The antiproliferative effect of acridone alkaloids on several cancer cell lines

Newly synthesized acridone derivatives targeting lung cancer: A toxicity and xenograft model study

AKT is one of the overexpressed targets in nonsmall cell lung cancer (NSCLC) and plays an important role in its progression and offers an attractive target for the therapy. The PI3K/AKT/mTOR pathway is upregulated in NSCLC. Acridone is an important heterocycle compound which treats cancer through various mechanisms including AKT as a target. In the present work, the study was designed to evaluate the safety profile of three acridone derivatives (AC-2, AC-7, and AC-26) by acute and repeated dose oral toxicity. In addition to this, we also checked the pAKT overexpression and its control by these derivatives in tumor xenograft model. The results from acute and repeated dose toxicity showed these compounds to be highly safe and free from any toxicity, mortality, or significant alteration in body weight, food, and water intake in the rats. In the repeated dose toxicity, compounds showed negligible variations in a few hematological parameters at 400 mg/kg. The histopathology, biochemical, and urine parameters remained unchanged. The xenograft model study demonstrated AC-2 to be inhibiting HOP-62 induced tumor via reduction in p-AKT1 (Ser473) expression significantly. In immunofluorescence staining AC-2 treated tissue section showed 2.5 fold reduction in the expression of p-AKT1 (Ser473). Histopathology studies showed the destruction of tumor cells with increased necrosis after treatment. The study concluded that AC-2 causes cell necrosis in tumor cells via blocking the p-AKT1 expression. The findings may provide a strong basis for further clinical applications of acridone derivatives in NSCLC.

K2CO3-Catalyzed Dual C-C-Coupled Cyclization to 3-Amino-4-benzoylbiphenyls and In Situ I2-Catalyzed C-N Bond Forming Annulation: A Metal-Free Synthesis of Arylacridones

Unprecedented metal-free cyclization catalysis reactions are developed in a highly regioselective fashion to synthesize 3-amino-4-benzoyl biphenyls and arylacridones with high atom economy. Catalytic K2CO3 is utilized as the only reagent for the unusual rapid dual C-C-coupled cyclization between β-keto enamines and cinnamaldehydes to furnish the functionalized biphenyls. Its C(sp2)-H functionalized C-N bond-forming cyclization was performed in situ using molecular I2 as a catalyst to furnish valuable arylacridones. Plausible mechanisms for the new cyclization reactions are predicted by conducting various control experiments and ESI-MS analyses.

A Proposed Association between Improving Energy Metabolism of HepG2 Cells by Plant Extracts and Increasing Their Sensitivity to Doxorubicin

Increasing cancer cell sensitivity to chemotherapy by amending aberrant metabolism using plant extracts represents a promising strategy to lower chemotherapy doses while retaining the same therapeutic outcome. Here, we incubated HepG2 cells with four plant extracts that were selected based on an earlier assessment of their cytotoxicity, viz asparagus, green tea, rue, and avocado, separately, before treatment with doxorubicin. MTT assays elucidated a significant decrease in doxorubicin-IC₅₀ following HepG2 incubation with each extract, albeit to a variable extent. The investigated extract's ultra-performance liquid chromatography and gas chromatography coupled with mass spectrometry (UPLC/MS and GC/MS) revealed several constituents with anticancer activity. Biochemical investigation displayed several favorable effects, including the inhibition of hypoxia-inducible factor1α (HIF1α), c-Myc, pyruvate kinase-M2 (PKM2), lactate dehydrogenase-A (LDH-A), glucose-6-phosphate dehydrogenase (G6PD), and glutaminase by asparagus and rue extracts. To less extent, HIF1α, c-Myc, PKM2, and LDH-A were partially inhibited by green tea extract, and HIF1α and glutaminase activity was inhibited by avocado oil. Undesirably, green tea extract increased glutaminase; avocado oil rose c-Myc, and both increased G6PD. In conclusion, our study confirms the potential cytotoxic effects of these plant extracts. It highlights a strong association between the ability of asparagus, green tea, rue, and avocado to sensitize HepG2 cells to doxorubicin and their power to amend cell metabolism, suggesting their use as add-on agents that might aid in clinically lowering the doxorubicin dose.

