Impact of Continuous Cropping on Soil Phenolic Acid Substances and Research Progress on Continuous Cropping Obstacle Reduction Techniques

At present,long-term continuous cropping in agricultural production has formed a relatively common development trend.With the increase of continuous cropping years,soil phenolic acids are also affected to varying degrees.This paper summarized the effects of continuous cropping on soil phenolic acids and the research progress of continuous cropping obstacle reduction techniques,aiming at providing theoretical basis and technical support for the research of continuous cropping obstacle reduction techniques and promoting the healthy and sustainable development of modern agriculture.

Polyphenols,Ascorbic Acid and Carotenoids Contents and Antioxidant Properties of Habanero Pepper(Capsicum chinense)Fruit

Their high bioactive compounds content and importance as dietary antioxidants has increased interest in Capsicum fruit. The fruit of seven Capsicum chinense Jacq. var. habanero genotypes grown in Yucatan, Mexico, were analyzed to quantify their phenolic compounds, carotenoids and ascorbic acid contents, and to measure their free radical scavenging (ABTS assay) and antioxidant activities (β-carotene/linoleic acid assay). Phenolics (20.54 to 20.75 mg/100 g sample), carotenoids (1.00 to 1.26 mg/100 g sample) and ascorbic acid contents (187.24 to 281.73 mg/100 g sample) varied between genotypes. Trolox equivalent antioxidant capacity (TEAC) ranged from 1.55 to 3.23 mM/mg sample. During the 120-min decolorization trial, antioxidant capacity decreased over time in the studied genotypes. Values ranged from 36%to 57% β-carotene bleaching during the first 30 minutes. Fruit from all seven studied genotypes are good antioxidant sources and hold promise as natural ingredients in functional foods.

Comparison between Sulfuric Acid-phenol and Sulfuric Acid-anthrone Methods Used for Determination of Polysaccharides in Shoots of Aralia elata (Miq.) Seem.

Sulfuric acid-phenol and sulfuric acid-anthrone methods were used to detect polysaccharide content in shoots of Aralia elata（ Miq.） Seem.,and the conversion factor to glucose was measured with refined polysaccharides. Comprehensive evaluation was carried out by linear relationship,precision,reproducibility,stability and recovery rate. The results showed that the linear relationship between glucose concentration and absorbance was good when glucose concentration was0-40 μg/ml,and the average recovery rate was equal to or higher than 97. 00% with good reproducibility（ RSD 〈 1. 60%,n = 5）. It revealed that the two methods were accurate and reliable,and suitable for the determination of polysaccharide content in the shoots of A. elata. Polysaccharide content detected by sulfuric acid-phenol and sulfuric acid-anthrone methods was 19. 31% and 20. 40% respectively.

SORPTION OF PHENOL ONTO GEL-TYPE CROSSLINKED POLYSTYRENEISOCYANURIC ACID RESIN

Spherical crosslinked polystyrene-isocyanuric acid resin was synthesized by reaction of chloromethylated polystyrene with isocyanuric acid. The sorption isotherms of phenol from aqueous solution and cyclohexane solution onto the resin were measured. It is of interest to notice that the resin sorbed phenol efficiently though its specific surface area was 0 and did not swell in water, and the sorption capacity.from aqueous solution was close to that of phenol onto XAD-4 at the same equilibrium concentration. Sorption enthalpies calculated from the isotherms according to the Clausius-Clapeyron equation were -2I~ -25lJ/mol and -39~ -41kJ/mol respectively. These values implied that the sorption processes were based on hydrogen bonding. In addition the details of the hydrogen bonding between the active sites of the resin and phenol were suggested.

A change of phenolic acids content in poplar leaves induced by methyl sali-cylate and methyl jasmonate

The contents of seven different phenolic acids such as gallic acid, catechinic acid, pyrocatechol, caffeic acid, coumaric acid, ferulic acid and benzoic acid in the poplar leaves （Populus Simonii×Populus Pyramibalis c.v and Populus deltoids） suffocated by Methyl jasmonate （MeJA） and Methyl salicylate （MeSA） were monitored for analyzing their functions in interplant communications by using high-pressure liquid chromatography （HPLC）.The results showed that the contents of phenolic acids had obviously difference in leaves exposed to either MeSA or MeJA.When P.deltoides leaves exposed to MeJA or MeSA, the level of gallic acid, coumaric acid, caffeic acid, ferulic acid and benzoic acid was increased, gallic acid in leaves treated with MeJA comes to a peak at 24 h while to a peak at 12-d having leaves treated with MeSA.When P.Simonii ×P.Pyramibalis c.v leaves were exposed to MeJA or MeSA, the level of gallic acid, pyrocatechol and ferulic acid was increased; The catechinic acid and benzoic acid had a little drop; The caffeic acid and coumaric acid were undetected in both suffocated and control leaves.This changed pattern indicated that MeJA and MeSA can act as airborne signals to induce defense response of plants.

