Identification of a novel storage glycine-rich peptide from guava (Psidium guajava) seeds with activity against Gram-negative bacteria

Antimicrobial Peptides From the Gut Microbiome of the Centenarians: Diversification of Biosynthesis and Youthful Development of Resistance Genes

Antimicrobial peptides (AMPs) offer a potential solution to the antibiotic crisis owing to their antimicrobial properties, and the human gut biome may be a source of these peptides. However, the potential AMPs and AMP resistance genes (AMPRGs) of gut microbes in different age groups have not been thoroughly assessed. Here, we investigated the potential development of AMPs and the distribution pattern of AMPRGs in the gut microbiome at different ages by analyzing the intestinal metagenomic data of healthy individuals at different life stages (CG: centenarians group n = 20; OAG: older adults group: n = 15; YG: young group: n = 15). Age-related increases were observed in the potential AMPs within the gut microbiome, with centenarians showing a greater diversity of these peptides. However, the gut microbiome of the CG group had a lower level of AMPRGs compared to that of the OAG group, and it was similar to the level found in the YG group. Additionally, conventional probiotic strains showed a significant positive correlation with certain potential AMPs and were associated with a lower detection of resistance genes. Furthermore, comparing potential AMPs with existing libraries revealed limited similarity, indicating that current machine learning models can identify novel peptides in the gut microbiota. These results indicate that longevity may benefit from the diversity of AMPs and lower resistance genes. Our findings help explain the age advantage of the centenarians and identify the potential for antimicrobial peptide biosynthesis in the human gut microbiome, offering insights into the development of antimicrobial peptide resistance and the screening of probiotic strains.

Comprehensive Review on Fruit Seeds: Nutritional, Phytochemical, Nanotechnology, Toxicity, Food Biochemistry, and Biotechnology Perspective

Fruit seeds are leftovers from a variety of culinary sectors. They are generally unutilized and contribute greatly to global disposals. These seeds not only possess various nutritional attributes but also have many heath-beneficial properties. One way to make use of these seeds is to extract their bioactive components and create fortified food items. Nowadays, researchers are highly interested in creating innovative functional meals and food components from these unconventional resources. The main objective of this manuscript was to determine the usefulness of seed powder from 70 highly consumed fruits, including Apple, Apricot, Avocado, Banana, Blackberry, Blackcurrant, Blueberry, Cherry, Common plum, Cranberry, Gooseberry, Jackfruit, Jamun, Kiwi, Lemon, Mahua, Mango, Melon, Olive, Orange, and many more have been presented. The nutritional attributes, phytochemical composition, health advantages, nanotechnology applications, and toxicity of these fruit seeds have been fully depicted. This study also goes into in-depth detailing on creating useful food items out of these seeds, such as bakery goods, milk products, cereal-based goods, and meat products. It also identifies enzymes purified from these seeds along with their biochemical applications and any research openings in this area.

The Biologically Active Biopolymer Silk: The Antibacterial Effects of Solubilized Bombyx mori Silk Fibroin with Common Wound Pathogens

Antibacterial properties are desirable in wound dressings. Silks, among many material formats, have been investigated for use in wound care. However, the antibacterial properties of liquid silk are poorly understood. The aim of this study is to investigate the inherent antibacterial properties of a Bombyx mori silk fibroin solution. Silk fibroin solutions containing ≥ 4% w/v silk fibroin do not support the growth of two common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. When liquid silk is added to a wound pad and placed on inoculated culture plates mimicking wound fluid, silk is bacteriostatic. Viability tests of the bacterial cells in the presence of liquid silk show that cells remain intact within the silk but could not be cultured. Liquid silk appears to provide a hostile environment for S. aureus and P. aeruginosa and inhibits growth without disrupting the cell membrane. This effect can be beneficial for wound healing and supports future healthcare applications for silk. This observation also indicates that liquid silk stored prior to processing is unlikely to experience microbial spoilage.

Psidium guajava: An Insight into Ethnomedicinal Uses, Phytochemistry, and Pharmacology

BACKGROUND

Psidium guajava (guava) is widely distributed in tropical and subtropical regions and adapted to various environmental conditions. Guava is an important economic fruit widely used as food and folk medicine. It contains flavonoids, alkaloids, tannins, triterpenoids, reducing sugars, essential oils, carotenoids, polyphenols, etc. The presence of triterpenoid acids such as guavacoumaric, ursolic, jacoumaric, guajavanoic, guavenoic, and Asiatic acids helps to develop novel drugs against various diseases. It is used traditionally for medicinal purposes, mainly for antioxidant, antimicrobial, antispasmodic, antidiabetic, anticancer, antiallergy, anti-inflammatory, and hepato-protective properties.

OBJECTIVE

The systematic literature study aims to summarize its botanical description, phytochemicals, pharmacological activities, and clinical trials. This review focuses on the plant's chemical composition and scientific approaches to human welfare.

METHODS

A systematic literature search was done on Psidium guajava through previous literature and online databases such as Google Scholar, Pubmed, Science Direct, etc., to explain its ethnomedicinal uses, phytochemistry, and pharmacological applications.

RESULTS

Previous literature studies of Psidium guajava suggest it can serve as antioxidant, antimicrobial, antispasmodic, antidiabetic, anticancer, anti-allergy, anti-inflammatory, and hepatoprotective effects. Successful clinical trials performed on the plant extracts against infantile rotaviral enteritis and infectious gastroenteritis showed future directions to work with the plant for clinical applications.

CONCLUSION

In this review, an attempt is made to show all literature studied, especially in phytochemistry, pharmacology, clinical trials and uses as traditional folk medicine around the world. The leaves have been used by folklore over the years to treat various ailments such as skin ulcers, diarrhoea, vaginal irritation, cough, conjunctivitis, etc. Further studies are required to explore more therapeutic remedies and to develop new medicines for future perspectives.

