Design, synthesis, and biological activities of aromatic gossypol Schiff base derivatives

Ratiometric Fluorescence Thermometry, Quantitative Gossypol Detection, and CO2 Chemical Fixation by a Multipurpose Europium (III) Metal-Organic Framework

A lanthanide-based molecular crystalline material endows metal-organic frameworks (MOFs) with many fascinating applications such as fluorescence detection and CO2 chemical fixation. Herein, we describe and study a multipurpose europium(III) MOF with the formula of {[Eu2(TATAB)2]·2.5H2O·2DMF}n (Eu-MOF) (where H3TATAB is 4,4',4″-((1,3,5-triazine-2,4,6-triyl)tris(azanediyl))tribenzoic acid ligand) for photoluminescence sensor matrix and CO2 chemical fixation. This Eu-MOF features 1D square channels along the c direction with a pore size of ca.14.07 Å × 14.07 Å, occupied by lattice water and DMF molecules. The obtained Eu-MOF can achieve simultaneous luminescence of the H3TATAB ligand and Eu3+ ions, which can be developed as the sensor matrix for ratiometric fluorescence thermometry. The luminescence of the Eu-MOF demonstrates an obvious color change from red to yellow as temperature rises from 303 to 373 K and the Eu-MOF has a satisfying relative sensitivity of 3.21% K-1 and a small temperature uncertainty of 0.0093 K at 333 K. Moreover, sensitive detection of gossypol was achieved with a quenching constant Ksv of 1.18 × 105 M-1 and a detection limit of 4.61 μM. A combination of the competitive absorption and photoinduced electron transfer caused by host-guest interactions and strengthened π-π packing effect synergistically between gossypol molecules and the Eu-MOF skeleton realizes the "turn-off" sensing of gossypol. Importantly, the nature of the Eu-MOF allows showing CO2 chemical fixation under mild conditions. Thus, the Eu-MOF can be utilized as a multipurpose material for ratiometric fluorescence thermometry, quantitative gossypol detection, and CO2 chemical fixation.

Design and Synthesis of Antifungal Candidates Containing Triazole Scaffold from Natural Rosin against Valsa mali for Crop Protection

Two series of dehydroabietyl-1,2,4-triazole-4-Schiff-based derivatives were synthesized from rosin to control plant fungal diseases. In vitro evaluation and screening of the antifungal activity were performed using Valsa mali, Colletotrichum orbiculare, Fusarium graminearum, Sclerotinia sclerotiorum, and Gaeumannomyces graminis. Compound 3f showed excellent fungicidal activity against V. mali (EC₅₀ = 0.537 μg/mL), which was significantly more effective than the positive control fluconazole (EC₅₀ = 4.707 μg/mL). Compound 3f also had a considerable protective effect against V. mali (61.57%-92.16%), which was slightly lower than that of fluconazole (85.17-100%) at 25-100 μg/mL. Through physiological and biochemical analyses, the preliminary mode of action of compound 3f against V. mali was explored. Ultrastructural observation of mycelia showed that compound 3f hindered the growth of the mycelium and destroyed the ultrastructure of V. mali seriously. Conductivity analysis and laser scanning confocal microscope staining showed that compound 3f changed cell-membrane permeability and caused accumulation of reactive oxygen species. The enzyme activity results showed that compound 3f significantly inhibited the activity of CYP51 (59.70%), SOD (76.9%), and CAT (67.86%). Molecular docking identified strong interaction energy between compound 3f and crystal structures of CYP51 (-11.18 kcal/mol), SOD (-9.25 kcal/mol), and CAT (-8.79 kcal/mol). These results provide guidance for the discovery of natural product-based antifungal pesticide candidates.

Novel palladium(II) and Zinc(II) Schiff base complexes: Synthesis, biophysical studies, and anticancer activity investigation

BACKGROUND

Schiff base metal complexes are considered promising chemotherapeutic agents due to their potential application in cancer therapy.

METHODS

The current work sought to synthesize a brand-new Schiff base ligand obtained from 2-hydroxybenzohydrazide and (E)- 1-(2-(p-tolyl)hydrazono)propan-2-one with metal ions which included Pd(II) and Zn(II) ions. Elemental analyses, FT-IR, mass spectra, 1H NMR, UV-Vis spectrometer, and computational analysis characterized the compound's structure. In vitro, the breast cancer cell line (MCF-7) was tested for its sensitivity to Schiff base (HL) and its Pd(II) and Zn(II) complexes. The half-maximal inhibitory concentration IC₅₀ of the compounds was determined and used to perform the comet assay, which was carried out to reveal the photo-induced DNA damaging ability of the compounds of individual cells. Moreover, the compounds' effects on antioxidant defense systems of enzymes in cells: superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities and oxidant Malondialdehyde (MDA) were examined in MCF-7 cells.

