Teucrium polium phenylethanol and iridoid glycoside characterization and flavonoid inhibition of biofilm-forming Staphylococcus aureus

Bio-Active Compounds from Teucrium Plants Used in the Traditional Medicine of Kurdistan Region, Iraq

Herbal medicine is still widely practiced in the Kurdistan Region, Iraq, especially by people living in villages in mountainous regions. Seven taxa belonging to the genus Teucrium (family Lamiaceae) are commonly employed in the Kurdish traditional medicine, especially to treat jaundice, stomachache and abdominal problems. We report, in this paper, a comprehensive account about the chemical structures and bioactivities of most representative specialized metabolites isolated from these plants. These findings indicate that Teucrium plants used in the folk medicine of Iraqi Kurdistan are natural sources of specialized metabolites that are potentially beneficial to human health.

A review of the phytochemistry, ethnopharmacology and biological activities of Teucrium genus (Germander)

Teucrium L (Lamiaceae) is mainly distributed in the Mediterranean area. A comprehensive survey in the electronic databases (during 2000-2020 years) with keywords of 'Teucrium' and 'Germander' showed that chemical analyses are available for 27 species, with sesquiterpenoids, iridoids, di and triterpenoids, and phenolic compounds as identified structures. The neo-clerodane diterpenoids as potential chemotaxonomic markers were the main compounds of this genus. As a result, Italy and Turkey have good attempts at phytochemical analysis. The pharmacological activities of different species including antioxidant, cytotoxic activity, antidiabetic, antimicrobial, anti-inflammatory and anti-insect have been summarized. Teucrium polium and Teucrium chamaedrys mainly have been used in digestive problems and diabetes in traditional medicine. Evidence-based clinical trials are needed to confirm the therapeutic properties of this genus. As well to the popularity of Asian and Anatolian species as ingredients in contemporary medicines and products, further research is required in comparison to European species.

Target-based screening for natural products against Staphylococcus aureus biofilms

As a notorious food-borne pathogen, Staphylococcus aureus can readily cause diseases in humans via contaminated food. Biofilm formation on various surfaces can increase the capacity of viable S. aureus cells for self-protection due to the stubborn structure of the biofilm matrix. Increased disease risk and economic losses caused by biofilm contamination in the food industry necessitate the urgent development of effective strategies for the inhibition and removal of S. aureus biofilms. Natural products have been extensively used as important sources of "eco-friendly" antibiofilm agents to avoid the side effects of conventional strategies on human health and the environment. This review discusses biofilm formation of S. aureus in food industries and focuses on providing an overview of potential promising target-oriented natural products and their mechanisms of S. aureus biofilm inhibition or removal. Hoping to provide valuable information of attractive research targets or potential undeveloped targets to screen potent natural anti-biofilm agents in food industries.

2α-Hydroxyalantolactone from Pulicaria undulata: activity against multidrug-resistant tumor cells and modes of action

BACKGROUND

Sesquiterpene lactones having α-methylene-γ-lactone moiety are promising natural metabolites showing various biological activity. One of the major metabolites isolated from Pulicaria undulata, 2α-hydroxyalantolactone (PU-1), has not been investigated in detail yet. Multidrug resistance (MDR) represents a major obstacle for cancer chemotherapy and the capability of novel natural products to overcoming MDR is of great interest.

PURPOSE

Exploring the molecular modes of action for potent natural product metabolites.

METHODS

The resazurin reduction assay was employed to evaluate the cytotoxicity of PU-1 on sensitive and their corresponding drug-resistant cell lines (overexpressing P-glycoprotein, BCRP, ABCB5, ΔEGFR, or TP53 knockout). Gene expression profiling was performed by transcriptome-wide mRNA microarray in the human CCRF-CEM leukemic cells after treatment with PU-1. The top significantly up- or down-regulated genes were identified by Chipster program and analyzed using Ingenuity Pathway Analysis (IPA) software. Finally, flow cytometry and Western blotting were performed for cell cycle analyses and apoptosis detection.

