Comprehensive Structure-activity Relationship Research Articles

Covalent DNA-Encoded Library Workflow Drives Discovery of SARS-CoV-2 Nonstructural Protein Inhibitors.

The COVID-19 pandemic, exacerbated by persistent viral mutations, underscored the urgent need for diverse inhibitors targeting multiple viral proteins. In this study, we utilized covalent DNA-encoded libraries to discover innovative triazine-based covalent inhibitors for the 3-chymotrypsin-like protease (3CLpro, Nsp5) and the papain-like protease (PLpro) domains of Nsp3, as well as novel non-nucleoside covalent inhibitors for the nonstructural protein 12 (Nsp12, RdRp). Optimization through molecular docking and medicinal chemistry led to the development of LU9, a nonpeptide 3CLpro inhibitor with an IC50 of 0.34 μM, and LU10, whose crystal structure showed a distinct binding mode within the 3CLpro active site. The X-ray cocrystal structure of SARS-CoV-2 PLpro in complex with XD5 uncovered a previously unexplored binding site adjacent to the catalytic pocket. Additionally, a non-nucleoside covalent Nsp12 inhibitor XJ5 achieved a potency of 0.12 μM following comprehensive structure-activity relationship analysis and optimization. Molecular dynamics revealed a potential binding mode. These compounds offer valuable chemical probes for target validation and represent promising candidates for the development of SARS-CoV-2 antiviral therapies.

Phenoxy-1,2-dioxetane-based activatable chemiluminescent probes: tuning of photophysical properties for tracing enzymatic activities in living cells.

The use of chemiluminophores for tracing enzymatic activities in live-cell imaging has gained significant attention, making them valuable tools for diagnostic applications. Among various chemiluminophores, the phenoxy-1,2-dioxetane scaffold exhibits significant structural versatility and its activation is governed by the chemically initiated electron exchange luminescence (CIEEL) mechanism. This mechanism can be initiated by enzymatic activity, changes in pH, or other chemical stimuli. The photophysical properties of phenoxy-1,2-dioxetanes can be fine-tuned through the incorporation of different substituents on the phenolic ring and by anchoring them with specific triggers. This review discusses the variations in physicochemical properties, including emission maxima, quantum yield, aqueous solubility, and pKa, as influenced by structural modifications, thereby establishing a comprehensive structure-activity relationship. Furthermore, it categorises the probes based on different enzyme classes, such as hydrolase-sensitive probes, oxidoreductase-responsive probes, and transferase-activatable phenoxy-1,2-dioxetanes, offering a promising platform technology for the early diagnosis of diseases and disorders. The summary section highlights key opportunities and limitations associated with applying phenoxy-1,2-dioxetanes in achieving precise and effective enzyme assays.

Pyrrolo[2,3-D]Pyrimidines as EGFR and VEGFR Kinase Inhibitors: A Comprehensive SAR Review.

Tyrosine kinases are implicated in a wide array of cellular physiological processes, including cell signaling. The discovery of the BCR-ABL tyrosine kinase inhibitor imatinib and its FDA approval in 2001 paved the way for the development of small molecule chemical entities of diverse structural backgrounds as tyrosine kinase inhibitors for the treatment of various ailments. Two of the most prominent tyrosine kinases as drug targets are the epidermal growth factor receptor (EGFR) and the vascular endothelial growth factor receptor (VEGFR), as evidenced by the clinical success of their many inhibitors in the drug market. Among several other physiological roles, EGFR regulates epithelial tissue development and homeostasis, while VEGFR regulates tumor-induced angiogenesis. The pyrrolo[2,3-d]pyrimidine nucleus represents a deaza-isostere of adenine, the nitrogenous base of ATP. The recent introduction of many pyrrolo[2,3-d]pyrimidines to the drug market as tyrosine kinase inhibitors makes them a hot topic in the medicinal chemistry research area at the present time. This review article comprehensively sheds light on the structure-activity relationship (SAR) of pyrrolo[2,3-d]pyrimidines as EGFR and VEGFR tyrosine kinase inhibitors, aiming to provide help medicinal chemists in the design of future pyrrolopyrimidine kinase inhibitors.

