Synthesis and Cytotoxicity Assessment against Human Colorectal Cancer Cell Lines of Quaternary 8-Dichloromethyl Protoberberine Alkaloids.

Twenty-two quaternary 8-dichloromethylprotoberberine alkaloids were synthesized from unmodified quaternary protoberberine alkaloids (QPAs) to improve their physical and chemical properties and to obtain selectively anticancer derivatives. The synthesized derivatives showed more appropriate octanol/water partition coefficients by up to values 3-4 compared to unmodified QPA substrates. In addition, these compounds exhibited significant antiproliferative activity against colorectal cancer cells and lower toxicity on normal cells, resulting in more significant selectivity indices than unmodified QPA compounds in vitro. The IC50 values of antiproliferative activity of quaternary 8-dichloromethyl-pseudoberberine 4-chlorobenzenesulfonate and quaternary 8-dichloromethyl-pseudopalmatine methanesulfonate against colorectal cancer cells are 0.31 µM and 0.41 µM, respectively, significantly stronger than those of other compounds and positive control 5-fluorouracil. These findings suggest that 8-dichloromethylation can be used as one of the modification strategies to guide the structural modification and subsequent investigation of anticancer drugs for CRC based on QPAs.

Chemoproteomics Reveals That Quaternary Protoberberine Alkaloids Inhibit Telomerase Activity Oncologically by Binding to PES1.

Natural QPAs have anti-cancer property. The prodrugs of QPAs synthesized in our work with significantly improved solubility showed significantly stronger activity in animal experiments. Nevertheless, the mechanism of action of QPAs for treating cancers remains poorly understood. Here, a chemoproteomic study reveals that QPAs non-covalently and multivalently bind to PES1 in CRC cells, which impinges on the direct interaction between hTERT and hTR in the assembly of the telomerase complex, downregulates telomerase activity, and so promotes the aging process of CRC cells. This study is beneficial for us to conduct extensively the pharmaceutical chemistry research of QPAs.

Trifluoromethylation of dihydrocoptisines and the effect on structural stability and XBP1-activating activity.

In order to obtain new dihydrocoptisine-type compounds with stable structure and activating XBP1 transcriptional activity, (±)-8-trifluoromethyldihydrocoptisine derivatives as target compounds were synthesized from quaternary ammonium chlorides of coptisine alkaloids as starting materials by a one-step reaction. The structures of the synthesized compounds were confirmed by 1H-, 13C-, and 19F-NMR as well as HRESIMS methods. These compounds showed more significant structural stability and activating XBP1 transcription activity in vitro than dihydrocoptisine as positive control. No obvious cytotoxicity on normal cell in vitro was observed with (±)-8-trifluoromethyldihydrocoptisines. Trifluoromethylation can be used as one of the fluorine modification strategies for dihydrocoptisines to guide follow-up studies on structural modification of coptisine-type alkaloids and on anti-Ulcerative colitis drugs with coptisines.

A unified total synthesis of benzo[d][1,3]dioxole-type benzylisoquinoline alkaloids of aporphines, coptisines, and dibenzopyrrocolines.

The first total synthesis of (S)-(+)-ovigerine, (S)-(+)-N-formylovigerine, and (6aS,6a'S)-(+)-ovigeridimerine of aporphine alkaloids with a benzo[d][1,3]dioxole structure feature was established. The strategy was based upon the well-known Pd-catalyzed arylation to set the aporphine framework, and Noyori asymmetric hydrogenation followed by diastereoselective resolution to achieve excellent enantioselectivity. By slightly modifying the total synthetic route and strategically combining it with a aza-Michael addition, Bischler-Napieralski reaction and N-arylation, this methodology was also applied to the total syntheses of benzo[d][1,3]dioxole-type benzylisoquinoline alkaloids of coptisines and dibenzopyrrocolines, including two impatiens, tetrahydrocoptisine, and quaternary coptisine bromide of coptisines and two dibenzopyrrocoline analogues, with the syntheses of all of these target compounds being efficient. Among the nine synthesized compounds, the total syntheses of the three aporphines and the two impatiens, all with ee values of greater than 99%, were reported for the first time. This work also represents the first unification of synthetic routes for the total synthesis of benzo[d][1,3]dioxole-type aporphines, coptisines, and dibenzopyrrocolines.