RESULTS

The Pd(II) complex displayed approximately the same IC₅₀ as Cisplatin, while Zn(II) complex had better activity than Cisplatin with very low IC₅₀, 1.40 μg/ml. Significant alterations in SOD, CAT, GPx, and MDA production were discovered, inducing oxidative stress, enlarging ROS production, and reducing the antioxidant amount. This change was approximately similar in most compounds. Consequently, it promoted apoptosis, particularly the Zn(II) complex, which demonstrated an improved impact because of its ability to influence the antioxidant defense systems of enzymes, mostly SOD and GPx, besides increasing MDA levels.

CONCLUSION

It can be concluded that Zn(II) complex is the most effective anticancer drug since it induced a very similar genotoxic effect as Cisplatin and has a very low IC₅₀ value.

Antifungal Activity, Structure-Activity Relationship and Molecular Docking Studies of 1,2,4-Triazole Schiff Base Derivatives

Fourteen novel Schiff base compounds (AS-1∼AS-14) containing 5-amino-1H-1,2,4-triazole-3-carboxylic acid and substituted benzaldehyde were successfully synthesized, and their structures were verified by melting point, elemental analysis (EA) and spectroscopic techniques (Fourier Transform Infra-Red (FT-IR) and Nuclear Magnetic Resonance (NMR)). In vitro hyphal measurements were used to investigate the antifungal activities of the synthesised compounds against Wheat gibberellic, Maize rough dwarf and Glomerella cingulate. The preliminary studies indicated that all compounds had good inhibitory effect on Wheat gibberellic and Maize rough dwarf, among which the compounds of AS-1 (7.44 mg/L, 7.27 mg/L), AS-4 (6.80 mg/L, 9.57 mg/L) and AS-14 (5.33 mg/L, 6.53 mg/L) showed better antifungal activity than that of the standard drug fluconazole (7.66 mg/L, 6.72 mg/L); while inhibitory effect against Glomerella cingulate was poor, only AS-14 (5.67 mg/L) was superior to that of fluconazole (6.27 mg/L). The research of structure-activity relationship exhibited that the introduction of halogen elements on the benzene ring and electron withdrawing groups at the 2,4,5 positions on the benzene ring was beneficial to the improvement of the activity against Wheat gibberellic, while the large steric hindrance was not conducive to the improvement of the activity. Additionally, except for AS-1, AS-3 and AS-10, the other compounds had one or several ratio systems to achieve synergistic effect after recombination with pyrimethamine, among which AS-7 had significant synergistic effect and was expected to be a combinated agent with application prospects. Finally, the molecular docking results of isocitrate lyase with Wheat gibberellic displayed that the presence of hydrogen bonds enabled stable binding of compounds to receptor proteins, and the residues of ARG A: 252, ASN A: 432, CYS A: 215, SER A: 436 and SER A: 434 were the key residues for their binding. Comparing the docking binding energy and biological activity results, it was revealed that the lower the docking binding energy was, the stronger the inhibitory ability of the Wheat gibberellic, when the same position on the benzene ring was substituted.

Computational investigation of phytoalexins as potential antiviral RAP-1 and RAP-2 (Replication Associated Proteins) inhibitor for the management of cucumber mosaic virus (CMV): a molecular modeling, in silico docking and MM-GBSA study

The Replication Associated Proteins (RAP-1 and RAP-2) encoded by CMV ORF 1a and ORF 2a are required for the different stages of the viral replication cycle; being multi-functional, they are good inhibitory targets for anti-CMV compounds. As a new perspective for sustainable crop improvement, we investigated the natural plant-based antimicrobial phytoalexins for their anti-CMV potential. Here, we modeled and predicted the functional domains of RAP-1 and RAP-2, docked with a ligand library comprising 128 phytoalexins reported with broad-spectrum activity, determined their binding energies (BEs), molecular interactions, and inhibition constant (Ki), and compared with the reference plant antiviral compounds ribavirin, ningnanmycin, and benzothiadiazole (BTH). Further, the change in Gibb's free energy of binding (ΔG) and the per residue contribution of the selected top-scored ligand molecules was assessed by the prime MM-GBSA approach. Our results revealed RAP-1 as a discontinuous two-domain and RAP-2 as a multi-domain protein. The compounds glyceollidin (9.8 kcal/mol) and moracin D (7.8 kcal/mol) topped the list for RAP-1 and RAP-2 protein targets respectively and also, the lead molecules had energetically more favorable and comparative ΔG values than the top-scored plant antiviral agent ningnanmycin. The evaluation of in vitro toxicity and agrochemical-like properties showed the least toxicity of these anti-CMV compounds. Taken together, our results provide new insights in understanding the inhibitory effects of phytoalexins towards the RAP proteins and could be employed as new promising anti-CMV candidate compounds for their application in agriculture as biopesticides to combat the CMV disease incidence.Communicated by Ramaswamy H. Sarma.

