Discovery of Natural Sesquiterpene Lactone 1-O-Acetylbritannilactone Analogues Bearing Oxadiazole, Triazole, or Imidazole Scaffolds for the Development of New Fungicidal Candidates

In recent decades, natural products have been considered important resources for developing of new agrochemicals because of their novel architectures and multibioactivities. Consequently, herein, 1-O-acetylbritannilactone (ABL), a natural sesquiterpene lactone from Inula britannica L., was used as a lead for further modification to discover fungicidal candidates. Six series of ABL-based derivatives containing an oxadiazole, triazole, or imidazole moiety were designed and synthesized, and their antifungal activities were also evaluated in vitro and in vivo. Bioassay results revealed that compounds 8d, 8h, and 8j (EC₅₀ = 61.4, 30.9, and 12.4 μg/mL, respectively) exhibited more pronounced inhibitory activity against Fusarium oxysporum than their precursor ABL (EC₅₀ > 500 μg/mL) and positive control hymexazol (EC₅₀ = 77.2 μg/mL). Derivatives 8d and 11j (EC₅₀ = 19.6 and 41.5 μg/mL, respectively) exhibited more potent antifungal activity toward Cytospora mandshurica than ABL (EC₅₀ = 68.3 μg/mL). Compound 10 exhibited excellent and broad-spectrum antifungal activity against seven phytopathogenic fungal mycelia. Particularly, the inhibitory activity of compound 10 against the mycelium of Botrytis cinerea was more than 10.8- and 2.3-fold those of ABL and hymexazol, respectively. Meanwhile, derivative 10 (IC₅₀ = 47.7 μg/mL) displayed more pronounced inhibitory activity against the spore of B. cinerea than ABL (IC₅₀ > 500 μg/mL) and difenoconazole (IC₅₀ = 80.8 μg/mL). Additionally, the in vivo control efficacy of compound 10 against B. cinerea was further studied using infected tomatoes (protective effect = 58.4%; therapeutic effect = 48.7%). The preliminary structure-activity relationship analysis suggested that the introduction of the 1,3,4-oxadiazole moiety (especially the 1,3,4-oxadiazole heterocycle containing the 4-chlorophenyl, 2-furyl, or 2-pyridinyl group) on the skeleton of ABL was more likely to produce potential antifungal compounds. These findings pave the way for further design and development of ABL-based derivatives as potential antifungal agents.

Natural Sesquiterpene Lactone as Source of Discovery of Novel Fungicidal Candidates: Structural Modification and Antifungal Activity Evaluation of Xanthatin Derived from Xanthium strumarium L

As part of our ongoing efforts to discover novel agricultural fungicidal candidates from natural sesquiterpene lactones, in the present work, sixty-three xanthatin-based derivatives containing a arylpyrazole, arylimine, thio-acylamino, oxime, oxime ether, or oxime ester moiety were synthesized. Their structures were well characterized by ¹H and ¹³C nuclear magnetic resonance and high-resolution mass spectrometry, while the absolute configurations of compounds 5' and 6a were further determined by single-crystal X-ray diffraction. Meanwhile, the antifungal activities of the prepared compounds against several phytopathogenic fungi were investigated using the spore germination method and the mycelium growth rate method in vitro. The bioassay results illustrated that compounds 5, 5', and 15 exhibited excellent inhibitory activity against the tested fungal spores and displayed remarkable inhibitory effects on fungal mycelia. Compounds 5 and 5' exhibited more potent inhibitory activity (IC₅₀ = 1.1 and 24.8 μg/mL, respectively) against the spore of Botrytis cinerea than their precursor xanthatin (IC₅₀ = 37.6 μg/mL), wherein the antifungal activity of compound 5 was 34-fold higher than that of xanthatin and 71-fold higher than that of the positive control, difenoconazole (IC₅₀ = 78.5 μg/mL). Notably, compound 6'a also demonstrated broad-spectrum inhibitory activity against the four tested fungal spores. Meanwhile, compounds 2, 5, 8, and 15 showed prominent inhibitory activity against the mycelia of Cytospora mandshurica with the EC₅₀ values of 2.3, 11.7, 11.1, and 3.0 μg/mL, respectively, whereas the EC₅₀ value of xanthatin was 14.8 μg/mL. Additionally, compounds 5' and 15 exhibited good in vivo therapeutic and protective effects against B. cinerea with values of 55.4 and 62.8%, respectively. The preliminary structure-activity relationship analysis revealed that the introduction of oxime, oxime ether, or oxime ester structural fragment at the C-4 position of xanthatin or the introduction of a chlorine atom at the C-3 position of xanthatin might be significantly beneficial to antifungal activity. In conclusion, the comprehensive investigation indicated that partial xanthatin-based derivatives from this study could be considered for further exploration as potential lead structures toward developing novel fungicidal candidates for crop protection.