Studies Directed towards the Synthesis of the Acridone Family of Natural Products: Total Synthesis of Acronycines and Atalaphyllidines

A modular and flexible three-step synthetic strategy has been developed for the synthesis of acridone natural products of biological significance. The tetracyclic core of acridone derivatives has been achieved efficiently in high yield from commercially available anthranilic acid and phenol derivatives via condensation reaction, followed by regioselective annulation. Acridone alkaloids acronycine and noracronycine are synthesized in improved overall yields in fewer steps than the previously reported approaches. The method has further been used for the synthesis of atalaphyllidine and 5-hydroxynoracronycine in excellent yields for the first time. Moreover, the synthetic utility of the present strategy has been showcased by the synthesis of oxa and thia analogues of acronycine alkaloid.

Atalantiaphyllines A-G, prenylated acridones from Atalantia monophylla DC. and their aromatase inhibition and cytotoxic activities

Seven previously undescribed acridones, named atalantiaphyllines A-G, along with twenty-six known compounds were isolated from the dichloromethane extracts of roots and stems of Atalantia monophylla DC. Their structures were elucidated by analysis of extensive NMR and HRMS data. Aromatase inhibition, cytotoxicity against MOLT-3, HepG2, A549 and HuCCA-1 cell lines and DPPH radical scavenging activity of these compounds were evaluated. Most of the tested acridones exhibited higher potency in inhibiting aromatase than the positive control, ketoconazole, with IC₅₀ values in the range of 0.08-2.0 μM. In the cytotoxicity assay, cycloataphylline A, N-methylbuxifoliadine E and atalantiaphylline G were selectively cytotoxic against MOLT-3 cell line with IC₅₀ values of 8.0, 5.4 and 9.8 μM, respectively, while only atalaphyllidine exhibited highest antioxidant activity as evaluated by DPPH free radical scavenging assay with an IC₅₀ value of 22.4 μM.

Synthesis of novel cytotoxic tetracyclic acridone derivatives and study of their molecular docking, ADMET, QSAR, bioactivity and protein binding properties

Acridone based synthetic and natural products with inherent anticancer activity advancing the research and generating a large number of structurally diversified compounds. In this sequence we have designed, synthesized a series of tetracyclic acridones with amide framework viz., 3-(alkyloyl/ aryloyl/ heteroaryloyl/ heteroaryl)-2,3-dihydropyrazino[3,2,1-de]acridin-7(1H)-ones and screened for their in vitro anti-cancer activity. The in vitro study revealed that compounds with cyclopropyl-acetyl, benzoyl, p-hydroxybenzoyl, p-(trifluoromethyl)benzoyl, p-fluorobenzoyl, m-fluorobenzoyl, picolinoyl, 6-methylpicolinoyl and 3-nicotinoyl groups are active against HT29, MDAMB231 and HEK293T cancer cell lines. The molecular docking studies performed for them against 4N5Y, HT29 and 2VWD revealed the potential ligand-protein binding interactions among the neutral aminoacid of the enzymes and carbonyl groups of the title compounds with a binding energy ranging from - 8.1394 to - 6.9915 kcal/mol. In addition, the BSA protein binding assay performed for them has confirmed their interaction with target proteins through strong binding to BSA macromolecule. The additional studies like ADMET, QSAR, bioactivity scores, drug properties and toxicity risks ascertained them as newer drug candidates. This study had added a new collection of piperazino fused acridone derivatives to the existing array of other nitrogen heterocyclic fused acridone derivatives as anticancer agents.

Cytotoxic activity of dimeric acridone alkaloids derived from Citrus plants towards human leukaemia HL-60 cells

OBJECTIVES

Acridone alkaloids from Citrus and their derivatives show various kinds of biological activity. However, the anticancer activities of dimeric acridone alkaloids with unique structures and the molecular mechanism of these effects are poorly understood.

METHODS

We investigated the cytotoxicity effects of dimeric acridone alkaloids isolated from Marsh grapefruit on human myeloid leukaemia HL-60 cells.