Gossypol Broadly Inhibits Coronaviruses by Targeting RNA-Dependent RNA Polymerases

Outbreaks of coronaviruses (CoVs), especially severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have posed serious threats to humans and animals, which urgently calls for effective broad-spectrum antivirals. RNA-dependent RNA polymerase (RdRp) plays an essential role in viral RNA synthesis and is an ideal pan-coronaviral therapeutic target. Herein, based on cryo-electron microscopy and biochemical approaches, gossypol (GOS) is identified from 881 natural products to directly block SARS-CoV-2 RdRp, thus inhibiting SARS-CoV-2 replication in both cellular and mouse infection models. GOS also acts as a potent inhibitor against the SARS-CoV-2 variant of concern (VOC) and exerts same inhibitory effects toward mutated RdRps of VOCs as the RdRp of the original SARS-CoV-2. Moreover, that the RdRp inhibitor GOS has broad-spectrum anti-coronavirus activity against alphacoronaviruses (porcine epidemic diarrhea virus and swine acute diarrhea syndrome coronavirus), betacoronaviruses (SARS-CoV-2), gammacoronaviruses (avian infectious bronchitis virus), and deltacoronaviruses (porcine deltacoronavirus) is showed. The findings demonstrate that GOS may serve as a promising lead compound for combating the ongoing COVID-19 pandemic and other coronavirus outbreaks.

Discovery of Novel α-Methylene-γ-Butyrolactone Derivatives Containing Vanillin Moieties as Antiviral and Antifungal Agents

On the basis of the structure of nicotlactone A (L1), a series of novel α-methylene-γ-butyrolactone derivatives B1-B43 were designed and synthesized by structure simplification and active fragment replacement strategies, and their antiviral and antifungal activities were evaluated. The bioassay studies indicated that many target compounds possessed good to excellent antiviral activity against tobacco mosaic virus (TMV) and some of these compounds exhibited specific antifungal activities against Valsa mali and Fusarium graminearum. Compound B32 exhibited the best anti-TMV activity (inactivation effect, 88.9%; protection effect, 65.8%; curative effect, 52.8%) in vivo at 500 mg/L, which is significantly higher than that of commercial virucides ribavirin and ningnanmycin. The inhibition effect of compound B32 was also visualized by the inoculation test using green fluorescent protein (GFP)-labeled TMV. The preliminary antiviral mechanism of compound B32 was investigated. Transmission electron microscopy (TEM) showed that compound B32 could destroy the integrity of virus particles. Then, molecular docking and isothermal titration calorimetry (ITC) analysis further demonstrated that compound B32 exhibited a strong binding affinity to the TMV coat protein with a dissociation constant (K_d) of 3.06 μM, superior to ribavirin. Thus, we deduced that compound B32 may interfere with the self-assembly of TMV particles by binding TMV coat protein (CP). In addition, compound B28 showed good in vitro activity against F. graminearum with an inhibition rate of 90.9% at 50 mg/L, which was greater than that of fluxapyroxad (59.1%) but lower than that of the commercial fungicide carbendazim (96.8%). The present study provides support for the application of these α-methylene-γ-butyrolactone derivatives as novel antiviral and antifungal agents in crop protection.

Coordination Chemistry, Antibacterial Screening, and In Silico ADME Study of Mononuclear NiII and CuII Complexes of Asymmetric Schiff Base of Streptomycin and Aniline

Two novel metal complexes, that is, Ni (StmAn)2(4) and Cu (StmAn)2(5), were synthesized from unsymmetrical Schiff base ligand StmAn (3). The ligand was prepared by refluxing streptomycin (2) and aniline (1). They were characterized by elemental microanalysis, conductivity measurements, and spectroscopic techniques such as 1H NMR, FT-IR, ESI-mass, and electronic absorption spectral study. Interestingly, the study revealed metal coordination through azomethine nitrogen and N-atom of NH-CH3 of N-methyl-L-glucosamine unit of streptomycin. The electronic absorption spectral study supported an octahedral geometry for complex 4 and a tetrahedral geometry for complex 5. Particle size calculation by Scherrer’s formula indicated their nanocrystalline nature. The geometry optimization of the complexes was achieved by running an MM2 job in Gaussian supported Cs-ChemOffice ultra-12.0.1 and ArgusLab 4.0.1 version software. Based on SwissADME predictions, a theoretical drug profile was generated by analyzing absorption, distribution, metabolism, excretion, and toxicity (ADMET) scores of the compounds. They were screened for in vitro antibacterial activity study against four clinical pathogens such as E. coli, S. pneumoniae, P. vulgaris, and S. aureus. Minimum inhibitory concentration (MIC) study demonstrated greater inhibitory potency of complex (4) (0.024 g/L) for S. aureus relative to ligand (3) and complex (5). Studies show that metal complexes are more toxic to bacteria.

