In vitro activity of plant extracts against biofilm-producing food-related bacteria

Synergistic antimicrobial action of chitosan-neem extracts nanoformulation as a promising strategy for overcoming multi-drug resistant bacteria

The objective of the present study was to analyze and identify the phytochemical components found in neem leaf extracts using gas chromatography-mass spectrometry (GC-MS) and Fourier-transform infrared spectroscopy (FTIR) methods. The extract samples were acquired using ethyl acetate (EA) and petroleum ether (PE) solvents. Moreover, the extracts were assessed for their antibacterial and antioxidant features. In addition, chitosan nanoparticles (Cs NPs) containing neem extracts were synthesized and evaluated for their potential antibacterial properties, explicitly targeting multi-drug resistant (MDR) bacteria. The neem extracts were analyzed using GC-MS, which identified components such as hydrocarbons, phenolic compounds, terpenoids, alkaloids, and glycosides. Results revealed that the PE extract showed significant antibacterial activity against a range of bacteria. In addition, the PE extract exhibited significant antioxidant activity, exceeding both the EA extract and vitamin C. In addition, both extracts exhibited notable antibiofilm activity, significantly inhibiting the production of biofilm. The Cs NPs, loaded with neem extracts, exhibited significant antibacterial action against multidrug-resistant (MDR) microorganisms. The Cs NPs/EA materials had the greatest zone of inhibition values of 24 ± 2.95 mm against Pseudomonas aeruginosa. Similarly, the Cs NPs/PE materials exhibited a zone of inhibition measurement of 22 ± 3.14 mm against P. aeruginosa. This work highlights the various biochemical components of neem extracts, their strong abilities to combat bacteria and oxidative stress, and the possibility of Cs NPs containing neem extracts as effective treatments for antibiotic-resistant bacterial strains.

Endophytic Streptomyces sp. MSARE05 isolated from roots of Peanut plant produces a novel antimicrobial compound

AIM

This study aimed to isolate, endophytic Streptomyces sp. MSARE05 isolated from root of a peanut (Arachis hypogaea) inhibits the growth of other bacteria. The research focused on characterizing the strain and the antimicrobial compound.

METHODS AND RESULTS

The surface-sterilized peanut roots were used to isolate the endophytic bacterium Streptomyces sp. MSARE05. A small-scale fermentation was done to get the antimicrobial compound SM05 produced in highest amount in ISP-2 medium (pH 7) for 7 days at 30°C in shaking (180 rpm) condition. Extraction, purification, and chemical analysis of the antibacterial component revealed a novel class of antibiotics with a 485.54 Dalton molecular weight. The MIC was 0.4-0.8 µg ml-1 against the tested pathogens. It also inhibits multidrug-resistant (MDR) pathogens and Mycobacterium with 0.8-3.2 µg ml-1 MIC. SM05 was found to disrupt cell membrane of target pathogen as evident by significant leakage of intracellular proteins and nucleic acids. It showed synergistic activity with ampicillin, chloramphenicol, streptomycin, and kanamycin.

CONCLUSIONS

The new-class antimicrobial SM05 consisting naphthalene core moiety was effective against drug-resistant pathogens but non-cytotoxic to human cells. This study underscores the significance of endophytic Streptomyces as a source of innovative antibiotics, contributing to the ongoing efforts to combat antibiotic resistance.

Natural phenolic compounds as biofilm inhibitors of multidrug-resistant Escherichia coli - the role of similar biological processes despite structural diversity

Multidrug-resistant gram-negative pathogens such as Escherichia coli have become increasingly difficult to treat and therefore alternative treatment options are needed. Targeting virulence factors like biofilm formation could be one such option. Inhibition of biofilm-related structures like curli and cellulose formation in E. coli has been shown for different phenolic natural compounds like epigallocatechin gallate. This study demonstrates this effect for other structurally unrelated phenolics, namely octyl gallate, scutellarein and wedelolactone. To verify whether these structurally different compounds influence identical pathways of biofilm formation in E. coli a broad comparative RNA-sequencing approach was chosen with additional RT-qPCR to gain initial insights into the pathways affected at the transcriptomic level. Bioinformatical analysis of the RNA-Seq data was performed using DESeq2, BioCyc and KEGG Mapper. The comparative bioinformatics analysis on the pathways revealed that, irrespective of their structure, all compounds mainly influenced similar biological processes. These pathways included bacterial motility, chemotaxis, biofilm formation as well as metabolic processes like arginine biosynthesis and tricarboxylic acid cycle. Overall, this work provides the first insights into the potential mechanisms of action of novel phenolic biofilm inhibitors and highlights the complex regulatory processes of biofilm formation in E. coli.

Hexanic extract of Achyrocline satureioides: antimicrobial activity and in vitro inhibitory effect on mechanisms related to the pathogenicity of Paenibacillus larvae

INTRODUCTION

Paenibacillus larvae is a spore-forming bacillus, the most important bacterial pathogen of honeybee larvae and the causative agent of American foulbrood (AFB). Control measures are limited and represent a challenge for both beekeepers and researchers. For this reason, many studies focus on the search for alternative treatments based on natural products.

AIM

The objective of this study was to determine the antimicrobial activity of the hexanic extract (HE) of Achyrocline satureioides on P. larvae and the inhibitory activity on some mechanisms related to pathogenicity.

MATERIAL AND METHODS

The Minimum Inhibitory Concentration (MIC) of the HE was determined by the broth microdilution technique and the Minimum Bactericidal Concentration (MBC) by the microdrop technique. Swimming and swarming motility was evaluated in plates with 0.3 and 0.5% agar, respectively. Biofilm formation was evaluated and quantified by the Congo red and crystal violet method. The protease activity was evaluated by the qualitative technique on skim milk agar plates.

