Pleiotropically activation of azaphilone biosynthesis by overexpressing a pathway-specific transcription factor in marine-derived Aspergillus terreus RA2905.

The genome sequencing of Aspergillus terreus reveals that the vast number of predicted biosynthetic gene clusters have not reflected by the metabolic profile observed under conventional culture conditions. In this study, a silent azaphilone biosynthetic gene cluster was activated by overexpressing a pathway-specific transcription factor gene2642 in marine-derived fungus A. terreus RA2905. Consequently, twenty azaphilone compounds were identified from the OE2642 mutant, including 11 new azaphilones and their precursors, azasperones C-J (1-5, 7-9) and preazasperones A-C (15-17). The structures of those new compounds were unambiguously determined on the basis of NMR and HRESIMS spectra analysis, and the absolute configurations were established depending on ECD calculations. Compounds 1 and 2 were the rarely reported naturally occurring azaphilones with 2-N coupled phenyl-derivative. The bioactivity assay revealed that compounds 18-20 exhibited significant anti-inflammatory activity. Based on the occurrence of diverse intermediates and the putative gene functions, a plausible biosynthetic pathway of these compounds was proposed. The above results demonstrated that overexpression of the pathway-specific transcription factor presents a promising approach for enriching fungal secondary metabolites and accelerating the targeted discovery of novel biosynthetic products.

Study on the Anti-Mycobacterium marinum Activity of a Series of Marine-Derived 14-Membered Resorcylic Acid Lactone Derivatives.

With the emergence of drug-resistant strains, the treatment of tuberculosis (TB) is becoming more difficult and there is an urgent need to find new anti-TB drugs. Mycobacterium marinum, as a model organism of Mycobacterium tuberculosis, can be used for the rapid and efficient screening of bioactive compounds. The 14-membered resorcylic acid lactones (RALs) have a wide range of bioactivities such as antibacterial, antifouling and antimalarial activity. In order to further study their bioactivities, we initially constructed a 14-membered RALs library, which contains 16 new derivatives. The anti-M. marinum activity was evaluated in vitro. Derivatives 12, 19, 20 and 22 exhibited promising activity with MIC90 values of 80, 90, 80 and 80 µM, respectively. The preliminary structure-activity relationships showed that the presence of a chlorine atom at C-5 was a key factor to improve activity. Further studies showed that 12 markedly inhibited the survival of M. marinum and significantly reduced the dosage of positive drugs isoniazid and rifampicin when combined with them. These results suggest that 12 is a bioactive compound capable of enhancing the potency of existing positive drugs, and its effective properties make it a very useful leads for future drug development in combating TB resistance.

Semisynthesis, Structure Elucidation and Anti-Mycobacterium marinum Activity of a Series of Marine-Derived 14-Membered Resorcylic Acid Lactones with Interesting Ketal Groups.

The incidence of Mycobacterium marinum infection is on the rise; however, the existing drug treatment cycle is lengthy and often requires multi-drug combination. Therefore, there is a need to develop new and effective anti-M. marinum drugs. Cochliomycin A, a 14-membered resorcylic acid lactone with an acetonide group at C-5' and C-6', exhibits a wide range of antimicrobial, antimalarial, and antifouling activities. To further explore the effect of this structural change at C-5' and C-6' on this compound's activity, we synthesized a series of compounds with a structure similar to that of cochliomycin A, bearing ketal groups at C-5' and C-6'. The R/S configuration of the diastereoisomer at C-13' was further determined through an NOE correlation analysis of CH3 or CH2 at the derivative C-13' position and the H-5' and H-6' by means of a 1D NOE experiment. Further comparative 1H NMR analysis of diastereoisomers showed the difference in the chemical shift (δ) value of the diastereoisomers. The synthetic compounds were screened for their anti-microbial activities in vitro. Compounds 15-24 and 28-35 demonstrated promising activity against M. marinum, with MIC90 values ranging from 70 to 90 µM, closely approaching the MIC90 of isoniazid. The preliminary structure-activity relationships showed that the ketal groups with aromatic rings at C-5' and C-6' could enhance the inhibition of M. marinum. Further study demonstrated that compounds 23, 24, 29, and 30 had significant inhibitory effects on M. marinum and addictive effects with isoniazid and rifampicin. Its effective properties make it an important clue for future drug development toward combatting M. marinum resistance.