Structural Modification and Biological Activity of Polysaccharides

Natural polysaccharides are macromolecular substances with a wide range of biological activities. The structural modification of polysaccharides by chemical means can enhance their biological activity. This paper reviews the latest research reports on the chemical modification of natural polysaccharides. At present, the modification methods of polysaccharides mainly include sulfation, phosphorylation, carboxymethylation, socialization, methylation and acetylation. The chemical and physical structures of the modified polysaccharides were detected via ultraviolet spectroscopy, FT-IR, high-performance liquid chromatography, ultraviolet spectroscopy, gas chromatography-mass spectrometry, nuclear magnetic resonance and scanning electron microscopy. Modern pharmacological studies have shown that the modified polysaccharide has various biological activities, such as antioxidant, antitumor, immune regulation, antiviral, antibacterial and anticoagulant functions in vitro. This review provides fresh ideas for the research and application of polysaccharide structure modification.

Discovery of [5,5'-bibenzo[d][1,3]dioxol]-6-substituted amine derivatives as potent proprotein convertase subtilisin/kexin type 9 inhibitors

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a promising therapeutic target for the treatment of hyperlipidemia. In discovery of novel small molecules that interfere PCSK9/LDLR protein-protein interaction (PPI), structural modification was performed based on our previously derived compounds. A series of [5,5'-bibenzo[d][1,3]dioxol]-6-amine analogs were designed and synthesized for the activity evaluation. In the PCSK9/LDLR PPI impairing test, molecules D28 and D29, exhibited remarkable inhibitory potency with IC50 values of 8.30 and 6.70 μM compared with SBC-115337 (17.89 μM), respectively. Molecular docking predicted the binding pattern of compounds D28 and D29 in the LDLR binding site of PCSK9. Hydrophobic interactions play an important role in the binding of aromatic molecular fragments to the pockets in the PCSK9/LDLR binding interface. Further LDLR expression and LDL uptake studies revealed that both D28 and D29 restored LDLR expression on the surface of hepatic HepG2 cells and improved extracellular LDL uptake in the presence of PCSK9. It is significant that molecules D28 and D29 exhibited potential for the treatment of hyperlipidemia in current in vitro investigations. Generally, lead compounds with novel structures were developed in the present study for further design of lipid-lowering molecules by targeting PCSK9/LDLR PPI.

Structural Modification Endows Small-Molecular SN38 Derivatives with Multifaceted Functions

As a camptothecin derivative, 7-ethyl-10-hydroxycamptothecin (SN38) combats cancer by inhibiting topoisomerase I. SN38 is one of the most active compounds among camptothecin derivatives. In addition, SN38 is also a theranostic reagent due to its intrinsic fluorescence. However, the poor water solubility, high systemic toxicity and limited action against drug resistance and metastasis of tumor cells of SN38 indicates that there is great space for the structural modification of SN38. From the perspective of chemical modification, this paper summarizes the progress of SN38 in improving solubility, increasing activity, reducing toxicity and possessing multifunction and analyzes the strategies of structure modification to provide a reference for drug development based on SN38.

