Effects of structural differences on the antibacterial activity of biflavonoids from fruits of the Brazilian peppertree (Schinus terebinthifolius Raddi)

Luteolin: A novel approach to fight bacterial infection

Diseases caused by bacteria significantly impact public health, causing both acute and chronic issues, sequelae, and death. The problems get even more significant, considering the antimicrobial resistance. Bacterial resistance occurs when antibacterial drugs fail to kill the microbes, leading to the persistence of infection and pathogen spread in the host. Thus, the search for new molecules with antibacterial activity dramatically impacts human health. Natural products have proven to be a prosperous source of these agents. Among them, the flavonoids deserve to be highlighted. They are secondary metabolites, primarily involved in plant signaling and protection. Thus, they play an essential role in plant adaptation to the environment. Herein, we will focus on luteolin because it is commonly found in edible plants and has diverse pharmacological properties such as anti-inflammatory, anticancer, antioxidant, and antimicrobial. We will further explore the luteolin antibacterial activity, mechanisms of action, structure-activity relationship, and toxicity of luteolin. Thus, we have included reports of luteolin with antibacterial activity recently published, as well as focused on nanotechnology as a pivotal and helpful approach for the clinical use of luteolin. This review aims to foster future research on luteolin as a therapeutic agent for treating bacterial infection.

Recent Advances, Challenges, and Functional Applications of Natural Phenolic Compounds in the Meat Products Industry

Natural phenolic compounds (NPCs) have been proven to effectively extend the storage time of meat products in recent years. To promote the discovery of more NPCs and their applications, this review examines recent progress in the classification, antioxidant, and antibacterial mechanisms of NPCs used in meat products. These compounds are found in both edible and inedible parts of plants, including fruits, vegetables, and trees. The recycling of agricultural by-products aligns with green agricultural trends and serves as a guideline for developing new sources of natural additives. Studies on the application of NPCs in various livestock and poultry products, either directly mixed into the matrix or indirectly contacted by preparation into bioactive films and packaging materials, has highlighted the great potential of NPCs. The pro-oxidative effects of NPCs on proteins and their interactions with biological macromolecules, such as proteins, provide new ideas for in-depth research on antioxidant and antibacterial mechanisms.

Antimicrobial activities of natural flavonoids against foodborne pathogens and their application in food industry

The application of natural alternatives as food preservatives has gained much attention due to the escalating negative perception of synthetic preservatives among consumers and the spread of drug-resistance foodborne pathogens. Natural flavonoids have the potential to be employed for food safety due to their antimicrobial properties against a wide range of foodborne pathogenic microorganisms. In this perspective, we reviewed the antimicrobial activities of natural flavonoids, the mechanism of action, as well as their application for food safety and quality. Various strategies for the incorporation of flavonoids into food products were highlighted, including direct addition to food formulations, encapsulation as micro or nanocarriers, and incorporation into edible or active films and coatings. Furthermore, we discussed the current challenges of industrial application of flavonoids, and proposed future trends to enhance their potential as natural preservatives. This review provides a theoretical foundation for the further development and application of flavonoids for food safety.

Cytotoxic and antibacterial compounds from Schinus terebinthifolia Raddi fruits

Chromatographic procedures of extracts of Schinus terebinthifolia Raddi fruits afforded (Z)-masticadienoic (1) and 3β-masticadienolic (2) acids, tetrahydroamentoflavone (3), and 4-O-methyl gallic acid (4). Addicionally, the derivative 6-oxo masticadienoic acid (1a) was prepared by an allylic oxidation. The chemical structures of obtained compounds were elucidated by spectrometric data analyses. Furthermore, both the semi-synthetic derivative and the metabolites were subjected to in vitro cytotoxicity against the A549 human lung cancer cell line, as well as antimicrobial activity tests. Compounds 2 and 1a exhibited cytotoxicity towards A549 cells with IC50 values of 20.13 and 6.11 µM, respectively. In the tests against pathogens, the CHCl3 and EtOAc soluble fractions of MeOH extract along with the pure compounds, exhibited antibacterial activity against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Except for 4-O-methyl gallic acid, the other pure compounds showed inhibitory microbial activities with MIC values ranging from 0.25 μg/mL to 25 μg/mL doses.

