Marcello Iriti

Chemical Diversity and Defence Metabolism: How Plants Cope with Pathogens and Ozone Pollution

Chemical defences represent a main trait of the plant innate immune system. Besides regulating the relationship between plants and their ecosystems, phytochemicals are involved both in resistance against pathogens and in tolerance towards abiotic stresses, such as atmospheric pollution. Plant defence metabolites arise from the main secondary metabolic routes, the phenylpropanoid, the isoprenoid and the alkaloid pathways. In plants, antibiotic compounds can be both preformed (phytoanticipins) and inducible (phytoalexins), the former including saponins, cyanogenic glycosides and glucosinolates. Chronic exposure to tropospheric ozone (O3) stimulates the carbon fluxes from the primary to the secondary metabolic pathways to a great extent, inducing a shift of the available resources in favour of the synthesis of secondary products. In some cases, the plant defence responses against pathogens and environmental pollutants may overlap, leading to the unspecific synthesis of similar molecules, such as phenylpropanoids. Exposure to ozone can also modify the pattern of biogenic volatile organic compounds (BVOC), emitted from plant in response to herbivore feeding, thus altering the tritrophic interaction among plant, phytophagy and their natural enemies. Finally, the synthesis of ethylene and polyamines can be regulated by ozone at level of S-adenosylmethionine (SAM), the biosynthetic precursor of both classes of hormones, which can, therefore, mutually inhibit their own biosynthesis with consequence on plant phenotype.

Traditional knowledge on medicinal and food plants used in Val San Giacomo (Sondrio, Italy)—An alpine ethnobotanical study

ETHNOPHARMACOLOGICAL RELEVANCE This work increases the ethnobotanical data from Northern Italy and, in particular, the Lombardy region, till now poorly documented, safeguarding the local folk knowledge, and provides information on new or scarcely reported properties of medicinal plants, whose traditional use needs to be validated experimentally. AIM OF THE STUDY The present study aimed to gather, analyse and evaluate the ethnobotanical information on the species used for medicinal and food purposes by the native people of Val San Giacomo. MATERIALS AND METHODS The plant use was documented by speaking with more than 100 people, mainly over 60 years old, born and resident in Val San Giacomo. Information was collected using semi-structured interviews and then analysed by indices such as Ethnophytonomic Index (EPI), Ethnobotanicity Index (EI), relative frequency of citation (RFC), use value (UV), relative importance (RI) and factor informant consensus (FIC). RESULTS Information on 66 plants belonging to 35 families (Asteraceae, Rosaceae and Lamiaceae, mainly) was gathered. The preference ranking placed Achillea moschata Wulfen at first place, both for the citation number and for RFC and UV. Arnica montana L., Thymus pulegioides L. and Artemisia genipi Stechm. were also in relevant use. Sixty species were wild and six were cultivated. Leaves, flowers, complete aerial parts and fruits were the plant parts most commonly used for remedy preparation (infusion, especially). The interviewees collected local flora for medicinal purposes, specifically. About 51.5% of the plant species were used to treat gastrointestinal tract of humans as digestive, depurative, appetiser, laxative, astringent and carminative remedies. About 56% of the plants were used in cookery, 24.2% in veterinary field, and 3% as cosmetics. The calculated indices demonstrated that in the studied area there is a small retention of plant knowledge. Only 6.2% of the autochthonous plants proved useful in folk tradition. Despite this, the uses of Sempervivum montanum L., Rhododendron ferrugineum L. and Panicum miliaceum L. were never documented by other ethnobotanical investigations conducted in the alpine area. CONCLUSIONS This survey was an extension of the ethnobotanical investigations performed in the Italian Alps. A study like this, though performed in a small area with a reduced traditional knowledge, could be the basis for subsequent research on the species that are interesting from a phytochemical point of view and on the potential use of their active metabolites.

