Two new 8-O-4′-type lignans from the stem of Schima superba and their cell growth inhibitory activities against human cancer cell lines

Two new lignans (1 and 2) were isolated from the EtOH extracts of the stem of Schima superba, and elucidated as (7R,8S)-1-(3,4-dimethoxyphenyl)-2-O-(2-methoxy-4-omegahydroxypropylphenyl)propane-1,3-diol (1) and threo-1-(4-hydroxy-3-methoxyphenyl)-1-methoxy-2-{4-[1-formyl-(E)-vinyl]-2-methoxyphenoxy}-3-propanol (2) by spectral analysis. Compounds 1 and 2 showed cell growth inhibitory activity against HeLa, CNE, HepG-2, and HEp-2 cell lines. Compound 1 exhibited significant cytotoxicities with IC₅₀ values of less than 4 μg/ml against all the tested cell lines.     

Effect of β-cyclodextrin encapsulation on cytotoxic activity of acetylshikonin against HCT-116 and MDA-MB-231 cancer cell lines

Acetylshikonin (AcSh), as a red colored pigment found in roots of the plants from family Boraginaceae, showed excellent cytotoxic activity. Due to its hydrophobic nature, and thus poor bioavailability, the aim of this study was to prepare acetylshikonin/β-cyclodextrin (AcSh/β-CD) inclusion complex by using coprecipitation method, characterize obtained system by using UV/VIS, IR and ¹H NMR spectroscopy, and determine cytotoxic activity. Phase solubility test indicated formation of A_L-type binary system (substrate/ligand ratio was 1:1 M/M), with stability constant Ks of 306.01 M⁻¹. Formation of noncovalent bonds between inner layer of the hole of β-CD and AcSh was observed using spectroscopic methods. Notable changes in chemical shifts of two protons (−0.020 ppm) from naphthoquinone moiety (C₆-H and C₇-H), as well as protons from hydroxyl groups (−0.013 and −0.009, respectively) attached to C₅ and C₈ carbons from naphthoquinone part indicate that the molecule of AcSh enters the β-CD cavity from the aromatic side. Cytotoxic activity against HCT-116 and MDA-MB-231 cell lines was measured by MTT test and clonogenic assay. Mechanisms of action of free AcSh and inclusion complex were assessed by flow cytometry. In comparison to free AcSh, AcSh/β-CD showed stronger short-term effect on HCT-116 cells and superior long-term effect on both cell lines. Inclusion complex induced more pronounced cell cycle arrest and autophagy inhibition, and induced increase in accumulation of intracellular ROS more effectively than free AcSh. In conclusion, AcSh/β-CD binary system showed better performances regarding cytotoxic activity against tested tumor cell lines.     

Synergistic,cytotoxic and apoptotic activities of olmesartan with NF-κB inhibitor against HeLa human cell line

Abstract

Context: Over expression of renin–angiotensin system (RAS) and nuclear factor-kappaB (NF-κB) has a major role in many cancers. It has been suggested that some angiotensin receptor blockers (ARBs) could reduce the proliferation of cancer cells. The role of NF-κB pathway has been documented in cell proliferation.

Objective: In this study, the role of angiotensin II and NF-κB pathway in human cervical cancer cell line (HeLa) proliferation was studied using olmesartan (as a novel Ag II antagonist) and Bay11-7082 (as NF-κB inhibitor).

Materials and methods: HeLa cells were treated with different concentrations of olmesartan and Bay11-7082. Cell proliferation was determined after 24, 48, and 72?h by MTT assay. Synergistic activity of olmesartan with Bay11-7082 was analyzed with Compusyn software. Apoptotic cells were determined using PI staining of DNA fragmentation.

Results: Cell viability decreased with olmesartan and Bay11-7082 in HeLa cells by 24, 48 and 72?h. Olmesartan had synergistic activity with Bay11-7082 and combinations of olmesartan with Bay11-7082 decreased cell viability as compared with single agent treatments. Olmesartan and Bay11-7082 induced a sub-G1 peak in flow cytometry histogram of treated cells indicating that apoptotic cell death is involved in olmesartan and Bay11-7082-induced toxicity.

