Synthesis, structure activity relationship and in vitro anti-influenza virus activity of novel polyphenol-pentacyclic triterpene conjugates

Chemical diversity, traditional uses, and bioactivities of Rosa roxburghii Tratt: A comprehensive review

Rosa roxburghii Tratt (RRT), known as chestnut rose, has been a subject of growing interest because of its diverse chemical composition and wide range of traditional uses. This comprehensive review aimed to thoroughly examine RRT, including its traditional applications, chemical diversity, and various bioactivities. The chemical profile of this plant is characterized by the presence of essential nutrients such as vitamin C (ascorbic acid), flavonoids, triterpenes, organic acids, tannins, phenolic compounds, polysaccharides, carotenoids, triterpenoids, volatile compounds, amino acids, and essential oils. These constituents contribute to the medicinal and nutritional value. Additionally, we explore the multifaceted bioactivities of RRT, including its potential as an anticancer agent, antioxidant, antiaging agent, antiatherogenic agent, hypoglycemic agent, immunoregulatory modulator, radioprotective agent, antimutagenic agent, digestive system regulator, anti-inflammatory agent, cardioprotective agent, and antibacterial agent, and its intriguing role in modulating the gut microbiota. Furthermore, we discuss the geographical distribution and genetic diversity of this plant species and shed light on its ecological significance. This comprehensive review provides a holistic understanding of RRT, bridges traditional knowledge with contemporary scientific research, and highlights its potential applications in medicine, nutrition, and pharmacology.

Synthesis and evaluation of pentacyclic triterpenoids conjugates as novel HBV entry inhibitors targeting NTCP receptor

Chronic liver diseases caused by hepatitis B virus (HBV) are the accepted main cause leading to liver cirrhosis, hepatic fibrosis, and hepatic carcinoma. Sodium taurocholate cotransporting polypeptide (NTCP), a specific membrane receptor of hepatocytes for triggering HBV infection, is a promising target against HBV entry. In this study, pentacyclic triterpenoids (PTs) including glycyrrhetinic acid (GA), oleanolic acid (OA), ursolic acid (UA) and betulinic acid (BA) were modified via molecular hybridization with podophyllotoxin respectively, and resulted in thirty-two novel conjugates. The anti-HBV activities of conjugates were evaluated in HepG2.2.15 cells. The results showed that 66% of the conjugates exhibited lower toxicity to the host cells and had significant inhibitory effects on the two HBV antigens, especially HBsAg. Notably, the compounds BA-PPT1, BA-PPT3, BA-PPT4, and UA-PPT3 not only inhibited the secretion of HBsAg but also suppressed HBV DNA replication. A significant difference in the binding of active conjugates to NTCP compared to the HBV PreS1 antigen was observed by SPR assays. The mechanism of action was found to be the competitive binding of these compounds to the NTCP 157-165 epitopes, blocking HBV entry into host cells. Molecular docking results indicated that BA-PPT3 interacted with the amino acid residues of the target protein mainly through π-cation, hydrogen bond and hydrophobic interaction, suggesting its potential as a promising HBV entry inhibitor targeting the NTCP receptor.

A review of structural modification and biological activities of oleanolic acid

Oleanolic acid (OA), a pentacyclic triterpenoid, exhibits a broad spectrum of biological activities, including antitumor, antiviral, antibacterial, anti-inflammatory, hepatoprotective, hypoglycemic, and hypolipidemic effects. Since its initial isolation and identification, numerous studies have reported on the structural modifications and pharmacological activities of OA and its derivatives. Despite this, there has been a dearth of comprehensive reviews in the past two decades, leading to challenges in subsequent research on OA. Based on the main biological activities of OA, this paper comprehensively summarized the modification strategies and structure-activity relationships (SARs) of OA and its derivatives to provide valuable reference for future investigations into OA.