Chemical-induced resistance against powdery mildew in barley: the effects of chitosan and benzothiadiazole

Chitosan (CHT), a deacetylated chitin derivative, and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a non toxic synthetic functional analogue of salicylic acid, were applied as foliar spray to barley plants (Hordeum vulgare L.), to compare their effectiveness in inducing resistance against Blumeria graminis f. sp. hordei and to investigate the underlying defence response. After an induction phase of 3 days (IP, time elapsed between treatment and fungal inoculation) both compounds reduced significantly the infection on the primary leaf, namely of 55.5% for CHT and of 68.9% for BTH, showing the induction of a good level of local resistance (LAR). A 5-day IP further reduced the infected areas in BTH treated plants (−77.2%) but not in CHT treated ones (−47.1%). Furthermore, both CHT and BTH also induced SAR, being the infection in the second non treated leaves reduced of 57% and 76.2%, respectively, as evaluated at 10-day IP. Both BTH and CHT induced oxidative burst and phenolic compound deposition in treated leaves, creating an hostile environment that slowed down the fungal spreading by impairing haustorium development. However, the greater efficacy of BTH was possibly due to: i) a greater reinforcement of papilla; ii) a higher level and the more homogeneous diffusion of H2O2 in the treated leaf tissues and iii) an induced hypersensitive-like response in many penetrated cells.

Anticancer Molecular Mechanisms of Resveratrol

Resveratrol is a pleiotropic phytochemical belonging to the stilbene family. Though it is only significantly present in grape products, a huge amount of preclinical studies investigated its anticancer properties in a plethora of cellular and animal models. Molecular mechanisms of resveratrol involved signaling pathways related to extracellular growth factors and receptor tyrosine kinases; formation of multiprotein complexes and cell metabolism; cell proliferation and genome instability; cytoplasmic tyrosine kinase signaling (cytokine, integrin, and developmental pathways); signal transduction by the transforming growth factor-β super-family; apoptosis and inflammation; and immune surveillance and hormone signaling. Resveratrol also showed a promising role to counteract multidrug resistance: in adjuvant therapy, associated with 5-fluoruracyl and cisplatin, resveratrol had additive and/or synergistic effects increasing the chemosensitization of cancer cells. Resveratrol, by acting on diverse mechanisms simultaneously, has been emphasized as a promising, multi-target, anticancer agent, relevant in both cancer prevention and treatment.

Melatonin, melatonin isomers and stilbenes in Italian traditional grape products and their antiradical capacity

Although polyphenols represent the paradigm of the health‐promoting effects ascribed to grape products, recently, attention has been paid to dietary melatonin, significantly present in Mediterranean foods. In this work, we measured melatonin, its isomers, stilbenes (trans‐ and cis‐resveratrol and their glucosides, piceids) and total polyphenols in some different grape products (red, white and dessert wines, grape juices and Modena balsamic vinegars) of distinct Italian areas. We also evaluated their antiradical activity by DPPH· and ABTS·+ assays. For indoleamine analysis, the separation was carried out on a 1.7‐μm C18 BEH column and the detection performed by means of mass spectrometry with electrospray ionization in positive ion mode with multiple reaction monitoring. The confirmation of the peak identity was accomplished by injection into the high‐resolution system (Orbitrap) using accurate mass measurements (error below 1.0 ppm). Mass spectrometry analyses revealed, for the first time, the presence of melatonin in dessert wines and balsamic vinegars, as well as the occurrence of three different melatonin isomers in grape products.

Neuroprotective herbs and foods from different traditional medicines and diets.

Plant secondary metabolites include an array of bioactive constituents form both medicinal and food plants able to improve human health. The exposure to these phytochemicals, including phenylpropanoids, isoprenoids and alkaloids, through correct dietary habits, may promote health benefits, protecting against the chronic degenerative disorders mainly seen in Western industrialized countries, such as cancer, cardiovascular and neurodegenerative diseases. In this review, we briefly deal with some plant foods and herbs of traditional medicines and diets, focusing on their neuroprotective active components. Because oxidative stress and neuroinflammation resulting from neuroglial activation, at the level of neurons, microglial cells and astrocytes, are key factors in the etiopathogenesis of both neurodegenerative and neurological diseases, emphasis will be placed on the antioxidant and anti-inflammatory activity exerted by specific molecules present in food plants or in remedies prescribed by herbal medicines.

Abscisic acid is involved in chitosan-induced resistance to tobacco necrosis virus (TNV).