Two New Phenolic Carboxylic Acid Esters from Opuntia vulgaris

Two new phenolic carboxylic acid esters n-butyl eucomate(1) and methyl eucomate (2) and six known compounds eucomic acid(3), 3-β-acetyl-taraxerol (4), friedelin(5),lupenone(6),methyl linoleate(7) and methyl oleate(8) were isolated from the stems of Opuntia vulgaris Mill(Cactaceae). Their structures were determined on the basis of spectral methods. Compounds 3,4,6,7,8 were isolated for the first time from this plant.

Biochemical changes in phenols,flavonoids,tannins,vitamin E,β-carotene and antioxidant activity during soaking of three white sorghum varieties

Objective:To investigate the changes in total phenols,flavonoids,tannins,vitamin E, β-carotene and antioxidant activity during soaking of three white sorghum varieties.Methods: The changes in total phenols,total ilavonoids,tannins,phenolic acids compounds,flavonoid components,vitamin E,P-carotene and antioxidant activity during soaking of sorghum grains were determined.Results:Total phenols,total flavonoids,tannins,vitamin E,P-carotene and antioxidant activity in raw sorghum were ranged from 109.21 to 116.70,45.91 to 54.69,1.39 to 21.79 mg/100 g,1.74 to 5.25,0.54 to 1.19 mg/kg and 21.72%to 27.69%and 25.29%to 31.97%,respectively. The above measured compounds were significantly decreased after soaking.p-Hydroxybenzoic acid,vanillic acid,syringic acid and cinnamic acid represent the major phenolic acids in Dorado variety.While ferulic acid,p-coumaric acid,gallic acid and caffeic acid represent the major phenolic acids in Shandaweel-6.On the other hand,protocatechuic acid represents the major phenolic acids in Giza-15.Regarding flavonoids components,Dorado was the highest variety in kampferol and naringenin while Shandaweel-6 was the highest variety in luteolin, apigenin,hypersoid,quercelin and christen.Finally,Giza-15 was the highest variety in catechin. Phenolic acids,flavonoid compounds and antioxidant activities were decreased after soaking. Conclusions:Sorghum varieties have moderate quantities from total phenols,total flavonoids, tannins,phenolic acids compounds,flavonoid components,vitamin E,P-carotene and antioxidant activity which decreased after soaking.

Induced Effects of Exogenous Phenolic Acids on Allelopathy of a Wild Rice Accession(Oryza longistaminata,S37)

Four exogenous phenolic acids, including salicylic acid, fumalic acid, p-coumaric acid and p-hydroxybenzonic acid, were used to investigate the regulatory effects on allelopathy of a wild rice accession of S37 （Oryza Iongistaminata）, which is a known allelopathic rice. The four exogenous phenolic acids induced the enhancement of the allelopathic potential of wild rice S37 in target weeds though the weed-suppressive activities were low, and the inducible effects were dependent on the specific phenolic acid, concentration and treatment time. After foliar application of exogenous phenolic acids, the inhibition rates for plant height, root length and fresh weight of barnyard grass （Echinochioa crus-galli） were significantly higher than those of the control. Especially at the concentration of 100 mg/L, the inhibition rates for plant height and fresh weight of barnyard grass by fumalic acid were 38.12% and 26.31% higher than those of the control, showing that fumalic acid was more effective compared with other phenolic acids in inhibiting monocotyledon weed growth. Furthermore, the weedsuppressive activity of aqueous extract from the leaves of wild rice S37 treated with exogenous phenolic acids was increased, and it peaked at 48 h after the treatment with the aqueous extract, and then gradually declined.