Natural phenolic compounds: Antimicrobial properties, antimicrobial mechanisms, and potential utilization in the preservation of aquatic products

Natural antibacterials have stood out in the last decade due to the growing demand for reducing chemical preservatives in food. In particular, natural phenolic compounds are secondary metabolites produced by plants for numerous functions including antimicrobial defence. Polyphenol has significant antimicrobial activity, but its antimicrobial properties are affected by the cell structure difference of bacteria, the concentration, type, and extraction method of polyphenol, and the treatment time of bacteria exposed to polyphenol. Therefore, this paper analyzed the antibacterial activity and mechanism of polyphenol as an antimicrobial agent. However, there remained significant considerations, including the interaction of polyphenols and food matrix, environmental temperature, and the effect of color and odor of some polyphenols on sensory properties of aquatic products, and the additive amount of polyphenols. On this basis, the application strategies of polyphenols as the antimicrobial agent in aquatic products preservation were reviewed.

Inhibitory effect of benzocaine from Schisandra chinensis on Alternaria alternata

The clinical effects of Schisandra chinensis against human disease are well-documented; however, studies on its application in controlling plant pathogens are limited. Here, we investigated its inhibitory effect on the growth of Alternaria alternata, a fungus which causes significant post-harvest losses on apples, known as black spot disease. S. chinensis fruit extract exhibited strong inhibitory effects on the growth of A. alternata with an EC50 of 1882.00 mg/L. There were 157 compounds identified in the extract by high performance liquid chromatography-mass spectrometry, where benzocaine constituted 14.19% of the extract. Antifungal experiments showed that the inhibitory activity of benzocaine on A. alternata was 43.77-fold higher than the crude extract. The application of benzocaine before and after A. alternata inoculation on apples prevented the pathogen infection and led to mycelial distortion according to scanning electron microscopy. Transcriptome analysis revealed that there were 4226 genes differentially expressed between treated and untreated A. alternata-infected apples with benzocaine. Metabolomics analysis led to the identification of 155 metabolites. Correlation analysis between the transcriptome and metabolome revealed that benzocaine may inhibit A. alternata growth via the beta-alanine metabolic pathway. Overall, S. chinensis extract and benzocaine are environmentally friendly plant-based fungicides with potential to control A. alternata.

Chemical and cytotoxicity profiles of 11 pink pepper (Schinus spp.) samples via non-targeted hyphenated high-performance thin-layer chromatography

INTRODUCTION

Pink pepper is a worldwide used spice that corresponds to the berries of two species, Schinus terebinthifolia Raddi or S. molle L. (Anacardiaceae). Toxic and allergic reactions by ingestion or contact with these plants were reported, and classical in vitro studies have highlighted the cytotoxic properties of apolar extracts from the fruits.

OBJECTIVES

Perform a non-targeted screening of 11 pink pepper samples for the detection and identification of individual cytotoxic substances.

METHODS

After reversed-phase high-performance thin-layer chromatography (RP-HPTLC) separation of the extracts and multi-imaging (UV/Vis/FLD), cytotoxic compounds were detected by bioluminescence reduction from luciferase reporter cells (HEK 293 T-CMV-ELuc) applied directly on the adsorbent surface, followed by elution of detected cytotoxic substance into atmospheric-pressure chemical ionization high-resolution mass spectrometry (APCI-HRMS).

RESULTS

Separations for mid-polar and non-polar fruit extracts demonstrated the selectivity of the method to different substance classes. One cytotoxic substance zone was tentatively assigned as moronic acid, a pentacyclic triterpenoid acid.

