Phenolic production and antioxidant properties of some Macedonian medicinal plants

Investigations have been made to study the production of phenolic compounds (total phenolics, flavonoids and phenylpropanoids) and total antioxidant capacity in 27 Macedonian traditional medicinal plants to improve its potential as a source of natural antioxidants. Antioxidant potential of plant extracts was analyzed by five different assays: cupric reducing antioxidant capacity (CUPRAC), phosphomolybdenum method (PM), reducing power (RP), 2,2-diphenyl-1-picrylhydrazyl (DPPH^·) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS^·+) radical scavenging activity. Origanum vulgare extract consistently exhibited the highest content of phenolic compounds and the strongest antioxidant capacity based on the tests performed, and can be proposed as a promising source of natural antioxidants. Melissa officinalis and Salvia ringens were also identified as valuable sources of antioxidant compounds. A positive linear correlation between antioxidant activity and total phenolics, flavonoids and phenylpropanoids indicates that these compounds are likely to be the main antioxidants contributing to the observed activities of evaluated plants. These findings suggest that the medicinal plants studied in this paper are good sources of bioactive compounds for the food and pharmaceutical industries.     

Phytochemical Analysis and Antioxidant Activity of <i>Crocus speciosus</i> Leaves

The numerous studies indicate leaves of plants are a rich source of bioactive compounds that can be a valuable source of compounds used in the pharmaceutical and cosmetic industries. Aim of this study was to investigate the chemical composition and the antioxidant property of Crocus speciosus leaves. Primary phytochemical screening of C. speciosus leaves revealed the presence of some following compound categories such as phenolic compounds, aminoacids, saponins, proteins, tannins, triterpenoids, glycosides, polysaccharides. The total flavonoids and phenolic compounds content were determined spectrophotometrically and by HPLC-DAD and HPLC-MS. Antiradical activity was determined by ABTS radical-cation scavenging method, spectrophotometrically. The total amount of flavonoids in C. speciosus leaves was 1.07 ± 0.02 mg RE/g (p < 0.05), the total amount of phenolic compounds was 0.41 ± 0.01 mg GAE/g (p < 0.05). By HPLC-DAD-MS analysis the presence of the mangiferin, chlorogenic acid, isoorientin, kaempferol, hyperoside, and isoquercitin was established for the first time in Crocus leaves. The antiradical activity of C. speciosus leaves extracts was 150.08 ± 4.5 μmol/g (p < 0.05) and its was mainly attributed to phenolic compounds content. The high amounts of flavonoids and antiradical activity in C. speciosus leaves suggests promising phytochemical and pharmacological study of this Crocus species.     

Biochemical Aspects of Parasitism by the Angiosperm Parasites: Phenolics in Parasites and Hosts

the contents of total phenolics in three parasitic angiosperms, Cuscuta species, Orobanche aegyptiaca and Dendrophthoe falcata and their respective hosts, were colorimetrieally determined. A biochemical comparison was made of the phenolics on the basis of the ability of alcoholic extracts of the tissues to inhibit amylose phosphorylase in vitro. High concentration of phenolics seemed to be a general feature of parasitic angiosperms. An increase in the concentration of the phenolics occurred in the tissues of infected hosts, in comparison with controls. the phenolics of Orobanche and mistletoe had inhibitory activity against amylose phosphorylase, but those of Cuscuta developed the inhibitory ability only when growing on hosts which themselves possessed inhibitory phenolics. the inhibitory activity of host phenolics was sometimes altered as a result of infection by parasite. Although the hosts often exerted some influence on the concentration and the inhibitory activity of phenolics in the parasites, there was no direct relationship between host and parasite phenolics. the sum of the phenolics in the tissues of parasite and the infected bost generally exceeded the phenolics in the tissues of the control host. The content of phenolics and their inhibitory activity did not appear to be directly related to the resistance of a host or to the extent of its susceptibility to parasite infection.     

