Isolation,structural characterization and neuraminidase inhibitory activities of polyphenolic constituents from Flos caryophylli

Neuraminidase (NA) is one of the key surface proteins of the influenza virus, which is an important target for anti-influenza therapy. In the present study, bioassay-guided fractionation led to isolation of two new compounds, rhamnetin-3-O-β-d-glucuronide-6″-methyl ester (1) and rhamnazin-3-O-β-d-glucuronide-6″-methyl ester (2), along with seventeen known compounds (3-19), from the MeOH extract of Flos Caryophylli using in vitro NA inhibition assay. These isolated compounds exhibited significantly inhibitory effects on the NA with IC₅₀ values ranging from 8.4 to 94.1 μM and were found to protect MDCK cells from A (H1N1) influenza infections (EC₅₀ = 1.5–84.7 μM) with very low cytotoxicity to the host cells (CC₅₀ = 374.3–1266.9 μM)), with selective index (SI) ranging from 7 to 297. The primary structure-relationships of these isolates were also discussed.     

Ellagitannin and flavonoid constituents from Agrimonia pilosa Ledeb. with their protein tyrosine phosphatase and acetylcholinesterase inhibitory activities

A new ellagitannin, agritannin (1), a new flavone glycoside, agriflavone (2), and another flavone glycoside with spectroscopic data reported for the first time, kaempferol-3-O-[(S)-3-hydroxy-3-methylglutaryl (1→6)]-β-d-glucoside (3), along with 16 known compounds were isolated from the aerial parts of Agrimonia pilosa Ledeb. These compounds were evaluated for PTP1B inhibitory activity. Among them, compounds 9 and 18 displayed potential inhibitory activity against PTP1B with IC₅₀ values of 7.14 ± 1.75 and 7.73 ± 0.24 μM, respectively. In addition, compound 1 showed significant inhibitory effect with an IC₅₀ value of 17.03 ± 0.09 μM. Furthermore, these compounds were tested in AChE inhibitory assays. Most of them were found to have moderate inhibitory effects, with IC₅₀ values ranging from 60.20 ± 1.09 to 92.85 ± 1.12 μM. Except compounds 3, 8, and 18 were inactive.     

Aspernolides F and G,new butyrolactones from the endophytic fungus Aspergillus terreus

Two new butyrolactones: aspernolides F (6) and G (7), together with three stigmasterol derivatives: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), and stigmasta-4,6,8(14), 22-tetraen-3-one (3), two meroterpenoids: terretonin A (4) and terretonin (5), and a butyrolactone derivative: butyrolactone VI (8) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were determined by spectroscopic means (1D, 2D NMR, and HRESIMS), as well as optical rotation measurement and comparison with literature data. The isolated compounds were evaluated for their anti-microbial, anti-malarial, anti-leishmanial, and cytotoxic activities. Compound 1 displayed a potent activity against MRSA and C. neoformans with IC₅₀ values of 0.96 μg/mL and 4.38 μg/mL, respectively compared to ciprofloxacin (IC₅₀ 0.07 μg/mL) and amphotericin B (IC₅₀ 0.34 μg/mL), respectively. While, 6 showed good activity against C. neoformans (IC₅₀ 5.19 μg/mL) and mild activity against MRSA (IC₅₀ 6.39 μg/mL). Moreover, 1 and 2 exhibited very good anti-leishmanial activity towards L. donovani with IC₅₀ values of 4.61 and 6.31 μg/mL, respectively and IC₉₀ values of 6.02 and 16.71 μg/mL, respectively.     