Design, synthesis, and structure–activity relationships of xanthine derivatives as broad-spectrum inhibitors of coronavirus replication

Illuminated by insights into the hijacking of host cellular metabolism by coronaviruses, we identified an initial hit compound 7030B-C5, characterized by a xanthine scaffold, via a cellular-level phenotypic screening from a domestic repertoire of lipid-modulating agents. A series of derivatives were synthesized and optimized through comprehensive structure–activity relationship (SAR) studies focusing on the N-1, C-8, and N-7 positions of xanthine and preliminary exploration on the N-3 position and parent nucleus. Compounds 10e, 10f and 10o, featuring modifications at the N-7 position, showed inhibitory activity with half maximal effective concentration (EC50) values in the three-digit nanomolar range against human coronavirus-229E (HCoV-229E). In particular, compound 10o exerted superior potency across various coronavirus strains, including HCoV-229E, HCoV-OC43, and the Omicron variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Further investigations revealed that 10o acted on the post-entry stages of virus replication and exhibited a distinctive antiviral mechanism from that of clinically approved nirmatrelvir and molnupiravir. Moreover, drug combination study indicates that 10o operates additively with nirmatrelvir, molnupiravir or omicsynin B4, a dual inhibitor of host proteases for S protein priming. Additionally, in vivo assessments show that 10o has favorable pharmacokinetic and safety profiles compared to its parent compound 7030B-C5. These findings underscore the potential of 10o as a promising antiviral candidate for the treatment of current and potential future coronavirus infections.

Optimization of B-Ring-Functionalized Antimalarial Tambjamines and Prodiginines.

Malaria has been a deadly enemy of mankind throughout history, affecting over 200 million people annually, along with approximately half a million deaths. Resistance to current therapies is of great concern, and there is a dire need for novel and well-tolerated antimalarials that operate by clinically unexploited mechanisms. We have previously reported that both tambjamines and prodiginines are highly potent novel antiplasmodial agents, but they required rigor optimizations to enhance the oral efficacy, safety, and physicochemical properties. Here, we launched a comprehensive structure-activity relationship study for B-ring-functionalized tambjamines and prodiginines with 54 novel analogues systematically designed and synthesized. A number of compounds exhibited remarkable antiplasmodial activities against asexual erythrocytic Plasmodium parasites, with improved safety and metabolic profiles. Notably, several prodiginines cured erythrocytic Plasmodium yoelii infections after oral 25 mg/kg × 4 days in a murine model and provided partial protection against liver stage Plasmodium berghei sporozoite-induced infection in mice.

Comprehensive Cell Biological Investigation of Cytochalasin B Derivatives with Distinct Activities on the Actin Network.

In search of a more comprehensive structure-activity relationship (SAR) regarding the inhibitory effect of cytochalasin B (2) on actin polymerization, a virtual docking of 2 onto monomeric actin was conducted. This led to the identification of potentially important functional groups of 2 (i.e., the NH group of the isoindolone core (N-2) and the hydroxy groups at C-7 and C-20) involved in interactions with the residual amino acids of the binding pocket of actin. Chemical modifications of 2 at positions C-7, N-2, and C-20 led to derivatives 3-6, which were analyzed for their bioactivities. Compounds 3-5 exhibited reduced or no cytotoxicity in murine L929 fibroblasts compared to that of 2. Moreover, short- and long-term treatments of human osteosarcoma cells (U-2OS) with 3-6 affected the actin network to a variable extent, partially accompanied by the induction of multinucleation. Derivatives displaying acetylation at C-20 and N-2 were subjected to slow intracellular conversion to highly cytotoxic 2. Together, this study highlights the importance of the hydroxy group at C-7 and the NH function at N-2 for the potency of 2 on the inhibition of actin polymerization.

Establishing the Comprehensive Structure−Activity Relationship of the Natural Antibiotic Kibdelomycin/Amycolamicin

Abstract: Kibdelomycin (KBD) and amycolamicin (AMM) are potent natural antibiotics effective against antibiotic‐resistant Gram‐positive pathogens, including vancomycin‐intermediate Staphylococcus aureus (S. aureus, VISA), methicillin‐resistant S. aureus (MRSA), and quinolone‐resistant S. aureus (QRSA). Their antibacterial activity stems from an unprecedented dual mechanism: the lower binding sites occupy the adenosine triphosphate (ATP) binding pocket of bacterial type II topoisomerases, while the upper binding sites disrupt the enzyme dimer interface. This dual action, combined with their unique chemical structures, positions KBD and AMM as promising scaffolds for developing new antibiotics. However, the structure‐activity relationship (SAR) of KBD/AMM remains underexplored due to their highly complex chemical structures. In this study, we utilized total synthesis to produce KBD/AMM analogs with various site modifications and evaluated their antimicrobial activities. Our findings establish the first comprehensive SAR for KBD/AMM, paving the way for the development of novel KBD/AMM‐based antibiotics.

