Potential Effects of Romanian Propolis Extracts against Pathogen Strains

In Vitro Antimicrobial Potential of Portuguese Propolis Extracts from Gerês against Pathogenic Microorganisms

Antimicrobial resistance (AMR) is one of humanity's main health problems today. Despite all the breakthroughs and research over the past few years, the number of microbial illnesses that are resistant to the available antibiotics is increasing at an alarming rate. In this article, we estimated the biomedical potential of Portuguese propolis harvested from the Gerês apiary over five years, evaluating the in vitro antimicrobial effect of five hydroalcoholic extracts prepared from five single propolis samples and of a hydroalcoholic extract obtained from the mixture of all samples. The antimicrobial potential was firstly assessed by determining the minimum inhibitory concentration (MIC) of these extracts against a panel of three Gram-positive (Bacillus subtilis, methicillin-sensitive Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus) and one Gram-negative bacteria (Escherichia coli), as well as two yeasts (Candida albicans and Saccharomyces cerevisiae). As MIC values against each bacterium were consistent across all the evaluated propolis extracts, we decided to further conduct a disk diffusion assay, which included three commercial antibiotics-erythromycin, vancomycin, and amoxicillin/clavulanic acid-for comparison purposes. In addition to displaying a concentration-dependent antibacterial effect, the hydroalcoholic extracts prepared with 70% ethanol exhibited stronger antimicrobial capacity than vancomycin against B. subtilis (% of increase ranged between 26 and 59%) and methicillin-sensitive S. aureus (% of increase ranged between 63 and 77%). Moreover, methicillin-resistant S. aureus (MRSA) showed susceptibility to the activity of the same extracts and resistance to all tested antibiotics. These findings support that propolis from Gerês is a promising natural product with promising antimicrobial activity, representing a very stimulating result considering the actual problem with AMR.

Phenolic Composition, Antiradical, Antimicrobial, and Anti-Inflammatory Activities of Propolis Extracts from North East Spain

Antioxidant-related parameters and anti-inflammatory and antimicrobial activities against Listeria monocytogenes were assessed in eight North East Spain poplar propolis samples. Propolis extracts (PEs) were obtained using 70% ethanol (PEE) and methanol (PME). Yield and total phenol compounds were higher in PEE. Phenolic acids were analyzed by a high-performance liquid chromatograph-diode array detector. Caffeic and ferulic acids were quantified in all PEE and PME. All samples contained p-coumaric acid (quantified in 6 PEE and in 3 PME). Ascorbic acid was detected in all propolis, but mainly quantified in PME (≤0.37 mg/g PE). Biological properties were tested on PEE. As for antiradical activities, trolox equivalent antioxidant capacity (TEAC) [against 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)•+], ranged between 578 and 4620 µmol trolox/g, 2,2-diphenyl-1-picrylhydrazyl (DPPH) (against DPPH free radical), between 0.049 and 0.094 mg/mL, antioxidant activity against hydroxyl (•OH) radical (AOA), between 0.04 and 11.01 mmol uric acid/g, and oxygen radical absorbance capacity (ORAC) against peroxyl (ROO•) radical between 122 and 3282 µmol trolox/g. Results of TEAC, AOA, and ORAC were significantly correlated. IC50 anti-inflammatory activity ranged from 1.08 to 6.19 mg/mL. Propolis showed higher inhibitory activity against L. monocytogenes CECT934 and L. monocytogenes CP101 by agar well diffusion (P < .05) (10.5 and 10.2 mm, respectively) than against L. monocytogenes CP102 (7.0 mm). Data of this research show that North East Spain propolis may be of interest for pharmaceutical and food industry use.

