Structure-activity relationships of analogs of 3,4,5-trimethylfuran-2(5H)-one with germination inhibitory activities

The Impact of Post-Fire Smoke on Plant Communities: A Global Approach

Smoke is one of the fire-related cues that can alter vegetation communities' compositions, by promoting or excluding different plant species. For over 30 years, smoke-derived compounds have been a hot topic in plant and crop physiology. Research in this field was initiated in fire-prone areas in Australia, South Africa and some countries of both Americas, mostly with Mediterranean-type climates. Then, research extended to regions with moderate climates, like Central European countries; this was sometimes determined by the fact that in those regions, extensive prescribed or illegal burning (swailing) occurs. Hence, this review updates information about the effects of smoke compounds on plant kingdoms in different regions. It also focuses on research advances in the field of the physiological effects of smoke chemicals, mostly karrikins, and attempts to gather and summarize the current state of research and opinions on the roles of such compounds in plants' lives. We finish our review by discussing major research gaps, which include issues such as why plants that occur in non-fire-prone areas respond to smoke chemicals. Have recent climate change and human activities increased the risk of wildfires, and how may these affect local plant communities through physiologically active smoke compounds? Is the response of seeds to smoke and smoke compounds an evolutionarily driven trait that allows plants to adapt to the environment? What can we learn by examining post-fire smoke on a large scale?

Enantioselective Lactonization by π-Acid-Catalyzed Allylic Substitution: A Complement to π-Allylmetal Chemistry

Asymmetric allylic alkylation (AAA) is a powerful method for the formation of highly useful, non-racemic allylic compounds. Here we present a complementary enantioselective process that generates allylic lactones via π-acid catalysis. More specifically, a catalytic enantioselective dehydrative lactonization of allylic alcohols using a novel Pd^II -catalyst containing the imidazole-based P,N-ligand (S)-StackPhos is reported. The high-yielding reactions are operationally simple to perform with enantioselectivities up to 99 % ee. This strategy facilitates the replacement of a poor leaving group with what would ostensibly be a better leaving group in the product avoiding complications arising from racemization by equilibration.

Smoke-water commonly induces hormetic dose responses in plants

A detailed evaluation was made of the literature concerning the dose response features of smoke-water extracts and other types of biological pyrolysis products on seed germination and plant growth. The evaluation was undertaken to extend our research on the occurrence and importance of hormesis in plant biology, as no similar assessment on smoke water biology had been published and that a preliminary survey suggested widespread occurrence of hormesis. It was determined that hormetic-like biphasic dose responses were commonly reported within the smoke-water plant literature for seed germination and plant growth. These findings were independent of the type of plant evaluated, the type of plant material used for the smoke-water extract, and the process of pyrolysis and extraction. The magnitude of the maximal stimulation of the biphasic dose responses was consistent with the hormetic concept, with maximal responses typically being approximately 30-60% greater than control values and with a stimulatory dose/concentration width less than 10 fold. These findings, which represent dose response features of a spectrum of novel and chemically diverse complex mixtures, support the generality of the hormetic dose response and its potential utility in enhancing the quality of study designs, including selection of dose/concentration number and spacing as well as biological model and endpoint.

A Raf-like kinase is required for smoke-induced seed dormancy in Arabidopsis thaliana

Plants sense and integrate diverse stimuli to determine the timing for germination. A smoke compound, 3,4,5-trimethylfuran-2(5H)-one (trimethylbutenolide, TMB), has been identified to inhibit the seed germination of higher plants. To understand the mode of action, we examined various physiological and molecular aspects of the TMB-dependent inhibition of seed germination in Arabidopsis thaliana The results indicated that the effect of TMB is due to the enhanced physiological dormancy, which is modulated by other dormancy regulatory cues such as after-ripening, stratification, and ABA/GA signaling. In addition, gene expression profiling showed that TMB caused genome-wide transcriptional changes, altering the expression of a series of dormancy-related genes. Based on the TMB-responsive physiological contexts in Arabidopsis, we performed mutant screening to isolate genetic components that underpin the TMB-induced seed dormancy. As a result, the TMB-RESISTANT1 (TES1) gene in Arabidopsis, encoding a B2 group Raf-like kinase, was identified. Phenotypic analysis of the tes1 mutant implicated that TES1 has a critical role in the TMB-responsive gene expression and the inhibition of seed germination. Taken together, we propose that plants have been equipped with a TMB sensory pathway through which the TMB induces the seed dormancy in a TES1-dependent way.