New Sulfurated Butyrolactones from the Fungus Penicillium janthinellum.

Deep-sea derived fungi are considered as significant resources to discovery structurally diverse and biologically active natural compounds. In this study, four new sulfurated butyrolactones, penijanthiones A-D (1-4), together with four known analogues (5-8), were isolated from a Mariana Trench-derived fungus Penicilliumjanthinellum SH0301. Compounds 1-4 were the undescribed examples for natural butyrolactones coupling with a mercaptolactate moiety. Their structures including the absolute configurations of these new compounds were elucidated by comprehensive spectroscopic data, and calculated electronic circular dichroism (ECD). The plausible biosynthetic pathway of sulfur-incorporation of 1-4 was proposed. All of these isolated compounds were evaluated their cytotoxic, antimicrobial and antiviral activities.

Inhibition of influenza A virus replication by a marine derived quinolone alkaloid targeting virus nucleoprotein.

Owing to the emergence of drug resistance and high morbidity and mortality, the need for novel anti-influenza A virus (IAV) drugs with divergent targets is highly sought after. Herein, a novel quinolone alkaloid (QLA) derived from marine fungus was discovered with broad-spectrum anti-IAV activities with low toxicity. Distinct from current anti-IAV drugs, QLA may block virus replication and viral RNA (vRNA) export from the nucleus by targeting virus nucleoprotein (NP). QLA can block the binding of chromosome region maintenance 1 to nuclear export signal 3 of NP to inhibit the nuclear export of NP and vRNP. QLA may also affect vRNP assembly by interfering with the binding of NP to RNA rather than NP oligomerization. Arg305 and Phe488-Gly490 may be required for the interaction between QLA and NP, and the binding pocket around these amino acids may be a promising target for anti-IAV drugs. Importantly, oral administration of QLA can protect the mice against IAV-induced death and weight loss, superior to the effects of the clinical drug oseltamivir. In summary, the marine derived compound QLA has the potential to be developed into a novel anti-IAV agent targeting virus NP protein in the future.

Trends of antimalarial marine natural products: progresses, challenges and opportunities.

Covering 1972 to 2021Malaria remains a significant public health problem in some regions of the world. The great efforts to control malaria have been severely compromised due to the widespread resistance of Plasmodium falciparum to nearly all frontline drugs. Pursuit of novel molecules from the sea will potentially result in new interventions against malaria, which are urgently needed to combat the increase of resistance. Focusing on the strategy of the "Blue Drug Bank", the molecules highlighted here can serve as an inspiration for future medicinal chemistry campaigns. This review covers the developments in the field of antimalarial marine lead compounds reported between 1972 and July 2021, and offers a comprehensive overview on their progresses and potentials. We selected 60 representative potential candidate molecules from 361 marine natural products, and highlighted their structure-activity relationships, molecular mechanisms of targets, and drug-like properties in order to assess their full potential to be developed. We summarized 107 clinically proven or potential antimalarial targets and their subcellular locations in the relevant target proteins, which linked the molecules to the target proteins at the subcellular level. Hence, it could be expected that natural products targeting different mechanisms may prove to be an effective strategy in antimalarial drug research and development in the future.

Integrating Activity-Guided Strategy and Fingerprint Analysis to Target Potent Cytotoxic Brefeldin A from a Fungal Library of the Medicinal Mangrove Acanthus ilicifolius.

Mangrove-associated fungi are rich sources of novel and bioactive compounds. A total of 102 fungal strains were isolated from the medicinal mangrove Acanthus ilicifolius collected from the South China Sea. Eighty-four independent culturable isolates were identified using a combination of morphological characteristics and internal transcribed spacer (ITS) sequence analyses, of which thirty-seven strains were selected for phylogenetic analysis. The identified fungi belonged to 22 genera within seven taxonomic orders of one phyla, of which four genera Verticillium, Neocosmospora, Valsa, and Pyrenochaeta were first isolated from mangroves. The cytotoxic activity of organic extracts from 55 identified fungi was evaluated against human lung cancer cell lines (A-549), human cervical carcinoma cell lines (HeLa), human hepatoma cells (HepG2), and human acute lymphoblastic leukemia cell lines (Jurkat). The crude extracts of 31 fungi (56.4%) displayed strong cytotoxicity at the concentration of 50 µg/mL. Furthermore, the fungus Penicillium sp. (HS-N-27) still showed strong cytotoxic activity at the concentration of 25 µg/mL. Integrating cytotoxic activity-guided strategy and fingerprint analysis, a well-known natural Golgi-disruptor and Arf-GEFs inhibitor, brefeldin A, was isolated from the target active strain HS-N-27. It displayed potential activity against A549, HeLa and HepG2 cell lines with the IC50 values of 101.2, 171.9 and 239.1 nM, respectively. Therefore, combining activity-guided strategy with fingerprint analysis as a discovery tool will be implemented as a systematic strategy for quick discovery of active compounds.