Synthesis, spectral studies, antioxidant and antibacterial evaluation of aromatic nitro and halogenated tetradentate Schiff bases

Herein, we report the synthesis, characterization, and biological properties of eleven (3a-3k) novel Schiff bases. The spectral data of FT-IR, ¹H NMR, ¹³C NMR, and LC-MS are associated with these synthesized compounds. From the FT-IR analysis, we confirmed the azomethine (-C=N-) group and from ¹H NMR data, the phenolic –OH proton is appeared at range δ 13.92–14.09ppm due to hydrogen bonding. The LC-MS analysis agreed with molecular ion peaks of synthesized Schiff bases. To evaluate the antibacterial activity of newly synthesized compounds were screened against b. licheniformis, b. species, e. coli, and s. aureus. Furthermore, the antioxidant activity was investigated by two methods 2,2-diphenyl-1-picryl hydrazyl (DPPH) and hydroxyl radical scavenging methods. The (-NO₂,-Cl,-Br,-I) substituted compounds have shown good antibacterial activity against tested organisms. Also, these compounds were exhibited higher antioxidant activity by given methods.

Structure, properties of gossypol and its derivatives-from physiological activities to drug discovery and drug design

Covering up to 2022Gossypol is a polyphenolic compound isolated from cottonseed. There are two optical enantiomers of gossypol, (-)-gossypol and (+)-gossypol. Gossypol exists as three different tautomers, aldehyde, ketone and lactol. Gossypol is toxic and provides a protective mechanism for cotton plants against pests. Gossypol was used as a male contraceptive in China in the 1970s. It was eventually abandoned due to noticeable side effects, disruption of potassium uptake and incomplete reversibility. Gossypol has gained considerable research interest due to its attractive biological activities, especially antitumor and antivirus. Gossypol derivatives are prepared by a structural modification to reduce toxicity and improve their therapeutic effect. This review depicts the bioactivity and regulation mechanisms of gossypol and its derivatives as drug lead compounds, with emphasis on its antitumor mechanism. The design and synthesis of pharmacologically active derivatives based on the structure of gossypol, such as gossypol Schiff bases, apogossypol, gossypolone, are thoroughly discussed. This review aims to serve as a reference for gossypol-based drug discovery and drug design.

Synthesis and Structure–Activity Relationship Studies of Nicot­lactone Analogues as Anti-TMV Agents

The synthesis of the originally proposed structure of (±)-nicotlactone A, a potent antiviral lignan with three continuous chiral centers, is reported in 5 steps from methyl acrylate. The key steps of the synthesis included an In-catalyzed regioselective allylation and a Mn-catalyzed Mukaiyama hydration reaction. Our synthetic strategy also enabled us to get the other three epimers and investigate the structure–activity relationship. The NMR data of the synthesized compounds do not match that of the isolated sample, indicating that the structure of nicotlactone A remains to be reassigned. All the synthetic target compounds were evaluated for their anti-tobacco mosaic virus (anti-TMV) activity. Bioassay results indicated that (±)-8-demethylnicotlactone A displayed similar anti-TMV activity to the commercial agent ningnanmycin, thus being a promising candidate or lead compound for developing novel antiviral agents in crop protection.

A turn-on NIR fluorescence sensor for gossypol based on Yb-based metal-organic framework

The development of analytical method for selective and sensitive detection of gossypol (Gsp), an extraction from the cotton plants, is important but still challenging in food safety and medical field. Herein, we reported a turn-on near infrared (NIR) fluorescence detection strategy for Gsp based on a metal-organic framework (MOF), QBA-Yb, which was prepared from 4,4'-(quinolone-5, 8-diyl) benzoate with Yb(NO₃)₃·5H₂O by solvothermal synthesis. The Gsp acted as another "antenna" to sensitize the luminescence of Yb³⁺, leading to the turn-on NIR emission upon 467 nm excitation. As Gsp concentration increased, the NIR emission at 973 nm enhanced gradually, thus enabling highly sensitive Gsp detection in a turn-on way. The experiment and theoretical calculation results revealed the presence of strong hydrogen bonds between Gsp molecules and the MOF skeleton. The developed QBA-Yb probe showed excellent characteristics for detection of Gsp molecules, accompanied by wide linear range (5-160 μg/mL), low detection limit (0.65 μg/mL) and short response time (within 10 min). We have further demonstrated that the QBA-Yb probe was successfully applied for the determination of Gsp in real samples of cottonseeds.