Syntheses and Structure-Activity Relationships in Antibacterial Activity against Clostridium difficile and XBP1 Activation Property of 13-[(N-Alkylamino)methyl]-8-oxodihydrocoptisines.

13-[(N-Alkylamino)methyl]-8-oxodihydrocoptisines were synthesized to evaluate antibacterial activity against Clostridium difficile and activating x-box-binding protein 1 (XBP1) activity, biological properties both associated with ulcerative colitis. Improving structural stability and ameliorating biological activity were major concerns. Different substituents on the structural modification site were involved to explore the influence of diverse structures on the bioactivities. The target compounds exhibited the desired activities with definite structure-activity relationship. In the series of 13-[(N-n-alkylamino)methyl]-8-oxodihydrocoptisines, the length of n-alkyl groups has a definite effect on the bioactivity, elongation of the length increasing the antibacterial activity. The synthesized compounds were determined to display strong or weak XBP1-activating activity in vitro. The preliminary results of this study warrant further medicinal chemistry studies on these synthesized compounds.

Syntheses and Structure-Activity Relationships in Growth Inhibition Activity against Human Cancer Cell Lines of 12 Substituted Berberine Derivatives.

In this study, quaternary berberine chloride is used as a lead compound to design and synthesize a series of berberine-12-amine derivatives to evaluate the growth inhibition activity against human cancer cell lines. Forty-two compounds of several series were obtained. The quaternary berberine-12-N,N-di-n-alkylamine chlorides showed the targeted activities with the IC50 values of most active compounds being dozens of times those of the positive control. A significant structure-activity relationship (SAR) was observed. The activities of quaternary berberine-12-N,N-di-n-alkylamine chlorides are significantly stronger than those of the reduced counterparts. In the range of about 6-8 carbon atoms, the activities increase with the elongation of n-alkyl carbon chain of 12-N,N-di-n-alkylamino, and when the carbon atom numbers are more than 6-8, the activities decrease with the elongation of n-alkyl carbon chain. The activities of the tertiary amine structure are significantly higher than that of the secondary amine structure.

Racemic 3,4-dihydro-4-naphthyl-naphthalen-1(2H)-ones from Juglans regia flowers.

Three previously undescribed (±)-3,4-dihydro-4-naphthyl-naphthalen-1(2H)-one derivatives were isolated from Juglans regia flowers. Elucidation of the 2D structures of these first-reported compounds was completed via regular spectroscopic methods. The assignment of racemic nature of these compounds was achieved using the examination of their chiral HPLC profiles. (±)-2,3-Dihydro-4',8,8'-trihydroxy-(1,1'-binaphthalen)-4(1H)-one, (±)-2,3-dihydro-4',5,8,8'-tetrahydroxy-(1,1'-binaphthalen)-4(1H)-one, and (±)-2,3-dihydro-1',5,5',8-tetrahydroxy-(1,2'-binaphthalen)-4(1H)-one were the structures of these racemic compounds, all taking on central chirality. The resolution of all the racemic compounds was conducted and achieved using a chiral HPLC procedure. The absolute configurations of the three isolated pairs of enantiomers were assigned via time-dependent density functional theory calculations from the electronic circular dichroism data. The findings in this paper demonstrated that the relevant biochemical reactions for the construction of these 3,4-dihydro-4-naphthyl-naphthalen-1(2H)-one derivatives in the test plant are nonselective. The (±)-2,3-dihydro-4',8,8'-trihydroxy-(1,1'-binaphthalen)-4(1H)-one showed selective inhibitory activity on tumor cells growth, preliminarily supporting the application of Juglans regia flowers to protect against cancers in a few Chinese folk areas.

Re-engineering and synthesis of cytotoxic 2,3:7,8-di(alkylenedioxy)-extended analogs of quaternary sanguinarine chloride.

A method was developed to synthesize 2,3:7,8-di(alkylenedioxy)-extended analogs of quaternary sanguinarine chloride. 1-Bromo-2-bromomethyl-3,4-alkylenedioxy benzenes and 6,7-alkylenedioxynaphthalen-1-amines were synthesized first. Reactions to construct the target compounds with these two series of synthons involved alterations on a published method for synthesizing 2,3,7,8-tetraoxygenated derivatives of benzo[c]phenanthridinium, substituting benzyl bromides for benzoic aldehydes, prolonging the radical annulation time, and conducting N-methylation with formic acid and NaBH4. All the target compounds showed the same or better in vitro growth inhibitory activities against cancer cell lines compared with the positive compound. The structure activity relationship relevant to cytotoxicity and lipophilicity of the target compounds was produced.

