Antibacterial effect against foodborne bacteria of plants used in traditional medicine in central Mexico: Studies in vitro and in raw beef

Effect of Partial Meat Replacement by Hibiscus sabdariffa By-Product and Pleurotus djamor Powder on the Quality of Beef Patties

The effects of Hibiscus sabdariffa (roselle; Hs) by-product (2-5%) and Pleurotus djamor (pink oyster; Pd) powder (5-7.5%) as meat replacers on the physicochemical and sensorial properties of beef patties were analyzed. The addition of these non-meat ingredients significantly decreased moisture and increased fiber content, and did not affect the protein level of the product. The antioxidant effect of the roselle by-product was limited, while Pleurotus djamor favored the oxidation processes. The samples supplemented with roselle by-product and mushroom powder presented significantly lower microbial counts (total viable counts, enterobacteria, and Pseudomonas) than control, but texture and sensorial parameters were significantly affected. The patties darkened due to the presence of the Hibiscus by-product, while the color of the samples containing 5% Pleurotus djamor was hardly modified. These samples, together with the control samples, were the most sensorially appreciated. The addition of these ingredients provoked a decrease in texture parameters, being less pronounced in the samples with only 2% of roselle by-product. In spite of the good antimicrobial and antioxidant properties of Hibiscus by-products, its inclusion in meat should be moderate (2-2.5%) to avoid consumer rejection when Pleurotus djamor is also included in the formulation.

Essential Oils of Aromatic Plant Species from the Atlantic Rainforest Exhibit Extensive Chemical Diversity and Antimicrobial Activity

Microbial resistance, caused by the overuse or inadequate application of antibiotics, is a worldwide crisis, increasing the risk of treatment failure and healthcare costs. Plant essential oils (EOs) consist of hydrophobic metabolites with antimicrobial activity. The antimicrobial potential of the chemical diversity of plants from the Atlantic Rainforest remains scarcely characterized. In the current work, we determined the metabolite profile of the EOs from aromatic plants from nine locations and accessed their antimicrobial and biocidal activity by agar diffusion assays, minimum inhibitory concentration, time-kill and cell-component leakage assays. The pharmacokinetic properties of the EO compounds were investigated by in silico tools. More than a hundred metabolites were identified, mainly consisting of sesqui and monoterpenes. Individual plants and botanical families exhibited extensive chemical variations in their EO composition. Probabilistic models demonstrated that qualitative and quantitative differences contribute to chemical diversity, depending on the botanical family. The EOs exhibited antimicrobial biocidal activity against pathogenic bacteria, fungi and multiple predicted pharmacological targets. Our results demonstrate the antimicrobial potential of EOs from rainforest plants, indicate novel macromolecular targets, and contribute to highlighting the chemical diversity of native species.

Antimicrobial Effects of Aqueous Extract from Calyces of Hibiscus sabdariffa in CD-1 Mice Infected with Multidrug-Resistant Enterohemorrhagic Escherichia coli and Salmonella Typhimurium

To determinate the antimicrobial effect of chloramphenicol and aqueous extract against multidrug-resistant enterohemorrhagic Escherichia coli (EHEC) and Salmonella enterica serovar Typhimurium in CD-1 mice. Aqueous extract was isolated from Hibiscus sabdariffa calyces. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of chloramphenicol and aqueous extract were determined for EHEC and S. Typhimurium. Nine groups of six mice each were formed. Three groups were inoculated orally with 1 × 10⁴ colony-forming units (CFU) of S. Typhimurium, three groups were inoculated with 1 × 10⁴ CFU of EHEC and the remaining three groups were not inoculated. Six hours postinoculation, the mice of some groups were orally administered solutions of aqueous extract (50 mg/mL), chloramphenicol (82 μg/mL), or isotonic saline. The EHEC and S. Typhimurium concentration in all mice feces was determined. For both pathogens, the MIC and MBC values of aqueous extract were 20 y 50 mg/mL, respectively; for chloramphenicol, they were between 17.5 and 82 μg/mL. EHEC and S. Typhimurium were not detected in the feces of mice that were administered aqueous extract on the 2nd and 3rd days posttreatment. Furthermore, these mice recovered from the infection. In contrast, in mice not treated, or treated with chloramphenicol alone, pathogens were isolated from their feces throughout the study, and some mice died. The H. sabdariffa calyx extracts could be an alternative to control multidrug-resistant bacteria in humans and animals.