Tentative Identification of Phytochemicals and Antioxidant Activities during Fruit-Ripening on <i>Chamaedorea radicalis</i> Mart.

This work aims to determine the phytochemical characterization of the pericarp of Chamaedorea radicalis Mart. fruit as a non-timber product with potential to obtain phytochemicals with potential applications in the industry. Fruit from C. radicalis were grouped in four ripening stages named as S1, S2, S3 and S4, according to maturity; S1 the most unripe stage and S4 the completely ripe stage. Determinations of total phenolic compounds, free radical scavenging activities and total flavonoid contents using spectrophotometric methods were done. Also, the tentative identification of phytochemicals during fruit ripening was done using UPLC-MS-MS. Total phenolic compound (TPC) content ranged from 7.24 to 12.53 mg gallic acid equivalents per gram of fresh weight (mg GAE/ g FW). Total flavonoids (TF) contents ranged from 0.163 to 0.23 mg of quercetin equivalents per g FW (mg QE/g FW). Free radical scavenging activity against DPPH and ABTS radicals varied from 40.80 to 53.68 and from 22.29 to 37.76 mmol Trolox equivalents g FW (mmol TE/g FW), respectively. Antioxidant assay in vitro by FRAP (ferric reducing antioxidant power) method showed that S3 was the highest level with antioxidant power while S4 was the lowest with Red ripeness stage showed the lowest contents for all determinations. Mass spectrometry allowed detection of 26 compounds, including phenolics, alkaloids and saponins. Afzelin, Kaempferol 3-neohesperidoside and the four saponins identified were present in all ripeness stages. Preliminary phytochemical identi- fication and the spectrophotometric determinations showed that the pericarp of C. radicalis presented antioxidants and compounds related to alkaloids, phenolics and saponins. The presence and abundance of each phytochemical regarding each ripeness stage should be considered.     

Phytochemical Analysis and Total Antioxidant Capacity of Rhizome,Above‐Ground Vegetative Parts and Flower of Three Iris Species

This study was aimed at investigating the phytochemical composition and antioxidant capacity of rhizomes, above‐ground vegetative parts and flowers of three Iris species: Iris humilis Georgi , Iris pumila L. and Iris variegata L. UHPLC‐Orbitrap MS analysis was used for determination of phytochemical profile. Total pigments, phenolics, flavonoids, soluble sugars and starch content as well as ABTS antioxidant capacity were also determined. In total, 52 phenolics compounds were identified with 9 compounds (derivatives of iriflophenone, apigenin C‐glycosides, luteolin O‐glycoside, isoflavones derivatives of iristectorigenin, dichotomitin, nigracin and irilone) never reported before in Iris spp. Differences in phenolic composition profile, pigments, soluble sugar, starch, total phenolics and flavonoids content and total antioxidant capacity were found among Iris species and different part of plants. Significant correlation between total phenolic content and antioxidant capacity was determined. The obtained results are comparable with those obtained for medical plants. These findings could be useful for fingerprinting characterization of Iris species and estimation of possible use in pharmaceutical industries.     

Antioxidant properties and phenolic profiling by UPLC-QTOF-MS of Ajwah,Safawy and Sukkari cultivars of date palm

Date palm (P. dactylifera) plays a vital role in ethnomedicinal practices in several parts of the world. There are over 2000 cultivars of date palm that differ in chemical composition and extent of bioactivity. The present study was undertaken to comparatively evaluate the antioxidant potential of three cultivars of date palm (Ajwah, Safawy and Sukkari) from Saudi Arabia and analyze their phenolic constituents in order to draw a rationale for their activity. Antioxidant activities of the date cultivars were evaluated by different quantitative methods including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging assay, total antioxidant capacity, reducing power, total phenolic (TPC), flavonoid (TFC) and tannin content (TTC), while qualitative phenolic composition was determined using ultra performance liquid chromatography coupled to quadropole time of flight mass spectrometry (UPLC-QTOF-MS). All the three date extracts showed good DPPH radical scavenging (IC₅₀ 103–177 μg/mL) and hydroxyl radical scavenging (IC₅₀ 1.1–1.55 mg/mL) activity and total antioxidant capacity (IC₅₀ 87–192 μg/mL). The reducing power was also comparable to that of ascorbic acid, used as standard in above experiments. All the three samples contain significant amount of major antioxidant components (phenolic, flavonoid and tannin) that successfully correlates with the results of radical scavenging assays. UPLC-QTOF-MS revealed a total of 22 compounds in these date cultivars classified into common phenolics, flavonoids, sterols and phytoestrogens. Significant variation in the degree of antioxidant activity of these three date cultivars can be attributed to the difference in the content and composition of phenolic compounds.     

