Oxidative Stress Response Mechanisms Sustain the Antibacterial and Antioxidant Activity of Quercus ilex

The development of new natural antibiotics is considered as the heart of several investigations in the nutraceutical field. In this work, leaves of Quercus ilex L. treated by tropospheric ozone (O3) and nitrogen (N) deposition, exhibited a clear antimicrobial efficacy against five multi-drug resistant (MDR) bacterial strains (two gram-positive and three gram-negative). Under controlled conditions, it was studied how simulated N deposition influences the response to O3 and the antibacterial and antioxidant activity, and antioxidant performance. The extraction was performed by ultra-pure acetone using two different steps. A higher antioxidant activity was measured in the presence of interaction between O3 and N treatments on Quercus leaves. At the same time, all organic extracts tested have shown bacteriostatic activity against all the tested strains with a MIC comprised between 9 and 4 micrograms/mL, and a higher antioxidant efficacy shown by spectrophotometric assay. Stronger antimicrobial activity was found in the samples treated with O3, whereas N-treated plants exhibited an intermediate antibacterial performance. This performance is related to the stimulation of the non-enzymatic antioxidant system induced by the oxidative stress, which results in an increase in the production of antimicrobial bioactive compounds.

Chemical Composition of Salvia fruticosa Mill. Essential Oil and Its Protective Effects on Both Photosynthetic Damage and Oxidative Stress in Conocephalum conicum L. Induced by Environmental Heavy Metal Concentrations

The genus Salvia L., belonging to the Lamiaceae family, contains more than 900 species distributed in various parts of the world. It is a genus containing aromatic plants used both in the culinary field and above all in the cosmetic area to produce several perfumes. Salvia fruticosa Mill., notoriously known as Greek Salvia, is a plant used since ancient times in traditional medicine, but today cultivated and used in various parts of Europe and Africa. Polar and apolar extracts of this plant confirmed the presence of several metabolites such as abietane and labdane diterpenoids, triterpenoids, steroids, and some flavonoids, causing interesting properties such as sedative, carminative, and antiseptic, while its essential oils (EOs) are mainly characterized by compounds such as 1,8-cineole and camphor. The aim of this work concerns the chemical analysis by GC and GC-MS, and the investigation of the biological properties, of the EO of S. fruticosa plants collected in eastern Sicily. The gas-chromatographic analysis confirmed the presence of 1,8-cineole (17.38%) and camphor (12.81%), but at the same time, also moderate amounts of α-terpineol (6.74%), β-myrcene (9.07%), camphene (8.66%), β-pinene (6.55%), and α-pinene (6.45%). To study the protective effect of EOs from S. fruticosa (both the total mixture and the individual compounds) on possible damage induced by heavy metals, an in vitro system was used in which a model organism, the liverwort Conocephalum conicum, was subjected to the effect of a mix of heavy metals (HM) prepared using values of concentrations actually measured in one of the most polluted watercourses of the Campania region, the Regi Lagni. Finally, the antioxidant response and the photosynthetic damage were examined. The exogenous application of the EO yields a resumption of the oxidative stress induced by HM, as demonstrated by the reduction in the Reactive Oxygen Species (ROS) content and by the increased activity of antioxidant enzyme catalase (CAT) and glutathione-S-transferase (GST). Furthermore, plants treated with HMs and EO showed a higher Fv/Fm (maximal quantum efficiency of PSII in the dark) with respect to HMs-only treated ones. These results clearly indicate the protective capacity of the EO of S. fruticosa against oxidative stress, which is achieved at least in part by modulating the redox state through the antioxidant pathway and on photosynthetic damage.

Non-Protein Thiol Compounds and Antioxidant Responses Involved in Bryophyte Heavy-Metal Tolerance

Heavy-metal pollution represents a problem which has been widely discussed in recent years. The biological effects of heavy metals have been studied in both animals and plants, ranging from oxidative stress to genotoxicity. Plants, above all metal-tolerant species, have evolved a wide spectrum of strategies to counteract exposure to toxic metal concentrations. Among these strategies, the chelation and vacuolar sequestration of heavy metals are, after cell-wall immobilization, the first line of defence that prevent heavy metals from interacting with cell components. Furthermore, bryophytes activate a series of antioxidant non-enzymatic and enzymatic responses to counteract the effects of heavy metal in the cellular compartments. In this review, the role of non-protein thiol compounds and antioxidant molecules in bryophytes will be discussed.