RESULTS

The sesquiterpene lactone, PU-1, showed potent cytotoxicity towards the drug-sensitive and -resistant cell lines. Transcriptome-wide mRNA expression profiling and pathway analysis pointed to genes involved in DNA damage response and G2/M cell cycle arrest. G2/M arrest was verified by flow cytometry and further confirmed by the upregulation of p21 and downregulation of p-CDC25C expression in Western blotting. Moreover, the suggested DNA damage checkpoint regulation was confirmed by immunofluorescence and Western blotting by upregulation of pS345 Chk1, p-H3 and γ-H2AX. Furthermore, PU-1 inhibited PI3K/AKT pathway, which is involved in signaling DNA damage and G2/M arrest. Cells ultimately induced apoptosis upon PU-1 treatment.

CONCLUSIONS

PU-1 is a potent natural product inhibiting otherwise drug-resistant human tumor cell growth through DNA damage, G2/M cell cycle arrest and apoptosis.

Cytotoxic and chemotaxonomic study of isolated metabolites from Centaurea aegyptiaca

The aerial parts of Centaureaa egyptiaca afforded 10 secondary metabolites including four sesquiterpene lactones; chlorohyssopifolin A (centaurepensin) (1), rediolpidetriol (2), linichlorinA (3), and sinaicin (4), one monoterpene; loliolid (5), one phenolic: tyrosol (6), three lignans; arctigenin (7), matairesinol (8), and pinoresinol (9), and one steroid; ergosta‐5,22‐dien‐3‐ol (10). The cluster analysis of 32 Centaurea species revealed that C. aegyptiaca is closely related to C. repens and C. solstitialise. The isolated compounds (1–10) were screened against CCRF‐CEM‐leukemia, MDA‐MB‐231‐pcDNA3 breast cancer, and HCT116 (p53+/+) colon carcinoma cell lines. Compounds1 and 2 were the most potent compounds against both leukemia and breast carcinoma cell lines.

First total syntheses of two natural glycosides

Isosyringinoside (1) and 3-(O-β-_d-glucopyranosyl)-α-(O-β-_d-glucopyranosyl)-4-hydroxy phenylethanol (2), the natural bioactive compounds contained unique structures, were first totally synthesized using easily available materials in short convenient routes with overall yields of 20.2% and 27.0%, respectively. An efficient total synthesis of 1 was developed in six steps, which contained two key steps of highly regioselective glycosylation without any selective protection steps. The seven-step synthesis of 2 involved two steps of regioselective glycosylations using BF₃-O(C₂H₅)₂ and TMSOTf as catalysts, respectively.

HR-LCMS-Based Metabolite Profiling, Antioxidant, and Anticancer Properties of Teucrium polium L. Methanolic Extract: Computational and In Vitro Study

In this study, we investigate the phytochemical profile, anticancer, and antioxidant activities of Teucrium polium methanolic extract using both in vitro and in silico approaches. The results showed the identification of 29 phytochemical compounds belonging to 13 classes of compounds and 20 tripeptides using High Resolution-Liquid Chromatography Mass Spectrometry (HR-LCMS). 13R-hydroxy-9E,11Z octadecadienoic acid, dihydrosamidin, valtratum, and cepharantine were the main compounds identified. The tested extract showed promising antioxidant activities (ABTS-IC50 = 0.042 mg/mL; 1,1-diphenyl-2-picrylhydrazyl (DPPH)-IC50 = 0.087 mg/mL, β-carotene-IC50 = 0.101 mg/mL and FRAP-IC50 = 0.292 mg/mL). Using both malignant Walker 256/B and MatLyLu cell lines, T. polium methanolic extract showed a dose/time-dependent antitumor activity. The molecular docking approach revealed that most of the identified molecules were specifically binding with human peroxiredoxin 5, human androgen, and human progesterone receptors with high binding affinity scores. The obtained results confirmed that T. polium is a rich source of bioactive molecules with antioxidant and antitumor potential.

