Metabolic disturbance and phytochemical changes in Andrographis paniculata and possible action mode of andrographolide

Objecive: To explore the effect of gibberellic acid(GA_3) and its inhibitor paclobutrazol(PBZ)on chemical composition and their pharmacological effects on Andrographis paniculata(Burm.f.) Wall. ex Nees, and to clarify action mode of andrographolide.Methods: The chemical composition was extracted by sequential extraction with hexane, dichloromethane, ethyl acetate and methanol, respectively. Andrographolide and its derivatives were evaluated by HPLC. Moreover, the metabolic profiling was analyzed by GC-MS. Inhibitory effect of crude extracts was tested against Staphylococcus aureus using agar well diffusion method. Mode of action was tested against mutant yeast by spotting assay. Andrographolide were tested for their mode of action against eukaryotes. Rsults: Among different solvents, dichloromethane gave the highest yield of crude(3.58% DW), with the highest andrographolide content(8.3 mg/g DW). The effect of plant hormone(10 mg/L GA_3 or PBZ) on phytochemical variations and bioactivity of Andrographis paniculata was demonstrated. It was found that PBZ promoted sesquiterpene compounds about 3.5 times over than GA_3 treatment. But inhibitory effect of extracts against Staphylococcus aureus was highest in GA_3 treated plants; andrographolide and 14-deoxy-11,12-didehydroandrographolide contents were significantly higher than those of water or PBZ. It was found that there were 11 strains involving in ergosterol biosynthesis, V-ATPase activity and homeostasis, and superoxide detoxification process. In this regard, andrographolide might cause the damage on the lipid bilayer of yeast cell and plasma membrane by interfering ergosterol biosynthesis.Conclusions: It is found that GA_3 promotes andrographolide and 14-deoxy-11,12-didehydroandrographolide content while PBZ promotes sesquiterpene content. Andrographolide might cause the damage on the lipid bilayer of yeast cell and plasma membrane by interfering ergosterol biosynthesis. It might also affect mitochondria electron transport chain, leading to the occurrence of ROS, which can further harm cell organelles. However, the library screening is the first step to investigate mode of action of andrographolide.

Discovery for New Herbicide Sites of Action by Quantification of Plant Primary Metabolite and Enzyme Pools

No herbicide with a new molecular site of action(SOA)has been introduced since the 1980s.Since then,the widespread evolution of resistance of weeds to most commercial herbicides has greatly increased the need for herbicides with new SOAs.Two untried strategies for the discovery on new herbicide SOAs are discussed.Some primary metabolism intermediates are phytotoxic(e.g.,protoporphyrin IX and sphingoid bases),and,because of this,the in vivo concentrations of these compounds are maintained at very low levels by plants.The determination of all primary metabolite phytotoxicities and pool sizes will identify targets of interest.Targeting SOAs that result in accumulation of phytotoxic compounds is the first novel approach to herbicide discovery.The second approach is to identify potential SOAs with very low in vivo enzyme levels.We know that higher numbers of enzyme molecules for a SOA requires more herbicide to kill a plant.Modern proteomic methods can identify low enzyme level SOAs for biorational herbicide discovery.These approaches might be useful in discovery of herbicides more closely related to natural compounds and that can be used in lower doses.

Heparin-induced extracorporeal LDL-precipitation(HELP):Mode of action, safety and clinical experience(3)

Safety and practicability of the HELP procedure Compared to standard plasma exchange, HELP-apheresis is much better tolerated, primarily be-cause heparin rather than citrate is used for anti-coagulation and therefore problems due to hypercalce-mia do not play a role.……

Direct-fed microbes: A tool for improving the utilization of low quality roughages in ruminants

For many years, ruminant nutritionists and microbiologists have been interested in manipulating the microbial ecosystem of the rumen to improve production efficiency of different ruminant species. Removal and restriction of antibiotics subtherapeutic uses from ruminant diets has amplified interest in improving nutrient utilization and animal performance and search for more safe alternatives. Some bacterial and fungal microorganisms as a direct-fed microbial（DFM） can be the most suitable solutions. Microorganisms that are commonly used in DFM for ruminants may be classified mainly as lactic acid producing bacteria（LAB）, lactic acid utilizing bacteria（LUB）, or other microorganism＇s species like Lactobacillus, Bifidobacterium, Enterococcus, Streptococcus, Bacillus, Propionibacterium, Megasphaera elsdenii and Prevotellabryantii, in addition to some fungal species of yeast such as Saccharomyces and Aspergillus. A definitive mode of action for bacterial or fungal DFM has not been established; although a variety of mechanisms have been suggested. Bacterial DFM potentially moderate rumen conditions, and improve weight gain and feed efficiency. Fungal DFM may reduce harmful oxygen from the rumen, prevent excess lactate production, increase feed digestibility, and alter rumen fermentation patterns. DFM may also compete with and inhibit the growth of pathogens, immune system modulation, and modulate microbial balance in the gastrointestinal tract. Improved dry matter intake, milk yield, fat corrected milk yield and milk fat content were obtained with DFM administration. However, the response to DFM is not constant; depending on dosages, feeding times and frequencies, and strains of DFM. Nonetheless, recent studies have supported the positive effects of DFM on ruminant performance.