CONCLUSION

The developed non-targeted hyphenated RP-HPTLC-UV/Vis/FLD-bioluminescent cytotoxicity bioassay-FIA-APCI-HRMS method was successfully demonstrated for cytotoxicity screening (bioprofiling) and respective cytotoxin assignment.

Antibiotic-Potentiating Activity of the Schinus terebinthifolius Raddi Essential Oil against MDR Bacterial Strains

Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus are the primary bacteria that cause clinical infections, such as urinary and intestinal infections, pneumonia, endocarditis, and sepsis. Bacterial resistance is an innate natural occurrence in microorganisms, resulting from mutations or the lateral exchange of genetic material. This serves as evidence for the association between drug consumption and pathogen resistance. Evidence has demonstrated that the association between conventional antibiotics and natural products is a promising pharmacological strategy to overcome resistance mechanisms. Considering the large body of research demonstrating the significant antimicrobial activities of Schinus terebinthifolius Raddi, the present study aimed to evaluate the chemical composition and antibiotic-enhancing effects of Schinus terebinthifolius Raddi essential oil (STEO) against the standard and multidrug-resistant strains of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The STEO was extracted by hydrodistillation using a Clevenger-type vacuum rotary evaporator. The Minimum Inhibitory Concentration (MIC) of the STEO was assessed by the microdilution method to evaluate the antibacterial activity. The antibiotic-enhancing activity of the essential oil was assessed by determining the MIC of antibiotics in the presence of a sub-inhibitory concentration (MIC/8) of the natural product. The GC-MS analysis revealed alpha-pinene (24.3%), gamma-muurolene (16.6%), and myrcene (13.7%) as major constituents of the STEO. The STEO potentiated the enhanced antibacterial activity of norfloxacin and gentamicin against all the strains and increased the action of penicillin against the Gram-negative strains. Therefore, it is concluded that although the STEO does not exhibit clinically effective antibacterial activity, its association with conventional antibiotics results in enhanced antibiotic activity.

Effects of flavonoids on membrane adaptation of food-associated bacteria

The effects of naringenin and the biflavonoids amentoflavone and tetrahydroamentoflavone on select bacterial lipids (carotenoids, fatty acids, and menaquinones) and membrane fluidity based on Laurdan generalized polarization were investigated. For this purpose, the pigment-forming food-associated microorganisms Staphylococcus xylosus (DSM 20266^T and J70), Staphylococcus carnosus DSM 20501^T, and Micrococcus luteus (ATCC 9341 and J3) were studied. The results suggest an envelope stress response by microorganisms due to flavonoids and an employment of adaptive mechanisms using carotenoids, fatty acids, and menaquinones. The flavonoid monomer naringenin impacted carotenoids, fatty acids, menaquinones, and membrane fluidity. Naringenin significantly influenced the carotenoid profile, particularly by an increase in the relative proportion of 4,4'-diaponeurosporenoic acid in Staphylococcus xylosus. Amentoflavone caused changes mainly in the membrane of Micrococcus luteus and decreased the menaquinone content. Tetrahydroamentoflavone mainly affected the carotenoids in the investigated strains. The noticeably different CCS value of tetrahydroamentoflavone compared to naringenin and amentoflavone revealed further insights into the structure-dependent effects of flavonoids. This study provides valuable insights into the response of pigment-forming food-associated microorganisms to naringenin, amentoflavone, and tetrahydroamentoflavone, which is important for the targeted and safe application of the latter as natural preservatives and useful for further research on the mechanisms of action.

A review of plant antipathogenic constituents: Source, activity and mechanism

Green prevention and control of plant pathogens is a development direction of sustainable and low-carbon agriculture given the limitation of traditional chemicals. Plant-derived antipathogenic constituents (PAPCs) exhibit the advantages of being environmental benign and a broad spectrum of target pathogens over traditional chemicals. Here, we review the research advances on plant sources, chemical compositions, activities of antipathogenic constituents in the past 20 years. Reported PAPCs are classified into categories of phenols, flavonoids, terpenoids, alkaloids and antimicrobial peptides. Angiosperms, gymnosperms and some lower plants are the main plant source of detected PAPCs. The PAPCs act on pathogens through multiple pathways including destroying cell structures, blocking key composition synthesis and inhibiting cell metabolism. The development trends of PAPCs are finally prospected. This review serves as a comprehensive review on the study of plant antipathogenic constituents and a key reference for forecasting the source, characteristic and activity of PAPC.