Plant Derived Natural Products against Pseudomonas aeruginosa and Staphylococcus aureus: Antibiofilm Activity and Molecular Mechanisms

Bacteria are social organisms able to build complex structures, such as biofilms, that are highly organized surface-associated communities of microorganisms, encased within a self- produced extracellular matrix. Biofilm is commonly associated with many health problems since its formation increases resistance to antibiotics and antimicrobial agents, as in the case of Pseudomonas aeruginosa and Staphylococcus aureus, two human pathogens causing major concern. P. aeruginosa is responsible for severe nosocomial infections, the most frequent of which is ventilator-associated pneumonia, while S. aureus causes several problems, like skin infections, septic arthritis, and endocarditis, to name just a few. Literature data suggest that natural products from plants, bacteria, fungi, and marine organisms have proven to be effective as anti-biofilm agents, inhibiting the formation of the polymer matrix, suppressing cell adhesion and attachment, and decreasing the virulence factors' production, thereby blocking the quorum sensing network. Here, we focus on plant derived chemicals, and provide an updated literature review on the anti-biofilm properties of terpenes, flavonoids, alkaloids, and phenolic compounds. Moreover, whenever information is available, we also report the mechanisms of action.

Phytotoxic and Antimicrobial Activities of Teucrium polium and Thymus decussatus Essential Oils Extracted Using Hydrodistillation and Microwave-Assisted Techniques

Essential oils (EOs) have been described as promising eco-friendly secondary products of aromatic plants with several biological activities. The present study aimed to characterize the chemical composition and explore phytotoxic and antimicrobial activities of Teucrium polium and Thymus decussatus EOs extracted using hydrodistillation (HD) and microwave-assisted extraction (MAE) methods. Twenty-seven and twenty-eight compounds were identified from HD and MAE extracted EOs of T. polium, respectively. The oxygenated sesquiterpenes (57.68%) were characterized as the main components of the hydrodistilled EO with a prominence of 6-epi-shyobunol (33.00%), while sesquiterpene hydrocarbons (54.48%) were the main components of the MAE method, with a prominence of delta-cadinene (25.13%). Eighteen and nineteen compounds, were characterized in T. decussatus EOs extracted using HD and MAE methods, respectively, and oxygenated monoterpenes represented the main components of both EOs with carvacrol (94.40% and 75.91%, respectively) as the main compound. The EOs extracted using the MAE method were slightly more phytotoxic than those extracted using the HD method. The T. decussatus EO extracted using the MAE method showed a higher inhibitory effect than T. polium by 16-, 32-, and 24-fold, regarding seed germination, shoot, and root growth of lettuce, respectively. Moreover, EOs extracted by HD method showed a similar pattern with 16-, 28-, and 14-fold effects. Both T. decussatus EOs exhibited potent inhibitory effect against all tested bacteria with an inhibition zone of 34–39 mm and the lowest minimum inhibitory concentration (MIC) of 0.49, 0.98, and 1.95 μg/mL against Aspergillus niger, Escherichia coli, and Staphylococcus aureus, respectively. However, the EOs of T. polium showed weak antibacterial activity and no antifungal effect. Further studies are needed for the characterization of bioactive major compounds, either singular or synergistic, at field scale and to determine their modes of action and safety.

Vasodilatory effect and structural-activity relationship of a group of iridoid glucosides from Phlomis likiangensis

As a folk medicine, Phlomis likiangensis is traditionally used in China to activate collaterals and protect cardiovascular system. We hypothesized that the beneficial effects of Phlomis likiangensis may be related to vasodilatation. In the present study, twelve known iridoid glucosides (1-12) were isolated from Phlomis likiangensis. The vasodilatory effects and the underlying mechanisms of the main components (iridoid glucosides) of Phlomis likiangensis on rat aortic rings were investigated. The result showed that iridoid glucosides significantly increased the vasodilatation in rat aortic rings, which was abolished by removing the endothelium of the vessels or by eliminating the generation of nitric oxide. Finally, the structure-activity relationship of compounds 1-12 was also speculated. Our findings provide the first evidence that the iridoid glucosides of Phlomis likiangensis may be the pharmacodynamic basis for its traditional efficacy.

Cytotoxicity of 40 Egyptian plant extracts targeting mechanisms of drug-resistant cancer cells

BACKGROUND

The multidrug resistance (MDR) phenotype encounters a major challenge to the success of established chemotherapy in cancer patients. We hypothesized that cytotoxic medicinal plants with novel phytochemicals can overcome MDR and kill MDR-cells with similar efficacy as drug sensitive cells.

PURPOSE

We evaluated plant extracts from an unexplored ecosystem in Egypt with unusual climate and nutrient conditions for their activity against sensitive and multidrug-resistant cancer cell lines.

