Plant growth inhibitors isolated from sugarcane (Saccharum officinarum) straw

Several compounds related with plant defense and pharmacological activities have been isolated from sugarcane. Straw phytotoxins and their possible mechanisms of growth inhibition are largely unknown. A bioassay-guided fractionation of the phytotoxic constituents leachated from a sugarcane straw led to the isolation of trans-ferulic (trans-FA), cis-ferulic (cis-FA), vanillic (VA) and syringic (SA) acids. The straw leachates and their identified constituents significantly inhibited root growth of lettuce and four weeds. VA was more phytotoxic to root elongation than FA and SA. The identified phenolic compounds significantly increased leakage of root cell constituents, inhibited dehydrogenase activity and reduced chlorophyll content in lettuce. VA and FA inhibited mitotic index while SA increased cell division. Additive (VA-FA and FA-SA) and synergistic (VA-SA) interactions on root growth were observed at the response level of EC(25). Although the isolated compounds differed in their relative phytotoxic activities, the observed physiological responses suggest that they have a common mode of action. HPLC analysis indicated that sugarcane straw can potentially release 1.43 (ratio 2:1, trans:cis), 1.14 and 0.14mmolkg(-1) (straw dry weight) of FA, VA and SA, respectively. As phenolic acids are often found spatially concentrated in the top soil layers under plant straws, further studies are needed to establish the impact of these compounds in natural settings.     

Drazepinone, a trisubstituted tetrahydronaphthofuroazepinone with herbicidal activity produced by Drechslera siccans

When grown in a minimal-defined medium, a strain of Drechslera siccans, a pathogenic fungus isolated from seeds of Lolium perenne, produced phytotoxic metabolites. This strain is one of the best toxin producers among several grass pathogenic fungal strains collected and tested to find phytotoxins to be used as natural herbicides of monocot weeds. From the culture filtrates of D. siccans, we isolated a new phytotoxic trisubstituted naphthofuroazepinone, named drazepinone, and characterised it as a 3,5,12a-trimethyl-2,5,5a,12a-tetrahydro-1H-naphtho[2',3':4,5]furo[2,3-b]azepin-2-one. Assayed at 2 microg microl(-1) solution the novel metabolite proved to have broad-spectrum herbicidal properties, without antibacterial and antifungal activities, and low zootoxic activity. Its original chemical structure and the interesting biological properties make drazepinone a potential natural herbicide.     

Variability in the composition of anti-oxidant compounds in Echinacea species by HPLC

A fast and reliable HPLC method for the determination of caffeic acid derivatives (caftaric acid, chlorogenic acid, caffeic acid, cynarin, echinacoside and cichoric acid) in various species of the genus Echinacea has been developed. Extraction of root samples by magnetic stirring with 80% methanol aqueous solution at room temperature allowed the complete recovery of all compounds of interest. Root extracts were analysed on a reversed-phase column with gradient elution and photodiode array detection. Caffeic acid derivatives showed differential qualitative and quantitative distributions in Echinacea species. The total amount of phenolic compounds ranged from 33.95 to 0.32 mg/g. The highest contents of caffeic acid derivatives were found in E. paradoxa var. paradoxa, E. paradoxa var. neglecta and E. purpurea, followed by E. angustifolia var. angustifolia, E. simulata, E. pallida and E. laevigata, whilst E. tennesseensis, E. sanguinea and E. atrorubens had low amounts of phenolic compounds. The radical scavenging activities of methanolic extracts of roots of Echinacea species was evaluated in vitro using the DPPH* radical scavenging method. The EC50 values of the samples ranged from 122 to 1223 microg/mL. The radical scavenging activities of the root extracts were correlated with the content of phenolic compounds, with a correlation coefficient (r2) of 0.923.     