Synthesis of Methylgenipin and Evaluation of Its Anti-Hepatic Injury Activity

Genipin has been the focus of research as a multifunctional compound for the treatment of pathogenic diseases. However, hepatotoxicity caused by oral genipin raises concerns about its safety. To obtain novel derivatives with low toxicity and efficacy, we synthesized methylgenipin (MG), a new compound, using structural modification, and investigated the safety of MG administration. The results showed that the LD₅₀ of oral MG was higher than 1000 mg/kg, no mice died or were poisoned during the experiment in the treatment group, and there was no significant difference in biochemical parameters and liver pathological sections compared with the control. Importantly, MG (100 mg/kg/d) treatment for 7 days reduced alpha-naphthylisothiocyanate (ANIT)-induced increases in liver index, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), and total bilirubin (TBIL) levels. Histopathology demonstrated that MG could treat ANIT-induced cholestasis. In addition, using proteomics to investigate the molecular mechanism of MG in the treatment of a liver injury may be related to enhancing antioxidant function. Kit validation showed that ANIT induced an increase in malondialdehyde (MDA) and a decrease in superoxide dismutase (SOD) and glutathione (GSH) levels, while the MG pretreatments, both of which were significantly reversed to some extent, suggested that MG may alleviate ANIT-induced hepatotoxicity by enhancing endogenous antioxidant enzymes and inhibiting oxidative stress injury. In this study, we demonstrate that the treatment of mice with MG does not cause impaired liver function and provide an investigation of the efficacy of MG against ANIT-induced hepatotoxicity, laying the foundation for the safety evaluation and clinical application of MG.

[Microbial transformation of artemisinin and its derivatives]

Microbial transformation is an efficient enzymatic approach for the structural modification of exogenous compounds to obtain derivatives. Compared with traditional chemical synthesis, the microbial transformation has in fact the undoubtable advantages of strong region-and stereo-selectivity, and a low environmental and economic impact on the production process, which can achieve the reactions challenging to chemical synthesis. Because microbes are equipped with a broad-spectrum of enzymes and therefore can metabolize various substrates, they are not only a significant route for obtaining novel active derivatives, but also an effective tool for mimicking mammal metabolism in vitro. Artemisinin, a sesquiterpene with a peroxy-bridged structure serving as the main active functional group, is a famous antimalarial agent discovered from Artemisia annua L. Some sesquiterpenoids, such as dihydroartemisinin, artemether, and arteether, have been developed on the basis of artemisinin, which have been successfully marketed and become the first-line antimalarial drugs recommended by WHO. As revealed by pharmacological studies, artemisinin and its derivatives have exhibited extensive biological activities, including antimalarial, antitumor, antiviral, anti-inflammatory, and immunomodulatory. As an efficient approach for structural modification, microbial transformation of artemisinin and its derivatives is an increasingly popular strategy that attracts considerable attention recently, and numerous novel derivatives have been discovered. Herein, this paper reviewed the microbial transformation of artemisinin and its artemisinin, including microbial strains, culture conditions, product isolation and yield, and biological activities, and summarized the advances in microbial transformation in obtaining active derivatives of artemisinin and the simulation of in vivo metabolism of drugs.

Semisynthesis, Biological Evaluation and Molecular Docking Studies of Barbatic Acid Derivatives as Novel Diuretic Candidates

Barbatic acid, a compound isolated from lichen, has demonstrated a variety of biological activities. In this study, a series of esters based on barbatic acid (6a-q') were designed, synthesized, and evaluated for their diuretic and litholytic activity at a concentration of 100 μmol/L in vitro. All target compounds were characterized using ¹H NMR, ¹³C NMR, and HRMS, and the spatial structure of compound 6w was confirmed using X-ray crystallography. The biological results showed that some derivatives, including 6c, 6b', and 6f', exhibited potent diuretic activity, and 6j and 6m displayed promising litholytic activity. Molecular docking studies further suggested that 6b' had an optimal binding affinity to WNK1 kinases related to diuresis, while 6j could bind to the bicarbonate transporter CaSR through a variety of forces. These findings indicate that some barbatic acid derivatives could be further developed into novel diuretic agents.