Quantification of polyphenolic antioxidants and free radical scavengers in marine algae

While the health benefits of antioxidant compounds from terrestrial plants are widely accepted in Western counties, there is less recognition of the health benefits of marine algal antioxidant compounds. Oceans are an abundant source of biomaterials, with many natural antioxidants derived from marine algae being investigated as potential anti-aging, anti-inflammatory, anti-bacterial, anti-fungal, cytotoxic, anti-malarial, anti-proliferative, and anti-cancer agents. The aim of this work was to quantify and compare polyphenolic content and free radical scavenging activity of algal extracts using normal phase and reverse phase thin layer chromatography. Post-chromatographic derivatization with neutral ferric chloride (FeCl₃) solution and with 2,2-diphenyl-1-picrylhydrazyl (DPPH·) free radical were used to assess total polyphenolic content and free radical scavenging activities in algal samples. Total phenolic content quantified on normal phase plates was correlated to phenolic content established on reverse phase plates. Similarly, free radical scavenging activity established on normal phase and reverse phase plates were in good agreement. However, although free radical scavenging activities determined on normal phase plates were highly correlated with polyphenolic content, this correlation was low for reverse phase plates. Lipophilic reversed phase TLC plates do not effectively separate mixtures of highly polar compounds like flavonoids, phenolic compounds and their glucosides. Thus, although reversed phase plates are recommended for assessment of free radical scavengers, as they do not influence the free radical-antioxidant reaction, they may not provide the best separation of polar phenolic compounds, especially flavonoids, and therefore may not accurately quantify polyphenolic content and free radical scavenging potential.     

低海拔地区黑苦荞酚类物质含量、组成及抗氧化活性研究

为探究黑苦荞的市场利用价值,该研究选择种植于湖北江汉平原低海拔地区的川荞1号和九江苦荞作为材料,分析苦荞籽粒中游离酚、结合酚、总酚、游离黄酮、结合黄酮和总黄酮的含量,利用DPPH自由基法、ABTS自由基法和铁离子还原抗氧化法(FRAP)三种抗氧化测试模型综合评价其体外抗氧化活性,并运用高效液相色谱(HPLC)技术对其酚类物质的组成进行鉴定。结果表明:(1)川荞1号籽粒的总酚和总黄酮含量显著高于九江苦荞,分别为27.38 mg GAE·g~(-1)DW、31.46 mg RE·g~(-1)DW和12.71 mg GAE·g~(-1)DW、14.68 mg RE·g~(-1)DW;其中游离酚与游离黄酮含量显著高于结合酚与结合黄酮含量,均占总酚和总黄酮含量的79%以上,且九江苦荞中结合酚和结合黄酮的含量高于川荞1号。(2)苦荞籽粒中酚类物质主要由芦丁、槲皮素、表儿茶素、山奈酚、山奈酚-3-芸香糖苷和槲皮素-3-O-芸香糖苷-3'-O-吡喃葡萄糖苷等黄酮类化合物组成,其中游离酚以芦丁和槲皮素为主,结合酚以表儿茶素和芦丁为主。(3)苦荞籽粒提取物均具有一定的抗氧化活性,黑苦荞川荞1号游离态DPPH、ABTS和FRAP抗氧化能力值分别为30.14、11.03、18.84 mg TE·g~(-1)DW,高于九江苦荞,而结合态三种抗氧化能力值低于九江苦荞,但黑苦荞川荞1号总抗氧化能力显著高于九江苦荞。在低海拔地区江汉平原,种植的黑苦荞川荞1号籽粒具有较高含量的酚类物质,符合后续的食品加工的生产要求,市场开发前景广阔。     