Establishing the Comprehensive Structure-Activity Relationship of the Natural Antibiotic Kibdelomycin/Amycolamicin.

Kibdelomycin (KBD) and amycolamicin (AMM) are potent natural antibiotics effective against antibiotic-resistant Gram-positive pathogens, including vancomycin-intermediate Staphylococcus aureus (S. aureus, VISA), methicillin-resistant S. aureus (MRSA), and quinolone-resistant S. aureus (QRSA). Their antibacterial activity stems from an unprecedented dual mechanism: the lower binding sites occupy the adenosine triphosphate (ATP) binding pocket of bacterial type II topoisomerases, while the upper binding sites disrupt the enzyme dimer interface. This dual action, combined with their unique chemical structures, positions KBD and AMM as promising scaffolds for developing new antibiotics. However, the structure-activity relationship (SAR) of KBD/AMM remains underexplored due to their highly complex chemical structures. In this study, we utilized total synthesis to produce KBD/AMM analogs with various site modifications and evaluated their antimicrobial activities. Our findings establish the first comprehensive SAR for KBD/AMM, paving the way for the development of novel KBD/AMM-based antibiotics.

Hybrids of 3-Hydroxypyridin-4(1H)-ones and Long-Chain 4-Aminoquinolines as Potent Biofilm Inhibitors of Pseudomonas aeruginosa Potentiate Tobramycin and Polymyxin B Activity.

The biofilm formation of Pseudomonas aeruginosa involves multiple complex regulatory pathways; thus, blocking a single pathway is unlikely to achieve the desired antibiofilm efficacy. Herein, a series of hybrids of 3-hydroxypyridin-4(1H)-ones and long-chain 4-aminoquinolines were synthesized as biofilm inhibitors against P. aeruginosa based on a multipathway antibiofilm strategy. Comprehensive structure-activity relationship studies identified compound 30b as the most valuable antagonist, which significantly inhibited P. aeruginosa biofilm formation (IC50 = 5.8 μM) and various virulence phenotypes. Mechanistic studies revealed that 30b not only targets the three quorum sensing systems but also strongly induces iron deficiency signals in P. aeruginosa. Furthermore, 30b demonstrated a favorable in vitro and in vivo safety profile. Moreover, 30b specifically enhanced the antibacterial activity of tobramycin and polymyxin B in in vitro and in vivo combination therapy. Overall, these results highlight the potential of 30b as a novel anti-infective candidate for treating P. aeruginosa infections.

Structural Optimization of Oxaprozin for Selective Inverse Nurr1 Agonism.

Nuclear receptor related 1 (Nurr1, NR4A2) is a ligand-sensing transcription factor with neuroprotective and anti-inflammatory roles widely distributed in the CNS. Pharmacological Nurr1 modulation is considered a promising experimental strategy in Parkinson's and Alzheimer's disease but target validation is incomplete. While significant progress has been made in Nurr1 agonist development, inverse agonists blocking the receptor's constitutive activity are lacking. Here we report comprehensive structure-activity relationship elucidation of oxaprozin which acts as moderately potent and nonselective inverse Nurr1 agonist and RXR agonist. We identified structural determinants selectively driving RXR agonism or inverse Nurr1 agonism of the scaffold enabling the development of selective inverse Nurr1 agonists with enhanced potency and strong efficacy.

Discovery and Optimization of Tetrahydroisoquinoline Derivatives To Enhance Lysosome Biogenesis as Preclinical Candidates for the Treatment of Alzheimer's Disease.