Analysis of Volatiles of Rose Pepper Fruits by GC/MS: Drying Kinetics, Essential Oil Yield, and External Color Analysis

Condiments and culinary supplements are subjected to long-term storage and may undergo physical, chemical, and biological changes that can influence their quality. Thus, the objective of the present study was to analyze the drying kinetics of rose pepper (Schinus terebinthifolius Raddi) fruits in an oven with forced air circulation at different temperatures, namely, 45, 55, 65, and 75°C, and determine the effective diffusion coefficient and activation energy using different mathematical models. Furthermore, the effects of the different drying temperatures were analyzed for external color parameters and yield of essential oil contents by gas chromatography coupled to a mass spectrometer. Of the ten models used for fitting, Thompson’s model was one with the best fitting to represent the drying of rose pepper fruits. The diffusion coefficient increases with the elevation of drying air temperature, described by the Arrhenius equation, with activation energy of 53.579 kJ·mol−1. The color of the fruits decreased in lightness (L ${}^{\ast }$ ) with the increase in temperature. Of the thirty-eight terpenes identified, α-pinene and cis-ocimene were the most abundant, with the overall highest yield being found at a drying temperature of 45°C.

Deleterious effects of Schinus terebinthifolius Raddi seed flour on cowpea weevil, Callosobruchus maculatus (F.), larval development

Schinus terebinthifolius, Raddi, has been extensively studied due to its anti-inflammatory and antibiotic properties. S. terebinthifolius was also toxic to some insects, however little has been explored about the nature of its insecticide compounds or the toxicity of this plant to insect species. In this work, we investigate the toxicity of S. terebinthifolius seed flour against the insect C. maculatus. S. terebinthifolius seed flour interfered with the post hatch development of the C. maculatus larvae, decreasing larval survival, mass and length. Using DEAE-cellulose chromatography, five protein fractions were isolated, a non-retained fraction (NRF) and four retained fractions, eluted with 0.25, 0.5, 0.7 and 1.0 M NaCl. Proteins with varying molecular masses were observed in all fractions. The majority protein bands were identified by mass spectrometry analysis and among the main identified proteins are 11S globulins (such glycinin), lipoxygenase, chitinases, 7S globulins (vicilins, canavalin and β conglycinin), annexin, catalase and sucrose binding protein. All DEAE-protein fractions were toxic to the insect, interfering with the post hatch larval development and survival. Decreases greater than 90% were observed in the larval mass and length at 20 days after oviposition (DAO) for larvae raised on diet containing 0.5% of some fractions. Alterations in the level of proteins, glucose and in the activity of the enzymes lipases and cysteine proteases were also detected in these larvae. Our results show that seeds of S. terebinthifolius have an arsenal of toxic proteins with potential for the control of the insect C. maculatus.

The antibacterial activity of natural-derived flavonoids

Flavonoids, a wide variety of phenolic secondary metabolites, are found in almost all plant families in the leaves, stems, roots, flowers, and seeds. Flavonoids could exert antibacterial activity via damaging the cytoplasmic membrane, inhibiting energy metabolism, and inhibiting the synthesis of nucleic acids, so flavonoids are considered constitutive antibacterial substances. This review aims to outline the recent advances of natural-derived flavonoids, including flavonoid glycosides with antibacterial potential to provide novel antibacterial lead hits/candidates, covering articles published between January 2016 and July 2021.