RESULTS

It was determined that the MIC of the HE on four strains of P. larvae ranged between 0.3 and 9.37 µg/ml and the MBC between 1.17 and 150 µg/ml. On the other hand, sub-inhibitory concentrations of the HE were able to decrease swimming motility, biofilm formation and the proteases production of P. larvae.

Compost and Phosphorus/Potassium-Solubilizing Fungus Effectively Boosted Quinoa's Physio-Biochemical Traits, Nutrient Acquisition, Soil Microbial Community, and Yield and Quality in Normal and Calcareous Soils

Calcareous soil had sufficient phosphorus and potassium (PK) in different forms due to the high contents of PK-bearing minerals; however, the available PK state was reduced due to its PK-fixation capacity. Compost, coupled with high PK solubilization capacity microbes, is a sustainable solution for bioorganic fertilization of plants grown in calcareous soil. A 2-year field experiment was conducted to investigate the effect of compost (20 t ha-1) with Aspergillus niger through soil drenching (C-AN) along with partial substitution of PK fertilization on quinoa performance in normal and calcareous soils. Treatments included PK100% (72 kg P2O5 ha-1 + 60 kg K2O ha-1 as conventional rate), PK100%+C-AN, PK75%+C-AN, PK50%+C-AN, PK25%+C-AN, and only C-AN in normal and calcareous soils. Results showed that C-AN and reduced PK fertilization (up to 75 or 50%) increased photosynthetic pigments and promoted nutrient acquisition in quinoa grown in calcareous soil. Reduced PK fertilization to 75 or 50% plus C-AN in calcareous soil increased osmoprotectants, nonenzymatic antioxidants, and DPPH scavenging activity of quinoa's leaves compared to the PK0%+C-AN treatment. The integrative application of high PK levels and C-AN enhanced the quinoa's seed nutritional quality (i.e., lipids, carbohydrates, mineral contents, total phenolics, total flavonoids, half maximal inhibitory concentration, and antiradical power) in calcareous soil. At reduced PK fertilization (up to 75 or 50%), application of compost with Aspergillus niger through soil drenching increased plant dry weight by 38.7 or 53.2%, hectoliter weight by 3.0 or 2.4%, seed yield by 49.1 or 39.5%, and biological yield by 43.4 or 33.6%, respectively, compared to PK0%+C-AN in calcareous soil. The highest P-solubilizing microorganism's population was found at PK0%+C-AN in calcareous soil, while the highest Azotobacter sp. population was observed under high PK levels + C-AN in normal soil. Our study recommends that compost with Aspergillus niger as a bioorganic fertilization treatment can partially substitute PK fertilization and boost quinoa's tolerance to salt calcareous-affected soil.

Antimicrobial Susceptibility of Staphylococcus aureus Strains and Effect of Phloretin on Biofilm Formation

Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) are known to be responsible of various infections, including biofilm-associated diseases. The aim of this study was to analyze 19 strains of S. aureus from orthopedic sites in terms of phenotypic antimicrobial susceptibility against 13 selected antibiotics, slime/biofilm formation, molecular analysis of specific antibiotic resistance genes (mecA, cfr, rpoB), and biofilm-associated genes (icaADBC operon). Furthermore, the effect of phloretin on the production of biofilm was evaluated on 8 chosen isolates. The susceptibility test confirmed almost all strains were resistant to cefoxitin and oxacillin. Most strains possess the mecA, whereas none of the strains had the cfr gene. Four strains (1, 7, 10, and 24) presented single-nucleotide polymorphisms (SNPs) in rpoB, which confer rifampicin resistance. IcaD was detected in all tested strains, whereas icaR was only found in two strains (24 and 30). Phloretin had a dose-dependent effect on biofilm production. Specifically, 0.5 × MIC determined biofilm inhibition in 5 out of 8 strains (8, 24, 25, 27, 30), whereas an increase in biofilm production was detected with phloretin at the 0.125 × MIC across all tested strains. These data are useful to potentially develop novel compounds against antibiotic-resistant S. aureus.

Induction role of chitosan nanoparticles to Anethum graveolens extract against food-borne bacteria, oxidant, and diabetic activities in vitro

Foodborne diseases as well as Foodborne pathogens are a global issue with significant effects on human health and economy. Therefore, several investigators have tried to find new alternative approaches to prevent and control this problem. In this context, the present study aimed to find some possible and effective approaches for controlling food-borne bacteria via Dill (Anethum graveolens L.) extract (DE) loaded with chitosan nanoparticles (ChNPs) besides its anti-oxidant and anti-diabetic activities. Flavonoid and phenolic contents of DE were detected by HPLC, indicating the presence of 18 constituents, high content (22526.51 μg/mL) of chlorogenic acid, followed by 2236.21 μg/mL of coumaric acid and 2113.81 μg/mL of pyrocatechol. In contrast, low contents of cinnamic acid, methyl gallate, apigenin, daidzein, quercetin, syringic acid, and kaempferol were detected. B. cereus, Staphylococcus aureus, E. coli, S. typhi, E. faecalis, and C. albicans were highly inhibited by DE loaded ChNPs (DELChNPs) with inhibition zones (IZs) of 28.50 ± 0.87, 30.33 ± 0.58, 29.33 ± 0.58, 23.17 ± 0.76, 25.76 ± 0.58, and 24.17 ± 0.29 mm with MIC 15.41 ± 0.36, 7.70 ± 0.17, 15.58 ± 0.07, 31.08 ± 0.07, 31.04 ± 0.07 and 62.33 ± 0.29 μg/mL compared with inhibitory activity caused by DE, where the IZs were 25.83 ± 1.44, 29.67 ± 0.85, 24.83 ± 0.76, 20.33 ± 1.53, 21.17 ± 0.29, and 19.67 ± 1.15 mm with MIC 62.33 ± 0.29, 31.08 ± 0.07, 62.50 ± 0.29, 31.08 ± 0.07, 31.04 ± 0.07, and 249.0 ± 1.73 μg/mL, respectively. Also, the minimum bactericidal concentration (MBC) of DELChNPs was less than DE against all tested microorganisms. The MBC/MIC index documented that DELChNPs were more effective than DE. The biofilm of tested bacteria was inhibited by DE and DELChNPs but with different levels of anti-biofilm activity. For example, the anti-biofilm activity was 79.26 and 86.15% against B. cereus using DE and DELChNPs, respectively. DELChNPs and DE, compared with the ascorbic acid, exhibited DPPH scavenging % with IC⁵⁰ values of 7.8 μg/mL, 13.96 μg/mL, and 4.83 μg/mL, respectively. Anti-diabetic activity in vitro via inhibition of amylase indicated that IC⁵⁰ was 164.2 μg/mL and 164.3 μg/mL using DE and DELChNPs, respectively. This investigation highlights the vital DE phytoconstituents, particularly DELChNPs which possess important therapeutic effects against food-borne microorganisms and could be utilized as a safe alternative to synthetic drugs.