Design, Semisynthesis, Insecticidal and Antibacterial Activities of a Series of Marine-Derived Geodin Derivatives and Their Preliminary Structure-Activity Relationships.

To enhance the biological activity of the natural product geodin (1), isolated from the marine-derived fungus Aspergillus sp., a series of new ether derivatives (2-37) was designed and semisynthesized using a high-yielding one-step reaction. In addition, the insecticidal and antibacterial activities of all geodin congeners were evaluated systematically. Most of these derivatives showed better insecticidal activities against Helicoverpa armigera Hübner than 1. In particular, 15 showed potent insecticidal activity with an IC50 value of 89 µM, comparable to the positive control azadirachtin (IC50 = 70 µM). Additionally, 5, 12, 13, 16, 30 and 33 showed strong antibacterial activity against Staphylococcus aureus and Aeromonas salmonicida with MIC values in the range of 1.15-4.93 µM. The preliminary structure-activity relationships indicated that the introduction of halogenated benzyl especially fluorobenzyl, into 1 and substitution of 4-OH could be key factors in increasing the insecticidal and antibacterial activities of geodin.

Nigrosporins B, a Potential Anti-Cervical Cancer Agent, Induces Apoptosis and Protective Autophagy in Human Cervical Cancer Ca Ski Cells Mediated by PI3K/AKT/mTOR Signaling Pathway.

Nigrosporins B, an anthraquinone derivative obtained from the secondary metabolites of marine fungus Nigrospora oryzae. In this study, we characterized the distinctive anti-cancer potential of Nigrosporins B in vitro and underlying molecular mechanisms in human cervical cancer Ca Ski cells for the first time. The results of MTT assay showed that Nigrosporins B significantly inhibited the proliferation of multiple tumor cells in a dose-dependent manner, especially for the Ca Ski cells with an IC50 of 1.24 µM. Nigrosporins B exerted an apoptosis induction effect on Ca Ski cells as confirmed by flow cytometry, AO/EB dual fluorescence staining, mitochondrial membrane potential analysis and western blot assay. In addition, Nigrosporins B induced obvious autophagy accompanied with the increase of autophagic vacuoles and the acceleration of autophagic flux as indicated by Cyto-ID staining, mRFP-GFP-LC3 adenovirus transfection and western blot analysis. Interestingly, the combination of Nigrosporins B with the three autophagy inhibitors all significantly enhanced the cytotoxicity of Nigrosporins B on Ca Ski cells, indicating that the autophagy induced by Nigrosporins B might protect Ca Ski cells from death. Furthermore, we found that Nigrosporins B inhibited the phosphorylation of PI3K, AKT, mTOR molecules and increased the protein expression levels of PTEN and p-AMPKα in a dose-dependent manner, suggesting that Nigrosporins B induced apoptosis and protective autophagy through the suppression of the PI3K/AKT/mTOR signaling pathway. Together, these findings revealed the anti-cervical cancer effect of Nigrosporins B and the underlying mechanism of action in Ca Ski cells, it might be as a promising alternative therapeutic agent for human cervical cancer.

Brefeldin A delivery nanomicelles in hepatocellular carcinoma therapy: Characterization, cytotoxic evaluation in vitro, and antitumor efficiency in vivo.

