Background: The antimicrobial activity of essential oils has been reported in hundreds of studies, however, the great majority of these studies attribute the activity to the most prevalent compounds without analyzing them independently. Therefore, the aim was to investigate the antibacterial activity of 33 free terpenes commonly found in essential oils and evaluate the cellular ultrastructure to verify possible damage to the cellular membrane. Methods: Screening was performed to select substances with possible antimicrobial activity, then the minimal inhibitory concentrations, bactericidal activity and 24-h time-kill curve studies were evaluated by standard protocols. In addition, the ultrastructure of control and death bacteria were evaluated by scanning electron microscopy. Results: Only 16 of the 33 compounds had antimicrobial activity at the initial screening. Eugenol exhibited rapid bactericidal action against Salmonella enterica serovar Typhimurium (2 h). Terpineol showed excellent bactericidal activity against S. aureus strains. Carveol, citronellol and geraniol presented a rapid bactericidal effect against E. coli. Conclusions: The higher antimicrobial activity was related to the presence of hydroxyl groups (phenolic and alcohol compounds), whereas hydrocarbons resulted in less activity. The first group, such as carvacrol, l-carveol, eugenol, trans-geraniol, and thymol, showed higher activity when compared to sulfanilamide. Images obtained by scanning electron microscopy indicate that the mechanism causing the cell death of the evaluated bacteria is based on the loss of cellular membrane integrity of function. The present study brings detailed knowledge about the antimicrobial activity of the individual compounds present in essential oils, that can provide a greater understanding for the future researches.

Yacon (Smallanthus sonchifolius) is a tuberous root with a high phenolic compounds and fibers content which has a prebiotic effect, both important for preventing and/or promoting the reduction of non-communicable chronic diseases risks. However, this root’s shelf life is highly reduced and culminates the reduction of the beneficial to health compounds, which can be avoided by some strategies. In this sense, this work aimed to produce yacon beverages added with anti-browning agents (cysteine or citric acid) and evaluated the spontaneous fermentation during storage. Three yacon beverages have been produced with cysteine or citric acid (0.05% w/w) and a control beverage. Beverages were analyzed by microbiological counts, nutritional composition, physical-chemical characteristics, total phenolic compounds and phenolic acids, for 60 day storage. The data were evaluated by ANOVA and compared using the Duncan test (p≤0.05) or regression models were adjusted. Regarding microorganisms, all beverages have reached 109 CFU.ml-1 after 30 day storage. To the anti-browning agents use, the differences were occasional; however, the citric acid beverage had a desirable pH (< 4.5) for a fermented beverage, which allows inhibition of undesirable bacteria and a higher proportional initial FOS amount and less variation with 30 and 60 day storage. However, the citric acid beverage have presented smaller amount of phenolic compounds like chlorogenic and gallic acids (230.37 ± 168.63 and 40.87 ± 1.32, respectively). So, we conclued that spontaneous fermentation was a preparation technique which has added nutritional and functionals values to the yacon beverage, in special to beverage added citric acid, with a higher proportion of FOS.

This study evaluated the composition and the cancer chemopreventive and antioxidant activities of the seed, skin, and pulp of Maximo hybrid grapes (IAC 138-22) harvested at different ripening stages. The content of total phenolic compounds and tannins were determined by the Folin-Ciocaulteau method, and total anthocyanins were determined using the differential pH method. Different chemical methods assessed the antioxidant activity. Cell viability (macrophage and melanoma skin cancer) and cancer chemopreventive activity were tested in cell lines by quinone reductase induction assay, TNF-α-induced NF-κB inhibitory activity assay, and aromatase inhibitory activity assay. The hybrid grape had high phenolic contents in both seeds and skin, significantly reduced upon ripening. The results showed that fruit ripening significantly affected both the composition and the antioxidant and cancer chemopreventive activities. Except for the anthocyanin content, the most significant results were observed for green seeds, with the greenest stage showing the best results. The green seeds showed the highest antioxidant activity, even when compared to free resveratrol. In the assessment of cancer chemopreventive activity, the green seeds showed the ability to inhibit N-FκB and aromatase activity, important factors for the early stage of cancer development. Besides, no extracts showed cytotoxicity. Therefore, this grape’s green seeds showed strong antioxidant and cancer chemopreventive activities confirmed herein, suggesting beneficial health effects.