Biochemical Profile and Antioxidant Properties of Propolis from Northern Spain

The antioxidant, anti-inflammatory, and antimicrobial characteristics of propolis, a bioactive compound collected from hives, have prompted its use in the food sector in recent times. This study investigated the physicochemical characteristics, phenolic profile, and antioxidant capacity of 31 propolis extracts collected from Northern Spain. The physicochemical composition (resins, waxes, ashes mineral content, and heavy metals) was within the allowable regulatory limits. The analysis of bioactive compounds enabled the identification of 51 constituents: flavonoids (apigenin, catechin, chrysin, quercetin, and pinocembrin) and phenolic acids (caffeic, ferulic, and coumaric). The mean value of total polyphenols was 42.72 ± 13.19 Pinocembrin-Galangin Equivalents/100 g, whereas a range between 1.64 ± 0.04 and 4.95 ± 0.36 Quercetin Equivalents (QE) g/100 g was found for total flavonoids content. The determination of bioactivities revealed significant antioxidant capacity using DPPH (1114.28 ± 10.39 µM Trolox Equivalents and 3487.61 ± 318.66 µM Vitamin C Equivalents). Resin content in propolis samples was positively and significantly correlated with both polyphenols (rho = 0.365; p = 0.043) and flavonoid composition (rho = 0.615; p = 0.000) as well as the antioxidant capacity TEAC DPPH (rho = 0.415; p = 0.020). A multiple regression analysis modeled the correlation between resin composition, flavonoids, and TEAC DPPH values, yielding a significant regression equation (R2 = 0.618; F (2,28) = 22.629; p < 0.000; d = 2.299). Therefore, evaluating physicochemical parameters and biological activities provides a promising framework for predicting propolis' quality and antioxidant properties, thus suggesting its potential as a functional and bioactive compound for the food industry.

Phyto-Inhibitory and Antimicrobial Activity of Brown Propolis from Romania

The objective of this paper was to study the phyto-inhibitory and antimicrobial activity of brown propolis collected from the counties of four regions in Romania. The main physico-chemical and functional properties of 16 samples of propolis from different landforms of geographical regions were determined. Their antimicrobial activities were established against 5 bacterial strains (Pseudomonas fluorescens, Bacillus subtilis, Bacillus cereus, Escherichia coli, and Proteus mirabilis) and 5 fungal strains (Alternaria alternata, Cladosporium cladosporioides, Fusarium oxysporum, Mucor racemosus, and Aspergillus niger). Simultaneously, the phyto-inhibitory effect of propolis samples on different cereals was highlighted: hexaploid bread wheat (Triticum aestivum), maize (Zea mays L.), oats (Avena sativa L.), and barley (Hordeum vulgare L.). Correlations between the antioxidant activity and total flavonoid and phenol content of the propolis samples were identified, respectively, and the statistical analysis highlighted that the diameter of the inhibition zone was influenced by the strain type (bacterial and fungal) and the geographical regions of propolis. Principal component analysis (PCA) indicated that out of seven principal components, only two exhibited > 0.5. Pearson's correlation coefficient showed a low and moderate positive linear relationship between the diameter of the inhibition zone and the flavonoid and phenol concentration of the propolis samples.

Antimicrobial Activity of Spanish Propolis against Listeria monocytogenes and Other Listeria Strains

The outbreaks of Listeria associated with food consumption are increasing worldwide concurrently with public concern about the need for natural growth inhibitors. In this context, propolis seems to be a promising bioactive product collected by honeybees, due to its antimicrobial activity against different food pathogens. This study aims to evaluate the efficacy of hydroalcoholic propolis extracts for controlling Listeria under several pH conditions. The physicochemical properties (wax, resins, ashes, impurities), the bioactive compounds (phenolic and flavonoid content), and the antimicrobial activity of 31 propolis samples collected from the half North of Spain were determined. Results showed similar trends in the physicochemical composition and bioactive properties, regardless of the harvesting area. Non-limiting pH conditions (7.04, 6.01, 5.01) in 11 Listeria strains (5 from collection and 6 wild strains from meat products) exhibited MICs (Minimum inhibition concentration) and MBCs (Minimum bactericidal concentration) ranging from 39.09 to 625 μg/mL. The antibacterial activity increased under acidic pH conditions, showing a synergistic effect at pH = 5.01 (p < 0.05). These findings suggest the potential of Spanish propolis as a natural antibacterial inhibitor to control Listeria growth in food products.