Fatty acids as natural specific inhibitors of the proto-oncogenic protein Shp2

Src homology-2 domain-containing protein tyrosine phosphatase (Shp2), a novel proto-oncogenic protein, is an important target in cancer therapy research. Approximately 2000 plant extracts were screened to find its natural specific inhibitors, with the ethyl acetate (EtOAc) active extract of the root of Angelica dahurica showing considerable inhibitory effects (IC(50)=21.6 mg/L). Bioguided isolation of EtOAc extract led to 13 compounds, including 10 fatty acids and derivatives. All these compounds were isolated from the plant for the first time. The inhibitory effects of these compounds on the enzyme activities of Shp2, VH1-related human protein (VHR), and hematopoietic protein tyrosine phosphatase (HePTP) were investigated. 8Z,11Z-Feptadecadienoic acid (4), 14Z,17Z-tricosadienoic acid (5), caffeic acid (9), and 2-hydroxy-3-[(1-oxododecyl) oxy]propyl-β-d-glucopyranoside (11) showed considerable selective inhibition of Shp2 activity. After treatment of HepG2 cells with the compounds, only compound 5, a polyunsaturated fatty acid, strongly induced poly (ADP-ribose) polymerase (PARP) cleavage in a dose- and time-dependent manner and increased the activities of caspase-3, caspase-8, and caspase-9 at 100 μM. Compound 5 also inhibited colony formation of HepG2 cells in a dose-dependent manner. Thus, this study reported fatty acids as specific Shp2 inhibitors and provided the molecular basis of one active compound as novel potential anticancer drug.     

Bioavailability and pharmacokinetics of caffeoylquinic acids and flavonoids after oral administration of Artichoke leaf extracts in humans

Extracts from artichoke leaves are traditionally used in the treatment of dyspeptic and hepatic disorders. Various potential pharmacodynamic effects have been observed in vitro for mono- and dicaffeoylquinic acids (e.g. chlorogenic acid, cynarin), caffeic acid and flavonoids (e.g. luteolin-7-O-glucoside) which are the main phenolic constituents of artichoke leaf extract (ALE). However, in vivo not only the genuine extract constituents but also their metabolites may contribute to efficacy. Therefore, the evaluation of systemic availability of potential bioactive plant constituents is a major prerequisite for the interpretation of in vitro pharmacological testing. In order to get more detailed information about absorption, metabolism and disposition of ALE, two different extracts were administered to 14 healthy volunteers in a crossover study. Each subject received doses of both extracts. Extract A administered dose: caffeoylquinic acids equivalent to 107.0 mg caffeic acid and luteolin glycosides equivalent to 14.4 mg luteolin. Extract B administered dose: caffeoylquinic acids equivalent to 153.8 mg caffeic acid and luteolin glycosides equivalent to 35.2 mg luteolin. Urine and plasma analysis were performed by a validated HPLC method using 12-channel coulometric array detection. In human plasma or urine none of the genuine target extract constituents could be detected. However, caffeic acid (CA), its methylated derivates ferulic acid (FA) and isoferulic acid (IFA) and the hydrogenation products dihydrocaffeic acid (DHCA) and dihydroferulic acid (DHFA) were identified as metabolites derived from caffeoylquinic acids. Except of DHFA all of these compounds were present as sulfates or glucuronides. Peak plasma concentrations of total CA, FA and IFA were reached within 1 h and declined over 24 h showing almost biphasic profiles. In contrast maximum concentrations for total DHCA and DHFA were observed only after 6-7 h, indicating two different metabolic pathways for caffeoylquinic acids. Luteolin administered as glucoside was recovered from plasma and urine only as sulfate or glucuronide but neither in form of genuine glucosides nor as free luteolin. Peak plasma concentrations were reached rapidly within 0.5 h. The elimination showed a biphasic profile.     

Phytotoxic potential of soils and wheat straw in rice rotation cropping systems of subtropical Taiwan

Using a wheat seed bio assay, the phytotoxicity of extracts obtained from wheat and rice rhizosphere soils was determined. The wheat rhizosphere soil extract was found to show phytotoxic effects. More allelopathic materials were found from the wheat-rice rotation soils than from the rice soil. Extracts obtained under basic conditions (pH 8) were found to be more inhibitory than those obtained by acid extraction (pH 5). Wheat straw was found also to contain phytotoxic substances. A comparison of two methods in concentrating the aqueous extracts, rotary evaporation and lyophilization, indicates that the former contained more substances with phytotoxic effects.     

