Plants strike back: Plant volatiles and their role in indirect defence against aphids.

As sessile organisms, plants have evolved different strategies to defend themselves against various biotic stressors. An important aspect of the complex response of plants to biotic stress is the emission of volatile compounds (VOCs), which are involved in direct and indirect plant defence mechanisms. Indirect plant defences include a range of plant traits that mediate defence against herbivores and play an important ecological role by not only utilising plants' own capabilities, but also signalling and attracting natural enemies of herbivores. Often the combination of volatiles emitted is specific to herbivores; they are consequently recognised by parasites and other predators, providing a clear link between the volatile signature and the prey. In this review, we focus on indirect plant defence and summarise current knowledge and perspectives on relationships between plants, aphids and parasitic wasps.

Influence of Climate-Related Environmental Stresses on Economically Important Essential Oils of Mediterranean Salvia sp.

Salvia L. is the largest genus in the family Lamiaceae, with about 1,000 species and a nearly cosmopolitan distribution. Salvia species are used in both traditional and conventional medicines, and other numerous industries, such as spices and perfumes. The number of papers dealing with Salvia exceeds 12,000 and mostly investigates their chemical composition and bioactive properties. A smaller proportion of papers however consider environmental factors, mostly on the effects of microclimate conditions on its geographic distribution along an altitudinal or longitudinal gradient, and very few studies can be found on the effects of emerging stressors on the commercial production of sages of medicinal and economical importance. Here, we summarize available data on the essential oil composition of three economically important sages from the Mediterranean area, that is, Salvia officinalis, Salvia officinalis subsp. lavandulifolia, and Salvia fruticosa, and the effects of climate-related environmental stressors on their chemical profiles. Environmental stress factors, such as an increase in soil salinity and aridity, and changes in annual average temperatures, are going to impose a serious risk on the commercial production of sage essential oils, which are commercially produced in many European countries. This review highlights the already confirmed effects of these stressors on three selected Salvia species and consequently the importance of mitigating the effects of climate change on the commercial production of these essential oils.

Biflavonoids: Important Contributions to the Health Benefits of Ginkgo (Ginkgo biloba L.).

Ginkgo (Ginkgo biloba L.) is one of the most distinctive plants, characterized by excellent resistance to various environmental conditions. It is used as an ornamental plant and is recognized as a medicinal plant in both traditional and Western medicine. Its bioactive potential is associated with the presence of flavonoids and terpene trilactones, but many other compounds may also have synergistic effects. Flavonoid dimers-biflavonoids-are important constituents of ginkgophytopharmaceuticals. Currently, the presence of 13 biflavonoids has been reported in ginkgo, of which amentoflavone, bilobetin, sciadopitysin, ginkgetin and isoginkgetin are the most common. Their role in plants remains unknown, but their bioactivity and potential role in the management of human health are better investigated. In this review, we have provided an overview of the chemistry, diversity and biological factors that influence the presence of biflavonoids in ginkgo, as well as their bioactive and health-related properties. We have focused on their antioxidant, anticancer, antiviral, antibacterial, antifungal and anti-inflammatory activities as well as their potential role in the treatment of cardiovascular, metabolic and neurodegenerative diseases. We also highlighted their potential toxicity and pointed out further research directions.

Exploring New Sources of Bioactive Phenolic Compounds from Western Balkan Mountains.

This study presents the first report on phenolic composition and bioactivity of ethanolic extracts of three plant species that grow in the western Balkan mountains and are used in traditional folk medicine: Valeriana montana, Salix retusa, and Campanula hercegovina. Phenolics were extracted from different aerial plant parts using 80% ethanol to assess the possibility of sustainable use of these plants as a source of bioactive compounds without disruption to the roots (for V. montana) or destruction of whole habitats (for S. retusa and C. hercegovina). The ethanolic extract of V. montana flower contained noticeable levels of apigenin and quercetin. The branches and bark of S. retusa were significantly rich in catechin, while rutin was the major phenolic found in the leaf extract of C. hercegovina. Furthermore, the flower extract of V. montana revealed the best antioxidant activity, which was comparable to 4-hydroxybenzoic acid and quercetin. Considering antimicrobial activity, the leaf extracts of V. montana and C. hercegovina demonstrated potent activity against all microbes tested, while the extracts of S. retusa were moderately effective. The presented results emphasize the potential of these plants as novel sources of bioactive compounds.

Influence of Extraction Solvent on the Phenolic Profile and Bioactivity of Two Achillea Species.

The phenolic composition, as well as the antioxidant and antimicrobial activities of two poorly investigated Achillea species, Achillea lingulata Waldst. and the endemic Achillea abrotanoides Vis., were studied. To obtain a more detailed phytochemical profile, four solvents with different polarities were used for the preparation of the plant extracts whose phenolic composition was analyzed using UHPLC-MS/MS (ultra-high performance liquid chromatography-tandem mass spectrometry). The results indicate that both of the investigated Achillea species are very rich in both phenolic acids and flavonoids, but that their profiles differ significantly. Chloroform extracts from both species had the highest yields and were the most chemically versatile. The majority of the examined extracts showed antimicrobial activity, while ethanolic extracts from both species were potent against all tested microorganisms. Furthermore, the antioxidant activity of the extracts was evaluated. It was found that the ethanolic extracts possessed the strongest antioxidant activities, although these extracts did not contain the highest amounts of detected phenolic compounds. In addition, several representatives of phenolic compounds were also assayed for these biological activities. Results suggest that ethanol is a sufficient solvent for the isolation of biologically active compounds from both Achillea species. Moreover, it was shown that the flavonoids naringenin and morin are mainly responsible for these antimicrobial activities, while caffeic, salicylic, chlorogenic, p-coumaric, p-hydroxybenzoic, and rosmarinic acid are responsible for the antioxidant activities of the Achillea extracts.