Elaboration and Characterization of Pereskia aculeate Miller Extracts Obtained from Multiple Ultrasound-Assisted Extraction Conditions

Pereskia aculeata Miller, is an unconventional food plant native to South America. This study aimed to investigate the influence of different ultrasonic extraction times (10, 20, 30, and 40 min) on the phytochemical profile, antioxidant and antibacterial activities of ethanolic extracts obtained from lyophilized Pereskia aculeate Miller (ora-pro-nobis) leaves, an under-researched plant. Morphological structure and chemical group evaluations were also conducted for the lyophilized P. aculeate leaves. The different extraction times resulted in distinct phenolic content and Antioxidant Activity (ATT) values. Different extraction time conditions resulted in phenolic compound contents ranging from 2.07 to 2.60 mg EAG.g^-1 of extract and different ATT values. The ATT evaluated by DPPH was significantly higher (from 61.20 to 70.20 μM of TE.g^-1 of extract) in extraction times of 30 and 40 min, respectively. For ABTS, it varied between 6.38 and 10.24 μM of TE.g^-1 of extract and 24.34 and 32.12 μM ferrous sulp.g^-1 of extract. All of the obtained extracts inhibited the growth of Staphylococcus aureus, particularly the treatment employing 20 min of extraction at the highest dilution (1.56 mg.mL^-1). Although liquid chromatography analyses showed that chlorogenic acid was the primary compound detected for all extracts, Paper Spray Mass Spectrometry (PS-MS) suggested the extracts contained 53 substances, such as organic, fatty, and phenolic acids, sugars, flavonoids, terpenes, phytosterols, and other components. The PS-MS proved to be a valuable technique to obtain the P. aculeate leaves extract chemical profile. It was observed that the freeze-drying process enhanced the conservation of morphological structures of P. aculeate leaves, as evidenced by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) identified carboxyl functional groups and proteins between the 1000 and 1500 cm^-1 bands in the P. aculeate leaves, thus favoring water interaction and contributing to gel formation. To the best of our knowledge, this is the first study to evaluate different times (10, 20, 30 and 40 min) for ultrasound extraction of P. aculeate leaves. The polyphenols improved extraction, and high antioxidant activity demonstrates the potential for applying P. aculeate leaves and their extract as functional ingredients or additives in the food and pharmaceutical industries.

Valorization of Juglans regia Leaves as Cosmeceutical Ingredients: Bioactivity Evaluation and Final Formulation Development

The cosmetic industry is constantly searching for bioactive ingredients, namely, those obtained from natural sources with environmentally friendly connotations and less toxic effects. A previous study of our research group optimized the extraction of phenolic compounds from Juglans regia by heat-assisted extraction. Due to its richness in different phenolic compounds, the present work aimed to develop a formulation containing J. regia leaf extract. The extract’s antioxidant, anti-tyrosinase, antimicrobial, anti-inflammatory, wound healing, cytotoxicity, and photostability properties were evaluated. The extract was then incorporated into an O/W base cream, followed by characterization of the final formulation in terms of its antioxidant properties, phenolic composition, and stability over time and at different storage conditions. The most abundant compounds in the hydroethanolic extract were 3-O-caffeoylquinic acid (18.30 ± 0.04 mg/g), quercetin-O-pentoside (9.64 ± 0.06 mg/g), and quercetin 3-O-glucoside (6.70 ± 0.19 mg/g). Besides those, the extract presented antioxidant, anti-inflammatory, wound closure, and antibacterial effects against several skin pathogens. In addition, HaCaT cell viability was maintained up to 98% at 400 µg/mL. Within Proteus vulgaris-infected HaCaT cells, the extract also presented an over 40% bacterial mortality rate at its nontoxic concentration (200 µg/mL). After incorporating the extract, the obtained formulation presented a good physicochemical profile over time and at different storage conditions while also maintaining its antioxidant effect; as such, it can be considered stable for topical application. Future work to evaluate its performance in terms of skin permeation and detailed toxicological studies with a focus on regulatory requirements, involving skin irritation, eye irritation, genotoxicity, photo-irritation, and dermal absorption, should be conducted, as the prepared formulation demonstrated relevant properties that deserve to be further explored.

Detection of biofilm formation of (Serratia and E.coli) and determination of the inhibitory effect of Quercus plant extract against these infectious pathogens

Biofilm is a complex microbial regional, especially resisting antimicrobials Quorum sensing function ate flow into an essential role in the composition concerning completely advanced superior biofilms on numerous microorganism, Biofilms change autonomous cells into particular cell groups. They are obtainable about comprehensions keen on biofilm materialization determined through the best-characterized strain, Escherichia col. The hastened biofilm obstacle of accord containing regular remedying decorates the requirement between significance with toughening modern rule approaches. By resources of the use of Congo process then PCR method since detection around biofilms arrangement, By way of the sunscreens of Quorum detecting were noticed over molecular finding using the PCR of the gene accountable for the structure of Biofilm in Serratia bacteria. The study showed that during the induction period, after 48 hours, the effects of bacterial inhabitation, the methanolic extract was more effective against (Serratia, Ecoli) regarding superb consciousness (10, 20, 30 mg/I).