Recent Efforts in Identification of Privileged Scaffolds as Antiviral Agents

Viral infections are the most important health concern nowadays to mankind, which is unexpectedly increasing the health complications and fatality rate worldwide. The recent viral infection outbreak developed a pressing need for small molecules that can be quickly deployed for the control/treatment of re-emerging or new emerging viral infections. Numerous viruses, including the human immunodeficiency virus (HIV), hepatitis, influenza, SARS-CoV-1, SARS-CoV-2, and others, are still challenging due to emerging resistance to known drugs. Therefore, there is always a need to search for new antiviral small molecules that can combat viral infection with new modes of action. This review highlighted recent progress in developing new antiviral molecules based on natural product-inspired scaffolds. Herein, the structure-activity relationship of the FDA-approved drugs along with the molecular docking studies of selected compounds have been discussed against several target proteins. The findings of new small molecules as neuraminidase inhibitors, other than known drug scaffolds, Anti-HIV and SARS-CoV are incorporated in this review paper.

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.

Application of cinnamic acid in the structural modification of natural products: A review

Natural products can generally exhibit a variety of biological activities, but most show mediocre performance in preliminary activity evaluation. Natural products often require structural modification to obtain promising lead compounds. Cinnamic acid (CA) is readily available and has diverse biological activities and low cytotoxicity. Introducing CA into natural products may improve their performance, enhance biological activity, and reduce toxic side effect. Herein, we aimed to discuss related applications of CA in the structural modification of natural products and provide a theoretical basis for future derivatization and drug development of natural products. Published articles, web databases (PubMed, Science Direct, SCI Finder, and CNKI), and clinical trial websites (https://clinicaltrials.gov/) related to natural products and CA derivatives were included in the discussion. Based on the inclusion criteria, 128 studies were selected and discussed herein. Screening natural products of CA derivatives allowed for classification by their biological activities. The full text is organized according to the biological activities of the derivatives, with the following categories: anti-tumor, neuroprotective, anti-diabetic, anti-microbial, anti-parasitic, anti-oxidative, anti-inflammatory, and other activities. The biological activity of each CA derivative is discussed in detail. Notably, most derivatives exhibited enhanced biological activity and reduced cytotoxicity compared with the lead compound. CA has various advantages and can be widely used in the synthesis of natural product derivatives to enhance the properties of drug candidates or lead compounds.

Synthesis of Novel Pentacyclic Triterpenoid Derivatives that Induce Apoptosis in Cancer Cells through a ROS-dependent, Mitochondrial-Mediated Pathway

Betulinic acid (BA) and oleanolic acid (OA) are plant-derived conjugates found in various medicinal plants that have emerged as potential antitumor agents. Herein, a series of novel BA and OA derivatives were synthesized by conjugation with per-O-methylated-β-cyclodextrin (PM-β-CD), and their anticancer properties against a panel of three human cancer cell lines were evaluated. Two OA-PM-β-CD conjugates (48 and 50) were observed to be the most potent conjugates against the three cell lines (MCF-7, BGC-823, and HL-60), with a 15- to 20-fold decrease in the IC₅₀ values (IC₅₀: 6.06-8.47 μM) compared with their parental conjugate (OA). Annexin V-FITC/propidium iodide staining and Western blot analysis revealed that both conjugates induced apoptosis in HL-60 cells. Additionally, in the representative conjugate 48-treated HL-60 cells, a decrease in mitochondrial membrane potential and subsequent release of cytochrome c into the cytosol were observed, indicating the activation of the intrinsic apoptosis pathway. Furthermore, 48 dramatically induced the generation of reactive oxygen species (ROS) in HL-60 cells, and the corresponding effect could be reversed using the ROS scavenger N-acetylcysteine. Collectively, these results suggest that the novel pentacyclic triterpenoid derivatives trigger the intrinsic apoptotic pathways via the ROS-mediated activation of caspase-3 signaling, inducing cell death in human cancer cells.

Recent advances in medicinal chemistry of oleanolic acid derivatives

Oleanolic acid (OA), a ubiquitous pentacyclic oleanane-type triterpene isolated from edible and medicinal plants, exhibits a wide spectrum of pharmacological activities and tremendous therapeutic potential. However, the undesirable pharmacokinetic properties limit its application and development. Numerous researches on structural modifications of OA have been carried out to overcome this limitation and improve its pharmacokinetic and therapeutic properties. This review aims to compile and summarize the recent progresses in the medicinal chemistry of OA derivatives, especially on structure-activity relationship in the last few years (2010-2021). It gives insights into the rational design of bioactive derivatives from OA scaffold as promising therapeutic agents.

