Design, Synthesis, and In Vitro and In Vivo Biological Evaluation of Limonin Derivatives for Anti-Inflammation Therapy

In this study, limonin derivatives were used to design new anti-inflammatory compounds with high pharmacological activity and low toxicity. A total of 23 new limonin derivatives were discovered, synthesized, and screened for their anti-inflammatory activity against lipopolysaccharide (LPS)-treated RAW 264.7 cells. Of them, compound f4 was found to be the most active, with a higher efficiency compared with limonin and celecoxib. Subsequently, we studied the mechanism underlying the activity of f4 and found that it inhibited proinflammatory cytokines by blocking the NF-κB/MAPK signaling pathway in LPS-treated RAW 264.7 cells as well as mice. In conclusion, f4 may be a promising anti-inflammatory lead compound.

Recent Progress in Oleanolic Acid: Structural Modification and Biological Activity

Natural products have been proven as the main source of biologically active compounds, which are potentially useful for drug development. As one of the most studied pentacyclic triterpenes, oleanolic acid (OA) exhibits a broad range of biological activities and serves as a good scaffold for the development of novel derivatives that could be vital in drug discovery for various ailments. Up to now, many of its derivatives with multiple bioactivities have been prepared through chemical modification. This review summarizes the recent reports of OA derivatives (2016-present) and their biological effects and action mechanisms in vitro and in vivo models, and discusses the design of novel and potent derivatives.

Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-N-oxide Urea) Gelators

The structural modification of existing supramolecular architecture is an efficient strategy to design and synthesize supramolecular gels with tunable and predictable properties. In this work, we have modified bis(pyridyl urea) compounds with different linkers, namely hexylene and butylene, to their corresponding bis(pyridyl-N-oxide urea). The gelation properties of both the parent and the modified compounds were studied, and the results indicated that modification of the 3-pyridyl moieties to the corresponding 3-pyridyl-N-oxides induced hydrogelation. The stability of the parent and modified compounds were evaluated by sol-gel transition temperature (T_gel) and rheological measurements, and single-crystal X-ray diffraction was used to analyze the solid-state interactions of the gelators. The morphologies of the dried gels were analyzed by scanning electron microscopy (SEM), which revealed that the structural modification did not induce any prominent effect on the gel morphology. The stimuli-responsive behavior of these gels in the presence of salts in DMSO/water was evaluated by rheological experiments, which indicated that the modified compounds displayed enhanced gel strength in most cases. However, the gel network collapsed in the presence of the chloride salts of aluminum(III), zinc(II), copper(II), and cadmium(II). The mechanical strength of the parent gels decreased in the presence of salts, indicating that the structural modification resulted in robust gels in most cases. The modified compounds formed gels below minimum gel concentration in the presence of various salts, indicating salt-induced gelation. These results show the making and breaking ability of the gel network in the presence of external stimuli (salts), which explains the potential of using LMWGs based on N-oxide moieties as stimuli-responsive materials.

Strong Structural Modification of Gd to Co3O4 for Catalyzing N2O Decomposition under Simulated Real Tail Gases

In this paper, Gd-promoted Co₃O₄ catalysts were prepared via a facile coprecipitation method for low-temperature catalytic N₂O decomposition. Due to the addition of Gd, the crystallite size of Co₃O₄ in the Gd_0.06Co catalyst surprisingly decreased to 4.9 nm, which is much smaller than most additive-modified Co₃O₄ catalysts. This huge change in the catalyst's textural structure endows the Gd_0.06Co catalyst with a large specific surface area, plentiful active sites, and a weak Co-O bond. Hence, Gd_0.06Co exhibited superior activity for catalyzing 2000 ppmv N₂O decomposition, and the temperature for the complete catalytic elimination of N₂O was as low as 350 °C. Meanwhile, compared with pure Co₃O₄, E_a decreased from 77.4 to 46.8 kJ·mol^-1 and TOF of the reaction increased from 1.16 × 10^-3 s^-1 to 5.13 × 10^-3 s^-1 at 300 °C. Moreover, Gd_0.06Co displayed a quite stable catalytic performance in the presence of 100 ppmv NO, 5 vol % O₂, and 2 vol % H₂O.