Discussion and conclusion: Results imply that olmesartan and Bay11-7082 inhibit the growth of HeLa cells as a concentration- and time-dependent mode and they have synergistic activity. Results show that RAS and NF-κB pathway blockade lead to significant cytotoxicity against tumor cell line. So, ARBs and NF-κB pathway inhibitors could be considered as good anti-cancer agents in cervix carcinoma after further studies.     

Antitumor activity of a novel series of α-aryloxy-α-methylhydrocinnamic acid derivatives as PPAR gamma agonists against a panel of human cancer cell lines

Summary  Peroxisome proliferator-activated receptor gamma (PPARγ) agonists have shown benefit in treating diabetes mellitus, atherosclerosis and cancer. However, widespread use of thiazolidinediones (TZDs), the clinically used synthetic PPARγ agonists, has been limited by adverse cardiovascular effects. Consequently, numerous novel non-TZD compounds were synthesized and antidiabetic efficacy was evaluated to identify PPARγ agonists for potential clinical use. On the other hand, many studies have documented that the antitumor activity of PPARγ agonists is PPARγ independent. Here we hypothesized that there might exist some compounds with less PPARγ agonistic activity or antidiabetic efficacy but potent antitumor activity. In this study, we evaluated the PPARγ agonistic and antitumor activity of several newly synthesized α-aryloxy-α-methylhydrocinnamic acid derivatives as PPARγ agonists in a panel of human cancer cell lines, which showed promising antitumor activity without appreciable PPARγ agonistic activity. The results of MTT assay revealed that cell viability was inhibited in a dose dependent manner with IC₅₀ 17.1–55.1 μM for all the novel compounds and rosiglitazone (17.2–165 μM). They induced cell cycle arrest and apoptosis tested by Flow Cytometry. In conclusion, our findings demonstrate that these compounds have potent in vitro cytotoxicity, the possible mechanism of which is through induction of apoptosis and cell cycle arrest Xishan Xiong and Yangliang Ye contributed equally to this work.     

Establishment of stable cell lines with high expression of heterodimers of human 4F2hc and human amino acid transporter LAT1 or LAT2 and delineation of their differential interaction with α-alkyl moieties

System L is a major transport system for cellular uptake of neutral amino acids. Among system L transporters, L-type amino acid transporter 1 (LAT1) is responsible for the nutrient uptake in cancer cells, whereas L-type amino acid transporter 2 (LAT2) is a transporter for non-cancer cells. In this study, we have established HEK293 cell lines stably expressing high levels of human LAT1 and LAT2 forming heterodimers with native human 4F2hc of the cells. We have found that L-[(14)C]alanine is an appropriate substrate to examine the function of LAT2, whereas L-[(14)C]leucine is used for LAT1. By using L-[(14)C]alanine on LAT2, we have for the first time directly evaluated the function of human LAT2 expressed in mammalian cells and obtained its reliable kinetics. Using α-alkyl amino acids including α-methyl-alanine and α-ethyl-L-alanine, we have demonstrated that α-alkyl groups interfere with the interaction with LAT2. These cell lines with higher practical advantages would be useful for screening and analyzing compounds to develop LAT1-specific drugs that can be used for cancer diagnosis and therapeutics. The strategy that we took to establish the cell lines would also be applicable to the other heterodimeric transporters with important therapeutic implications.     

Effects of anthocyanins on the AhR–CYP1A1 signaling pathway in human hepatocytes and human cancer cell lines

Anthocyanins are plant pigments occurring in flowers and berry fruits. Since a phenomenon of food–drug interactions is increasingly emerging, we examined the effects of 21 major anthocyanins and the extracts from 3 food supplements containing anthocyanins on the aryl hydrocarbon receptor (AhR)–cytochrome P450 CYP1A1 signaling pathway in human hepatocytes and human hepatic HepG2 and intestinal LS174T cancer cells. Pelargonidin-3-O-rutinoside (PEL-2) and cyanidin-3,5-O-diglucoside (CYA-3) dose-dependently activated AhR, as revealed by gene reporter assay. PEL-2 and CYA-3 induced CYP1A1 mRNA but not protein in HepG2 and LS174T cells. Neither compounds induced CYP1A1 mRNA and protein in four different primary human hepatocytes cultures. The effects of PEL-2 and CYA-3 on AhR occurred by ligand-dependent and ligand-independent mechanisms, respectively, as demonstrated by ligand binding assay. In a direct enzyme inhibition assay, none of the antocyanins tested inhibited the CYP1A1 marker activity to less than 50% even at 100 μM concentration. PEL-2 and CYA-3 at 100 μM inhibited CYP1A1 to 79% and 65%, respectively. In conclusion, with exception of PEL-2 and CYA-3, there were no effects of 19 major anthocyanins and 3 food supplements containing anthocyanins on AhR–CYP1A1 signaling, implying zero potential of these compounds for food–drug interactions with respect to AhR–CYP1A1 pathway.     

