Chemical Constituents of Stinging Nettle (Urtica dioica L.): A Comprehensive Review on Phenolic and Polyphenolic Compounds and Their Bioactivity.

Polyphenolic compounds are of great interest in today's science. Naturally, they occur in plants and other sources in many different forms. Their wide range of biological activity has attracted the attention of the scientific community. One of the sources of phenolic compounds is stinging nettle (Urtica dioica L.), a common plant in almost all parts of the world. A long tradition of utilization and an interesting chemical profile make this plant a fascinating and extensive object of study. The chemical profile also allows this plant to be used as a food and a pigment source in the food, pharmaceutical, and cosmetic industries. Previously conducted studies found phenolic acids and polyphenolic compounds in root, stalk, and stinging nettle leaves. Different extraction techniques were usually used to isolate them from the leaves. Obtained extracts were used to investigate biological activity further or formulate different functional food products. This study aimed to collect all available knowledge about this plant, its chemical composition, and biological activity and to summarize this knowledge with particular attention to polyphenolic compounds and the activity and mechanisms of their actions.

Recovery of Polyphenolic Compounds and Vitamins from the Stinging Nettle Leaves: Thermal and Behavior and Biological Activity of Obtained Extracts.

Stinging nettle (SN) is an extraordinary plant from the Urticaceae botanical family. It is well-known and widely used in food and folk medicine to treat different disorders and diseases. This article aimed to study the chemical composition of SN leaves extracts, i.e., polyphenolic compounds and vitamins B and C, because many studies ascribed high biological potency to these compounds and their significance in the human diet. Besides the chemical profile, the thermal properties of the extracts were studied. The results confirmed presence of many polyphenolic compounds and vitamins B and C. It also showed that the chemical profile closely correlated with the applied extraction technique. The thermal analysis showed that analyzed samples were thermally stable up to about 160 °C. Thermal degradation of samples UAE, MAE, and MAC took place in four steps, and sample SE in three steps. Altogether, results confirmed the presence of health-beneficial compounds in stinging nettle leaves and indicated the possible application of its extract in pharmaceutical and food industries as both a medicinal and food additive.

Recovery of Biologically Active Compounds from Stinging Nettle Leaves Part II: Processing of Exhausted Plant Material after Supercritical Fluid Extraction.

Stinging nettle (Urtica dioica L.) is one fantastic plant widely used in folk medicine, pharmacy, cosmetics, and food. This plant's popularity may be explained by its chemical composition, containing a wide range of compounds significant for human health and diet. This study aimed to investigate extracts of exhausted stinging nettle leaves after supercritical fluid extraction obtained using ultrasound and microwave techniques. Extracts were analyzed to obtain insight into the chemical composition and biological activity. These extracts were shown to be more potent than those of previously untreated leaves. The principal component analysis was applied as a pattern recognition tool to visualize the antioxidant capacity and cytotoxic activity of extract obtained from exhausted stinging nettle leaves. An artificial neural network model is presented for the prediction of the antioxidant activity of samples according to polyphenolic profile data, showing a suitable anticipation property (the r2 value during the training cycle for output variables was 0.999).

Cinnamon essential oil and its emulsion as efficient antibiofilm agents to combat Acinetobacter baumannii.

Acinetobacter baumannii is an emerging nosocomial pathogen resistant to a wide spectrum of antibiotics, with great potential to form a biofilm, which further aggravates treatment of infections caused by it. Therefore, searching for new potent agents that are efficient against A. baumannii seems to be a necessity. One of them, which has already been proven to possess a wide spectrum of biological activities, including antimicrobial effect, is cinnamon essential oil. Still, further increase of antibacterial efficacy and improvement of bioavailability of cinnamon oil is possible by emulsification process. The aim of this study was comparative analysis of cinnamon essential oil and its emulsion against biofilm forming A. baumannii clinical isolates. Furthermore, the investigation of toxicological aspects of possible applications of essential oil and emulsion was done as well. Gas chromatography-mass spectrometry of essential oil indicated trans-cinnamaldehyde as the most abundant component. The cinnamon emulsion was synthesized from cinnamon essential oil by combining modified low- and high- energy methods. Synthesized emulsion was characterized with Fourier-transform infrared spectroscopy and photon correlation spectroscopy. Both substances exhibited significant antibacterial (minimal inhibitory concentrations in the range 0.125-0.5 mg/ml) and antibiofilm effects (inhibitions of formation and reduction of pre-formed biofilm were 47-81 and 30-62%, respectively). Compared to essential oil, the efficacy of emulsion was even stronger considering the small share of pure oil (20%) in the emulsion. The result of biofilm eradication assay was confirmed by scanning electron microscopy. Even though the cytotoxicity was high especially for the emulsion, genotoxicity was not determined. In conclusion, strong antibacterial/antibiofilm effect against A. baumannii of the cinnamon essential oil and the fact that emulsification even potentiated the activity, seems to be of great significance. Observed cytotoxicity implicated that further analysis is needed in order to clearly determine active principles being responsible for obtained antibacterial/antibiofilm and cytotoxic properties.

