8,9-methylenedioxybenzo[i]phenanthridines: topoisomerase I-targeting activity and cytotoxicity

Research progress in pharmacological activities and structure-activity relationships of tetralone scaffolds as pharmacophore and fluorescent skeleton

The tetralone and tetralone derivatives, as crucial structural scaffolds of potential novel drugs targeted at multiple biological end-points, are normally found in several natural compounds and also, it can be used as parental scaffold and/or intermediate for the synthesis of a series of pharmacologically active compounds with a broad-spectrum of bioactivities including antibacterial, antitumor, CNS effect and so on. Meanwhile, SAR information of its analogues has drawn attentions among medicinal chemists, which could contribute to the further research related to tetralone derivatives aimed at multiple targets. This review encompasses pharmacological activities, SAR analysis and docking study of tetralone and its derivatives, expecting to provide a general retrospect and prospect on tetralone derivatives.

Pharmaceutically relevant (hetero)cyclic compounds and natural products from lignin-derived monomers: Present and perspectives

Lignin, the richest source of renewable aromatics on the planet, is an intriguing raw material for the construction of value-added aromatics. In the past decade, much progress has been made regarding the development of efficient lignin depolymerization methods, able to produce specific monophenol derivatives in high-enough selectivity and yields. This now serves as an excellent basis for developing powerful downstream conversion strategies toward a wide range of products, including fine chemical building blocks. The inherent structural features of lignin-derived platform chemicals undoubtedly inspire the development of novel, creative, atom-economic synthetic routes toward biologically active molecules or natural products. In this perspective we attempt to bridge the structural features of lignin-derived platform chemicals with existing synthetic strategies toward the construction of heterocycles and provide a summary of efforts for the production of natural products from aromatics that can be, in principle, obtained from lignin. Last, we comment on the latest efforts that present entire value-chains from wood to valuable pharmaceutically relevant compounds.

Modular Synthesis and Biological Investigation of 5-Hydroxymethyl Dibenzyl Butyrolactones and Related Lignans

Dibenzyl butyrolactone lignans are well known for their excellent biological properties, particularly for their notable anti-proliferative activities. Herein we report a novel, efficient, convergent synthesis of dibenzyl butyrolactone lignans utilizing the acyl-Claisen rearrangement to stereoselectively prepare a key intermediate. The reported synthetic route enables the modification of these lignans to give rise to 5-hydroxymethyl derivatives of these lignans. The biological activities of these analogues were assessed, with derivatives showing an excellent cytotoxic profile which resulted in programmed cell death of Jurkat T-leukemia cells with less than 2% of the incubated cells entering a necrotic cell death pathway.

Polyphenols from wolfberry and their bioactivities

Nine new phenylpropanoids, one new coumarin, and 43 known polyphenols were isolated from wolfberry. Their structures were determined by spectroscopic analyses, chemical methods, and comparison of NMR data. Polyphenols, an important type of natural products, are notable constituents in wolfberry. 53 polyphenols, including 28 phenylpropanoids, four coumarins, eight lignans, five flavonoids, three isoflavonoids, two chlorogenic acid derivatives, and three other constituents, were identified from wolfberry. Lignans and isoflavonoids were firstly reported from wolfberry. 22 known polyphenols were the first isolates from the genus Lycium. This research presents a systematic study on wolfberry polyphenols, including their bioactivities. All these compounds exhibited oxygen radical absorbance capacity (ORAC), and some compounds displayed DPPH radical scavenging activity. One compound had acetylcholinesterase inhibitory activity. The discovery of new polyphenols and their bioactivities is beneficial for understanding the scientific basis of the effects of wolfberry.

QSAR modeling on benzo[c]phenanthridine analogues as topoisomerase I inhibitors and anti-cancer agents

Benzo[c]phenanthridine (BCP) derivatives were identified as topoisomerase I (TOP-I) targeting agents with pronounced antitumor activity. In this study, hologram-QSAR, 2D-QSAR and 3D-QSAR models were developed for BCPs on topoisomerase I inbibitory activity and cytotoxicity against seven tumor cell lines including RPMI8402, CPT-K5, P388, CPT45, KB3-1, KBV-1and KBH5.0. The hologram, 2D, and 3D-QSAR models were obtained with the square of correlation coefficient R² = 0.58-0.77, the square of the crossvalidation coefficient q² = 0.41-0.60 as well as the external set's square of predictive correlation coefficient r² = 0.5-0.80. Moreover, the assessment method based on reliability test with confidence level of 95% was used to validate the predictive power of QSAR models and to prevent over-fitting phenomenon of classical QSAR models. Our QSAR model could be applied to design new analogues of BCPs with higher antitumor and topoisomerase I inhibitory activity.