Catalytic ozonation of phenol and oxalic acid with copper-loaded activated carbon

A novel heterogeneous catalytic ozonation process in water treatment was studied, with a copper-loaded activated carbon （Cu/AC） that was prepared by an incipient wetness impregnation method at low temperature and tested as a catalyst in the ozonation of phenol and oxalic acid. Cu/AC was characterized using XRD, BET and SEM techniques. Compared with ozonation alone, the presence of Cu/AC in the ozonation processes significantly improves the degradation of phenol or oxalic acid. With the introduction of the hydroxyl radical scavenger, i.e., turt-butanol alcohol （t-BuOH）, the degradation efficiency of both phenol and oxalic acid in the Cu/AC catalyzed ozonation process decreases by 22% at 30 min. This indicates that Cu/AC accelerates ozone decomposition into certain concentration of hydroxyl radicals. The amount of Cu（II ） produced during the reaction of Cu/AC-catalyzed ozonation of phenol or oxalic acid is very small, which shows that the two processes are both heterogeneous catalytic ozonation reactions.

Changes of Polyphenols in Tobacco Leaves During the Flue-Curing Process and Correlation Analysis on Some Chemical Components

The changes of polyphenols in tobacco leaves during the flue-curing process and correlation analysis on some chemical components were studied. Leaf samples were taken from different tobacco-producing regions in Henan Province, China. The results indicated that the content of total phenols increased during the first 24 h of curing, and then decreased. It reached the lowest value at 72 h of curing and increased rapidly after that. The content of chlorogenic acid also increased during 0-24 h of curing. But the lowest point occurred at 60 or 72 h of curing and then it increased till the end of the curing process. The content of mtin generally increased with curing, and showed little fluctuations. The changes of PPO and POD activity were the opposite. Rutin was found to have a highly significant positive correlation with total sugar （r=0.822^＊＊）, but a highly significant negative correlation with starch, nicotine, and protein.

Addition Mechanisms of Phenol toward Formaldehyde under Acidic Condition: a Theoretical Investigation

The reaction mechanisms of phenol with formaldehyde in the first and second addition at the ortho- and para-position in acid solution were theoretically investigated at the PW91/DNP level with solvent effects included. The reaction of phenol with protonated methanediol firstly forms an adduct intermediate, via a SN2 mechanism with a water molecule as the leaving group. From the adduct intermediate, there are two reaction channels involving a proton transfer to form the addition products. One is that a proton directly transfers via a four-membered ring transition state with a notable energy barrier （Four-member mechanism）. Another mechanism involving a water molecule as catalyst to mediate the proton transfer （WCP mechanism）, is a barrierless process, indicating that the formation of the adduct intermediate, the first reaction step, is rate-limiting. The reaction products are free hydroxymethyl phenols and/or hydroxybenzy carbocation （HOC6H4CH2＋） which plays an important role in the following formation of methylene and methylene ether linkages. The second addition reactions between formaldehyde and hydroxymethyl phenol at all possible reaction sites of the phenol ring in acid solution were also investigated and discussed.

The effects of phenolic acid on nitrogen metabolism in Populus 3 euramericana ‘Neva’

The declines in soil fertility and productivity in continuously cropped poplar plantations axe related to phenolic acid accumulation in the soil. Nitrogen is a vital life element for poplar and whether the accumulation of phenolic acid could influence nitrogen metabolism in poplar and thereby hinder continuous cropping is not clear. In this study, poplar cuttings of Populus × euramericana ‘Neva＇ were potted in vermiculite, and phenolic acids at three concentrations （032, 0.5X and 1.0X） were added according to the actual content （1.0X） in the soil of a second-generation poplar plantation. Each treatment had eight replicates. We measured gas exchange parameters and the activities of key enzymes related to nitrogen metabolism in the leaves. Leaf photosynthetic parameters varied with the concentration of phenolic acids. The net photosynthetic rate （PN） significantly decreased with increasing phenolic acid concentration, and non-stomatal factors might have been the primary limitation for PN- The activities of nitrate reductase （NR）, glutamine synthetase （GS） and glutamate synthase （GOGAT）, as well as the contents of nitrate nitrogen, ammonium nitrogen, and total nitrogen in the leaves decreased with increasing phenolic acid concentration. This was significantly and positively related to PN （P 〈 0.05）. The low concentration of phe- nolic acids mainly affected the transformation process of NO3- to NO2-, while the high concentration of phenolic acids affected both processes, where NO3- was transferred to NO2- and NH4＋ was transferred to glutamine （Gln）. Overall, phenolic acid had significant inhibitory effects on the photosynthetic productivity of Populus x euramericana ＇Neva＇. This was probably due to its influence on the activities of nitrogen assimilation enzymes, which reduced the amount of amino acids that were translated into protein and enzymes. Improving the absorption and utilization of nitrogen by plants could help to overcome the problems caused by continuous cropping.