Mangiferin: a review of dietary sources, absorption, metabolism, bioavailability, and safety

Mangiferin is a potential candidate for use in nutraceutical and functional food applications due to its numerous bioactivities. However, the low bioavailability of mangiferin is a major limitation for establishing efficacy for use. This review describes current information on known food sources and factors that influence mangiferin contents, absorption, and metabolism features, and recent progress that has come from research efforts to increase the bioavailability of mangiferin. We also list patents that targeted to enhance mangiferin bioavailability. Mangifera indica L. is the major dietary source for mangiferin, a xanthone that varies widely in different parts of the plant and is influenced by many factors that involve plant propagation and post-harvest processing. Mangiferin absorption occurs mostly in the small intestine by passive diffusion with varying absorption capacities in different segments of the gastrointestinal tract. Recent research has led to the development of novel technologies to encapsulate mangiferin in nano/microparticle carrier systems as well as generate mangiferin derivatives to improve solubility and bioavailability. Preclinical studies reported that mangiferin < 2000 mg/kg is generally nontoxic. The safety and the increase in bioavailability are key limiting factors for developing successful applications for mangiferin as a nutritional dietary supplement or nutraceutical.

Design, Synthesis, and Antibacterial Evaluation of Novel Ocotillol Derivatives and Their Synergistic Effects with Conventional Antibiotics

The improper use of antibiotics has led to the development of bacterial resistance, resulting in fewer antibiotics for many bacterial infections. Especially, the drug resistance of hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA) is distinctly serious. This research designed and synthesized two series of 3-substituted ocotillol derivatives in order to improve their anti-HA-MRSA potency and synergistic antibacterial activity. Among the synthesized compounds, 20–31 showed minimum inhibitory concentration (MIC) values of 1–64 µg/mL in vitro against HA-MRSA 18–19, 18–20, and S. aureus ATCC29213. Compound 21 showed the best antibacterial activity, with an MIC of 1 μg/mL and had synergistic inhibitory effects. The fractional inhibitory concentration index (FICI) value was 0.375, when combined with chloramphenicol (CHL) or kanamycin (KAN). The structure–activity relationships (SARs) of ocotillol-type derivatives were also summarized. Compound 21 has the potential to be developed as a novel antibacterial agent or potentiator against HA-MRSA.

Pharmacokinetics and brain distribution studies of 6-hydroxykynurenic acid and its structural modified compounds

OBJECTIVES

6-Hydroxykynurenic acid (6-HKA) is an organic acid component in extracts of Ginkgo biloba leaves and acts as a major contributor to neurorestorative effects, while its oral bioavailability was low. Therefore, using prodrug method to improve the bioavailability and brain content of 6-HKA is significant.

METHODS

Three structural modified compounds of 6-HKA were synthesized, and ultra performance liquid chromatography-tandem mass spectrometry methods for quantification of these structural modified compounds in rat plasma and rat brain homogenate were established and comprehensively validated. The methods were effectively applied to investigate the effects of structural modification on apparent permeability coefficients in cells, the pharmacokinetics and the brain distribution in rats.

KEY FINDINGS

The results illustrated that esterification can greatly improve the apparent permeability coefficient and bioavailability of 6-HKA. Comparing with direct oral administration of 6-HKA, the bioavailability of isopropyl ester was greatly improved (from 3.96 ± 1.45% to 41.8 ± 15.3%), and the contents of 6-HKA in rat brains (49.7 ± 9.2 ng/g brain) were significantly higher after oral administration.

CONCLUSIONS

The bioavailability and the brain content of 6-HKA can be improved by the prodrug method. Among three structural modified compounds, isopropyl-esterified 6-HKA was the most promising treatment.

