Rapid Recognition and Targeted Isolation of Anti-HIV Daphnane Diterpenes from Daphne genkwa Guided by UPLC-MSn

Uncovering the underlying mechanism of yuanhuacine against colorectal cancer by transcriptomics and experimental investigations

BACKGROUND

Colorectal cancer (CRC) holds the third position in terms of incidence and ranks behind lung cancer in terms of mortality worldwide. Yuanhuacine, one of the main active ingredients of genkwa flos, has demonstrated promising application prospects in the field of cancer treatment. However, its underlying mechanism against CRC has not been fully clarified.

PURPOSE

This study aimed to investigate anti-tumor activity of yuanhuacine and clarify its underlying mechanism in CRC.

METHODS

CRC HCT116, HT-29, Caco-2, SW480, and LS174T cells were used to assess the in vitro anti-tumor activity of yuanhuacine by cell viability, proliferation, apoptosis, cycle distribution, migration, and colony formation assays. Meanwhile, an HT-29 xenograft mouse model was successfully constructed to investigate the anti-tumor effect of yuanhuacine in vivo. Transcriptomic assay and network pharmacology were applied to explore the underlying mechanism of yuanhuacine in combating CRC, which was further verified by quantitative reverse transcription polymerase chain reaction, western blot. The interaction of yuanhuacine with protein was performed by molecular docking, molecular dynamics simulation, and cell thermal shift assays.

RESULTS

Yuanhuacine significantly induced apoptosis and reduced viability of CRC cells with IC50 values ranging from 28.09 to 56.16 μM. Moreover, it suppressed the colony formation ability of CRC cells and inhibited the expression of proliferation marker Ki67 in CRC cells and tissues. Meanwhile, the impairment of cell migration by yuanhuacine has been identified by wound healing assay and transwell migration assay. Furthermore, cell cycle assay showed that yuanhuacine resulted in significant G2/M phase arrest. Yuanhuacine significantly inhibited the tumor growth of HT-29 xenograft mice without obvious pathological changes in major organs. Mechanistically, the differentially expressed genes were enriched in cell cycle by both Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses. The mRNA and protein expressions of PLK1, CCNA2, and TTK were inhibited by yuanhuacine. Cell thermal shift assay further validated the direct interactions between yuanhuacine and each of PLK1, CCNA2, and TTK. The anti-proliferation activity and cell cycle arrest induced by yuanhuacine were reversed by overexpression of PLK1.

CONCLUSIONS

Yuanhuacine is a promising candidate compound in combating CRC by inhibiting proliferation of CRC cells. The major underlying mechanism involves regulating PLK1, which results in G2/M phase arrest.

Natural promising daphnane diterpenoids: An integrated review of their sources, structural classification, biological activities, and synthesis

Daphnane diterpenoids, as one of the representative types of diterpenoid compounds with rich structural diversity and significant biological activities, have an uncommon 5/7/6 tricyclic skeleton mainly found in species of Thymelaeaceae and Euphorbiaceae families. Due to the unique peculiarity of the framework and remarkable pharmacological activities, over the past three decades, novel structures have been continuously discovered and more structural subtypes have been derived. However, there is always a lack of a unified and convincing structural classification strategy for the summary of daphnane diterpenoids, which affects the in-depth and systematic research of pharmaceutical chemists and pharmacologists. In addition, the distinctive skeleton, continuous chiral centers, and prominent bioactivities of daphnane diterpenoids have attracted widespread interest among synthetic chemists. However, there are currently only a few reports of complete synthesis of compounds with low overall yields. Given the broad attention paid to daphnane diterpenoids in recent years, this review summarized the sources, structural classification, biological activities, and synthesis of around 300 natural daphnane diterpenoids discovered from 1993 to 2023, providing a reference for further discovery of novel structures, chemical and biological synthesis, and drug research.

Isomer Differentiation by UHPLC-Q-Exactive-Orbitrap MS led to Enhanced Identification of Daphnane Diterpenoids in Daphne tangutica

INTRODUCTION

Liquid chromatography-mass spectrometry (LC-MS) has enhanced the rapid, accurate analysis of complex plant extracts, eliminating the need for extensive isolation. Tandem mass spectrometry (MS/MS) further enhances this process by providing detailed structural information. However, differentiating structural isomers remains a challenge due to their minor spectral and structural differences.