3′-[4-({[3β,28-Bis(acetyloxy)lup-20(29)-en-30-yl]oxy}carbonyl)-1H-1,2,3-triazol-1-yl]-3′-deoxythymidine

The reaction of the azidothymidine (AZT) with the 30-propynoylated derivative of 3,28-O,O′-diacetylbetulin gave a 1,4-disubstituted 1,2,3-triazole. The chemical structure of new derivative was characterized by 1H NMR, 13C NMR and HR-MS. The triterpene-AZT conjugate was tested against a human cancer cell lines such as glioblastoma (SNB-19), amelanotic melanoma (C-32), ovarian adenocarcinoma (SKOV-3) and breast cancer (T47D, and MCF-7). 3′-[4-({[3β,28-Bis(acetyloxy)lup-20(29)-en-30-yl]oxy}carbonyl)-1H-1,2,3-triazol-1-yl]-3′-deoxythymidine shown significant activity against MCF-7 cells, with an IC50 value of 4.37 µM.

Recent Development of Flavonoids with Various Activities

Flavonoids, a series of compounds with C6-C3-C6 structure, mostly originate from plant metabolism. Flavonoids have shown beneficial effects on many aspects of human physiology and health. Recently, many flavonoids with various activities have been discovered, which has led to more and more studies focusing on their physiological and pharmacodynamic activities. The anti-cancer and anti-viral activities especially have attracted the attention of many researchers. Therefore, the discovery and development of flavonoids as anti-disease drugs has great potential and may make significant contribution to fighting diseases. This review focus on the discovery and development of flavonoids in medicinal chemistry in recent years.

Mutual Prodrugs of 5-Fluorouracil: From a Classic Chemotherapeutic Agent to Novel Potential Anticancer Drugs

The development of potent antitumor agents with a low toxicological profile against healthy cells is still one of the greatest challenges facing medicinal chemistry. In this context, the “mutual prodrug” approach has emerged as a potential tool to overcome undesirable physicochemical features and mitigate the side effects of approved drugs. Among broad‐spectrum chemotherapeutics available for clinical use today, 5‐fluorouracil (5‐FU) is one of the most representative, also included in the World Health Organization model list of essential medicines. Unfortunately, severe side effects and drug resistance phenomena are still the primary limits and drawbacks in its clinical use. This review describes the progress made over the last ten years in developing 5‐FU‐based mutual prodrugs to improve the therapeutic profile and achieve targeted delivery to cancer tissues.

H5N1 Avian Flu Infection in Hubbard Broiler Chicken Can Be Prevented or Cured by Methylated Soy Protein During 42 Days Rearing

Methylated soy protein (MSP) which is positively charged with enhanced hydrophobicity may have antiviral action. This study is verifying if MSP can act inhibit H5N1 inside an animal model. Five groups of Hubbard chicks were challenged at the 25th day of the experiment with AIV virus (H5N1; 0.1 × 10⁵ EID₅₀/mL); 1 group did not receive any treatment (positive control), 2 groups (protective) received treatments before and after the challenge (0.1-0.2 g/L in drinking water ad libitum), and 2 groups (curative) received them only after the challenge. The positive control recorded 100% mortality after 3-5 days of infection. Chicken receiving MSP (0.2 g/L), delayed reaching to 100% mortality to the 7^th day after infection, while those receiving MSP low level (0.1 g/L) could achieve 100% survival during the whole incubation period (42 days), either as a preventive or curative approach. H5N1 virus was not detected in the tracheal and cloacal swabs of the groups receiving 0.1 g/L, opposite to the positive control. The low level of MSP (0.1 g/L) reduced the viral titer to about 1% of the positive control in the protective and curative groups after 5 days of infection, and could maintain the bird body-weight, liver and kidney function, and histopathological status within the normal values. Humoral and TLC response in the group receiving both the virus and the MSP (0.1 g/L) may refer to a possibility that MSP-weakened virus has transformed into a vaccine-like material eliciting host immunity.