Chemical Characterization, Antibacterial Activity, and Embryo Acute Toxicity of Rhus coriaria L. Genotype from Sicily (Italy)

This study reports a full characterization of the Sicilian sumac, Rhus coriaria L. This fruit represents a potential source of fiber (33.21 ± 1.02%) and unsaturated fatty acids, being the contents of linoleic and α-linolenic acids, 30.82 ± 1.21% and 1.85 ± 0.07%, respectively. In addition, the content of phenolic and total anthocyanin was 71.69 ± 1.23 mg/g as gallic acid equivalents, and 6.71 ± 0.12 mg/g as cyanidin-3-O-glucoside equivalents, respectively. The high content in mineral elements, consisting mainly of potassium, calcium, magnesium, and phosphorus, followed by aluminum, iron, sodium, boron, and zinc, was detected by inductively coupled plasma mass spectrometry (ICP-MS). Moreover, its antimicrobial activity was evaluated against multidrug resistant (MDR) microorganisms, represented by Escherichia coli and Klebsiella pneumoniae strains isolated from poultry. The activity of seven different sumac fruit extracts obtained using the following solvents—ethanol (SE), methanol (SM), acetone (SA), ethanol and water (SEW), methanol and water (SMW), acetone and water (SAW), water (SW)—was evaluated. The polyphenol profile of SM extract, which showed better activity, was analyzed by ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS). The major component identified was gallic acid, followed by quercetin, methyl digallate, pentagalloyl-hexoside, and kaempferol 3-O-glucoside. The non-toxicity of Sicilian R. coriaria was confirmed by testing the effect of the same extract on zebrafish embryos.

A Preliminary Study of Chemical Profiles of Honey, Cerumen, and Propolis of the African Stingless Bee Meliponula ferruginea

Recently, the honey and propolis of stingless bees have been attracting growing attention because of their health-promoting properties. However, studies on these products of African Meliponini are still very scarce. In this preliminary study, we analyzed the chemical composition of honey, two cerumen, and two resin deposits (propolis) samples of Meliponula ferruginea from Tanzania. The honey of M. ferruginea was profiled by NMR and indicated different long-term stability from Apis mellifera European (Bulgarian) honey. It differed significantly in sugar and organic acids content and had a very high amount of the disaccharide trehalulose, known for its bioactivities. We suggested trehalulose to be a potential marker for African stingless bee honey analogously to the recent proposal for Meliponini honey from Asia, South America, and Australia and demonstrated its easy discrimination by ¹³C NMR. Propolis and cerumen were studied by GC-MS (gas chromatography-mass spectometry). The samples contained mainly terpenoids (di-and triterpenes) but demonstrated qualitative and quantitative differences. This fact was an indication that possibly M. ferruginea has no strict preferences for resins used to construct and protect their nests. The antimicrobial and anti-quorum sensing properties of the two materials were also tested. These first results demonstrated that the honey, cerumen, and propolis of African stingless bees were rich in biologically active substances and deserved further research.

Inhibition of biofilm formation, quorum sensing and other virulence factors in Pseudomonas aeruginosa by polyphenols of Gynura procumbens leaves

Quorum sensing (QS) enables virulence factors in bacteria for biofilm formation and pathogenic invasion. Therefore, quorum quenching (QQ), disruption of QS circuit, becomes an alternative antimicrobial therapy. In this study, leaf extract of Gynura procumbens (GP) was used to inhibit biofilm and virulent factors in Pseudomonas aeruginosa. The extract inhibited the biofilm production (p ≤ 0.05) in P. aeruginosa strains MZ2F and MZ4A. The minimum biofilm eradication concentration (MBEC) was recorded at 250 and 500 μg/ml while total activity was found at 288 and 144 ml/g, respectively. Moreover, a significant reduction of virulence factors (p ≤ 0.05) at sub-MBEC without affecting the growth implies the QQ action of the extract. The bioactive fractions were rich in polyphenols and tentatively identified as quercetin and myricetin (R_f=0.53-0.60). Furthermore, we employed computational methods to validate our findings and their interactions with QS receptors (LasR and RhlR). Interestingly, docking studies have also shown that quercetin and myricetin are the promising anti-QS agents out of 31 GP compounds. Notably, their binding affinity ranged between -9.77 and -10.52 kcal/mol for both QS receptors, with controls ranging from -5.40 to -8.97 kcal/mol. Besides, ΔG of quercetin and myricetin with LasR was -71.56 and -74.88 kcal/mol, respectively. Moreover, compounds were suitable drug candidates with stable binding interactions. Therefore, the anti-QS activity of GP leaves and the identified polyphenols can be used in developing QQ-based therapeutics. Communicated by Ramaswamy H. Sarma.

