Chemical composition and in vitro control of agricultural plant pathogens by the essential oil and various extracts of Nandina domestica Thunb.

BACKGROUND: The aims of this study were to examine the chemical composition of the essential oil isolated from the floral parts of Nandina domestica Thunb. by hydrodistillation, and to test the efficacy of essential oil and various leaf extracts (n‐hexane, chloroform, ethyl acetate and methanol) as an antifungal potential against a panel of agricultural plant pathogens. RESULTS: The GC‐MS analysis determined that 79 compounds, which represented 87.06% of total oil, were present in the oil containing mainly 1‐indolizino carbazole (19.65%), 2‐pentanone (16.4%), mono phenol (12.1%), aziridine (9.01%), methylcarbinol (4.6%), ethanone (3.3%), furfural (2.96%), 3,5‐dimethylpyrazole (1.29%) and 2(5H)‐furanone (1.32%). The oil (1000 ppm disc^?1) and the leaf extracts (1500 ppm disc^?1) revealed remarkable antifungal effect against Fusarium oxysporum, Fusarium solani, Phytophthora capsici, Colletotrichum capsici, Sclerotinia sclerotiorum, Botrytis cinerea and Rhizoctonia solani in the growth inhibition range of 53.3–64.3% and 33.3–56.0%, respectively, along with their respective values for mimimum inhibitory concentration (MIC) ranging from 125 to 1000 µg mL^?1 and 500 to 2000 µg mL^?1. The values for minimal fungicidal concentration (MFC) of the oil and extracts were obtained in the range of 125 to 1000 µg mL^?1 and 500 to 2000 µg mL^?1, respectively. The essential oil also had a strong detrimental effect on spore germination of all the plant pathogens tested along with concentration as well as time‐dependent kinetic inhibition of B. cinerea. CONCLUSION: The results obtained in this study demonstrate that N. domestica mediated oil and extracts could become potential alternatives to synthetic fungicides for controlling certain important agricultural plant pathogenic fungi. Copyright © 2008 Society of Chemical Industry     

Enhancing disease resistance in peach fruit with methyl jasmonate

BACKGROUND: Peaches are susceptible to microbial decay during postharvest distribution at ambient temperature. To search for effective alternatives to currently used fungicides for disease control, in this study the effect of methyl jasmonate (MeJA) on disease resistance and fruit decay of peaches after harvest in response to pathogen attack was investigated. RESULTS: Freshly harvested peaches were treated with 1 µmol L^?1 MeJA vapour at 20 °C for 24 h. At 0, 12, 24 and 36 h after this treatment, both treated and untreated fruits were artificially wounded and inoculated with Penicillium expansum, Botrytis cinerea or Rhizopus stolonifer spore suspension (1 × 10⁵ spores mL^?1) and then incubated at 20 °C for 6 days. MeJA treatment significantly reduced the postharvest diseases. Incubation for 12 h was the optimal length of time after MeJA treatment, resulting in the lowest disease incidence and lesion diameter for all pathogens. The activities of defence enzymes including chitinase, β‐1,3‐glucanase, phenylalanine ammonia‐lyase, polyphenol oxidase and peroxidase were enhanced by MeJA treatment, and the level of total phenolics in MeJA‐treated fruit was also higher than that in control fruit. In addition, MeJA affected hydrogen peroxide (H₂O₂)‐metabolising enzymes such as superoxide dismutase, catalase and ascorbate peroxidase and induced a higher level of H₂O₂ during incubation, which might serve as a signal to induce resistance against P. expansum. CONCLUSION: MeJA was effective in reducing decay and might enhance disease resistance in peach fruit by increasing levels of antipathogenic proteins and antimicrobial phenolic compounds. Copyright © 2009 Society of Chemical Industry     

Isolation of eriocitrin (eriodictyol 7‐O‐rutinoside) as an arachidonate lipoxygenase inhibitor from Lumie fruit (Citrus lumia) and its distribution in Citrus species