MATERIAL AND METHODS/STUDY DESIGN

Methylene chloride: methanol (1:1) and methanol: H₂O (7:3) extracts of 40 plants were prepared resulting in a sum of 76 fraction containing compounds with varying polarity. The resazurin reduction assay was employed to evaluate the cytotoxicity of these extracts on five matched pairs of drug-sensitive and their drug-resistant cell lines. Flow cytometry and Western blotting was used to determine cell cycle analyses, apoptosis, and autophagy. Reactive oxygen species (ROS) were measured spectrophotometrically.

RESULTS

Extracts derived from Withania obtusifolia (WO), Jasonia candicans (JC), Centaurea lippii (CL), and Pulicaria undulata (PU) were the most active ones among 76 extracts from 40 Egyptian medicinal plants. They showed a significant reduction of cell viability on drug-sensitive CCRF-CEM leukemia cell line with IC₅₀ values less than 7 µg/ml. Low cross-resistance degrees were observed in multidrug-resistant CEM/ADR5000 cells towards CL (1.82-fold) and JC (6.09-fold). All other drug-resistant cell lines did not reveal cross-resistance to the four extracts. Further mechanistic assessment have been studied for these four extracts.

CONCLUSION

The methylene chloride: methanol (1:1) fractions of WO, JC, CL, and PU are promising cytotoxic extracts that could be used to combat MDR cancer cells through different cell death pathways.

Euphosantianane A⁻D: Antiproliferative Premyrsinane Diterpenoids from the Endemic Egyptian Plant Euphorbia Sanctae-Catharinae

Euphorbia species are rich in diterpenes. A solvent extraction of Euphorbia sanctae-catharinae, a species indigenous to the Southern Sinai of Egypt, afforded several premyrsinane diterpenoids (1⁻4) as well as previously reported metabolites (5⁻13) that included three flavonoids. Isolated compounds were chemically characterized by spectroscopic analysis. Identified compounds were bioassayed for anti-proliferative activity in vitro against colon (Caco-2) and lung (A549) tumor cell lines. Compound 9 exhibited robust anti-proliferative activity against A549 cells (IC50 = 3.3 µM). Absolute configurations for 8 versus 9 were determined by experimental and TDDFT-calculated electronic circular dichorism (ECD) spectra.

Antihyperlipidemic Effect of Different Fractions Obtained from Teucrium polium Hydroalcoholic Extract in Rats

Background:

This study was aimed to screen the antihyperlipidemic effect of different fractions of Teucrium polium to obtain the most efficient herbal fraction for isolation of bioactive constituents responsible for hypolipidemic activity.

Methods:

Chloroform, butanol, and aqueous fractions were obtained from hydroalcoholic extract of T. polium aerial parts using partitioning process. To induce hyperlipidemia, dexamethasone (Dex) was injected 10 mg/kg/day (s.c.) for 8 days. In the test groups, animals received 50, 100 and 150 mg/kg of T. polium hydroalcoholic extract and different fractions orally simultaneously with Dex. Serum lipid profile and hepatic marker enzymes were evaluated using biochemical kits.

Results:

All treatments, especially chloroform and aqueous fractions, reversed serum lipid markers in hyperlipidemic rats. Maximum reduction in triglyceride (60.2%, P < 0.001) and maximum elevation in high-density lipoprotein (HDL) (35.0%, P < 0.01) was observed for chloroform fraction. Maximum cholesterol-lowering effect (29.0%, P < 0.001) and maximum reduction in low-density lipoprotein were found for hydroalcoholic extract (72.9%, P < 0.001). Aqueous fraction improved all lipid markers at the highest dose. Butanol fraction decreased triglyceride at the lowest dose (43.9%, P < 0.001) and increased HDL (33%, P < 0.05) at the highest dose. There was a significant increase in alanine aminotransferase and aspartate aminotransferase levels in all tested groups compared to normal group (P < 0.001).

Conclusions:

This study showed strong antihyperlipidemic effect of various fractions derived from hydroalcoholic extract of T. polium. Chloroform and aqueous fractions may be worthy candidates for isolation of bioactive hypolipidemic constituents. However, possible hepatotoxicity should be considered for clinical application.