Ouabain impairs cancer metabolism and activates AMPK-Src signaling pathway in human cancer cell lines

In addition to the well-known cardiotonic effects,cardiac glycosides(CGs)produce potent anticancer effects with various molecular mechanisms.We previously show that ouabain induces autophagic cell death in human lung cancer cells by regulating AMPK-mediated mTOR and Src-mediated ERK1/2 signaling pathways.However,whether and how AMPK and Src signaling interacts in ouabain-treated cancer cells remains unclear.Given the pivotal role of AMPK in metabolism,whether ouabain affects cancer cell metabolism remains elusive.In this study we showed that treatment with ouabain(25 nM)caused simultaneous activation of AMPK and Src signaling pathways in human lung cancer A549 cells and human breast cancer MCF7 cells.Cotreatment with AMPK inhibitor compound C or siRNA greatly abrogates ouabain-induced Src activation,whereas cotreatment with Src inhibitor PP2 has little effect on ouabain-induced AMPK activity,suggesting that AMPK served as an upstream regulator of the Src signaling pathway.On the other hand,ouabain treatment greatly depletes ATP production in A549 and MCF7 cells,and supplement of ATP(100μM)blocked ouabain-induced AMPK activation.We further demonstrated that ouabain greatly inhibited the mitochondrial oxidative phosphorylation(OXPHOS)in the cancer cells,and exerted differential metabolic effects on glycolysis depending on cancer cell type.Taken together,this study reveals that the altered cancer cell metabolism caused by ouabain may contribute to AMPK activation,as well as its cytotoxicity towards cancer cells.     

The first total syntheses of (±)-norphoebine,dehydrophoebine, oxophoebine,dehydrocrebanine, oxocrebanine and uthongine and their cytotoxicity against three human cancer cell lines

The first total syntheses of (±)-norphoebine, dehydrophoebine, oxophoebine, dehydrocrebanine, oxocrebanine and uthongine have been achieved. The crucial step involved the formation of ring C by a microwave-assisted direct biaryl coupling to produce the aporphine skeleton in high yields. The synthetic alkaloids were evaluated for their cytotoxicity against three human cancer cell lines MCF7, KB and NCI-H187. The results showed that uthongine was the best candidate of the series and it exhibited cytotoxicity against a human breast cancer MCF7 line with an IC₅₀ = 3.05 μM     

Preparation and characterization of Δ9-tetrahydrocannabinol-loaded biodegradable polymeric microparticles and their antitumoral efficacy on cancer cell lines

Abstract

Cannabinoids present an interesting therapeutic potential as antiemetics, appetite stimulants in debilitating diseases (cancer, AIDS and multiple sclerosis), analgesics, and in the treatment of multiple sclerosis and cancer, among other conditions. However, despite their high clinical potential, only few dosage forms are available to date.

In this paper, the development of Δ⁹-tetrahydrocannabinol (THC) biodegradable microspheres as an alternative delivery system for cannabinoid parenteral administration is proposed. Tetrahydrocannabinol was encapsulated into biodegradable microspheres by the oil-in-water (o/w) emulsion solvent evaporation method. Several formulations were prepared using different drug:polymer ratios. The influence of antioxidant (α-tocopherol acetate) concentration on the release of THC from the microparticles was studied. Elevated process yield and entrapment efficiencies were achieved. The in vitro drug release studies showed that the encapsulated drug was released over a two week period. As THC has shown therapeutic potential as anticancer drug, the efficacy of the microspheres was tested on different cancer cell lines. Interestingly, the microspheres were able to inhibit cancer cell proliferation during the nine-day study period. All the above results suggest that the use of biodegradable microspheres would be a suitable alternative delivery system for THC administration.     