An inhibitory compound acting against rat platelet 12‐lipoxygenase was isolated from the peel of Lumie fruit (Citrus lumia) by activity‐guided separation. It was identified as eriocitrin (eriodictyol 7‐O‐rutinoside) by spectroscopic analyses. Eriocitrin inhibited 5‐lipoxygenase (IC₅₀29.1 µmol L^?1) from rat peritoneal polymorphonuclear leukocytes in addition to 12‐lipoxygenase (IC₅₀22.3 µmol L^?1). Its aglycone, eriodictyol (5,7,3′, 4′‐tetrahydroxyflavanone), was a much more potent inhibitor of both 12‐lipoxygenase (IC₅₀0.07 µmol L^?1) and 5‐lipoxygenase (IC₅₀0.20 µmol L^?1). It also inhibited the production of leukotriene B₄ in intact peritoneal polymorphonuclear leukocytes stimulated with calcium ionophore A23187 (IC₅₀12.7 µmol L^?1). The distribution of eriocitrin in 39 citrus fruits was investigated by high‐performance liquid chromatography analysis. Lumie, eureka lemon (Citrus limon), Sambokan (Citrus sulcata), Sudachi (Citrus sudachi) and Koji (Citrus leiocarpa) fruits were found to contain high levels of eriocitrin in both peel and juice vesicles. Copyright © 2006 Society of Chemical Industry     

A novel antifungal peptide from foxtail millet seeds

BACKGROUND: Antifungal proteins (AFP) help plants to combat phytopathogenic fungi and thus protect plants from the devastating damage caused by fungal infections and prevent massive economic losses. To date, several proteins with antibacterial and/or antifungal properties have been isolated and characterized from different plant species and tissues; however, there are no reports concerning the antifungal peptide from foxtail millet seeds. RESULTS: An antifungal peptide with a molecular mass of 26.9 kDa was isolated from dry seeds of the foxtail millet (Setaria italica (L.) Beauv.), using a procedure that involved four chromatographic steps. The antifungal peptide was adsorbed on CM‐Sepharose, Affi‐gel blue gel and Superdex 75. It was further purified by C₁₈ reverse‐phase high‐performance liquid chromatography and submitted for analysis of peptide mass fingerprint. The Mascot peptide mass fingerprint of the isolated protein hit no existing protein (score > 60), and it was proved to be a novel antifungal peptide. It inhibited mycelial growth in Alternaria alternate with an IC₅₀ of 1.3 µmol L^?1, and it also exhibited antifungal activity against Trichoderma viride, Botrytis cinerea and Fusarium oxysporum. Transmission electron microscopy of mold forms of Alternaria alternate after incubation with 20 µg mL^?1 of the antifungal protein for 48 h revealed marked ultrastructural changes in the fungus. CONCLUSION: A novel antifungal peptide with high potency was isolated from foxtail millet seeds. Copyright © 2011 Society of Chemical Industry     

Scirpusin A,a hydroxystilbene dimer from Xinjiang wine grape,acts as an effective singlet oxygen quencher and DNA damage protector

BACKGROUND: Grapes and red wines are rich sources of phenolic compounds such as anthocyanins, catechins, flavonols and stilbenes, most of which are potent antioxidants showing cardioprotective properties. We first isolated scirpusin A, a hydroxystilbene dimer, from a wine grape of Xinjiang, and studied its antioxidant activity. RESULTS: Reactive oxygen species scavenging effects and the protection against reactive singlet oxygen‐induced DNA damage of scirpusin A have been investigated in our experiments. The concentration of scirpusin A required to inhibit 50% of ¹O₂ generation was 17 µmol L^?1, while addition of scirpusin A at 140 µmol L^?1 caused complete inhibition. Further kinetic study revealed that the reaction of Scirpusin A with singlet oxygen has an extremely high rate constant (k_a = 4.68 × 10⁹ L mol^?1 s^?1). Scirpusin A (140 µmol L^?1) exhibited significant inhibition effects on pBR322 DNA breakage. However, scavenging effects of scirpusin A on superoxide anion O₂^?? and hydroxyl radical ·OH were not potent as the inhibitor rates at a concentration of 1400 µmol L^?1 were 28.83% and 19.5%, respectively. CONCLUSION: The present study shows that scirpusin A is a selective quencher of singlet oxygen and a protector against reactive singlet oxygen‐induced pBR322 DNA damage at very low concentrations. Copyright © 2010 Society of Chemical Industry     