Synthesis and Evaluation of Piperazine-Tethered Derivatives of Alepterolic Acid as Anticancer Agents

Alepterolic acid is a natural diterpenoid isolated from Aleuritopteris argentea with potential anti-cancer activity. In this study, alepterolic acid was modified to construct a series of arylformyl piperazinyl derivatives (3a-3p). The synthesized derivatives were fully characterized with HRMS, NMR, and IR. Four compounds with inhibition rate higher than 30 % at 10 μM (3f, 3n, 3g and 3k) were further measured to obtain the IC50 values against four cancer cell lines, including hepatoma cell lines HepG2, lung cancer cell lines A549, estrogen receptor-positive cell lines MCF7, and triple-negative breast cancer (TNBC) cell lines MDA-MB-231 by MTT assay. It was found that these compounds were more effective to HepG2 and MDA-MB-231 cells, while less toxic to A549 and MCF7 cells, and compound 3n as the most toxic derivatve against MDA-MB-231 cell lines, with IC50 value of 5.55±0.56 μM. Trypan blue staining and colony formation assay showed that compound 3n inhibited the growth of MDA-MB-231 cells and prevented colony formation. Hoechst staining, flow cytometry and western blot analysis revealed that compound 3n induced caspase-dependent apoptosis in MDA-MB-231 cells. Conclusively, compound 3n was demonstrated to be a potential anti-cancer lead compound for further investigation.

Mechanism and Kinetics of Prothioconazole Photodegradation in Aqueous Solution

This study investigated the effects of light source, pH value, and NO₃^- concentration on the photodegradation of prothioconazole in aqueous solution. The half-life (t_1/2) of prothioconazole was 173.29, 21.66, and 11.18 min under xenon, ultraviolet, and high-pressure mercury lamps, respectively. At pH values of 4.0, 7.0, and 9.0 under a xenon lamp light source, the t_1/2 values were 693.15, 231.05, and 99.02 min, respectively. Inorganic substance NO₃^- clearly promoted the photodegradation of prothioconazole, with t_1/2 values of 115.53, 77.02, and 69.32 min at NO₃^- concentrations of 1.0, 2.0, and 5.0 mg L^-1, respectively. The photodegradation products were identified as C₁₄H₁₅Cl₂N₃O, C₁₄H₁₆ClN₃OS, C₁₄H₁₅Cl₂N₃O₂S, and C₁₄H₁₃Cl₂N₃ based on calculations and the Waters compound library. Furthermore, density functional theory (DFT) calculations showed that the C-S, C-Cl, C-N, and C-O bonds of prothioconazole were the reaction sites with high absolute charge values and greater bond lengths. Finally, the photodegradation pathway of prothioconazole was concluded, and the variation in energy of the photodegradation process was attributed to the decrease in activation energy caused by light excitation. This work provides new insight into the structural modification and photochemical stability improvement of prothioconazole, which plays an important role in decreasing safety risk during application that will reduce the exposure risk in field environment.

Design, synthesis and anti-tumor activity of asiatic acid derivatives as VEGF inhibitors

The VEGF receptor is mock-coupled with a known active compound and the active groups of the inhibitor which can bind to VEGF were analyzed. Using asiatic acid as a lead compound, 10 novel skeleton candidate compounds were designed through introduction of the active groups onto the special location and synthesized simultaneously. Furthermore, the structure of these compounds was determined by ¹H NMR, ¹³C NMR and MS and 9 compounds were identified as the new compounds. Moreover, the in vitro anti-tumor activities of these new compounds were determined by MTT assay on two cancer cell lines (HepG2 and SGC-7901). The results showed that compounds I₁ and II₂ have more potent anticancer activity than positive control drugs such as gefitinib and paclitaxel.

Natural products in crop protection: thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles as antifungal agents and their mechanism of action

BACKGROUND

Phytopathogenic fungi can cause a direct loss in economic value of agriculture. Especially Valsa mali Miyabe et Yamada, a devastating phytopathogenic disease especially threatening global apple production, is very difficult to control and manage. To discover new potential antifungal agents, a series of thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles were prepared. Their antifungal activities were first tested against six typically phytopathogenic fungi including Curvularia lunata, Valsa mali, Alternaria alternate, Fusarium graminearum, Botrytis cinerea and Fusarium solani. Then their mechanism of action against V. mali was investigated.

RESULTS

Derivatives displayed potent antifungal activity against V. mali. Notably, 3-acetyl-N-benzylindole thiosemicarbazone (IV-1: EC₅₀ : 0.59 μg mL^-1 ), whose activity was comparable to that of a commercial fungicide carbendazim (EC₅₀ : 0.33 μg mL^-1 ), showed greater than 98-fold antifungal activity of the precursor indole. Moreover, compound IV-1 displayed good protective and therapeutic effects on apple Valsa canker disease. By scanning electron microscope (SEM) and RNA-Seq analysis, it was demonstrated that compound IV-1 can destroy the hyphal structure and regulate the homeostasis of metabolism of V. mali via the ergosterol biosynthesis and autophagy pathways.