Antibacterial Effects of Flavonoids and Their Structure-Activity Relationship Study: A Comparative Interpretation

According to the latest report released by the World Health Organization, bacterial resistance to well-known and widely available antibacterial drugs has become a significant and severe global health concern and a grim challenge to tackle in order to cure infections associated with multidrug-resistant pathogenic microorganisms efficiently. Consequently, various strategies have been orchestrated to cure the severe complications related to multidrug-resistant bacteria effectively. Some approaches involved the retardation of biofilm formation and multidrug-resistance pumps in bacteria as well as the discovery of new antimicrobial agents demonstrating different mechanisms of action. In this regard, natural products namely alkaloids, terpenoids, steroids, anthraquinone, flavonoids, saponins, tannins, etc., have been suggested to tackle the multidrug-resistant bacterial strains owing to their versatile pharmacological effects. Amongst these, flavonoids, also known as polyphenolic compounds, have been widely evaluated for their antibacterial property due to their tendency to retard the growth of a wide range of pathogenic microorganisms, including multidrug-resistant bacteria. The hydroxylation of C5, C7, C3′, and C4′; and geranylation or prenylation at C6 have been extensively studied to increase bacterial inhibition of flavonoids. On the other hand, methoxylation at C3′ and C5 has been reported to decrease flavonoids’ antibacterial action. Hence, the latest information on the antibacterial activity of flavonoids is summarized in this review, with particular attention to the structure–activity relationship of this broad class of natural compounds to discover safe and potent antibacterial agents as natural products.

Natural biflavonoids as potential therapeutic agents against microbial diseases

Microbes broadly constitute several organisms like viruses, protozoa, bacteria, and fungi present in our biosphere. Fast-paced environmental changes have influenced contact of human populations with newly identified microbes resulting in diseases that can spread quickly. These microbes can cause infections like HIV, SARS-CoV2, malaria, nosocomial Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), or Candida infection for which there are no available vaccines/drugs or are less efficient to prevent or treat these infections. In the pursuit to find potential safe agents for therapy of microbial infections, natural biflavonoids like amentoflavone, tetrahydroamentoflavone, ginkgetin, bilobetin, morelloflavone, agathisflavone, hinokiflavone, Garcinia biflavones 1 (GB1), Garcinia biflavones 2 (GB2), robustaflavone, strychnobiflavone, ochnaflavone, dulcisbiflavonoid C, tetramethoxy-6,6″-bigenkwanin and other derivatives isolated from several species of plants can provide effective starting points and become a source of future drugs. These biflavonoids show activity against influenza, severe acute respiratory syndrome (SARS), dengue, HIV-AIDS, coxsackieviral, hepatitis, HSV, Epstein-Barr virus (EBV), protozoal (Leishmaniasis, Malaria) infections, bacterial and fungal infections. Some of the biflavonoids can provide antiviral and protozoal activity by inhibition of neuraminidase, chymotrypsin-like protease, DV-NS5 RNA dependant RNA polymerase, reverse transcriptase (RT), fatty acid synthase, DNA polymerase, UL54 gene expression, Epstein-Barr virus early antigen activation, recombinant cysteine protease type 2.8 (r-CPB2.8), Plasmodium falciparum enoyl-acyl carrier protein (ACP) reductase or cause depolarization of parasitic mitochondrial membranes. They may also provide anti-inflammatory therapeutic activity against the infection-induced cytokine storm. Considering the varied bioactivity of these biflavonoids against these organisms, their structure-activity relationships are derived and wherever possible compared with monoflavones. Overall, this review aims to highlight these natural biflavonoids and briefly discuss their sources, reported mechanism of action, pharmacological uses, and comment on resistance mechanism, flavopiridol repurposing and the bioavailability aspects to provide a starting point for anti-microbial research in this area.

Schinus terebinthifolius fruits intake ameliorates metabolic disorders, inflammation, oxidative stress, and related vascular dysfunction, in atherogenic diet-induced obese rats. Insight of their chemical characterization using HPLC-ESI-QTOF-MS/MS

ETHNOPHARMACOLOGY RELEVANCE

Schinus terebinthifolius is traditionally used for its anti inflammatory capacity, and indicated as a cardioprotective agent, whereas, its preventive effect against atherogenic diet fed (AD) induced metabolic disorders and the underlying mechanisms has not yet been explored.