The effect of various extraction techniques on the quality of sage (Salvia officinalis L.) essential oil, expressed by chemical composition, thermal properties and biological activity.

In this study, influence of the extraction techniques on the quality of the sage essential oil was investigated. Obtained samples were analyzed for chemical composition by GC/MS, thermal properties by thermogravimetric analysis (TGA), and for biological activity: antioxidant (DPPH, CUPRAC, FRAP, ABTS, HRSA and TBARS), microbiological (Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger), and cytotoxic (HeLa, LS-174, A549 and MRC-5) activities. Chemical composition showed that viridiflorol was principal compound in all samples followed by camphor, thujones, and verticiol. MWD 400 W was the most potent antioxidant agent, D 200 W and MWD 400 W antimicrobial agents, while hydrodistallates (D 200 W and D 400 W) were the most potent cytotoxic agents. An artificial neural network model was developed for the antioxidant activity anticipation of analyzed samples. These models showed good prediction properties (the r2 value during training cycle for output variables was 0.998).

Evaluation of novel green walnut liqueur as a source of antioxidants: Multi-method approach.

In this study, a novel green walnut liqueur (GWL) based on green walnuts, as the main ingredient, with the addition of fruits, aromatic plants, chocolate and honey, was produced at the pilot-scale. Antioxidant activity (AO) of the obtained GWL was determined using multiple AO assays in parallel, standard spectrophotometric (FC, DPPH and FRAP) and recently developed electrochemical ones, HydroxoPerhydroxoMercury(II) Complex and Mercury Reduction Antioxidant Power, and compared to similar commercial alcoholic beverages. Characterization of the GWL in terms of volatile and polyphenolic components was performed using SPE-GC-MS and HPLC-DAD-MS/MS, respectively. Sensory quality assessment was performed by experts in the field of sensory analysis of alcoholic beverages, using a scoring method. According to all AO assays applied, AO activity and total phenolics content of GWL were superior in comparison to commercial spirits considered. The volatile fraction of GWL was mainly composed of eugenol, α-terpineol and vanillin, while the most prevalent phenolic compounds were gallic (5.054 mg/L) and chlorogenic acid (1.307 mg/L) and flavonoids such as catechine (0.882 mg/L), quercetin (0.499 mg/L) and its sugar-conjugated derivatives, quercetin 3-O-glucoside (0.774 mg/L) and quercetin-3-O-rhamnoside (0.614 mg/L). Gallic acid is the major contributor to total AO activity, especially determined by DPPH and FRAP, followed by catechine, quercetin and chlorogenic acid. Among the terpenoids, contribution of eugenol to total AO activity is estimated as the highest. Excellent sensory quality (18.52 of maximum 20 scores) was ascribed to GWL. Consequently, the presence of bioactive compounds and high AO activity of GWL, in addition to high sensory quality score, indicates a high market potential for this high-value product.

Antioxidant and enzyme-inhibitory activity of peppermint extracts and essential oils obtained by conventional and emerging extraction techniques.

Peppermint is widely used medicinal plant with distinguished bioactive potential, therefore, the aim of present work was to develop novel peppermint extracts with high activity by application of traditional and emerging separation techniques. Conventional hydrodistillation and microwave-assisted hydrodistillation (MWHD) were applied for recovery of essential oil (EO), while organic solvent extraction using Soxhlet apparatus, microwave-assisted and ultrasound-assisted process and supercritical fluid extraction (SFE) were applied for non-selective recovery of peppermint lipophilic extracts. Extracts were characterized in terms of terpenoids profile with special emphasis on content of major compounds (mentol, menthone, isomenthol and eucalyptol). Antioxidant activity (DPPH, ABTS, CUPRAC, FRAP, chelating and phosphomolybdenum assay) and enzyme-inhibitory assays (acetylcholinesterase, butyrylcholinesterase, tyrosinase, amylase and glucosidase inhibition) were used for screening of peppermint bioactivity. MWHD was recognized as alternative for traditional process in EO recovery, while SFE extracts were useful for green production of solvent-free peppermint extracts rich in terpenoids and other lipophilic bioactives.