Plant-Derived Smoke Affects Biochemical Mechanism on Plant Growth and Seed Germination

The role of plant-derived smoke, which is changed in mineral-nutrient status, in enhancing germination and post-germination was effectively established. The majority of plant species positively respond to plant-derived smoke in the enhancement of seed germination and plant growth. The stimulatory effect of plant-derived smoke on normally growing and stressed plants may help to reduce economic and human resources, which validates its candidature as a biostimulant. Plant-derived smoke potentially facilitates the early harvest and increases crop productivity. Karrikins and cyanohydrin are the active compound in plant-derived smoke. In this review, data from the latest research explaining the effect of plant-derived smoke on morphological, physiological, biochemical, and molecular responses of plants are presented. The pathway for reception and interaction of compounds of plant-derived smoke at the cellular and molecular level of plant is described and discussed.

Natural Compound-derived Cytochrome bc1 Complex Inhibitors as Antifungal Agents

The high incidence of fungal pathogens has become a global issue for crop protection. A promising strategy to control fungal plant infections is based on the use of nature-inspired compounds. The cytochrome bc1 complex is an essential component of the cellular respiratory chain and is one of the most important fungicidal targets. Natural products have played a crucial role in the discovery of cytochrome bc1 inhibitors, as proven by the development of strobilurins, one of the most important classes of crop-protection agents, over the past two decades. In this review, we summarize advances in the exploration of natural product scaffolds for the design and development of new bc1 complex inhibitors. Particular emphasis is given to molecular modeling-based approaches and structure-activity relationship (SAR) studies performed to improve the stability and increase the potency of natural precursors. The collected results highlight the versatility of natural compounds and provide an insight into the potential development of nature-inspired derivatives as antifungal agents.

Two new norsesquiterpenoids with estrogenic activity from the stems and leaves of Dioscorea oppositifolia L

Two new norsesquiterpenoids, dioscopposin A (1) and dioscopposin B (2), as well as 21 known compounds (3-23) were isolated from the stems and leaves of Dioscorea oppositifolia L. Their structures were elucidated by detailed analysis of comprehensive spectroscopic data. The absolute configurations were deduced by the comparison of experimental and calculated electronic circular dichroism spectra. Estrogenic activity of all the isolated compounds were evaluated using MCF-7 cells proliferation assay and compounds 2, 3, 7, 13, 15, 16, 18 and 21 exhibited proliferation activity.

Synthesis of potent neuroprotective butenolides based on plant smoke derived 3,4,5-Trimethylfuran-2(5H)-one and 3-methyl-2H-furo[2,3-c]pyrone-2-one

Smoke derived karrikinolide and trimethylbutenolide exerted neuroprotective effects against monoamine oxidase and acetylcholinesterase. Synthesis of potent analogs was achieved. Sulphur substitution in the bicyclic ring structure of KAR₁ displayed the most encouraging activity returning IC₅₀ values of 13.75 ± 0.001 μM and 0.03 ± 0.02 μM for monoamine oxidase A and B and 0.08 ± 0.006 μM for acetylcholinesterase. Neuroprotective butenolides may be particularly useful in the treatment of depressive disorders, Alzheimer's and Parkinson's diseases.

Swailing affects seed germination of plants of European bio-and agricenosis in a different way

Swailing as a part of agricultural practice is an illegal habit in many European countries. The indirect effect of swailing is the emission of volatiles (SGV), hence the aim of the study was to identify their impact to seeds of different species occurring or grown Europe. It was carried out on seeds of 29 species of 10 botanical families within the angiosperms. The response to SGV was more or less differentiated within a family, and even within the species, e.g. in the case of tomato. The stimulation of germination and/or increased seedling vigour was established in celery, green- and red-leafed basil, white and red cabbage, white clover and wild thyme. The same effect was noticed for the seeds of stratified broadleaf plantain and the positively photoblastic seeds of German chamomile germinated in darkness. The inhibition of seed germination and/ or reduced seedling vigour was demonstrated in case of caraway, dill and forget-me-not. Similar results were obtained in the experiments carried outin vitroand in the soil, hence it can be assumed that the indirect impact of SGV on plant habitat composition is likely. The interaction of SGV compounds with seed testa and seed phytohormones is discussed.