Triterpenes from the roots of Lantana montevidensis with antiprotozoal activity

Bioassay guided fractionation of the roots of Lantana montevidensis (Verbenaceae) has resulted in the isolation and identification of three new triterpenoids; 13β-hydroxy-3-oxo-olean-11-en-28-oic acid (1), 12β,13β-dihydroxyolean-3-oxo-28-oic acid (2) and 12β,13β,22β-trihydroxyolean-3-oxo-28-oic acid (3) in addition to nine known compounds: oleanonic acid (4), oleanolic acid (5), 3β,25β-dihydroxy-olean-12-en-28-oic acid (6), lantadene A (7), 19α-hydroxy-3-oxo-olean-12-en-28-oic acid (8) pomolic acid (9), camaric acid (10) together with β-sitosterol (11) and β-sitosterol-3-O-β-d-glucoside (12). The structures of the isolated metabolites were elucidated based on comprehensive 1D and 2D NMR spectroscopic data as well as HR-ESI–MS. The extracts and the isolated metabolites were evaluated for their antiprotozoal and antimicrobial activities. Compound 2 showed antibacterial activity against Staphylococcus aureus and methicillin resistant S. aureus with IC₅₀ values against both organisms of 2.1 μM and compound 10 showed activity against same organisms with IC₅₀ values 8.74 and 8.09 μM, respectively, compared to the positive control ciprofloxacin (IC₅₀ = 0.3 μM against S. aureus and MRSA). Compounds 1, 4, 5, 6, and 10 showed moderate antileishmanial activity with IC₅₀ values ranging between (2.54–14.95 μM) and IC₉₀ values ranging between (11.90–19.47 μM), using pentamidine as a control (IC₅₀ values 2.09 ≥ 16.8 μM) and IC₉₀ values ranging between (4.72 ≥ 16.8 μM). These compounds also showed highly potent antitrypanosomal activity with IC₅₀ values ranging between (0.39–7.12 μM) and IC₉₀ values ranging between (1.91–10.51 μM), which are more efficient than the DFMO, the antitrypanosomal drug employed as positive control (IC₅₀ and IC₉₀values 11.82 and 30.82 μM).     

Tyrosinase inhibitory effects of 1,3-diphenylpropanes from Broussonetia kazinoki

Six 1,3-diphenylpropanes exhibiting inhibitory activities against both the monophenolase and diphenolase actions of tyrosinase were isolated from the methanol (95%) extract of Broussonetia kazinoki. These compounds, 1–6, were identified as kazinol C (1), D (2), F (3), broussonin C (4), kazinol S (5) and kazinol T (6). The latter two species (5 and 6) emerged to be new 1,3-diphenylpropanes which we fully spectroscopically characterized. The IC₅₀ values of compounds (1, 3–5) for monophenolase inhibition were determined to range between 0.43 and 17.9 μM. Compounds 1 and 3–5 also inhibited diphenolase significantly with IC₅₀ values of 22.8, 1.7, 0.57, and 26.9 μM, respectively. All four active tyrosinase inhibitors (1, 3–5) were competitive inhibitors. Interestigly they all mainfested simple reversible slow-binding inhibition against diphenolase. The most potent inhibitor, compound 4 diplayed the following kinetic parameters k₃ = 0.0993 μM^?1 min^?1, k₄ = 0.0048 min^-1, and K_i^app = 0.0485 μM.     

Comparing anti-HIV,antibacterial, antifungal,micellar, and cytotoxic properties of tricarboxylato dendritic amphiphiles

Three series of homologous dendritic amphiphiles—RCONHC(CH₂CH₂COOH)₃, 1(n); ROCONHC(CH₂CH₂COOH)₃, 2(n); RNHCONHC(CH₂CH₂COOH)₃, 3(n), where R = n-C_nH_2n+1 and n = 13–22 carbon atoms—were assayed for their potential to serve as antimicrobial components in a topical vaginal formulation. Comparing epithelial cytotoxicities to the ability of these homologues to inhibit HIV, Neisseria gonorrhoeae, and Candida albicans provided a measure of their prophylactic/therapeutic potential. Measurements of the ability to inhibit Lactobacillus plantarum, a beneficial bacterium in the vagina, and critical micelle concentrations (CMCs), an indicator of the potential detergency of these amphiphiles, provided additional assessments of safety. Several amphiphiles from each homologous series had modest anti-HIV activity (EC₅₀ = 110–130 μM). Amphiphile 2(18) had the best anti-Neisseria activity (MIC = 65 μM), while 1(19) and 1(21) had MICs against C. albicans of 16 and 7.7 μM, respectively. Two measures of safety showed promise as all compounds had relatively low cytotoxic activity (EC₅₀ = 210–940 μM) against epithelial cells and low activity against L. plantarum, 1(n), 2(n), and 3(n) had MICs ? 490, 1300, and 940 μM, respectively. CMCs measured in aqueous triethanolamine and in aqueous potassium hydroxide showed linear dependences on chain length. As expected, the longest chain in each series had the lowest CMC—in triethanolamine: 1(21), 1500 μM; 2(22), 320 μM; 3(22), 340 μM, and in potassium hydroxide: 1(21), 130 μM; 3(22), 40 μM. The CMC in triethanolamine adjusted to pH 7.4 was 400 μM for 1(21) and 3900 μM for 3(16). The promising antifungal activity, low activity against L. plantarum, relatively high CMCs, and modest epithelial cytotoxicity in addition to their anti-Neisseria properties warrant further design studies with dendritic amphiphiles to improve their safety indices to produce suitable candidates for antimicrobial vaginal products.     