KEY FINDINGS

Of the six dimeric acridone alkaloids tested, citbismine-E, the most potent, dose- and time-dependently decreased HL-60 cell viability by inducing apoptosis. The treatment of HL-60 cells with citbismine-E yielded a significant increase in levels of intracellular reactive oxygen species (ROS). Citbismine-E lowered the mitochondrial membrane potential and increased the activities of caspase-9 and -3. In addition, citbismine-E-induced apoptosis, decrease in mitochondrial membrane potential and caspase activation were significantly alleviated by pretreatment of the cells with antioxidant N-acetylcysteine (NAC). Citbismine-E induced intrinsic caspase-dependent apoptosis through ROS-mediated c-Jun N-terminal kinase activation. Citbismine-E-induced production of oxidative stress biomarkers, malondialdehyde and 8-hydroxy-2'-deoxyguanosine was also attenuated by pretreatment with NAC.

CONCLUSIONS

Citbismine-E is a powerful cytotoxic agent against HL-60 cells that acts by inducing mitochondrial dysfunction-mediated apoptosis through ROS-dependent JNK activation. Citbismine-E also induced oxidative stress damage via ROS-mediated lipid peroxidation and DNA damage in HL-60 cells.

Synthesis, cytotoxicity evaluation, and molecular modeling studies of 2,N10-substituted acridones as DNA-intercalating agents

Acridine-based compounds possess anticancer activities by intercalating to DNA. Although they have chemotherapeutic potential, acridine-based compounds are not used to treat cancer. In this study, 2, N10-acridone derivatives are designed and synthesized based on acridone, a ketone derivative of acridine. Herein, acridone is functionalized with alkyl side chains containing terminal nitrogen-based moieties at the N10-position and substituted at the C2-position. The products are evaluated for in vitro cytotoxicity against four cancer cell lines: Molt-3, HepG2, A549, and HuCCA-1. The derivative bearing two butyl piperidine side chains at the C2- and N10-positions is the most active, with IC50 values ranging from 2.96 to 9.46 µM. Molecular modeling studies supported the binding of the derivatives to DNA by intercalation, thereby confirming the observed cytotoxic effects.

Structural tuning of acridones for developing anticancer agents targeting dihydrofolate reductase

Targeting dihydrofolate reductase, here, we report the tumor growth inhibitory activity of substituted acridones. The screening of the molecules over 60 cell line panel of human cancer cells identified (S)-oxiran-2-ylmethyl 9-oxo-9,10-dihydroacridine-4-carboxylate (19) with average GI₅₀ 0.3 μM. The specificity of the compound to CCRF-CEM, MOLT-4 and SR cell lines of leukemia and SW-620, SF268, LOXIMVI, ACHN and MCF7 cancerous cells exhibiting GI₅₀ in the nM range was observed. C6 Glioma cells treated with compound 19 showed differentiated cell morphology and cell cycle arrest in G2/M phase. The interactions of the compound with dihydrofolate reductase were ascertained with the help of enzyme immunoassays, molecular docking and molecular dynamic studies.

Acridone alkaloids from the stem bark of Citrus aurantium display selective cytotoxicity against breast, liver, lung and prostate human carcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Citrus aurantium L. (Rutaceae) is used, either singly or as a part of a polyherbal preparation, in Nigerian traditional medicine for the management of cancer and inflammatory diseases. Currently, there is a dearth of knowledge demonstrating its anticancer potential.

AIM OF THE STUDY

This study was carried out to determine the in vitro cytotoxicity of the crude extract of the stem bark of C. aurantium, identify and isolate the bioactive constituents and to establish the cytotoxicity of such constituents.

MATERIALS AND METHODS

The powdered bark of C. aurantium was extracted by MeOH at room temperature (25-34 °C) and the crude extract was partitioned successively, with n-hexane, dichloromethane and methanol. Amongst the fractions, the DCM fraction was the most active and compounds were isolated from this fraction using a combination of chromatographic techniques. The structures of the isolated compounds were elucidated by spectroscopic means (MS, 1D and 2D NMR). The cytotoxicity of the extract, and the isolated compounds were evaluated by the MTT assay against four human cancer cell lines: A549 (lung), HepG2 (liver), MCF7 (breast) and PC3 (prostate). The selectivity of the isolated compounds was assessed using the normal human prostate epithelium cells (PNT2).

RESULTS AND DISCUSSION

Of the three plant fractions, the DCM fraction showed significant cytotoxicity, with its highest activity against A549 cells (IC₅₀ = 3.88 µg/mL) and the least activity on HepG2 cells (IC₅₀ = 5.73 µg/mL). Six acridone alkaloids, citrusinine-I (1), citracridone-I (2), 5-hydroxynoracronycine (3), natsucitrine-I (4), glycofolinine (5) and citracridone-III (6), were isolated from the DCM fraction of C. aurantium. The isolated compounds demonstrated potent to moderate cytotoxicity (IC₅₀ = 12.65-50.74 µM) against the cancer cells under investigation. It is noteworthy that the compounds exerted cytotoxicity at least four times more selective towards the carcinoma cells than the PNT2 cells.

