Circadian rhythm of anti-fungal prenylated chromene in leaves of Piper aduncum

Leaves of Piper aduncum accumulate the anti-fungal chromenes methyl 2,2-dimethyl-2H-1-chromene-6-carboxylate (1) and methyl 2,2-dimethyl-8-(3'-methyl-2'-butenyl)-2H-1-chromene-6-carboxylate (2). The enzymatic formation of 2 from dimethylallyl diphosphate and 1 was investigated using cell-free extracts of the title plant. An HPLC assay for the prenylation reaction was developed and the enzyme activity measured in the protein extracts. The prenyltransferase that catalyses the transfer of the dimethylallyl group to C-2' of 1 was soluble and required dimethylallyl diphosphate as the prenyl donor. In the leaves, the biosynthesis of the prenylated chromene 2 was time-regulated and prenyltransferase activity depended upon circadian variation. Preliminary characterisation and purification experiments on the prenyltransferase from P. aduncum have been performed.     

Photochromic agents as tools for protein structure study: lapachenole is a photoaffinity ligand of cytochrome P450 3A4

Cytochrome P450 3A4 is a drug-metabolizing enzyme of extraordinarily broad substrate specificity. This quality imparts upon the enzyme special importance in understanding its determinants of activity and substrate recognition. Limited successes in P450 3A4 active-site structure studies have been achieved by use of mechanism-based inactivators and photoaffinity ligands. We report here the potential of photochromic agents, compounds with the ability to undergo light-induced, reversible reactions, to be used as effective photoaffinity ligands. Four such compounds of the chromene family were shown by ultraviolet and visible spectroscopy to undergo photoinduced rearrangements to highly conjugated and reactive products in buffered aqueous solution. While some of these intermediates were very long-lived (>12 h, photoactivated lapachenole), others existed for milliseconds in their opened forms (precocene I and 2,2-dimethyl-5,6-benzo-2H-chromene) and were observed by laser flash photolysis. Each of the tricyclic structures studied rapidly underwent Michael addition reactions with the test nucleophile glutathione upon irradiation to form single conjugated products. The smaller precocene I reacted more extensively to form multiple products. These attributes of the chromenes inspired testing of their potential to label cytochrome P450 3A4 in a light-dependent fashion. Access to the protein active site by lapachenole was demonstrated with the molecule's ability to competitively inhibit P450 3A4-mediated oxidative metabolism of midazolam with an IC(50) value of 71 microM. This inhibition became irreversible upon irradiation of the enzyme-ligand complex with ultraviolet light. These results clearly demonstrate that chromenes are effective photoaffinity reagents for the cytochrome P450 superfamily of enzymes and probably other proteins as well.     

Synthesis and antibacterial activity of some new benzo[5,6]chromeno[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidines

The synthesis and antibacterial activity of some new benzo[5,6]chromeno[2,3-d]pyrimidine derivatives are described. The title compounds were obtained by the reaction of 1H-benzo[f]chromenes with aliphatic and aromatic amines. The structures of all newly synthesized compounds were confirmed by IR, ¹HNMR, ¹³C NMR, and NOESY experiments. The compounds exhibited potent antibacterial activity against gram-positive and gram-negative bacterial species. 10-Methyl-12-(4-hydroxyphenyl)-10,12-dihydro-11H-benzo[5,6]chromeno[2,3-d] pyrimidin-11-imine displayed greater antibacterial activity against gramnegative bacterial species than did ciprofloxacinandamoxicillin.     

Effect of 7,8-benzolfavone on the formation of benzo(alpha)pyrene-DNA-bound products in hamster embryo cells.

The hydrocarbon-deoxyribonucleoside products present in enzyme digests of DNA from hamster embryo cultures that had been treated with[3H]-benzo[alpha]pyrene (BP) were isolated by chromatography on Sephadex LH20 columns. The products isolated from cells treated with 7,8-benzoflavone (7,8-BF) for 18 h prior to the addition of [3H] BP were indistinguishable from the products isolated from untreated cultures, but the amounts of these products decreased with increasing concentrations of 7,8-BF. The amount of BP metabolized was also decreased in 7,8-BF-treated cultures. The decrease in the amounts of hydrocarbon-deoxyribonucleoside products per mg DNA was logarithmic with respect to the decrease in BP metabolism. The findings are consistent with the hypothesis that 7,8-BF inhibits both an initial and a later metabolic step involved in the conversion of BP to a reactive species that binds to cellular DNA.     