The development of novel cytochrome P450 2J2 (CYP2J2) inhibitor and the underlying interaction between inhibitor and CYP2J2

Human Cytochrome P450 2J2 (CYP2J2) as an important metabolic enzyme, plays a crucial role in metabolism of polyunsaturated fatty acids (PUFAs). Elevated levels of CYP2J2 have been associated with various types of cancer, and therefore it serves as a potential drug target. Herein, using a high-throughput screening approach based on enzymic activity of CYP2J2, we rapidly and effectively identified a novel natural inhibitor (Piperine, 9a) with IC₅₀ value of 0.44 μM from 108 common herbal medicines. Next, a series of its derivatives were designed and synthesised based on the underlying interactions of Piperine with CYP2J2. As expected, the much stronger inhibitors 9k and 9l were developed and their inhibition activities increased about 10 folds than Piperine with the IC₅₀ values of 40 and 50 nM, respectively. Additionally, the inhibition kinetics illustrated the competitive inhibition types of 9k and 9l towards CYP2J2, and K_i were calculated to be 0.11 and 0.074 μM, respectively. Furthermore, the detailed interaction mechanism towards CYP2J2 was explicated by docking and molecular dynamics, and our results revealed the residue Thr114 and Thr 315 of CYP2J2 were the critical sites of action, moreover the spatial distance between the carbon atom of ligand methylene and Fe atom of iron porphyrin coenzyme was the vital interaction factor towards human CYP2J2.

Surface-Enhanced Raman Spectroscopy for Molecule Characterization: HIM Investigation into Sources of SERS Activity of Silver-Coated Butterfly Scales

Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for obtaining structural information of molecules in solution at low concentrations. While commercial SERS substrates are available, high costs prevent their wide-spread use in the medical field. One solution is to prepare requisite noble metal nanostructures exploiting natural nanostructures. As an example of biomimetic approaches, butterfly wing scales with their intricate nanostructures have been found to exhibit exquisite SERS activity when coated with silver. Selecting appropriate scales from particular butterfly species and depositing silver of certain thicknesses leads to significant SERS activity. For morphological observations we used scanning electron microscopes as well as a helium ion microscope, highly suitable for morphological characterization of poorly conducting samples. In this paper, we describe a protocol for carrying out SERS measurements based on butterfly wing scales and demonstrate its LOD with a common Raman reporter, rhodamine 6 G. We also emphasize what special care is necessary in such measurements. We also try to shed light on what makes scales work as SERS substrates by carefully modifying the original nanostructures. Such a study allows us to either use scales directly as a raw material for SERS substrate or provides an insight as to what nanostructures need to be recreated for synthetic SERS substrates.

Effort of ionic radius on doped style of silver and copper/zinc oxide nanorods for photodegradation of methylene blue

The homogeneous Cu-ZnO and heterogeneous Ag/ZnO nanorods were synthesised by controlling the ionic radius of Cu and Ag with lattice of ZnO. The structure of Cu-ZnO and Ag/ZnO was investigated by a series of methods. The study of the photoelectric properties suggested both the homogeneously and heterogeneously doped ZnO displayed an increased photocatalytic performance. It was worth noting that the Cu-ZnO and Ag/ZnO composites shown different degradation activities of methylene blue under the visible and UV light irradiation. The data suggested that the Cu species incorporated into the crystal lattice of ZnO nanorods could promote the utilisation of visible light, leading to 2.5- and 2.7-fold increase in the degradation rates compared with Ag/ZnO and ZnO nanorods. However, when UV light was employed, on the one hand, the significant increase of the activity for both Cu-ZnO and Ag/ZnO compared with ZnO was observed and on the other hand, the degradation rate of Cu-ZnO was close to that of Ag/ZnO. The investigation suggested that the metallic Cu in the ZnO crystal lattice could promote the separation of electrons and holes generated by ZnO under visible light. As for the UV light, both doping styles could favour the separation process. The present work could provide a further insight for the design of ZnO-based nanomaterials and development of their applications in environmental catalysis.

Optimization of Osthole in the Lactone Ring: Structural Elucidation, Pesticidal Activities, and Control Efficiency of Osthole Ester Derivatives