A support vector machine classification model for benzo[c]phenathridine analogues with toposiomerase-I inhibitory activity

Benzo[c]phenanthridine (BCP) derivatives were identified as topoisomerase I (TOP-I) targeting agents with pronounced antitumor activity. In this study, a support vector machine model was performed on a series of 73 analogues to classify BCP derivatives according to TOP-I inhibitory activity. The best SVM model with total accuracy of 93% for training set was achieved using a set of 7 descriptors identified from a large set via a random forest algorithm. Overall accuracy of up to 87% and a Matthews coefficient correlation (MCC) of 0.71 were obtained after this SVM classifier was validated internally by a test set of 15 compounds. For two external test sets, 89% and 80% BCP compounds, respectively, were correctly predicted. The results indicated that our SVM model could be used as the filter for designing new BCP compounds with higher TOP-I inhibitory activity.

Tumor-selective cytotoxicity of benzo[c]phenanthridine derivatives from Toddalia asiatica Lam

PURPOSE

To develop a novel anti-cancer drug of low side effect against lung adenocarcinoma, the authors screened the bioresources of Okinawa Island, Japan. The medicinal plant Toddalia asiatica Lam. contained three benzo[c]phenanthridine derivatives: dihydronitidine (DHN), nitidine (NTD) and demethylnitidine (DMN). Of the three derivatives, DHN had been shown to selectively inhibit the growth of cancer cells in our previous study. Because of similar molecular topology of NTD or DMN to DHN, it can be expected that NTD and DMN also show selective cytotoxicity. The aim of the present study was therefore to examine the selective cytotoxicity of these two compounds in vitro and in vivo.

METHODS

Benzo[c]phenanthridine derivatives were isolated from T. asiatica Lam., and their chemical structures were identified by interpretation of NMR and MS spectrum. Of the isolated compounds, NTD and DMN were evaluated for cytotoxicity in vitro or in vivo.

RESULTS

NTD as well as DHN selectively reduced the growth of murine and human lung adenocarcinoma in vitro with selective intracellular accumulation. NTD has also been proven to be highly effective in vivo to inhibit the growth of both murine and human lung adenocarcinoma in a subcutaneous xenograft model without any deteriorating side effect. In contrast, DMN had no selective cytotoxicity suggesting that 8-methoxy group of NTD is the critical structural feature for the selective cytotoxicity.

CONCLUSIONS

This study thus proves the effectiveness of benzo[c]phenanthridine derivatives as anti-cancer agent in vivo for the first time, and discusses the mechanisms responsible for the selective cytotoxicity.

12-Substituted 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phenanthridines as novel topoisomerase I-targeting antitumor agents

2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine and a few of its 12-substituted analogs are active as TOP1-targeting agents. Studies were performed to further evaluate the potential of this series of non-camptothecin TOP1-targeting agents. The influence of a hydroxymethyl, formyl, N,N-dimethylaminomethyl, 2-(N,N-dimethylamino)ethyl, 3-(N,N-dimethylamino)propyl), and 4-(N,N-dimethylamino)butyl substituent at the 12-position on TOP1-targeting activity and tumor cell growth was evaluated. In addition, the relative pharmacologic activities of the 12-carboxamide analog, as well as its N-methyl and N,N-dimethyl derivatives were assessed.

6-Substituted 6H-dibenzo[c,h][2,6]naphthyridin-5-ones: reversed lactam analogues of ARC-111 with potent topoisomerase I-targeting activity and cytotoxicity

6-Substituted 8,9-dimethoxy-2,3-methylenedioxy-6H-dibenzo[c,h][2,6]naphthyridin-5-ones were synthesized and evaluated for topoisomerase I-targeting activity and cytotoxicity. Several of these reversed lactam analogues of ARC-111 exhibited exceptional cytotoxicity with IC50 values ranging from 0.5 to 3.0 nM. In contrast to topotecan, no resistance was observed with several of these reversed lactam analogues in tumor cell lines that overexpressed the efflux transporters MDR1 or BCRP.