Inhibitory Mechanism of Flavonoids from Sedum aizoon L. on Rhizopus nigricans

Rhizopus nigricans is a widespread phytopathogen in fruits and vegetables that can cause considerable economic effects and resource waste. Flavonoids from Sedum aizoon L. (FSAL) have specific antifungal activities. This study selected FSAL as an antifungal to prolong the preservation of fruits and vegetables. The results showed that the mycelial morphology and ultrastructure were damaged by the FSAL treatment (1.0 minimum inhibitory concentration), led to the increase of reactive oxygen species and malondialdehyde, and affected the activity of key enzymes in the glycolytic pathway, such as lactic dehydrogenase, pyruvate kinase, and hexokinase of R. nigricans. Key genes in glycolysis were upregulated or downregulated. In addition, in the treatment and control groups, 221 differentially expressed genes were found, including 89 that were upregulated and 32 that were downregulated, according to the transcriptome results. The differential genes were mainly enriched in glycolysis, pyruvate metabolism, and citrate cycle pathways. The results revealed some insights into the antifungal mechanism of FSAL against R. nigricans and offered a theoretical foundation for its advancement as a novel plant-derived antifungal agent.

Qualitative Characterization and Antifungal Activity of Romanian Honey and Propolis

The purpose of this study was to review the physicochemical characterization of Romanian honey and propolis and their antifungal effect on different strains. As an indicator of environmental pollution, lead exceeded the allowed limits in two study areas. The relationship between the acidity and electrical conductivity of polyfloral honey and the antioxidant activity with the total content of phenolics and flavonoids was investigated. The antifungal activity of 13 polyfloral honey and propolis samples from North-West and Central Romania and 12 samples from Alba County was investigated against six fungal strains: Aspergillus niger, Aspergillus flavus, Candida albicans, Penicillium chrysogenum, Rhizopus stolonifer, Fusarium oxysporum. All honey and propolis samples exhibited an antifungal effect. The most sensitive strains were P. chrysogenum and R. stolonifer for honey and P. chrysogenum and F. oxisporumn for propolis. A two-way analysis of variance was used to evaluate the correlations between the diameter of the inhibition zones for the strains and the propolis extracts. Statistical analysis demonstrated that the diameter of the inhibition zone was influenced by the strain type and the geographical origin of honey and propolis. Pearson's correlation coefficient shows a significant positive linear relationship between the diameter of the inhibition zone and the flavonoid and phenol concentration of honey and propolis, respectively.

Prospects of ultrasonically extracted food bioactives in the field of non-invasive biomedical applications - A review

Foods incorporated with bioactive compounds, called nutraceuticals, can fight or prevent or alleviate diseases. The contribution of nutraceuticals or phytochemicals to non-invasive biomedical applications is increasing. Although there are many traditional methods for extracting bioactive compounds or secondary metabolites, these processes come with many disadvantages like lower yield, longer process time, high energy consumption, more usage of solvent, yielding low active principles with low efficacy against diseases, poor quality, poor mass transfer, higher extraction temperature, etc. However, nullifying all these disadvantages of a non-thermal technology, ultrasound has played a significant role in delivering them with higher yield and improved bio-efficacy. The physical and chemical effects of acoustic cavitation are the crux of the output. This review paper primarily discusses the ultrasound-assisted extraction (USAE) of bioactives in providing non-invasive prevention and cure to diseases and bodily dysfunctions in human and animal models. The outputs of non-invasive bioactive components in terms of yield and the clinical efficacy in either in vitro or in vitro conditions are discussed in detail. The non-invasive biomedical applications of USAE bioactives providing anticancer, antioxidant, cardiovascular health, antidiabetic, and antimicrobial benefits are analyzed in-depth and appraised. This review additionally highlights the improved performance of USAE compounds against conventionally extracted compounds. In addition, an exhaustive analysis is performed on the role and application of the food bioactives in vivo and in vitro systems, mainly for promoting these efficient USAE bioactives in non-invasive biomedical applications. Also, the review explores the recovery of bioactives from the less explored food sources like cactus pear fruit, ash gourd, sweet granadilla, basil, kokum, baobab, and the food processing industrial wastes like peel, pomace, propolis, wine residues, bran, etc., which is rare in literature.