More than 55 million individuals are suffering from Alzheimer's disease (AD), while the effective therapeutic strategies remain elusive. Our previous study identified a lysosome-enhancing lead compound LH2-051 with a tetrahydroisoquinoline scaffold through a novel dopamine transporter-cyclin-dependent kinase 9-transcription factor EB (DAT-CDK9-TFEB) regulation mechanism to promote TFEB activation and lysosome biogenesis. Here, we launched a comprehensive structure-activity relationship study for LH2-051, and 47 new derivatives were designed and synthesized, in which several compounds exhibited remarkable lysosome-enhancing activities. Notably, compounds 37 and 45 exhibited more favorable TFEB activation and lysosome biogenesis capabilities, good safety profiles, and excellent pharmacokinetic profiles with high brain penetration. Further investigations demonstrated that both compounds significantly enhance the clearance of Aβ aggregates and ameliorate the impairment of learning, memory, and cognition in APP/PS1 mice. Overall, these results indicated that compounds 37 and 45 are promising preclinical drug candidates for the treatment of AD.

Design, synthesis, and biological evaluation of first-in-class FABP1 inhibitors for the treatment of NASH

The fatty acid-binding protein 1 (FABP1) is a fatty acid transporter protein that is considered as an emerging target for metabolic diseases. Despite forceful evidence that the inhibition of FABP1 is essential for ameliorating NASH, pharmacological control and validation of FABP1 are hindered by a lack of relevant inhibitors as pharmacological tool. Therefore, the development of effective FABP1 inhibitors is a current focus of research. Herein, we firstly reported the comprehensive structure-activity relationship (SAR) study of novel FABP1 inhibitors derived from high throughput screening of our in-house library, which resulting in the identification of the optimal compound 44 (IC50 = 4.46 ± 0.54 μM). Molecular docking studies revealed that 44 forms stable hydrogen bonds with amino acids around the active pocket of FABP1. Moreover, 44 alleviated the typical histological features of fatty liver in NASH mice, including steatosis, lobular inflammation, ballooning and fibrosis. Additionally, 44 has been demonstrated to have lipid metabolism regulating, anti-oxidative stress and hepatoprotective properties. This study might be provided a promising insight into the field of NASH and inspiration for the development of FABP1 inhibitors.

Discovery of a Potent, Selective, and Cell-Active SPIN1 Inhibitor.

The methyl-lysine reader protein SPIN1 plays important roles in various human diseases. However, targeting methyl-lysine reader proteins has been challenging. Very few cellularly active SPIN1 inhibitors have been developed. We previously reported that our G9a/GLP inhibitor UNC0638 weakly inhibited SPIN1. Here, we present our comprehensive structure-activity relationship study that led to the discovery of compound 11, a dual SPIN1 and G9a/GLP inhibitor, and compound 18 (MS8535), a SPIN1 selective inhibitor. We solved the cocrystal structure of SPIN1 in complex with 11, confirming that 11 occupied one of the three Tudor domains. Importantly, 18 displayed high selectivity for SPIN1 over 38 epigenetic targets, including G9a/GLP, and concentration dependently disrupted the interactions of SPIN1 and H3 in cells. Furthermore, 18 was bioavailable in mice. We also developed 19 (MS8535N), which was inactive against SPIN1, as a negative control of 18. Collectively, these compounds are useful chemical tools to study biological functions of SPIN1.

Abstract 1809: Discovery of novel AXL and MER inhibitors as potential anticancer and immunomodulatory drugs

Abstract In cancer progression, abnormal AXL expression can promote tumor growth, metastasis, and chemotherapy resistance, while MER can identify apoptotic cancer cells and induce immune suppression in the tumor microenvironment. Combining AXL and MER inhibitors could generate a synergistic effect, enhancing antitumor responses, and further suppressing resistance formed by monotherapy with AXL selective or MER selective inhibitors. According to the explicit function of AXL and MER, the development of dual AXL and MER inhibitors may provide tremendous advantages to cancer patients. Drawing on our experience in the discovery of an anti-EGFR and anti-HER2 clinical candidate, we introduced several AXL-active and MER-active pharmacophores into DBPR112. Furthermore, we modified the scaffold and the solubilizing groups to improve the drug-like properties. Our comprehensive structure-activity relationship study led to the discovery of several potent dual AXL and MER inhibitors. Among approximately 200 synthesized compounds, BPR5K230 demonstrated strong inhibitory activities against AXL and MER, along with favorable oral bioavailability (F% = 55%) and promising in vivo antitumor effects in various mouse xenograft models, including MDA-MB-231, 4T1, and MC-38 tumor models. BPR5K230 effectively addressed sorafenib resistance in the Hepa 1-6 model and exhibited significant synergistic antitumor effects when combined with an anti-PD-L1 antibody in the EMT-6 model. As a result, BPR5K230 represents a promising dual AXL/MER kinase inhibitor, and further preclinical evaluation is underway for its development as a potential anticancer and immune-modulating drug. Citation Format: Hsing-Pang Hsieh, Mu-Chun Li, Wan-Ching Yen, Su-Ying Wu, Teng-Kuang Yeh, Ching-Chuan Kuo, Shau-Hua Ueng, Han-Chung Wu. Discovery of novel AXL and MER inhibitors as potential anticancer and immunomodulatory drugs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1809.