Chemical composition and antimicrobial activity of Osage orange (Maclura pomifera) leaf extracts.

The main goal of this study was to establish the chemical profile of Osage orange (Maclura pomifera) leaf extracts, obtained by conventional maceration technique, and to examine its antimicrobial activity. The identification and quantification of the extract compounds were done using ultra-high-performance liquid chromatography, with a diode array detector coupled with triple-quadrupole mass spectrometer and gas chromatography-mass spectrometry techniques. Thirty-one polyphenolic compounds were detected and identified in the ethanolic extracts, whereby 5-O-caffeoylquinic acid was found to be the dominant compound. Among other compounds, pentacosane and palmitic acid were the most abundant compounds in the dichloromethane extract. The preliminary antimicrobial activity screening shows that Gram-positive bacteria tend to be more sensitive to the investigated extracts. The highest antimicrobial activity was determined against Enterococcus faecalis ATCC 19433 and Listeria monocytogenes ATCC 35152. From these results, Osage orange leaves can be considered as plant material with significant antimicrobial properties.

Tomato pomace extract and organic peppermint essential oil as effective sodium nitrite replacement in cooked pork sausages.

The effect of supercritical fluid extract of tomato pomace (TP) and essential oil of organic peppermint (PM) on pH, color, residual nitrite content, lipid oxidation (TBARS value) and total plate count (TPC) of cooked pork sausages produced with 50 mg/kg of sodium nitrite was investigated. Five batches were produced: T1: 100 mg/kg of sodium nitrite; T2: 50 mg of sodium nitrite; T3: 50 mg of sodium nitrite and 0.150 µL/g TP; T4: 50 mg of sodium nitrite, 0.075 µL/g TP and 0.075 µL/g PM; T5: 50 mg of sodium nitrite and 0.150 µL/g PM. The lowest residual nitrite content and TBARS value were observed in treatment T4. The inclusion of TP increased redness of cooked pork sausages. TPC was the lowest in treatment T5. The results of this study showed that the addition of TP and PM enhanced quality of cooked sausages produced with reduced level of sodium nitrite.

New herbal bitter liqueur with high antioxidant activity and lower sugar content: innovative approach to liqueurs formulations.

Herbal liqueurs are spirits with numerous functional properties, due to the presence of bioactive extractable compounds deriving from herbs. The aim of this study was to obtain new herbal bitter liqueur (HBL) on the basis of twelve selected bitter and aromatic plants extracts, with an optimal sensory profile for consumer acceptance. Also, the determination of optimal sugar content in HBL was done. Furthermore, antioxidant (AO) capacity and total phenolic content (TPC) of HBL was evaluated and compared to similar commercial herbal spirits. Among five tested formulations, assessed by 9-point hedonic scale, HBL with the ratio of bitter and aromatic plants 1:4 was the most acceptable. Ideal concentration of sugar in HBL, determined using a just-about-right scale, was found to be 80.32 g/l of sucrose, which is approximately 20% less than the minimum stipulated by European Union Regulation and several times lower than in the majority of commercial liqueurs. Obtained result indicates the possibility of sugar reduction in liqueurs, and suggests the need to carry out sensory analysis before production of these high-calorie beverages. Radical scavenging ability against DPPH and ABTS radicals, as well as ferric reducing antioxidant power and TPC of HBL were convincingly superior in comparison to similar commercial herbal alcoholic beverages. High correlation coefficients between TPC and other assays applied strongly support the significant role of the polyphenols in the total AO capacity of the HBL and other tested commercial herbal spirits. Headspace GC/MS revealed that the most abundant terpenes were menthone (3.75%), eucalyptol (3.42%) and menthol (3.10%), whereas methanol was present in a small amount (4.97 mg/l).

Essential oil versus supercritical fluid extracts of winter savory (Satureja montana L.) - Assessment of the oxidative, microbiological and sensory quality of fresh pork sausages.