The chemical composition of the aerial parts of Stachys spreitzenhoferi (Lamiaceae) growing in Kythira Island (Greece), and their antioxidant, antimicrobial, and antiproliferative properties

The Stachys L. genus has been used in traditional medicine to treat skin inflammations, stomach disorders, and stress. The aim of this study was to investigate the chemical profile and biological activity of the methanolic extract of Stachys spreitzenhoferi Heldr. (Lamiaceae) aerial parts, collected on the island of Kythira, South Greece. The analysis by liquid chromatography coupled with electrospray ionization and high-resolution mass spectrometry [LC-(-)ESI/HRMSⁿ] of the methanol extract revealed the occurrence of thirty-six compounds - flavonoids, phenylethanoid glycosides, iridoids, quinic acid derivatives, aliphatic alcohol glycosides, and oligosaccharides - highlighting the substantial presence, as main peaks, of the iridoid melittoside (2) along with flavonoid compounds such as 4'-O-methylisoscutellarein mono-acetyl-diglycoside/chrysoeriol mono-acetyl-diglycoside (24), trimethoxy- (35) and tetramethoxyflavones (36). This extract was tested for its antimicrobial properties against Gram-positive and negative pathogenic strains. The extract was not active against Gram-negative bacteria tested, but it possessed a good dose-dependent antimicrobial activity towards S. aureus (MIC: 1.0 mg/mL) and L. monocytogenes (MIC: 1.0 mg/mL) Gram-(+) strains. Furthermore, this extract has been tested for its possible antioxidant activity in vitro. In particular, it has been shown that these molecules cause a decrease in DPPH, ABTS, and H₂O₂ radicals. The extract of S. spreitzenhoferi exhibited anti-DPPH activity (IC₅₀: 0.17 mg/mL), anti-H₂O₂ activity (IC₅₀: 0.125 mg/mL), and promising antiradical effect with an IC₅₀ value of 0.18 mg/mL for anti-ABTS activity. S. spreitzenhoferi extract caused a decrease in ROS (at the concentration of 200 μg/mL) and an increase in the activity of the antioxidant enzymes SOD, CAT, and GPX in OZ-stimulated PMNs. Furthermore, it exhibited antiproliferative activity against acute myeloid leukemia (U937 cell), causing 50% of cell death at the 0.75 mg/mL.

Antioxidant response to heavy metal pollution of Regi Lagni freshwater in Conocephalum conicum L. (Dum.)

Conocephalum conicum L. is a cosmopolitan liverwort species able to respond to local environmental pollution by changing its biological features. In the present study, we assessed the different biological responses in C. conicum to heavy metal contamination of Regi Lagni channels, a highly polluted freshwater body. As for the in field experiment, we set up moss bags containing collected samples of the local wild growing C. conicum, from the upstream site (non-polluted area), and we exposed them in the three selected sites characterized by different and extreme conditions of heavy metal pollution. In addition, to better understand the contribution of heavy metals to the alterations and response of the liverwort, we performed in vitro tests, using the same concentration of heavy metals measured in the sites at the moment of the exposition. In both experimental settings, bioaccumulation, ultrastructural damage, reactive oxygen species production and localization, antioxidant enzymes activity (superoxide dismutase, catalase and glutathione S-transferases), glutathione (reduced and oxidized) levels, localization of compounds presenting thiol groups and phenolic content were investigated. The results showed that the samples from different sites and conditions (for in vitro tests) showed significant differences. In particular, the ultrastructural alterations show a trend correlated to the different exposure situations; ROS contents, glutathione, antioxidant enzyme activities, and phenolic contents were increased showing an enhancement of the antioxidant defense both by the enzymatic way and by using the synthesis of antioxidant phenolic compounds. This study confirms the ability of C. conicum to respond to heavy metal pollution and the responses studied are, at least partially, correlated to the presence of heavy metals. All the responses considered respond consistently with the pollution trend and they can be proposed as pollution biomarkers. Therefore, we suggest the use of C. conicum to identify local hot spots of pollution in further investigation.

Biological responses to heavy metal stress in the moss Leptodictyum riparium (Hedw.) Warnst

Leptodictyum riparium, a widely distributed aquatic moss, can both tolerate and accumulate very high concentrations of toxic heavy metals, with only slight apparent damage. Here we report the effects on photosynthetic yield, glutathione (GSH), phytochelatin (PCn) synthesis, nitrogen metabolism and cellular localization of molecules rich in SH groups in L. riparium exposed in vitro to heavy metals. We simulated the concentrations of Cu, Zn, Cd, Pb detected in Regi Lagni, Italy, one of the most contaminated freshwater sites in Southern Europe, in the laboratory to test how the moss responds to heavy metal contamination. There was a steady decrease of photosynthetic efficiency correlated with the heavy metal concentrations and ultrastructural organization. All PCn levels increased significantly as the concentration of heavy metals increased, while the GSH levels did not appear to be particularly affected. A significant increase of GDH and NADH-GOGAT activities increased with increasing heavy metal concentration. Immunoblotting analysis revealed an increase of the chl-GS2 while no significant increase was detected in the cyt-GS1. These results give insight into the molecular events underlying the metal-tolerance of the aquatic moss L. riparium exposed to environmental heavy metal concentrations.