Xanthine oxidase inhibitory terpenoids of Amentotaxus formosana protect cisplatin-induced cell death by reducing reactive oxygen species (ROS) in normal human urothelial and bladder cancer cells

The diterpenoids (+)-ferruginol (1), ent-kaur-16-en-15-one (2), ent-8(14),15-sandaracopimaradiene-2α,18-diol (3), 8(14),15-sandaracopimaradiene-2α,18,19-triol (4), and (+)-sugiol (5) and the triterpenoids 3β-methoxycycloartan-24(24¹)-ene (6), 3β,23β-dimethoxycycloartan-24(24¹)-ene (7), 3β,23β-dimethoxy-5α-lanosta-24(24¹)-ene (8), and 23(S)-23-methoxy-24-methylenelanosta-8-en-3-one (9), isolated from Amentotaxus formosana, showed inhibitory effects on xanthine oxidase (XO). Of the compounds tested, compound 5 was a potent inhibitor of XO activity, with an IC₅₀ value of 6.8 ± 0.4 μM, while displaying weak ABTS radical cation scavenging activity. Treatment of the bladder cancer cell line, NTUB1, with 3–10 μM of compound 5 and 10 μM cisplatin, and immortalized normal human urothelial cell line, SV-HUC1, with 0.3–1 μM and 10–50 μM of compound 5 and 10 μM cisplatin, respectively, resulted in increased viability of cells compared with cytotoxicity induced by cisplatin. Treatment of NTUB1 with 20 μM cisplatin and 10 or 30 μM of compound 5 resulted in decreased ROS production compared with ROS production induced by cisplatin. These results indicate that 10 or 30 μM of compound 5 in NTUB1 cells may mediate through the suppression of XO activity and reduction of reactive oxygen species (ROS) induced by compound 5 cotreated with 20 μM cisplatin and protection of subsequent cell death.     

Isolation of antiplasmodial anthraquinones from Kniphofia ensifolia,and synthesis and structure–activity relationships of related compounds

Bioassay-guided separation of the South African plant Kniphofia ensifolia for antiplasmodial activity led to the isolation of two new anthraquinones, named kniphofiones A and B (3 and 4), together with three known bioactive anthraquinone monomers (1, 2 and 5), and four known bisanthraquinones (6–9). The structures of the two new compounds were elucidated based on analyses of their 1D and 2D NMR spectra and mass spectrometric data. The dimeric compounds 6 and 7 displayed the strongest antiplasmodial activity among all the isolated compounds, with IC₅₀ values of 0.4 ± 0.1 and 0.2 ± 0.1 μM, respectively. The two new compounds displayed modest activities, with IC₅₀ values of 26 ± 4 and 9 ± 1 μM, respectively. Due to the synthetic accessibility of the new compounds and the increased activity shown by the dimeric compounds, a structure–activity relationship study was conducted. As a result, one analogue of kniphofione B (4), the caffeic acid derivative of aloe-emodin, was found to have the highest activity among all the aloe-emodin derivatives, with an IC₅₀ value of 1.3 ± 0.2 μM.     