CONCLUSION

3-Acetyl-N-(un)substituted benzylindoles thiosemicarbazones (IV-1-IV-5) can be studied as leads for further structural modification as antifungal agents against V. mali. Particularly, these ergosterol biosynthesis and autophagy pathways can be used as target receptors for design of novel green pesticides for management of congeneric phytopathogenic fungi. © 2023 Society of Chemical Industry.

Recent advances in oridonin derivatives with anticancer activity

Cancer is a leading cause of mortality responsible for an estimated 10 million deaths worldwide in 2020, and its incidence has been rapidly growing over the last decades. Population growth and aging, as well as high systemic toxicity and chemoresistance associated with conventional anticancer therapies reflect these high levels of incidence and mortality. Thus, efforts have been made to search for novel anticancer drugs with fewer side effects and greater therapeutic effectiveness. Nature continues to be the main source of biologically active lead compounds, and diterpenoids are considered one of the most important families since many have been reported to possess anticancer properties. Oridonin is an ent-kaurane tetracyclic diterpenoid isolated from Rabdosia rubescens and has been a target of extensive research over the last few years. It displays a broad range of biological effects including neuroprotective, anti-inflammatory, and anticancer activity against a variety of tumor cells. Several structural modifications on the oridonin and biological evaluation of its derivatives have been performed, creating a library of compounds with improved pharmacological activities. This mini-review aims to highlight the recent advances in oridonin derivatives as potential anticancer drugs, while succinctly exploring their proposed mechanisms of action. To wind up, future research perspectives in this field are also disclosed.

Synthesis of Oleanolic Acid-Dithiocarbamate Conjugates and Evaluation of Their Broad-Spectrum Antitumor Activities

Efficient and mild synthetic routes for bioactive natural product derivatives are of current interest for drug discovery. Herein, on the basis of the pharmacophore hybrid strategy, we report a two-step protocol to obtain a series of structurally novel oleanolic acid (OA)-dithiocarbamate conjugates in mild conditions with high yields. Moreover, biological evaluations indicated that representative compound 3e exhibited the most potent and broad-spectrum antiproliferative effects against Panc1, A549, Hep3B, Huh-7, HT-29, and Hela cells with low cytotoxicity on normal cells. In terms of the IC₅₀ values, these OA-dithiocarbamate conjugates were up to 30-fold more potent than the natural product OA. These compounds may be promising hit compounds for the development of novel anti-cancer drugs.

Discovery of a potent olaparib-chlorambucil hybrid inhibitor of PARP1 for the treatment of cancer

Introduction: Development of Poly (ADP-ribose) polymerase (PARP) inhibitors has been extensively studied in cancer treatment. Olaparib, the first approved PARP inhibitor, showed potency in the inhibition of both BRCA (breast cancer associated)-mutated and BRCA-unmutated cancers. Methods: Aiming to the discovery of olaparib analogs for the treatment of cancer, structural modifications were performed based on the scaffold of olaparib. In the first series, reduction of carbonyl group to CH₂ led to decrease of PARP1 inhibitory activity. Preserving the original carbonyl group, molecules with potent PARP1 inhibitory activities were derived by introduction of hydrazide and aromatic nitrogen mustard groups. The synthesized compounds were evaluated in the in the PARP1 enzyme inhibitory screening, cancer cell based antiproliferative assay, cell cycle arrest and apoptosis studies. Results: It is remarkable that, molecule C2 with chlorambucil substitution, exhibited potent PARP1 inhibitory activity and a broad-spectrum of anticancer potency in the in vitro antiproliferative assay. Compared with olaparib and chlorambucil, molecule C2 also showed significant potency in inhibition of a variety of BRCA-unmutated cell lines. Further analysis revealed the effects of C2 in induction of G2/M phase cell cycle arrest and promotion of apoptosis. Discussion: Collectively, the olaparib-chlorambucil hybrid molecule (C2) could be utilized as a lead compound for further drug design.