Design, synthesis, biological evaluation and structure-activity relationship study of quinazolin-4(3H)-one derivatives as novel USP7 inhibitors

Recent research has indicated that the abnormal expression of the deubiquitinase USP7 induces tumorigenesis via multiple cell pathways, and in particular, the p53-MDM2-USP7 pathway is well understood. USP7 is emerging as a promising target for cancer therapy. However, there are limited reports on USP7 inhibitors. Here we report design, synthesis and biological evaluation of novel quinazolin-4(3H)-one derivatives as potent USP7 inhibitors. Our results indicated that the compounds C9 and C19 exhibited the greatest potency against the USP7 catalytic domain, with IC₅₀ values of 4.86 μM and 1.537 μM, respectively. Ub-AMC assays further confirmed IC₅₀ values of 5.048 μM for C9 and 0.595 μM for C19. MTT assays indicated that gastric cancer MGC-803 cells were more sensitive to these compounds than BGC-823 cells. Flow cytometry analysis revealed that C9 restricted cancer cell growth at the G0/G1 and S phases and inhibited the proliferation and clone formation of MGC-803 cells. Further biochemical experiments indicated that C9 decreased the MDM2 protein level and increased the levels of the tumour suppressors p53 and p21 in a dose-dependent manner. Docking studies predicted that solvent exposure of the side chains of C9 and C19 would uniquely form hydrogen bonds with Met407 of USP7. Additionally, C9 exhibited a remarkable anticancer effect in a zebrafish gastric cancer MGC-803 cell model. Our results demonstrated that quinazolin-4(3H)-one derivatives were suitable as leads for the development of novel USP7 inhibitors and especially for anti-gastric cancer drugs.

Synthesis and antiviral activity of a series of novel quinoline derivatives as anti-RSV or anti-IAV agents

We report herein the synthesis of a series of novel quinoline derivatives, based on the lead compound 1a, identified from a rRSV-mGFP high-throughput screening assay. Our results revealed that target compounds 1b, 1g-h, 1af and 1ah (IC₅₀ = 3.10-6.93 μM) had good in vitro activity against RSV, which were better than 1a and ribavirin. In addition, we found that compound 1g displayed the lower cytotoxicity (CC₅₀: 2490.33 μM) and the highest selective index (SI = 673.06), suggesting its promising potential as a candidate for further development. On the other hand, compounds 1a, 1m, 1v, 1ad-1af and 1ah-1ai (IC₅₀s: 1.87-14.28 μM) were more active against IAV than or comparable to ribavirin (IC₅₀: 15.36 ± 0.93 μM). Particularly, the most active compound 1ae (IC₅₀: 1.87 ± 0.58 μM) was found to be 8.2-fold more potent than the reference drug, which could inhibit the virus transcription and replication cycle at an early stage.

Structure-aided optimization of 3-O-β-chacotriosyl epiursolic acid derivatives as novel H5N1 virus entry inhibitors

It is urgent to develop new antiviral agents due to the continuous emergence of drug-resistant strains of influenza virus. Our earlier studies have identified that certain pentacyclic triterpene saponins with 3-O-β-chacotriosyl residue are novel H5N1 virus entry inhibitors. In the present study, a series of C-28 modified 3-O-β-chacotriosyl epiursolic acid derivatives via conjugation with different kinds of sides were synthesized, of which anti-H5N1 activities in A549 cells were evaluated in vitro. Among them, 10 exhibited strongest anti-H5N1 potency at the low-micromole level without cytotoxicity, surpassing the potency of ribavirin. Further mechanism studies of the lead compound 10 based on HI, SPR and molecular modeling revealed that these new 3-epiursolic acid saponins could bind tightly to the viral envelope HA protein, thus blocking the invasion of H5N1 viruses into host cells.