CONCLUSION

The results obtained from this study have provided some evidence for the ethnomedicinal use of C. aurantium against cancer and the acridone alkaloids present in its stem bark, have appeared to be responsible for the anticancer effects.

Synthesis, anticonvulsant, antioxidant and binding interaction of novel N-substituted methylquinazoline-2,4(1H,3H)-dione derivatives to bovine serum albumin: a structure-activity relationship study

A novel class of N-substituted glycosmicine derivatives was synthesized, and their anticonvulsant, antioxidant activity and interaction with bovine serum albumin (BSA) were evaluated. The synthesized compounds 4a-j were examined for anticonvulsant activity by maximal electroshock induced seizures (MESs) test and their neurotoxic effects were determined by rotorod test in mice. The structure-activity relationships (SARs) of these compounds were also investigated. Compounds 4d, 4g, 4i and 4j were found to have good protective effect from seizure. The in vitro antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging assay. The interaction between novel N-substituted methylquinazoline-2,4(1H,3H)-dione (NMQ) and BSA was analyzed by fluorescence and ultraviolet spectroscopy at 304K under simulative physiological conditions. BSA fluorescence quenched by NMQ is discussed according to the Stern-Volmer equation. The binding constant and binding sites of NMQ with BSA were calculated. According to Forster non-radiation energy transfer theory, the binding distance (r) between NMQ and BSA was calculated.

Two new acridone alkaloids from Glycosmis macrantha

Extraction and chromatographic separation of the extracts of dried stem barks of Glycosmis macrantha lead to isolation of two new acridone alkaloids, macranthanine (1) and 7-hydroxynoracronycine (2), and a known acridone, atalaphyllidine (3). The structures of these alkaloids were determined by detailed spectral analysis and also by comparison with reported data.

A natural compound from Hydnophytum formicarium induces apoptosis of MCF-7 cells via up-regulation of Bax

BACKGROUND

Hydnophytum formicarium Jack is an epyphytic shrub that belongs to the family of Rubiaceae and is native to the tropical rain forests of the Asean region, which includes Malaysia. A flavanoid derivative, 7, 3', 5'-trihydroxyflavanone (3HFD), isolated from H. formicarium has been reported to have cytotoxic effects on the human breast carcinoma cell line MCF-7. The aim of the current study was to investigate the mode of cell death in MCF-7 cells treated with 3HFD. A DNA fragmentation assay was conducted on isolated genomic DNA, a TUNEL assay was used to determine the mode of cell death and Western blotting was used to evaluate the expression levels of Bax and Bcl-2. Immunofluorescence staining of MCF-7 cells was also performed to confirm the up-regulation of the Bax protein.

RESULTS

The ladder pattern resulting from the DNA fragmentation assay was a multimer of 180 kb. The morphological changes of cells undergoing apoptosis were visualised by a TUNEL assay over time. The percentage of apoptotic cells increased as early as 6 hours post treatment compared to untreated cells. Western blotting revealed up-regulation of the pro-apoptotic protein Bax. However, 3HFD did not affect expression of the anti-apoptotic protein Bcl-2.

CONCLUSIONS

Our results provide evidence that plant-derived 3HFD was able to induce the apoptotic cell death of MCF-7 cells by increasing Bax expression level and makes 3HFD a promising agent for chemotherapy, which merits further study.

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

Chemical investigation of the roots and fruits of Zanthoxylumleprieurii 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 LD(50) at 13.1microg/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 IC(50) values ranging from 27 to 77microM. 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 IC(50) of 51+/-8microM and 4.3+/-0.4microM, respectively.