Influence of chemical profiles of host plants on the infestation diversity ofRetithrips syriacus

The onset of biotic stress in the host plants as a result of increased insect population size leads to enhanced levels of secondary metabolites and associated phenolic enzyme activity. Of the three host plants examined, viz.Ricinus communis (castor),Eucalyptus globulus (eucalyptus) andManihot utilissima (tapioca), castor was the host most preferred byRetithrips syriacus. Despite the fact that tapioca had the highest levels of secondary compounds, thrips infestation persisted. However, fecundity and growth were reduced because of the relatively high levels of primary metabolites. Gallic acid was found to be the most toxic of the phenolic acids, followed by pyrogallol, resorcinol, phloroglucinol and vanillic acid. The less toxic phenolic acids and flavanoids were detected in leaves that harboured thrips, while the preponderance of gallic acid was found in uninfested hosts. Thus the interaction ofRetithrips syriacus with the hosts is governed essentially by the biochemical profiles of its hosts, which tend to be altered subsequent to infestation, thus manifesting induced resistance through enhanced production of phenolics     

Host-mediated volatile polymorphism in a parasitic plant influences its attractiveness to pollinators

Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as “ornithophilic” by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.     

The effect of host mycorrhizal status on host plant–parasitic plant interactions

Two pot experiments were conducted to examine three-level interactions between host plants, mycorrhizal fungi and parasitic plants. In a greenhouse experiment, Poa annua plants were grown in the presence or absence of an AM fungus (either Glomus lamellosum V43a or G. mosseae BEG29) and in the presence or absence of a root hemiparasitic plant (Odontites vulgaris). In a laboratory experiment, mycorrhizal infection (Glomus claroideum BEG31) of Trifolium pratense host plants (mycorrhizal versus non-mycorrhizal) was combined with hemiparasite infection (Rhinanthus serotinus) of the host (parasitized versus non-parasitized). Infection with the two species of Glomus had no significant effect on the growth of P. annua, while hemiparasite infection caused a significant reduction in host biomass. Mycorrhizal status of P. annua hosts (i.e. presence/absence of AM fungus) affected neither the biomass nor the number of flowers produced by the attached O. vulgaris plants. Infection with G. claroideum BEG31 greatly increased the biomass of T. pratense, but hemiparasite infection had no effect. The hemiparasitic R. serotinus plants attached to mycorrhizal hosts had higher biomass and produced more flowers than plants growing with non-mycorrhizal hosts. Roots of T. pratense were colonized by the AM fungus to an extent independent of the presence or absence of the hemiparasite. Our results confirm earlier findings that the mycorrhizal status of a host plant can affect the performance of an attached root hemiparasite. However, improvement of the performance of the parasitic plant following attachment to a mycorrhizal host depends on the extent to which the AM fungi is able to enhance the growth of the host. Accepted: 23 February 2001     

Profiling and Elucidation of the Phenolic Compounds in the Aerial Parts of Gynura bicolor and G. divaricata Collected from Different Chinese Origins