Plant derived antimicrobial peptides: Mechanism of target, isolation techniques, sources and pharmaceutical applications

Antimicrobial resistance is a global health and development threat which is caused by the excess and prolonged usage of antimicrobial compounds in agriculture and pharmaceutical industries. Resistance of pathogenic microorganisms to the already existing drugs represent a serious risk to public health. Plant sources such as cereals, legumes, fruits and vegetables are potential substrates for the isolation of antimicrobial peptides (AMP) with broad spectrum antimicrobial activity against bacteria, fungi and viruses with novel immunomodulatory activities. Thus, in the quest of new antimicrobial agents, AMPs have recently gained interest. Therefore, AMP can be used in agriculture, pharmaceutical and food industries. This review focuses on various explored and unexplored plant based food sources of AMPs, their isolation techniques and antimicrobial mechanism of peptides. Therefore, the literature discussed in this review paper will prove beneficial the research purposes for agriculture, pharmaceutical and food industries. PRACTICAL APPLICATIONS: Isolation of antimicrobial peptides (AMPs) can be done on industrial scale. AMP isolated from food sources can be used in pharmaceutical and agriculture industries. AMP from natural sources mitigate the problem of antimicrobial resistance. AMP isolated from food products can be used as nutraceutical.

Guava (Psidium guajava L.) seed: A low-volume, high-value byproduct for human health and the food industry

Guava processing industries generate peel and seeds as primary waste fractions. Guava seeds obtained after fruit processing possess untapped potential in the field of food science due to the presence of a diversity of nutritional and bioactive compounds. Along with offering a detailed understanding of the nutritional attributes of guava seeds, the present review comprehensively elaborates on the therapeutic activities of their bioactive compounds, their techno-functional properties, and their other edible and nonedible applications. The limited molecular and biochemical mechanistic studies outlining the antioxidant, immunomodulatory, anticancer, antimicrobial, neuroprotective and antidiabetic activities of guava seeds available in the literature are also extensively discussed in this review. The use of guava seed constituents as food additives and food functional and structural modulators, primarily as fat reducers, emulsifiers, water and oil holding agents, is also conceptually explained. Additional human intervention and molecular mechanistic studies deciphering the effects of guava seeds on various diseases and human health are warranted.

Plant-Derived Antimicrobial Peptides: Novel Preservatives for the Food Industry

Food spoilage is a widespread issue brought on by the undesired growth of microbes in food products. Thousands of tons of usable food or food products are wasted every day due to rotting in different parts of the world. Several food preservation techniques are employed to prevent food from rotting, including the use of natural or manufactured chemicals or substances; however, the issue persists. One strategy for halting food deterioration is the use of plant-derived antimicrobial peptides (AMPs), which have been investigated for possible bioactivities against a range of human, plant, and food pathogens. The food industry may be able to benefit from the development of synthetic AMPs, produced from plants that have higher bioactivity, better stability, and decreased cytotoxicity as a means of food preservation. In order to exploit plant-derived AMPs in various food preservation techniques, in this review, we also outline the difficulties in developing AMPs for use as commercial food preservatives. Nevertheless, as technology advances, it will soon be possible to fully explore the promise of plant-derived AMPs as food preservatives.

The Updated Review on Plant Peptides and Their Applications in Human Health

Biologically active plant peptides, consisting of secondary metabolites, are compounds (amino acids) utilized by plants in their defense arsenal. Enzymatic processes and metabolic pathways secrete these plant peptides. They are also known for their medicinal value and have been incorporated in therapeutics of major human diseases. Nevertheless, its limitations (low bioavailability, high cytotoxicity, poor absorption, low abundance, improper metabolism, etc.) have demanded a need to explore further and discover other new plant compounds that overcome these limitations. Keeping this in mind, therapeutic plant proteins can be excellent remedial substitutes for bodily affliction. A multitude of these peptides demonstrates anti-carcinogenic, anti-microbial, anti-HIV, and neuro-regulating properties. This article's main aim is to list out and report the status of various therapeutic plant peptides and their prospective status as peptide-based drugs for multiple diseases (infectious and non-infectious). The feasibility of these compounds in the imminent future has also been discussed.

Antiulcer Potential of Psidium guajava Seed Extract Supported by Metabolic Profiling and Molecular Docking

One of the most severe human health problems is gastric ulceration. The main aim of our study is to explore the gastroprotective effect of the Psidium guajava seeds extract (PGE). Metabolic profiling based on LC-HRMS for the extract led to the dereplication of 23 compounds (1–23). We carried out a gastric ulcer model induced by indomethacin in male albino rats in vivo and the extract of PGE was investigated at a dose of 300 mg/kg in comparison to cimetidine (100 mg/kg). Furthermore, the assessment of gastric mucosal lesions and histopathology investigation of gastric tissue was done. It has been proved that Psidium guajava seeds significantly decreased the ulcer index and protected the mucosa from lesions. The antiulcer effect of Psidium guajava seed extract, which has the power of reducing the ensuing inflammatory reactions, can counteract the inflammation induced by indomethacin by the downregulation of relative genes expression (IL-1β, IL-6, and TNF-α). Moreover, PGE significantly downregulated the increased COX-2, TGF-β, and IGF-1 relative genes expression, confirming its beneficial effect in ulcer healing. Moreover, the possible PGE antioxidant potential was determined by in vitro assays using hydrogen peroxide and superoxide radical scavenging and revealed high antioxidant potential. Additionally, on the putatively annotated metabolites, an in silico study was conducted, which emphasized the extract’s antiulcer properties might be attributed to several sterols such as stigmasterol and campesterol. The present study provided evidence of Psidium guajava seeds considered as a potential natural gastroprotective agent.

