Autotoxicity and allelopathy of 3,4-dihydroxyacetophenone isolated from Picea schrenkiana needles

Bioassay-guided fractionation of the diethyl ether fraction of a water extract of Picea schrenkiana needles led to the isolation of the phenolic compound 3,4-dihydroxy- acetophenone (DHAP). The allelopathic effects of DHAP were evaluated under laboratory conditions on P. schrenkiana, rice (Oryza sativa L.), wheat (Triticum aestivum L.), radish (Raphanus sativus L.), lettuce (Latuca sativa L.), cucumber (Cucumis sativus L.) and mung bean (Phaseolus radiatus L.). DHAP significantly inhibited seed germination and seedling growth of P. schrenkiana at concentrations of 2.5 mM and 0.5 mM (p < 0.05). Soil analysis revealed that P. schrenkiana forest soils contained exceptionally high DHAP concentrations (mean = 0.51 ± 0.03 mg/g dry soil), suf?cient to inhibit natural P. schrenkiana recruitment. DHAP also exhibited strong allelopathic potential. It significantly inhibited wheat and lettuce seed germination at concentrations of 1 mM and 0.5 mM (p < 0.05). The active compound also completely inhibited root growth of the six test species at high concentrations. Our results suggest a dual role of DHAP, both as an allelochemical and as an autotoxicant. The potential for a single plant needle-leached compound to in?uence both inter- and intra-speci?c interactions emphasized the complex effects that plant secondary metabolites might have on plant population and community structure.     

Phytotoxic effects and a phytotoxin from the invasive plant Xanthium italicum Moretti

The allelopathic effects of different parts of the plant Xanthium italicum Moretti were evaluated by conducting bioassays against two dicot plants, amaranth (Amaranthus mangostanus L.) and lettuce (Lectuca sativa L.), and two monocot plants, wheat (Triticum aestivum Linn) and ryegrass (Lolium multiforum). Leaf and fruit extract possessed the strongest biological activity, killing all seeds of four test species at 0.05 g/mL concentration. Fruits were chosen for further investigation because of their high biomass. This led to the isolation and identification of a phytotoxin-Xanthinosin-a known sesquiterpene lactone. Xanthinosin significantly affected seedling growth of all test species at 160 μM concentration. Cultivating seeds in 800 μM xanthinosin solution resulted in a great decrease in seedling growth of all test species, especially for the two dicot plants, amaranth and lettuce, whose root length was inhibited by 78% and 89%, respectively. By comparison, the numbers were 69% lower for wheat, and 66% for ryegrass, two monocot plants. When treated with 4 mM xanthinosin solution, seed germination of all test plants was almost completely inhibited. The possibility of utilizing xanthinosin as an eco-friendly herbicide was discussed.     

Investigation of heavy-metal uptake by vegetables growing in contaminated soils using the modified BCR sequential extraction method

The heavy metal (Cu, Fe, Co, Ni, Cd, Cr, Pb, Zn, and Mn) concentrations in soils and in vegetable samples, i.e. lettuce (Lactuca sativa L.), parsley (Petroselinum crispum), dill (Anethum graveolens), and onion (Allium cepa L.), taken from three urban vegetable gardens in Kayseri, Turkey, were determined by FAAS. The modified three-step sequential extraction procedure proposed by the European Bureau of References (BCR), now the Standards, Measurements and Testing Programme, was used in order to evaluate trace elements mobility in soil samples, and heavy-metal uptake by vegetables. Three operationally defined fractions were isolated using the BCR procedure: acid extractable (i.e. bound to carbonates), reducible (bound to Fe/Mn oxides), and oxidizable (bound to organic matter and sulphides). The vegetable samples were prepared to analysis using the wet-ashing procedure. To estimate the accuracy of the method used in analysis of the vegetable samples, the standard reference material (NIST SRM 1573a, Tomato leaves) was used. The results of recovery for all the elements were relatively satisfactory (87.7–108%). For the soil samples, the recovery values were calculated by proportioning the sum of the steps of the BCR procedure to those of the pseudototal digestion (i.e. aqua regia). In soils, the mobility of heavy metals followed the order Mn>Cd>Cu>Pb>Zn>Cr>Ni>Co>Fe. The relationship between the vegetable–metal and soil–extractable metal concentrations was examined in order to evaluate the bioavailability of metals, and the positive correlation, especially for the first (i.e. water, acid-soluble and exchangeable fraction) and for the third (i.e. oxidizable fraction) extraction steps, was obtained.     