Design, Synthesis, and Bioactivities of Phthalide and Coumarin Derivatives Based on the Biosynthesis and Structure Simplification of Gossypol

Because gossypol and hemigossypol show antiviral activity but are structurally complex, we designed and synthesized a series of structurally simpler phthalide and coumarin derivatives. The phthalide derivatives were synthesized by opening the naphthalene ring of hemigossypol, and the coumarin derivatives were synthesized by ring-opening reactions of the phthalide derivatives with the goal of investigating the effect of the lactone ring size on bioactivity. The bioassay results showed that the two series of target compounds possessed moderate to good activities against tobacco mosaic virus, One of the compounds showed in vivo inactivation, curative, and protection activities of 50 ± 1, 53 ± 3, and 48 ± 2% at 500 mg/L, values which are higher than those of gossypol (32 ± 1, 35 ± 1, 29 ± 1%, respectively) and comparable to those of hemigossypol (55 ± 1, 49 ± 1, and 48 ± 1%, respectively) and the commercial antiviral agent ningnanmycin (56 ± 2, 54 ± 1, 58 ± 1%) at the same dose. Thus, this compound is a promising candidate for the development of new anti-plant-virus agents. In addition, most of the synthesized compounds showed broad-spectrum activity when tested against 14 kinds of phytopathogenic fungi and showed selectivity against Sclerotinia sclerotiorum, Physalospora piricola, and Rhizoctonia cerealis. Moreover, some of the compounds exhibited activity against Plutella xylostella larvae; the two most active compounds exhibited larvicidal activities (LC₅₀) of 4.10 and 5.47 mg/L, respectively. Further studies showed that these compounds also exhibited insecticidal activities against Mythimna separata, Helicoverpa armigera, and Pyrausta nubilalis larvae.

Preparation and Anti-Tobacco Mosaic Virus Activities of Crocetin Diesters

The development of antiviral agents with an original structure and noticeable effect is always in great need. Natural products are important lead compounds in the development of new pesticides. Crocin-1 and crocin-2 were effectively isolated from Gardeniae fructus and found to have higher anti-tobacco mosaic virus (TMV) activity levels than ribavirin. A series of the crocetin diester derivatives were synthesized with separated crocetin-1 as material and evaluated for their anti-TMV activities. They could be dissolved in common organic solvents as dichloromethane, ethyl acetate, tetrahydrofuran, and methanol. Compounds 5, 9, 13, 14, and 15 displayed higher activities in vivo than ribavirin. Compound 14 with significantly higher antiviral activities than lead compounds (crocin-1 and crocin-2) emerged as a new antiviral candidate.

Spectral, Molecular Modeling, and Biological Activity Studies on New Schiff's Base of Acenaphthaquinone Transition Metal Complexes

The newly synthesized Schiff's base derivative, N-allyl-2-(2-oxoacenaphthylen-1(2H)-ylidene)hydrazine-1-carbothioamide, has been characterized by different spectral techniques. Its reaction with Co(II), Ni(II), and Zn(II) acetate led to the formation of 1 : 1 (M:L) complexes. The IR and NMR spectral data revealed keto-thione form for the free ligand. On chelation with Co(II) and Ni(II), it behaved as mononegative and neutral tridentate via O, N¹, and S donors, respectively, while it showed neutral bidentate mode via O and N¹ atoms with Zn(II). The electronic spectra indicated that all the isolated complexes have an octahedral structure. The thermal gravimetric analyses confirmed the suggested formula and the presence of coordinated water molecules. The XRD pattern of the metal complexes showed that both Co(II) and Ni(II) have amorphous nature, while Zn(II) complex has monoclinic crystallinity with an average size of 9.10 nm. DFT modeling of the ligand and complexes supported the proposed structures. The calculated HOMO-LUMO energy gap, ΔE_H-L, of the ligand complexes was 1.96–2.49 eV range where HAAT < Zn(II) < Ni(II) < Co(II). The antioxidant activity investigation showed that the ligand and Zn(II) complex have high activity than other complexes, 88.5 and 88.6%, respectively. Accordingly, the antitumor activity of isolated compounds was examined against the hepatocellular carcinoma cell line (HepG2), where both HAAT and Zn(II) complex exhibited very strong activity, IC₅₀ 6.45 ± 0.25 and 6.39 ± 0.18 μM, respectively.