Plant Antimicrobial Peptides as Potential Tool for Topic Treatment of Hidradenitis Suppurativa

Among chronic skin autoinflammatory diseases, Hidradenitis Suppurativa (HS) stands out for its chronicity, highly variable condition, and profound impact on the patients' quality of life. HS is characterized by suppurative skin lesions in diverse body areas, including deep-seated painful nodules, abscesses, draining sinus, and bridged scars, among others, with typical topography. To date, HS is considered a refractory disease and medical treatments aim to reduce the incidence, the infection, and the pain of the lesions. For this purpose, different classes of drugs, including anti-inflammatory molecules, antibiotics and biological drugs are being used. Antimicrobial peptides (AMPs), also called defense peptides, emerge as a new class of therapeutic compounds, with broad-spectrum antimicrobial action, in addition to reports on their anti-inflammatory, healing, and immunomodulating activity. Such peptides are present in prokaryotes and eukaryotes, as part of the innate eukaryotic immune system. It has been proposed that a deregulation in the expression of AMPs in human epithelial tissues of HS patients may be associated with the etiology of this skin disease. In this scenario, plant AMPs stand out for their richness, diversity of types, and broad antimicrobial effects, with potential application for topical systemic use in patients affected by HS.

Antifungal Peptides and Proteins to Control Toxigenic Fungi and Mycotoxin Biosynthesis

The global challenge to prevent fungal spoilage and mycotoxin contamination on food and feed requires the development of new antifungal strategies. Antimicrobial peptides and proteins (AMPs) with antifungal activity are gaining much interest as natural antifungal compounds due to their properties such as structure diversity and function, antifungal spectrum, mechanism of action, high stability and the availability of biotechnological production methods. Given their multistep mode of action, the development of fungal resistance to AMPs is presumed to be slow or delayed compared to conventional fungicides. Interestingly, AMPs also accomplish important biological functions other than antifungal activity, including anti-mycotoxin biosynthesis activity, which opens novel aspects for their future use in agriculture and food industry to fight mycotoxin contamination. AMPs can reach intracellular targets and exert their activity by mechanisms other than membrane permeabilization. The mechanisms through which AMPs affect mycotoxin production are varied and complex, ranging from oxidative stress to specific inhibition of enzymatic components of mycotoxin biosynthetic pathways. This review presents natural and synthetic antifungal AMPs from different origins which are effective against mycotoxin-producing fungi, and aims at summarizing current knowledge concerning their additional effects on mycotoxin biosynthesis. Antifungal AMPs properties and mechanisms of action are also discussed.

Isolation and functionalities of bioactive peptides from fruits and vegetables: A reviews

Bioactive peptides have recently gained more research attention as potential therapies for the management of bodily disorders and metabolic syndromes of delicate health importance. On another note, there is a rising trend on a global scale for the consumption and adoption of fruit and vegetables for the fulfilment of dietary and health needs. Furthermore, fruits and vegetables are being more studied as base materials for the isolation of biologically functional components and accordingly, they have been investigated for their concomitant bioactive peptides. This review focuses on isolation and bio-functional properties of bioactive peptides from fruits and vegetables. This manuscript is potential in serving as a material collection for fundamental consultancy on peptides derived from fruits and vegetables, and further canvasses the necessitation for the use of these food materials as primal matter for such.

A nematode-derived, mitochondrial stress signaling-regulated peptide exhibits broad antibacterial activity

A dramatic rise of infections with antibiotic-resistant bacterial pathogens continues to challenge the healthcare field due to the lack of effective treatment regimes. As such, there is an urgent need to develop new antimicrobial agents that can combat these multidrug-resistant superbugs. Mitochondria are central regulators of metabolism and other cellular functions, including the regulation of innate immunity pathways involved in the defense against infection. The mitochondrial unfolded protein response (UPR^mt) is a stress-activated pathway that mitigates mitochondrial dysfunction through the regulation of genes that promote recovery of the organelle. In the model organism Caenorhabditis elegans, the UPR^mt also mediates an antibacterial defense program that combats pathogen infection, which promotes host survival. We sought to identify and characterize antimicrobial effectors that are regulated during the UPR^mt. From our search, we discovered that the antimicrobial peptide CNC-4 is upregulated during this stress response. CNC-4 belongs to the caenacin family of antimicrobial peptides, which are predominantly found in nematodes and are known to have anti-fungal properties. Here, we find that CNC-4 also possesses potent antimicrobial activity against a spectrum of bacterial species and report on its characterization.

Summary: The caenacin antimicrobial peptide CNC-4 is regulated by a mitochondrial recovery pathway and exhibits broad antibacterial activity.

Therapeutic Potential of Medicinal Plant Proteins: Present Status and Future Perspectives

Biologically active molecules obtained from plant sources, mostly including secondary metabolites, have been considered to be of immense value with respect to the treatment of various human diseases. However, some inevitable limitations associated with these secondary metabolites like high cytotoxicity, low bioavailability, poor absorption, low abundance, improper metabolism, etc., have forced the scientific community to explore medicinal plants for alternate biologically active molecules. In this context, therapeutically active proteins/peptides from medicinal plants have been promoted as a promising therapeutic intervention for various human diseases. A large number of proteins isolated from the medicinal plants have been shown to exhibit anti-microbial, anti-oxidant, anti-HIV, anticancerous, ribosome-inactivating and neuro-modulatory activities. Moreover, with advanced technological developments in the medicinal plant research, medicinal plant proteins such as Bowman-Birk protease inhibitor and Mistletoe Lectin-I are presently under clinical trials against prostate cancer, oral carcinomas and malignant melanoma. Despite these developments and proteins being potential drug candidates, to date, not a single systematic review article has documented the therapeutical potential of the available biologically active medicinal plant proteome. The present article was therefore designed to describe the current status of the therapeutically active medicinal plant proteins/peptides vis-à-vis their potential as future protein-based drugs for various human diseases. Future insights in this direction have also been highlighted.