Multitargeted Flavonoid Inhibition of the Pathogenic Bacterium Staphylococcus aureus: A Proteomic Characterization

Growth inhibition of the pathogen Staphylococcus aureus with currently available antibiotics is problematic in part due to bacterial biofilm protection. Although recently characterized natural products, including 3',4',5-trihydroxy-6,7-dimethoxy-flavone [1], 3',4',5,6,7-pentahydroxy-flavone [2], and 5-hydroxy-4',7-dimethoxy-flavone [3], exhibit both antibiotic and biofilm inhibitory activities, the mode of action of such hydroxylated flavonoids with respect to S. aureus inhibition is yet to be characterized. Enzymatic digestion and high-resolution MS analysis of differentially expressed proteins from S. aureus with and without exposure to antibiotic flavonoids (1-3) allowed for the characterization of global protein alterations induced by metabolite treatment. A total of 56, 92, and 110 proteins were differentially expressed with bacterial exposure to 1, 2, or 3, respectively. The connectivity of the identified proteins was characterized using a search tool for the retrieval of interacting genes/proteins (STRING) with multitargeted S. aureus inhibition of energy metabolism and biosynthesis by the assayed flavonoids. Identifying the mode of action of natural products as antibacterial agents is expected to provide insight into the potential use of flavonoids alone or in combination with known therapeutic agents to effectively control S. aureus infection.

Iridoid glycoside permethylation enhances chromatographic separation and chemical ionization

RATIONALE

While natural products isolated from medicinal plants can serve as a rich source of biologically active metabolites, mixtures of structurally related compounds of a polar nature are often difficult to chemically resolve by traditional separation techniques. Chemical derivatization to reduce metabolite polarity combined with liquid chromatography (LC) is the strategy presented here to resolve a mixture of structurally related natural product glycosides solvent extracted from the medicinal herb Teucrium polium for mass spectrometric characterization.

METHODS

The partially purified plant extract was subjected to chemical derivatization and electrospray ionization mass spectrometry (ESI-MS) fragmentation pattern analysis allowed for structural characterization of iridoid and secoiridoid glycosides. Selected ions were subjected to tandem mass spectrometric (MS/MS) analysis with a relatively higher-energy collision dissociation to assist in structural elucidation.

RESULTS

Permethylation replaced all protons from free hydroxyl and amino groups with methyls and resulted in increases in both hydrophobicity, for facilitated chromatographic separation, and proton affinity, for enhanced chemical ionization. Protonated and/or sodiated adducts were observed for the six compounds detected in positive-ion mode ESI-MS with a mass accuracy of less than 2 ppm.

CONCLUSIONS

Permethylation combined with LC/MS analysis is shown here to be an effective chemical practice for separating and characterizing iridoid glucosinolates and is expected to be well suited for the chemical characterization of other polar natural-product mixtures of closely related compounds. Copyright © 2016 John Wiley & Sons, Ltd.

Plant Natural Products Targeting Bacterial Virulence Factors

Decreased antimicrobial efficiency has become a global public health issue. The paucity of new antibacterial drugs is evident, and the arsenal against infectious diseases needs to be improved urgently. The selection of plants as a source of prototype compounds is appropriate, since plant species naturally produce a wide range of secondary metabolites that act as a chemical line of defense against microorganisms in the environment. Although traditional approaches to combat microbial infections remain effective, targeting microbial virulence rather than survival seems to be an exciting strategy, since the modulation of virulence factors might lead to a milder evolutionary pressure for the development of resistance. Additionally, anti-infective chemotherapies may be successfully achieved by combining antivirulence and conventional antimicrobials, extending the lifespan of these drugs. This review presents an updated discussion of natural compounds isolated from plants with chemically characterized structures and activity against the major bacterial virulence factors: quorum sensing, bacterial biofilms, bacterial motility, bacterial toxins, bacterial pigments, bacterial enzymes, and bacterial surfactants. Moreover, a critical analysis of the most promising virulence factors is presented, highlighting their potential as targets to attenuate bacterial virulence. The ongoing progress in the field of antivirulence therapy may therefore help to translate this promising concept into real intervention strategies in clinical areas.

Cytotoxic saponin poliusaposide from Teucrium polium

Three saponin glycosides have been isolated and characterized from Teucrium polium L. (Lamiaceae).