Monica Scognamiglio

Plant growth inhibitors: allelopathic role or phytotoxic effects? Focus on Mediterranean biomes

Allelopathy (the chemical based communication among plants) is gaining more and more attention thanks to its likely outcomes in several fields, but it is, in the meantime, a questionable topic, due to a difficult determination. Despite the broad literature, allelopathic interactions are far from being clarified. Conclusive evidence in this field is not a simple find, as this biological activity is governed by a number of different factors. Such an issue can be solved only provided that suitable methods are used. Understanding allelopathy in natural ecosystems may be crucial in order to think about the exploitation of this resource. Mediterranean plants, in particular, have been proven to be a source of natural active compounds. This paper reviews the most outstanding methods used for plant extract or pure metabolite phytotoxic or allelopathic properties determination. Furthermore, it points out the bioactive metabolites reported from plants characteristics of Mediterranean ecosystems.

Oleanane saponins from Bellis sylvestris Cyr. and evaluation of their phytotoxicity on Aegilops geniculata Roth

Six oleanane saponins were isolated for the first time from leaves of Bellis sylvestris Cyr., the southern daisy. Their structures were established by the extensive use of 2D-NMR experiments, including COSY, TOCSY, NOESY, HSQC, HMBC, CIGAR, H2BC, and HSQC-TOCSY, along with Q-TOF HRMS² analysis. All of the compounds are constituted by bayogenin as aglycone, and characterized by the presence of an oligosaccharide moiety, consisting of two to four sugar unities esterified at the C-28 carboxyl carbon. One of the isolated compounds is a bisdesmoside containing an additional sugar moiety at the C-3 carbon. The phytotoxic activity assayed against Aegilops geniculata Roth., a coexisting test species, has been evaluated revealing that all the compounds, at the highest concentrations, showed strong phytotoxicity against the leaf development.

Spectroscopic identification and anti-biofilm properties of polar metabolites from the medicinal plant Helichrysum italicum against Pseudomonas aeruginosa

Two new acylated styrylpyrones, one 5-methoxy-1(3H)-isobenzofuranone glucoside and a hydroxymethyl-orcinol derivative, along with sixteen known aromatic metabolites, including lignans, quinic acid derivatives low-molecular weight phenol glucosides, have been isolated from the methanol extract of Helichrysum italicum, a medicinal plant typical of the Mediterranean vegetation. The structures of these compounds have been elucidated on the basis of extensive 2D-NMR spectroscopic analyses, including COSY, TOCSY, HSQC, CIGAR-HMBC, H2BC and HSQC-TOCSY, along with Q-TOF HRMS(2) analysis. Selected compounds were evaluated for their anti-biofilm properties against Pseudomonas aeruginosa.

Structure elucidation and hepatotoxicity evaluation against HepG2 human cells of neo-clerodane diterpenes from Teucrium polium L.

Seven neo-clerodanes (teupolins VI-XII) and eleven known compounds were isolated and characterized from leaf extracts of Teucrium polium L., a medicinal plant used in traditional and herbal medicine for its hypolipidemic, hypoglycemic, antioxidant and antiproliferative properties. The structures of these compounds were elucidated by 1D (1H, 13C and DEPT) and 2D (COSY, TOCSY, HSQC, HMBC) NMR experiments and by mass spectrometry analysis. The complete stereostructure of each compound was defined with a NOESY experiment. Because the overexploitation of herbal remedies containing T. polium extracts has resulted in several cases of hepatitis, the hepatotoxic activity of pure metabolites against the human hepatoblastoma cancer cell line HepG2 was assessed by the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) test. All of the compounds showed low toxicity values at the highest concentration tested (200 μM).

Chemical Composition and Seasonality of Aromatic Mediterranean Plant Species by NMR-Based Metabolomics.

An NMR-based metabolomic approach has been applied to analyse seven aromatic Mediterranean plant species used in traditional cuisine. Based on the ethnobotanical use of these plants, the approach has been employed in order to study the metabolic changes during different seasons. Primary and secondary metabolites have been detected and quantified. Flavonoids (apigenin, quercetin, and kaempferol derivatives) and phenylpropanoid derivatives (e.g., chlorogenic and rosmarinic acid) are the main identified polyphenols. The richness in these metabolites could explain the biological properties ascribed to these plant species.

abeo-Abietanes from Teucrium polium roots as protective factors against oxidative stress

Six new 17(15→16)-abeo-abietanes, along with seven known compounds, were isolated and characterized from ethyl acetate root extract of Teucrium polium L., a medicinal plant belonging to the Labiatae family reported to have hypolipidemic, hypoglycaemic, anti-nociceptive and anti-inflammatory effects. Their structures were elucidated by 1D ((1)H, (13)C and DEPT) and 2D (COSY, TOCSY, HSQC, HMBC, and NOESY) NMR and mass spectral data. The antioxidative properties of pure metabolites were analyzed on the basis of their DPPH radical scavenging capability. The antioxidant capacity in cell-free systems of the isolated metabolites was carried out by measuring their capabilities to inhibit the synthesis of thiobarbituric acid reactive species in assay media using as oxidable substrates a vegetable fat and the pentose sugar 2-deoxyribose and to prevent oxidative damage of the bovine serum albumin (BSA) hydrosoluble protein. All of the compounds showed a significant and dose-response efficacy although weaker than that exercised by the standard Trolox®.