Use of seed priming to improve Cd accumulation and tolerance in Silene sendtneri, novel Cd hyper-accumulator.

Changes in the environment as a result of industrialisation and urbanisation impact negatively on plant growth and crop production. Cadmium (Cd) is one of the most dangerous metals that enters the food chain, with toxic effects on plants and human health. This study evaluated the potential of Silene sendtneri as a novel hyperaccumulator and the role of seed priming in tolerance and accumulation rate of Cd. The effect of different priming agents on germination performance, root growth, seedling development, metal uptake and accumulation, antioxidant defences including enzymatic and non-enzymatic antioxidants has been assessed. Seed priming using silicic acid, proline alone or in combination with salicylic acid- enhanced germination, seedling development, and root growth under Cd stress. The same priming treatments induced an increase of water content in shoots and roots when plants were exposed to Cd. The enzymatic antioxidant response was specific for the priming agent used. An increase in ferulic acid and rutin in shoots was related to the increase of Cd concentration in the medium. The concentration of malic and oxalic acid increased significantly in shoots of plants grown on high Cd concentrations compared to low Cd concentrations. Silene sendtneri can accumulate significant levels of Cd with enhanced accumulation rate and tolerance when seeds are primed. The best results are obtained by seed priming using 1% silicic acid, proline and salicylic acid.

Phenolic compounds and bioactive properties of Verbascum glabratum subsp. bosnense (K. Malý) Murb., an endemic plant species.

Detailed analysis of phenolic composition and antioxidant and antimicrobial activities of Verbascum glabratum subsp. bosnense (K. Malý) Murb., an endemic species of southeastern Dinaric Alps was performed for the first time. The phenolic composition measured via UHPLC-MS/MS of four extract with different polarity suggested this plant species is very rich in both phenolic acids and flavonoids. Ethanol extract was chemically the most versatile containing 12 compounds with quercitrin and rosmarinic acid as the majors, while water extracts were rich in 4-hydroxybenzoic acid, salicylic acid, morin, and apigenin. All extracts showed high antioxidant potential measured spectrophotometrically with IC50 values ranging 0.139 - 0.021 mg/mL. Antimicrobial testing using agar diffusion test showed that ethanol extract was the most potent against all tested organisms. Also, these activities are correlated with the content of phenolic compounds, which suggest they are active ingredients of the extracts.

Utilization of Mentha aquatica L. for removal of fecal pathogens and heavy metals from water of Bosna river, Bosnia and Herzegovina.

The aim of the present study was to investigate the potential of Mentha aquatica L. for phytoremediation of water contaminated with heavy metals and fecal pathogens from Bosna river. The water was treated with M. aquatica for 5, 10, and 15 days consecutively after which it was analyzed for the various physicochemical and microbiological parameters. The initial concentration of cadmium (Cd) ranged from 3.644 to 6.108 µg/l, while lead (Pb) varied between 0.1 and 1.386 µg/l. After treatment, M. aquatica accumulated significant amounts of cadmium (Cd) and lead (Pb) with the highest removal rates of 96.49% for Cd and 45.72% for Pb. Values of several physicochemical parameters were decreased after 15 days treatment period. All water samples were analyzed for enumeration of aerobic heterotrophic bacteria, total coliforms, and fecal coliforms by the membrane filtration. Removal efficiency was greater than 80% for microbiological parameters. The concentration of heavy metals was determined in different plant parts and subsequently, the translocation factor was determined. In M. aquatica plant parts, concentrations of Pb and Cd were increased after 15 days of treatment. Our results demonstrated that M. aquatica could be good candidates for the removal of fecal pathogens and heavy metals present in surface water.

Total phenolic and flavonoid contents, antioxidant and antimicrobial activities of Alnus glutinosa (L.) Gaertn., Alnus incana (L.) Moench and Alnus viridis (Chaix) DC. extracts.

The objective of this study was to determine total phenolic and flavonoid contents, antioxidant and antimicrobial activities of methanolic extracts from the leaves and barks of three Alnus species. The phenolic and flavonoid contents of extracts were determined spectrophotometrically using Folin-Ciocalteau and aluminium chloride methods, respectively. In addition, antioxidant activity of the extracts was determined using 1,1-diphenyl-2-picrylhydrazyl radical scavenging method. The antimicrobial activity was performed by disc diffusion assay against six reference bacterial strains including Gram-negative and Gram-positive bacteria and two fungal strains. Extract of Alnus viridis bark contained the highest amounts of total phenolics (780 mg CAT/g), while extract of A. viridis leaves had the highest amount of flavonoids (30.01 mg RUT/g). All extracts showed antioxidant activity higher than thymol, which was used as a positive probe. The largest diameters of inhibition zone (25 mm) were recorded with Bacillus subtilis 168 M and Staphylococcus aureus ATCC 6538.