Prebiotic Combinations Effects on the Colonization of Staphylococcal Skin Strains

Background: An unbalanced skin microbiota due to an increase in pathogenic vs. commensal bacteria can be efficiently tackled by using prebiotics. The aim of this work was to identify novel prebiotic combinations by exerting species-specific action between S. aureus and S. epidermidis strains. Methods: First, the antimicrobial/antibiofilm effect of Xylitol-XYL and Galacto-OligoSaccharides–GOS combined with each other at different concentrations (1, 2.5, 5%) against S. aureus and S. epidermidis clinical strains was evaluated in time. Second, the most species-specific concentration was used to combine XYL with Fructo-OligoSaccharides–FOS, IsoMalto-Oligosaccharides–IMO, ArabinoGaLactan–LAG, inulin, dextran. Experiments were performed by OD₆₀₀ detection, biomass quantification and LIVE/DEAD staining. Results: 1% XYL + 1% GOS showed the best species-specific action with an immediate antibacterial/antibiofilm action against S. aureus strains (up to 34.54% ± 5.35/64.68% ± 4.77) without a relevant effect on S. epidermidis. Among the other prebiotic formulations, 1% XYL plus 1% FOS (up to 49.17% ± 21.46/37.59% ± 6.34) or 1% IMO (up to 41.28% ± 4.88/36.70% ± 10.03) or 1% LAG (up to 38.21% ± 5.31/83.06% ± 5.11) showed antimicrobial/antibiofilm effects similar to 1% XYL+1% GOS. For all tested formulations, a prevalent bacteriostatic effect in the planktonic phase and a general reduction of S. aureus biofilm formation without loss of viability were recorded. Conclusion: The combinations of 1% XYL with 1% GOS or 1% FOS or 1% IMO or 1% LAG may help to control the balance of skin microbiota, representing good candidates for topic formulations.

Role of Antioxidant Molecules and Polymers in Prevention of Bacterial Growth and Biofilm Formation

Background:

Antioxidants are multifaceted molecules playing a crucial role in several cellular functions. There is by now a well-established knowledge about their involvement in numerous processes associated with aging, including vascular damage, neurodegenerative diseases and cancer. An emerging area of application has been lately identified for these compounds in relation to the recent findings indicating their ability to affect biofilm formation by some microbial pathogens, including Staphylococcus aureus, Streptococcus mutans, and Pseudomonas aeruginosa.

Methods:

A structured search of bibliographic databases for peer-reviewed research literature was performed using a focused review question. The quality of retrieved papers was appraised using standard tools.

Results:

One hundred sixty-five papers extracted from pubmed database and published in the last fifteen years were included in this review focused on the assessment of the antimicrobial and antibiofilm activity of antioxidant compounds, including vitamins, flavonoids, non-flavonoid polyphenols, and antioxidant polymers. Mechanisms of action of some important antioxidant compounds, especially for vitamin C and phenolic acids, were identified.

Conclusion:

The findings of this review confirm the potential benefits of the use of natural antioxidants as antimicrobial/antibiofilm compounds. Generally, gram-positive bacteria were found to be more sensitive to antioxidants than gram-negatives. Antioxidant polymeric systems have also been developed mainly derived from functionalization of polysaccharides with antioxidant molecules. The application of such systems in clinics may permit to overcome some issues related to the systemic delivery of antioxidants, such as poor absorption, loss of bioactivity, and limited half-life. However, investigations focused on the study of antibiofilm activity of antioxidant polymers are still very limited in number and therefore they are strongly encouraged in order to lay the foundations for application of antioxidant polymers in treatment of biofilm-based infections.

Phytochemical Diversity and Pharmacological Properties of Rhus coriaria

Rhus coriaria L. (Anacardiaceae), sumac, is a common condiment, appetizer and souring agent in the Mediterranean region that has a long history in traditional medicine. R. coriaria has been prescribed for the treatment of many ailments including diarrhea, ulcer, hemorrhoids, hemorrhage, wound healing, hematemesis, and eye ailments like ophthalmia and conjunctivitis. The plant is also used as diuresis, antimicrobial, abortifacient and as a stomach tonic. Sumac is known to be rich in different classes of phytochemicals including tannins, polyphenols, flavonoids, organic acids and essential oils and continues to be a hot topic for extensive research work designed for revealing its phytochemical constituents and evaluating its bioactive properties. This review summarizes the recent phytochemical and diverse bioactivity studies on R. coriaria, especially those concerned with antitumor, antioxidant, hypoglycemic, antimicrobial, and anti-inflammatory studies.

Phytochemical Study and Antibacterial and Antibiotic Modulation Activity of Punica granatum (Pomegranate) Leaves

This study aimed to determine phytochemical contents, antibacterial properties, and antibiotic modulating potential of Punica granatum leaf extracts: hexane, chloroform, ethyl acetate, ethanol, and aqueous extracts as well as an extract enriched with total oligomer flavonoids (TOFs). The TOF extract contained the highest value of phenols and flavonoids. Rutin, luteolin, gallic acid, and ellagic acid were determined by HPLC analysis of this extract. The antibacterial activity was assayed by the disc diffusion method and microdilution method against Staphylococcus aureus and Escherichia coli standard ATCC strains and clinical isolates resistant strains. The TOF extract was the most active against all tested strains. The checkerboard method was used for the determination of synergy between two antibiotics (amoxicillin and cefotaxime) and P. granatum leaf extracts. The best synergistic interaction was found with TOF extract combined with amoxicillin for penicillin-resistant E. coli and penicillin-resistant S. aureus. These results can be assigned to tannins, flavonoids, and phenolic acids found in P. granatum leaf extracts. Pomegranate leaf extracts or active compounds isolated from these extracts could be used to fight the emergence and spread of resistant bacterial strains.