The forgotten 2S albumin proteins: Importance, structure, and biotechnological application in agriculture and human health

2S albumin proteins are a group of important seed storage proteins (SSPs) essential to seeds at early and late developmental stages, by providing amino acids and other nutrients during germination and for seed defense. 2S albumins possess a well-conserved cysteine supporting the stability of temperature, pH, and proteolysis. The 3D structure rich in alpha-helices and positively charged is particularly suited for antibacterial and antifungal activity, which is presented by many 2S albumins. However, the hypervariable region present in 2S albumins induces allergenic reactions. Because of that, 2S albumins have never been recognized for their biotechnological potential. However, the development of servers used for the rational design of antimicrobial molecules has now brought a new application to 2S albumins, acting as a model to design antimicrobial molecules without the toxic or allergenic effects of 2S albumins. Therefore, this review is focused on discussing the importance of 2S albumins to seed development and defense and the biochemical, structural and functional properties of these proteins thought to play a role in their antimicrobial activity. Additionally, the application of 2S albumins to design synthetic antimicrobial peptides is discussed, potentially bringing new functions to these forgotten proteins.

The revitalization of antimicrobial peptides in the resistance era

The antibiotic resistance crisis is becoming incredibly thorny due to the indiscriminate employment of antibiotics in agriculture and aquaculture, such as growth promoters, and the emergence of bacteria that are capable of enduring antibiotic treatment in an endless stream. Hence, to reverse this situation, vigorous efforts should be made in the process of identifying other alternative strategies with a lower frequency of resistance. Antimicrobial peptides (AMPs), originated from host defense peptides, are generally produced by a variety of organisms as defensive weapons to protect the host from other pathogenic bacteria. The unique ability of AMPs to control bacterial infections, as well as low propensity to acquire resistance, provides the basis for it to become one of the promising antibacterial substances. Herein, we present new insights into the biological functions, structural properties, distinct mechanisms of action of AMPs and their resistance determinants. Besides, we separately discuss natural and synthetic AMPs, including their source, screening pathway and antibacterial activity. Lastly, challenges and perspectives to identify novel potent AMPs are highlighted, which will expand our understanding of the chemical space of antimicrobials and provide a pipeline for discovering the next-generation of AMPs.

Phytosterol, Lipid and Phenolic Composition, and Biological Activities of Guava Seed Oil

Plant seeds have been found to contain bioactive compounds that have potential nutraceutical benefits. Guava seeds (Psidium guajava) are by-products in the beverage and juice industry; however, they can be utilized for a variety of commercial purposes. This study was designed to analyze the phytochemicals of the n-hexane extract of guava seed oil (GSO), to study its free-radical scavenging activity, and to monitor the changes in serum lipids and fatty acid profiles in rats that were fed GSO. The GSO was analyzed for phytochemicals using chromatographic methods. It was also tested for free-radical scavenging activity in hepatoma and neuroblastoma cells, and analyzed in terms of serum lipids and fatty acids. GSO was found to contain phenolic compounds (e.g., chlorogenic acid and its derivatives) and phytosterols (e.g., stimasterol, β-sitosterol and campesterol), and exerted radical-scavenging activity in cell cultures in a concentration-dependent manner. Long-term consumption of GSO did not increase cholesterol and triglyceride levels in rat serum, but it tended to decrease serum fatty acid levels in a concentration-dependent manner. This is the first study to report on the lipid, phytosterol and phenolic compositions, antioxidant activity, and the hepato- and neuro-protection of hydrogen peroxide-induced oxidative stress levels in the GSO extract.

Screening & analysis of anionic peptides from Foeniculum vulgare Mill by mass spectroscopy

Fennel (Foeniculum vulgare Mill.) member from the family Umbelliferae (Apiaceae) and has been used in Saudi Arabia as an medicine as of the from the tradition. Our previous work with seed extracts of this plant generated DEAE-ion exchange purified proteins that exhibited antibacterial properties. The current study moves this work forward by using 2-D gel separation and MALDI TOF/TOF to identify proteins in this active extract. Fourteen protein spots were excised, digested, and identified. Several putative functions were identified, including: a copper-trans locating ATPase PAA1 chloroplastic-like isoform X1; a cytosolic enolase; a putative pentatricopeptide repeat-containing protein; an NADP-requiring isocitrate dehydrogenase; two proteins annotated as being encoded downstream from Son-like proteins; three probable nuclear proteins 5–1; and four predicted/ unidentified proteins. Future efforts will further characterize their relevant antimicrobial properties with the aim of cloning and high throughput synthesis of the antimicrobial element(s).

Discovery and identification of antimicrobial peptides in Sichuan pepper (Zanthoxylum bungeanum Maxim) seeds by peptidomics and bioinformatics

Antimicrobial peptides (AMPs) have generated growing attention because of the increasing bacterial resistance. However, the discovery and identification of AMPs have proven to be challenging due to the complex purification procedure associated with conventional methods. For the reasons given above, it is necessary to explore more efficient ways to obtain AMPs. We established a new method for discovery and identification of novel AMPs by proteomics and bioinformatics from Zanthoxylum bungeanum Maxim seeds protein hydrolysate directly. This process was initially achieved by employing ultra-performance liquid chromatography-electrospray ionization-mass spectrometry/mass (UPLC-ESI-MS/MS) spectrometry to identify peptides derived from Z. bungeanum Maxim seed protein hydrolysates. Three online servers were introduced to predict potential AMPs. Sixteen potential AMPs ranging from 1.5 to 2.7 kDa were predicted and chemically synthesized, one of which, designated NP-6, inhibited activity against all the tested strains according to antimicrobial assay. Time-killing assay indicated that NP-6 could quickly kill almost all the Escherichia coli within 180 min and Staphylococcus aureus at 360 min. Moreover, the simulation 3D structure of NP-6 was consisted of α-helix and random coil, and this was verified by circular dichroism (CD) spectra. At last, the scanning electron microscope (SEM) images of E. coli and S. aureus treated by NP-6 demonstrated that NP-6 had a significant effect on bacteria cell morphology. Our findings provide an efficient approach for discovery of AMPs, and Z. bungeanum Maxim seeds may be a nature resource to extract antimicrobial agents.