A novel antimicrobial peptide with broad-spectrum and exceptional stability derived from the natural peptide Brevicidine

The global issue of antibiotic resistance is increasingly severe, highlighting the urgent necessity for the development of new antibiotics. Brevicidine, a natural cyclic lipopeptide, exhibits remarkable antimicrobial activity against Gram-negative bacteria. In this study, a comprehensive structure-activity relationship of Brevicidine was investigated through 20 newly synthesized cyclic lipopeptide analogs, resulting in the identification of an optimal linear analog 22. The sequence of analog 22 consisted of five d-amino acids and four non-natural amino acid 2,5-diaminovaleric acid (Orn) and conjugated with decanoic acid at N-terminal. Compared to Brevicidine, analog 22 was easier to synthesize, and exerted broad spectrum antimicrobial activity and excellent stability (t1/2 = 40.98 h). Additionally, analog 22 demonstrated a rapid bactericidal effect by permeating non-specifically through the bacterial membranes, thereby minimizing the likelihood of inducing resistance. Moreover, it exhibited remarkable efficacy in combating bacterial biofilms and reversing bacterial resistance to conventional antibiotics. Furthermore, it effectively suppressed the growth of bacteria in vital organs of mice infected with S. aureus ATCC 25923. In conclusion, analog 22 may represent a potential antimicrobial peptide for further optimization.

Design, Synthesis, and Biological Evaluation of 5-(5-Iodo-2-isopropyl-4-methoxyphenoxy)pyrimidine-2,4-diamine (AF-353) Derivatives as Novel DHFR Inhibitors against Staphylococcus aureus.

The high lethality of Staphylococcus aureus infections and the emergence of antibiotic resistance make the development of new antibiotics urgent. Our previous work identified a hit compound h1 (AF-353) as a novel Mycobacterium tuberculosis (Mtb) dihydrofolate reductase (DHFR) inhibitor. Herein, we analyzed the antimicrobial profile of h1 and performed a comprehensive structure-activity relationship (SAR) assay based on h1. The representative compound j9 exhibited potent antibacterial activity against S. aureus without cross-resistance to other antimicrobial classes. Multiple genetic and biochemical approaches showed that j9 directly binds to SaDHFR, resulting in strong inhibition of its enzymatic activity (IC50 = 0.97 nM). Additionally, j9 had an acceptable in vivo safety profile and oral bioavailability (F = 40.7%) and also showed favorable efficacy in a mouse model of methicillin-resistant S. aureus (MRSA) skin infection. Collectively, these findings identified j9 as a novel SaDHFR inhibitor with the potential to combat drug-resistant S. aureus infections.

Sulfone-based human liver pyruvate kinase inhibitors – Design, synthesis and in vitro bioactivity

Non-alcoholic fatty liver disease (NAFLD) is a prevalent pathological condition characterised by the accumulation of fat in the liver. Almost one-third of the global population is affected by NAFLD, making it a significant health concern. However, despite its prevalence, there is currently no approved drug specifically designed for the treatment of NAFLD. To address this critical gap, researchers have been investigating potential targets for NAFLD drug development. One promising candidate is the liver isoform of pyruvate kinase (PKL). In recent studies, Urolithin C, an allosteric inhibitor of PKL, has emerged as a potential lead compound for therapeutic intervention. Building upon this knowledge, our team has conducted a comprehensive structure-activity relationship of Urolithin C. In this work, we have employed a scaffold-hopping approach, modifying the urolithin structure by replacing the urolithin carbonyl with a sulfone moiety. Our structure-activity relationship analysis has identified the sulfone group as particularly favourable for potent PKL inhibition. Additionally, we have found that the presence of catechol moieties on the two aromatic rings further improves the inhibitory activity. The most promising inhibitor from this new series displayed nanomolar inhibition, boasting an IC50 value of 0.07 μM. This level of potency rivals that of urolithin D and significantly surpasses the effectiveness of urolithin C by an order of magnitude. To better understand the molecular interactions underlying this inhibition, we obtained the crystal structure of one of the inhibitors complexed with PKL. This structural insight served as a valuable reference point, aiding us in the design of inhibitors.