Effects of Phenolic Acids on Growth and Activities of Membrane Protective Enzymes of Cucumber Seedlings

Two phenolic acids P-hydroxy benzoic acid and cinnamic acid were designated as four concentrations (0, 50 μmol/L, 100 μmol/L, 150 μmol/L) to investigate the effects of phenoic acids on the growth and the activities of membrane protective enzymes of cucumber seedlings. The results showed that both phenolic acids inhibited the seedlings growth. The inhibitory effects were increased with the concentration of phenolic acids increasing and the time of treatment prolonging. Seedlings treated with A150 (P-hydroxy benzoic acid, 150 μmol/L), B50 (cinnamic acid, 50 μmol/L), B100 (cinnamic acid, 100 μmol/L), B150 (cinnamic acid, 150 μmol/L) showed significantly shorter in plant height , smaller in leaf area. and lighter in fresh weight. The inhibitory effect of cinnamic acid was comparatively stronger than that of P-hydroxy benzoic acid. For protective enzymes system, compared to control , the POD activity increased at all concentrations of P-hydroxy benzoic acid during the treatment but increased at first then decreased before increased again at last at all concentrations of cinnamic acid .In the case of CAT, its activity increased at first, then decreased, and increased again at lower concentrations of phenolic acids. However, at higher concentrations the activities decreased at first, then increased a little, decreased continuously at last. In addition, the treatments of phenolic acids led to an increase then a decreaseof SOD activity and an increase of MDA content in the seedlings. All above indicated the accumulating of free radicalsand destruction of protective enzymes at higher concentrations of phenolic acids.

Research Progress on Application Effect of Biomass Charcoal and Its Restoration of Soil Phenolic Acid Pollution

Biomass charcoal has positive effects on reducing soil nutrient loss, increasing fertilizer utilization, reducing organic pollution and pesti-cide residues, inhibiting pollutant enrichment, and reducing bioavailability of pollutants. In this paper, the concept and effect of biomass charcoal were reviewed; the research situation of phenolic pollutants in soil was described; and the research progress on restoration of soil phenolic acid pol-lution by biomass charcoal application was summarized.

PRZEWALSKINIC ACID A,A NEW PHENOLIC ACID FROM SALVIA PRZEWALSKII MAXIM

From the root of Salvia przewalskii Maxim.a new phenolic acid, przewalskinic acid A was isolated and the structure was established by the analysis of^(13)C-NMR,~1H-NMR and two-dimensional COSY experiments.

Anti-acetylcholinesterase activity of the aglycones of phenolic glycosides isolated from Leonurus japonicus

Objective: To find the genuine structure with anti-acetylcholinesterase(anti-ACh E) from the phenolic glycosides abundant in Leonurus japonicus(Lamiaceae). The assay for antiACh E activity is often used to lead anti-Alzheimer's drugs.Methods: The five phenolic glycosides, tiliroside, leonurusoside C, 2’’’-syringoylrutin,rutin, and lavanduliofolioside were isolated from L. japonicus. The activities of the glycosides were relatively low. Seven compounds including p-coumaric acid, caffeic acid, hydroxytyrosol, salidroside, syringic acid, kaempferol, and quercetin, which are produced by the hydrolysis of the five glycosides, were also assayed for anti-ACh E activity.Results: Of those seven compounds, the five compounds other than salidroside and syringic acid exhibited potent anti-ACh E activities. In particular, the IC_(50)s of caffeic acid and quercetin were(1.05 ± 0.19) and(3.58 ± 0.02) mg/m L, respectively. Rutin was the most abundant flavonoid in the extract(9.18 mg/g as measured by HPLC).Conclusion: The substances with potent anti-ACh E were caffeic acid, quercetin, pcoumaric acid, kaempferol, and hydroxytyrosol that can be produced from their glycosides.

Study on Optimization of Ethanol Reflux Extraction of Phenolic Acids from Salvia miltiorrhiza

The extraction technology of phenolic acid compounds from Salvia miltiorrhiza by ethanol reflux was studied. In this experiment, salvianolic acid B standard was used to make the standard curve. Single factor experiment and orthogonal experiment were used to study the extraction of different ethanol concentrations, reflux times and material-to-liquid ratios. The OD value of salvianolic acid compounds was measured with a spectrophotometer. The extraction rate of phenolic acid compounds under different extraction conditions was calculated through a regression equation, so as to obtain the optimal conditions for the ethanol reflux extraction process of Salvia miltiorrhiza. The experimental data can provide a reference for the ethanol reflux extraction process of salvianolic acids in the industry. According to the experiment, the extraction rate of phenolic acids in Salvia miltiorrhiza was the highest when the ethanol concentration was 60%, the reflux time was 1.5 hours, and the ratio of material-to-liquid was 1:10.