Synthesis and Anti-Tobacco Mosaic Virus/Fungicidal/Insecticidal/Antitumor Bioactivities of Natural Product Hemigossypol and Its Derivatives

To further study the structure-activity relationship of gossypol, hemigossypol (1) and its derivatives (2-23) were successfully designed via structure simplification and chemically synthesized. The anti-tobacco mosaic virus (TMV), fungicidal, and insecticidal activities of them were tested systematically. Most of these derivatives exhibited excellent anti-TMV activity. Furthermore, these compounds also exhibited broad-spectrum fungicidal activities against 14 kinds of phytopathogenic fungi. In particular, hemigossypol acid lactone (7) was stable in the air. In terms of biological activity, it not only showed anti-TMV activity (inhibitory rates of 70.3, 65.4 and 72.4% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively) comparable to ningnanmycin but also exhibited higher insecticidal activity against mosquito larvae (60%/0.25 mg/kg) than the commercial species rotenone. None of hemigossypol and the tested derivatives showed antitumor activities.

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.

Ternary hydrogels with tunable mechanical and self-healing properties based on the synergistic effects of multiple dynamic bonds

Ternary hydrogels with tunable mechanical properties were prepared based on the synergistic effects of hydrogen bonds and imine bonds.

Mn(II) complex of a vitamin B6 Schiff base as an exclusive apoptosis inducer in human MCF7 and HepG2 cancer cells: Synthesis, characterization, and biological studies

Herein, a Mn(II) complex of the N,N'-dipyridoxyl(1,4-butanediamine) (═H₂ L) Schiff base has been newly synthesized. The synthesized complex was characterized by several experimental methods. In addition, the density functional theory approaches were used for theoretical identification of the complex. A good agreement between the computed and experimental infrared frequencies demonstrates validity of the optimized geometry for the synthesized complex. In a N₂ O₂ manner, two azomethine nitrogens and two phenolate oxygens of the L^2- ligand are coordinated to the Mn²⁺ metal ion. The biological studies indicate an efficient apoptotic and antioxidant activities of the synthesized [MnL(CH₃ OH)₂ ] complex on both of the HepG2 and MCF7 cancer cells. Since it has been suggested that the complex is an exclusive potent antitumor for treatment of the human breast and liver cancers.

Synthesis, characterization, and supramolecular architectures of two distinct classes of probes for the visualization of endogenously generated hypochlorite ions in response to cellular activity

Two distinct classes of compounds, (E)-2-(((3-amino-4-nitrophenyl) imino) methyl)-5-(diethylamino) phenol (SB) and 5-(diethylamino)-2-(5-nitro-1H-benzo[d]imidazol-2-yl) phenol (IM) were synthesized. SB, a bright red colored compound was crystallized in acetonitrile as a triclinic crystal system while IM, yellow colored compound crystallized as a monoclinic crystal system in dimethylformamide by vapor diffusion of diethylether. These compounds were characterized using spectroscopic techniques (IR, UV-visible, ¹H, and ¹³C NMR), and X-ray crystallography. SB and IM displayed classical and non-classical H-bonding involving C-H…O and π…π interactions. These compounds detected hypochlorite ions in aqueous DMSO (1: 9, v/v, HEPES buffer, pH 7.4), and detection was visible via color changes by naked eye. We also performed UV-visible and fluorescence titrations, showing detection limits of 8.82 × 10^-7 M for SB and 2.44 × 10^-7 M for IM. The fluorometric responses from SB and IM were also studied against different ROS and anions. DFT calculations were performed to strengthen the proposed sensing mechanisms of both SB and IM. Hypochlorite, which is endogenously generated by myeloperoxidase in endosomes, was specifically visualized using SB and IM in lipopolysaccharide-treated RAW264.7 cells. These probes were also used to image the generation of hypochlorite by RAW264.7 cells during phagocytosis of non-fluorescent polystyrene beads.

Highly Enantioselective Semisynthesis of (+)/(-)-Gossypol Schiff Base Derivatives from Ground Plant Material

We have recently developed a one-pot process for simultaneous extraction and chemical modification (SECheM) on Cienfuegosia digitata, a Mauritanian Malvaceae called locally "Izide". On the basis of this innovative methodology that consisted of using ground plant roots as starting material in gossypol Schiff base semisynthesis, we now report how this concept can be used to access enantiomerically pure Schiff base atropisomer derivatives of gossypol in only two steps. This study has been envisioned since enantiomerically pure Schiff base atropisomer derivatives of gossypol are generally more potent biologically when compared to racemic gossypol Schiff bases.

Natural Product Gossypol and its Derivatives in Precision Cancer Medicine

Gossypol, a natural product extracted from the seed, roots, and stem of cotton, was initially used as a male contraceptive but was subsequently investigated as a novel antitumor agent. This review depicts the current status of gossypol and its derivatives as novel antitumor agents as well as presents their preparation and characteristics, especially of some gossypol Schiff bases, through quantitative and structural analysis. The main attractive target sites of gossypol and its derivatives are Bcl-2 family proteins containing the anti-apoptosis proteins Bcl-2 and Bcl-XL. The molecular mechanism of gossypol analogs not only involves cell apoptosis but also autophagy, cell cycle arrest, and other abnormal cellular phenomena. Gossypol and its derivatives exert antitumor effects on different cancer types in vitro and in vivo, and demonstrate synergistic effects with other chemo- and radio- therapeutic treatments. In addition, several nanocarriers have been designed to load gossypol or its derivatives in order to expand the range of their applications and evaluate their combination effects with other anti-tumor agents. This review may serve as a reference for the rational application of gossypol analogs as anti-tumor agents.