Research progress on antitumor activity of XRP44X and analogues as microtubule targeting agents

Cancer threatens human health and life. Therefore, it is particularly important to develop safe and effective antitumor drugs. Microtubules, the main component of cytoskeleton, play an important role in maintaining cell morphology, mitosis, and signal transduction, which are one of important targets of antitumor drug research and development. Colchicine binding site inhibitors have dual effects of inhibiting proliferation and destroying blood vessels. In recent years, a series of inhibitors targeting this target have been studied and some progress has been made. XRP44X has a novel structure and overcomes some disadvantages of traditional inhibitors. It is also a multifunctional molecule that regulates not only the function of tubulin but also a variety of biological pathways. Therefore, the structure, synthesis, structure-activity relationship, and biological activity of XRP44X analogues reported in recent years were summarized in this paper, to provide a useful reference for the rational design of efficient colchicine binding site inhibitors.

Discovery of Resveratrol and its Derivatives as Novel Antiviral and Anti- Phytopathogenic-Fungus Agents

BACKGROUND

Plant diseases caused by viruses and pathogens have posed a serious threat to global agricultural production and are difficult to control. Natural products have always been a valuable source for lead discovery in medicinal and agricultural chemistry. The natural product resveratrol was found to have good antiviral activity against the tobacco mosaic virus (TMV) and fungicidal activities against 14 kinds of phytopathogenic fungi.

OBJECTIVE

The aim of this work was to design, synthesize a series of derivatives of resveratrol, and evaluate their antiviral and fungicidal activities systematically.

METHODS

Novel resveratrol sulfonate derivatives were prepared by a convenient synthesis method from resveratrol, alkyl sulfonyl chloride, aryl sulfonyl chloride, and heterocyclic sulfonyl chloride. Their structures were also identified by nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS).

RESULTS

Most of the targets were obtained at a high yield. Compounds I-2, I-5, I-10, II-2, and II-4, with excellent antiviral activities, showed higher anti-TMV activities than those of lead compounds and commercial ribavirin (inhibitory rates of 38, 37, and 38% at 500 μg/mL for inactivation, curative, and protection activities in vivo, respectively). In particular, compounds I-5, I-10, II-2, and II-4 displayed similar inhibitory effects as ningnanmycin (inhibitory rates of 54, 56, and 58% at 500 μg/mL for inactivation, curative, and protection activities in vivo, respectively), the best antiviral agent at present, thereby emerging as new antiviral pilot compounds. Further fungicidal activity tests showed that resveratrol derivatives also displayed broad-spectrum fungicidal activities.

CONCLUSION

The anti-TMV activities of these compounds were discovered for the first time. Some of these simply structured compounds showed higher TMV inhibitory effects than ribavirin. The current study provided valuable insights into the antiviral and fungicidal activities of resveratrol derivatives, but more modification of the structure should be conducted.

Synthesis and Biological Evaluation of Gentiopicroside Derivatives as Novel Cyclooxygenase-2 Inhibitors with Anti-Inflammatory Activity

Purpose

Nonsteroidal anti-inflammatory drugs cause a series of adverse reactions. Thus, the search for new cyclooxygenase-2 selective inhibitors have become the main direction of research on anti-inflammatory drugs. Gentiopicroside is a novel selective inhibitor of cyclooxygenase-2 from Chinese herbal medicine. However, it is highly hydrophilic owing to the presence of the sugar fragment in its structure that reduces its oral bioavailability and limits efficacy. This study aimed to design and synthesize novel cyclooxygenase-2 inhibitors by modifying gentiopicroside structure and reducing its polarity.

Materials and Methods

We introduced hydrophobic acyl chloride into the gentiopicroside structure to reduce its hydrophilicity and obtained some new derivatives. Their in vitro anti-inflammatory activities were evaluated against NO, TNF-α, PGE₂, and IL-6 production in the mouse macrophage cell line RAW264.7 stimulated by lipopolysaccharide. The in vivo inhibitory activities were further tested against xylene-induced mouse ear swelling. Molecular docking predicted that whether new compounds could effectively bind to target protein cyclooxygenase-2. The inhibitory activity of new compounds to cyclooxygenase-2 enzyme were verified by the in vitro experiment.