Here, we prepared a series of novel osthole-type ester derivatives modified in the lactone ring of osthole, which is isolated from Cnidium monnieri. The positions of H-3 and H-4 of the representative compound 4z were determined by a ¹H-¹H COSY spectrum. By opening the lactone ring of osthole, the double bonds at the C-3 and C-4 positions of diol 3 and esters 4a-4z, 4a', and 4b' were still retained as a Z configuration. That is, H-3 and H-4 of compounds 3 and 4a-4z, 4a', and 4b' were all in the cis relationship. The steric configurations of 4k, 4v, and 4z were further undoubtedly determined by single-crystal X-ray diffraction. Against Tetranychus cinnabarinus Boisduval, four aliphatic esters 4c (R = n-C₃H₇; LC₅₀: 0.31 mg/mL), 4d (R = CH₃(CH₂)₁₀; LC₅₀: 0.24 mg/mL), 4a' (R = CH₃(CH₂)₉; LC₅₀: 0.28 mg/mL), and 4b' (R = CH₃(CH₂)₁₂; LC₅₀: 0.32 mg/mL) showed the most promising acaricidal activity, and compounds 4c, 4d, and 4a' also exhibited a potent control efficiency. Especially, compound 4d exhibited greater than fivefold acaricidal activity of the precursor osthole (LC₅₀: 1.22 mg/mL). Against Mythimna separata Walker, compounds 4g, 4l, and 4m displayed 1.6-1.8-fold potent insecticidal activity of osthole. It demonstrated that the lactone ring of osthole is not necessary for the agricultural activities, thiocarbonylation of osthole was not beneficial for the agricultural activities, introduction of R as an aliphatic chain is vital for the acaricidal activity, notably, the length of the aliphatic chain is related to the acaricidal activity, 4d could be further studied as a lead acaricidal agent, and to the aromatic series, R containing the fluorine atom(s) is important for the insecticidal activity.

Tanshinones: An Update in the Medicinal Chemistry in Recent 5 Years

Tanshinones are an important type of natural products isolated from Salvia miltiorrhiza Bunge with various bioactivities. Tanshinone IIa, cryptotanshinone and tanshinone I are three kinds of tanshinones which have been widely investigated. Particularly, sodium tanshinone IIa sulfonate is a water-soluble derivative of tanshinone IIa and it is used in clinical in China for treating cardiovascular diseases. In recent years, there are increasing interests in the investigation of tanshinones derivatives in various diseases. This article presents a review of the anti-atherosclerotic effects, cardioprotective effects, anticancer activities, antibacterial activities and antiviral activities of tanshinones and structural modification work in recent years.

Design, synthesis, and antitumor activity evaluation of pretubulysin analogs

Pretubulysin, a biosynthetic precursor of the tubulysins, shows potent biological activity in a variety of tumor cell lines. Although there are several total synthesis routes to tubulysin and pretubulysin reported, the commercialization still has been hampered due to the complexity of the structure. To find structurally simpler pretubulysin analogs, a series of 2-(3-(methylamino)propyl)thiazole-4-carboxamides are designed and synthesized, and their anticancer activities are screened using MCF-7 (breast cancer), and NCI-H157 (lung cancer) cell lines. Taxol (IC₅₀  = 0.01 µM) and pretubulysin are used as the control. Compounds 8c (IC₅₀  = 0.05 µM, MCF-7; 0.09 µM, NCI-H157) and 8h (IC₅₀  = 0.01 µM, MCF-7; 0.02 µM, NCI-H157) exhibited certain antitumor activities comparable to those of Taxol. The urea analogs of pretubulysin might represent a promising scaffold for the further development of novel antitumor drugs.

Predictive hybrid paradigm for cytotoxic activity of 1,3,4-thiadiazole derivatives as CDK6 inhibitors against human (MCF-7) breast cancer cell line and its structural modifications: rational for novel cancer therapeutics