Genomic,transcriptomic,and metabolomic analysis of Oldenlandia corymbosa reveals the biosynthesis and mode of action of anti-cancer metabolites

Plants accumulate a vast array of secondary metabolites,which constitute a natural resource for pharmaceuticals.Oldenlandia corymbosa belongs to the Rubiaceae family,and has been used in traditional medicine to treat different diseases,including cancer.However,the active metabolites of the plant,their biosynthetic pathway and mode of action in cancer are unknown.To fill these gaps,we exposed this plant to eight different stress conditions and combined different omics data capturing gene expression,metabolic profiles,and anti-cancer activity.Our results show that O.corymbosa extracts are active against breast cancer cell lines and that ursolic acid is responsible for this activity.Moreover,we assembled a high-quality genome and uncovered two genes involved in the biosynthesis of ursolic acid.Finally,we also revealed that ursolic acid causes mitotic catastrophe in cancer cells and identified three high-confidence protein binding targets by Cellular Thermal Shift Assay(CETSA)and reverse docking.Altogether,these results constitute a valuable resource to further characterize the biosynthesis of active metabolites in the Oldenlandia group,while the mode of action of ursolic acid will allow us to further develop this valuable compound.

Discovery of Novel Anthranilic Diamide Derivatives Bearing Sulfoximine Group as Potent Insecticide Candidates

The fall armyworm,Spodoptera frugiperda(S.frugiperda),represents the most resistant insect species and poses serious threat to grain yield.Chlorantraniliprole(CHL),which targets the ryanodine receptors(RyRs)in insects,has demonstrated the efficacy in controlling S.frugiperda.Nevertheless,this has led to emerging resistance in several countries.To counter this resistance,a viable approach involves the development of novel compounds that bind against RyRs via distinct binding sites or modes.In this study,a series of 22 novel anthranilic diamide derivatives was designed and synthesized,and their insecticidal activities were evaluated.Most of these derivatives showed moderate to good insecticidal activity against S.frugiperda and Mythimna separata.Time-lapse fluorescence measurements of endoplasmic reticulum luminal calcium revealed that most derivatives elicited cellular responses similar as CHL when assessed on HEK293 cells expressing S.frugiperda ryanodine receptors(SfRyRs).The mode of action of compound 13a was studied and verified on the isolated neurons by calcium imaging technique.Finally,molecular docking analysis was employed to predict the binding mechanism of compound 13a against SfRyRs.Overall,these novel diamide derivatives hold promise as a valuable resource for guiding the future design of insecticidal compounds targeting RyRs.

Evolution and development of potent monobactam sulfonate candidate IMBZ18g as a dual inhibitor against MDR Gram-negative bacteria producing ESBLs

A series of new monobactam sulfonates is continuously synthesized and evaluated for their antimicrobial efficacies against Gram-negative bacteria.Compound 33a(IMBZ18G)is highly effective in vitro and in vivo against clinically intractable multi-drug-resistant(MDR)Gram-negative strains,with a highly druglike nature.The checkerboard assay reveals its significant synergistic effect withβ-lactamase inhibitor avibactam,and the MIC values against MDR enterobacteria were reduced up to 4—512folds.X-ray co-crystal and chemoproteomic assays indicate that the anti-MDR bacteria effect of 33a results from the dual inhibition of the common PBP3 and some class A and Cβ-lactamases.Accordingly,preclinical studies of 33a alone and 33a-avibactam combination as potential innovative candidates are actively going on,in the treatment ofβ-lactamase-producing MDR Gram-negative bacterial infections.