Spectroscopic and molecular docking studies on interaction of two Schiff base complexes with bovine serum albumin

This study was designed to examine interaction of two ternary copper (II) Schiff base complexes with bovine serum albumin (BSA), using spectroscopic and molecular docking techniques. The fluorescence quenching measurements revealed that the quenching mechanism was static and the binding site of both Schiff bases to BSA was singular. Förster energy transfer measurements, synchronous fluorescence spectroscopy, and docking study showed both Schiff bases bind to the Trp residues of BSA in short distances. Docking study showed that both Schiff base molecules bind with BSA by forming several hydrogen and van der Waals bonds. In addition, molecular docking study indicated that Schiff base A and Schiff base B were located within the binding pocket of subdomain IB and subdomain IIA of BSA, respectively. Results of Fourier transform-infrared spectroscopy demonstrated that bovine serum albumin interacts with both Schiff bases and the secondary structure of BSA was changed.Communicated by Ramaswamy H. Sarma.

Leveraging botanical resources for crop protection: the isolation, bioactivity and structure-activity relationships of lycoris alkaloids

BACKGROUND

Lycoris aurea (L' Herit.) Herb (Amaryllidaceae) is a native pesticide in China. The ethanolic extract of Lycoris aureate bulbs, the total alkaloids of L. aurea bulbs and the main alkaloids of L. aurea bulbs were systematically investigated as part of a novel project to study their antiviral, fungicidal (phytopathogenic) and insecticidal activities. We also prepared 18 lycorine derivatives and evaluated their bioactivities.

RESULTS

Lycorine had excellent larvicidal activity against Plutella xylostella (LC₅₀ = 10.6 mg L^-1 ) and was also effective during a field trial. It also showed good inhibitory activity against tobacco mosaic virus (TMV) and good fungicidal activity against Phytophthora capsici (EC₅₀ = 7.76 mg L^-1 ). Compounds 13 and 15 exhibited good anti-TMV activity, excellent fungicidal activity against Rhizoctonia cerealis (EC₅₀ = 6.78 mg L^-1 ) and excellent larvicidal activity against Culex pipiens pallens (LC₅₀ at 0.1-0.25 mg L^-1 ).

CONCLUSION

Lycorine was identified as the main active component of L. aurea bulbs and showed potential for field application against P. xylostella. The activities of compounds 13 and 15 make them excellent candidates for new lead compounds in novel pesticide research. This study provides the basis for developing these alkaloids into potential agrochemicals. © 2018 Society of Chemical Industry.

Preparation and functional analysis of gossypols having two carbohydrate appendages with enaminooxy linkages

We developed new gossypol (Gos)-based glycoconjugates through dehydration condensation of native Gos and chemically modified glycosides having aminooxy groups. The resultant glycoconjugates (glycoGos) were resistant to hydrolysis, although they were light-sensitive and slowly decomposed even under indoor lighting. The glycoGos also exhibited improved water solubility compared with native Gos, but their saturated concentrations in water were still low (6.4-17 μM), due to their hydrophobic naphthyl rings. We also carried out WST-8 assays to assess the anticancer activity of the glycoGos on DLD-1 and HepG2 cells and found that the glycoGos having β-lactosides and having β-galactosides (specific ligands for asialoglycoprotein receptors) showed enhanced anticancer activity on HepG2 cells.

Discovery of Glycosylated Genipin Derivatives as Novel Antiviral, Insecticidal, and Fungicidal Agents

A series of novel genipin glycoside derivatives incorporating 11 glycosidic moieties at either the 1 or 10 position of genipin were designed and synthesized. These compounds exhibited moderate to excellent inhibitory activities against tobacco mosaic virus. Especially, the in vitro and in vivo activities of compounds 6e, 7c, 7d, 7f, 7h, and 7i were comparable to that of ribavirin. In particular, compound 7c, the mannosyl derivative of genipin at the 10 position, showed the best activity. The series of genipin glycosyl derivatives also displayed fungicidal activities against 14 kinds of phytopathogenic fungi, especially for Rhizoctonia cerealis and Sclerotinia sclerotiorum. Moreover, compound 6h exhibited good insecticidal activity against diamondback moth; compounds 7b, 7c, and 7g exhibited moderate insecticidal activity against three kinds of Lepidoptera pests (oriental armyworm, cotton bollworm, and corn borer); and compound 7e showed excellent larvacidal activities against mosquito.

