Italian acacia honey exhibits lytic effects against the crayfish pathogens Aphanomyces astaci and Fusarium avenaceum

The in vitro and in vivo antibacterial activities of uniflorous honey from a medicinal plant, Scrophularia ningpoensis Hemsl., and characterization of its chemical profile with UPLC-MS/MS

ETHNOPHARMACOLOGICAL RELEVANCE

According to the Compendium of Materia Medica, honey has been used as a traditional medicine in treatment against mucositis, tinea, hemorrhoids and psoriasis. In complementary medicine, due to its significant antimicrobial activity, honey has been widely used as a remedy for skin wounds and gastrohelcosis for thousands of years.

AIM OF THE STUDY

This study is aimed at exploring the antimicrobial activity and mechanisms of honey sourced from medicinal plants, and revealing the composition-activity relationship, to facilitate their complementary and alternative application in the therapy of bacterial infectious diseases.

MATERIALS AND METHODS

Eight kinds of medicinal plant-derived uniflorous honey, native to China, were gathered. Their antimicrobial activities were evaluated in vitro, and then in vivo with the systemically infected mouse model and the acute skin infection model. SYTOX uptake assay, scanning electron microscopy, DNA binding assay, and quantitative real-time PCR, were carried out to elucidate the antibacterial mechanisms. This was followed by an investigation of the componential profile with the UPLC-MS/MS technique.

RESULTS

It was found that Scrophularia ningpoensis Hemsl. (figwort) honey (S. ningpoensis honey) exhibited broad-spectrum and the strongest antibacterial potency (MICs of 7.81-125.00%, w/v), comparable to manuka honey. In the in vivo assays, S. ningpoensis honey significantly decreased the bacterial load of the muscles under the acute MRSA-infected skin wounds; the sera level of TNF-α in the S. aureus and P. aeruginosa-infected mice decreased by 45.38% and 51.75%, respectively, after the treatment of S. ningpoensis honey (125 mg/10 g). It was capable of killing bacteria through disrupting the cell membranes and the genomic DNA, as well as down-regulating the expression of genes associated with virulence, biofilm formation and invasion, including icaA, icaD, eno, sarA, agrA, sigB, fib and ebps in S. aureus, and lasI, lasR, rhlI, rhlR and algC in P. aeruginosa. Apart from H₂O₂, some other nonperoxide compounds such as adenosine, chavicol, 4-methylcatechol, trehalose, palmitoleic acid and salidroside, might play a vital role in the antibacterial properties of S. ningpoensis honey.

CONCLUSIONS

This is the first study to thoroughly investigate the antibacterial activity, mode of action, and componential profile of S. ningpoensis honey. It suggested that S. ningpoensis honey might be a potential supplement or substitute for manuka honey, for the prevention or treatment of bacterial infections. It will facilitate the precise application of medicinal plant-sourced honey, provide a new thread for the development of antibacterial drugs, and assist in the distinction of different kinds of honey.

Antifungal Activity of Honey Samples from Khyber Pakhtunkhwa (Pakistan) as affected by Botanical Origin

The present study evaluated the antifungal activity of honey samples collected from different locations at Khyber Pakhtunkhwa (KPK, Pakistan). Disc diffusion method was used to test the antifungal potential of twenty-one (branded, unbranded, and natural comb) honey samples from the different botanical origins at different concentrations (undiluted, 10%, 30%, and 50%, w/v) against Candida albicans and Rhodotorula species. Branded, unbranded, and natural comb honey samples generate different inhibition zones (4-13 mm, 5-15 mm, and 8-17 mm) against Rhodotorula species. Candida albicans showed resistance for all tested honey samples. Minimum inhibitory concentration (MIC) against Candida albicans and Rhodotorula species were 53.33%-88.12% and 1.76%-90.22% for branded, 61.3% – 93.8% and 9.90% – 95.5% for unbranded, and 67.1%-96.8% and 6.39%-98.8% for natural comb honey. In conclusion, natural comb honey from Khyber Pakhtunkhwa may have antifungal therapeutic potential and could be a useful source for generating functional food.