Tyrolobibenzyls E and F from Scorzonera humilis and distribution of caffeic acid derivatives,lignans and tyrolobibenzyls in European taxa of the subtribe Scorzonerinae (Lactuceae,Asteraceae)

A chemosystematic study of the subtribe Scorzonerinae, a subtribe of the Lactuceae tribe of the Asteraceae family was performed, using the recently discovered tyrolobibenzyls as well as lignans and caffeic acid derivatives as diagnostic characters. In addition to the known compounds two new tyrolobibenzyls (E and F) were isolated and their structures were established by mass spectrometry and 1D and 2D NMR spectroscopy. Twenty four samples from rootstocks of seventeen different Scorzonerinae taxa, comprising members of three genera (Podospermum, Scorzonera, and Tragopogon), were analyzed. Tyrolobibenzyls A (1), B (2), C (5), D (3), E (6), and F (4) were identified in crude extracts by means of HPLC retention times, on-line UV spectra and on-line MS/MS spectra. Quantification of these compounds was performed by HPLC, using 2,2-bis-(4-hydroxyphenyl)-propane as an internal standard. Tyrolobibenzyls A-F were only detected in samples from Scorzonera humilis, while chlorogenic acid and 3,5-dicaffeoylquinic acid were detected in all samples investigated. In contrast, caffeoyl tartaric acid and cichoric acid were not detectable in any member of the subtribe Scorzonerinae.     

红背山麻杆叶的化学成分研究(Ⅰ)——酚酸类及相关化合物

采用80%丙酮提取石油醚萃取部位,利用凝胶、MCI及Toyopearl Butyl-650C柱色谱进行分离纯化得到10个酚酸类及相关化合物。根据化合物的波谱数据分析鉴定为水杨酸(1)、对羟基苯甲酸(2)、2,5-二羟基苯甲酸(3)、3,4-二羟基苯甲酸(4)、反-对香豆酸(5)、顺-对香豆酸(6)、咖啡酸(7)、咖啡酸甲酯(8)、没食子酸(9)、没食子酸甲酯(10)。其中化合物1~8、10均为首次从本属植物中分离得到。     

The selective allelopathic interaction of a pasture-forest intercropping in Taiwan

An allelopathic interaction of a pasture-forest intercropping system was evaluated by field and greenhouse experiments and by laboratory assays. A study site was situated in the farm of Hoshe Forestry Experiment Station at Nantou County, Taiwan. After deforestation of Chinese fir (Cunninghamia lanceolata), a split plot design of 8 treatments was set up: open ground without planting as control, planted with kikuyu grass, planted with kikuyu grass andAlnus formosana, planted with kikuyu grass andZelkova formosana, planted with kikuyu grass andCinnamomum camphora, planted withA. formosana, planted withZ. formosana, and planted withC. camphora. Field measurements showed that weeds grew luxuriantly six months after treatment in plots which had not been planted with kikuyu grass. However, the growth of weeds was significantly retarded but that of woody plants was not affected when the plots were planted with kikuyu grass. As compared with the tap water control, the aqueous leachate of kikuyu grass stimulated the seedling growth ofC. camphora andA. formosana, but the extract stimulated the growth ofC. camphora and inhibited that ofA. formosana. In contrast, the aqueous extracts of three hardwood plants exhibited variable inhibition on the root initiation of kikuyu grass, and the extract ofZ. formosana revealed the highest phytotoxic effect. The aforementioned extracts and leachates were bioassayed against seed germination and radicle growth of four test plants, namely annual rye grass, perennial rye gras, tall fescue, and Chinese cabbage and against seedling growth ofMiscanthus floridulus. The extract ofZ. formosana revealed the highest phytotoxic effect on the test species while that of kikuyu grass showed the least effect. By means of paper chromatography and high performance liquid chromatography, phytotoxic phenolics were identified and the amount of phytotoxins present was highest in the extract ofZ. formosana but was lowest in that of kikuyu grass. The degree of phytotoxicity and amount of phytotoxins was in good correlation, indicating that a selective allelopathic effect was involved. The findings suggest that allelopathy may contribute benefits in the intercropping system to reduce the need for herbicides and to lessen the labour cost for weed control.Paper No. 346 of the Scientific Journal Series of the Institute of Botany, Academia Sinica, Taipei, Taiwan, Republic of China. This study was supported in part by grants of Academia Sinica, Taipei, and Council of Agriculture, Executive Yuan of the Republic of China.     

