Nigellothionins from Black Cumin (Nigella sativa L.) Seeds Demonstrate Strong Antifungal and Cytotoxic Activity

Antimicrobial Properties and Therapeutic Potential of Bioactive Compounds in Nigella sativa: A Review

Nigella sativa (N. sativa; Ranunculaceae), commonly referred to as black cumin, is one of the most widely used medicinal plants worldwide, with its seeds having numerous applications in the pharmaceutical and food industries. With the emergence of antibiotic resistance in pathogens as an important health challenge, the need for alternative microbe-inhibitory agents is on the rise, whereby black cumin has gained considerable attention from researchers for its strong antimicrobial characteristics owing to its high content in a wide range of bioactive compounds, including thymoquinone, nigellimine, nigellidine, quercetin, and O-cymene. Particularly, thymoquinone increases the levels of antioxidant enzymes that counter oxidative stress in the liver. Additionally, the essential oil in N. sativa seeds effectively inhibits intestinal parasites and shows moderate activity against some bacteria, including Bacillus subtilis and Staphylococcus aureus. Thymoquinone exhibits minimum inhibitory concentrations (MICs) of 8-16 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA) and exhibits MIC 0.25 µg/mL against drug-resistant mycobacteria. Similarly, quercetin shows a MIC of 2 mg/mL against oral pathogens, such as Streptococcus mutans and Lactobacillus acidophilus. Furthermore, endophytic fungi isolated from N. sativa have demonstrated antibacterial activity. Therefore, N. sativa is a valuable medicinal plant with potential for medicinal and food-related applications. In-depth exploration of the corresponding therapeutic potential and scope of industrial application warrants further research.

Plant-Derived Antimicrobials and Their Crucial Role in Combating Antimicrobial Resistance

Antibiotic resistance emerged shortly after the discovery of the first antibiotic and has remained a critical public health issue ever since. Managing antibiotic resistance in clinical settings continues to be challenging, particularly with the rise of superbugs, or bacteria resistant to multiple antibiotics, known as multidrug-resistant (MDR) bacteria. This rapid development of resistance has compelled researchers to continuously seek new antimicrobial agents to curb resistance, despite a shrinking pipeline of new drugs. Recently, the focus of antimicrobial discovery has shifted to plants, fungi, lichens, endophytes, and various marine sources, such as seaweeds, corals, and other microorganisms, due to their promising properties. For this review, an extensive search was conducted across multiple scientific databases, including PubMed, Elsevier, ResearchGate, Scopus, and Google Scholar, encompassing publications from 1929 to 2024. This review provides a concise overview of the mechanisms employed by bacteria to develop antibiotic resistance, followed by an in-depth exploration of plant secondary metabolites as a potential solution to MDR pathogens. In recent years, the interest in plant-based medicines has surged, driven by their advantageous properties. However, additional research is essential to fully understand the mechanisms of action and verify the safety of antimicrobial phytochemicals. Future prospects for enhancing the use of plant secondary metabolites in combating antibiotic-resistant pathogens will also be discussed.

New Insights into Involvement of Low Molecular Weight Proteins in Complex Defense Mechanisms in Higher Plants

Dynamic climate changes pose a significant challenge for plants to cope with numerous abiotic and biotic stressors of increasing intensity. Plants have evolved a variety of biochemical and molecular defense mechanisms involved in overcoming stressful conditions. Under environmental stress, plants generate elevated amounts of reactive oxygen species (ROS) and, subsequently, modulate the activity of the antioxidative enzymes. In addition, an increase in the biosynthesis of important plant compounds such as anthocyanins, lignin, isoflavonoids, as well as a wide range of low molecular weight stress-related proteins (e.g., dehydrins, cyclotides, heat shock proteins and pathogenesis-related proteins), was evidenced. The induced expression of these proteins improves the survival rate of plants under unfavorable environmental stimuli and enhances their adaptation to sequentially interacting stressors. Importantly, the plant defense proteins may also have potential for use in medical applications and agriculture (e.g., biopesticides). Therefore, it is important to gain a more thorough understanding of the complex biological functions of the plant defense proteins. It will help to devise new cultivation strategies, including the development of genotypes characterized by better adaptations to adverse environmental conditions. The review presents the latest research findings on selected plant defense proteins.