OBJECTIVE

This study aimed to extend the applicability of LC-MS/MS for the structural identification of daphnane diterpenoids, with a particular focus on distinguishing functional isomers.

METHODS

LC-MS analyses were performed using an UHPLC-Q-Exactive-Orbitrap MS. The MS conditions for distinguishing isomers were optimized using in-source CID and HCD modes with reference compounds. A qualitative analysis was then conducted on the extract of Daphne tangutica. The chemical structures of the detected daphnane diterpenoids were estimated by analyzing the fragmentation patterns in both the mass spectra and product ion spectra. These identifications were further validated by isolation and comparison with an in-house daphnane diterpenoid library.

RESULTS

By optimizing MS conditions, especially in the negative ion mode, it was possible to accurately distinguish structural isomers such as yuanhuajine and gniditrin. Qualitative analysis of D. tangutica identified a total of 28 daphnanes, including seven previously unreported compounds. Furthermore, a novel geometric isomer of gniditrin was isolated by conducting isolation on the crude diterpenoid fraction.

CONCLUSION

This study demonstrated that LC-MS/MS analysis can effectively distinguish functional isomers of daphnane diterpenoids, thereby enhancing the identification of daphnanes in plant extracts and highlighting its potential as a powerful tool for phytochemical analysis.

Qualitative Analysis of Daphnane Diterpenoids in Various Parts of Daphne pontica L. by UHPLC-Q-Exactive-Orbitrap MS

INTRODUCTION

Daphne pontica L. is an evergreen shrub that is recorded as an anti-diarrheic plant in Turkish folk medicine. Previous studies on D. pontica have reported, albeit slightly, the isolation of daphnane diterpenoids, but no systematic phytochemical analysis of daphnane diterpenoids has been conducted.

OBJECTIVE

This study aimed to comprehensively investigate daphnane diterpenoids in the extracts from the different parts (stems, leaves, and fruits) of D. pontica.

METHODS

An ultra-high-performance liquid chromatography coupled with Q-Exactive hybrid quadrupole Orbitrap mass spectrometer (UHPLC-Q-Exactive-Orbitrap MS) was used for the qualitative analysis of D. pontica. The stems, leaves, and fruits of D. pontica were extracted with diethyl ether. Each extract was then pretreated by a solid phase extraction cartridge and subjected to LC-MS/MS analysis. Detected daphnane diterpenoids were tentatively identified by comparison with an in-house daphnane library, and their chemical structures were estimated in detail by MS/MS fragmentation evaluation.

RESULTS

A total of 33 kinds of daphnanes were identified from the different parts of D. pontica, and were classified into three subtypes: daphnane orthoester, polyhydroxy daphnane, and macrocyclic daphnane orthoester. Among them, six daphnanes were postulated to be previously unreported compounds based on MS/MS fragmentation elucidation. Furthermore, the three plant parts showed similar daphnane diterpenoid profiles, with the stems containing the most abundant daphnane diterpenoids.

CONCLUSION

This is the first study to perform qualitative analysis of daphnane diterpenoids systematically and comprehensively in different parts of D. pontica. The results revealed that D. pontica is a plant resource rich in a variety of daphnane diterpenoids.

Daphne genkwa: Ethnopharmacology, phytochemistry and pharmacology of an important traditional Chinese medicine

Daphne genkwa, as a traditional medicine, is widely distributed in China, Korea and Vietnam. In China, the dried flower buds of this plant are named "Yuanhua". It has the ability to effectively promote urination, eliminate phlegm and alleviate cough, eliminate parasites and cure of scabies, with a broad spectrum of pharmacological effects and considerable clinical efficacy. This paper provides a summary and classification of the main chemical constituents of D. genkwa based on a review of relevant domestic and foreign literature. It also outlines the current research status of traditional clinical usage, pharmacological effects, and toxicity of D. genkwa. The aim is to provide a theoretical basis for further study of D. genkwa and its potential new clinical applications.