In silico analysis of the antimicrobial activity of phytochemicals: towards a technological breakthrough

BACKGROUND

The complications associated with infections from pathogens increasingly resistant to traditional drugs lead to a constant increase in the mortality rate among those affected. In such cases the fundamental purpose of the microbiology laboratory is to determine the sensitivity profile of pathogens to antimicrobial agents. This is an intense and complex work often not facilitated by the test's characteristics. Despite the evolution of the Antimicrobial Susceptibility Testing (AST) technologies, the technological breakthrough that could guide and facilitate the search for new antimicrobial agents is still missing.

METHODS

In this work, we propose the experimental use of in silico instruments, particularly feedforward Multi-Layer Perceptron (MLP) Artificial Neural Network, and Genetic Programming (GP), to verify, but also to predict, the effectiveness of natural and experimental mixtures of polyphenols against several microbial strains.

RESULTS

We value the results in predicting the antimicrobial sensitivity profile from the mixture data. Trained MLP shows very high correlations coefficients (0,93 and 0,97) and mean absolute errors (110,70 and 56,60) in determining the Minimum Inhibitory Concentration and Minimum Microbicidal Concentration, respectively, while GP not only evidences very high correlation coefficients (0,89 and 0,96) and low mean absolute errors (6,99 and 5,60) in the same tasks, but also gives an explicit representation of the acquired knowledge about the polyphenol mixtures.

CONCLUSIONS

In silico tools can help to predict phytobiotics antimicrobial efficacy, providing an useful strategy to innovate and speed up the extant classic microbiological techniques.

In vitro Synergy of Polyphenolic Extracts From Honey, Myrtle and Pomegranate Against Oral Pathogens, S. mutans and R. dentocariosa

The increasing incidence rate of oral diseases, the wide spread of antimicrobial resistance, and the adverse effects of conventional antibiotics mean alternative prevention and treatment options are needed to counteract oral pathogens. In this regard, our study aims to evaluate the antibacterial activity of polyphenolic extracts prepared from acacia honey, myrtle leaves, and pomegranate peel against cariogenic bacteria, such as Streptococcus mutans and Rothia dentocariosa. The chemical-physical parameters of acacia honey and the RP-HPLC polyphenolic profile of pomegranate peel extract have been previously described in our studies, while the characterization of myrtle extract, performed by HPLC analysis, is reported here. All the extracts were used singly and in binary combinations to highlight any synergistic effects. Moreover, the extracts were tested in association with amoxicillin to evaluate their ability to reduce the effective dose of this drug in vitro. The values of minimal inhibitory concentrations and minimal bactericidal concentrations have been used to quantitatively measure the antibacterial activity of the single extracts, while the fractional inhibitory concentration index has been considered as predictor of in vitro anticariogenic synergistic effects. Finally, a time-kill curve method allowed for the evaluation of the bactericidal efficacy of the combined extracts. The microbiological tests suggest that acacia honey, myrtle, and pomegranate extracts are able to inhibit the cariogenic bacteria, also with synergistic effects. This study provides useful and encouraging results for the use of natural extract combinations alone or in association with antibiotics (adjuvant therapy) as a valid alternative for the prevention and treatment of oral infectious diseases.

Chestnut Shell Extract Modulates Immune Parameters in the Rainbow Trout Oncorhynchus mykiss

In this study, chestnut (Castanea sativa) shell was extracted with different solvents, and immunomodulatory activity was investigated in an in vitro model system using blood and intestinal leukocytes of Oncorhynchus mykiss. Gallic acid (GA) was used as a standard. Chestnut shell extract (CSE) and GA readily entered both blood and intestinal leukocytes. Superoxide anion production and phagocytosis were decreased by low doses of CSE and increased with high doses. CSE and GA differently regulated cytokine expression in blood and intestinal leukocytes. High doses of CSE upregulated IL-1β, TNF-α, and IL-10 in intestinal leukocytes and IL-10 in blood leukocytes. Low doses of CSE upregulated IL-1β and TNF-α in blood leukocytes. GA appeared to be effective only in blood leukocytes. The effects of CSE on pro- and anti-inflammatory cytokines seemed to suggest an alert effect of the immune defense system against a possible infectious agent. The less evident effect of GA in comparison to CSE could have been attributable to the synergistic and/or additive effects of polyphenols in the latter. The immune-stimulating activity of CSE reported here could be useful for future practical applications in fish health.