Gynura bicolor and G. divaricata are not only known to be nutritive as cultured vegetables, but also beneficial as folk medicines in East Asia. As demonstrated by the current phytochemical knowledge, the genus Gynura is a promising source of phenolics with multiple medicinal activities. To expand this phytochemical knowledge, the phenolic secondary metabolites of G. bicolor and G. divaricata were studied. From the aerial parts of these two species, collected in five different Chinese locations, two fractions of phenolic compounds with different polarity were obtained by extraction and chromatographic separation. Using UPLC/MS/MS analysis, a total of 53 phenolics were either identified by comparison with respective reference compounds or tentatively characterized by their chromatographic behavior, UV‐absorption patterns, and MS fragmentations. Some naturally existing positional isomers of O‐caffeoylquinic acid, O‐p‐coumaroylquinic acid, O‐feruloylquinic acid, and dicaffeoylquinic acid as well as their methyl esters were qualitatively characterized by their specific fragmentation patterns in targeted MS/MS. In addition, the aerial parts of the two Gynura species contained kaempferol, quercetin oligoglycosides, and a variety of derivatives of benzoic acid, hydroxycinnamic acid, and caffeic acid. Furthermore, the distribution of phenolic compounds in the two species from different Chinese origins was discussed. Finally, an investigation of the total phenolic content and in vitro antioxidant activity of the various phenolic fractions was completed, to evaluate the potential of the extracts of these species for medicinal development. The free‐radical‐scavenging activities of the extracts derived from plants originating from Nanjing were proven to be higher than those of the other extracts, which correlated well with their total phenolic content.     

Phenolic Profile of Artemisia alba Turra

The aim of this study was to evaluate flower and leaf methanol extracts of Artemisia alba Turra for their total phenolic and flavonoid contents, antioxidant capacity and to investigate their phenolic composition. The flower extract was richer in total phenolics and flavonoids and possessed higher antioxidant activity through DPPH and ABTS assays. The UHPLC‐PDA‐MS analysis of the flower and leaf methanol extracts revealed similar phenolic profile and allowed identification of 31 phenolic compounds (flavonoids, coumarins, and phenolic acids) by comparison with the respective reference compounds or tentatively characterized by their chromatographic behavior, UV patterns, and MS fragmentations. The presence of hispidulin, jaceosidin, desmethoxycentaureidin, and dicaffeoyl esters of quinic acid in A. alba is reported herein for the first time. The distribution of flavonoids in A. alba from different origins was discussed from chemotaxonomic point of view.     

3种百合鳞茎中多酚类物质的抗氧化活性分析

以野生百合渥丹、山丹和传统食用的兰州百合为研究对象,对其鳞茎中多酚类物质、11种单体酚的含量及抗氧化活性(ABTS自由基、超氧阴离子、羟自由基的清除能力,铜离子还原能力以及抑制脂质过氧化活性)进行了分析。结果表明:两种野生百合鳞茎中的多酚类物质含量及抗氧化活性均显著高于兰州百合。3种百合鳞茎中单体酚的种类也有所不同,但均含有没食子酸、矢车菊素-3-芸香糖苷、儿茶素、表儿茶素、杨梅酮、芦丁、对香豆酸、山奈酚。相关性分析显示,除对羟自由基的清除力外,各酚类物质总量与不同抗氧化指标之间呈显著正相关关系。试验结果认为,野生百合鳞茎可作为天然抗氧化资源应用于食品和医药业,具有一定的开发应用前景。     

Structure-radical scavenging activity relationships of phenolic compounds from traditional Chinese medicinal plants

Traditional Chinese medicinal plants associated with anticancer contain a wide variety of natural phenolic compounds with various structural features and possessing widely differing antioxidant activity. The structure-radical scavenging activity relationships of a large number of representative phenolic compounds (e.g., flavanols, flavonols, chalcones, flavones, flavanones, isoflavones, tannins, stilbenes, curcuminoids, phenolic acids, coumarins, lignans, and quinones) identified in the traditional Chinese medicinal plants were evaluated using the improved ABTS*+ and DPPH methods. Different categories of tested phenolics showed significant mean differences in radical scavenging activity. Tannins demonstrated the strongest activity, while most quinones, isoflavones, and lignans tested showed the weakest activity. This study confirmed that the number and position of hydroxyl groups and the related glycosylation and other substitutions largely determined radical scavenging activity of the tested phenolic compounds. The differences in radical scavenging activity were attributed to structural differences in hydroxylation, glycosylation and methoxylation. The ortho-dihydroxy groups were the most important structural feature of high activity for all tested phenolic compounds. Other structural features played a modified role in enhancing or reducing the activity. Within each class of phenolic compounds, the structure-activity relationship was elucidated and discussed. This study reveals the structure-activity relationships of a large series of representative natural phenolic compounds more systematically and fully than previous work. Structure-radical scavenging activity relationships of some natural phenolics identified in the medicinal plants were evaluated for the first time.     