Growth of Lesions Caused by Botrytis fabae on Field Bean Leaves in Relation to Foliar Bacteria, Non-enzymic Phytotoxins, Pectic Enzymes and Osmotica

Extracts from spreading chocolate spot lesions contained a heat-stable,water-soluble, ether- or ethanol-insoluble phytotoxic fraction.Elution from Sephadex G75 indicated that the molecular weightsof the toxic compounds were between 10000 and 30000 daltons.The toxins were adsorbed on DEAE Sephadex and eluted from itwith 0.1–0.2 M NaCl. Toxic activity was enhanced in solutionswith low osmotic potentials similar to those found in lesions.Controlling the growth of contaminating bacteria in lesionswith antibiotics appeared to reduce the levels of heat-stabletoxins extracted and to reduce the rate of increase in lesionsize. There were high levels of polygalacturonase (PG) activity inlesion extracts; large quantitites of PG, but little or no trans-eliminases,were produced by Botrytis fabae in liquid culture. A pectolyticstrain of Bacillus lentus was associated with trans-eliminasesin lesion extracts, and produced transeliminases, but not PG,in liquid culture. Activities of both heat-stable phytotoxins and of pectic enzymesmay depend on fungal isolate and types and populations of contaminatingbacteria. Botrytis fabae L., Bacillus, Vicia faba L., phytotoxins, pectic enzymes, chocolate spot     

Antimutagenic effect of phenolic acids

In the present study, the Salmonella typhimurium tester strain TA 100 was used in the plate-incorporation test to examine the antimutagenic potential of caffeic, ferulic and cichoric acids extracted from plant species of genera Echinacea (L) Moench, as well as of another phenolic acids, on 3-(5-nitro-2-furyl)acrylic acid (5NFAA) and sodium azide mutagenicity. All tested compounds possess antimutagenic activity. In the case of 5NFAA, the antimutagenic potency of tested compounds was in the order of gallic acid > ferulic acid > caffeic acid > syringic acid > vanillic acid. The mutagenic effect of sodium azide was inhibited by tested phenolic acids by about 20-35 %. The most effective compound, gallic acid inhibits this effect by 82 % in the concentration of 500 mug/plate. The only exception from favourable properties of tested phenolic acids is cichoric acid, which in the contrary significantly increased the mutagenic effect of 5NFAA.     

The chemotaxonomic and medicinal significance of phenolic acids in Arctopus and Alepidea (Apiaceae subfamily Saniculoideae)

The occurrence of (R)-3′-O-β-d-glucopyranosylrosmarinic acid, rosmarinic acid and caffeic acid in two important South African medicinal plants is reported for the first time. (R)-3′-O-β-d-Glucopyranosylrosmarinic acid and rosmarinic acid were isolated and identified in several samples from three species of the genus Arctopus L. (sieketroos) and three species of the genus Alepidea F. Delaroche (ikhathazo), both recently shown to be members of the subfamily Saniculoideae of the family Apiaceae. The compounds occur in high concentrations (up to 15.3 mg of (R)-3′-O-β-d-glucopyranosylrosmarinic acid per g dry wt) in roots of Arctopus. Our results provide a rationale for the traditional uses of these plants, as the identified compounds are all known for their antioxidant activity, with rosmarinic acid further contributing to a wide range of biological activities. Furthermore, we confirm the idea that (R)-3′-O-β-d-glucopyranosylrosmarinic acid is a useful chemotaxonomic marker for the subfamily Saniculoideae.     