Comparative α-Naphthoflavone and β-Naphthoflavone Inhibits the Formation of a Carcinogenic Estrogen Metabolite

17β-Estradiol (E2) is hydrolyzed to 2-hydroxy-E2 and 4-hydroxy-E2 (4-OH-E2) via cytochrome P450 (CYP) 1B1. In estrogen target tissues including the mammary gland, ovaries and uterus, CYP1B1 is highly expressed, and 4-OH-E2 is predominantly formed in cancerous tissues. In the present study, we investigated the inhibitory activity of α-naphthoflavone and β-naphthoflavone against CYP1B1 using estrogen E2 as substrate in vitro to reveal structure–activity relationship between structure of flavonoids and inhibition. The results showed that α-naphthoflavone and β-naphthoflavone possessed inhibitory activity against CYP1B1-mediated E2 and the inhibition of α-naphthoflavone was stronger than β-naphthoflavone. By kinetic analyses, α-naphthoflavone displayed uncompetitive inhibition, while β-naphthoflavone displayed mixed inhibition. Taken together, the data suggested that the benzo at A ring of flavonoids play a prominent role in CYP1B1 inhibition, especially 7,8-benzo is better than 5,6-benzo. This study may help to reveal the relationship between the structure of flavonoids and the inhibition CYP1B1 for discovering new drugs in cancer therapy and prevention.     

Inhibition of microsome-mediated binding of benzo[a]pyrene to DNA by flavonoids either in vitro or after dietary administration to rats.

The in vitro and in vivo effects of selected natural flavonoids (flavone, flavanone, tangeretin, quercetin, chrysin) on the microsome-catalysed binding of [3H]benzo[a]pyrene to calf thymus DNA were investigated and compared with those of two synthetic flavonoids, 7,8-benzoflavone and 5,6-benzoflavone. In vitro addition of these flavonoids (0.1 mM) to an incubation system containing hepatic microsomes prepared from Aroclor 1254-pretreated rats strongly inhibited BaP-DNA adduct formation (72-89%). The incubation of BaP with hepatic microsomes prepared from animals fed 0.3% quercetin, tangeretin and 7,8-benzoflavone for 2 weeks also resulted in less effective binding of BaP metabolites to added DNA, than with microsomes from untreated rats. Other tested compounds, chrysin, flavone, flavanone and 5,6-benzoflavone showed no or little effect. The influence of flavonoid pretreatment on hepatic microsomal enzymes involved in BaP metabolism has also been examined. Aryl hydrocarbon hydroxylase activity was moderately increased (1.5-1.8-fold) in microsomes prepared from rats fed flavone, tangeretin, 7,8-benzoflavone and 5,6-benzo-flavone. Epoxide hydrolase activity was enhanced by 7,8-benzoflavone (1,6-fold), and by flavone and flavanone (5-fold). These results confirm that flavonoids, in vitro, are potent inhibitors of carcinogen-DNA binding. Oral administration of 0.3% flavonoids alters the properties of liver microsomes, resulting in the decreased ability of BaP metabolites to bind DNA.     

Chromenes of polyketide origin from Peperomia villipetiola

An extract of leaves and stems of Peperomia villipetiola has been found to contain myristicin (3-methoxy-4,5-methylenedioxy-allylbenzene) and seven chromenes, whose structures are methyl 5-hydroxy-7-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (1), methyl 5-methoxy-7-methyl-2,2-dimethyl-2H-1-chromene-8-carboxylate (2), methyl 7-hydroxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (3), methyl 7-methoxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (4), 5-methanol-7-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylic acid (5), 5-methanol-7-methoxy-2,2-dimethyl-2H-1-chromene-6-carboxylic acid (6), and methyl 5-acetoxymethanol-7-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylate (7). A biosynthetic rationale for 1-7 suggests that orsellinic acid may be a common intermediate. The anti-fungal activities of the chromenes were measured bioautographically against Cladosporium cladosporioides and Cladosporium sphaerospermum: compounds 6 and 7 were found to be the most active.     

Polycyclic aromatic hydrocarbon quinones may be either substrates for or irreversible inhibitors of the human placental NAD-linked 15-hydroxyprostaglandin dehydrogenase.