Design,synthesis of new chiral fluorine-containing β-hydroxysulfonamides from natural amino acids and study of their anti-inflammatory and analgesic activities

A series of new chiral fluorine-containing β-hydroxysulfonamides were conveniently synthesized in three steps, starting from natural L-amino acids, and evaluated for their anti-inflammatory and analgesic activities. The structures of these compounds were supported by FT-IR, ¹H, ¹³C and ¹⁹F NMR, elemental analysis and HRMS. Among the tested compounds, 4c, 4g and 4h exhibited promising anti-inflammatory activity. Moreover, compound 4h showed a significant analgesic activity. The structure–activity relationships of selected compounds were discussed.     

Synthesis,biosynthesis and biological activities of galbanic acid – A review

Context: Galbanic acid (GA) is a biologically active sesquiterpene coumarin from Ferula species (Apiaceae). This compound showed various biological properties including anticancer, cancer chemopreventive, anticoagulant, antiviral, and antileishmanial activities.

Objectives: This article is a review on the synthesis, biosynthesis, and biological activities of GA. In addition, we discussed gaps in our knowledge about GA that deserve future research. In this article, we also evaluated the drug-likeness of GA in silico.

Methods: All relevant databases were searched for the terms “galbanic acid”, “methyl galbanate”, “Ferula” and “sesquiterpene coumarin” without limitation, up to May 2013. Information on GA was collected via electronic search using Pubmed, Scopus, Web of Science, and Sciencedirect. All physicochemical parameters used for the prediction of drug-likeness were calculated using MarvinSketch (version 5.11, academic package, ChemAxon).

Results: This compound showed various biological properties including anticancer, cancer chemopreventive, anticoagulant, antiviral and antileishmanial activities. GA can inhibit the growth of prostate cancer cells via decreasing androgen receptor abundance. In silico physicochemical studies on GA showed that this compound has drug-like properties, the parameters that are important to predict potential of a compound for being a future drug.

Conclusion: GA is a valuable natural product with various biological activities. New discoveries with GA are to be expected.     

Anticancer and apoptotic activity of biologically synthesized zinc oxide nanoparticles against human colon cancer HCT-116 cell line- in vitro study

Aim of this study was to synthesize the safe and stable zinc oxide nanoparticles (ZnONPs) from the leaves of Artocarpus heterophyllus. The alter in the color of the leaf extract dark brown upon addition of zinc nitrate Zn(NO₃) confirms the formation of Zinc Oxide nanoparticles (ZnONPs). UV-VIS spectrophotometric analysis showed lambda max at 235 nm while Fourier transform infra-red (FTIR) spectroscopy showed various amines and amides are involved in the stabilization of ZnONPs. Energy dispersive X –rays (EDX) confirms the presence of zinc. Transmission electron microscopy (TEM) analysis revealed particle size ranges from 12 to 24 nm. These observed characteristic of nanoparticles are extremely useful in anticancer activities against HCT-116 colon cancer cell line. These ZnONPs showed IC50 value at 20μg/ml while on normal Vero cell line showed less effective by MTT assay. Furthermore, these nanoparticles were evaluated for apoptotic activity by acridine orange/ethidium bromide (AO/EB) double staining method showed the membrane blebbing and chromatin condensation.     

Antiproliferative effects of novel urea derivatives against human prostate and lung cancer cells; and their inhibition of β-glucuronidase activity

Twenty-one novel urea derivatives were synthesized and their structures characterized by mass, NMR, IR, and UV spectroscopy. These compounds were evaluated for their antiproliferative profile against human PC-3 (prostate) and NCI-H460 (lung) cancer cell lines. Among them, compound 21 N-(3-nitrophenyl)-N′-(1-phenylethyl)urea was found to be active against both PC-3 (IC₅₀ ± SEM: 20.13 ± 0.91 μM) and NCI-H460 (GI₅₀: 22 ± 2.6 μM) cell lines; hence has the potential to be further studied as anticancer agent. These compounds were also investigated for their ability to inhibit urease, β-glucuronidase, and phosphodiesterase enzymes. N-(2,6-Dimethylphenyl)-N′-(4′-nitrophenyl)urea (1) demonstrated 90 % inhibition of β-glucuronidase enzyme (IC₅₀ ± SEM: 3.38 ± 0.043 μM).     