COAP-Pd Catalyzed Asymmetric Formal [3+2] Cycloaddition for Optically Active Multistereogenic Spiro Cyclopentane-Indandiones Bearing Cyclic N-Sulfonyl Ketimine Skeletons

We reported a chiral oxamide-phosphine ligand (COAP-Ph)-Pd-catalyzed asymmetric [3+2] cycloaddition reaction between vinyl cyclopropane compounds derived from 1,3-indanedione and 2-vinylcyclopropane-1,1-dicarboxylates with cyclic sulfonyl 1-azadienes. The corresponding reactions provided a series of enantiomerically active spiro cyclopentane-indandione and cyclopentane structures bearing three consecutive stereogenic centers in good yields with good diastereo- and enantioselectivity. The COAP-Pd complex serves not only to promote generation of chiral π-allyl-palladium intermediates and induce the asymmetry of the reaction, but also depress the background reaction.

Asymmetric Construction of the Core of C6, C7-Epoxy Daphnane Diterpenoid Orthoesters

Asymmetric construction of the core of C6, C7-epoxy daphnane diterpenoid orthoesters is developed through a convergent synthetic strategy. The salient features include a diastereoselective nucleophilic assembly of two bulky cyclic fragments, an oxidative cleavage/transesterification/aldol cascade to fashion the seven-membered ring, and a base-mediated transesterification/retro-aldol/aldol/epoxidation cascade to install the epoxy moiety with proper stereochemistry.

Isolation and Identification of 12-Deoxyphorbol Esters from Euphorbia resinifera Berg Latex: Targeted and Biased Non-Targeted Identification of 12-Deoxyphorbol Esters by UHPLC-HRMSE

Diterpenes from the Euphorbia genus are known for their ability to regulate the protein kinase C (PKC) family, which mediates their ability to promote the proliferation of neural precursor cells (NPCs) or neuroblast differentiation into neurons. In this work, we describe the isolation from E. resinifera Berg latex of fifteen 12-deoxyphorbol esters (1-15). A triester of 12-deoxy-16-hydroxyphorbol (4) and a 12-deoxyphorbol 13,20-diester (13) are described here for the first time. Additionally, detailed structural elucidation is provided for compounds 3, 5, 6, 14 and 15. The absolute configuration for compounds 3, 4, 6, 13, 14 and 15 was established by the comparison of their theoretical and experimental electronic circular dichroism (ECD) spectra. Access to the above-described collection of 12-deoxyphorbol derivatives, with several substitution patterns and attached acyl moieties, allowed for the study of their fragmentation patterns in the collision-induced dissociation of multiple ions, without precursor ion isolation mass spectra experiments (HRMSE), which, in turn, revealed a correlation between specific substitution patterns and the fragmentation pathways in their HRMSE spectra. In turn, this allowed for a targeted UHPLC-HRMSE analysis and a biased non-targeted UHPLC-HRMSE analysis of 12-deoxyphorbols in E. resinifera latex which yielded the detection and identification of four additional 12-deoxyphorbols not previously isolated in the initial column fractionation work. One of them, identified as 12-deoxy-16-hydroxyphorbol 20-acetate 13-phenylacetate 16-propionate (20), has not been described before.

Identification of Daphnane Diterpenoids from Wikstroemia indica Using Liquid Chromatography with Tandem Mass Spectrometry

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) has emerged as a powerful tool for the rapid identification of compounds within natural resources. Daphnane diterpenoids, a class of natural compounds predominantly found in plants belonging to the Thymelaeaceae and Euphorbiaceae families, have attracted much attention due to their remarkable anticancer and anti-HIV activities. In the present study, the presence of daphnane diterpenoids in Wikstroemia indica, a plant belonging to the Thymelaeaceae family, was investigated by LC-MS/MS analysis. As a result, 21 daphnane diterpenoids (1-21) in the stems of W. indica were detected. Among these, six major compounds (12, 15, 17, 18, 20, and 21) were isolated and their structures were unequivocally identified through a comprehensive analysis of the MS and NMR data. For the minor compounds (1-11, 13, 14, 16, and 19), their structures were elucidated by in-depth MS/MS fragmentation analysis. This study represents the first disclosure of structurally diverse daphnane diterpenoids in W. indica, significantly contributing to our understanding of bioactive diterpenoids in plants within the Thymelaeaceae family.