Under aerobic conditions, 9,10-phenanthrenequinone and 5,6-chyrsenequinone undergo oxidation-reduction cycling in the presence of NADH and the NAD-linked 15-hydroxyprostaglandin dehydrogenase. This results in the formation of potentially hazardous semiquinones, the superoxide anion, and H2O2. Superoxide dismutase inhibits this cycling by destroying the free radical chain propagator, the superoxide anion. Four other polycyclic aromatic hydrocarbon quinones are not substrates of the enzyme and they cause it to undergo a time-dependent inactivation. This presumably results from alkylation of the enzyme. Glutathione fully protects the enzyme against inactivation by 1,2-naphthoquinone but is only partially effective against 7,8-benzo[a]pyrenequinone. These results suggest that in tissues which contain the NAD-linked 15-hydroxyprostaglandin dehydrogenase some polycyclic aromatic hydrocarbon quinones might produce deleterious effects by undergoing redox cycling. Others might cause such effects by irreversibly inhibiting the enzyme which catalyzes the first step in prostaglandin catabolism.     

The effects of benzoflavones on polycyclic hydrocarbon metabolism and skin tumor initiation.

The effects of benzoflavones on skin tumor initiation by polycyclic hydrocarbons and epidermal aryl hydrocarbon hydroxylase were investigated. 7,8-Benzoflavone (7,8-BF) was found to be a potent inhibitor of the inhibition of skin tumors by 3-methylcholanthrene (MC) as well as 7,12-dimethylbenz(a)anthracene (DMBA). 5,6-Benzoflavone(5,6-BF) inhibited tumor initiation by MC and DMBA, but to a lesser degree than 7,8-BF. Dose-response studies of the capacity of 7,8-BF to inhibit DMBA tumor initiation revealed that 7,8-BF was an effective inhibitor at 2.5 microgram and a maximum inhibition of 90% occurred at 100 microgram of 7,8-FB. The tumor initiating ability of 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHMe-12MeBA) was not inhibited by 7,8-BF. Epidermal aryl hydrocarbon(benzo(a)pyrene hydroxylase(AHH) was increased by 5,6-BF and either had no effect or was slightly inhibited by 7,8-BF when given either topically or i.p. Both flavones when added directly to the assay tubes inhibited the in vitro epidermal AHH activity from control and MC pretreated mice by greater than 75%. When added in vitro, 7,8-BF and 5,6-BF inhibited epidermally mediated covalent binding of radioactive DMBA and dibenz(a,h)anthracene to DNA by 50% or more. The inhibition of skin tumor initiation by 7,8-BF and 5,6-BF appears to be partially related to its ability to inhibit the formation of electrophilic intermediates.     

Assessment of oxidative base damage to isolated and cellular DNA by HPLC-MS/MS measurement

Oxidation reactions that involve several oxygen and nitrogen reactive species together with nucleobase radical cations give rise among various classes of lesions to modified bases. About 70 of oxidized nucleosides that include diastereomeric forms have been characterized in mechanistic studies involving isolated DNA and related model compounds. However, only eight modified bases have been accurately measured within cellular DNA upon exposure to either gamma or UVA radiations. Emphasis is placed in this survey on recent developments of HPLC associated with tandem mass spectrometry (MS/MS) operating in the mild electrospray ionization mode. Interestingly, the HPLC-MS/MS assay in the multiple reaction monitoring mode appears to be the more sensitive and accurate method currently available for singling out several oxidized nucleosides including 8-oxo-7,8-dihydro-2'-deoxyguanosine, 8-oxo-7,8-dihydro-2'-deoxyadenosine, 5-formyl-2'-deoxyuridine, 5-(hydroxymethyl-2'-deoxyuridine, 5-hydroxy-2'-deoxyuridine, and the four diastereomers of 5,6-dihydroxy-5,6-dihydrothymidine within isolated and cellular DNA. However, one limitation of the assay that also applied to all chromatographic methods is the slight side-oxidation of normal bases during DNA extraction and subsequent work-up. This explains why the combined use of DNA repair glycosylases with either the comet assay or the alkaline elution technique is a better alternative to monitor the formation of low levels of oxidized bases within cellular DNA.     