Cytoprotective effect against mercury chloride and bioinsecticidal activity of Eugenia jambolana Lam.

The fruit fly Drosophila melanogaster is often utilized in genetic research, and in the last decades, it has become one of best organisms for studies of human diseases and toxicological research. Mercury chloride (HgCl₂), the main representative of mercury compounds, is the target of numerous investigations, not only because of its intrinsic toxicity but also because it accounts for the toxicity of elemental mercury since the latter is converted to Hg⁺² by oxidation. Eugenia jambolana Lam. Myrtaceae, known in Brazil as “jambolão”, is of great interest because of its medicinal applications, especially its leaves and fruits. The aim of this work was to characterize, by CG–MS, the chemical constituents of the essential oil of Eugenia jambolana and to evaluate its bioinsecticidal action in the Drosophila melanogaster model, as well as to determine the cytoprotective and chelating effect of the extract of E. jambolana. The results obtained here point to the potential of essential oils as a source in biological prospecting for bioinsecticides. Because of their biodegradability, essential oils can be important tools in the biological control of pests. The results demonstrated that the extract has an allelopathic effect on lettuce seeds and that its interaction with mercury chloride allows a greater growth of the radicle and plumule of Lactuta sativa seedlings, showing that this plant can provide an alternative solution to the problem of contamination by heavy metals, besides having cytoprotective potential and moderate chelating activity.     

Decarboxylation of lndole-3-Acetic Acid and Inhibition of Growth in Avena sativa Seedlings by Plant-Derived Photosensitizers*

Abstract— A number of plant phototoxins, when supplemented with UVA (320–400 nm) radiation, are capable of sensitizing the decomposition of indole-3-acetic acid (IAA), as measured by release of ¹⁴CO₂ from carboxyl-labeled IAA. Alpha-terthienyl (αT) and harmine caused significant rates of IAA decarboxylation at concentrations as low as 1 nM and were approximately 80% as effective as riboflavin and flavin mononucleotide. Partial inhibition by sodium azide indicates that the aT-induced decarboxylation of IAA is predominately, but not entirely, a type II reaction mediated by singlet oxygen. Based on changes in UV ab sorption spectra, it appears that the hormones gibberellic acid, abscisic acid and 6-benzylaminopurine (a cytokinin) are less susceptible to photosensitized decomposition than is IAA. Alpha-terthienyl plus UVA also inhibited elongation growth and reduced endogenous IAA levels in Avena sativa L. coleoptile sections and promoted senescence in intact Avena seedlings. These results confirm the allelopathic potential of plant photosensitizers such as αT and indicate that the phytohormone IAA may represent an additional target for the action of photosensitizers.     

Allelopathic activity and chemical constituents of extracts from roots of Euphorbia heterophylla L

Euphorbia heterophylla L. is regarded as a major weed worldwide. Its high aggressiveness in agricultural environment prompted us to investigate the allelopatic activity and chemical constitution of extracts from roots of this plant. Hexane extract showed low phytotoxic activity. Methanol extract at 2.0 mg mL^?1 inhibited 100% of germination, root and shoot growth of the indicator plants Sorghum bicolor and Lactuca sativa. β-sitosterol, stigmasterol, and esters of lupeol, germanicol, taraxasterol, pseudotaraxasterol, α-amyrin and β-amyrin were isolated from the hexane extract and their structures elucidated on the basis of MS and ¹H, ¹³C and DEPT-135 NMR data. GC-MS analysis of the derivatized methanol extract allowed for identifying a series of allelopathic organic acids potentially involved in allelopathic interactions of E. heterophylla. This is the first study on the allelopathic activity of extracts and identification of metabolites from roots of E. heterophylla.     