A structural perspective of plant antimicrobial peptides

Among the numerous strategies plants have developed to fend off enemy attack, antimicrobial peptides (AMPs) stand out as one of the most prominent defensive barriers that grant direct and durable resistance against a wide range of pests and pathogens. These small proteins are characterized by a compact structure and an overall positive charge. AMPs have an ancient origin and widespread occurrence in the plant kingdom but show an unusually high degree of variation in their amino acid sequences. Interestingly, there is a strikingly conserved topology among the plant AMP families, suggesting that the defensive properties of these peptides are not determined by their primary sequences but rather by their tridimensional structure. To explore and expand this idea, we here discuss the role of AMPs for plant defense from a structural perspective. We show how specific structural properties, such as length, charge, hydrophobicity, polar angle and conformation, are essential for plant AMPs to act as a chemical shield that hinders enemy attack. Knowledge on the topology of these peptides is facilitating the isolation, classification and even structural redesign of AMPs, thus allowing scientists to develop new peptides with multiple agronomical and pharmacological potential.

The role of antimicrobial peptides in plant immunity

Selective pressure imposed by millions of years of relentless biological attack has led to the development of an extraordinary array of defense strategies in plants. Among these, antimicrobial peptides (AMPs) stand out as one of the most prominent components of the plant immune system. These small and usually basic peptides are deployed as a generalist defense strategy that grants direct and durable resistance against biotic stress. Even though their name implies a function against microbes, the range of plant-associated organisms affected by these peptides is much broader. In this review, we highlight the advances in our understanding on the role of AMPs in plant immunity. We demonstrate that the capacity of plant AMPs to act against a large spectrum of enemies relies on their diverse mechanism of action and remarkable structural stability. The efficacy of AMPs as a defense strategy is evidenced by their widespread occurrence in the plant kingdom, an astonishing heterogeneity in host peptide composition, and the extent to which plant enemies have evolved effective counter-measures to evade AMP action. Plant AMPs are becoming an important topic of research due to their significance in allowing plants to thrive and for their enormous potential in agronomical and pharmaceutical fields.

Antimicrobial peptides from different plant sources: Isolation, characterisation, and purification

Antimicrobial peptides (AMPs), the self-defence products of organisms, are extensively distributed in plants. They can be classified into several groups, including thionins, defensins, snakins, lipid transfer proteins, glycine-rich proteins, cyclotides and hevein-type proteins. AMPs can be extracted and isolated from different plants and plant organs such as stems, roots, seeds, flowers and leaves. They perform various physiological defensive mechanisms to eliminate viruses, bacteria, fungi and parasites, and so could be used as therapeutic and preservative agents. Research on AMPs has sought to obtain more detailed and reliable information regarding the selection of suitable plant sources and the use of appropriate isolation and purification techniques, as well as examining the mode of action of these peptides. Well-established AMP purification techniques currently used include salt precipitation methods, absorption-desorption, a combination of ion-exchange and reversed-phase C18 solid phase extraction, reversed-phase high-performance liquid chromatography (RP-HPLC), and the sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) method. Beyond these traditional methods, this review aims to highlight new and different approaches to the selection, characterisation, isolation, purification, mode of action and bioactivity assessment of a range of AMPs collected from plant sources. The information gathered will be helpful in the search for novel AMPs distributed in the plant kingdom, as well as providing future directions for the further investigation of AMPs for possible use on humans.

Optimization of EnBase Fed-Batch Cultivation to Improve Soluble Fraction Ratio of α-Luffin Ribosome Inactivating Protein

Background

The increase of the protein expression via ribosomal manipulation is one of the suggested cellular mechanisms involved in EnBase fed-batch mode of cultivation. However, this system has not been implemented for cytotoxic proteins.

Objectives

Here, the expression pattern of α-Luffin, a ribosome inactivation protein (RIP) with an innate toxicity, was investigated in EnBase system and the effect of low temperature cultivation on the increase of α-Luffin solubility was determined.

Materials and Methods

The encoding cDNA for mature α-Luffin was synthesized and subcloned into pET28a plasmid under the control of T7 promoter. The E. coli expression yield in EnBase® Flo fed-batch system was compared with traditional batch mode at two temperatures: 25 °C and 30 °C. Sampling was performed at several time intervals and solubility of recombinant-protein was checked on SDS-PAGE in pellet and supernatant samples. The purification of recombinant protein was performed by Ni-NTA column.

Results

In fed-batch cultivation mode, the early incubation time was desirable at 30 °C whereas the maximum amount of soluble α-Luffin was achieved from the extended protein synthesis period (12 and 24h post induction) at 25 °C.

Conclusions

Our founding showed that EnBase had a greater efficacy in producing higher soluble protein ratios compared to batch cultivation growth rate, however for cytotoxic proteins, incubation temperature and time need to be optimized. Owing to the advantages of natural toxins from RIP family for producing anticancer immune-conjugates, well optimization of this protein expression is of importance regarding industrial aspects. The optimized condition proposed here is promising in terms of large scale soluble production of α-Luffin without the need for refolding.