A review on the diversity of antimicrobial peptides and genome mining strategies for their prediction

Antibiotic resistance has become one of the most serious threats to human health in recent years. In response to the increasing microbial resistance to the antibiotics currently available, it is imperative to develop new antibiotics or explore new approaches to combat antibiotic resistance. Antimicrobial peptides (AMPs) have shown considerable promise in this regard, as the microbes develop low or no resistance against them. The discovery and development of AMPs still confront numerous obstacles such as finding a target, developing assays, and identifying hits and leads, which are time-consuming processes, making it difficult to reach the market. However, with the advent of genome mining, new antibiotics could be discovered efficiently using tools such as BAGEL, antiSMASH, RODEO, etc., providing hope for better treatment of diseases in the future. Computational methods used in genome mining automatically detect and annotate biosynthetic gene clusters in genomic data, making it a useful tool in natural product discovery. This review aims to shed light on the history, diversity, and mechanisms of action of AMPs and the data on new AMPs identified by traditional as well as genome mining strategies. It further substantiates the various phases of clinical trials for some AMPs, as well as an overview of genome mining databases and tools built expressly for AMP discovery. In light of the recent advancements, it is evident that targeted genome mining stands as a beacon of hope, offering immense potential to expedite the discovery of novel antimicrobials.

In Vitro Assessment of Anti-Adipogenic and Anti-Inflammatory Properties of Black Cumin (Nigella sativa L.) Seeds Extract on 3T3-L1 Adipocytes and Raw264.7 Macrophages

Background and Objectives: This study evaluated the in vitro anti-adipogenic and anti-inflammatory properties of black cumin (Nigella sativa L.) seed extract (BCS extract) as a potential candidate for developing herbal formulations targeting metabolic disorders. Materials and Methods: We evaluated the BCS extract by assessing its 2,2-diphenyl-1-picrohydrazyl (DPPH) radical scavenging activity, levels of prostaglandin E2 (PGE2) and nitric oxide (NO), and mRNA expression levels of key pro-inflammatory mediators. We also quantified the phosphorylation of nuclear factor kappa light chain enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPK) signaling molecules. To assess anti-adipogenic effects, we used differentiated 3T3-L1 cells and BCS extract in doses from 10 to 100 μg/mL. We also determined mRNA levels of key adipogenic genes, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/BEPα), adipocyte protein 2 (aP2), lipoprotein lipase (LPL), fatty acid synthase (FAS), and sterol-regulated element-binding protein 1c (SREBP-1c) using real-time quantitative polymerase chain reaction (qPCR). Results: This study showed a concentration-dependent DPPH radical scavenging activity and no toxicity at concentrations up to 30 μg/mL in Raw264.7 cells. BCS extract showed an IC50 of 328.77 ± 20.52 μg/mL. Notably, pre-treatment with BCS extract (30 μg/mL) significantly enhanced cell viability in lipopolysaccharide (LPS)-treated Raw264.7 cells. BCS extract treatment effectively inhibited LPS-induced production of PGE2 and NO, as well as the expression of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS), interleukin (IL)-1β and IL-6, possibly by limiting the phosphorylation of p38, p65, inhibitory κBα (I-κBα), and c-Jun N-terminal kinase (JNK). It also significantly attenuated lipid accumulation and key adipogenic genes in 3T3-L1 cells. Conclusions: This study highlights the in vitro anti-adipogenic and anti-inflammatory potential of BCS extract, underscoring its potential as a promising candidate for managing metabolic disorders.

Recombinant Fusion Protein Containing Plant Nigellothionin Regulates the Growth of Food-Spoiling Fungus (Aspergillus niger)

This study aimed to obtain a recombinant chimeric protein named trx-NsW2 via theheterologous expression of the multifunctional antimicrobial peptide nigellothionin from black cumin (Nigella sativa L.) seeds in the Escherichia coli system. The protein was purified using a combination of Ni-NTA affinity chromatography and reversed-phase HPLC. Based on the HPLC calibration, the total yield of the protein was calculated to be 650 mg/L of bacterial culture. The fungistatic activity of trx-NsW2 against the food-spoiling fungus Aspergillus niger was demonstrated as itinhibited the maturation of conidiawithout affecting conidial germination or fungal growth. In contrast to mature nigellothionin NsW2, the fusion protein showeda low level of cytotoxicity towards both normal and tumor cell lines at concentrationsof up to 100-200 µM. Interestingly, at lower concentrations, it even stimulated cytokinesis. These findings are of critical importance for applying chimeric antimicrobial proteins obtained via microbiological synthesis in applied science.

Diversity of Cationic Antimicrobial Peptides in Black Cumin (Nigella sativa L.) Seeds

Black cumin (Nigella sativa L.) is known to possess a wide variety of antimicrobial peptides belonging to different structural families. Three novel antimicrobial peptides have been isolated from black cumin seeds. Two of them were attributed as members of the non-specific lipid transfer proteins family, and one as a defensin. We have made an attempt of using the proteomic approach for novel antimicrobial peptides search in N. sativa seeds as well. The use of a well-established approach that includes extraction and fractionation stages remains relevant even in the case of novel peptides search because of the lacking N. sativa genome data. Novel peptides demonstrate a spectrum of antimicrobial activity against plant pathogenic organisms that may cause economically important crop diseases. These results obtained allow considering these molecules as candidates to be applied in "next-generation" biopesticides development for agricultural use.

