Diatom cell-size composition as a novel tool for quantitative estimates of the water table in peatlands.

Diatom cell-size composition is an indicator of aquatic environmental changes but has been rarely investigated, especially in semi-terrestrial peatlands. In this study, both taxonomic composition and cell-size composition of diatoms were analysed in 41 samples from two montane peatlands, northeastern China. Redundancy analyses revealed that diatom taxonomic composition was significantly related to the depth to the water table (DWT) and Ca2+, while cell-size composition was significantly associated with DWT and Si. DWT was the most important factor and its sole effect explained 26.2% and 17.9% of the total variance in taxonomic composition and cell-size composition, respectively. Accordingly, diatom-based water-table transfer functions were developed based on taxonomic composition and cell-size composition, respectively. The maximum-likelihood (ML) model based on diatom taxonomic composition had the best performance, with a correlation coefficient value (R2) of 0.78 and the root mean squared error of prediction (RMSEP) of 6.66 cm. The ML model based on cell-size composition had similar performance, with an R2 of 0.78 and the RMSEP of 6.87 cm, suggesting that diatom cell-size composition can be a new quantitative means to track past water-table changes. This method requires further appraisal with palaeoecological data but offers a new option that deserves exploration.

Three rare anti-inflammatory sesquiterpene lactones from Magnolia grandiflora.

Four new sesquiterpene lactones (SLs) (1-4), along with a biosynthetically related SL (5), have been isolated from the leaves of Magnolia grandiflora. Magrandate A (1) is notable as the first C18 homogemarane type SL, featuring a unique 1,7-dioxaspiro[4.4]nonan-6-one core. Compounds 2 and 3, representing the first instances of chlorine-substituted gemarane-type SL analogs in natural products, were also identified. The structures of these isolates were elucidated through a combination of spectroscopic data analysis, electronic circular dichroism calculations, and X-ray single-crystal diffraction analysis. All isolates demonstrated anti-inflammatory activity in lipopolysaccharide-stimulated RAW264.7 cells. Notably, 3-5 showed a significant inhibitory effect on nitric oxide production, with IC50 values ranging from 0.79 to 4.73 µmol·L-1. Additionally, 4 and 5 exhibited moderate cytotoxic activities against three cancer cell lines, with IC50 values between 3.09 and 11.23 µmol·L-1.

Bioassay-guided isolation of α-Glucosidase inhibitory constituents from Hypericum sampsonii.

This study employed the α-glucosidase inhibitory activity model as an anti-diabetic assay and implemented a bioactivity-guided isolation strategy to identify novel natural compounds with potential therapeutic properties. Hypericum sampsoniiwas investigated, leading to the isolation of two highly modified seco-polycyclic polyprenylated acylphloroglucinols (PPAPs) (1 and 2), eight phenolic derivatives (3-10), and four terpene derivatives (11-14). The structures of compounds 1 and 2, featuring an unprecedented octahydro-2H-chromen-2-one ring system, were fully characterized using extensive spectroscopic data and quantum chemistry calculations. Six compounds (1, 5-7, 9, and 14) exhibited potential inhibitory effects against α-glucosidase, with IC50 values ranging from 0.050 ± 0.0016 to 366.70 ± 11.08 µg·mL-1. Notably, compound 5 (0.050 ± 0.0016 µg·mL-1) was identified as the most potential α-glucosidase inhibitor, with an inhibitory effect about 6900 times stronger than the positive control, acarbose (IC50 = 346.63 ± 15.65 µg·mL-1). A docking study was conducted to predict molecular interactions between two compounds (1 and 5) and α-glucosidase, and the hypothetical biosynthetic pathways of the two unprecedented seco-PPAPs were proposed.

Discovery of diverse sesquiterpenoids from Magnolia grandiflora with cytotoxic activities by inducing cell apoptosis.

Phytochemical study of Magnolia grandiflora led to the isolation of 39 sesquiterpenoids, including 15 new compounds (1-15). Compounds 1 and 2 are discovered to be the first 13-norgermacrane type sesquiterpenoids in natural products. Compound 15 is a rare 5,6-seco-guaiane type sesquiterpene and its possible biogenic precursor is presumed to be compound 20. Subsequent structural modification for compound 28 led to 21 derivatives, among which 15 derivatives were new compounds. All compounds were tested for the inhibitory effects on three tumor cell lines, and 17 compounds were active with the IC50 values ranging from 1.91 ± 0.39 µM to 12.29 ± 1.68 µM. The structure-activity relationships implied that an α, ß-unsaturated lactone group was an important active group for the cytotoxicity. Two most active compounds (19 and 29) with low toxicity on normal human liver cell line were selected for further mechanism study. Compound 29 could induce apoptosis on Colo320DM cells through influencing the key apoptotic related proteins, such as PARP, Cleaved PARP, cleaved Caspase-3, and pro-Caspase 3. In addition, compound 19 with the best cytotoxic activity on HEL cells also could induce the apoptosis in dose- and time-dependent manners. In summary, our investigation implied that compounds 19 and 29 are two new potential anti-cancer candidates for ongoing study in the future.