Hepatocellular carcinoma (HCC) is one of the major cancers with high mortality rate. Traditional drugs used in clinic are usually limited by the drug resistance and side effect and novel agents are still needed. Macrolide brefeldin A (BFA) is a well-known lead compound in cancer chemotherapy, however, with poor solubility and instability. In this study, to overcome these disadvantages, BFA was encapsulated in mixed nanomicelles based on TPGS and F127 copolymers (M-BFA). M-BFA was conferred high solubility, colloidal stability, and capability of sustained release of intact BFA. In vitro, M-BFA markedly inhibited the proliferation, induced G0/G1 phase arrest, and caspase-dependent apoptosis in human liver carcinoma HepG2 cells. Moreover, M-BFA also induced autophagic cell death via Akt/mTOR and ERK pathways. In HepG2 tumor-bearing xenograft mice, indocyanine green (ICG) as a fluorescent probe loaded in M-BFA distributed to the tumor tissue rapidly, prolonged the blood circulation, and improved the tumor accumulation capacity. More importantly, M-BFA (10 mg/kg) dramatically delayed the tumor progression and induced extensive necrosis of the tumor tissues. Taken together, the present work suggests that M-BFA has promising potential in HCC therapy.

17-Hydroxybrevianamide N and Its N1-Methyl Derivative, Quinazolinones from a Soft-Coral-Derived Aspergillus sp. Fungus: 13S Enantiomers as the True Natural Products.

Under the guidance of MS/MS-based molecular networking and HPLC-UV, two new alkaloid racemates, (±)-17-hydroxybrevianamide N (1) and (±)-N1-methyl-17-hydroxybrevianamide N (2), featuring a rare o-hydroxyphenylalanine residue and an imide subunit, were isolated from a soft-coral-derived Aspergillus sp. fungus. The true natural products (+)-1 and (+)-2 were further monitored and obtained from the freshly prepared EtOAc extracts, while (-)-1 and (-)-2 are artifacts generated during extraction and purification processes. Simultaneously, the structures including absolute configurations of (+)-13S-1, (-)-13R-1, (+)-13S-2, and (-)-13R-2 were elucidated on the basis of comprehensive spectroscopic analysis, ECD calculations, and X-ray diffraction data. Interestingly, basic solution promotes the racemization of (+)-1 and (-)-1, whereas acidic solution suppresses the transformation. The current research was concerned with the true natural products and their artifacts, providing critical insight into the isolation and identification of natural products.

Targeted Isolation of Asperheptatides from a Coral-Derived Fungus Using LC-MS/MS-Based Molecular Networking and Antitubercular Activities of Modified Cinnamate Derivatives.

Under the guidance of MS/MS-based molecular networking, four new cycloheptapeptides, namely, asperheptatides A-D (1-4), were isolated together with three known analogues, asperversiamide A-C (5-7), from the coral-derived fungus Aspergillus versicolor. The planar structures of the two major compounds, asperheptatides A and B (1 and 2), were determined by comprehensive spectroscopic data analysis. The absolute configurations of the amino acid residues were determined by advanced Marfey's method. The two structurally related trace metabolites, asperheptatides C and D (3 and 4), were characterized by ESI-MS/MS fragmentation methods. A series of new derivatives (8-26) of asperversiamide A (5) were semisynthesized. The antitubercular activities of 1, 2, and 5-26 against Mycobacterium tuberculosis H37Ra were also evaluated. Compounds 9, 13, 23, and 24 showed moderate activities with MIC values of 12.5 µM, representing a potential new class of antitubercular agents.

Semisynthesis, Antiplasmodial Activity, and Mechanism of Action Studies of Isocoumarin Derivatives.

In this study, eight natural isocoumarins (1-8) were isolated from a marine-derived Exserohilum sp. fungus. To explore their structure-activity relationship and discover potent antimalarial leads, a small library of 22 new derivatives (1a-1n, 2a, 3a-3c, 4a-4c, and 7a) were semisynthesized by varying the substituents of the aromatic ring and the aliphatic side chains. The natural compound (1) and three semisynthetic derivatives (1d, 1n, and 2a), possessing an all-cis stereochemistry, exhibited strong antiplasmodial activity with IC50 values of 1.1, 0.8, 0.4, and 2.6 µM, respectively. Mechanism studies show that 1n inhibits hemozoin polymerization and decreases the mitochondrial membrane potential but also inhibits P. falciparum DNA gyrase. 1n not only combines different mechanisms of action but also exhibits a high therapeutic index (CC50/IC50 = 675), high selectivity, and a notable drug-like profile.

Semi-Synthesis, Cytotoxic Evaluation, and Structure-Activity Relationships of Brefeldin A Derivatives with Antileukemia Activity.