Efficacy Confirmation Test of Black Cumin (Nigella sativa L.) Seeds Extract Using a High-Fat Diet Mouse Model

To deal with the adverse effects associated with the use of currently available treatments for metabolic disorders, such as type 2 diabetes, there is a need to find an alternative drug compound. In the present study, we investigated the therapeutic potential of black cumin (Nigella sativa L.) seeds extract (BCS extract) for type 2 diabetes using a 45% Kcal-fed obese mouse model. The BCS extract at different doses (400–100 mg/kg) showed a dose-dependent improvement tendency in high-fat diet (HFD)-induced obesity, non-alcoholic fatty liver disease (NAFLD), hyperlipidemia, and diabetic nephropathy compared to the metformin (250 mg/kg). In particular, BCS extract at a dose of 200 mg/kg significantly inhibited the HFD-induced metabolic conditions. The oral administration of BCS extract (200 mg/kg) significantly inhibited the oxidative stress through lipid peroxidation, normalized the activity of sugar metabolism-related enzymes and the expression of genes involved in fat metabolism, and inhibited insulin resistance through glucose and fat metabolism by regulating the 5’-AMP-activated protein kinase (AMPK) expression. Furthermore, BCS extract (200 mg/kg) showed renal damage improvement effects compared to the metformin (250 mg/kg). The results clearly show that BCS aqueous extract at an appropriate concentration could help in the treatment of metabolic disorders, and BCS aqueous extract can be used as a functional food for various diabetic complications, such as obesity, diabetes, and NAFLD.

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.

Fast killing kinetics, significant therapeutic index, and high stability of melittin-derived antimicrobial peptide

The emergence of multidrug-resistant (MDR) bacteria is a major challenge for antimicrobial chemotherapy. Concerning this issue, antimicrobial peptides (AMPs) have been presented as novel promising antibiotics. Our previous de novo designed melittin-derived peptides (MDP1 and MDP2) indicated their potential as peptide drug leads. Accordingly, this study was aimed to evaluate the kinetics of activity, toxicity, and stability of MDP1 and MDP2 as well as determination of their structures. The killing kinetics of MDP1 and MDP2 demonstrate that all bacterial strains were rapidly killed. MDP1 and MDP2 were ca. 100- and 26.6-fold less hemolytic than melittin and found to be respectively 72.9- and 41.6-fold less cytotoxic than melittin on the HEK293 cell line. MDP1 and MDP2 showed 252- and 132-fold improvement in their therapeutic index in comparison to melittin. MDP1 and MDP2 sustained their activities in the presence of human plasma and were found to be ca. four to eightfold more stable than melittin. Spectropolarimetry analysis of MDP1 and MDP2 indicates that the peptides adopt an alpha-helical structure predominantly. According to the fast killing kinetics, significant therapeutic index, and high stability of MDP1, it could be considered as a drug lead in a mouse model of septicemia infections.

Immunomodulatory peptides-A promising source for novel functional food production and drug discovery

Immunomodulatory peptides are a complex class of bioactive peptides that encompasses substances with different mechanisms of action. Immunomodulatory peptides could also be used in vaccines as adjuvants which would be extremely desirable, especially in response to pandemics. Thus, immunomodulatory peptides in food of plant origin could be regarded both as valuable suplements of novel functional food preparation and/or as precursors or possible active ingredients for drugs design for treatment variety of conditions arising from impaired function of immune system. Given variety of mechanisms, different tests are required to assess effects of immunomodulatory peptides. Some of those effects show good correlation with in vivo results but others, less so. Certain plant peptides, such as defensins, show both immunomodulatory and antimicrobial effect, which makes them interesting candidates for preparation of functional food and feed, as well as templates for design of synthetic peptides.

Nigella sativa L. Phytochemistry and Pharmacological Activities: A Review (2019-2021)

Medicinal and aromatic plants are mainly characterized by the presence of different bioactive compounds which exhibit various therapeutic activities. In order to investigate the different pharmacological properties of different Nigella sativa extracts, a multitude of research articles published in the period between 2019 and 2021 were obtained from different databases (Scopus, Science Direct, PubMed, and Web of Science), and then explored and analyzed. The analysis of the collected articles allows us to classify the phytochemicals and the pharmacological activities through their underlying molecular mechanisms, as well as to explore the pharmacological activities exhibited by several identified compounds in Nigella sativa which allow a better understanding, and better elucidation, of the bioactive compounds responsible for the pharmacological effects. Also shown are the existence of other bioactive compounds that are still unexplored and could be of great interest. This review could be taken as a guide for future studies in the field.