Secondary metabolites from the Endophytic fungi Fusarium decemcellulare F25 and their antifungal activities.

Seven new compounds, including three isocoumarins (1-3), three pyrrolidinone derivatives (8-10), and one pentaene diacid (15), together with 13 known compounds, were isolated from the rice culture of the endophytic fungus Fusarium decemcellulare F25. Their structures and stereochemistry were established using HRESIMS, NMR, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction. The possible biosynthetic pathways for compounds 1-3 and 8-10 were proposed. The antifungal efficacies of compounds 1 - 20 were evaluated against Colletotrichum musae, and compounds 13, 14, and 17 exhibited inhibitory activities against C. musae with MIC values of 256, 64 and 128 µg/mL, respectively.

Wheat Root Protection From Cereal Cyst Nematode (Heterodera avenae) by Fluopyram Seed Treatment.

Cereal cyst nematode (Heterodera avenae), an important plant-parasitic nematode causing yield losses of wheat, has been found in many provinces in China. It is urgent to develop an effective method of protecting wheat from H. avenae damage. Because of its novel mode of action, fluopyram has been registered for controlling root-knot nematodes on cucumber and tomato in China. However, the bioactivity of fluopyram against H. avenae and whether this seed treatment can effectively control H. avenae on wheat remains unknown. In this study, a bioactivity assay revealed that fluopyram increased the mortality of H. avenae second-stage juveniles (J2), with lethal concentrations (LC) required to kill 50% (LC50) and 90% (LC90) of 0.92 mg⋅liter-1 and 2.92 mg⋅liter-1, respectively. Hatching tests showed that the H. avenae egg hatching percent was reduced by 35.2 to 69.2% with fluopyram at rates of 1.6 to 6.4 mg⋅liter-1, and that the egg hatching period was delayed by 3 to 9 days compared with the control. During pot and field trials, fluopyram seed treatment significantly reduced the H. avenae population density and increased wheat yield by 3.0 to 13.7%. Therefore, fluopyram seed treatment is an effective approach for the management of H. avenae on wheat in China.

Screening, identification and application of soil bacteria with nematicidal activity against root-knot nematode (Meloidogyne incognita) on tomato.

BACKGROUND: Root-knot nematodes (Meloidogyne spp.) are soilborne pathogens that can cause great damage to and economic loss of crops globally. Owing to the high toxicity of chemicals toward humans and the environment, the use of biocontrol bacteria, a promising method for controlling root-knot nematodes, has gained attention. RESULTS: To screen novel bacterial strains for their ability to control root-knot nematodes, 106 bacterial strains were isolated from soil. Eight of the obtained isolates exhibited satisfactory nematicidal activity against Meloidogyne incognita at 2-fold dilutions (approximately 3 × 1012 CFU mL-1 ) after 12 h of exposure. Based on their physiological, biochemical and molecular (16S rRNA and gyrB gene sequences) characteristics, the eight strains were identified as Bacillus halotolerans, B. kochii, B. oceanisediminis, B. pumilus, B. toyonensis, B. cereus, Pseudomonas aeruginosa and B. pseudomycoides. In greenhouse and field experiments, the eight isolates suppressed M. incognita up to 69.96% compared to the control. Additionally, the yield of tomato increased 1.4-26.1% over that of the control. CONCLUSION: The strains of B. halotolerans DDWA, B. kochii DDWB, B. oceanisediminis DDWC and B. pseudomycoides JNC have potential to control M. incognita, which has not been previously reported. © 2020 Society of Chemical Industry.

Modifying the Formulation of Abamectin To Promote Its Efficacy on Southern Root-Knot Nematode (Meloidogyne incognita) under Blending-of-Soil and Root-Irrigation Conditions.

The southern root-knot nematode (RKN), Meloidogyne incognita, is the most disastrous and prevalent nematode threat to the production of crops, especially vegetables. In the current study, second-stage juveniles (J2) of M. incognita were collected from five regions near Tai'an, China. The toxicity of abamectin to these J2 had insignificant differences, with LC50 values of approximately 2 mg/L. Two pesticide application approaches (i.e., blending-of-soil and root-irrigation) were adopted in pot experiments; blending-of-soil was more beneficial for promoting the efficacy of abamectin on the RKN of tomatoes. Abamectin microcapsule suspension exhibited superiority to emulsifiable concentrate (EC) at dosages of 5 and 10 mg active ingredient per plant integrating efficacy, root length, plant height, the fresh weight of roots, and the fresh weight of stems + leaves. Adsorption, leaching, and mobility of abamectin in the soil also verified bioactivity test results. Modifying the formulation of abamectin can promote its efficacy on RKN under different application approaches.