Comparison of the Antimicrobial Activity of Hibiscus sabdariffa Calyx Extracts, Six Commercial Types of Mouthwashes, and Chlorhexidine on Oral Pathogenic Bacteria, and the Effect of Hibiscus sabdariffa Extracts and Chlorhexidine on Permeability of the Bacterial Membrane

To determine and compare the antimicrobial effect of Hibiscus sabdariffa calyx extracts, six types of commercial mouthwashes, and chlorhexidine on Streptococcus mutans, Streptococcus sanguinis, Capnocytophaga gingivalis, and Staphylococcus aureus. Two varieties of H. sabdariffa cultivated in Mexico were used. Aqueous, methanolic, ethanolic, acetonic, and ethyl acetate extracts were obtained from H. sabdariffa calyces. Six different types of mouthwash (Astringosol^®, Colgate plax-ice-infinity^®, Crest pro-health^®, Dental max^®, Equate^®, and Listerine zero^®) and chlorhexidine (0.12%) were purchased at a pharmacy. The antimicrobial activity of the H. sabdariffa calyx extracts, mouthwashes, and chlorhexidine was determined by the agar disc diffusion technique. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of all solutions were determined by the broth dilution method and the pour plate technique, respectively. Also, the effect of H. sabdariffa extracts and chlorhexidine on permeability of the bacterial membrane was determined by the violet crystal assay. All H. sabdariffa calyx extracts and chlorhexidine showed antibacterial activity against all oral pathogenic bacteria. The mouthwashes showed lower antibacterial effect than H. sabdariffa extracts and chlorhexidine. Dental max showed no antibacterial effect. The MICs and MBCs, respectively, for H. sabdariffa extracts were between 5-20 and 10-20 mg/mL; and for chlorhexidine, between 3-4 and 3-5 mg/mL. For the Listerine^®, the MIC and MBC values were between 20-25 and 25-33 mg/mL, respectively. The results of the crystal violet test indicate that H. sabdariffa calyx extracts and chlorhexidine alter the permeability of the bacterial membrane. All H. sabdariffa extracts and chlorhexidine showed significantly greater antimicrobial effect than mouthwashes. This is the first report in which the antimicrobial effect of the H. sabdariffa calyx extracts, mouthwashes, and chlorhexidine is compared.

Comparative Effects of Carum copticum Essential Oil on Bacterial Growth and Shiga-Toxin Gene Expression of Escherichia coli O157:H7 at Abused Refrigerated Temperatures

Abused refrigerated temperatures are described as unacceptable deviations from the optimal temperature, occurring frequently during transportation of food products. Escherichia coli O157:H7 is a serious contaminant of meats and meat products due to its ability to grow at abused temperatures (> 10 °C). The aim of this study was to evaluate the antibacterial activity of Carum copticum essential oil for the control of Escherichia coli O157:H7 using laboratory media and minced beef at severe abused refrigerated temperature (15 °C). A comparative quantitative reverse transcription real-time PCR was used to assess effects of temperature and Carum copticum essential oil at sub-minimum inhibitory concentrations on bacterial growth and Shiga-toxin gene (stx1A and stx2A) expression. Results indicated that Carum copticum essential oil inhibited growth of E. coli O157:H7 in tryptone soy broth (TSB) media at all sub-MIC values until Hour 48. However, bacterial population increased progressively until Hour 72 at essential oil concentration of 0.75% (ml g^-1) and reached 8.6 log CFU g^-1 in minced beef. The essential oil at concentration of 0.005% (ml g^-1) increased stx gene expression at all times, but increased stx gene expression (0.015%) at Hour 24 in TSB media. The expression rate of stx1A in minced beef decreased progressively (10.39 and 7.67 folds for 0.5 and 0.75%, respectively) and expression of stx2A was variable in minced beef during storage. In conclusion, results from this study have shown that effects of Carum copticum essential oil on growth and virulence gene expression are not necessarily correlated and temperature, essential oil concentration, investigated gene type, and bacterial growth environment (in vivo or in vitro) are effective as well.