Two polymethoxylated flavonoids with antioxidant activities and a rearranged clerodane diterpenoid from the leaf exudates of Microglossa pyrifolia

Three novel compounds; two polymethoxylated flavonoids, 5,7,4′-trihydroxy-3,8,3′,5′-tetramethoxyflavone (1), 5,7,3′-trihydroxy-3,8,4′,5′-trimethoxyflavone (2), and a clerodane diterpenoid; 8-acetoxyisochiliolide lactone (3) were characterized from the leaf exudates of Microglossa pyrifolia. In addition, three known polymethoxylated flavonoids including; 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone (4), 5,3′4′-trihydroxy-3,7,8-trimethoxyflavone (5), 5,3′4′-trihydroxy-7-methoxyflavanone (6) and a clerodane diterpenoid; 7,8-epoxyisocholiolide lactone (7) were identified. Their structures were determined on the basis of spectroscopic evidence. All the compounds did not exhibit antiplasmodial and antimicrobial activities at 47.6 μg/mL and were not cytotoxic at 5 μg/mL. Compound 6 exhibited modest antileishmanial activity with IC₅₀ value of 13.13 μg/mL with 5 and 7 showing activities with IC₅₀ values of 31.13 and 38.00 μg/mL, respectively, therefore inactive. The flavonoids (quercetin derivatives, 4 and 5) showed similar antioxidant activities, using 2,2-diphenylpicrylhydrazyl (DPPH) assay, with IC₅₀ values of 6.2 ± 0.3 μg/mL for 4 (17.3 μM) and 5 (17.8 μM) respectively. These activities were comparable to that of the standard quercetin (IC₅₀ value of 6.0 ± 0.2 μg/mL (19.9 μM)), irrespective of methylation of the characteristic hydroxyl groups expected to be responsible for activity and additional substitution at C-8 in ring A of the flavonoid ring. These studies revealed that the presence of an hydroxyl group at C-4′ positions and oxygenation at C-3 in flavone skeleton, appears to be necessary for good antioxidant activities as encountered in compounds 1, 4 and 5. Substantial reduction in antioxidant activity was shown by methoxylation of the 4′-OH as observed in compound 2 with an IC₅₀ value of 8.79 ± 0.3 μg/mL (24.4 μM).     

Acylated iridoid glycosides and acylated rhamnopyranoses from Gmelina arborea flowers

Nine acylated iridoid glycosides (1–9), five acylated rhamnopyranoses (10–14) and verbascoside (15) were isolated from Gmelina arborea flowers, including 5 new compounds (1, 2, and 10–12). The cytoprotective activity of 11 selected compounds (1–8, 10, 11, and 15) against CCl₄-induced cytotoxicity on liver was determined. Compounds 1, 2, 4, 7, 8 and 15 displayed hepatoprotective activity. 6-O-α-l-(2″, 3″-di-O-trans-p-hydroxycinnamoyl)rhamnopyranosylcatalpol (2) exhibited the most potent cytoprotective effect with an EC₅₀ value of 42.5 μM (SI = 19.3) compared with biphenyldimethylesterate (DDB, EC₅₀ = 277.3 μM, SI = 9.8) and bicylo-ethanol (EC₅₀ = 279.2 μM, SI = 12.2). Among the acylated iridoid glycosides, the compounds (2 and 8) containing phenolic hydroxy groups were more active than were those lacking them.     

Cytotoxic glucosydic iridoids from Veronica americana

Fractionation guided by the cytotoxic activity of the methanolic extract of Veronica americana led to the isolation of two new iridoids identified as 4β-hydroxy-6-O-(p-hydroxybenzoyl)-tetrahydrolinaride (1) and 10-O-protocatechuyl-catalpol (2), together with four known aromatic acids, veratric acid (3) p-methoxybenzoic acid (4), p-hydroxybenzoic acid (5) and protocatechuic acid (6). The structure of these compounds was determined by spectroscopic analysis. Iridoid glycosides 1 and 2 showed selective cytotoxic activity against the human cancer cell lines HF-6 (IC₅₀ = 0.031 and 0.066 μM, respectively) and PC-3 (IC₅₀ = 0.721 and 0.801 μM, respectively), with less sensitivity in normal MRC-5 cells (IC₅₀ = 77.103 and 1451.562 μM, respectively). Compound 1 was 9.9 times more potent than camptothecin against HF-6 cell line, while compound 2 was 4.7 times, more potent, against the same cell line, than camptothecin. The found biological efficacy of 1 and 2 allow us to propose these compounds as candidates for the development of effective anticancer therapeutic agents.     