Application of HPLC and ESI-MS techniques in the analysis of phenolic acids and flavonoids from green leafy vegetables (GLVs)

Diets containing high proportions of fruits and vegetables reduce the risk of onset of chronic diseases. The role of herbal medicines in improving human health is gaining popularity over the years, which also increases the need for safety and efficiency of these products. Green leafy vegetables （GLVs） are the richest source of phenolic compounds with excellent antioxidant properties. Increased consumption of diets containing phenolic compounds may give positive and better results to human health and significantly improves the immune system. Highly selective, susceptible and versatile analytical techniques are necessary for extraction, identifica- tion, and quantification of phenolic compounds from plant extracts, which helps to utilize their important biological properties. Recent advances in the pre-treatment procedures, separation techniques and spectro- metry methods are used for qualitative and quantitative analysis of phenolic compounds. The online coupling of liquid chromatography with mass spectrometry （LC-MS） has become a useful tool in the metabolic profiling of plant samples. In this review, the separation and identification of phenolic acids and flavonoids from GLVs by LC-MS have been discussed along with the general extraction procedures and other sources of mass spectrometer used. The review is devoted to the understanding of the structural configuration, nature and accumulation pattern of phenolic acids and flavonoids in plants and to highlighting the recent developments in the chemical investigation of these compounds by chromatographic and spectroscopic techniques. It concludes with the advantages of the combination of these two methods and prospects.

Temperature and Acidified Solvent Effect on Total Anthocyanins and RP-HPLC Phenolic Acids Determination in Selected Spices

Total anthocyanins of spices (Syzygium aromaticum L., Coriadrum sativum L., Cuminum cyminum L., Zingiber officinale Rosc., Elettaria cardamomum, Curcuma longa, Rhus coriaria L., Cinnamomum zeylanicum Blume, Foeniculum vulgare Mill and Laurus nobilis L.) were determined using acidified (1% HCl) solvents (methanol, ethanol and acetone) at three temperatures (20℃, 40℃ and 60℃). Also phenolic acids were separated and identified by RP-HPLC. Results showed that sumac and cinnamon had the highest levels of anthocyanins, while for the acetone the cinnamon indicated the highest amount of anthocyanins when methanol and ethanol were used as extracting solvents at 20℃. At 40℃ using ethanol, sumac showed the highest level of anthocyanins whereas acetone solvent yielded the highest anthocyanin contents for cinnamon. At 60℃, cinnamon showed the highest level of anthocyanins when methanol and acetone were the solvents, while sumac had the highest anthocyanins level using ethanol as solvent. HPLC results showed ten phenolic acids found in those spices and varied in their concentrations. Gallic acid had the highest level (1642.3 mg/100g) (cloves). Gentisic acid had the lowest level (1.2 mg/100g) in ginger. Also sumac showed the highest level of chlorogenic acid (1528.7 mg/100g). Some acids were not found in some spices, for instance, benzoic acid was not found in coriander, cumin, ginger, green cardamom, cinnamon and sweet laurel.

Analysis of the Fatty Acids and Phenolic Compounds in a Cereal-Based Fermented Food (Tarhana)

Tarhana is a Turkish home-made fermented food product. The mixture of wheat flour, yoghurt, yeast, cooked vegetables, salt, and spices is fermented for 1 - 7 days. Tarhana is sun dried and ground for preparation of instant Tarhana powder. Color, phenolic compounds and fatty acid composition were determined for home-made Tarhana, collected from 4 cities in the Thrace Region of Turkey. Color and phenolic content were significantly different (P < 0.05). These differences were due to the variation of ingredients used at different locations. The major unsaturated fatty acids were oleic (C18:1, 16.41% - 57.69%), and linoleic acids (C18:2, 9.74% - 56.31%). Palmitic (C16:0, 16.90% - 37.66%) and stearic acids (C18:0, 0.65% - 11.34%) were the main saturated fatty acids. This study suggested that Tarhana soup is a good source of unsaturated fatty acids. Antioxidant properties of phenolic compounds and their effect on peroxidation of lipids in Tarhana should be tested in future studies.