Different Strategies to Obtain Corn (Zea mays L.) Germ Extracts with Enhanced Antioxidant Properties

Maize ( Zea mays L.) germs are by-products from the milling industry. The objective of this work was to compare the phenolic and lipophilic antioxidant fractions of yellow and white corn varieties, provided by Corn Valley S.r.l. (Piumbega, Mantova, Italy) and among the raw materials most processed by the company. The phenolic fraction, extracted with ultrasound-assisted extraction, alone and in combination with chemical and enzymatic hydrolyses, was analyzed with high-performance thin-layer chromatography and reversed-phase high-performance liquid chromatography-diode array detector. Among the various extraction techniques used, the combination of sonication and alkaline hydrolysis proved to be an effective method for the extraction of phenolic compounds from yellow and white germs, with the highest ferulic acid concentrations (636.54 ± 3.71 and 569.23 ± 1.69 mg FA/g dried extract, respectively), total phenolic contents (844.5 ± 64.6 and 742.8 ± 15.44 mg gallic acid equivalents/g dried extract, respectively), and the best antioxidant activity (14.33 ± 0.48 and 11.41 ± 1.1 µg/mL, respectively). The lipophilic fraction, extracted using supercritical carbon dioxide was analyzed by gas chromatography-mass spectrometry. The unsaponifiable fractions were found to be 2.41% ± 0.24% in yellow corn and 1.85% ± 0.08% in white corn; β-sitosterol, campesterol, and stigmasterol were identified as the main phytosterols characterizing both lipophilic extracts which showed the most effective antioxidant activity (1.29 ± 0.26 mg/mL and 1.33 ± 0.21 mg/mL, respectively) compared with the control. Finally, the phenolic and lipophilic extracts obtained from maize by-products may be reintroduced into the health-oriented market as extracts enriched of high-added value biomolecules with antioxidant activity both as active molecules and as additives of natural origin.

Effect of flavonoids on antimicrobial activity of microorganisms present in dental plaque

PURPOSE

Dental caries is a multi-factorial oral disease, requiring a susceptible host, cariogenic microorganisms and suitable substrate. Caries is extended worldwide in spite of the availability of countless prophylactic means, including fluoride toothpaste and dental sealers. Many efforts have been made to achieve isolation of pure natural products for medicinal use. Flavonoids are bioactive polyphenol compounds possessing multidimensional effects such as antibacterial action.

METHODS

The present study targeted the characterization of antibacterial and antifungal activity of various flavonoids (apigenin, catechin, luteolin, morin, myricetin, naringin, quercetin and rutin). Nine strains present in dental plaque were used: Agreggatibacter actinomycetemcomitans, Actinomyces naeslundii, Actinomyces viscosus, Enterococcus faecalis, Escherichia coli, Lactobacillus casei, Staphylococcus aureus, Streptococcus oralis and Streptococcus sanguinis as well as Candida albicans fungal strain.

RESULTS

Results revealed that luteolin, morin, naringin, quercetin and rutin effectively inhibited bacterial and fungal growth. However, morin was the most effective flavonoid.

CONCLUSION

It might then be concluded that flavonoids show bacteriostatic effect on all of tested bacteria and fungus.

Quorum sensing in food spoilage and natural-based strategies for its inhibition

Food can harbor a variety of microorganisms including spoilage and pathogenic bacteria. Many bacterial processes, including production of degrading enzymes, virulence factors, and biofilm formation are known to depend on cell density through a process called quorum sensing (QS), in which cells communicate by synthesizing, detecting and reacting to small diffusible signaling molecules - autoinducers (AI). The disruption of QS could decisively contribute to control the expression of many harmful bacterial phenotypes. Several quorum sensing inhibitors (QSI) have been extensively studied, being many of them of natural origin. This review provides an analysis on the role of QS in food spoilage and biofilm formation within the food industry. QSI from natural sources are also reviewed towards their putative future applications to prolong shelf life of food products and decrease foodborne pathogenicity.

Polyphenols From Vitis vinifera Lambrusco By-Products (Leaves From Pruning): Extraction Parameters Evaluation Through Design of Experiment

Vitis vinifera L. leaves from pruning are by-products of the wine industry and represent an important source of secondary raw material, thanks to their polyphenols content. Optimization of the extraction processes is a key factor for their valorization, and Design of Experiment (DOE) could be a tool to obtain the most performing extract in terms of polyphenols quality/quantity and bioactivity. Vitis vinifera Lambrusco leaves were subjected to ultrasound-assisted extractions guided by a 23 factorial design. Three independent parameters (% solvent, time of extraction, and solvent:solid ratio) were considered to evaluate the extraction process by analyzing the extraction yield, the total phenolic content (Folin-Ciocalteu assay), and the antioxidant capacity (DPPH assay). Moreover, the content of the main molecules was identified and quantified by reversed-phase high-performance liquid chromatography coupled with diode array detection and mass spectrometry. The DOE highlighted the best extraction conditions that showed slight changes considering the different evaluating parameters. The highest extraction yield was obtained by extraction with 100% water, 60 minutes of extraction time, and 30:1 solvent:solid ratio, but it was neither the richest in polyphenols nor antioxidant capacity. The latter 2 characteristics were associated with the extraction performed using 50% ethanol, 35 minutes of extraction time, and a 20:1 solvent:solid ratio. That extract also exhibited the highest quantity of flavonols.

Antibacterial and antibiofilm activity of acetone leaf extracts of nine under-investigated south African Eugenia and Syzygium (Myrtaceae) species and their selectivity indices

BACKGROUND

Antimicrobial resistance (AMR) remains an important global health issue but the gap between AMR and development of new antimicrobials is increasing. Plant extracts may have good activity per se or may be sources of effective antimicrobial compounds which can act against planktonic and/or biofilms of pathogens. We determined the antimicrobial efficacy and cytotoxicity of some under-investigated plants from the Myrtaceae family endemic to South Africa. The ability of the plant extracts to inhibit or destroy pre-formed bacterial biofilms was also determined.

METHODS

Based on previous preliminary in vitro screening and on chemotaxonomy, nine species from the Myrtaceae family were selected. The antimicrobial activity of the crude acetone leaf extracts was determined against six common nosocomial pathogens, namely: Gram-positive bacteria (Bacillus cereus, Enterococcus faecalis, Staphylococcus aureus), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella Typhimurium) using a two-fold serial microdilution assay with p-iodonitrotetrazolium violet as growth indicator. The number of antimicrobial compounds present in extracts was determined by bioautography. Cytotoxicity of extracts was determined against Vero kidney cells using a colorimetric tetrazolium-based assay. The total antibacterial activity (TAA) in ml/g and selectivity index (LC50/MIC) of the plant extracts were calculated. A modified crystal violet assay was used to determine the antibiofilm activity of the extracts.

