The Effect of 5OH-1,4-Naphthoquinone on Norway Spruce Seeds during Germination

Biochar mitigates allelopathic effects in temperate trees

Many invasive and some native tree species in North America exhibit strong allelopathic effects that may contribute to their local dominance. Pyrogenic carbon (PyC; including soot, charcoal, and black carbon) is produced by the incomplete combustion of organic matter and is widespread in forest soils. Many forms of PyC have sorptive properties that can reduce the bioavailability of allelochemicals. We investigated the potential for PyC produced by controlled pyrolysis of biomass ("biochar" [BC]) to reduce the allelopathic effects of black walnut (Juglans nigra) and Norway maple (Acer platanoides), a common native tree species and a widespread invasive species in North America, respectively. Seedling growth of two native tree species (Acer saccharinum [silver maple] and Betula papyrifera [paper birch]) in response to leaf-litter-incubated soils was examined; litter incubation treatments included leaves of black walnut, Norway maple, and a nonallelopathic species (Tilia americana [American basswood]) in a factorial design with varying dosages; responses to the known primary allelochemical of black walnut (juglone) were also examined. Juglone and leaf litter of both allelopathic species strongly suppressed seedling growth. BC treatments substantially mitigated these effects, consistent with the sorption of allelochemicals; in contrast no positive effects of BC were observed in leaf litter treatments involving controls or additions of nonallelopathic leaf litter. Treatments of leaf litter and juglone with BC increased the total biomass of silver maple by ~35% and in some cases more than doubled the biomass of paper birch. We conclude that BCs have the capacity to largely counteract allelopathic effects in temperate forest systems, suggesting the effects of natural PyC in determining forest community structure, and also the applied use of BC as a soil amendment to mitigate allelopathic effects of invasive tree species.

Inhibitory effect of novel 5-O-acyl juglones on mammalian DNA polymerase activity, cancer cell growth and inflammatory response

We previously found that vitamin K(3) (menadione, 2-methyl-1,4-naphthoquinone) inhibits the activity of human mitochondrial DNA polymerase γ (pol γ). In this study, we focused on juglone (5-hydroxy-1,4-naphthoquinone), which is a 1,4-naphthoquinone derivative, and chemically synthesized novel juglones conjugated with C2:0 to C22:6 fatty acid (5-O-acyl juglones). The chemically modified juglones enhanced mammalian pol inhibition and their cytotoxic and anti-inflammatory activities. The juglone conjugated with oleic acid (C18:1-acyl juglone) showed the strongest inhibition of DNA replicative pol α activity and human colon carcinoma (HCT116) cell growth in 10 synthesized 5-O-acyl juglones. C12:0-Acyl juglone was the strongest inhibitor of DNA repair-related pol λ, as well as the strongest suppression of the production of tumor necrosis factor (TNF)-α production induced by lipopolysaccharide (LPS) in the compounds tested. Moreover, this compound caused the greatest reduction in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced acute inflammation in mouse ears. C12:0- and C18:1-Acyl juglones selectively inhibited the activities of mammalian pol species, but did not influence the activities of other pols and DNA metabolic enzymes tested. These data indicate that the novel 5-O-acyl juglones target anti-cancer and/or anti-inflammatory agents based on mammalian pol inhibition. Moreover, the results suggest that acylation of juglone is an effective chemical modification to improve the anti-cancer and anti-inflammation of vitamin K(3) derivatives, such as juglone.

Simultaneous detection of pro- and antioxidative effects in the variants of the deoxyribose degradation assay

Interest in the redox properties of natural products has led to the development of various assays for the detection of antioxidant activities and ROS-scavenging properties. Here, additional modifications of the 2-deoxy-d-ribose degradation assay are introduced that specifically allow the determination of interactions of the test compound with the autoxidation of ascorbic acid and the autoxidation of the test compound itself. To illustrate this, juglone and quercetin were used as examples. The modified assay systems provide insights into their specific antioxidative and pro-oxidative properties. In additional, an extensive characterization of the redox properties of their complex with iron is possible, if iron ions are added in the free form or complexed with EDTA. The juglone-iron complex proved to be pro-oxidative in a wider range of milieus than the quercetin-iron complex.

Occurrence and fate of the phytotoxin juglone in alley soils under black walnut trees

Juglone (5-hydroxy-1,4-napthoquinone) is a chemical released by walnut trees, which can be toxic at various levels to several plant species. A balance among competing source and sink mechanisms and rates will ultimately determine whether juglone is capable of attaining sufficient levels to be allelopathic to intercrops in a walnut tree agroforestry system. In this study, juglone's release, accumulation, and decline in soil are explored using data from soil beneath a black walnut tree (Juglans nigra L) alley cropping system, greenhouse pot studies, and laboratory sorption/degradation studies. Juglone pore water concentrations estimated from extracts of surficial soil from beneath the alley cropping system exceeded the lowest solution culture toxicity levels reported for some plants of 10(-7) M, but did not exceed the inhibition threshold reported for typical intercrops such as maize and soybeans 10(-5) M. Further assessment of the likely persistence of juglone in soils indicated that juglone is both microbially and abiotically degraded, and that it will be particularly short-lived in soils supporting microbial activity. However, walnut seedlings planted in sand-filled pots clearly showed that juglone is released in measurable quantities to the soil's rhizosphere. Therefore, juglone accumulation in low fertility soils is plausible, and may still be worthy of consideration in management of alley agroforestry systems.

Insight into naphthoquinone metabolism: beta-glucosidase-catalysed hydrolysis of hydrojuglone beta-D-glucopyranoside

In plants, the naphthoquinone juglone is known to be involved in pathogenic defence mechanisms, but it may also take part in plant developmental processes. This naphthoquinone can accumulate in a glycosylated form, namely hydrojuglone beta-d-glucopyranoside. The structural configuration of this compound was shown to be 1, 5-dihydroxy-4-naphthalenyl-beta-d-glucopyranoside by means of MS, NMR and nuclear Overhauser effect spectroscopy analyses. A hydrojuglone beta-d-glucopyranoside beta-glucosidase (EC 3.2.1.21) was purified to homogeneity from Juglans regia L. The enzyme catalysed the release of juglone from hydrojuglone beta-d-glucopyranoside with high specificity and showed Michaelis-Menten kinetics with Km=0.62 mM and Vmax=14.5 microkat/mg of protein. This enzyme also showed a higher activity towards beta-d-fucosyl than beta-d-glucosyl bonds. The purified enzyme had an apparent Mr of 64000 by SDS/PAGE and a pI 8.9 by isoelectrofocusing PAGE. The purified enzyme was inhibited by several bivalent cations, such as Cu2+, Fe2+, Hg2+, and by d-glucono-1,5-lactone, showing non-competitive inhibition of the mixed type.