The dysregulation of cyclin-CDK6 interactions has been implicated in human breast cancer, providing a rationale for more therapeutic options. Recently, ATP-competitive inhibitors have been employed for managing breast cancer. These molecules, like most natural CDKs inhibitors, potently bind in the ATP-binding site of CDK6 to regulate trans-activation. Nonetheless, only a few numbers of these molecules are approved to mitigate breast cancer, thus, ensuring that the search for more selective inhibitors continues. In this study, we attempted to establish the selective predictive models for identifying potent CDK6 inhibitors against a human breast cancer cell-line using a dataset of fifty-two 1,3,4-thiadiazole derivatives. The significant eight descriptor hybrid QSAR models generated exhibited encouraging statistical attributes including R2> 0.70, Q²_LOO > 0.70, Q²_LMO > 0.60, Qfn2 > 0.6. Furthermore, the study designed new compounds based on the activity and structural basis for selectivity of compounds for CDK6. While demonstrating good potency and modest selectivity, the compound C16, which showed significantly high activity of 5.5607 µM and binding energy value of -9.0 Kcal/mol, was used as template for compounds design to generate 10 novel series of 1,3,4-thiadiazole analogues containing benzisoselenazolone scaffolds, with significant pharmacological activity and better selectivity for CDK6. By our rationale, four of the designed compounds (C16b, C16h, C16i, and C16j) with activity values of 6.2584 µM, 6.7812 µM, 6.4717 µM, and 6.2666 µM respectively, and binding affinities of -10.0 kcal/mol, -9.9 kcal/mol, -9.9 kcal/mol, and -9.9 kcal/mol respectively, may emerge as therapeutic options for breast cancer treatment after extensive in vitro and in vivo studies.Communicated by Ramaswamy H. Sarma.

Effect of methylglyoxal on the alteration in structure and digestibility of α-lactalbumin, and the formation of advanced glycation end products under simulated thermal processing

α-Dicarbonyl compounds (α-DCs) are a class of compounds generated during the thermal processing of food. Due to the high reactivity, α-DCs were endowed with the ability to react with food components thus lowering nutrition value and even leading to a potential risk for food safety. In this study, methylglyoxal (MG), the most abundant α-DCs, was selected to investigate the alteration effects on the structure and digestibility of α-lactalbumin (αLA) under thermal processing (60-100°C). The results showed that the modification degree of αLA by MG increased with the rise of processing temperature, accompanied by the significant changes in molecular weight, intrinsic fluorescence, and secondary structures of αLA. High-resolution mass spectrometry analysis identified that lysine (Lys) and arginine (Arg) are the modification sites, and Nε-(carboxyethyl)-L-lysine is the main modification type. Since the Lys and Arg are also the cleavage sites of trypsin, the digestibility of MG modified αLA (MG-αLA) by trypsin correspondingly decreased with an increase of processing temperature. The reacted Lys and Arg residues, and the protein-bound AGEs were quantified, and the contents were found to be highly dependent on the temperature.

Anti-Tumor Drug Discovery Based on Natural Product β-Elemene: Anti-Tumor Mechanisms and Structural Modification

Natural products are important sources for drug discovery, especially anti-tumor drugs. β-Elemene, the prominent active ingredient extract from the rhizome of Curcuma wenyujin, is a representative natural product with broad anti-tumor activities. The main molecular mechanism of β-elemene is to inhibit tumor growth and proliferation, induce apoptosis, inhibit tumor cell invasion and metastasis, enhance the sensitivity of chemoradiotherapy, regulate the immune system, and reverse multidrug resistance (MDR). Elemene oral emulsion and elemene injection were approved by the China Food and Drug Administration (CFDA) for the treatment of various cancers and bone metastasis in 1994. However, the lipophilicity and low bioavailability limit its application. To discover better β-elemene-derived anti-tumor drugs with satisfying drug-like properties, researchers have modified its structure under the premise of not damaging the basic scaffold structure. In this review, we comprehensively discuss and summarize the potential anti-tumor mechanisms and the progress of structural modifications of β-elemene.

The effect of structural modification of antimicrobial peptides on their antimicrobial activity, hemolytic activity, and plasma stability

In this article, a series of modifications were made on an antimicrobial peptide F_2,5,12 W, including altering the amino acid sequence, introducing cysteine and other typical amino acids, developing peptide dimers via disulfide bonds, and conjugating with mPEG, in order to enhance the antimicrobial activity, plasma stability, and reduce the hemolytic activity of peptides. The results showed that mPEG conjugation could significantly improve the plasma stability and reduce the hemolytic activity of peptides, while the antimicrobial activity decreased meanwhile. However, altering the sequence of the peptide without changing its amino acid composition had little impact on its antimicrobial activity and plasma stability. The introduction of cysteine enhanced the plasma stability of peptides conspicuously, but at the same time, the increased hydrophobicity of peptides increased their hemolysis. The antimicrobial mechanism and cytotoxicity of the peptides with relatively high antimicrobial activity were also studied. In general, this study provided some ideas for the rational design and structure optimization of antimicrobial peptides.