Acridone alkaloids from Vepris verdoorniana (Excell & Mendonça) Mziray (Rutaceae)

Two new acridone alkaloids, verdoocridone A (1) and B (4), together with fifteen known compounds were isolated from methanol extracts of the roots and leaves of Vepris verdoorniana. The structures of all compounds were determined by comprehensive spectroscopic analyses (1D and 2D NMR, EI- and ESI–MS). The ¹³C NMR values of 1,2,3,5-tetramethoxy-N-methylacridone (2) and 5-methoxyaborinine (3) are also reported. The crude extracts and compounds (1-6) were tested for their antimicrobial activity. The test delivered moderate activities for crude extracts and compounds 1, 5 and 6 against the bacterium Staphylococcus aureus and the fungi Mucor meihei and Candida albicans with MIC values between 115 and 180 μg/mL for extracts and between 21.3 and 29.4 μM for compounds, compared to gentamycin with 0.2 μM and nystatin with 5.2 μM against both fungi. The determination of the radical scanvenging activity using 1,1-dephenyl-2-picrylhydrazyl (DPPH) assay gave moderate antioxidant values for all tested compounds, with IC₅₀ between 0.29 and 0.41 μM, compared to the standard 3-t-butyl-4-hydroxyanisole (BHA) displaying 0.03 μM.     

Prenylated C6–C3 compounds from the roots of Illicium henryi

Eleven prenylated C₆–C₃ compounds, illihenryifunones A, B (1, 2), illihenryifunol A (3), illihenryipyranol A (4), illihenryiones A−G (5–11), and three known prenylated C₆–C₃ compounds (12–14), were isolated from the roots of Illicium henryi. Structures of 1–11 were elucidated by spectroscopic methods including NMR, HRESIMS, and CD. The absolute configuration of the 11,12-diol moiety in 5 was determined by observing its induced circular dichroism after addition of Mo₂(OAc)₄ in DMSO. The absolute configuration of C-11 in 4 was determined as S based on the Rh₂(OCOCF₃)₄-induced CD data; the absolute configuration of 3 was determined as R by comparison of its experimental and calculated electronic circular dichroism (ECD). The antioxidant activities of compounds 1–14 were also evaluated. Compound 4 exhibited strong antioxidant activity with an IC₅₀ value of 2.97 ± 1.30 μM, whereas compounds 3 and 8 showed antioxidant activities with IC₅₀ values of 44.36 ± 0.30 and 48.00 ± 2.01 μM, respectively.     

Pentacyclic hemiacetal sterol with antifouling and cytotoxic activities from the soft coral Nephthea sp.

A novel unusual pentacyclic hemiacetal sterol nephthoacetal (1), was isolated from soft coral Nephthea sp. The structure of this sterol was inferred from its two acetyl derivatives (2) and (3), by means of spectroscopic methods, and quantum chemical calculations. Anti-fouling activity of compounds 1–3 against Bugula neritina larvae was evaluated, sterol (1) exhibited significant inhibitory effect with EC₅₀ value of 2.5 μg/mL, while having low toxicity with LC₅₀ >25.0 μg/mL. The in vitro cytotoxic activity of compounds 1–3 against HeLa cells was also evaluated, all of them exhibited moderate cytotoxicity with IC₅₀ values of 12.3 (1), 10.1 (2), and 19.6 μg/mL (3), respectively.     

β-Secretase (BACE1)-inhibiting C-methylrotenoids from Abronia nana suspension cultures

Suspension cultures of Abronia nana were established to produce C-methylisoflavones. A new C-methylrotenoid, named abronione A (2), was isolated along with three known rotenoids, boeravinone D (1), boeravinone A methyl ether (3), and mirabijalone D (4). The IC₅₀ values of compounds 1, 2, and 4 on β-secretase (BACE1) were 4.77, 62.21, and 4.24 μM, respectively, whereas 3 was inactive. At concentrations up to 1.0 mM, the compounds did not inhibit other proteases such as trypsin, chymotrypsin, and elastase, indicating that they were specific inhibitors of β-secretase. Compounds 1 and 4 were non-competitive inhibitors based on the Dixon plot and with K_i values of 5.01 and 4.28 μM, respectively. At 50 μM, compound 4 inhibited Aβ_1–42 production by 43.7% in APP_SW-N2a cells.     