PHOTOTROPISM AND AXIS EXTENSION IN LIGHT-GROWN MUSTARD (Sinapis alba L.) SEEDLINGS‡

Abstract— The relationship between phototropism and axis extension was examined in light-grown mustard (Sinapis alba L.) seedlings using the low pressure sodium lamp (SOX)? technique to eliminate growth responses due to phytochrome. Addition of blue light caused no net inhibition of hypocotyl elongation, but plants showed a phototropic response. Curvature was caused by a simultaneous inhibition of growth on the illuminated side of the hypocotyl and an acceleration on the shaded side. Phototropism thus occurs independently of axis elongation and suggests that they are two separate processes. The results are inconsistent with the Blaauw theory of phototropism.     

THE TEMPERATURE DEPENDENCE OF Pfr ACTION GOVERNS THE UPPER TEMPERATURE LIMIT FOR GERMINATION IN LETTUCE

In most cultivars of lettuce (Lactuca saliva L,), red light acting through the red/far-red reversible phytochrome system promotes full germination within the20–30°C range, but at progressively higher temperatures germination declines sharply. The relationship between this upper ternperature limit for germination and the temperature dependence of phytochrome action was investigated in Grand Rapids lettuce. In fresh seeds the GT₅₀ (temperature giving half maximal germination) was ca 29–30°C. In these seeds, escape from far-red reversibility did not occur at 35°C, a temperature above the GT₅₀, but occurred rapidly at 27°C, a temperature below the upper limit. Increasing periods of dark pretreatment at high temperature (35°C) or increasing concentrations of the germination inhibitor coumarin caused a progressive decline in the GT₅₀, Escape from photoreversibility did not occur at 27°C in seeds in which the GT₅₀ had been reduced to less than 25°C by coumarin or by prolonged high temperature pretreatment. These results indicate that there is a close correlation between the position of the upper temperature limit for germination, and the temperature dependence of phytochrome action. We conclude that factors that alter the upper temperature limit for germination do so by changing the temperature dependence of phytochrome action.     

Agrocybynes A–E from the culture broth of Agrocybe praecox

Five novel compounds (1–3, 5, and 6), and two known ones (4 and 7) were isolated from the culture broth of Agrocybe praecox. Their structures were determined by the interpretation of spectroscopic data. Compounds 1–4 inhibited hypocotyl growth of lettuce, and 1, 3, and 4 inhibited the root growth.     

Phytochemical characterisation and bioprospection for antibacterial and antioxidant activities of Lippia alba Brown ex Britton & Wilson (Verbenaceae)

Ethanol extract and fractions obtained from fresh and dry aerial parts of Lippia alba were examined in order to determine their phytochemical composition, antioxidant capacity and antibacterial activities. The ethanol extracts and fractions exhibited an antioxidant effect by the DPPH assay, especially samples of fresh plant. HPLC analysis of the ethyl acetate fractions identified the presence of phenolic acids and flavonoids. The ethanol extract and fractions showed activity against reference and multidrug-resistant strains of Staphylococcus aureus and Enterococcus faecalis (MIC range 2000–250 μg/mL). The hexane and dichloromethane fractions of fresh plant showed better activity against reference strains of Escherichia coli (MIC of 250 and 125 μg/mL, respectively), but all extracts and fractions were less active against multidrug-resistant strains of all the Gram-negative species evaluated. The results showed that the extract and fractions of L alba aerial parts showed antibacterial activity, even against multidrug-resistant Gram-positive bacteria, and antioxidant effect (DPPH assay).     