Design, Synthesis and Biological Evaluation of 1-methyl-1H-pyrazole-5-Carboxamide Derivatives as Novel Anti-Prostate Cancer Agents

BACKGROUND

The androgen receptor (AR) signaling functions is a critical driving force for the progression of prostate cancer (PCa) to bring about anti-prostate cancer agents, and AR has been proved to be an effective therapeutic target even for castration-resistant prostate cancer (CRPC).

OBJECTIVE

In order to discover novel anti prostate cancer agents, we performed structural modifications based on the lead compounds T3 and 10e.

METHODS

A set of 1-methyl- 1H-pyrazole-5-carboxamide derivatives were synthesized and evaluated for their inhibitory activities against both expressions of prostate-specific antigen(PSA) and growth of PCa cell lines.

RESULTS

Compound H24 was found to be able to completely block PSA expression at 10 µM, and showed prominent antiproliferative activity in both the LNCaP cell line (GI 50 = 7.73 µM) and PC-3 cell line (GI 50 = 7.07 µM).

CONCLUSIONS

These preliminary data supported a further evaluation of compound H24 as a potential agent to treat prostate cancer.

Synthesis of oleanolic acid analogues targeting PDGF receptor inhibitors and their antitumor biological activities

The PDGF receptor is mock-coupled with a known active compound, and 14 novel skeleton candidate compounds were designed and synthesized. The structure was confirmed by ¹H NMR, ¹³C NMR and MS. The in vitro cytotoxicity of the two cancer cell lines (SGC-7901 and A549) was evaluated by MTT assay. PDGF receptor protein inhibition assays were performed on I₆ and II₄ using fluorescence polarization immunoassay (FPIA). [Formula: see text].

[Application of sucrose phosphorylase in glycosylation]

Water solubility, stability, and bioavailability, can be substantially improved after glycosylation. Glycosylation of bioactive compounds catalyzed by glycoside hydrolases (GHs) and glycosyltransferases (GTs) has become a research hotspot. Thanks to their rich sources and use of cheap glycosyl donors, GHs are advantageous in terms of scaled catalysis compared to GTs. Among GHs, sucrose phosphorylase has attracted extensive attentions in chemical engineering due to its prominent glycosylation activity as well as its acceptor promiscuity. This paper reviews the structure, catalytic characteristics, and directional redesign of sucrose phosphorylase. Meanwhile, glycosylation of diverse chemicals with sucrose phosphorylase and its coupling applications with other biocatalysts are summarized. Future research directions were also discussed based on the current research progress combined with our working experience.

Role of N-Oxide Moieties in Tuning Supramolecular Gel-State Properties

The role of specific interactions in the self-assembly process of low molecular weight gelators (LMWGs) was studied by altering the nonbonding interactions responsible for gel formation via structural modification of the gelator/nongelator. This was achieved by modifying pyridyl moieties of bis(pyridyl) urea-based hydrogelator (4–BPU) and the isomer (3–BPU) to pyridyl N–oxide compounds (L₁ and L₂, respectively). The modification of the functional groups resulted in the tuning of the gelation properties of the parent gelator, which induced/enhanced the gelation properties. The modified compounds displayed better mechanical and thermal stabilities and the introduction of the N–oxide moieties had a prominent effect on the morphologies of the gel network, which was evident from the scanning electron microscopy (SEM) images. The effect of various interactions due to the introduction of N–oxide moieties in the gel network formation was analyzed by comparing the solid-state interactions of the compounds using single crystal X-ray diffraction and computational studies, which were correlated with the enhanced gelation properties. This study shows the importance of specific nonbonding interactions and the spatial arrangement of the functional groups in the supramolecular gel network formation.

Chemistry and Biofunctional Significance of Bioactive Peptide Interactions with Food and Gut Components

Food-derived bioactive peptides (BAPs) have gained significant interest as functional agents for developing food products with health benefits. To elucidate the underlying bioactivity mechanisms, current research investigates mostly the structure-activity relationship of native peptides. However, peptide structures are highly susceptible to chemical modifications, which can subsequently influence their physiological behaviors and bioactivities. This paper highlights the peptide structure modifications occurring with major food components during processing and the digestive environment of the gut as well as associated changes in peptide properties and biofunctions. Given the modification propensity of peptides, focus should be shifted toward characterizing the nature, biofunctions, gut activity, bioavailability, and safety of the modified peptides toward achieving pragmatic food applications of BAPs.