Polyphenol oxidase activity of two olive (Olea europaea L.) cultivars as an early criterion of Mn toxicity

BACKGROUND: The time course of polyphenol oxidase (PPO) activity in the leaves of two olive cultivars (Picual and FS‐17) irrigated with nutrient solutions differing in Mn concentration (0, 2 and 1280 µmol L^?1) was studied under hydroponic conditions to determine whether PPO activity could be used as an early criterion of Mn status of olive plants, and to elucidate whether genotypic differences exist between the two olive cultivars studied, concerning the effect of Mn concentration on PPO activity. RESULTS: In all the Mn treatments, PPO activity was greater in Picual than in FS‐17. Under excess Mn (1280 µmol L^?1), PPO activity gradually increased with time, starting from day 30 of the experiment in both cultivars, and this increase preceded the appearance of Mn toxicity symptoms. In contrast, in the other two Mn treatments (0 and 2 µmol L^?1) PPO activity increased and afterwards decreased during the experiment, but the trend was not clear. In the 1280 µmol L^?1 treatment, PPO activity linearly increased (R = 0.8836 for Picual and 0.943 for FS‐17) with the increase of Mn concentration in the leaves of both cultivars. In the 1280 µmol L^?1 Mn treatment, PPO activity was negatively related with Fe and Zn concentrations in the leaves, and positively in the 0 and 2 µmol L^?1 Mn treatments with the Ca, Mg and K concentrations. CONCLUSION: From the differential time course of PPO activity in the three Mn treatments (0, 2 and 1280 µmol L^?1), it is concluded that periodic measurements of PPO activity in the leaves of the olive cultivars Picual and FS‐17 can be used for the early detection of Mn toxicity (before the appearance of symptoms). Copyright © 2010 Society of Chemical Industry     

Assessment of in vitro antioxidant, antibacterial and immune activation potentials of aqueous and ethanol extracts of Phyllanthus niruri

BACKGROUND: Recently much attention has been paid to biologically active plants because of their low production cost and fewer adverse effects compared with chemical drugs. In the present investigation the bioactivity of Phyllanthus niruri ethanol and aqueous extracts was evaluated in vitro. RESULTS: The ethanol extract of P. niruri showed a high level of flavonoid content (123.9 ± 0.002 mg g^?1), while the aqueous extract showed the highest 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH; IC₅₀6.85 ± 1.80 µmol L^?1) and 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS; 46.44 ± 0.53 µmol L^?1) free radical scavenging activities with high phenol content (376 ± 0.02 mg g^?1) and elevated levels of ferric reducing antioxidant power (FRAP; 23 883 ± 0.019 mmol g^?1) with excellent antibacterial activity against Staphylococcus aureus (20 mm inhibition zone) and Streptococcus agalactiae (12 mm inhibition zone), respectively, in addition to the best immune activation potential of human peripheral blood mononuclear cells (450.5%). CONCLUSIONS: It is clear from our results that both extracts of P. niruri has excellent bioactivity roles via elevated levels of antibacterial, antioxidant and percentage of peripheral blood mononuclear cell proliferation, which could lead to the development of medications for clinical use. Copyright © 2012 Society of Chemical Industry     

α-Glucosidase- and α-amylase-inhibitory activities of phlorotannins from Eisenia bicyclis