Fascicularones H–K,Four New Sesquiterpenoids from the Cultured Mycelia of the Fungus Hypholoma fasciculare

The AcOEt extract of Hypholoma fasciculare yielded four new congeners, fascicularones H ( 4 ), I ( 5 ), J ( 6 ), and K ( 7 ). All structures were unambiguously established by 1D and 2D NMR and MS data. In a lettuce seedling assay, compounds 4 – 7 showed radicle elongation.     

RELATIVE IMPORTANCE OF BLUE LIGHT AND LIGHT ABSORBED BY PHYTOCHROME IN GROWTH OF MUSTARD (Sinapis alba L.) SEEDLINGS*

Abstract— Hypocotyl straight growth in mustard (Sinapis alba L.) responds very strongly and in precisely the same way to low fluence rate red (RL) and white light (WL). The effect of weak light can be attributed fully to light absorption by phytochrome. Only with increasing fluence rate an effect of blue light (BL) comes into play which cannot be explained by the action of phytochrome. However, this specific action of BL can be demonstrated in hypocotyl growth of mustard seedlings only up to 5 days after sowing (25°C). With older seedlings control of hypocotyl growth seems to be exerted exclusively via phytochrome. Regarding the far-red light dependent “high irradiance reaction” (FR-HIR) it was found that it plays a dominant role in growth of mustard only during a relatively short period. It tends to disappear in favor of a RL-HIR between 3 and 4 days after sowing. It is concluded that the seedling exhibits a largely endogenous temporal pattern of responsiveness to light. Phototropism of the mustard seedling can be elicited by low fluence rates (< 1 mW m^?2) of unilateral BL. This same light has no effect on straight growth. It is concluded that BL-dependent phototropic growth response of a hypocotyl and the effect of BL on longitudinal growth of the hypocotyl are unrelated phenomena.     

Study of allelopathic effects of Eucalyptus erythrocorys L. crude extracts against germination and seedling growth of weeds and wheat

Allelopathic materials inside a tree can produce positive or negative change in the survival, growth, reproduction and behaviour of other organisms if they escape into the environment. To assess these effects, this work was carried out to evaluate the allelopathic impact of Eucalyptus erythrocorys L. on seed germination and seedling growth of two weeds: Sinapis arvensis L. and Phalaris canariensis L.; on one cultivated crop: Triticum durum L. Aqueous; and on ethanolic leaf extracts of E. erythrocorys L. The study was effected using four concentrations (10, 20, 25 and 30 μL/mL) while distilled water was used as a control. The results showed that the E. erythrocorys L. crude extracts had an inhibitory effect on seed germination and seedling growth of both studied weeds and wheat. The inhibition rate was increased by the increase in extract concentration. Only ethanolic extracts of E. erythrocorys L. induced a significant inhibition of seed germination of durum wheat. The effect of E. erythrocorys L. crude extracts was more severe on weeds than on durum wheat. These results indicate that the seedling growth, especially radicle elongation, was the more sensitive indicator to evaluate the effects of extracts than was the seed germination.     

Impact of Short Time Atmospheric Plasma Treatment on Onion Seeds

The paper presents the results of an experiment on the effect of cold plasma (He?+?O₂ and He?+?Air) generated in a radio frequency cold atmospheric plasma jet on the process of germination of onion cv. Wolska (Allium cepa L.) seeds. In order to determine the impact of the gas flow on the seed surface, CFD simulations and Schlieren imaging were performed and surface characteristics were studied using a digital microscope. Plasma treatment of the seeds was carried out four times (2, 5, 10 and 15 s) with one control group. Pre-sowing plasma stimulation of seeds improved the germination capacity and germination energy for all tested groups in comparison to the control. The best germination capacity and energy were obtained for seeds stimulated with 10 s of plasma treatment. Analysis of the data showed a statistically significant impact of plasma treatment on the onion seed’s germination parameters. Plasma treatment did not induce significant changes on the seed surface, as microscope images showed but length of all plasma-treated seedlings increased in comparison to control.