Effects of the plant volatile trans­2-hexenal on the dispersal ability, nutrient metabolism and enzymatic activities of Bursaphelenchus xylophilus.

Bursaphelenchus xylophilus causes pine wilt disease (PWD), which severely damages pine species. The plant volatile trans­2-hexenal has strong activity against nematodes, although the precise mechanism of this inhibitory action remains unclear. In this paper, the fumigant effects of the LC10 and LC30 of trans­2-hexenal on B. xylophilus were demonstrated. The trans­2-hexenal treatments significantly inhibited the dispersal ability of nematodes. The results also indicated that trans­2-hexenal affects the metabolism of nutrients and the activity of digestive enzymes. Among detoxifying enzymes, after treatment with trans­2-hexenal, glutathione S-transferase activity increased significantly and general esterase activity decreased significantly. Based on these results, trans­2-hexenal disturbs the normal physiological and biochemical activities of this nematode. These results provide valuable insight into the nematicidal mechanisms of trans­2-hexenal.

Nematicidal Activity of trans-2-Hexenal against Southern Root-Knot Nematode (Meloidogyne incognita) on Tomato Plants.

Botanical nematicides have recently received increasing interest because of the high risks of some traditional nematicides to human health and the environment. This study evaluated the nematicidal activity of a plant volatile, trans-2-hexenal, against Meloidogyne incognita. This compound exhibited higher activity in a fumigation experiment than in the aqueous phase in vitro. Both in pot tests and in field trials, trans-2-hexenal showed significant efficacy against M. incognita while maintaining excellent plant growth, especially at doses of 1000 and 500 L ha-1, which were superior to that of abamectin at 180 g ha-1 via hole application treatment but not significantly different from fumigation with 400 kg ha-1 of dazomet. Furthermore, plants treated with 500 L ha-1 trans-2-hexenal had fruit yields 20.2 and 45% greater than the control group. On this basis, trans-2-hexenal may be a potential alternative fumigation agent for controlling M. incognita on tomato crops.

Effects of trans-2-hexenal on reproduction, growth and behaviour and efficacy against the pinewood nematode, Bursaphelenchus xylophilus.

BACKGROUND: Bursaphelenchus xylophilus is a serious quarantined pest that causes severe damage and major economic losses to pine forests. Because of the adverse effects of some traditional nematicides on humans and the environment, the search for new plant toxicants against these nematodes has intensified. Nematicidal activity of trans-2-hexenal, which is a six-carbon aldehyde present in many plants, was tested against the nematode. RESULTS: trans-2-Hexenal showed significant efficacy against B. xylophilus in a dose range of 349.5-699 g m-3 by fumigation of pinewood logs. Additionally, it had significant nematicidal activity against different life stages of B. xylophilus in an in vitro test, with second-stage larvae (L2s) being the most sensitive, with an LC50 value of 9.87 µg mL-1 at 48 h. Egg hatch was also significantly inhibited. Further studies revealed that trans-2-hexenal inhibited the reproductive activity of B. xylophilus, with negative effects on reproduction rate and egg numbers. Moreover, trans-2-hexenal reduced the body length of B. xylophilus. Respiratory rate and thrashing behaviour of B. xylophilus also decreased following treatment with this compound. CONCLUSION: trans-2-Hexenal had significant nematicidal activity against B. xylophilus, providing a basis for elucidation of the mode of action of trans-2-hexenal against plant-parasitic nematodes in future studies. © 2016 Society of Chemical Industry.

Effects of the microbial secondary metabolite benzothiazole on the nutritional physiology and enzyme activities of Bradysia odoriphaga (Diptera: Sciaridae).

Bradysia odoriphaga (Diptera: Sciaridae) is the major pest that damages Chinese chive production. As a volatile compound derived from microbial secondary metabolites, benzothiazole has been determined to possess fumigant activity against B. odoriphaga. However, the mechanism of action of benzothiazole is not well understood. In the present study, fourth-instar larvae of B. odoriphaga were exposed to LC10 and LC30 of benzothiazole. Sublethal concentrations (LC10 and LC30) of benzothiazole significantly reduced the food consumption of the larvae on the second day after treatment (2 DAT). However, there were no significant changes in pupal weight among the different treatments. We also measured the protein, lipid, carbohydrate, and trehalose contents and the digestive enzyme activities of the larvae, and the results suggest that benzothiazole reduced the nutrient accumulation and decreased the digestive enzyme activities of B. odoriphaga. In addition, the activity of glutathione S-transferase was significantly decreased at 6h after treatment with benzothiazole, whereas general esterase activities were significantly increased at 6 and 24h after treatment. The results of this study indicate that benzothiazole interferes in the normal food consumption and digestion process by decreasing the activities of digestive enzymes. These results provide valuable information for understanding the toxicity of benzothiazole and for exploring volatile compound for the control of this pest.