Study of the structure–bioactivity relationship of three new pyridine Schiff bases: synthesis, spectral characterization, DFT calculations and biological assays

Schiff bases exhibit a broad range of applications, including their use as catalysts, stabilizers, dyes, and intermediates in organic synthesis; and biological activities, such as antifungal properties.

Development of SECheM Concept for Isolation and Chemical Modification of Gossypol Directly from Cienfuegosia digitata

INTRODUCTION

Gossypol is an axially chiral natural polyphenol classically extracted from the Malavaceae family. Nevertheless, its extraction and isolation from a plant can be quite complicated and extremely time-consuming since gossypol is known to be sensitive to degradation under solvents, high temperature and light action. Moreover, its purification over column chromatography is a challenging problem due to its ability to oxidise and the existence of various tautomer forms.

OBJECTIVE

To develop an efficient "one-step" strategy for simultaneous extraction and semi-synthesis by short-circuiting critical gossypol isolation and purification steps.

METHODOLOGY

Gossypol was first isolated from Cienfuegosia digitata roots, characterised (by 1D and 2D NMR) and quantified (by UV spectrophotometry). Thus, aniline was selected to test the "one-step" in situ trapping of freshly extracted gossypol leading to a Schiff base analogue. After screening solvents and extraction times on this model reaction, the "SECheM" (simultaneous extraction and chemical modification) concept was successfully extended to other amines, underlining the efficiency and the robustness of the strategy.

RESULTS

After having shown that gossypol occurred as a major compound in C. digitata roots, different experimental procedures using Soxhlet extraction in the presence of aniline pointed out the best conditions for the SECheM concept (7 h of reaction and extraction time in ether as solvent). Ultimately, the concept has been generalised to 17 other amines.

CONCLUSION

This is a report of the first semi-synthesis that allows: (1) "in situ" preparation of more stable gossypol Schiff base derivatives directly from ground plant material and (2) circumvention of gossypol extraction and purification problems. Copyright © 2017 John Wiley & Sons, Ltd.

Recent advances in gossypol derivatives and analogs: a chemistry and biology view

Gossypol as a natural occurring polyphenol has been studied in a wide range of therapeutic contexts for a long time. The chemical modifications on gossypol were limited due to the unique chemical properties of polyphenols. The design and synthesis of gossypol derivatives and the exploration of their biological activities are the interest of the synthetic chemists, medicinal chemists and pharmacologists. Thus, the progress of diverse gossypol derivatives and analogs' synthesis, biological activities, mechanism elucidation and drug discovery based on gossypol scaffold is summarized.

Antiviral activity and mechanism of gossypols: effects of the O2˙− production rate and the chirality

(−)-Gossypol displayed an obviously higher antiviral activity against the tobacco mosaic virus (TMV) than (+)-gossypol, whereas the anti-TMV activity of (−)-gossypol Schiff bases is not significantly higher than (+)-gossypol Schiff bases.

Synthesis and Biological Evaluation of New (−)-Gossypol-Derived Schiff Bases and Hydrazones

A series of 14 new (-)-gossypol Schiff bases and hydrazones have been synthesized via an in situ procedure in high yields. Structural data showed that all target compounds exist as the enamine tautomer. Bioassays showed that several compounds exhibited cytotoxic effects against three human cancer cell lines. Compound 8a showed the greatest cytotoxic effect against hepatocellular carcinoma (HepG2), lung carcinoma (LU-1), and breast cancer (MCF-7) cell lines with IC50 values of 20.93, 13.58, and 9.40 μM, respectively. However, in an antibacterial test, compounds 8a and 8b inhibited Staphylococcus aureus and Bacillus cereus and compound 8e inhibited only Staphylococcus aureus at the same MIC values of 1024 μg/ml.

Synthesis, structure and antimicrobial evaluation of a new gossypol triazole conjugates functionalized with aliphatic chains and benzyloxy groups

Synthetic limitations in the copper-catalyzed azide alkyne cycloaddition (CuAAC) on gossypol's skeleton functionalized with alkyne (2) or azide (3) groups have been indicated. Modified approach to the synthesis of new gossypol-triazole conjugates yielded new compounds (24-31) being potential fungicides. Spectroscopic studies of triazole conjugates 24-31 have revealed their structures in solution, i.e., the presence of enamine-enamine tautomeric forms and π-π stacking intramolecular interactions between triazole arms. Biological evaluation of the new gossypol-triazole conjugates revealed the potency of 30 and 31 derivatives, having triazole-benzyloxy moieties, comparable with that of miconazole against Fusarium oxysporum. The results of HPLC evaluation of ergosterol content in different fungi strains upon treatment of gossypol and its derivatives enabled to propose a mechanism of antifungal activity of these compounds.