Jin Cai

Protective effect of Polygonum orientale L. extracts against Clavibater michiganense subsp. sepedonicum, the causal agent of bacterial ring rot of potato.

The Polygonum orientale L. extracts were investigated for antibacterial activity against Clavibater michiganense subsp. sepedonicum (Spieckermann & Kotthoff) Davis et al., the causal agent of a serious disease called bacterial ring rot of potato. The results showed that the leaf extracts of P. orientale had significantly (p<0.05) greater antibacterial activity against C. michiganense subsp. sepedonicum than root, stem, flower extracts in vitro. According to the results of single factor experiments and L273(13) orthogonal experiments, optimum extraction conditions were A1B3C1, extraction time 6 h, temperature 80°C, solid to liquid ratio 1∶10 (g:mL). The highest (p<0.05) antibacterial activity was observed when pH was 5, excluding the effect of control. The extracts were stable under ultraviolet (UV). In vivo analysis revealed that 50 mg/mL of P. orientale leaf extracts was effective in controlling decay. Under field conditions, 50 mg/mL of P. orientale leaf extracts also improved growth parameters (whole plant length, shoot length, root length, plant fresh weight, shoot fresh weight, root fresh weight, dry weight, and number of leaves), in the 2010 and 2011 two growing seasons. Further solvent partition assays showed that the most active compounds were in the petroleum ether fractionation. Transmission electron microscopy (TEM) showed drastic ultrastructural changes caused by petroleum ether fractionation, including bacterial deformation, electron-dense particles, formation of vacuoles and lack of cytoplasmic materials. These results indicated that P. orientale extracts have strong antibacterial activity against C. michiganense subsp. sepedonicum and a promising effect in control of bacterial ring rot of potato disease.

Laminaria japonica Extract, an Inhibitor of Clavibater michiganense Subsp. Sepedonicum

Bacterial ring rot of potato is one of the most serious potato plant and tuber diseases. Laminaria japonica extract was investigated for its antimicrobial activity against Clavibater michiganense subsp. sepedonicum (Spieckermann & Kotthoff) Davis et al., the causative agent of bacterial ring rot of potato. The results showed that the optimum extraction conditions of antimicrobial substances from L. japonica were an extraction temperature of 80°C, an extraction time of 12 h, and a solid to liquid ratio of 1∶25. Active compounds of L. japonica were isolated by solvent partition, thin layer chromatography (TLC) and column chromatography. All nineteen fractionations had antimicrobial activities against C. michiganense subsp. sepedonicum, while Fractionation three (Fr.3) had the highest (P<0.05) antimicrobial activity. Chemical composition analysis identified a total of 26 components in Fr.3. The main constituents of Fr.3 were alkanes (80.97%), esters (5.24%), acids (4.87%) and alcohols (2.21%). Antimicrobial activity of Fr.3 against C. michiganense subsp. sepedonicum could be attributed to its ability to damage the cell wall and cell membrane, induce the production of reactive oxygen species (ROS), increase cytosolic Ca2+ concentration, inhibit the glycolytic pathway (EMP) and tricarboxylic acid (TCA) cycle, inhibit protein and nucleic acid synthesis, and disrupt the normal cycle of DNA replication. These findings indicate that L. japonica extracts have potential for inhibiting C. michiganense subsp. sepedonicum.

Phytoremediation of phenol using Polygonum orientale and its antioxidative response

Abstract Polygonum orientale with beautiful red flowers can be found as one dominant species in the vicinity of most water bodies and wetlands in China. However, its phytoremediation potential has not been sufficiently explored because little is known about its resistance to inorganic or organic pollutants. We investigated P. orientale response to low and moderate levels of phenol stress (≤ 80 mg L-1). Endpoints included phenol tolerance of P. orientale and the removal of the pollutant, antioxidant enzyme activities, damage to the cell membrane, osmotic regulators and photosynthetic pigments. In plant leaves, phenol stress significantly increased the activities of peroxidase (POD) and catalase (CAT), as well as the contents of proline, soluble sugars and carotenoids, whereas superoxide dismutase (SOD), H2O2 and electrolyte leakage (EL) levels remained unaltered. On the other hand, there were significant decreases of soluble protein and chlorophyll contents. We demonstrated that, in combination with phenol tolerance and its removal, P. orientale has efficient protection mechanisms against phenol-induced oxidative damage (≤ 80 mg L-1). We propose that P. orientale could be used as an alternative and interesting material in the phytoremediation of phenol.

Antimicrobial activities of Nitellopsis obtusa (Desvaux) Groves and Chara vulgaris L.

The extracts of Nitellopsis obtusa (Desvaux) Groves and Chara vulgaris L. were investigated for antimicrobial activities against the following common microorganisms using an agar diffusion method: Staphylococcus aureus , Bacillus subtilis , Escherichia coli , Proteus vulgaris , Saccharomyces cerevisiae , and Candida albicans . The extracts strongly inhibited the growth of Gram-positive bacteria, but did not show inhibitory activity against Gram-negative bacteria and yeast. In this study, novel methods for extraction of antimicrobial substances from N . obtusa and C . vulgaris were reported. The optimum extraction conditions were investigated using single factor experimental design and L 27 3 (13) orthogonal experimental design. Results showed that the optimum extraction conditions for N . obtusa are: solid to liquid ratio 1:15, temperature 85°C, ethanol concentration 50%, extraction time 6h; and the optimum extraction conditions for C . vulgaris are: solid to liquid ratio 1:15, temperature 85°C, ethanol concentration 70%, extraction time 10h. Stability study demonstrated neuter and alkaline conditions enhanced the antimicrobial activities from N . obtusa and C . vulgaris , and both extracts were stable under ultraviolet (UV). These data suggest that extracts from both N . obtusa and C . vulgaris might be of potential use as bactericidal agents.

