a variante indireta. As técnicas de bioautografia e difusão mostraram sensibilidades similares, embora a última tenha fornecido condições mais apropriadas para o crescimento bacteriano. Neste estudo, também discutimos as melhores condições para a determinação da concentração inibitória mínima.

Derivatization does not influence antimicrobial and antifungal activities of applanoxidic acids and sterols from Ganoderma spp.

Applanoxidic acids and sterols, isolated from Ganoderma spp., were acetylated and/or methylated. The antibacterial activity against Escherichia coli and Staphylococcus aureus and the antifungal activity against Candida albicans and Trichophyton mentagrophytes of the derivatives were investigated by a microdilution method, and compared with those of the natural products. Both natural and modified compounds exhibited comparable antibacterial and antifungal activities in a range of 1.0 to > 2.0 mg/ml minimal inhibitory concentration.