The effect of winter savory (Satureja montana L.) essential oil (SEO) and supercritical extracts (SE1; SE2) at concentrations of 0.075 and 0.150 µL/g on pH, lipid oxidation (TBARS), microbial growth and sensory quality of fresh pork sausages during storage were investigated. SEO, SE1 and SE2 improved oxidative and microbial stability of fresh pork sausages. The addition of SEO and SE1 at concentration of 0.150 µL/g affected the reduction of total Enterobacteriaeceae count to under 3 log cfu/g. Sausages produced with SE1 and SE2 had a higher scores for odor, flavor and overall acceptance compared to sausages treated with SEO and control sample. Therefore, the results of this paper revealed significant antioxidative and antimicrobial activity of SE1 and SE2, and consequently its high potential of utilization in processing of fresh pork sausages.

The influence of the extraction temperature on polyphenolic profiles and bioactivity of chamomile (Matricaria chamomilla L.) subcritical water extracts.

The main goal of this research was to determine the relationship among chemical structure, bioactivity and temperature of chamomile during subcritical water extraction in isobaric conditions (45 bar) at seven different temperatures (65-210 °C). The influence of temperature on phenolic profiles was defined by UHPLC-HESI-MS/MS. The overall results indicate that the presence of conjugated double bonds, side chains, glucose moiety or ether moiety in molecules influence the efficiency of polyphenols' extraction in subcritical water. In terms of antioxidant activity, the extracts were the most active towards ABTS radicals (IC50 = 7.3-16.8 µg/mL), whereby temperature of 150 °C was optimal. On the other hand, the extracts obtained at 115 °C showed highest cytotoxicity. Inhibition of α-amylase and α-glucosidase was the highest at 65 and 85 °C, i.e. 0.51 and 4.13 mmolAE/g, respectively. Activity against tyrosinase was the highest at 210 °C (17.92 mgKAE/g). The data showed that different non-phenolic compounds may also participate in bio-activities of the extracts.

Subcritical water extraction as a cutting edge technology for the extraction of bioactive compounds from chamomile: Influence of pressure on chemical composition and bioactivity of extracts.

The study was designed to determine the relationship between chemical structure, bioactivity and pressure during the subcritical water extraction (SCW) of chamomile. Extraction was carried out at isothermal conditions (100 °C) at five different pressures (10, 30, 45, 60 and 90 bar). Twenty three polyphenolic compounds were identified in the extracts, whereby apigenin was found to be the dominant compound (61.53-1344.99 mg/kg). Results suggest that the lowest applied pressure has negligible effect on phenolic recovery from chamomile, but also the use of pressures above than 45 bar was proven as needlessly. By using in vitro assays, influence of pressure on antioxidant, cytotoxic and enzyme-inhibitory activities of the extracts was evaluated. Extracts obtained at 30, 45 and 60 bar exhibited stronger bioactivities than at 10 and 90 bar. It was concluded that pressure exert a significant influence on chemical composition of extracts, and thus on biological activity of chamomile extracts.

Biological activity and chemical profile of Lavatera thuringiaca L. extracts obtained by different extraction approaches.

BACKGROUND: Lavatera thuringiaca L. is herbaceous perennial plant from Malvaceae family, which is known for its biological activity and richness in polyphenolic compounds. Despite this, the information regarding the biological activity and chemical profile is still insufficient. PURPOSE: Aim of this study was to investigate biological potential and chemical profile of Lavatera thuringiaca L., as well as influence of applied extraction technique on them. STUDY DESIGN AND METHODS: Two conventional and four non-conventional extraction techniques were applied in order to obtain extracts rich in bioactive compound. Extracts were further tested for total phenolics, flavonoids, condensed tannins, gallotannins and anthocyanins contents using spectrophotometric assays. Polyphenolic profile was established using HPLC-DAD analysis. Biological activity was investigated regarding antioxidant, cytotoxic and antibacterial activities. Four antioxidant assays were applied as well as three different cell lines for cytotoxic and fifteen bacterial strain for antibacterial activity. RESULTS AND CONCLUSION: Results showed that subcritical water extraction (SCW) dominated over the other extraction techniques, where SCW extract exhibited the highest biological activity. Study indicates that plant Lavatera thuringiaca L. may be used as a potential source of biologically compounds.