Hibiscus Acid and Chromatographic Fractions from Hibiscus Sabdariffa Calyces: Antimicrobial Activity against Multidrug-Resistant Pathogenic Bacteria

The anti-microbial properties of acetone extracts from Hibiscus sabdariffa calyces, fractions isolated by silica gel chromatography and hibiscus acid purified from some of these fractions and additionally identified by nuclear magnetic resonance spectroscopy, mid-infrared spectroscopy and X-ray diffraction, were studied against both multidrug-resistant Salmonella strains and pathogenic Escherichia coli bacteria. Gel diffusion was used to determine the anti-microbial effects. The mode of action of hibiscus acid was determined by crystal violet assay. Hibiscus acid and 17 of the 25 chromatographic fractions obtained, displayed an anti-microbial effect against all bacterial strains tested. Hibiscus acid showed a greater anti-microbial effect than the acetone extract against most of the bacteria strains, while chromatographic fractions IX–XIV exerted the greatest anti-microbial effect against all bacteria. The minimum inhibitory concentration of the acetone extract was 7 mg/mL, and the minimum bactericidal concentration was 10 mg/mL, while the corresponding values for hibiscus acid were 4–7 and 7 mg/mL, respectively. The results of the crystal violet assay indicate that hibiscus acid alters membrane permeability. Hibiscus acid is a potential alternative to control multidrug-resistant bacteria. Due to its ready availability and easy extraction from H. sabdariffa, hibiscus acid is potentially useful in the food industries.

Enrichment of chelidonine from Chelidonium majus L. using macroporous resin and its antifungal activity

Chelidonium majus L. (greater celandine) has been used as an herbal medicine for several centuries. This study investigated an efficient method to purify chelidonine from the extract of C. majus L. using macroporous adsorption resins and evaluated the antifungal activity of chelidonine against Botryosphaeria dothidea as a model strain. Static adsorption and desorption tests revealed that D101 was the optimal resin for chelidonine purification. Pseudo-second-order kinetics model and Freundlich equation model were the most suitable for evaluating the endothermic and spontaneous adsorption processes of chelidonine on D101. Dynamic adsorption and desorption tests on D101 columns showed that the concentration of chelidonine increased 14.16-fold, from 2.67% to 37.81%, with the recovery yield of 80.77%. The antifungal activity of enriched chelidonine products was studied with B. dothidea. The results showed that the EC₅₀ of crude extracts, enriched chelidonine products, and chelidonine standard against B. dothidea were 3.24mg/mL, 0.43mg/mL, and 0.77mg/mL, respectively. The result of antifungal activity test showed that chelidonine had the potential to be a useful antifungal agent. Moreover, the enrichment method of chelidonine was highly efficient, low cost, and harmless to the environment for industrial applications.

Attachment of 13 Types of Foodborne Bacteria to Jalapeño and Serrano Peppers and Antibacterial Effect of Roselle Calyx Extracts, Sodium Hypochlorite, Colloidal Silver, and Acetic Acid against These Foodborne Bacteria on Peppers

Chili peppers are a very important crop in Mexico. However, these peppers have been associated with Salmonella infection outbreaks in the United States, and Salmonella and diarrheagenic Escherichia coli pathotypes have been isolated from jalapeño and serrano peppers in Mexico. To decrease microbial contamination of fruits and vegetables, chemical agents are commonly used; however, chemical agents used to eliminate pathogenic bacteria on vegetables have a limited antimicrobial effect. Roselle ( Hibiscus sabdariffa ) calyces have been reported to have an antimicrobial effect on pathogenic bacteria. In the present study, the antibacterial effect of four roselle calyx extracts (water, methanol, acetone, and ethyl acetate), sodium hypochlorite, colloidal silver, and acetic acid against foodborne bacteria was evaluated on contaminated jalapeño and serrano peppers. The 13 types of foodborne bacteria evaluated were Listeria monocytogenes , Shigella flexneri , Salmonella Typhimurium, Salmonella Typhi, Salmonella Montevideo, Staphylococcus aureus , E. coli O157:H7, five E. coli pathotypes (Shiga toxin producing, enteropathogenic, enterotoxigenic, enteroinvasive, and enteroaggregative), and Vibrio cholerae O1. All 13 types attached to both pepper types, with no significant differences in attachment between jalapeño and serrano peppers. Roselle calyx extract treatment resulted in a greater reduction in levels of all foodborne bacteria than did treatment with sodium hypochlorite, colloidal silver, and acetic acid on both pepper types. Roselle calyx extracts may be a useful for disinfection of chili peppers in the field, processing plants, restaurants, and homes.