High Value-Added Use of Citrus Industrial Wastes in Agriculture: Semisynthesis and Anti-Tobacco Mosaic Virus/Insecticidal Activities of Ester Derivatives of Limonin Modified in the B Ring

Globally, the citrus industry produces various wastes, which contain a great deal of limonoids. In order for the sustainable development of the citrus industry, and considering the diverse bioactivities of limonoids, a series of ester derivatives were constructed by structural modification of limonin in the B ring. Furthermore, two seven-membered lactone derivatives of limonin and obacunone with a novel skeleton in the B ring were obtained by the Baeyer-Villiger oxidation rearrangement. The steric structures of six key compounds 3a, 3b, 4m, 4n, 6, and 7 were determined by X-ray crystallography. It demonstrated that the molar ratio of 3a (7α-isomer) and 3b (7β-isomer) depended on the mixed solvents in the reduction system. The anti-tobacco mosaic virus (TMV) activities under three different modes of action for most of the tested compounds were as the following sequence: inactivation effect > protection effect > curative effect. It was noteworthy that compound 4aa displayed the most potent anti-TMV/insect growth inhibitory activities, which indicated that the introduction of the phenylacryloyloxy group at the C-7β position of limonin could significantly improve its agricultural biological activities. This study will pave the way for future value-added application of citrus industrial wastes and provide strong evidence for the discovery of sustainable biopesticides based on limonoids.

Construction of oxime ester derivatives of osthole from Cnidium monnieri, and evaluation of their agricultural activities and control efficiency

BACKGROUND

In order to discover natural-product-based pesticidal candidates, a series of coumarin-like derivatives containing oxime ester fragments at the C-8 position were prepared by structural modification of osthole, a natural plant product isolated from Cnidium monnieri. Their pesticidal activities were evaluated against two typically fruit trees/crop-threatening agricultural pests, Mythimna separata Walker and Tetranychus cinnabarinus Boisduval.

RESULTS

Osthole was regioselectively oxidized by selenium dioxide to give the E-isomer, (2'E)-3'-formaldehydylosthole (2). Four key steric structures of 2, (2'E, 4'E)-(o-chloropyrid-3-ylcarbonyl)oximinylosthole (4o), (2'E, 4'E)-(styrylcarbonyl)oximinylosthole (4t), and (2'E, 4'E)-(acetyl)oximinylosthole (4w) were undoubtedly confirmed by X-ray crystallography. Against T. cinnabarinus, it is noteworthy that (2'E, 4'E)-(p-chlorophenylcarbonyl)oximinylosthole (4c) exhibited over three-fold more potent acaricidal activity of the precursor osthole, with especially good control efficiency observed in the glasshouse. Against M. separata, compounds 4c and (2'E, 4'E)-(p-nitrophenylcarbonyl)oximinylosthole (4f) showed the most pronounced growth inhibitory activity. The relationships between their structures and agricultural activities also were studied.

CONCLUSION

These results demonstrate that compound 4c could be further structurally modified as pesticidal agents. It will lay the foundation for future application of osthole derivatives as pesticides. © 2020 Society of Chemical Industry.

In vitro anti-trypanosomal potential of kaurane and pimarane semi-synthetic derivatives

As part of the search for anti-trypanosomal agents, this work presents the production of sixteen derivatives. All of them were obtained from two natural diterpenes, one with kaurane skeleton (ent-kaurenoic acid) and other with a pimarane skeleton (ent-pimaradienoic acid). Then, the eighteen compounds were assayed against epimastigote form of Trypanosoma cruzi, with the derivatives showing increase of activity in relation to their precursors. Moreover, the most active derivative presented an IC₅₀ <12.5 µM (estimated 0.8 µM), lower than Benznidazole (IC₅₀ = 9.8 µM), used as control. The esterification of acid diterpenes showed to be an interesting way in the search for anti-trypanosomal agents.