In silico optimization of a guava antimicrobial peptide enables combinatorial exploration for peptide design

Plants are extensively used in traditional medicine, and several plant antimicrobial peptides have been described as potential alternatives to conventional antibiotics. However, after more than four decades of research no plant antimicrobial peptide is currently used for treating bacterial infections, due to their length, post-translational modifications or  high dose requirement for a therapeutic effect . Here we report the design of antimicrobial peptides derived from a guava glycine-rich peptide using a genetic algorithm. This approach yields guavanin peptides, arginine-rich α-helical peptides that possess an unusual hydrophobic counterpart mainly composed of tyrosine residues. Guavanin 2 is characterized as a prototype peptide in terms of structure and activity. Nuclear magnetic resonance analysis indicates that the peptide adopts an α-helical structure in hydrophobic environments. Guavanin 2 is bactericidal at low concentrations, causing membrane disruption and triggering hyperpolarization. This computational approach for the exploration of natural products could be used to design effective peptide antibiotics.

Antimicrobial peptides are considered promising alternatives to antibiotics. Here the authors developed a computational algorithm that starts with peptides naturally occurring in plants and optimizes this starting material to yield new variants which are highly distinct from the parent peptide.

Bioactive characteristics and optimization of tamarind seed protein hydrolysate for antioxidant-rich food formulations

Tamarind seed has been a source of valuable nutrients such as protein (contains high amount of many essential amino acids), essential fatty acids, and minerals which are recognized as additive to develop perfect balanced functional foods. The objective of present work was to optimize the process parameters for extraction and hydrolysis of protein from tamarind seeds. Papain-derived hydrolysates showed a maximum degree of hydrolysis (39.49%) and radical scavenging activity (42.92 ± 2.83%) at optimized conditions such as enzyme-to-substrate ratio (1:5), hydrolysis time (3 h), hydrolysis temperature (65 °C), and pH 6. From this study, papain hydrolysate can be considered as good source of natural antioxidants in developing food formulations.

Cloning and soluble expression of mature α-luffin from Luffa cylindrica in E. coli using SUMO fusion protein

α-Lufin, found in Luaf cylindrica seeds, is a type I ribosome inactivating proteins. Cytotoxic effects make it an appropriate candidate for the construction of immunotoxins and conjugates. Because of limited natural resources, recombinant technology is the best approach to achieve large-scale production of plant-based proteins. In the present study, α-lufin protein was expressed in E. coli and the effects of different temperature conditions, SUMO fusion tag, and cultivation strategies on total expression and solubility were investigated. Protein expression was evaluated at different intervals (0, 4, 6, 8, 24 h) postinduction. Our results showed that EnBase had higher eficiency than LB, and maximum solubility and total protein expression were achieved 24 h after induction at 30 °C and 25 °C, respectively. It was shown that SUMO tag is an effective strategy to improve protein solubility.

Antimicrobial Peptides from Fruits and Their Potential Use as Biotechnological Tools-A Review and Outlook

Bacterial resistance is a major threat to plant crops, animals and human health, and over the years this situation has increasingly spread worldwide. Due to their many bioactive compounds, plants are promising sources of antimicrobial compounds that can potentially be used in the treatment of infections caused by microorganisms. As well as stem, flowers and leaves, fruits have an efficient defense mechanism against pests and pathogens, besides presenting nutritional and functional properties due to their multifunctional molecules. Among such compounds, the antimicrobial peptides (AMPs) feature different antimicrobials that are capable of disrupting the microbial membrane and of acting in binding to intra-cytoplasmic targets of microorganisms. They are therefore capable of controlling or halting the growth of microorganisms. In summary, this review describes the major classes of AMPs found in fruits, their possible use as biotechnological tools and prospects for the pharmaceutical industry and agribusiness.

A 2S Albumin from the Seed Cake of Ricinus communis Inhibits Trypsin and Has Strong Antibacterial Activity against Human Pathogenic Bacteria

Hospital-acquired infections caused by antibiotic-resistant bacteria threaten the lives of many citizens all over the world. Discovery of new agents to hinder bacterial development would have a significant impact on the treatment of infections. Here, the purification and characterization of Rc-2S-Alb, a protein that belongs to the 2S albumin family, from Ricinus communis seed cake, are reported. Rc-2S-Alb was purified after protein extraction with Tris-HCl buffer, pH 7.5, fractionation by ammonium sulfate (50-75%), and chromatography on Phenyl-Sepharose and DEAE-Sepharose. Rc-2S-Alb, a 75 kDa peptide, displays trypsin inhibitory activity and has high in vitro antibacterial activity against Bacillus subtilis, Klebsiella pneumonia, and Pseudomonas aeruginosa, which are important human pathogenic bacteria. Atomic force microscopy studies indicated that Rc-2S-Alb disrupts the bacterial membrane with loss of the cytoplasm content and ultimately bacterial death. Therefore, Rc-2S-Alb is a powerful candidate for the development of an alternative drug that may help reduce hospital-acquired infections.

Immune Cell-Conditioned Media Suppress Prostate Cancer PC-3 Cell Growth Correlating With Decreased Proinflammatory/Anti-inflammatory Cytokine Ratios in the Media Using 5 Selected Crude Polysaccharides

Five different crude polysaccharides from guava seed (GSPS), bitter buckwheat (BBPS), common buckwheat (CBPS), red Formosa lambsquarters (RFLPS), and yellow Formosa lambsquarters (YFLPS) were isolated to treat human prostate cancer PC-3 cells via direct action or tumor immunotherapy. The splenocyte- and macrophage-conditioned media (SCM and MCM) were prepared using individual selected polysaccharides, and then SCM or MCM was further collected to treat PC-3 cells. The relationship between PC-3 cell growth and Th1/Th2 cytokines in SCM as well as proinflammatory/anti-inflammatory cytokine secretion profiles in MCM were delineated. The results showed that all 5 selected polysaccharides did not significantly inhibit PC-3 cell growth via direct action. However, SCM or MCM cultured in the absence or presence of 5 selected polysaccharides significantly (P < .05) inhibited PC-3 cell growth. MCM cultured with 5 polysaccharides dose dependently enhanced their inhibitory effects on the viabilities of PC-3 cells than those cultured without polysaccharides. There was a significant (P < .05) negative correlation between PC-3 cell viabilities and (interleukin [IL]-6 + tumor necrosis factor [TNF]-α)/IL-10 level ratios in the corresponding MCM, implying that macrophages suppress PC-3 cell growth through decreasing secretion ratios of proinflammatory/anti-inflammatory cytokines in a tumor microenvironment.