Protective effect of Dryopteris crassirhizoma extracts in the control of the root-knot nematode Meloidogyne incognita

Root-knot nematodes (Meloidogyne spp.) are among the most damaging soilborne plant parasites and are responsible for large economic losses in a wide variety of crops worldwide. More recently attention has increased on the use of phytochemicals as natural and biodegradable control agents to control plant-parasitic nematodes. In this study the nemat-icidal activity of extracts from 13 cryptogamic species was tested against the root-knot nematode Meloidogyne incognita. Ten extracts caused more then 50% mortality of second-stage juveniles after 48 h in an in vitro assay at 1 mg·ml-1. The extract from Dryopteris crassirhizoma displayed the highest activity, resulting in 100% mortality after 72 h at 1 mg·ml-1. The extract of D. crassirhizoma was then separated into five fractions by sequential extractions with water, petroleum ether, chloroform, ethyl acetate, and n-butyl alcohol. The chloroform fraction contained the highest level of total phloroglucinols (64.4%) and also was the most bioactive, with the lowest LC50 value of 0.4 mg·ml-1. In pot experiments, D. crassirhizoma was tested against M. incognita on tomato and applied in three ways: as a liquid extract for soil drenching and root-dip treatments, or as a powder applied as a soil additive. All of these treatments reduced root galling and the final population density of M. incognita and increased plant growth compared with the control. Of the three types of treatments, soil amendment with pulverized rhizomes from D. crassirhizoma was the most effective treatment against M. incognita.

Effects of Chloroform Extract of Dryopteris crassirhizoma on the Ultramicroscopic Structures of Meloidogyne incognita

In our early experiments, the chloroform extract of D. crassirhizoma was demonstrated to contain the highest concentrations of total phloroglucinols among several extract fractions and possessed the most effective nematicidal activity. This study aimed to ascertain the ultrastructural changes in M. incognita after treatment with a D. crassirhizoma chloroform extract at 1 mg·mL−1 for 24 h. It was found that the extract exhibited significant destructive effects on the worms ultrastructure and caused distinctive damage to body surfaces and internal structures. These results will contribute to a deeper understanding of the nematicidal mechanism of D. crassirhizoma, as well as in the design of efficient bionematicides.

Antimicrobial activity of Laminaria japonica extracts against bacterial canker of tomato disease agent Clavibacter michiganensis subsp. michiganensis

Laminaria japonica was extracted with ethanol, and tested for antimicrobial activity against Clavibacter michiganensis subsp. michiganensis (Cmm). This gram-positive bacterium is the agent of a serious tomato disease called bacterial canker. On in vitro antimicrobial assays, L. japonica extracts showed intensive antimicrobial activity to inhibit Cmm. Extracting parameters (time, temperature, and solid/liquid ratio) were investigated and further optimized integratedly with L27(313) orthogonal array design (OAD). Our data implied that the optimum extraction conditions were A3B3C3, that were extracting time 12 h, extracting temperature 80 °C, and solid/liquid ratio 1:30 (g:mL). Extracting temperature was the significant factor affecting extracting condition. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of L. japonica extracts against Cmm were 2.5 mg/mL and 5 mg/mL. Scanning electron microscopy (SEM) observation indicated L. japonica extracts caused considerable morphological alterations in Cmm cells, such as protoplast leakage, cell membrane disruption, cell clumped, and cell fragmented. Reactive oxygen species (ROS) level determination and ATPase activity assay revealed that L. japonica extracts did cause significant accumulation in ROS and reduce the intracellular ATPase activity rapidly. Accordingly, these results indicated that L. japonica extracts could open a new promising opportunity for this tomato disease control.

Inhibitory activity of Athyrium sinense extracts against Clavibater michiganense subsp. sepedonicum

Clavibater michiganense subsp. sepedonicum , the causal agent of a serious disease called bacterial ring rot of potato, is widespread under both greenhouse and field cultivation. In order to find a promising method for the control of this disease, Athyrium sinense extracts were investigated in the study presented here. Results showed that the A. sinense extracts had significantly inhibitory activity against C. michiganense subsp. sepedonicum . Eight organic solvents were used to obtain A. sinense extracts, and ethanol was selected as an ideal extraction solvent. Based on single factor experiment results and L 27 3 (13) orthogonal experiment results, optimum extraction conditions were obtained. They were A 2 B 3 C 3 , solid to liquid ratio 1:20 (g:mL), temperature 97°C and extraction time 10h. Stability assays revealed that Zn 2+ , Fe 3+ , acidic and neutral conditions enhanced inhibitory activity, and extracts were stable under ultraviolet (UV). Transmission electron microscopy (TEM) showed drastic changes caused by A. sinense extracts, including lack of cytoplasmic materials, formation of vacuoles and bacterial deformation. These results revealed A. sinense extracts have strong inhibitory activity against C. michiganense subsp. sepedonicum , and can be used as a potent phytochemical fungicide.