Synthesis,antibacterial and antifungal activities of naphthoquinone derivatives: a structure–activity relationship study

The synthesis of 1,4-naphthoquinone derivatives is of great interest since these compounds exhibit strong activity as antimalarial, antibacterial, antifungal and anticancer agents. A series of 50 naphthoquinone derivatives was synthesized and evaluated for antibacterial and antifungal activity against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, Candida krusei, Candida parapsilosis and Cryptococcus neoformans using the broth microdilution method. The Candida species were the most susceptible microorganisms. Halogen derivatives of 1,4-naphthoquinone presented strong activity, e.g., 2-bromo-5-hydroxy-1,4-naphthoquinone, which exhibited inhibition at an MIC of 16 µg/mL in S. aureus, and 2-chloro-5,8-dihydroxy-1,4-naphthoquinone, with an MIC of 2 µg/mL in C. krusei. These compounds showed higher activity against fungi, but the antibacterial activities were very low. The study of structure–activity relationships is very important in the search for new antimicrobial drugs due to the limited therapeutic arsenal.     

Tretinoin or retinol enhancement of lymphokine-activated killer cell proliferation and cytotoxicity against human bladder cancer cells in vitro

目的：研究维Ａ酸（Ｔｒｅ）或维生素Ａ（Ｒｅｔ）对膀胱肿瘤患者淋巴因子激活的杀伤细胞（ＬＡＫ细胞）的增殖和对膀胱肿瘤细胞的细胞毒作用．方法：分别用细胞计数和ＭＴＴ法测定ＬＡＫ细胞的增殖和细胞毒作用．结果：Ｔｒｅ或Ｒｅｔ１０－１００ｎｍｏｌ·Ｌ－１加强由白细胞介素２（ＩＬ２）诱导的ＬＡＫ细胞的增殖和对膀胱肿瘤细胞的杀伤作用．结论：Ｔｒｅ或Ｒｅｔ增强膀胱肿瘤患者ＬＡＫ细胞增殖及对膀胱肿瘤的细胞毒作用．     

Synthesis and in vitro biological activities of ferrocenyl–chalcone amides

A series of aminoferrocenyl–chalcone amides 11–19 were synthesized through condensation of a carboxylic acid-functionalized chalcone 10 with ferrocenylamines, using 1,1′-carbonyldiimidazole as the coupling agent. The compounds were screened for their antiplasmodial activities against CQS 3D7 and CQR FCR3 strains of Plasmodium falciparum. All compounds were found to be active, with IC₅₀ values ranging between 0.5–4.5 and 2.1–6.6 µM against 3D7 and FCR3, respectively. Amide 11, featuring a 2-aminoethylene linker, was the most active of all, with IC₅₀ values of 2.6 and 2.1 µM against the 3D7 and FCR3 strains, respectively. In screens against a panel of three cancer cell lines, i.e., TK-10, UACC-62, and MCF-7, amide 19, with a piperazinyl linker, showed increased activity against all three cell lines, compared to the reference drug, parthenolide. Antimicrobial assays that had been performed on six different microorganisms revealed that most of the synthesized amides were inactive against all of these microorganisms. Compound 17, however, with an aminodi(ethyleneoxy) linker, displayed moderate bactericidal activity against the gram-negative microorganisms, with a MIC₁₀₀ value of 128 µM. The outcomes of this study may hence significantly contribute toward malaria and cancer chemotherapy research, and more generally to the growing body of research that aims at illustrating the potential of employing organometallic compounds in medicinal chemistry programs.     

Synthesis, antimicrobial and cytotoxic activities of novel 4-trifluoromethyl-(1,2,3)-thiadiazolo-5-carboxylic acid hydrazide Schiff’s bases

A series of novel 1,2,3-thiadiazolo-5-carboxylic acid hydrazide Schiff’s bases 4a–4r were prepared starting from ethyl-4,4,4-trifluoroacetoacetate and ethyl carbazate in four steps. All the compounds were screened for antibacterial activity against various bacterial strains at 150 μg/ml concentration and found no activity. Similarly, all the compounds were screened for antifungal activity against various fungal strains at 100 and 150 μg/ml concentrations. Compounds 4a, 4m, and 4q found to show moderate activity against Candida albicans. Further, compounds were evaluated for cytotoxic activity against breast carcinoma cells MDA-MB 231 (aggressive), MCF-7 (non-aggressive) using doxorubicin as standard. Compound 4n was found to show 25.39 % cell viability against MDA-MB 231 and 63.60 % cell viability against MCF-7 cells.     