Anti-Inflammatory Flavonoids from Agrimonia pilosa Ledeb: Focusing on Activity-Guided Isolation.

To elucidate the anti-inflammatory properties and constituents of Agrimonia pilosa Ledeb. (A. pilosa), a comprehensive investigation was conducted employing activity-guided isolation. The anti-inflammatory effects were evaluated through an in vitro nitric oxide (NO) assay on lipopolysaccharide (LPS)-treated RAW 264.7 macrophage cells. Seven bio-active compounds with anti-inflammatory properties were successfully isolated from the butanol fraction and identified as follows: quercetin-7-O-β-d-rhamnoside (1), apigenin-7-O-β-d-glucopyranoside (2), kaempferol-7-O-β-d-glucopyranoside (3), quercetin (4), kaempferol (5), apigenin (6), and apigenin-7-O-β-d-glucuronide-6″-butylester (7). All isolated compounds showed strong NO inhibitory activity with IC50 values ranging from 1.4 to 31 µM. Compound 6 demonstrated the most potent NO inhibition. Compound 7, a rare flavonoid, was discerned as a novel anti-inflammatory agent, ascertained through its inaugural demonstration of nitric oxide inhibition. Subsequently, a comprehensive structure-activity relationship (SAR) analysis was conducted employing eight flavonoids derived from A. pilosa. The outcomes elucidated that flavones exhibit superior NO inhibitory effects compared to flavonols, and the aglycone form manifests greater potency in NO inhibition than the glycone counterpart. These results highlight A. pilosa as a promising source of effective anti-inflammatory agents and indicate its potential as a health-beneficial dietary supplement and therapeutic material.

Novel anthraquinone amide derivatives as potential glyoxalase-I inhibitors.

This study aimed to identify novel Glyoxalase-I (Glo-I) inhibitors with potential anticancer properties, focusing on anthraquinone amide-based derivatives. We synthesized a series of these derivatives and conducted in silico docking studies to predict their binding interactions with Glo-I. In vitro assessments were performed to evaluate the anti-Glo-I activity of the synthesized compounds. A comprehensive structure-activity relationship (SAR) analysis identified key features responsible for specific binding affinities of anthraquinone amide-based derivatives to Glo-I. Additionally, a 100 ns molecular dynamics simulation assessed the stability of the most potent compound compared to a co-crystallized ligand. Compound MQ3 demonstrated a remarkable inhibitory effect against Glo-I, with an IC50 concentration of 1.45 µM. The inhibitory potency of MQ3 may be attributed to the catechol ring, amide functional group, and anthraquinone moiety, collectively contributing to a strong binding affinity with Glo-I. Anthraquinone amide-based derivatives exhibit substantial potential as Glo-I inhibitors with prospective anticancer activity. The exceptional inhibitory efficacy of compound MQ3 indicates its potential as an effective anticancer agent. These findings underscore the significance of anthraquinone amide-based derivatives as a novel class of compounds for cancer therapy, supporting further research and advancements in targeting the Glo-I enzyme to combat cancer.

Design, Synthesis and Characterization of Deoxycholic Acid-chalcone Conjugates as Antioxidant Agents

Abstract: The present article reports the synthesis, characterization, and antioxidant activity of the chalcone-deoxycholic acid conjugates. The structures of the synthesised bile acidchalcone conjugates have been determined using 1H and 13C NMR spectroscopy. According to the results of the DPPH experiment, compounds 5e (3, 4, 5-methoxy; IC50; 15.04 μg /ml) and 5f (4-hydroxy group; IC50; 11.73 μg /ml) had higher antioxidant activity than the control compound ascorbic acid (IC50; 20.72 μg /ml). The best conjugate was found to be 5f in the DPPH test (IC50: 11.73 μg /ml; 4-hydroxy group), while the best conjugate in the ABTS assay was found to be 5g (IC50: 67.97 μg /ml; pyridine group). It is straightforward to synthesize a huge library of bile acid-derived compounds and employ them in comprehensive structure-activity relationship investigations to identify the compounds with the best antioxidant activity.