Alkyl esters of hydroxycinnamic acids with improved antioxidant activity and lipophilicity protect PC12 cells against oxidative stress

Hydroxycinnamic acids (HCAs) are phenolic compounds present in dietary plants, which possess considerable antioxidant activity. In order to increase the lipophilicity of HCAs, with the aim of improving their cellular absorption and expansion of their use in lipophilic media, methyl, ethyl, propyl and butyl esters of caffeic acid and ferulic acid have been synthesized. All caffeate esters had a slightly lower DPPH IC(50) (13.5-14.5 μM) and higher ferric reducing antioxidant power (FRAP) values (1490-1588 mM quercetin/mole [mMQ/mole]) compared to caffeic acid (16.6 μM and 1398 mMQ/mole, respectively) in antioxidant assays. In contrast, ferulate esters were less active in DPPH (56.3-74.7 μM) and FRAP assays (193-262 mMQ/mole) compared to ferulic acid (44.6 μM and 324 mMQ/mole, respectively). Redox properties of HCAs were in line with their antioxidant capacities, so that compounds with higher antioxidant activities had lower oxidation potentials. Measurement of partition coefficients disclosed the higher lipophilicity of the esters compared to parent compounds. All esters of caffeic acid significantly inhibited hydrogen peroxide-induced neuronal PC12 cell death assessed by MTT assay at 5 and 25 μM. However, caffeic acid, ferulic acid and ferulate esters were not able to protect the cells. In conclusion, these findings suggest that alkyl esterification of some HCAs augments their antioxidant properties as well as their lipophilicity and as a consequence, improves their cell protective activity against oxidative stress. These compounds could have useful applications in conditions where oxidative stress plays a pathogenic role.     

Isolation and identification of a plant growth inhibitor from Tinospora tuberculata Beumee

Tinospora tuberculata Beumee has been used widely as a folk medicine and several bioactive compounds have been isolated. However, no herbicidal compound has been reported in this species. Therefore, we investigated the presence of phytotoxins in T. tuberculata. The aqueous methanol extracts of T. tuberculata inhibited the growth of roots and shoots of cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), timothy (Phleum pratense L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv.). The extract was then purified by several chromatographic runs with monitoring the inhibitory activity and the main phytotoxic substance was isolated. The chemical structure of the compound was determined by spectral data as syringin (4-[(1E)-3-Hydroxyprop-1-en-1-yl]-2,6-dimethoxyphenyl β-d-glucopyranoside). It inhibited the root and shoot growth of all test plant species at concentrations >10 µM. The concentrations required for 50 % inhibition of root and shoot growth of cress and lettuce ranged from 78.2 to 412 μM, and that of timothy and barnyard grass renged from 9.8 to 73.2 µM. Effectiveness of syringin on monocotyledonous (timothy and barnyard grass) plants was greater than that on dicotyledonous (cress and lettuce) plants. These results suggest that syringin may contribute to the allelopathic effect caused by the T. tuberculata extract.     

Uptake,translocation and persistence of mycotoxins in rice seedlings

The mycotoxins citrinin, patulin and terreic acid are absorbed by rice seedling roots and translocated to shoots. Ten day analysis of toxin treated plants showed persistence of citrinin, patulin and terreic acid. All three toxins at a concentration of 100 ppm showed phytotoxic activity indicating terreic acid in addition to citrinin and patulin as phytotoxins.     

The phytopathogenic fungus Alternaria brassicicola: Phytotoxin production and phytoalexin elicitation

The metabolites and phytotoxins produced by the phytopathogenic fungus Alternaria brassicicola (Schwein.) Wiltshire, as well as the phytoalexins induced in host plants, were investigated. Brassicicolin A emerged as the most selective phytotoxic metabolite produced in liquid cultures of A. brassicicola and spirobrassinin as the major phytoalexin produced in infected leaves of Brassica juncea (whole plants). In detached infected leaves of B. juncea, the main component was N′-acetyl-3-indolylmethanamine, the product of detoxification of the phytoalexin brassinin by A. brassicicola. In addition, the structure elucidation of three hitherto unknown metabolites having a fusicoccane skeleton was carried out and the antifungal activity of several plant defenses against A. brassicicola was determined.     