Effects of drought and N level on the interactions of the root hemiparasite Rhinanthus alectorolophus with a combination of three host species

• Increasing nitrogen deposition and more frequent drought events are likely to change plant interactions in natural grasslands. Both factors may also influence the interactions between hemiparasitic plants, regarded as keystone species in many grasslands, and their host species.
• We grew a combination of three suitable hosts, a grass, a forb and a legume, with and without the hemiparasite Rhinanthus alectorolophus at three levels of nitrogen (N) and two levels of water availability in a factorial design.
• Biomass of the hemiparasite and host community increased with N level and was reduced by drought to a similar degree. Larger plants in fertilised pots started to wilt earlier, and the presence of a hemiparasite further increased drought sensitivity. The hemiparasite strongly reduced biomass of the host community and overall productivity, and affected the competitive balance among host plants because it particularly reduced biomass of the dominant grass. These effects were the opposite of those of high N. The hemiparasite increased the root mass fraction of the hosts at all levels of N and water availability, indicating that the effect of the hemiparasite on the hosts was mainly due to loss of belowground resources.
• Our results indicate that hemiparasites will not always respond more strongly to increased N availability and drought than autotrophic plants, and that hemiparasites can have similarly strong effects on grassland communities as soil fertility and drought. By preferentially attacking dominant species the hemiparasites might alleviate the negative effects of nutrient enrichment on grassland diversity.

     

Phenolic composition and antioxidant properties of some traditionally used medicinal plants affected by the extraction time and hydrolysis

Introduction – Polyphenolic phytochemicals in traditionally used medicinal plants act as powerful antioxidants, which aroused an increasing interest in their application in functional food development. Objective – The effect of extraction time (5 and 15 min) and hydrolysis on the qualitative and quantitative content of phenolic compounds and antioxidant capacity of six traditionally used medicinal plants (Melissa officinalis L., Thymus serpyllum L., Lavandula officinalis Miller, Rubus fruticosus L., Urtica dioica L., and Olea europea L.) were investigated. Methodology – The content of total phenols, flavonoids, flavan‐3‐ols and tannins was determined using UV/Vis spectrophotometric methods, while individual phenolic acids, flavones and flavonols were separated and detected using HPLC analysis. Also, to obtain relevant data on the antioxidant capacity, two different assays, (2,2‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid) (ABTS) radical scavenging and ferric reducing/antioxidant power (FRAP) assays were used. Results – The extraction efficiency of phenolics, as well as the antioxidant capacity of plant extracts, was affected by both prolonged extraction and hydrolysis. The overall highest content of phenolic compounds was determined in hydrolyzed extract of blackberry leaves (2160 mg GAE/L), followed by the non‐hydrolyzed extract of lemon balm obtained after 15 min of extraction (929.33 mg GAE/L). The above extracts also exhibited the highest antioxidant capacity, while extracts of olive leaves were characterized with the lowest content of phenolic compounds, as well as the lowest antioxidant capacity. The highest content of rosmarinic acid, as the most abundant phenolic compound, was determined in non‐hydrolyzed extract of lemon balm, obtained after 15 min of extraction. Although the hydrolysis provided the highest content of polyphenolic compounds, longer extraction time (15 min) was more efficient to extract these bioactives than shorter extraction duration (5 min). Conclusion – The distribution of detected phenolic compounds showed a wide variability with regard to their botanical origin. Examined medicinal plants showed to be a valuable supplement to a daily intake of bioactive compounds. Copyright © 2010 John Wiley & Sons, Ltd.     