Chemical interactions between plants in Mediterranean vegetation: The influence of selected plant extracts on Aegilops geniculata metabolome

Allelopathy is the chemical mediated communication among plants. While on one hand there is growing interest in the field, on the other hand it is still debated as doubts exist at different levels. A number of compounds have been reported for their ability to influence plant growth, but the existence of this phenomenon in the field has rarely been demonstrated. Furthermore, only few studies have reported the uptake and the effects at molecular level of the allelochemicals. Allelopathy has been reported on some plants of Mediterranean vegetation and could contribute to structuring this ecosystem. Sixteen plants of Mediterranean vegetation have been selected and studied by an NMR-based metabolomics approach. The extracts of these donor plants have been characterized in terms of chemical composition and the effects on a selected receiving plant, Aegilops geniculata, have been studied both at the morphological and at the metabolic level. Most of the plant extracts employed in this study were found to have an activity, which could be correlated with the presence of flavonoids and hydroxycinnamate derivatives. These plant extracts affected the receiving plant in different ways, with different rates of growth inhibition at morphological level. The results of metabolomic analysis of treated plants suggested the induction of oxidative stress in all the receiving plants treated with active donor plant extracts, although differences were observed among the responses. Finally, the uptake and transport into receiving plant leaves of different metabolites present in the extracts added to the culture medium were observed.

NMR-based metabolic profiling and in vitro antioxidant and hepatotoxic assessment of partially purified fractions from Golden germander (Teucrium polium L.) methanolic extract

Golden germander (Teucrium polium L.) is a Mediterranean shrub of the Labiatae family, used in traditional medicine for its diuretic, antipyretic, diaphoretic, antispasmodic, tonic, anti-inflammatory, antihypertensive, anorexic, analgesic, antibacterial and antidiabetic effects. Like other plants of the Teucrium genus, it was widely popular because of its hypoglycemic and hypolipidemic properties but various cases of T. polium-induced hepatitis have been reported. neo-Clerodane diterpenoids, considered chemotaxonomic markers for the Teucrium genus, are believed to be responsible for the observed hepatotoxicity. The plant also produces flavonoids and phenylethanoid glycosides to which the antioxidant and cytoprotective therapeutic properties of its preparations can be traced back. In order to establish a herbal formula that preserves the plant beneficial properties, T. polium leaf drug has been subjected to a bio-guided fractionation. The different phytocomplexes obtained were analyzed by means of an extensive antioxidant screening and hepatotoxicity evaluation against HepG2, a human hepatoblastoma cell line. The cytotoxicity of the fractions was also evaluated against HeLa and A549 cell lines. In order to identify the substances responsible for the bioactivities, NMR-based metabolic profiling techniques of all the phytocomplexes were performed. Data obtained highlighted the possibility of preparing strong antioxidant extracts, useful as food additives, such as MeOH-2, and MeOH-3, completely devoid of hepatotoxic components.

Endophytism of Penicillium Species in Woody Plants

The genus Penicillium is ubiquitous and its species are commonly recovered from every kind of substrate and environmental conditions. Therefore, not surprisingly, Penicillium strains are commonly reported in investigations dealing with fungal endophytic assemblages of plants in both natural and anthropic contexts. As such they are implicated in more or less effective relationships with the host, and involved in applicative issues concerning plant protection and the production of bioactive compounds to be exploited as pharmaceuticals. The available data on occurrence, biocenotic role, production and bioactivities of secondary metabolites of Penicillium strains which have been isolated as endophytes from woody plants are reviewed in the present paper in the aim to introduce the state of the art to researchers involved in this particular field.

Chemical constituents and in vitro anti-inflammatory activity of Cistanche violacea Desf. (Orobanchaceae) extract

A new iridoid (1) and a new phenylethanoid glycoside (4), together with five known compounds (2, 3, 5, 6 and 7), were isolated for the first time from the ethyl acetate soluble part of the hydroalcoholic extract of the aerial parts of Cistanche violacea Desf. (Orobanchaceae), an endemic species of the North of the Sahara. The structures of these compounds have been elucidated on the basis of extensive 2D NMR spectroscopic analysis, including COSY, TOCSY, NOESY, HSQC, CIGAR-HMBC, H2BC and HSQC-TOCSY. All compounds were isolated from C. violacea for the first time. The anti-inflammatory activity of the EtOAc extract of C. violacea, was investigated by using human red blood cell (HRBC) membrane stabilization and inhibition of the albumin denaturation method. This study demonstrates, for the first time the effectiveness of C. violacea in combating inflammation, this might be believed to be influenced by the synergistic action of the above isolated compounds. The present study suggests that C. violacea would serve as a source for the discovery of novel anti-inflammatory agents.