Anti-oxidative and anti-aging activities of 2-O-α-glucopyranosyl-L-ascorbic acid on human dermal fibroblasts

A stable ascorbic acid derivative, 2-O-α-glucopyranosyl-l-ascorbic acid (AA-2G), was evaluated and compared with ascorbic acid for its protective effect against cellular damage and senescence induced by hydrogen peroxide (H(2)O(2)). Pretreatment with AA-2G for 72 h promoted the proliferation of normal human dermal fibroblasts (NHDF) and protected against cell damage induced by H(2)O(2). In contrast, ascorbic acid increased the proliferation and protected against cell damage, only when culture medium containing ascorbic acid was replaced every 24 h during the pretreatment period. These results suggest that the effect of AA-2G is longer-lasting compared to that of ascorbic acid. Senescence associated-β-galactosidase (SA-β-gal) activity, a classical biomarker of cellular senescence, was increased in H(2)O(2)-exposed NHDF cells, but pretreatment or posttreatment with ascorbic acid or AA-2G significantly inhibited the increase in SA-β-gal levels. AA-2G was more potent than ascorbic acid in down-regulating SA-β-gal activity. Expression of SIRT1, which has attracted attention as an anti-aging factor in recent years, was significantly decreased in H(2)O(2)-exposed NHDF cells compared to untreated cells. However, pretreatment NHDF cells with AA-2G before H(2)O(2) exposure significantly inhibited this decrease in SIRT1 expression, whereas ascorbic acid had no effect. After H(2)O(2) exposure, the expression levels of p53 and p21 were increased in NHDF cells and pretreatment with AA-2G inhibited this increase. Together, these results suggest that AA-2G protects dermal fibroblasts from oxidative stress and cellular senescence. These characteristics indicate that AA-2G could become a promising material for its anti-aging properties.     

Synthesis and biological activities of Schiff bases of gabapentin with different aldehydes and ketones: a structure–activity relationship study

A series of novel gabapentin derivatives 6a–k and 7a–f were synthesized, and their biological activities were determined. The chemical structures were confirmed by elemental analyses, UV–visible, FT-IR, and ¹H NMR spectral studies. The structure–activity relationships (SAR) for anticonvulsant and antioxidant activities were discussed. Compounds 7a–f were evaluated for their possible anticonvulsant activity by Maximal Electroshock Seizure (MES) test, and their neurotoxic effects were determined by rotorod test. Majority of the compounds were active in MES tests. Compounds 7b and 7e showed good protective effect from seizure when compared to standard drug, phenytoin (100 mg/kg). The same compounds showed no neurotoxicity at the maximum dose administered (100 mg/kg). Most of the novel compounds showed DPPH radical scavenging activity, where compounds 6f, 6j, and 7a were the best radical scavengers (IC₅₀ was about 60 μg/ml).     

Structure–activity relationships and the cytotoxic effects of novel diterpenoid alkaloid derivatives against A549 human lung carcinoma cells

The cytotoxicity of three alkaloids from the roots of Aconitum yesoense var. macroyesoense as well as 36 semi-synthetic C₂₀-diterpenoid atisine-type alkaloid derivatives against A549 human lung carcinoma cells was examined. Ten acylated alkaloid derivatives, pseudokobusine 11-veratroate (9), 11-anisoate (12), 6,11-dianisoate (14), 11-p-nitrobenzoate (18), 11,15-di-p-nitrobenzoate (22), 11-cinnamate (25) and 11-m-trifluoromethylbenzoate (27), and kobusine 11-p-trifluoromethylbenzoate (35), 11-m-trifluoromethylbenzoate (36) and 11,15-di-p-nitrobenzoate (39), exhibited cytotoxic activity, and 11,15-dianisoylpseudokobusine (16) was found to be the most potent cytotoxic agent. Their IC₅₀ values against A549 cells ranged from 1.72 to 5.44 μM. In the occurrence of cytotoxic effects of atisine-type alkaloids, replacement by an acyl group at both C-11 and C-15 resulted in the enhancement of activity of the parent alkaloids compared to that from having hydroxy groups at this position, and the presence of a hydroxy group at the C-6 position was required for the cytotoxic effects. These acylated alkaloid derivatives inhibit cell growth through G1 arrest.