RESULTS

Syzygium legatii, Syzygium masukuense, and Syzygium species A had the best activities against Gram-negative and Gram-positive bacteria (MIC) values ranging from 0.04-0.08 mg/ml. Eugenia erythrophylla had the best MIC (0.02 mg/ml) against Bacillus cereus. Many extracts had relatively low cytotoxicity (LC50 > 20 μg/ml) leading to reasonable selectivity indices. Three leaf extracts (Syzygium masukuense, Syzygium species A, and Eugenia natalitia) were moderately cytotoxic (20 μg/ml < LC50 < 100 μg/ml). The plant extracts had a good capacity to reduce biofilm formation and good to poor potential to destroy pre-formed biofilms.

CONCLUSIONS

The plant species examined in this study had varying degrees of antibacterial activity against bacterial planktonic and biofilm forms with some having good activity against both forms. Several of these selected species may be potential candidates for further investigation to isolate antimicrobial compounds and to determine the mechanism of activity.

Polyphenolic profile, antibacterial activity and brine shrimp toxicity of leaf extracts from six Tunisian spontaneous species

The aim of this study was to investigate the polyphenolic profile and biological properties of leaves acetonic extracts from six Tunisian spontaneous plants of Marrubium vulgare L., Rhus tripartita (Ucria) D.C., Hernaria fontanesii J. Gay subsp. fontanesii, Ziziphus lotus L., Plantago ovata Forsk., Thymelaea hirsuta (L.) Endl. Bioassay-guided and HPLC-PDA-ESI-MS procedures demonstrated that R. tripartita contained the highest amount of phenolic compounds (1475.1 µg/g), followed by Z. lotus (1087.8 µg/g) and P. ovata (1027.6 µg/g). Interestingly, in R. tripartita myricetin-3-O-galactoside turned out to be the most abundant one. The plant extracts showed antimicrobial efficacy against Listeria monocytogenes, Staphylococcus aureus and S. epidermidis including methicillin resistant strains; no activity was detected against Gram-negative bacteria. R. tripartita revealed the best MIC and MBC values and caused significant decrease of S. aureus biofilm. Both R. tripartita and Z. lotus did not display any toxicity against Artemia salina Leach (LC₅₀ > 1000 μg/mL).

Antimicrobial and Antibiofilm Activity against Staphylococcus aureus of Opuntia ficus-indica (L.) Mill. Cladode Polyphenolic Extracts

Plant extracts are a rich source of natural compounds with antimicrobial properties, which are able to prevent, at some extent, the growth of foodborne pathogens. The aim of this study was to investigate the potential of polyphenolic extracts from cladodes of Opuntia ficus-indica (L.) Mill. to inhibit the growth of some enterobacteria and the biofilm formation by Staphylococcus aureus. Opuntia ficus-indica cladodes at two stages of development were analysed for total phenolic content and antioxidant activity by Oxygen Radical Absorbance Capacity (ORAC) and Trolox equivalent antioxidant capacity (TEAC) (in vitro assays) and by cellular antioxidant activity in red blood cells (CAA-RBC) (ex vivo assay). The Liquid Chromatography Time-of-Flight Mass Spectrometry (LC/MS–TOF) analysis of the polyphenolic extracts revealed high levels of piscidic acid, eucomic acid, isorhamnetin derivatives and rutin, particularly in the immature cladode extracts. Opuntia cladodes extracts showed a remarkable antioxidant activity (in vitro and ex vivo), a selective inhibition of the growth of Gram-positive bacteria, and an inhibition of Staphylococcus aureus biofilm formation. Our results suggest and confirm that Opuntia ficus-indica cladode extracts could be employed as functional food, due to the high polyphenolic content and antioxidant capacity, and used as natural additive for food process control and food safety.

Flavonoids in Ecuadorian Oreocallis grandiflora (Lam.) R. Br.: Perspectives of Use of This Species as a Food Supplement

Oreocallis grandiflora (Lam.) R. Br. is an Ecuadorian species belonging to the Proteaceae family, commonly known as cucharillo (Loja and Zamora provinces), cucharilla (Sierra region), gañal (Bolívar province), and algil (Chimborazo province). Its leaves and flowers, collected during blooming, are traditionally used for oral administration to treat liver diseases, vaginal bleeding, and ovary/uterus inflammation and as digestive, diuretic, and hypoglycemic remedy. Related literature does not report any scientific evidences regarding the chemical composition of the used parts of this species (leaves and flowers), while few indications are reported about the healthy properties of their preparations. Based on these premises, the present research was performed with the objectives to fill the gaps of the chemical and biological knowledge about this species, enriching the knowledge related to the plant biodiversity of Amazonian Ecuador and to the ethnobotanical tradition of Andean communities. Chemical and biological investigation (in vitro antioxidant and anti-inflammatory activity) of flower and leaf hydroalcoholic extracts shed a light on the functional metabolites putatively involved in healthy properties of the O. grandiflora traditional preparations. The chemical fingerprinting achieved by HPTLC and ¹HNMR analyses showed the presence of flavonoids, subsequently quantitatively estimated by AlCl₃ complexation assay and HPLC-DAD. Silica gel chromatography allowed the isolation of the main compounds of the flower extract: quercetin 3-O-β-glucuronide and myricetin 3-O-β-glucuronide. RP-HPLC-DAD-MS analyses showed the presence of quercetin 3-O-rutinoside and isorhamnetin 3-O-rutinoside, in addition to the above-mentioned molecules, in the leaf extract. Regarding the antioxidant (DPPH test, a radical scavenging assay) and anti-inflammatory (WST-1 assay, an oxidative burst test) activities, leaf extract showed the most promising results when compared to the positive controls. The same extract, however, exhibited a higher cytotoxicity compared to the flower extract, indicating the latter preparation as the most interesting anti-inflammatory crude drug.