Atalaphylline

The title acridone alkaloid [systematic name: 1,3,5-trihydr­oxy-2,4-bis­(3-methyl­but-2-en­yl)acridin-9(10H)-one], C₂₃H₂₅NO₄, known as atalaphylline, was isolated from Atalantia monophylla Corrêa, a mangrove plant. The mol­ecule contains three fused planar rings with an r.m.s. deviation of 0.026 (2) Å. Both 3-methyl­but-2-enyl substituents are in a (−)anticlinal conformation. An intra­molecular N—H⋯O hydrogen bond generates an S(5) ring motif, while an intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, the mol­ecules are linked into screw chains along [010] by inter­molecular O—H⋯O hydrogen bonds. These chains are stacked along the a axis by π–π inter­actions with centroid–centroid distances of 3.6695 (13) and 3.6696 (13) Å.

Search for MDR modulators: design, syntheses and evaluations of N-substituted acridones for interactions with p-glycoprotein and Mg2+

By combining the structural features of acridone based anti-cancer drugs (like amsacrine) and MDR modulator propafenone, acridones with hydroxyl amine chain at N-10 have been designed and synthesized. These molecules exhibit appreciable interactions with p-gp and Mg(2+) indicating their suitability to modulate p-gp mediated multi drug resistance.

Potential anti-allergic acridone alkaloids from the roots of Atalantia monophylla

Acridone alkaloids, cycloatalaphylline-A (1), N-methylcyclo-atalaphylline-A (2) and N-methylbuxifoliadine-E (3), were isolated from the dichloromethane and acetone extracts of the root of Atalantia monophylla along with eight known acridone alkaloids: buxifoliadine-A (4), buxifoliadine-E (5), N-methylatalaphylline (6), atalaphylline (7), citrusinine-I (8), N-methylataphyllinine (9), yukocitrine (10) and junosine (11) and two known coumarins: auraptene (12) and 7-O-geranylscopoletin (13). Their structures were elucidated on the basis of spectroscopic analyses. Compounds 2, 5 and 8 possessed appreciable anti-allergic activity in RBL-2H3 cells model with IC(50) values of 40.1, 6.1 and 18.7 microM, respectively.

Acridone and furoquinoline alkaloids from Teclea gerrardii (Rutaceae: Toddalioideae) of southern Africa

The combined hexane/CH(2)Cl(2) extract of the stem bark of Teclea gerrardii (Rutaceae: Toddalioideae) has yielded two acridone alkaloids, 3-hydroxy-1-methoxy-N-methylacridone (tegerrardin A) (1) and 3-hydroxy-N-methyl-1-(gamma,gamma-dimethylallyloxy)acridone (tegerrardin B) (2), three known acridones (3-5), two known furoquinolines (6,7), and the acridone precursor tecleanone (8). Arborinine (3) and evoxine (6) displayed moderate antiplasmodial activity against the CQS D10 strain of Plasmodium falciparum, with IC(50) values of 12.3 and 24.5 microM, respectively.

In vitrocytotoxicity activity on several cancer cell lines of acridone alkaloids andN-phenylethyl-benzamide derivatives fromSwinglea glutinosa(Bl.) Merr

The methanol extract from the stems and fruits of Swinglea glutinosa (Rutaceae) afforded 11 known acridone alkaloids and three N-phenylethyl-benzamide derivatives, glycocitrine-IV, 1,3,5-trihydroxy-4-methoxy-10-methyl-2,8-bis(3-methylbut-2-enyl)acridin-9(10H)-one, 1,3,5- trihydroxy-2,8-bis(3-methylbut-2-enyl)-10-methyl-9-acridone, citbrasine, citrusinine-II, citrusinine-I, 5-dihydroxyacronycine, pyranofoline, 3,4-dihydro-3,5,8-trihydroxy-6-methoxy-2,2,7-trimethyl-2H-pyrano[2,3-a]acridin-12(7H)-one, 2,3-dihydro-4,9-dihydroxy-2-(2-hydroxy-propan-2-yl)-11-methoxy-10-methylfuro[3,2-b]acridin-5(10H)-one, bis-5-hydroxyacronycine, N-(2-{4-[(3,7-dimethylocta-2,6-dien-1-yl)oxy]phenyl}ethyl)benzamide, N-(2-{4-[(3,7-dimethyl-4-acethyl-octa-2,6-dien-1-yl)oxy]phenyl}ethyl)benzamide, and severine acetate. All compounds isolated were examined for their activity against three cancer cell lines: human lung carcinoma (COR-L23), human breast adenocarcinoma (MCF7), human melanoma (C32), and normal human fetal lung cell line, MRC-5. The acridones tested exhibited weak cytotoxicity but the amides showed moderate nonselective cytotoxic activity.