Chitosan (CHT) antiviral activity has been further investigated in the pathosystem Phaseolus vulgaris - tobacco necrosis virus (TNV). CHT application elicited both callose apposition and ABA accumulation in leaf tissues, at 12 and 24h after treatment, respectively, and induced a high level of resistance against TNV. Besides, treatment with the ABA inhibitor nordihydroguaiaretic acid (NDGA), before CHT application, reduced both callose deposition and plant resistance to the virus, thus indicating the involvement of ABA in these processes. Exogenous application of ABA also induced a significant resistance to TNV, though this resistance was abolished by NDGA pre-treatment. These results, overall, indicate that the rise of ABA synthesis induced by chitosan plays an important role in enhancing callose deposition but the latter has only a partial effect on virus spreading, which must be constraint by other resistance mechanisms.

From vineyard to glass : agrochemicals enhance the melatonin and total polyphenol contents and antiradical activity of red wines

Abstract:  Resistance inducers are a class of agrochemicals, including benzothiadiazole and chitosan, which activate the plant own defence mechanisms. In this work, open‐field treatments with plant activators were performed on two red grape (Vitis vinifera L.) varieties cultivated in different localities, Groppello (Brescia, Lombardia, Italy) and Merlot (Treviso, Veneto, Italy). Treatments were carried out every 10 days until the véraison and, after harvesting, experimental wines (microvinificates) were prepared. In general, both melatonin and total polyphenol content, determined by mass spectrometry and Folin‐Ciocalteu assay, respectively, were higher in wines produced from grapes treated with resistance inducers than in those obtained from untreated control and conventional fungicide‐treated grapes. Accordingly, antiradical power of wines derived from plant activator‐treated grapes, measured by both DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) and the ABTS [(2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid)] radical–scavenging assay, was higher than in their counterparts. To the best of our knowledge, this is the first report on the effects of agrochemicals on the melatonin content of red wine.

Plant Polyphenols and Oral Health: Old Phytochemicals for New Fields

Despite the protective role of diets rich in fruit plant polyphenols against some cancers and chronic degenerative and inflammatory diseases, insufficient emphasis has been placed on oral health. Numerous studies have aimed to ascertain the role of polyphenols in the prevention and treatment of oral diseases; however, even when in vitro evidence appears convincing, the same is not true for in vivo studies, and thus there is a general paucity of solid evidence based on animal and clinical trials. To the best of our knowledge, only two reviews of polyphenols and oral health have been published; however, neither considered the potential role of whole plant extracts, which contain mixtures of many polyphenols that are often not completely identified. In the present study, our main aim was to review the current state of knowledge (search period: January 1965 to March 2011) on the effects of plant extracts/polyphenols on oral health. We found data on grapes, berries, tea, cocoa, coffee, myrtle, chamomile, honey/propolis, aloe extracts and the three main groups of polyphenols (stilbenes, flavonoids and proanthocyanidins). Their effects on caries, gingivitis, periodontal disease, candidiasis, oral aphtae, oral mucositis, oral lichen planus, leukoplakia and oral cancer were investigated. The data suggest that there is a lack of strong evidence, in particular regarding randomized clinical trials. However, a fascinating starting point has been provided by pre-clinical studies that have shown interesting activities of polyphenols against the most common oral diseases (caries, periodontitis and candidiasis), as well as in oral cancer prevention.

The presence of melatonin in grapevine (Vitis vinifera L.) berry tissues

Abstract:  Melatonin has been reported in a variety of food plants and, consequently, in a number of plant‐derived foodstuffs. In grapevine (Vitis vinifera L.) products, it was found in berry exocarp (skin) of different cultivars and monovarietal wines. Herein, we assessed, by means of mass spectrometry, the occurrence of melatonin in all berry tissues (skin, flesh, and seed) at two different phenological stages, pre‐véraison and véraison. We detected the highest melatonin content in skin, at pre‐véraison, whereas, at véraison, the highest levels were reported in the seed. Furthermore, during ripening, melatonin decreased in skin, while increasing in both seed and flesh. The relative concentrations of melatonin in diverse berry tissues were somewhat different from those of total polyphenols (TP), the latter measured by the Folin‐Ciocalteau assay, and more abundant in seed at pre‐véraison and in exocarp at véraison. The highest antiradical activity, determined by both DPPH (2,2‐diphenyl‐1‐pycryl hydrazyl) and ABTS [(2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid)] radical‐scavenging assay, was reported at pre‐veráison in seed. To the best of our knowledge, we reported, for the first time, the occurrence of melatonin in grape seeds.