Results

A total of 21 novel derivatives were synthesized, and exhibit lower polarities than the gentiopicroside. Most compounds have good in vitro anti-inflammatory activity. The in vivo activity results demonstrated that 8 compounds were more active than gentiopicroside. The inhibition rate of some compounds was higher than celecoxib. Molecular docking predicted that 6 compounds could bind to cyclooxygenase-2 and had high docking scores in accordance with their potency of the anti-inflammatory activity. The confirmatory experiment proved that these 6 compounds had significant inhibitory effect against cyclooxygenase-2 enzyme. Structure-activity relationship analysis presumed that the para-substitution with the electron-withdrawing groups may benefit the anti-inflammatory activity.

Conclusion

These gentiopicroside derivatives especially PL-2, PL-7 and PL-8 may represent a novel class of cyclooxygenase-2 inhibitors and could thus be developed as new anti-inflammatory agents.

Synthesis of Piperine-Based Ester Derivatives with Diverse Aromatic Rings and Their Agricultural Bioactivities against Tetranychus cinnabarinus Boisduval, Aphis citricola Van der Goot, and Eriosoma lanigerum Hausmann

Exploration of plant secondary metabolites or by using them as leads for development of new pesticides has become one of the focal research topics nowadays. Herein, a series of new ester derivatives of piperine were prepared via the Vilsmeier−Haack−Arnold (VHA) reaction, and their structures were characterized by infrared spectroscopy (IR), melting point (mp), proton nuclear magnetic resonance spectroscopy (1H NMR), and carbon nuclear magnetic resonance spectroscopy (13C NMR). Notably, the steric configurations of compounds 6 and 7 were confirmed by single-crystal analysis. Against T. cinnabarinus, compounds 9 and 11 exhibited 47.6- and 45.4-fold more pronounced acaricidal activity than piperine. In particular, compounds 9 and 11 also showed 2.6-fold control efficiency on the fifth day of piperine. In addition, compound 6 (>10−fold higher than piperine) displayed the most potent aphicidal activity against A. citricola. Furthermore, some derivatives showed good aphicidal activities against E. lanigerum. Moreover, the effects of compounds on the cuticles of T. cinnabarinus were investigated by the scanning electron microscope (SEM) imaging method. This study will pave the way for future high value added application of piperine and its derivatives as botanical pesticides.

Chemistry and Biological Activities of Naturally Occurring and Structurally Modified Podophyllotoxins

Plants containing podophyllotoxin and its analogues have been used as folk medicines for centuries. The characteristic chemical structures and strong biological activities of this class of compounds attracted attention worldwide. Currently, more than ninety natural podophyllotoxins were isolated, and structure modifications of these molecules were performed to afford a variety of derivatives, which offered optimized anti-tumor activity. This review summarized up to date reports on natural occurring podophyllotoxins and their sources, structural modification and biological activities. Special attention was paid to both structural modification and optimized antitumor activity. It was noteworthy that etoposide, a derivative of podophyllotoxin, could prevent cytokine storm caused by the recent SARS-CoV-2 viral infection.

High Value-Added Application of Natural Plant Products in Crop Protection: Construction and Pesticidal Activities of Piperine-Type Ester Derivatives and Their Toxicology Study

To discover new potential pesticide candidates, recently, structural modification of natural bioactive products has received much attention. In this work, a series of new piperine-type ester derivatives were regio- and stereoselectively synthesized based on a natural alkaloid piperine isolated from Piper nigrum. Their structures were characterized by IR, mp, ¹H NMR (¹³C NMR), and high-resolution mass spectrometry (HRMS). Against Tetranychus cinnabarinus Boisduval (Acari: Tetranychidae), compounds 4e, 4f, 4u, and 4v displayed the most significant acaricidal activity with LC₅₀ values of 0.155, 0.117, 0.177, and 0.164 mg/mL, respectively. Particularly, compound 4f showed >120-fold higher acaricidal activity than piperine (LC₅₀: 14.198 mg/mL). Notably, the acaricidal activity of 4f was equivalent to that of the commercial acaricide spirodiclofen (LC₅₀: 0.115 mg/mL). Additionally, against Eriosoma lanigerum Hausmann (Hemiptera: Aphididae), compounds 4w and 4b' showed 1.8-fold aphicidal activity of piperine. Furthermore, via the scanning electron microscope (SEM) imaging method, the obvious destruction of the construction of the cuticle layer of 4f-treated T. cinnabarinus was observed. Compound 4f could be further studied as a lead acaricidal agent.