Chromenes from Peperomia serpens (Sw.) Loudon (Piperaceae)

Chromatographic separation of the CH2Cl2 extract from leaves of Peperomia serpens yielded two chromenes [5-hydroxy-8-(3',7'-dimethylocta-2',6'-dienyl)-2,2,7-trimethyl-2H-1-chromene (1) and 5-hydroxy-8-(3'-methyl-2'-butenyl)-2,2,7-trimethyl-2H-1-chromene-6-carboxylic acid (2)], besides the known chromene [methyl 5-hydroxy-2,2,7-trimethyl-2H-1-chromene-6-carboxylate (3)] and the flavonoid, dihydrooroxylin (4). Their structural elucidation were achieved by spectroscopic analyses. The antifungal activities of the CH2Cl2 extract and the isolated chromenes were measured bioautographically against Cladosporium cladosporioides and C. sphaerospermum, when it was found that the crude extract showed higher activity as compared to the pure compounds.     

Evidence for translational control of the binding of 7, 12-dimethylbenz[a]anthracene to DNA of murine epidermal cell in culture.

The effects of various inhibitors of aryl hydrocarbon hydroxylase (AHH), antioxidants, inhibitors of DNA, RNA, and protein synthesis, and protease inhibitors on the binding of [7,12-3H]dimethylbenz[a]anthracene ([3H] DMBA) to DNA of murine epidermal cells in culture have been investigated. 7,8-Benzoflavone, 5,6-benzoflavone and methyrapone (inhibitors of AAH) and antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), efficiently reduced the binding of [3H] DMBA to cellular DNA. Inhibitors of DNA and RNA synthesis did not affect this process whereas inhibitors of protein synthesis suppressed the binding of [3H] DMBA to cellular DNA. Protease inhibitors p-tosylamide-2-phenylchloromethyl ketone (TPCK) and p-tosyl-L-lysine chloromethyl ketone (TLCK) also reduced the interaction between DMBA and DNA. Thus, it appears that binding of DMBA to cellular DNA is regulated at the level of translation or/and post translation.     

Metabolism and excretion of acetylchromenes by the migratory grasshopper

The extent of metabolism and excretion of three acetylchromenes (two toxic, one relatively nontoxic) were examined in adult migratory grasshoppers (Melanoplus sanguinipes) following topical administration. Both the total amount excreted (parent plus metabolites) and the proportion of parent compound in the excreta were inversely correlated with contact toxicity. Both toxic and nontoxic acetylchromenes are rapidly absorbed from the cuticle, with maximum excretion of parent and metabolite chromenes from 4 to 8 h posttreatment in each case. Much of the applied compounds (60–80%) apparently remains within the insect, and cannot be recovered by extraction of the insect. Metabolites formed result from simple oxidative and reductive transformations. For all of the compounds tested (including the allatocidin precocene II), the major mode of metabolism results from aliphatic hydroxylation of one of the geminal methyl groups on the chromene. No conjugated metabolites were found in the excreta.     

Host-mediated mutagenicity experiments with benzo[a]pyrene and two of its metabolites

Benzo[a]pyrene (BP) and two of its major metabolites, the ultimate mutagen BP-4,5-oxide and the proximate mutagen trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene (BP-7,8-diol) were investigated for mutagenicity in Salmonella typhimurium TA1538, TA98 and TA100 using an intrasanguineous host-mediated assay. BP and BP-4,5-oxide were not mutagenic under any experimental conditions. BP-7,8-diol was inactive with the strain TA1538 but was mutagenic with the strains TA98 and TA100. The effect was potentiated by pretreatment of the host mice with the cytochrome P-450 inducer 5,6-benzoflavone. We conclude: (i) one of the reasons for the observed insensitivity of the intrasanguineous host-mediated assay towards BP is that BP-4,5-oxide, which contributes to the microsome-mediated mutagenicity of BP, is inactive in the host-mediated assay; (ii) the finding that BP-7,8-diol is mutagenic in the host-mediated assay demonstrates that the lack of mutagenicity of BP is not intrinsic; (iii) the potentiated mutagenicity after treatment of the hosts with 5,6-benzoflavone suggests that cytochrome P-450 is more important in the activation of BP-7,8-diol in this system than other enzymes (e.g. prostaglandin synthase) that can also activate this compound in vitro.     