Tigliane and daphnane diterpenoids from Thymelaeaceae family: chemistry, biological activity, and potential in drug discovery

Tigliane and daphnane diterpenoids are characteristically distributed in plants of the Thymelaeaceae family as well as the Euphorbiaceae family and are structurally diverse due to the presence of polyoxygenated functionalities in the polycyclic skeleton. These diterpenoids are known as toxic components, while they have been shown to exhibit a wide variety of biological activities, such as anti-cancer, anti-HIV, and analgesic activity, and are attracting attention in the field of natural product drug discovery. This review focuses on naturally occurring tigliane and daphnane diterpenoids from plants of the Thymelaeaceae family and provides an overview of their chemical structure, distribution, isolation, structure determination, chemical synthesis, and biological activities, with a prime focus on the recent findings.

Identification of Daphne genkwa and Its Vinegar-Processed Products by Ultraperformance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry and Chemometrics

Crude herbs of Daphne genkwa (CHDG) are often used in traditional Chinese medicine to treat scabies baldness, carbuncles, and chilblain owing to their significant purgation and curative effects. The most common technique for processing DG involves the use of vinegar to reduce the toxicity of CHDG and enhance its clinical efficacy. Vinegar-processed DG (VPDG) is used as an internal medicine to treat chest and abdominal water accumulation, phlegm accumulation, asthma, and constipation, among other diseases. In this study, the changes in the chemical composition of CHDG after vinegar processing and the inner components of the changed curative effects were elucidated using optimized ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Untargeted metabolomics, based on multivariate statistical analyses, was also used to profile differences between CHDG and VPDG. Eight marker compounds were identified using orthogonal partial least-squares discrimination analysis, which indicated significant differences between CHDG and VPDG. The concentrations of apigenin-7-O-β-d-methylglucuronate and hydroxygenkwanin were considerably higher in VPDG than those in CHDG, whereas the amounts of caffeic acid, quercetin, tiliroside, naringenin, genkwanines O, and orthobenzoate 2 were significantly lower. The obtained results can indicate the transformation mechanisms of certain changed compounds. To the best of our knowledge, this study is the first to employ mass spectrometry to detect the marker components of CHDG and VPDG.

Metabolism, pharmacokinetics, and bioavailability of yuanhuacine in rat using LC-MS

Yuanhuacine is a Daphne-type diterpene ortho-ester and is one of the main active ingredients of genkwa flos. Anticancer activity of yuanhuacine has been well investigated in various tumor cells and animal models, but information on metabolism and pharmacokinetics is limited. The aims of the present study were to investigate the metabolic and pharmacokinetic profiles of yuanhuacine in rat. The metabolic profile of yuanhuacine was obtained from rat plasma, urine, and feces using ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. A total of seven metabolites were detected, and the proposed metabolic pathways involved oxidation and glucuronidation. A simple and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed for the determination of yuanhuacine in rat plasma. The linear range of yuanhuacine was 1-1000 ng/ml (R²  = 0.998). The intra- and inter-precision (coefficient of variation %) of the assay was 3.86-6.18% and 2.65-5.75%, respectively, and the intra- and inter-accuracy (relative error %) was -3.83-4.77% and -3.03-5.11%, respectively. The extraction recovery, matrix effect, stability, and incurred sample reanalysis of yuanhuacine were within acceptable levels. The established method was validated and successfully applied to the preclinical pharmacokinetic study of yuanhuacine. The absolute oral bioavailability of yuanhuacine was calculated as 1.14%, and it reached the maximum plasma concentration of 28.21 ± 2.79 ng/ml in rat plasma at 2 h in the oral dosing group. The apparent volume of distribution of intravenous and intragastric administrations was 26.07 ± 6.45 and 21.83 ± 3.54 L/kg, respectively. The half-life of elimination of yuanhuacine was 9.64 ± 1.53 h in the intravenous dosing group.

Lead/Drug Discovery from Natural Resources

Natural products and their derivatives have been shown to be effective drug candidates against various diseases for many years. Over a long period of time, nature has produced an abundant and prosperous source pool for novel therapeutic agents with distinctive structures. Major natural-product-based drugs approved for clinical use include anti-infectives and anticancer agents. This paper will review some natural-product-related potent anticancer, anti-HIV, antibacterial and antimalarial drugs or lead compounds mainly discovered from 2016 to 2022. Structurally typical marine bioactive products are also included. Molecular modeling, machine learning, bioinformatics and other computer-assisted techniques that are very important in narrowing down bioactive core structural scaffolds and helping to design new structures to fight against key disease-associated molecular targets based on available natural products are considered and briefly reviewed.

