BackgroundChemical reduction has become an accessible and useful alternative to obtain silver nanoparticles (AgNPs). However, its toxicity capacity depends on multiple variables that generate differences in the ability to inhibit the growth of microorganisms. Thus, optimazing parameters for the synthesis of AgNPs can increase its antimicrobial capacity by improving its physical-chemical properties.MethodsIn this study a Face Centered Central Composite Design (FCCCD) was carried out with four parameters: AgNO3 concentration, sodium citrate (TSC) concentration, NaBH4 concentration and the pH of the reaction with the objective of inhibit the growth of microorganisms. The response variables were the average size of AgNPs, the peak with the greatest intensity in the size distribution, the polydispersity of the nanoparticle size and the yield of the process. AgNPs obtained from the optimization were characterized physically and chemically. The antimicrobial activity of optimized AgNPs was evaluated against Staphylococcus aureus, Escherichia coli, Escherichia coli AmpC resistant, and Candida albicans and compared with AgNPs before optimization. In addition, the cytotoxicity of the optimized AgNPs was evaluated by the colorimetric assay MTT (3- (4,5- Dimethylthiazol- 2- yl)- 2, 5 - Diphenyltetrazolium Bromide).ResultsIt was found that the four factors studied were significant for the response variables, and a significant model (p < 0.05) was obtained for each variable. The optimal conditions were 8 for pH and 0.01 M, 0.0 6M, 0.01 M for the concentration of TSC, AgNO3, and NaBH4, respectively. Optimized AgNPs spherical and hemispherical were obtained, and 67.66% of it had a diameter less than 10.30 nm. A minimum bactericidal concentration (MBC) and minimum fungicidal Concentration (MFC) of optimized AgNPs was found against Staphylococcus aureus, Escherichia coli, Escherichia coli AmpC resistant, and Candida albicans at 19.89, 9.94, 9.94, 2.08 μg/mL, respectively. Furthermore, the lethal concentration 50 (LC50) of optimized AgNPs was found on 19.11 μg/mL and 19.60 μg/mL to Vero and NiH3T3 cells, respectively.ConclusionsIt was found that the factors studied were significant for the variable responses and the optimization process used was effective to improve the antimicrobial activity of the AgNPs.

This study deals with the extraction, optimization, and evaluation of the antioxidant and antimicrobial activities of bioactive compounds obtained from the seeds of annatto using microwave-assisted extraction as compared to leaching. Annatto seeds were subjected to a microwave treatment of 2450 MHz and power of 700 watts using a response surface design involving four factors: pH (4–11), solvent concentration (ethanol) (50–96 %), solvent-to-seed ratio (2–10), and microwave exposure time (0–5 min). The contents of polyphenol compounds and bixin were taken as response variables. Subsequently, the antioxidant and antimicrobial activities were assessed at the optimal processing conditions predicted by the experimental design. Microwaves, solvent concentration, and the solvent-to-seed ratio showed a statistically significant effect for the extraction of polyphenol compounds and bixin. Thus, microwaves accelerated the extraction of those compounds and the slight increase in temperature caused some degradation of the polyphenol compounds. The microwave-assisted extraction increased the contents of polyphenols and bixin along with their antioxidant activity as compared to leaching extraction. However, this technique does not significantly improve the antimicrobial activity against Bacillus cereus and Staphylococcus aureus.

This study evaluated the antimicrobial activity (i.e., against Bacillus cereus and Staphylococcus aureus) and the antioxidant activity (i.e., ABTS, FRAP, and DPPH) of annatto seeds extract obtained by ultrasound-assisted extraction. A response surface design with three levels such as pH (2-11), solvent concentration (50-96 %), seed-to-solvent ratio (1:2–1:10), and treatment time (0-30 min) was employed to determine the optimal experimental conditions. Thus, a pH of 7.0, seed-to-solvent ratio of 1:7, and treatment time of 20 min were selected as optimal rendering an extract having a 0.62% of bixin, 3.81 mg gallic acid/mg equivalent of polyphenol compounds (ABTS 1035.7, FRAP 424.7, and DPPH 1161.5 μM trolox/L), and a minimal inhibitory concentration against Bacillus cereus and Staphylococcus aureus of 32 and 16 mg/L, respectively. Further, the main bioactive compounds identified by LC/ESI-MS were bixin and catechin, chlorogenic acid, chrysin, butein, hypolaetin, licochalcone A, and xanthohumol.

Colombian berry (agraz) has demonstrated a high antioxidant content in vitro. On the present study, it was elaborated and characterized an agraz nectar, designed a placebo with similar physicochemical and sensorial characteristics of the agraz nectar, but without polyphenols; and evaluated their antioxidant capacity both in vitro and in vivo in adults with cardiovascular risk factors. The polyphenolic concentration of the agraz nectar and its antioxidant capacity was superior than other reported for this fruit. A high content of total cyanidins was observed in the freeze-dried agraz, but not delphinin was detected by HPLC. For the intervention study, sixty-six subjects, with at least three cardiometabolic risk factors, consumed agraz nectar or placebo daily during 4 weeks each, separated by a 4-week washout period. Total phenol concentration and antioxidant capacity in the participants' serum were not statistically different after consuming agraz nectar and placebo. However, women increased significantly their serum DPPH scavenging capacity after consuming agraz nectar, compared to placebo. This is one of the first studies showing data about the effects of this colombian berry on the antioxidant capacity in people with metabolic syndrome.