Bioactive steroids from Oryza sativa L

Rice is one of the most interesting crops in the world from both the social and the economic point of views. The monoculture practices along with the heavy use of herbicides are characteristic of modern agriculture and are inducing the appearance of tolerant and/or herbicide resistant weed biotypes. This is the case the world's main weed of rice barnyardgrass (Echinochloa crus-galli). Alternative strategies for weed suppression consist of the use of chemicals from rice due to necessity of obtaining new herbicides with new modes of action that could prevent resistance phenomena. In order to carry out a study that guides to the isolation of the most active compounds from rice, different extracts were achieved, and their activities evaluated. So, all the plant material was divided into three parts: fresh plant, dried plant, and fresh plant from Pluviotron. The aerial part was separated from roots in all cases and extracted in water, in organic solvents as well as with the Pluviotron device. The activity of the 12 extracts obtained was evaluated using a generalist bioassay, wheat etiolated coleoptiles bioassay, and a phytotoxic bioassay on barnyardgrass as target species. The bioactive extracts were fractionated and 15 compounds were isolated and identified by spectroscopic methods. Eight of these compounds were isolated for the first time in Oryza sativa. The most phytotoxic compounds on E. crus-galli were ergosterol peroxide and 7-oxo-stigmasterol. In the case of ergosterol peroxide the activity was higher than the commercial herbicide Logran. This is the first report of potential allelopathic activity of steroids on weeds based on their phytotoxicity.     

Inhibition of tillering in cereals by substituted 2-phenoxypropionic acids

The properties of various mono- and di-substituted analogues of 2-phenoxypropionic acid as inhibitors of tillering were investigated on wheat, barley and rice. Highest levels of activity were shown by (R)2-Cl,5-Cl, (R)2-Cl,5-F, and (R)2-Cl,5-methyl analogues. Few or no signs of phytotoxic effects (leaf chlorosis or necrosis) were evident on wheat or barley following spray application of these compounds. Rice was both more susceptible to inhibition of tillering and phytotoxic effects. However, almost complete inhibition of tillering was achieved by application of some compounds to rice with little or no phytotoxicity. Comparisons were made between the properties of these compounds and commercially used phenoxyacetic and phenoxypropionic herbicides and plant growth regulators. Dichlorprop inhibited tillering in rice, fenoprop in wheat and rice, and fluroxypyr in wheat, all without phytotoxic effects.     

Water-soluble inhibitor(s) of tumor respiration formed from ultraviolet-induced oxidation of linoleic and linolenic acids

Inhibition of Ehrlich ascites carcinoma respiration by aqueous extracts of oxidized linoleic or linolenic acid (aqueous emulsions UV-irradiated, 90 min) was associated entirely with relatively involatile compounds which were both thiobarbituric acid (TBA)-reactive and peroxidase-reactive. Inhibitory compounds were heat stable and migrated in thin-layer chromatography with aldehydes, "hydroperoxides," and TBA-reactive compounds. Peroxidase-catalyzed reduction of the "hydroperoxide" diminished the inhibition. At 4.7 x 10(-5) M "hydroperoxide" concentration, the residues from both linoleic and linolenic acid inhibited tumor oxygen consumption to a similar degree. However, at this concentration of "hydroperoxide" only the dried extract from linolenic acid was able to produce inhibition (100%) of aerobic glucose utilization by tumor cells. No glycolytic inhibition by the dried residue of oxidized linoleic acid was observed. At least 12 compounds (approximate chain length, 7C-13C) containing alpha,Beta-unsaturated carbonyl groups were isolated by gas-liquid chromatography (GLC) of dried extracts of oxidized linolenic acid. No single fraction inhibited tumor respiration, but the recombined mixture of all compounds caused complete respiratory inhibition of ascites tumor cells. Less material was required to inhibit oxygen consumption before than after GLC presumably because the more highly inhibitory components of the extract (along with "hydroperoxides" and TBA-reactive compounds) were lost during GLC. Extracts from oxidized linolenic acid were found to produce in all tumor cells cytoplasmic evaginations which were readily detected by phase microscopy.