     

Three new sulphur glycosides from the seeds of Descurainia sophia

Three new sulphur glycosides, raphanuside B–D (1–3), together with a known sulphur glycoside, raphanuside (4) were isolated from the decoction of the seeds of Descurainia sophia (L.) Webb ex Prantl, and the compound 4 was reported for the first time from this plant. Their structures were identified by means of UV, IR, 1D, 2D NMR (HSQC, HMBC and NOESY) and HR–ESI–MS spectroscopic data.     

The Organosulfur Chemistry of the Genus Allium – Implications for the Organic Chemistry of Sulfur

A Cook's tour is presented of the organosulfur chemistry of the genus Allium, as represented, inter alia, by garlic (Allium sativum L.) and onion (Allium cepa L.). We report on the biosynthesis of the S-alk(en)yl-L -cysteine S-oxides (aroma and flavor precursors) in intact plants and on how upon cutting or crushing the plants these precursors are cleaved by allinase enzymes, giving sulfenic acids—highly reactive organosulfur intermediates. In garlic, 2-propenesulfenic acid gives allicin, a thiosulfinate with antibiotic properties, while in onion 1-propenesulfenic acid rearranges to the sulfine (Z)-propanethial S-oxide, the lachrymatory factor (LF) of onion. Highlights of onion chemistry include the assignment of stereochemistry to the LF and determination of the mechanism of its dimerization; the isolation, characterization, and synthesis of thiosulfinates which most closely duplicate the taste and aroma of the freshly cut bulb, and additional unusual compounds such as zwiebelanes (dithiabicyclo[2.1.1]hexanes), a bis-sulfine (a 1,4-butanedithial S,S′-dioxide), antithrombotic and antiasthmatic cepaenes (α-sulfinyl disulfides), and vic-disulfoxides. Especially noteworthy in the chemistry of garlic are the discovery of ajoene, a potent antithrombotic agent from garlic, and the elucidation of the unique sequence of reactions that occur when diallyl disulfide, which is present in steam-distilled garlic oil, is heated. Reaction mechanisms under discussion include [3, 3]- and [2, 3]-sigma-tropic rearrangements involving sulfur (e.g. sulfoxide-accelerated thio- and dithio-Claisen rearrangements) and cycloadditions involving thiocarbonyl systems. In view of the culinary importance of alliaceous plants as well as the unique history of their use in folk medicine, this survey concludes with a discussion of the physiological activity of the components of these plants: cancer prevention, antimicrobial activity, insect and animal attractive/repulsive activity, olfactory–gustatory–lachrymatory properties, effect on lipid metabolism, platelet aggregation inhibitory activity and properties associated with ajoene. And naturally, comments about onion and garlic induced bad breath and heartburn may not be overlooked.     

Thin-layer chromatographic fingerprinting of the nonvolatile fraction extracted from the medicinal herb Cistus incanus L.

ABSTRACT

The aim of this study was to provide the first from-start-to-end thin-layer chromatographic method of fingerprinting the Cistus incanus L. raw herbal material, with a purpose to further use it for rapid screening, authentication, and quality control of the traded C. incanus L. herbs. To this effect, 12 different C. incanus L. samples purchased as herbal teas from a local market were extracted by means of the accelerated solvent extraction (ASE) with chemometrically optimized solvent extraction mixture and temperature (methanol–water, 27:73, v/v; 130°C), to derive the polar fraction from the plant samples. Then, the extracts were developed in two thin-layer chromatographic systems, both using the commercially precoated silica gel 60 chromatographic plates, yet two different mobile phases (mobile phase 1, ethyl acetate–formic acid–acetic acid–water, 100:11:11:13, v/v/v/v, and mobile phase 2, ethyl acetate–dichloromethane–formic acid–acetic acid–water, 100:10:10:10:11, v/v/v/v/v). The chromatograms were densitometrically scanned in the reflectance mode at the wavelength λ?=?366?nm to obtain fingerprints of the extracts derived from individual C. incanus L. samples. Mobile phase 2 performed slightly better, because with its use, the maximum number of 11 peaks could be seen in the respective fingerprints, whereas with mobile phase 1, the maximum number of 10 peaks only. Then an antioxidant potential of the investigated herbal extracts was assessed, making use of mobile phase 2 and the 0.20% methanol solution of 2,2-diphenyl picrylhydrazyl as a visualizing reagent. The resulting chromatograms were densitometrically scanned in the extinction mode at the wavelength λ?=?550?nm to obtain biological fingerprints of the extracts. Finally, chromatographic and biological fingerprints underwent a semiquantitative evaluation in terms of the contents of the extracted polar fraction and an overall antioxidant potential of the individual plant species.     