Evaluation and lead optimization of anti-malarial acridones

With 2-methoxy-6-chloroacridone as a lead compound, we synthesized and tested acridone derivatives to develop a better understanding of the anti-malarial structure-activity relationships. Over 30 acridone derivatives were synthesized. The most potent compounds contained extended alkyl chains terminated by trifluoromethyl groups and located at the 3-position of the tricyclic system. Acridones optimized in the length of the side chain and the nature of the terminal fluorinated moiety exhibited in vitro anti-malarial IC(50) values in the low nanomolar and picomolar range and were without cytotoxic effects on the proliferation and differentiation of human bone marrow progenitors or mitogen-activated murine lymphocytes at concentrations up to 100,000-fold higher. Based on a structural similarity to known anti-malarial agents it is proposed that the haloalkoxyacridones exert their anti-malarial effects through inhibition of the Plasmodium cytochrome bc(1) complex. Haloalkoxyacridones represent an extraordinarily potent novel class of chemical compounds with the potential for development as therapeutic agents to treat or prevent malaria in humans.

Algicidal and antifungal compounds from the roots of Ruta graveolens and synthesis of their analogs

Bioassay-guided fractionation of the ethyl acetate extract of Ruta graveolens roots yielded rutacridone epoxide with potent selective algicidal activity towards the 2-methyl-isoborneol (MIB)-producing blue-green alga Oscillatoria perornata, with relatively little effect on the green alga Selenastrum capricornutum. The diol-analog of rutacridone epoxide, gravacridondiol, which was also present in the same extract, had significantly less activity towards O. perornata. Rutacridone epoxide also showed significantly higher activity than commercial fungicides captan and benomyl in our micro-bioassay against the agriculturally important pathogenic fungi Colletotrichum fragariae, C. gloeosporioides, C. acutatum, and Botrytis cineara and Fusarium oxysporium. Rutacridone epoxide is reported as a direct-acting mutagen, precluding its use as an agrochemical. In order to understand the structure-activity relationships and to develop new potential biocides without toxicity and mutagenicity, some analogs containing the (2-methyloxiranyl)-dihydrobenzofuran moiety with an epoxide were synthesized and tested. None of the synthetic analogs showed comparable activities to rutacridone epoxide. The absolute stereochemistry of rutacridone was determined to be 2'(R) and that of rutacridone epoxide to be 2'(R), 3'(R) by CD and NMR analysis.

Cancer chemopreventive activity of acridone alkaloids on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis

Seventeen acridone alkaloids isolated from the Rutaceous plants were tested for their inhibitory activities against Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. Some prenylated acridones were found to have remarkably potent activities. 1,3-Dihydroxy-10-methyl-2,4-diprenylacridone (18) as synthesized according to these results in vitro, exhibited a marked inhibitory effect on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. The result of the present investigation indicated that some of these acridone alkaloids may be potentially valuable cancer chemopreventive agents.

Bioactive acridone alkaloids from Swinglea glutinosa

A new prenylated acridone alkaloid, 1,3,5-trihydroxy-2,8-bis(3-methylbut-2-enyl)-10-methyl-9-acridone (1), was isolated from the stembark of Swinglea glutinosa, along with three known acridone alkaloids, 5-hydroxynoracronycine (2), 1,3,5-trihydroxy-4-methoxy-2-(3-methylbut-2-enyl)-10-methyl-9-acridone (3), and 1,3,5-trihydroxy-4-methoxy-10-methylacridone (4). The isolated alkaloids were assessed in vitro against chloroquine-sensitive and -resistant Plasmodium falciparum strains and for cytotoxicity using HeLa cells.

Antiproliferative effects of the readily extractable fractions prepared from various citrus juices on several cancer cell lines

To eliminate the masking effect by flavonoid glycosides, which comprise approximately 70% of conventionally prepared sample, the readily extractable fraction from Citrus juice, which was prepared by adsorbing on HP-20 resin and eluting with ethanol and acetone from the resin, was subjected to antiproliferative tests against several cancer cell lines. Screening of 34 Citrus juices indicated that King (Citrus nobilis) strongly inhibited proliferation of all cancer cell lines examined. Sweet lime and Kabuchi inhibited three of the four cancer cell lines. In contrast, these samples were substantially less cytotoxic toward normal human cell lines.