Brefeldin A (1), a potent cytotoxic natural macrolactone, was produced by the marine fungus Penicillium sp. (HS-N-29) from the medicinal mangrove Acanthus ilicifolius. Series of its ester derivatives 2-16 were designed and semi-synthesized, and their structures were characterized by spectroscopic methods. Their cytotoxic activities were evaluated against human chronic myelogenous leukemia K562 cell line in vitro, and the preliminary structure-activity relationships revealed that the hydroxy group played an important role. Moreover, the monoester derivatives exhibited stronger cytotoxic activity than the diester derivatives. Among them, brefeldin A 7-O-2-chloro-4,5-difluorobenzoate (7) exhibited the strongest inhibitory effect on the proliferation of K562 cells with an IC50 value of 0.84 µM. Further evaluations indicated that 7 induced cell cycle arrest, stimulated cell apoptosis, inhibited phosphorylation of BCR-ABL, and thereby inactivated its downstream AKT signaling pathway. The expression of downstream signaling molecules in the AKT pathway, including mTOR and p70S6K, was also attenuated after 7-treatment in a dose-dependent manner. Furthermore, molecular modeling of 7 docked into 1 binding site of an ARF1-GDP-GEF complex represented well-tolerance. Taken together, 7 had the potential to be served as an effective antileukemia agent or lead compound for further exploration.

Microketides A and B, Polyketides from a Gorgonian-Derived Microsphaeropsis sp. Fungus.

Microketides A and B (1 and 2), a pair of new C-11 epimeric polyketides, were obtained from the gorgonian-derived fungus Microsphaeropsis sp. RA10-14 collected from the South China Sea. The absolute configurations of 1 and 2 were assigned by the modified Mosher's method, TDDFT-ECD, and NMR calculations. Compounds 1 and 2 were evaluated for antibacterial, antifungal, and growth inhibition of marine phytoplankton activities. Microketide A (1) exhibited promising inhibitory activity against Pseudomonas aeruginosa, Nocardia brasiliensis, Kocuria rhizophila, and Bacillus anthraci with the same MIC value as ciprofloxacin (0.19 µg/mL).

The oxygenated products of cryptotanshinone by biotransformation with Cunninghamella elegans exerting anti-neuroinflammatory effects by inhibiting TLR 4-mediated MAPK signaling pathway.

Cryptotanshinone (1), a major bioactive constituent in the traditional Chinese medicinal herb Dan-Shen Salvia miltiorrhiza Bunge, has been reported to possess remarkable pharmacological activities. To improve its bioactivities and physicochemical properties, in the present study, cryptotanshinone (1) was biotransformed with the fungus Cunninghamella elegans AS3.2028. Three oxygenated products (2-4) at C-3 of cryptotanshinone (1) were obtained, among them 2 was a new compound. Their structures were elucidated by comprehensive spectroscopic analysis including HRESIMS, NMR and ECD data. All of the biotransformation products (2-4) were found to inhibit significantly lipopolysaccharide-induced nitric oxide production in BV2 microglia cells with the IC50 values of 0.16-1.16 µM, approximately 2-20 folds stronger than the substrate (1). These biotransformation products also displayed remarkably improved inhibitory effects on the production of inflammatory cytokines (IL-1ß, IL-6, TNF-α, COX-2 and iNOS) in BV-2 cells via targeting TLR4 compared to substrate (1). The underlying mechanism of 2 was elucidated by comparative transcriptome analysis, which suggested that it reduced neuroinflammatory mainly through mitogen-activated protein kinase (MAPK) signaling pathway. Western blotting results revealed that 2 downregulated LPS-induced phosphorylation of JNK, ERK, and p38 in MAPK signaling pathway. These findings provide a basal material for the discovery of candidates in treating Alzheimer's disease.

Annular oxygenation and rearrangement products of cryptotanshinone by biotransformation with marine-derived fungi Cochliobolus lunatus and Aspergillus terreus.