Esters and amides of 2,3-dimethoxy-8,9-methylenedioxy-benzo[i]phenanthridine-12-carboxylic acid: Potent cytotoxic and topoisomerase I-targeting agents

The exceptional topoisomerase I-targeting activity and antitumor activity of 5-(2-N,N-dimethylamino)ethyl-8,9-dimethoxy-2,3-methylenedioxy-5H-dibenzo[c,h][1,6]naphthyridin-6-one (ARC-111, topovale) prompted studies on similarly substituted benzo[i]phenanthridine-12-carboxylic ester and amide derivatives. Among the benzo[i]phenanthridine-12-carboxylic esters evaluated, the 2-(N,N-dimethylamino)ethyl, 2-(N,N-dimethylamino)-1-methylethyl, and 2-(N,N-dimethylamino)-1,1-dimethylethyl esters possessed similar cytotoxicity, ranging from 30 to 55 nM in RPMI8402 and KB3-1 cells. Several of the carboxamide derivatives possess potent topoisomerase I-targeting activity and cytotoxicity. The 2-(N,N-dimethylamino)ethyl, 2-(N,N-diethylamino)ethyl, and 2-(pyrrolidin-1-yl)ethyl amides were among the more cytotoxic benzo[i]phenanthridine-12-carboxylic derivatives, with IC50 values ranging from 0.4 to 5.0 nM in RPMI8402 and KB3-1 cells.

Novel and specific inhibitors of a poxvirus type I topoisomerase

Vaccinia DNA topoisomerase (vTopo) is a prototypic pox virus family topoisomerase that shares extensive structural and mechanistic properties with the human type IB enzyme (hTopo) and is important for viral replication. Despite their far-reaching similarities, vTopo and hTopo have surprisingly distinct pharmacological properties. To further exploit these differences, we have developed recently the first high-throughput screen for vTopo, which has allowed rapid screening of a 1990-member small-molecule library for inhibitors. Using this approach, 21 compounds were identified with IC(90) values less than 10 muM, and 19 of these were also found to inhibit DNA supercoil relaxation by vTopo. Four of the most potent compounds were completely characterized and are structurally novel topo I inhibitors with efficacies at nanomolar concentrations. These inhibitors were highly specific for vTopo, showing no inhibition of the human enzyme even at 500- to 2000-fold greater concentrations. We describe a battery of efficient experiments to characterize the unique mechanisms of these vTopo inhibitors and discuss the surprising promiscuity of this enzyme to inhibition by structurally diverse small molecules.

Dimethoxybenzo[i]phenanthridine-12-carboxylic acid derivatives and 6H-dibenzo[c,h][2,6]naphthyridin-5-ones with potent topoisomerase I-targeting activity and cytotoxicity

The exceptional TOP1-targeting activity and antitumor activity of ARC-111, 1, prompted studies on similarly substituted benzo[i]phenanthridine-12-carboxylic ester and amide derivatives. These studies were extended to include 6-substituted 8,9-dimethoxy-2,3-methylenedioxy-dibenzo[c,h][2,6]naphthyridin-5-ones, which represent reversed lactam analogues of 1. Several of these analogues retained the potent TOP1-targeting activity and cytotoxicity observed for ARC-111.

Synthesis and cytotoxic activity of benzo[c][1,7] and [1,8]phenanthrolines analogues of nitidine and fagaronine

Fagaronine and nitidine are natural benzo[c] phenanthridinium alkaloids, which display antileukemic activity. Both act as topoisomerase I and topoisomerase II inhibitors. The objective of the present study was to prepare noncharged isosters of these compounds, with replacement of the aromatic A ring by a pyridine ring, present in other topoisomerase I inhibitors. Various 7,8- and 8,9-dimethoxy and metylenedioxy benzo[c][1,7] and [1,8]phenanthrolines were readily synthesized by benzyne-mediated cyclization of the corresponding substituted N-(2-halobenzyl)-5-quinolinamines or 5-isoquinolinamines. In both series, compounds bearing oxygenated substituents at positions 8 and 9 exhibited cytotoxic properties towards L1210 murine leukemia cells, which may result from their capacities to intercalate into DNA. Topoisomerase I inhibition was observed for all active compounds.