Structure-aided optimization of 3-O-β-chacotriosyl ursolic acid as novel H5N1 entry inhibitors with high selective index

Currently, entry inhibitors contribute immensely in developing a new generation of anti-influenza virus drugs. Our earlier studies have identified that 3-O-β-chacotriosyl ursolic acid (1) could inhibit H5N1 pseudovirus by targeting hemagglutinin (HA). In the present study, a series of C-28 modified pentacyclic triterpene saponins via conjugation with a series of amide derivatives were synthesized and their antiviral activities against influenza A/Duck/Guangdong/99 virus (H5N1) in MDCK cells were evaluated. The SARs analysis of these compounds revealed that introduction of certain amide structures at the 17-COOH of ursolic acid could significantly enhance both their antiviral activity and selective index. This study indicated that the attachment of the methoxy group or Cl atom to the phenyl ring at the ortho- or para-position was crucial to improve inhibitory activity. Mechanism studies demonstrated that these title triterpenoids could bind tightly to the viral envelope HA to block the attachment of viruses to host cells, which was consistent with docking studies.

Design and synthesis of pentacyclic triterpene conjugates and their use in medicinal research

Triterpenoids are natural products from plants and many other organisms that have various biological activities, such as antitumor, antiviral, antimicrobial, and protective activities. This review covers the synthesis and biological evaluation of pentacyclic triterpene (PT) conjugates with other molecules that have been found to increase the IC₅₀ or improve the pharmacological profile of the parent PT. Some of these molecules are designed to target specific proteins or cellular organelles, which has resulted in highly selective lead structures for drug development. Other PT conjugates are useful for investigating their mechanism of action. This concept has been very successful: 1) Many compounds, especially mitochondria-targeting PT conjugates, have reached a selective cytotoxicity at low nanomolar concentrations in cancer cells. 2) A number of PT conjugates have had high activity against HIV or the influenza virus. 3) Fluorescent PT conjugates have been able to visualize the PT in living cells, which has allowed quantification of the uptake and distribution of the PT within the cell. 4) Biotinylated PT conjugates have been used to identify target proteins, which may help to show their mechanism of action. 5) A large number of PT conjugates with polyethylene glycol (PEG), polyamines, etc. form nanometer-sized micelles that have a much better pharmacological profile than the PT alone. In summary, the connection of a PT to an appropriate modifying molecule has resulted in extremely useful semisynthetic compounds with a high potential to treat cancer or viral infections or compounds that are useful for the study of the mechanism of action of PTs at the molecular level.

Design, synthesis of oleanolic acid-saccharide conjugates using click chemistry methodology and study of their anti-influenza activity

The development of entry inhibitors is an emerging approach to the inhibition of influenza virus. In our previous research, oleanolic acid (OA) was discovered as a mild influenza hemagglutinin (HA) inhibitor. Herein, as a further study, we report the preparation of a series of OA-saccharide conjugates via the CuAAC reaction, and the anti-influenza activity of these compounds was evaluated in vitro. Among them, compound 11b, an OA-glucose conjugate, showed a significantly increased anti-influenza activity with an IC₅₀ of 5.47 μM, and no obvious cytotoxic effect on MDCK cells was observed at 100 μM. Hemagglutination inhibition assay and docking experiment indicated that 11b might interfere with influenza virus infection by acting on HA protein. Broad-spectrum anti-influenza experiments showed 11b to be robustly potent against 5 different strains, including influenza A and B viruses, with IC₅₀ values at the low-micromole level. Overall, this finding further extends the utility of OA-saccharide conjugates in anti-influenza virus drug design.

Synthesis and antitumor activity of fluorouracil - oleanolic acid/ursolic acid/glycyrrhetinic acid conjugates

Due to the obvious adverse effects of 5-fluorouracil that limit its clinical usefulness and considering the diverse biological activities of pentacyclic triterpenes, twelve pentacyclic triterpene-5-fluorouracil conjugates were synthesized and their antitumor activities were evaluated. The results indicated that all the single substitution targeted hybrids (7a-12a) possessed much better antiproliferative activities than the double substitution targeted hybrids (7b-12b). Hybrid 12a exhibited good antiproliferative activities against all the tested MDR cell lines. Furthermore, it was revealed that 12a could induce intracellular calcium influx, the generation of ROS, arrest the cell proliferation at the G1 phase, and activate the apoptotic signaling caspase-8, which eventually activates the apoptotic effector caspase-3 and causes the later nuclear apoptosis.