Synthesis and Antileukemia Activity Evaluation of Benzophenanthridine Alkaloid Derivatives

Abstract

Thirty-three benzophenanthridine alkaloid derivatives (1a-1u and 2a-2l) were synthesized, and their cytotoxic activities against two leukemia cell lines (Jurkat Clone E6-1 and THP-1) were evaluated in vitro using a Cell Counting Kit-8 (CCK-8) assay. Nine of these derivatives (1i-l, 2a, and 2i-l) with IC₅₀ values in the range of 0.18-7.94 μM showed significant inhibitory effects on the proliferation of both cancer cell lines. Analysis of the primary structure-activity relationships revealed that different substituent groups at the C-6 position might have an effect on the antileukemia activity of the corresponding compounds. In addition, the groups at the C-7 and C-8 positions could influence the antileukemia activity. Among these compounds, 2j showed the strongest in vitro antiproliferative activity against Jurkat Clone E6-1 and THP-1 cells with good IC₅₀ values (0.52 ± 0.03 μM and 0.48 ± 0.03 μM, respectively), slightly induced apoptosis, and arrested the cell-cycle, all of which suggests that compound 2j may represent a potentially useful start point to undergo further optimization toward a lead compound.

Keywords: Zanthoxylum nitidum; antileukemia activity; benzophenanthridine alkaloid derivatives; cell cycle and apoptosis; synthesis.

Figure 1

The structures of chelerythrine (1), sanguinarine (2), and bocconoline.

Figure 2

Reagents and reaction conditions: (i) TMSCN, DMAP, DCM, reflux, 14 h; (ii) NaBH_4, MeOH, r.t., 0.5 h; (iii) CH₃CN, r.t., 3–8 h; (iv) ethyl trimethylsilylacetate, CsF, CH₃CN, r.t., 4–5 h; (v) LiAlH₄, THF, 5 °C, 0.5 h; (vi) CH₃CN, r.t., 3–4 h; (vii) CH₃CN, r.t., 5–14 h; (viii) CH₃COCH₃, 20% Na₂CO₃, reflux, 24 h; (ix) PhCOOH, piperidine, toluene, reflux, 24 h.

Figure 3

Compound 2j induced apoptosis in Jurkat Clone E6-1 and THP-1 cell lines. (A) Compound 2j induced apoptosis in Jurkat Clone E6-1 cell line. Jurkat Clone E6-1 cells were treated with 0.25, 0.5, and 1.0 µM of compound 2j for 48 h, and cells were subsequently stained with Annexin V–FITC/PI and subsequently analyzed by flow cytometry. (B) Compound 2j induced apoptosis in THP-1 cell line. THP-1 cells were treated with 0.25, 0.5, and 1.0 µM of compound 2j for 48 h, and cells were subsequently stained with Annexin V–FITC/PI and subsequently analyzed by flow cytometry. All data are presented as means ± SD (n = 3); *** p < 0.001 vs. the control group.

Figure 4

Effects of compound 2j on Jurkat Clone E6-1 and THP-1 cell-cycle. (A) The cell-cycle distribution of Jurkat Clone E6-1 using flow cytometry. (B) The percentage of Jurkat Clone E6-1 cells in the G₀/G₁ phase. (C) The percentage of Jurkat Clone E6-1 cells in the S phase. (D) The percentage of Jurkat Clone E6-1 cells in the G₂/M phase. (E) The cell-cycle distribution of THP-1 using flow cytometry. (F) The percentage of THP-1 cells in the G₀/G₁ phase. (G) The percentage of THP-1 cells in the S phase. (H) The percentage of THP-1 cells in the G₂/M phase. All data are presented as means ± SD (n = 3); * p < 0.05 and *** p < 0.001 vs. the control group.

Figure 4

Effects of compound 2j on Jurkat Clone E6-1 and THP-1 cell-cycle. (A) The cell-cycle distribution of Jurkat Clone E6-1 using flow cytometry. (B) The percentage of Jurkat Clone E6-1 cells in the G₀/G₁ phase. (C) The percentage of Jurkat Clone E6-1 cells in the S phase. (D) The percentage of Jurkat Clone E6-1 cells in the G₂/M phase. (E) The cell-cycle distribution of THP-1 using flow cytometry. (F) The percentage of THP-1 cells in the G₀/G₁ phase. (G) The percentage of THP-1 cells in the S phase. (H) The percentage of THP-1 cells in the G₂/M phase. All data are presented as means ± SD (n = 3); * p < 0.05 and *** p < 0.001 vs. the control group.