Target isolation of cytotoxic diterpenoid esters and orthoesters from Daphne tangutica maxim based on molecular networking

Guiding by LC-MS/MS analysis and the GNPS Molecular Networking, five undescribed daphnane diterpenoids, tanguticanines A-E, and eleven known analogues were discovered from the whole plants of Daphne tangutica Maxim. Their structures and absolute configurations were determined via extensive NMR spectroscopic analysis, ECD calculations, and X-ray diffraction crystallography. Tanguticanine E (5) exhibited promising cytotoxicity against the HepG2 cell line with an IC₅₀ value of 9.93 ± 0.10 μM. Further flow cytometry experiment was performed to detect cell apoptosis, and the results indicated that cytotoxic diterpenoids (tanguticanines B, D and E, altadaphnan C, gniditrin, hirsein A and simplexin) exert their effects through induction of apoptosis.

Daphnane-Type Diterpenes from Stelleropsis tianschanica and Their Antitumor Activity

Four new daphnane-type diterpenes named tianchaterpenes C-F (1–4) and six known ones were isolated from Stelleropsis tianschanica. Their structures were elucidated based on chemical and spectral analyses. The comparisons of calculated and experimental electronic circular dichroism (ECD) methods were used to determine the absolute configurations of new compounds. Additionally, compounds 1–10 were evaluated for their cytotoxic activities against HGC-27 cell lines; the results demonstrate that compound 2 had strong cytotoxic activities with IC₅₀ values of 8.8 µM, for which activity was better than that of cisplatin (13.2 ± 0.67 µM).

Guided isolation of daphnane-type diterpenes from Daphne genkwa by molecular network strategies

A molecular networking-guided study on the Daphne genkwa Sieb. et Zucc led to the isolation of twelve daphnane-type diterpenoids including four undescribed compounds, yuanhuakines A-D. Their structures were elucidated by spectroscopic analyses, ECD calculations, and single-crystal X-ray diffraction analysis. All isolates were evaluated for their inhibitory activity against the A549, Hep3B, and MCF-7 cell lines. The majority of compounds inhibited A549 cells with IC₅₀ values ranging from 7.77 to 20.56 μM, and their structure-activity relationship is preliminarily discussed. Five of these compounds were selected for further experiments, and they appear to inhibit A549 cell lines by inducing apoptosis.

Yuanhuacin and Related Anti-Inflammatory and Anticancer Daphnane Diterpenes from Genkwa Flos-An Overview

The dried flower buds of the plant Daphne genkwa Sieb. et Zucc. have been largely used in traditional Chinese medicine for the treatment of inflammatory diseases. Numerous diterpenoids have been isolated from the Genkwa Flos (yuanhua in Chinese), including a series of daphnane-type diterpene designated as yuanhuacin (YC, often improperly designated as yuanhuacine) and analogues with a patronymic name. The series includes ten daphnane-type diterpenes: yuanhuacin, yuanhuadin (YD), yuanhuafin (YF), yuanhuagin (YG), yuanhuahin (YH), yuanhuajin (YJ), yuanhualin (YL), yuanhuamin (YM), yuanhuapin (YP), and yuanhuatin (YT). They are distinct from the rare flavonoid yuanhuanin. The series comprises several anticancer agents, such as the lead compound YC, which has revealed potent activity in vitro and in vivo against models of lung and breast cancers. The main signaling pathways implicated in the antitumor effects have been delineated. Protein kinase C is a key factor of activity for YC, but in general the molecular targets at the origin of the activity of these compounds remain little defined. Promising anticancer effects have been reported with analogues YD and YT, whereas compounds YF and YP are considered more toxic. The pharmacological activity of each compound is presented, as well as the properties of Genkwa Flos extracts. The potential toxic effects associated with the use of these compounds are also underlined.