Effects and mechanisms of Bacillus thuringiensis crystal toxins for mosquito larvae

Bacillus thuringiensis is a Gram-positive aerobic bacterium that produces insecticidal crystalline inclusions during sporulation phases of the mother cell. The vir- ulence factor, known as parasporal crystals, is composed of Cry and Cyt toxins. Most Cry toxins display a common 3-domain topology. Cry toxins exert intoxication through toxin activation, receptor binding and pore formation in a suitable larval gut environment. The mosquitocidal toxins of Bt subsp, israelensis （Bti） were found to be highly active against mosquito larvae and are widely used for vector control. Bt subsp, jegathesan is another strain which possesses high potency against broad range of mosquito larvae. The present review summarizes characterized receptors for Cry toxins in mosquito larvae, and will also discuss the diversity and effects of 3-D mosquitocidal Cry toxin and the ongo- ing research for Cry toxin mechanisms generated from investigations of lepidopteran and dipteran larvae.

Comparison on effect of hydrophobicity on the antibacterial and antifungal activities of α-helical antimicrobial peptides

HPRP-A1, a 15-mer α-helical cationic peptide, was derived from N-terminus of ribosomal protein L1 (RpL1) of Helicobacter pylori. In this study, HPRP-A1 was used as a framework to obtain a series of peptide analogs with different hydrophobicity by single amino acid substitutions in the center of nonpolar face of the amphipathic helix in order to systematically study the effect of hydrophobicity on biological activities of -helical antimicrobial peptides. Hydrophobicity and net charge of peptides played key roles in the biological activities of these peptide analogs; HPRP-A1 and peptide analogs with relative higher hydrophobicity exerted broad spectrum antimicrobial activity against Gram-negative bacteria, Gram-positive bacteria and pathogenic fungi, but also showed stronger hemolytic activity; the change of hydrophobicity and net charge of peptides had similar effects with close trend and extent on antibacterial activities and antifungal activities. This indicated that there were certain correlations between the antibacterial mode of action and the antifungal mode of action of these peptides in this study. The peptides exhibited antimicrobial specificity for bacteria and fungi, which provided potentials to develop new antimicrobial drugs for clinical practices.

Integrated view of plant metabolic defense with particular focus on chewing herbivores

Success of plants largely depends on their ability to defend against herbivores.Since emergence of the first voracious consumers,plants maintained adapting their structures and chemistry to escape from extinction.The constant pressure was further accelerated by adaptation of herbivores to plant defenses,which all together sparked the rise of a chemical empire comprised of thousands of specialized metabolites currently found in plants.Metabolic diversity in the plant kingdom is truly amazing,and although many plant metabolites have already been identified,a large number of potentially useful chemicals remain unexplored in plant bioresources.Similarly,biosynthetic routes for plant metabolites involve many enzymes,some of which still wait for identification and biochemical characterization.Moreover,regulatory mechanisms that control gene expression and enzyme activities in specialized metabolism of plants are scarcely known.Finally,understanding of how plant defense chemicals exert their toxicity and/or repellency against herbivores remains limited to typical examples,such as proteinase inhibitors,cyanogenic compounds and nicotine.In this review,we attempt summarizing the current status quo in metabolic defense of plants that is predominantly based on the survey of ubiquitous examples of plant interactions with chewing herbivores.

Crystal structure of Arabidopsis thaliana HPPK/DHPS,a bifunctional enzyme and target of the herbicide asulam

Herbicides are vital formodern agriculture,but their utility is threatened by genetic or metabolic resistance in weeds,as well as regulatory barriers.Of the known herbicide modes of action,7,8-dihydropterin synthase(DHPS),which is involved in folate biosynthesis,is targeted by just one commercial herbicide,asulam.A mimic of the substrate para-aminobenzoic acid,asulam is chemically similar to sulfonamide antibiotics,and although it is still in widespread use,asulam has faced regulatory scrutiny.With an entire mode of action represented by just one commercial agrochemical,we sought to improve the understanding of its plant target.Here we solve a 2.3A°resolution crystal structure for Arabidopsis thaliana DHPS that is conjoined to 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase(HPPK),and we reveal a strong structural conservation with bacterial counterparts at the sulfonamide-bindingpocket of DHPS.We demonstrate that asulamand the antibiotic sulfamethoxazole have herbicidal as well as antibacterial activity,andwe explore the structural basis of their potency by modeling these compounds in mitochondrial HPPK/DHPS.Our findings suggest limited opportunity for the rational design of plant selectivity fromasulamand indicate that pharmacokinetic or delivery differences between plants andmicrobesmight be the bestways to safeguard thismode of action.