Three new geranyl aurones from the leaves of Artocarpus altilis

From the MeOH extract of the leaves of Artocarpus altilis (Moraceae), three new aurones, altilisin H (1), I (2), and J (3), have been isolated together with two known flavonoids. Their structures were elucidated on the basis of spectroscopic data. All compounds possessed tyrosinase inhibitory activity with IC₅₀ values less than 100 μM, while compounds 1–3 displayed potent α-glucosidase inhibitory activity with IC₅₀ values ranging from 4.9 to 5.4 μM.     

Two new rotenoids from the roots of Millettia speciosa

Two new rotenoids, named millettiaosas A–B (1–2), together with four known compounds were isolated from the roots of Millettia speciosa. Their structures were elucidated on the basis of spectroscopic analysis including 1D and 2D NMR techniques and HRESIMS. Evaluation of the two new compounds for cytotoxicity against four human cancer cell lines (MCF-7, HCT-116, A549 and HepG-2) showed moderate activities (10 μM < IC₅₀ < 26 μM).     

Tirucallane triterpenoids from the stem bark of Araliopsis synopsis

Two new tirucallane triterpenoids, 21-methoxy-21,23-epoxy-tirucalla-7,24-dien-3α-ol (1) and 21-methoxy-21,23-epoxy-tirucalla-7,24-diene-1α,3α-diol (2), together with thirteen known compounds were isolated from the CH₂Cl₂ extract of the stem bark of Araliopsis synopsis. The structures of the compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data and comparison with previously known analogs. Compounds 1–10 were tested against bacteria, fungi and plant pathogen oomycetes by the paper disk agar diffusion assay resulting in missing to low activities corresponding with MICs > 1 mg/mL. However, compounds 5–10 exhibited high cytotoxic activity against the human Caucasian prostate adenocarcinoma cell PC-3 line, with IC₅₀ 8.5–12.5 μM compared to the standard Doxorubicin with IC₅₀ = 0.9 μM, while compounds 1, 3 and 4 showed low activity.     

Bioactive 2-pyrone metabolites from an endophytic Phomopsis asparagi SWUKJ5.2020 of Kadsura angustifolia

Five new 2-pyrone metabolites, phomaspyrones A–E (1–5) along with three known compounds, macommelin-8,9-diol (6), macommelin-9-ol (7), and macommelin (8), were isolated from the culture broth of an endophytic fungus Phomopsis asparagi SWUKJ5.2020 of medicinal plant Kadsura angustifolia by sequentially purification over silica gel, Sephadex LH-20 column chromatography and preparative HPLC. Their structures were elucidated on the basis of spectroscopic analysis, including two-dimensional (2D) NMR and HRMS (ESI-TOF) data. Among them, compounds 3–5 exhibited notable cytotoxicity against HL-60 and K562 cells with IC₅₀ values of below 10 μg/mL better than those of the other isolated metabolites (IC₅₀ = 10.6–26.6 μg/mL). The results showed that the keto or hemiketal functionality might play an important role in cytotoxic activity of this class of compounds.     

In vitro cytotoxic activity of isolated acridones alkaloids from Zanthoxylum leprieurii Guill. et Perr

Chemical investigation of the roots and fruits of Zanthoxylum leprieurii Guill. et Perr. led to the isolation of three new alkaloids including two acridone derivatives, 3-hydroxy-1,4-dimethoxy-10-methyl-9-acridone (2) and 3-hydroxy-1,2-dimethoxy-10-methyl-9-acridone (3) named helebelicine A and B, respectively, and one secobenzo[c]phenantridine, 10-O-demethyl-12-O-methylarnottianamide (10), together with thirteen other compounds. The structures of compounds 2, 3 and 10 as well as those of the known compounds were elucidated by using spectroscopic methods and by comparison with reported data. The brine-shrimp (artemia salina) lethality bioassay of the chloroform extract of the fruits showed modest cytotoxicity with LD₅₀ at 13.1 μg/mL. Isolated compounds 1, 4–6 were found to be moderately active against lung carcinoma cells (A549), colorectal adenocarcinoma cells (DLD-1) and normal cells (WS1) with IC₅₀ values ranging from 27 to 77 μM. In contrast to the positive control etoposide used, the cytotoxicity of the most active compound 4 was found to be selective against cancer cells in comparison to normal cells WS1 with IC₅₀ of 51 ± 8 μM and 4.3 ± 0.4 μM, respectively.