Peroxidase catalysed aerobic degradation of 5,6,7,8-tetrahydrobiopterin at physiological pH

The aerobic degradation of 5,6,7,8-tetrahydrobiopterin at neutral pH is catalysed by peroxidase (EC 1.11.1.7) and provides quinonoid 7,8-dihydro(6H)biopterin which readily loses the side chain to yield 7,8-dihydro(3H)pterin. The latter is in equilibrium with trace amounts of 6-hydroxy-5,6,7,8-tetrahydropterin (covalent hydrate) which is irreversibly oxidised to quinonoid 6-hydroxy-7,8-dihydro(6H)pterin, and this finally rearranges to 7,8-dihydroxanthopterin. Spectroscopic evidence (ultraviolet, 1H NMR and 13C NMR) is presented for the reversible addition of water across the 5,6-double bond of 7,8-dihydro(3H)pterin. The intermediate quinonoid 6-hydroxy-7,8-dihydro(6H)pterin is a good substrate for dihydropteridine reductase (EC 1.6.99.7) with a Km of 16.3 microM and kcat of 22.5 s-1. The rate of aerobic degradation (oxidation and loss of the side chain) of natural (6R)-5,6,7,8-tetrahydrobiopterin is several times slower than the rate for the unnatural (6S) isomer. By using a modified assay procedure the kinetic parameters for dihydropteridine reductase are as follows: with (6R)-7,8-dihydro(6H)biopterin Km = 1.3 microM and kcat = 22.8 s-1; with (6S)-7,8-dihydro(6H)biopterin Km = 13.5 microM and kcat = 51.6 s-1; and with (6RS)-7,8-dihydro(6H)neopterin Km = 19.2 microM and kcat = 116 s-1.     

Synthesis and enzymatic transformations of 5-halo-6-methoxy-5,6-dihydro derivatives of 5-[1-methoxy-2-halo (or 2,2-dihalo)ethyl]-2'-deoxyuridines as potential herpes simplex virus inhibitors

The 5-halo-6-methoxy-5,6-dihydro derivatives of 5-[1-methoxy-2-halo(or 2,2-dihalo)ethyl]-2'-deoxyuridines (3-12) were synthesized and investigated as potential anti-herpes agents. These 5,6-dihydro derivatives were designed to act as potential prodrugs to 5-[1-methoxy-2-halo(or 2,2-dihalo)ethyl]-2'-deoxyuridines (2a-e), with enhanced metabolic stability, and ready conversion to the parent molecules. These 5,6-disubstituted-5,6-dihydro analogs are stable to E. coli thymidine phosphorylase, and undergo regeneration of the 5,6-olefinic bond to provide parent moieties (2a-e), upon incubation with glutathione at 37 degrees C. The compounds (3-12) themselves were found to be non-inhibitory against herpes simplex virus type-1 (HSV-1), likely due in part to their inability to undergo conversion to parent compounds in cell culture medium.     

Metabolic activation of alpha-naphthoflavone by 2,3,7,8-tetrachlorodibenzodioxin-induced rat liver microsomes

Previous studies in our laboratory had demonstrated that addition of alpha-naphthoflavone (ANF) to lymphocytes from smokers or polychlorinated biphenyls (PCB)s-exposed individuals caused an increase in sister chromatid exchange (SCE) frequency whereas lymphocytes from controls were relatively unaffected. In order to investigate the mechanism responsible, metabolism of ANF by uninduced and 2,3,7,8-tetrachlorodibenzodioxin (TCDD)-induced microsomes was studied as a function of microsomal protein concentration and incubation time. Nonpolar metabolites were analyzed and the amount of conjugated (polar) and protein-bound metabolites determined. The initial ANF-metabolism rate was 10-fold higher in TCDD-induced microsomes (4.9 +/- 0.6 nmol/min per mg TCDD-induced microsomal protein vs. 0.5 +/- 0.2 nmol/min per mg uninduced microsomal protein) than in uninduced microsomes. Moreover, uninduced microsomes no longer metabolize ANF after 30-40 min while TCDD-induced microsomes metabolize ANF for longer than 2 h or until all the ANF is gone. In addition to the metabolites formed by uninduced microsomes [7,8-dihydro-7,8-dihydroxy-ANF (7,8-dihydrodiol); 5,6-dihydro-5,6-dihydroxy-ANF (5,6-dihydrodiol); 5,6-oxide-ANF and 6-hydroxy-ANF], TCDD-induced microsomes from unidentified metabolites. When TCDD-induced microsomes and 40 microM ANF were added to Chinese hamster ovary (CHO) cells, we found a correlation between the concentration of 5,6-oxide-ANF and clastogenicity to CHO cells. However, purified 5,6-oxide-ANF did not induce SCEs in CHO cells in the absence or presence of TCDD-induced microsomes. However, a minor metabolite (identified as the 9,10-dihydro-9,10-dihydroxy-ANF by acid dehydration) formed with TCDD-induced microsomes produces clastogenicity in CHO cells. These data indicate that a minor metabolite of ANF is a potent clastogen which suggests that this metabolite may be responsible for the ANF-mediated increases in SCE frequency in lymphocytes from smokers or PCB-exposed individuals.     