Biochemical Characterization of Clinical Strains of Staphylococcus spp. and Their Sensitivity to Polyphenols-Rich Extracts from Pistachio (Pistacia vera L.)

We characterized a number of clinical strains of Staphylococcus spp. and investigated their sensitivity against polyphenols-rich extracts from natural raw and roasted pistachios (NPRE and RPRE, respectively). Out of 31 clinical isolates of Staphylococcus spp., 23 were coagulase-positive and identified as S. aureus, of which 21 were MRSA. Polyphenols-rich extracts from natural pistachios and roasted pistachios were prepared: the total phenols content, expressed as gallic acid equivalent (GAE)/100 g fresh weight (FW), was higher in natural pistachios (359.04 ± 8.124 mg) than roasted pistachios (225.18 ± 5.055 mg). The higher total phenols content in natural pistachios also correlated to the higher free-radical scavenging activity found by DPPH assay: NPRE and RPRE showed IC₅₀ values of 0.85 (C.L. 0.725⁻0.976 mg mL^-1) and 1.15 (C.L. 0.920⁻1.275 mg mL^-1), respectively. Both NPRE and RPRE were active against S. aureus 6538P and Staph. spp. clinical isolates, with RPRE being the most active (MIC values ranging between 31.25 and 2000 μg mL^-1). The antimicrobial potential of pistachios could be used to identify novel treatments for S. aureus skin infections.

Current Screening Methodologies in Drug Discovery for Selected Human Diseases

The increase of many deadly diseases like infections by multidrug-resistant bacteria implies re-inventing the wheel on drug discovery. A better comprehension of the metabolisms and regulation of diseases, the increase in knowledge based on the study of disease-born microorganisms’ genomes, the development of more representative disease models and improvement of techniques, technologies, and computation applied to biology are advances that will foster drug discovery in upcoming years. In this paper, several aspects of current methodologies for drug discovery of antibacterial and antifungals, anti-tropical diseases, antibiofilm and antiquorum sensing, anticancer and neuroprotectors are considered. For drug discovery, two different complementary approaches can be applied: classical pharmacology, also known as phenotypic drug discovery, which is the historical basis of drug discovery, and reverse pharmacology, also designated target-based drug discovery. Screening methods based on phenotypic drug discovery have been used to discover new natural products mainly from terrestrial origin. Examples of the discovery of marine natural products are provided. A section on future trends provides a comprehensive overview on recent advances that will foster the pharmaceutical industry.

Antibacterial and Antibiofilm Effects of Zanthoxylum bungeanum Leaves against Staphylococcus aureus

Biofilm formation by Staphylococcus aureus on food contact surfaces is one of the most important issues for the food safety. The difficulties in controlling biofilms have driven the search for new antibacterial and antibiofilm agents from natural resources. The aims of the present study were to investigate the antibacterial and antibiofilm activities of the methanolic extract from Zanthoxylum bungeanum Maxim. leaves and identify the active compounds. By bioassay guide of inhibitory activity against S. aureus, four antibacterial compounds were separated from this extract and identified as neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid and 4- O-caffeoyl-2,3-dihydroxy-2- C-methylbutyric acid based on MS and NMR data analyses. The four compounds exhibited moderate antibacterial activity against S. aureus with minimum inhibitory concentration of 5 mg/mL. Moreover, a fraction consisted of the four compounds was subjected to antibiofilm assays against S. aureus. Crystal violet staining and XTT reduction assay demonstrated that this fraction showed an excellent inhibitory efficacy on the biomass and metabolic activity of S. aureus biofilm. Scanning electron microscopic observation displayed that this fraction induced severe morphological changes in the architecture of S. aureus biofilm, which further confirmed that it possessed a potent inhibitory activity on the biofilm formation of S. aureus. So, these results suggested that Z. bungeanum leaves could be used as an attractive and promising candidate for the development of natural antibacterial agent for controlling food-related bacterial biofilms.

Myrcia splendens (Sw.) DC. (syn. M. fallax (Rich.) DC.) (Myrtaceae) Essential Oil from Amazonian Ecuador: A Chemical Characterization and Bioactivity Profile

In this study, we performed the chemical characterization of Myrcia splendens (Sw.) DC. (Myrtaceae) essential oil from Amazonian Ecuador and the assessment of its bioactivity in terms of cytotoxic, antibacterial, and antioxidant activity as starting point for possible applicative uses. M. splendens essential oil, obtained by hydro-distillation, was analyzed by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID): the major components were found to be trans-nerolidol (67.81%) and α-bisabolol (17.51%). Furthermore, we assessed the cytotoxic activity against MCF-7 (breast), A549 (lung) human tumor cell lines, and HaCaT (human keratinocytes) non-tumor cell line through 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) test: promising results in terms of selectivity and efficacy against the MCF-7 cell line (IC₅₀ of 5.59 ± 0.13 μg/mL at 48 h) were obtained, mainly due to α-bisabolol. Furthermore, antibacterial activity against Gram positive and negative bacteria were performed through High Performance Thin Layer Chromatography (HPTLC) bioautographic assay and microdilution method: trans-nerolidol and β-cedren-9-one were the main molecules responsible for the low antibacterial effects against human pathogens. Nevertheless, interesting values of Minimum Inhibitory Concentration (MIC) were noticeable against phytopathogen strains. Radical scavenging activity performed by HPTLC bioautographic and spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) approaches were negligible. In conclusion, the essential oil revealed a good potential for plant defense and anti-cancer applications.