Semisynthesis and Pesticidal Activities of Novel Cholesterol Ester Derivatives Containing Cinnamic Acid-like Fragments

Due to the extensive use of agrochemicals resulting in the emergence of pesticide resistance and ecological environment problems, the research and development of new alternatives for crop protection is highly desirable. In order to discover potent natural product-based insecticide candidates, a series of new cholesterol ester derivatives containing cinnamic acid-like fragments at the C-7 position were synthesized. Some derivatives showed potent pesticidal activities. Against Mythimna separata Walker, compounds 2a, Id, Ig, and IIg showed 2.1-2.4-fold growth-inhibitory activity of the precursor cholesterol. Against Plutella xylostella Linnaeus, compounds Ig, IIf, and IIi exhibited 1.9-2.1-fold insecticidal activity of cholesterol. These results will pave the way for the future synthesis of cholesterol-based derivatives as agrochemicals.

Natural products as sources of acetylcholinesterase inhibitors: Synthesis, biological activities, and molecular docking studies of osthole-based ester derivatives

Osthole is a natural coumarin compound which isolated from Cnidium monnieri (L.) Cusson, has extensive pharmacological activities and could be used as a leading compound for drug research and development. In a continuous effort to develop new acetylcholinesterase inhibitors from natural products, eighteen osthole esters were designed, synthesized, and confirmed by ¹H NMR, ¹³C NMR and HRMS. The anti-AChE activity of These derivatives was measured at a concentration of 1.0 mol/mL in vitro by Ellman's method, and the result showed that 4m and 4o had moderate inhibitory activities with 68.8% and 62.6%, respectively. Molecular docking study results further revealed AChE interacted optimally with docking poses 4m and 4o. Network pharmacology also predicted that compound 4m could be involved in Ras signaling pathway, which made it a potential therapeutic target of AD.

Modification of Whey Proteins by Sonication and Hydrolysis for the Emulsification and Spray Drying Encapsulation of Grape Seed Oil

In this study, whey protein concentrate (WPC) was sonicated or partially hydrolyzed by Alcalase, then examined as an emulsifier and carrier for the emulsification and spray drying of grape seed oil (GSO)-in-water emulsions. The modification treatments increased the free amino acid content and antioxidant activity (against DPPH and ABTS free radicals), as well as, the solubility, emulsifying, and foaming activities of WPC. The modified WPC-stabilized emulsions had smaller, more homogeneous droplets and a higher zeta potential as compared to intact WPC. The corresponding spray-dried powders also showed improved encapsulation efficiency, oxidative stability, reconstitution ability, flowability, solubility, and hygroscopicity. The morphology of particles obtained from the primary WPC (matrix type, irregular with surface pores) and modified WPC (reservoir type, wrinkled with surface indentations), as well as the oxidative stability of the GSO were influenced by the functional characteristics and antioxidant activity of the carriers. Changes in the secondary structures and amide regions of WPC, as well as the embedding of GSO in its matrix, were deduced from FTIR spectra after modifications. Partial enzymolysis had better results than ultrasonication; hence, the WPC hydrolysates are recommended as emulsifiers, carriers, and antioxidants for the delivery and protection of bioactive compounds.

Strategies for Solubility and Bioavailability Enhancement and Toxicity Reduction of Norcantharidin

Cantharidin (CTD) is the main active ingredient isolated from Mylabris, and norcantharidin (NCTD) is a demethylated derivative of CTD, which has similar antitumor activity to CTD and lower toxicity than CTD. However, the clinical use of NCTD is limited due to its poor solubility, low bioavailability, and toxic effects on normal cells. To overcome these shortcomings, researchers have explored a number of strategies, such as chemical structural modifications, microsphere dispersion systems, and nanodrug delivery systems. This review summarizes the structure-activity relationship of NCTD and novel strategies to improve the solubility and bioavailability of NCTD as well as reduce the toxicity. This review can provide evidence for further research of NCTD.