Antimicrobial Peptides from Plants

Plant antimicrobial peptides (AMPs) have evolved differently from AMPs from other life forms. They are generally rich in cysteine residues which form multiple disulfides. In turn, the disulfides cross-braced plant AMPs as cystine-rich peptides to confer them with extraordinary high chemical, thermal and proteolytic stability. The cystine-rich or commonly known as cysteine-rich peptides (CRPs) of plant AMPs are classified into families based on their sequence similarity, cysteine motifs that determine their distinctive disulfide bond patterns and tertiary structure fold. Cystine-rich plant AMP families include thionins, defensins, hevein-like peptides, knottin-type peptides (linear and cyclic), lipid transfer proteins, α-hairpinin and snakins family. In addition, there are AMPs which are rich in other amino acids. The ability of plant AMPs to organize into specific families with conserved structural folds that enable sequence variation of non-Cys residues encased in the same scaffold within a particular family to play multiple functions. Furthermore, the ability of plant AMPs to tolerate hypervariable sequences using a conserved scaffold provides diversity to recognize different targets by varying the sequence of the non-cysteine residues. These properties bode well for developing plant AMPs as potential therapeutics and for protection of crops through transgenic methods. This review provides an overview of the major families of plant AMPs, including their structures, functions, and putative mechanisms.

Chemical composition of biomass generated in the guava tree pruning

Psidium guajava L. (Myrtaceae) is a native plant of Central America and is now widely cultivated in many tropical regions of the world for the fruit production. In Mexico, in the guava orchards common practices to control fruit production are: water stress, defoliation and pruning. In this study, we report the chemical composition of the biomass (branches and leaves) generated in the pruning practices. The results ranged as follows: pH (4.98-5.88), soda solubility (39.01-70.49 %), ash (1.87-8.20 %); potassium and calcium were the major inorganic elements in ash. No heavy metals were detected in the studied samples; total solubility (15.21-46.60 %), Runkel lignin (17.77-35.26 %), holocellulose (26.56 -69.49 %), α-cellulose (15.53-35.36 %), hemicelluloses (11.02-34.12 %), tannins in aqueous extracts (3.81-9.06 %), and tannins in ethanolic extracts (3.42-15.24 %).

Influence of the protocol of fibroin extraction on the antibiotic activities of the constructed composites

The effect of the solvents for silk fibroin (SF) extraction on its antimicrobial activity was studied. Extraction protocols were performed using LiBr (SF_L) and Ajisawa’s reagent (CaCl₂:ethanol:H₂O) (SF_C). The morphological and structural characteristics of the extracted SF and their composites were assessed. Corresponding bactericidal activities against Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922) and Pseudomonas aeroginosa (ATCC 27853) were performed. The resulting solutions were either casted into films or individually incorporated into composites of silver nanoparticles (NS) embedded into chitosan fragments (Cs) through γ-irradiation. Films of SF, obtained by using the two solvents, as well as the final prepared composites of SF, NS and Cs were analyzed using XRD, FTIR, SEM, TEM and zeta potential at several pH values. The band gap values were calculated. The results proved that, although SF_C consumed shorter gelation time, yet SF_L exerted higher antibiotic activity against the tested microorganisms. Moreover, the final composites had the ability to significantly reduce the growth of these medically relevant bacteria and are, therefore, recommended as a novel natural antibacterial biomaterial for several biomedical applications.

Structural insights into Cn-AMP1, a short disulfide-free multifunctional peptide from green coconut water

Multifunctional and promiscuous antimicrobial peptides (AMPs) can be used as an efficient strategy to control pathogens. However, little is known about the structural properties of plant promiscuous AMPs without disulfide bonds. CD and NMR were used to elucidate the structure of the promiscuous peptide Cn-AMP1, a disulfide-free peptide isolated from green coconut water. Data here reported shows that peptide structure is transitory and could be different according to the micro-environment. In this regard, Cn-AMP1 showed a random coil in a water environment and an α-helical structure in the presence of SDS-d25 micelles. Moreover, deuterium exchange experiments showed that Gly4, Arg5 and Met9 residues are less accessible to solvent, suggesting that flexibility and cationic charges seem to be essential for Cn-AMP1 multiple activities.

Chemical synthesis, structure-activity relationship, and properties of shepherin I: a fungicidal peptide enriched in glycine-glycine-histidine motifs

Although glycine-rich antimicrobial peptides (AMPs) are found in animals and plants, very little has been reported on their chemistry, structure activity-relationship, and properties. We investigated those topics for Shepherin I (Shep I), a glycine-rich AMP with the unique amino acid sequence G(1)YGGHGGHGGHGGHGGHGGHGHGGGGHG(28). Shep I and analogues were synthesized by the solid-phase method at 60 °C using conventional heating. Purification followed by chemical characterization confirmed the products' identities and high purity. Amino acid analysis provided their peptide contents. All peptides were active against the clinically important Candida species, but ineffective against bacteria and mycelia fungi. Truncation of the N- or C-terminal portion reduced Shep I antifungal activity, the latter being more pronounced. Carboxyamidation of Shep I did not affect the activity against C. albicans or C. tropicalis, but increased activity against S. cerevisiae. Carboxyamidated analogues Shep I (3-28)a and Shep I (6-28)a were equipotent to Shep I and Shep Ia against Candida species. As with most cationic AMPs, all peptides had their activity significantly reduced in high-salt concentrations, a disadvantage that is defeated if 10 µM ZnCl2 is present. At 100 µM, the peptides were practically not hemolytic. Shep Ia also killed C. albicans MDM8 and ATCC 90028 cells. Fluo-Shep Ia, an analogue labeled with 5(6)-carboxyfluorescein, was rapidly internalized by C. albicans MDM8 cells, a salt-sensitive process dependent on metabolic energy and temperature. Altogether, such results shed light on the chemistry, structural requirements for activity, and other properties of candidacidal glycine-rich peptides. Furthermore, they show that Shep Ia may have strong potential for use in topical application.