Structural modification of natural products by biotransformation with fungi is an attractive tool to obtain novel bioactive derivatives. In the present study, cryptotanshinone (1), a quinoid abietane diterpene from traditional Chinese medicine Salvia miltiorrhiza (Danshen), was transformed by two marine-derived fungi. By using Cochliobolus lunatus TA26-46, one new oxygenated and rearranged product (2), containing a 5,6-dihydropyrano[4,3-b]chromene moiety, together with one known metabolite (10), were obtained from the converted broth of cryptotanshinone (1) with the isolated yields of 1.0% and 2.1%, respectively. While, under the action of Aspergillus terreus RA2905, seven new transformation products (3-9) as well as 10 with the fragments of 2-methylpropan-1-ol and oxygenated p-benzoquinone were produced and obtained with the isolated yields of 0.1%-1.3%. The structures of the new compounds were elucidated by comprehensive spectroscopic analysis including High Resolution Electrospray Ionization Mass Spectroscopy (HRESIMS), Nuclear Magnetic Resonance (NMR) and Electronic Circular Dichroism (ECD). The metabolic pathways of cryptotanshinone by these two fungi were presumed to be the opening and rearrangement of furan ring, and/or oxygenation of cyclohexane ring. Cryptotanshinone (1) and its metabolites displayed anti-inflammatory activities against NO production in LPS-stimulated BV-2 cells and antibacterial activities towards methicillin-resistant Staphylococcus aureus. These findings revealed the potential of marine fungi to transform the structures of natural products by biotransformation.

Antimicrobial and Antioxidant Polyketides from a Deep-Sea-Derived Fungus Aspergillus versicolor SH0105.

Fifteen polyketides, including four new compounds, isoversiol F (1), decumbenone D (2), palitantin B (7), and 1,3-di-O-methyl-norsolorinic acid (8), along with 11 known compounds (3-6 and 9-15), were isolated from the deep-sea-derived fungus Aspergillus versicolor SH0105. Their structures and absolute configurations were determined by comprehensive spectroscopic data, including 1D and 2D NMR, HRESIMS, and ECD calculations, and it is the first time to determine the absolute configuration of known decumbenone A (6). All of these compounds were evaluated for their antimicrobial activities against four human pathogenic microbes and five fouling bacterial strains. The results indicated that 3,7-dihydroxy-1,9-dimethyldibenzofuran (14) displayed obvious inhibitory activity against Staphylococcus aureus (ATCC 27154) with the MIC value of 13.7 µM. In addition, the antioxidant assays of the isolated compounds revealed that aspermutarubrol/violaceol-I (15) exhibited significant 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity with the IC50 value of 34.1 µM, and displayed strong reduction of Fe3+ with the ferric reducing antioxidant power (FRAP) value of 9.0 mM under the concentration of 3.1 µg/mL, which were more potent than ascorbic acid.

New Thiodiketopiperazine and 3,4-Dihydroisocoumarin Derivatives from the Marine-Derived Fungus Aspergillus terreus.

Aspergillus terreus has been reported to produce many secondary metabolites that exhibit potential bioactivities, such as antibiotic, hypoglycemic, and lipid-lowering activities. In the present study, two new thiodiketopiperazines, emestrins L (1) and M (2), together with five known analogues (3-7), and five known dihydroisocoumarins (8-12), were obtained from the marine-derived fungus Aspergillus terreus RA2905. The structures of the new compounds were elucidated by analysis of the comprehensive spectroscopic data, including high-resolution electrospray ionization mass spectrometry (HRESIMS), one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR), and electronic circular dichroism (ECD) data. This is the first time that the spectroscopic data of compounds 3, 8, and 9 have been reported. Compound 3 displayed antibacterial activity against Pseudomonas aeruginosa (minimum inhibitory concentration (MIC) = 32 µg/mL) and antifungal activity against Candida albicans (MIC = 32 µg/mL). In addition, compound 3 exhibited an inhibitory effect on protein tyrosine phosphatase 1 B (PTP1B), an important hypoglycemic target, with an inhibitory concentration (IC)50 value of 12.25 µM.

Structure-Activity Relationships and Potent Cytotoxic Activities of Terphenyllin Derivatives from a Small Compound Library.

A small library of 120 compounds was established with seventy new alkylated derivatives of the natural product terphenyllin, together with 45 previous reported derivatives and four natural p-terphenyl analogs. The 70 new derivatives were semi-synthesized and evaluated for cytotoxic activities against four cancer cell lines. Interestingly, 2',4''-diethoxyterphenyllin, 2',4,4''-triisopropoxyterphenyllin, and 2',4''-bis(cyclopentyloxy)terphenyllin showed potent activities with IC50 values in a range from 0.13 to 5.51 µM, which were similar to those of the positive control, adriamycin. The preliminary structure-activity relationships indicated that the introduction of alkyl substituents including ethyl, allyl, propargyl, isopropyl, bromopropyl, isopentenyl, cyclopropylmethyl, and cyclopentylmethyl are important for improving the cytotoxicity.