Design, Synthesis, and Anti-inflammatory/Antioxidant Activities of Guaiazulene Dimers Bridged by Triethylene Glycol

doi:10.6023/A25060209

Abstract

Imbalanced release of inflammatory mediators can trigger various chronic diseases, and the development of highly effective anti-inflammatory drugs holds significant clinical value. The bridged dimerization of natural products can markedly enhance the bioactivity, selectivity, and stability of monomers. This study designed and synthesized guaiazulene (GA)-based dimers (BGA-E and BGA-T) linked via ester and ether bonds, with triethylene glycol as the spacer and the natural bicyclic sesquiterpene GA as the core structure. The anti-inflammatory and antioxidant activities of the new compounds were investigated in comparison with the reference compounds (GA and sodium guaiazulene sulfonate). The antioxidant capacity of the compounds was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and the ferric ion reducing antioxidant power (FRAP) assay. The inhibitory effects of the compounds on inflammatory factors were evaluated using the Griess method, conventional enzyme-linked immunosorbent assay (ELISA), and Western Blot analysis. Cytotoxicity was measured via the Cell Counting Kit-8 (CCK-8) assay. The results demonstrated that compound BGA-T effectively suppressed the release of the inflammatory cytokine interleukin-6 (IL-6) induced by lipopolysaccharide (LPS), reducing IL-6 secretion to 34.89% of the blank control group. Its inhibitory effect was 8-fold stronger than GA. Additionally, BGA-T exerted its anti-inflammatory effects by downregulating the expression of cyclooxygenase-2 (COX-II). None of the tested compounds exhibited significant cytotoxicity. This study provides new insights for the design of bridged dimers based on natural products and the development of anti-inflammatory drugs.

Key words: guaiazulene, triethylene glycol, anti-inflammatory, antioxidant, natural products

Cite this article

Diefeng Ren, Junjun Xiang, Xike Gao. Design, Synthesis, and Anti-inflammatory/Antioxidant Activities of Guaiazulene Dimers Bridged by Triethylene Glycol[J]. Acta Chimica Sinica, 2025, 83(10): 1174-1183.

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Fig. & Tab. 15

Figure 1. The structural formula of artemisinin-bridged dimers

Figure 2. Chemical structure of Guaiazulene

Scheme 1. Synthetic routes of BGA-E and BGA-T

Figure 3. 1H NMR spectra of compounds BGA-E and BGA-T

Figure 4. The scavenging rates of different concentrations of compounds against DPPH radicals at 0.5 h (a) and 4 h (b) Data are given as mean±standard error of mean (SEM). Statistical analysis is performed by oneway analysis of variance (ANOVA). **p<0.01

化合物	时间/h	自由基清除率^a/%
化合物	时间/h	50 μmol•L⁻¹	100 μmol•L⁻¹	200 μmol•L⁻¹	400 μmol•L⁻¹
BGA-E	0.5	12.86	14.25	18.90	24.13
BGA-E	4	14.19	16.58	23.58	31.91
BGA-T	0.5	11.25	12.06	12.70	17.52
BGA-T	4	13.35	14.72	14.83	24.44
GA	0.5	11.84	11.86	13.88	10.15
GA	4	12.35	12.51	13.91	12.03
GA-SO₃Na	0.5	10.86	10.95	10.40	9.20
GA-SO₃Na	4	11.23	11.64	11.24	9.69

Table 1. The scavenging rates of different concentrations of compounds against DPPH radicals at 0.5 h and 4 h

Figure 5. Measurement of OD values for compounds at different concentrations by FRAP assay Data are given as mean±SEM

化合物	OD值
化合物	50 μmol•L⁻¹	100 μmol•L⁻¹	200 μmol•L⁻¹	400 μmol•L⁻¹
BGA-E	0.0685	0.0827	0.1011	0.1389
BGA-T	0.1005	0.1503	0.2267	0.3357
GA	0.1084	0.1772	0.3135	0.5741
GA-SO₃Na	0.0955	0.1370	0.2090	0.3346

Table 2. Measurement of OD values for compounds at different concentrations by FRAP assay

Figure 6. NO inhibition rates of compounds at various concentrations in LPS-stimulated RAW 264.7 cells Data are given as mean±SEM. Statistical analysis is performed by Two-way analysis of variance (ANOVA). ****p<0.0001, ***p<0.001, **p<0.01 compared to GA and GA-SO3Na

化合物	浓度/(μmol•L⁻¹)	抑制率^a/%
BGA-E	10	16.60
	20	23.01
	40	36.23
	80	47.75
BGA-T	10	15.61
	20	28.57
	40	43.99
	80	57.92
GA	10	12.88
	20	19.52
	40	23.05
	80	27.19
GA-SO₃Na	10	4.49
	20	2.85
	40	6.18
	80	15.32
模型组	—	0

Table 3. NO inhibition rates of compounds at various concentrations in LPS-stimulated RAW 264.7 cells

Figure 7. The effect of different compounds on the relative amount of TNF-α (a) and IL-6 (b) in LPS-induced RAW 264.7 cells Data are given as mean±SEM. Statistical analysis is performed by Two-way analysis of variance (ANOVA). ****p<0.0001, ***p<0.001, **p<0.01 compared to GA and GA-SO3Na

化合物	浓度/ (μmol•L⁻¹)	相对含量^a/%
化合物	浓度/ (μmol•L⁻¹)	TNF-α	IL-6
BGA-E	20	101.71	88.40
	40	105.33	71.76
	80	139.79	45.83
BGA-T	20	94.47	79.25
	40	89.67	63.89
	80	77.14	34.89
GA	20	101.29	98.72
	40	114.84	95.28
	80	122.68	92.17
GA-SO₃Na	20	88.96	103.13
	40	84.68	96.59
	80	82.98	91.48
模型组	—	100.00	100.00

Table 4. The relative amounts of TNF-α and IL-6 in LPS-induced RAW 264.7 cells with the compounds

Figure 8. Western blot bands showing the effects of different compounds on COX-II expression in LPS-induced RAW 264.7 cells

Figure 9. The effect of different compounds on the relative amount of COX-II in LPS-induced RAW 264.7 cells Data are given as mean±SEM. Statistical analysis is performed by One-way analysis of variance (ANOVA). ****p<0.0001, ***p<0.001, **p<0.01 compared to DMSO

Figure 10. Effects of compounds on the cell viability of macrophage RAW 264.7 cells

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