Syntheses and structure-activity relationships on antibacterial and anti-ulcerative colitis properties of quaternary 13-substituted palmatines and 8-oxo-13-substituted dihydropalmatines.

In this study, quaternary palmatine is used as a lead compound to design and synthesize derivatives to evaluate bioactivities, with twenty-seven compounds of four series being obtained. Antibacterial activity was examined by determining the minimal inhibitory concentration (MIC) values on Staphylococcus aureus, Escherichia coli, and Candida albicans, three series of derivatives being found to exhibit activity in vitro with significant structure-activity relationship (SAR). Elongating the carbon chain led to the antibacterial activity increased, with quaternary 13-hexanoylpalmatine chloride, quaternary 13-(ω-ethoxycarbonyl)heptylpalmatine chloride, and 8-oxo-13-(N-n-nonyl)aminomethyldihydropalmatine, all of which possess the longest aliphatic carbon chain in the corresponding series of derivatives, showing the MIC values of 62.5, 7.81, and 15.63 µg/ml against S. aureus, respectively. The property of anti-ulcerative colitis (anti-UC) was assessed at the levels of both in vitro and in vivo, with X-box-binding protein 1 (XBP1) being targeted in vitro. Seven compounds were found not only to be hypocytotoxic toward intestinal epithelial cells, but also to exhibit activity of activating the transcription of XBP1 in vitro. Five compounds were found to possess significant dose-effect relationship with EC50 values at a level of 10-7 µM in vitro. 8-Oxo-13-formyldihydropalmatine as an intermediate was found to display significant curative effect on UC in vivo based on the biomarkers of body weight change, colon length change, and calculated values of disease activity index and colon macroscopic damage index of the experimental animals, as well as the examination into the pathological changes of the colon tissue of the modeled animals.

Six scalemic mixtures of 6-monosubstituted dihydrobenzophenanthridine alkaloids from Chelidonium majus and optically active structures of enantiomers.

Six pairs of previously undescribed 6-monosubstituted dihydrobenzophenanthridine alkaloids were separated as corresponding six scalemic mixtures from the aerial part of Chelidonium majus. The elucidation for the 2D structures of these alkaloids was achieved using regular spectroscopic and chemical methods. The assignment of scalemic-mixture nature was achieved using combined examinations of their NMR data, CD spectra, calculation of specific rotations, and chiral HPLC profiles. The identification for the relative configurations of alkaloids possessing two asymmetric carbons directly connected up by a rotatable sp3-sp3 carbon-carbon single bond was significantly facilitated by discussing the erythro and threo relative configurations defined by the mutuality of the orders of decreasing steric hindrances between the two sets of ligands linked to the two chiral centers. Two scalemic mixtures were assigned as (1'R,6R/1'S,6S)- and (1'S,6R/1'R,6S)-1-(dihydrochelerythrine-6-yl)ethanols, two as (1'R,6R)/(1'S,6S)- and (1'S,6R)/(1'R,6S)-1-(dihydrosanguinarine-6-yl)ethanols, one as (±)-ethyl 2-(dihydrosanguinarine-6-yl)acetate, and one as (±)-ethyl dihydrosanguinarine-6-carboxylate, respectively. The resolution of three scalemic mixtures was achieved and the absolute configurations of the three pairs of enantiomers were assigned via time-dependent Density Functional Theory calculations of electronic circular dichroism (ECD) data. The assignment for the absolute configurations of the other three scalemic mixtures was achieved via a chiral HPLC-UV/CD method plus analyzing their ECD data. The findings of this paper demonstrated that the relevant biochemical reactions concerning the construction of these 6-monosubstituted dihydrobenzophenanthridine alkaloids in the test plant are very nonselective. Scalemic mixture of (1'R,6R)/(1'S,6S)-1-(dihydrosanguinarine-6-yl)ethanol exhibited biological activity. It inhibited the growth of human MDA-MB-231 cell line at a moderate level with IC50 value of 5.12 µM.