Dihydrophenanthrenes from a Sicilian Accession of Himantoglossum robertianum (Loisel.) P. Delforge Showed Antioxidant, Antimicrobial, and Antiproliferative Activities

The peculiar aspect that emerges from the study of Orchidaceae is the presence of various molecules, which are particularly interesting for pharmaceutical chemistry due to their wide range of biological resources. The aim of our study was to investigate the properties of two dihydrophenanthrenes, isolated, for the first time, from Himantoglossum robertianum (Loisel.) P. Delforge (Orchidaceae) bulbs and roots. Chemical and spectroscopic study of the bulbs and roots of Himantoglossumrobertianum (Loisel.) P. Delforge resulted in the isolation of two known dihydrophenanthrenes-loroglossol and hircinol-never isolated from this plant species. The structures were evaluated based on ¹H-NMR, ¹³C-NMR, and two-dimensional spectra, and by comparison with the literature. These two molecules have been tested for their possible antioxidant, antimicrobial, antiproliferative, and proapoptotic activities. In particular, it has been shown that these molecules cause an increase in the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) in polymorphonuclear leukocytes (PMN); show antimicrobial activity against Escherichia coli and Staphylococcus aureus, and have anti-proliferative effects on gastric cancer cell lines, inducing apoptosis effects. Therefore, these two molecules could be considered promising candidates for pharmaceutical and nutraceutical preparations.

In-field and in-vitro study of the moss Leptodictyum riparium as bioindicator of toxic metal pollution in the aquatic environment: Ultrastructural damage, oxidative stress and HSP70 induction

This study evaluates the effects of toxic metal pollution in the highly contaminated Sarno River (South Italy), by using the aquatic moss Leptodictyum riparium in bags at 3 representative sites of the river. Biological effects were assessed by metal bioaccumulation, ultrastructural changes, oxidative stress, as Reactive Oxygen Species (ROS) production and Glutathione S-transferase (GST) activity, as well as Heat Shock Proteins 70 (HSP70s) induction. The results showed that L. riparium is a valuable bioindicator for toxic metal pollution of water ecosystem, accumulating different amounts of toxic metals from the aquatic environment. Toxic metal pollution caused severe ultrastructural damage, as well as increased ROS production and induction of GST and HSP70s, in the samples exposed at the polluted sites. To assess the role and the effect of toxic metals on L. riparium, were also cultured in vitro with Cd, Cr, Cu, Fe, Ni, Pb, Zn at the same concentrations as measured at the 3 sites. Ultrastructure, ROS, GST, and HSP70s resulted severely affected by toxic metals. Based on our findings, we confirm L. riparium as a model organism in freshwater biomonitoring surveys, and GST and HSP70s as promising biomarkers of metal toxicity.

Analysis of testosterone fatty acid esters in the digestive gland of mussels by liquid chromatography-high resolution mass spectrometry

Several studies have indicated that up to 70% of the total steroids detected in molluscs are in the esterified form and that pollutants, by modifying the esterification of steroids with fatty acids, might act as endocrine disrupters. However, despite the strong physiological significance of this process, there is almost no information on which fatty acids form the steroid esters and how this process is modulated. This study (a) investigates the formation of fatty acid esters of testosterone in digestive gland microsomal fractions of the mussel Mytilus galloprovincialis incubated with either palmitoly-CoA or CoA and ATP, and (b) assesses whether the endocrine disruptor tributyltin (TBT) interferes with the esterification of testosterone. Analysis of testosterone esters was performed by liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). When microsomal fractions were incubated with testosterone and palmitoly-CoA, the formation of testosterone palmitate was detected. However, when microsomes were incubated with CoA and ATP, and no exogenous activated fatty acid was added, the synthesis of 16:0, 16:1, 20:5 and 22:6 testosterone esters was observed. The presence of 100µM TBT in the incubation mixture did not significantly alter the esterification of testosterone. These results evidence the conjugation of testosterone with the most abundant fatty acids in the digestive gland microsomal fraction of mussels.

Effects of heavy metals on ultrastructure and Hsp70 induction in Lemna minor L. exposed to water along the Sarno River, Italy

The effects of freshwater pollution in the highly contaminated river Sarno (Campania, Southern Italy) have been evaluated using bags containing the aquatic plant Lemna minor (Lemnacee, Arales), in order to determine morpho-physiological modifications as a response to pollutants. The exposition of Lemna bags for 7 days on three different sites along the river path showed alterations in chloroplasts and vacuoles shape and organization. Moreover, some specimens were exposed in vitro at the same heavy metal (HM) concentrations measured in the polluted sites of the river, and compared with data from the bag experiment; to verify the dose and time dependent effects, samples were exposed to HM in vitro at concentrations ranging from 10(-6) to 10(-4)M up to 7 days. Transmission electron microscopy (TEM) observations on in vitro plants confirmed that ultrastructural alterations affected most of plastids and the shape of different subcellular structures, namely vacuoles; in in vitro stressed specimens, Heat Shock Proteins 70 (Hsp70) levels changed, in dependence of changing levels of HM measured in different sites along the river path. Thus L. minor exhibited a possible correlation between the levels of HM pollution and Hsp70 occurrence; interestingly, the data presented showed that copper specifically increased Hsp70 levels at concentrations detected in polluted river waters, whereas cadmium and lead did not; on the other side, the latter represent highly toxic elements when specimens were exposed to higher levels in vitro. The effects of specific elements in vitro are compared to those observed in bags exposed along the river path; thus results are examined in order to propose L. minor as an organism able to be utilized to monitor heavy metals pollution; the possibility of using Hsp70s as specific markers of HM pollution is discussed.