AIM OF THE STUDY

This study was undertaken to investigate the ameliorative role of Schinus terebinthifolius fruits extract (STFE) against cardiovascular problem, oxidative and inflammatory status related to obesity in rats fed an atherogenic diet.

MATERIALS AND METHODS

The metabolites profile in STFE was evaluated using HPLC-DAD-ESI-QTOF-MS/MS analysis. In Wistar rats, atherogenic diet was added for 9 weeks to induce lipid accumulation simultaneously with STFE (50 mg/kg b. w) or saline treatment. Biochemical, oxidant, and inflammatory criteria together with hepatic and arterial integrity examination were assessed.

RESULTS

A total of thirty three metabolites were identified using HPLC-DAD-ESI-QTOF-MS, among them masazino-flavanone was the major compound (2645.50 μg/g DW). The results indicated that STFE supplementation during 9 weeks (50 mg/kg b. w.) significantly attenuated the altered lipid profile by decreasing the levels of TC, TG, LDL-C and increasing the HDL-C content both in plasma and liver, when compared with the AD-group. The histological analysis using ORO staining revealed a decrease in the lipid droplet deposit in the cytoplasm of hepatocytes of STFE + AD group. The addition of STFE could improve the glycemic status of AD-treated rats by decreasing the glucose and insulin secretion, and ameliorating the hepatic glycogen synthesis. The harmful effects of atherogenic diet on hepatic oxidative stress indicators (MDA, PC, GSH, SOD, CAT, and GPx), biochemical markers (AST, ALT, LDH and ALP), and liver function, were found to be decreased by the addition of STFE. Moreover, the reduction of inflammatory markers (CRP, IL-6 and TNF-α), associated to alleviating of aortic oxidative stress and integrity, highlighted the positive anti-atherogenic effect of STFE.

CONCLUSION

Overall, the pleiotropic protective effect observed with S. terebinthifolius fruits might be related to the presence of various bioactive compounds.

Biflavonoid as potential 3-chymotrypsin-like protease (3CLpro) inhibitor of SARS-Coronavirus

3CL protease is one of the key proteins expressed by SARS-Coronavirus-2 cell, the potential to be targeted in the discovery of antivirus during this COVID-19 pandemic. This protein regulates the proteolysis of viral polypeptide essential in forming RNA virus. 3CL protease (3CLpro) was commonly targeted in the previous SARS-Coronavirus including bat and MERS, hence, by blocking this protein activity, the coronavirus should be eradicated. This study aims to review the potency of biflavonoid as the SARS-Coronavirus-2 3CLpro inhibitor. The review was initiated by describing the chemical structure of biflavonoid and followed by listing its natural source. Instead, the synthetic pathway of biflavonoid was also elaborated. The 3CLpro structure and its function were also illustrated followed by the list of its 3D-crystal structure available in a protein data bank. Lastly, the pharmacophores of biflavonoid have been identified as a protease inhibitor, was also discussed. This review hopefully will help researchers to obtain packed information about biflavonoid which could lead to the study in designing and discovering a novel SARS-Coronavirus-2 drug by targetting the 3CLpro enzyme.

Volatile Phenols-Important Contributors to the Aroma of Plant-Derived Foods

Volatile phenols like phenylpropanoid and benzoid compounds originate from the aromatic amino acid phenylalanine, which is biosynthesized via the shikimate/arogenate pathway. These volatile compounds contribute to the aroma of a number of economically important plant-derived foods like herbs, spices and fruits. The sequestration of numerous phenylpropanoid and benzoid compounds as glycosides occurs widely in fruits, and this pool represents an important source of flavor that can be released during storage and processing. Therefore, this review will provide an overview of the biosynthesis of free and glycosylated phenylpropanoid and benzoid compounds and their reactions during food processing, which both lead to the generation of odor-active volatile phenols in plant-derived foods.