Chemical composition, antioxidant activities and protein profiling of different parts of Allamanda cathartica

The phytochemical screening and protein profiling of Allamanda cathartica was performed. Biochemical analysis revealed that peroxidase (8730 ± 307 units/g), superoxide dismutase (181 ± 3.79 units/g), catalase (529 ± 28.9 units/g), protease (3598 ± 79.8 units/g), total phenolic contents (19,344 ± 657 μM/g), β-esterases (342 ± 46.5 units/g) and the total oxidant status were highest in the roots as compared to other plant parts. However, total soluble proteins (128 ± 1.54 mg/g), lycopene (5.70 ± 0.61 mg/g), chlorophyll a (161 ± 24.9 μg/g), total chlorophyll content (267 ± 34.3 μg/g) and total carotenoid content (12.4 ± 1.71 mg/g) were found to be highest in leaves. Moreover, total antioxidant capacity (5.43 ± 0.29 μM/g) detected by using ABTS method and α-esterase (714.580 ± 23.6 units/g) were highest in shoots. The protein profiling was performed using SDS-PAGE. In leaves, 13 peptides with molecular weight (M.wt.) from 27 to 168 kDa were detected while in shoots 10 peptides with M.wt. from 30 to 95 kDa were resolved. Similarly, in roots, 10 peptides of 30-880 kDa and in flower seven peptides of 30-88 kDa were detected.

Native and recombinant Pg-AMP1 show different antibacterial activity spectrum but similar folding behavior

Glycine-rich proteins (GRPs) derived from plants compose a family of proteins and peptides that share a glycine repeat domain and they can perform diverse functions. Two structural conformations have been proposed for GRPs: glycine loops arranged as a Velcro and an anti-parallel β-sheet with several β-strands. The antimicrobial peptide Pg-AMP1 is the only plant GRP with antibacterial activity reported so far and its structure remains unclear. Recently, its recombinant expression was reported, where the recombinant peptide had an additional methionine residue at the N-terminal and a histidine tag at the C-terminal (His6-tag). These changes seem to change the peptide's activity, generating a broader spectrum of antibacterial activity. In this report, through ab initio molecular modelling and molecular dynamics, it was observed that both native and recombinant peptide structures were composed of an N-terminal α-helix and a dynamic loop that represents two-thirds of the protein. In contrast to previous reports, it was observed that there is a tendency to adopt a globular fold instead of an extended one, which could be in both, glycine loops or anti-parallel β-sheet conformation. The recombinant peptide showed a slightly higher solvated potential energy compared to the native form, which could be related to the His6-tag exposition. In fact, the His6-tag could be mainly responsible for the broader spectrum of activity, but it does not seem to cause great structural changes. However, novel studies are needed for a better characterization of its pharmacological properties so that in the future novel drugs may be produced based on this peptide.

The use of versatile plant antimicrobial peptides in agribusiness and human health

Plant immune responses involve a wide diversity of physiological reactions that are induced by the recognition of pathogens, such as hypersensitive responses, cell wall modifications, and the synthesis of antimicrobial molecules including antimicrobial peptides (AMPs). These proteinaceous molecules have been widely studied, presenting peculiar characteristics such as conserved domains and a conserved disulfide bond pattern. Currently, many AMP classes with diverse modes of action are known, having been isolated from a large number of organisms. Plant AMPs comprise an interesting source of studies nowadays, and among these there are reports of different classes, including defensins, albumins, cyclotides, snakins and several others. These peptides have been widely used in works that pursue human disease control, including nosocomial infections, as well as for agricultural purposes. In this context, this review will focus on the relevance of the structural-function relations of AMPs derived from plants and their proper use in applications for human health and agribusiness.

The attack of the phytopathogens and the trumpet solo: Identification of a novel plant antifungal peptide with distinct fold and disulfide bond pattern

Phytopathogens cause economic losses in agribusiness. Plant-derived compounds have been proposed to overcome this problem, including the antimicrobial peptides (AMPs). This paper reports the identification of Ps-AFP1, a novel AMP isolated from the Pisum sativum radicle. Ps-AFP1 was purified and evaluated against phytopathogenic fungi, showing clear effectiveness. In silico analyses were performed, suggesting an unusual fold and disulfide bond pattern. A novel fold and a novel AMP class were here proposed, the αβ-trumpet fold and αβ-trumpet peptides, respectively. The name αβ-trumpet was created due to the peptide's fold, which resembles the musical instrument. The Ps-AFP1 mechanism of action was also proposed. Microscopic analyses revealed that Ps-AFP1 could affect the fungus during the hyphal elongation from spore germination. Furthermore, confocal microscopy performed with Ps-AFP1 labeled with FITC shows that the peptide was localized at high concentration along the fungal cell surface. Due to low cellular disruption rates, it seems that the main target is the fungal cell wall. The binding thermogram and isothermal titration, molecular dynamics and docking analyses were also performed, showing that Ps-AFP1 could bind to chitin producing a stable complex. Data here reported provided novel structural-functional insights into the αβ-trumpet peptide fold.