Drug metabolizing enzyme induction by benzoquinolines,acridine, and quinacrine; Tricyclic aromatic molecules containing a single heterocyclic nitrogen

Rats were treated with nitrogen-containing phenanthrene (3,4-, 5,6-, or 7,8-benzoquinoline) or anthracene (acridine or quinacrine) derivatives at a dose of 75 mg/kg, daily for 3 days. The hepatic drug metabolizing enzyme response ranged from no induction (quinacrine) through low (5,6-benzoquinoline), intermediate (acridine), and high (3,4-benzoquinoline) magnitude increases of only phase II enzymes, to induction of both phase I and phase II enzymes (7,8-benzoquinoline). The phase I enzyme response of 7,8-benzoquinoline was an induction of CYP1A. All three benzoquinolines, but neither anthracene derivative, elevated NAD(P)H quinone oxidoreductase activity. A similar pattern but of lesser magnitude was seen with glutathione S-transferase activity. 3,4-Benzoquinoline was the only agent to significantly increase microsomal epoxide hydrolase activity (2.3-fold). Both 3,4- and 7,8-benzoquinoline increased UDP-glucuronosyltransferase activity toward 4-nitrophenol (40% and 70%, respectively), but only the 3,4-isomer increased activity toward morphine (75%), diclofenac (75%), and testosterone (23%), and only the 7,8-isomer increased activity toward chloramphenicol (105%). 3,4-Benzoquinoline elevated the hepatic mRNA concentration of UGT2B1 but not UGT1*6. Acridine treatment increased UDP-glucuronosyltransferase activity toward morphine (47%), 1-naphthol (28%), testosterone (19%), and estrone (19%). Quinacrine failed to elevate any UDP-glucuronosyltransferase activity and depressed activities toward testosterone and estrone by 20%. This study shows that some tricyclic aromatic compounds containing a single heterocyclic nitrogen atom have the potential for use as chemoprotective agents based upon their ability to selectively induce only phase II enzymes. © 1997 John Wiley & Sons, Inc. J Biochem Toxicol 11: 297–303, 1997.     

Prenylated flavanones from the twigs of Dorstenia mannii

Investigation of the twigs of Dorstenia mannii gave 6,8-diprenyl-5,7,3′4′-tetrahydroxyflavanone and four new prenylated flavanones, named dorsmanins E-H and characterized as 5,6-7,8-bis-(2,2-dimethylchromano)-3′,4′-dihydroxyflavanone, 7,8-[2″-(1-hydroxy-1-methylethyl)-dihydrofurano]-6-prenyl-5,3′,4′-trihydroxyflavanone, 6,7-[2″-(1-hydroxy-1-methylethyl)dihydrofurano]-8-prenyl-5,3′,4′-trihydroxyflavanone and 6-prenyl-8-(2-hydroxy-3-methylbut-3-enyl)-5,7,3′,4′-tetrahydroxyflavanone, respectively, on the basis of spectral analysis and chemical evidence for the chromano derivative.     

New substituted 4H-chromenes as anticancer agents

As a continuation of our efforts to discover and develop small molecules as anticancer agents, we identified GRI-394837 as an initial hit from similarity search on RGD and its analogs. Based on GRI-394837, we designed and synthesized a focused set of novel chromenes (4a-e) in a single step using microwave method. All five compounds showed activity in the nanomolar range (IC(50): 7.4-640 nM) in two melanoma, three prostate and four glioma cancer cell lines. The chromene 4e is active against all the cell lines and particularly against the A172 human glioma cell line (IC(50): 7.4 nM). Interestingly, in vitro tubulin polymerization assay shows 4e to be a weak tubulin polymerization inhibitor but it shows very strong cytotoxicity in cellular assays, therefore there must be additional unknown mechanism(s) for the anticancer activity. Additionally, the strong antiproliferative activity was verified by one of the selected chromene (4a) by the NCI 60 cell line screen. These results strongly suggest that the novel chromenes could be further developed as a potential therapeutic agent for a variety of aggressive cancers.