BACKGROUND: In an effort to develop alternative therapeutic agents, strong inhibitory activity against α‐glucosidase and α‐amylase was detected in Eisenia bicyclis methanolic extract. RESULTS: In this study, two phlorotannins were isolated from E. bicyclis and characterised by chromatography and nuclear magnetic resonance. The active substances were identified as fucofuroeckol A (FF) and dioxinodehydroeckol (DD). To the authors' knowledge, this is the first report of the identification of these substances in E. bicyclis. However, to date, no antidiabetic activity of FF and DD has been reported. Both phlorotannins demonstrated significant inhibitory activity against α‐glucosidase and α‐amylase. FF showed potent antidiabetic activity, with IC₅₀ values of 131.34 nmol L^?1 against α‐glucosidase and 42.91 µmol L^?1 against α‐amylase. The corresponding IC₅₀ values of DD were 93.33 nmol L^?1 and 472.7 µmol L^?1. Furthermore, kinetic analysis revealed that FF and DD exhibited non‐competitive inhibitory activity against α‐glucosidase. CONCLUSION: These results suggest that FF and DD may be candidates for the development of an antidiabetic pharmaceutical agent or food additive. Copyright © 2012 Society of Chemical Industry     

Sulfate determines the glucosinolate concentration of horseradish in vitro plants (Armoracia rusticana Gaertn., Mey. & Scherb.)

BACKGROUND: Horseradish plants (Armoracia rusticana) contain high concentrations of glucosinolates. Former studies have revealed that Armoracia plants cultivated in vitro have markedly lower glucosinolate concentrations than those grown in soils. Yet, these studies neglected that the sulfate concentration in the growth medium may have had a strong impact on glucosinolate metabolism. Accordingly, in this study horseradish in vitro plants were cultivated with differing sulfate concentrations and the glucosinolate concentrations were quantified by ion pair HPLC. RESULTS: Cultivation in 1.7 mmol L^?1 sulfate (as used in the prior studies) resulted in the accumulation of 16.2 µmol g^?1 DW glucosinolates, while the glucosinolate concentration increased to more than 23 µmol g^?1 DW when 23.5 mmol L^?1 sulfate was used in the medium. Correspondingly, the glucosinolate concentration decreased to 1.6 µmol g^?1 DW when sulfate concentration was lowered to 0.2 mmol L^?1. CONCLUSION: Since the glucosinolate accumulation in relation to the sulfate concentration follows a typical saturation curve, we deduce that the availability of sulfate determines the glucosinolate concentration in horseradish in vitro plants. © 2012 Society of Chemical Industry     

Control of anthracnose rot and quality deterioration in loquat fruit with methyl jasmonate

BACKGROUND: Loquat (Eriobotrya japonica Lindl.) fruit has a short shelf‐life, mainly due to fungal decay. Current control of postharvest disease of the fruit is mainly dependent on fungicides. However, because of the increasing consumer concern over food safety, there is an urgent need to search for effective alternatives to control disease. The objective of this work was to determine the efficacy of methyl jasmonate (MeJA) in controlling anthracnose rot caused by Colletotrichum acutatum and maintaining quality of loquat fruit. RESULTS: Loquat fruit were treated with 10 µmol L^?1 MeJA and wound inoculated with C. acutatum spore suspension of 1.0 × 10⁵ spores mL^?1 24 h after treatment, and then stored at 20 °C for 6 days. The percentage of infected wounds showing decay symptom was reduced from 54.4% to 16.7% and the lesion diameter was reduced from 7.26 mm to 4.00 mm by MeJA treatment on the 4th day after inoculation. MeJA treatment induced higher activities of two defense‐related enzymes—chitinase and β‐1,3‐glucanase—during 6 days storage. Meanwhile, the treatment inhibited increases in fruit firmness and internal browning index, and maintained higher extractable juice rate and total soluble solids and titratable acidity contents, thereby delaying the development of flesh leatheriness. CONCLUSION: MeJA treatment effectively inhibited anthracnose rot and maintained quality in loquat fruit. Inhibition of the disease was mainly because of resistance induced in loquat fruit by MeJA. A postharvest application of MeJA could be an alternative to chemical fungicides for control of postharvest disease in loquat fruit. Copyright © 2008 Society of Chemical Industry