Phenolic acids act as signaling molecules in plant-microbe symbioses

Phenolic acids are the main polyphenols made by plants. These compounds have diverse functions and are immensely important in plant-microbe interactions/symbiosis. Phenolic compounds act as signaling molecules in the initiation of legumerhizobia symbioses, establishment of arbuscular mycorrhizal symbioses and can act as agents in plant defense. Flavonoids are a diverse class of polyphenolic compounds that have received considerable attention as signaling molecules involved in plant-microbe interactions compared to the more widely distributed, simple phenolic acids; hydroxybenzoic and hydroxycinnamic acids, which are both derived from the general phenylpropanoid pathway. This review describes the well-known roles attributed to phenolic compounds as nod gene inducers of legume-rhizobia symbioses, their roles in induction of the GmGin1 gene in fungus for establishment of arbuscular mycorrhizal symbiosis, their roles in inducing vir gene expression in Agrobacterium, and their roles as defense molecules operating against soil borne pathogens that could have great implications for rhizospheric microbial ecology. Amongst plant phenolics we have a lack of knowledge concerning the roles of phenolic acids as signaling molecules beyond the relatively well-defined roles of flavonoids. This may be addressed through the use of plant mutants defective in phenolic acids biosynthesis or knock down target genes in future investigations.Key words: Agrobacterium sp., flavonoids, legume-rhizobium symbioses, phenolic acids, plant defense, vesicular arbuscular mycorrhiza     

荸荠皮提取物对DPPH自由基清除活性

采用70%丙酮溶液对荸荠皮中抗氧化物质进行提取,得到红棕色浸膏。通过定性及定量方法分析了荸荠皮提取物中可能存在的具有抗氧化活性的物质;采用DPPH自由基法测定了荸荠皮提取物对DPPH自由基的清除能力。结果显示,荸荠皮提取物中含有多酚类和黄酮类等化合物,其多酚含量为3.31%(w/w,以干物质计)。DPPH自由基法显示,荸荠皮提取物具有一定的清除DPPH自由基能力,其清除能力与提取物浓度之间显示出良好的剂量-效应关系。该提取物(IC50值为130.37 ppm)对DPPH自由基清除能力略低于BHT(IC50值为94.16 ppm)。     

Antioxidant activity and cytotoxicity of methanol extracts from aerial parts of Korean salad plants

The aim of this investigation was to determine the content of total phenolics, antioxidant activity and cytotoxicity of methanol extracts from the aerial parts of 11 Korean medicinal salad plants. The highest total phenolic content of the methanol extracts was found in Aster scaber (17.1 mg 100 g(-1)), followed by Ixeris dentate (16.4 mg 100 g(-1)), Aster yomena (12.0 mg 100 g(-1)) and Sedum sarmentosum (9.1 mg 100 g(-1)) of FW. Methanol extracts of Ixeris dentate and Aster scaber at 50 microg mL(-1) exhibited the highest DPPH radical scavenging activity by 86.4 and 83.3%, respectively. It was registered a dose-dependent increase of DPPH free radical scavenging activity. Total phenolic content of the studied plant extracts was correlated with the DPPH radical scavenging activity. It was found by means of MTT assay, that cytotoxicity of the methanol extracts was the highest against HCT-116. Methanol extracts from Petasites japonicus (IC(50)<25.0 microg mL(-1)) showed the highest activity against HCT-116, following by Angelica gigas (34.75 microg mL(-1)), Erythronium japonicum (44.06 microg mL(-1)), and Aster scaber (54.87 microg mL(-1)). In conclusion, the studied salad plants have high total phenolics content and high antioxidant activity. These plants dose-dependently increased DPPH free radical scavenging activity. The total phenolics level was highly correlated with the free radical scavenging activity. Most of the studied salad plants have potent cytotoxicity activity. The results of this investigation suggest that the extracts of studied salad plants could be an addition to basic medicine for some diseases.