Phytochemistry and Pharmacological Activities of the Diterpenoids from the Genus Daphne

There are abundant natural diterpenoids in the plants of the genus Daphne from the Thymelaeaceae family, featuring a 5/7/6-tricyclic ring system and usually with an orthoester group. So far, a total of 135 diterpenoids has been isolated from the species of the genus Daphne, which could be further classified into three main types according to the substitution pattern of ring A and oxygen-containing functions at ring B. A variety of studies have demonstrated that these compounds exert a wide range of bioactivities both in vitro and in vivo including anticancer, anti-inflammatory, anti-HIV, antifertility, neurotrophic, and cholesterol-lowering effects, which is reviewed herein. Meanwhile, the fascinating structure-activity relationship is also concluded in this review in the hope of providing an easy access to available information for the synthesis and optimization of efficient drugs.

Identification of anti-HIV macrocyclic daphnane orthoesters from Wikstroemia ligustrina by LC-MS analysis and phytochemical investigation

Macrocyclic daphnane orthoesters (MDOs) have attracted significant research interest for the drug discovery to cure HIV infection based on the "Shock and Kill" strategy. In the present study, the first chemical study on Wikstroemia ligustrina (Thymelaeaceae) was carried out by LC-MS analysis and phytochemical investigation. Nine daphnane diterpenoids (1-9) including seven MDOs were detected by LC-MS analysis. Further phytochemical investigation resulted in the isolation and structural elucidation of five daphnanes (1, 2, 5, 8, and 9) with potent anti-HIV activity. Taking the isolated MDO (1) as a model compound, the MS/MS fragmentation pathway was also elucidated.

Daphnane Diterpenoids from Daphne genkwa Inhibit PI3K/Akt/mTOR Signaling and Induce Cell Cycle Arrest and Apoptosis in Human Colon Cancer Cells

Seven new daphnane-type diterpenoids, daphgenkins A-G (1-7), and 15 known analogues (8-22) were isolated from the flower buds of Daphne genkwa. Their structures and absolute configurations were elucidated by spectroscopic data and calculated ECD analyses. The cytotoxicities of all daphnane-type diterpenoids (1-22) obtained were evaluated against three human colon cancer cell lines (SW620, RKO, and LoVo). Compounds 1, 12, and 13 exhibited cytotoxic effects against the SW620 and RKO cell lines, with IC₅₀ values in the range of 3.0-9.7 μM. The most active new compound, 1, with an IC₅₀ value of 3.0 μM against SW620 cells, was evaluated further for its underlying molecular mechanism. Compound 1 induced G₀/G₁ cell cycle arrest, leading to the induction of apoptosis in SW620 cells. Also, it induced cancer cell apoptosis by an increased ratio of Bax/Bcl-2, activated cleaved caspase-3 and caspase-9, and upregulated PARP. Finally, compound 1 significantly inhibited PI3K/Akt/mTOR signaling in SW620 cells. Together, the results suggest that compound 1 may be a suitable lead compound for further biological evaluation.

Discovery, synthesis, and optimization of an N-alkoxy indolylacetamide against HIV-1 carrying NNRTI-resistant mutations from the Isatis indigotica root

From an aqueous decoction of the traditional Chinese medicine "ban lan gen" (the Isatis indigotica root), an antiviral natural product CI - 39 was isolated as an NNRTI (non-nucleoside reverse transcriptase inhibitor) (EC50 = 3.40 μM). Its novel structure was determined as methyl (1-methoxy-1H-indol-3-yl)acetamidobenzoate by spectroscopic data and confirmed by single crystal X-ray diffraction. Through synthesis and structure-activity relationship (SAR) investigation of CI - 39 and 57 new derivatives (24 with EC50 values of 0.06-8.55 μM), two optimized derivatives 10f and 10i (EC50: 0.06 μM and 0.06 μM) having activity comparable to that of NVP (EC50 = 0.03 μM) were obtained. Further evaluation verified that 10f and 10i were RT DNA polymerase inhibitors and exhibited better activities and drug resistance folds compared to NVP against seven NNRTI-resistant strains carrying different mutations. Especially, 10i (EC50 = 0.43 μM) was more active to the L100I/K103N double-mutant strain as compared to both NVP (EC50 = 0.76 μM) and EFV (EC50 = 1.08 μM). The molecular docking demonstrated a possible binding pattern between 10i and RT and revealed activity mechanism of 10i against the NNRTI-resistant strains.