Functional properties and fatty acids profile of different beans varieties

Dried seeds of four varieties of Phaseolus vulgaris, three of Vigna unguiculata ssp. unguiculata and two of Vigna angularis grown and marketed in Italy, Mexico, India, Japan, Ghana and Ivory Coast were analysed for fatty acids content. In oils from seeds of P. vulgaris, the main fatty acids were linolenic (34.7–41.5%) and linoleic (30.7–40.3%), followed by palmitic (10.7–16.8%). The first three aforementioned fatty acids in the lipid fraction of V. unguiculata varieties were 28.4, 28.7 and 26.2%, respectively; while in V. angularis varieties, main fatty acids were linoleic (36.4–39.1%) and palmitic (26.9–33.3%), followed by linolenic (17.9–22.2%). Statistical analyses indicate that botanical species play a rule in bean fatty acids distribution, while the same was not verified for geographical origin. Furthermore, the atherogenic index (AI) and the thrombogenic index (TI) were investigated for health and nutritional information. The results showed that these wide spread legumes have functional features to human health.     

Production of a new mucilage compound in Lepidium sativum callus by optimizing in vitro growth conditions

The mucilage in Lepidium sativum L. is considered a biologically active compound with diverse medicinal properties. Different explants (hypocotyls and leaf) were transferred to Murashige and Skoog (MS) medium supplemented with twelve different plant growth regulator combinations under two different incubations (light and dark). The best mucilage production from callus (36.76% g g^?1 dry weight) was obtained in the MS medium supplemented with 1 mg L^?1 of 2, 4-D and 2 mg L^?1 of BAP under the light condition. The mucilage produced by callus culture was nearly three times more than the mucilage yield of the seeds. The glucose, arabinose + mannose and galactose were 43.4 (mg g^?1 DW), 195.3 (mg g^?1 DW) and 86.2 (mg g^?1 DW) in the mucilage originated from seed, callus leaf and callus hypocotyl, respectively. The present study proposes an efficient method for producing large scales of mucilage with a favorable sugar aimed at food or pharmaceutical industries.     

RESPONSES OF LIGHT-GROWN WILD-TYPE and LONG-HYPOCOTYL MUTANT CUCUMBER SEEDLINGS TO NATURAL and SIMULATED SHADE LIGHT*

The photomorphogenic control of hypocotyl extension growth was characterized in wild type (WT) and long hypocotyl (Ih) mutant seedlings of cucumber (Cucumis sativus L.) grown under natural radiation in outdoor and glasshouse experiments. Hypocotyl extension growth of WT plants was promoted by supplementing sunlight with far-red light during the photoperiod, by reducing the amount of blue light reaching either the whole shoot or the hypocotyl, and by reducing the amount of UV reaching the whole shoot.The Ih seedlings only responded to a reduction in UV-B levels. Both WT and Ih seedlings showed phototropic responses to the direction of blue light. Increasing degrees of vegetational shade promoted hypocotyl growth of WT plants. The Ih mutant showed no hypocotyl growth promotion by natural shade in glasshouse experiments (no UV-B, low water demand) and a reduced response (10-23% of the WT response, according to pretreatment conditions) in outdoor experiments (UV-B, high water demand).