Second generation β-elemene nitric oxide derivatives with reasonable linkers: potential hybrids against malignant brain glioma

Figures & data

Figure 1. The structure of β-elemene and its clinical preparations.

Figure 2. (A) The allylicchlorination reaction of β-elemene and the corresponding reaction products 2–4. (B) The designing strategy of β-elemene NO donor hybrids.

Figure 3. In vivo metabolizion of 13-β-elemenol ester NO donor derivatives may result in producing toxic 13-β-elemenal.

Scheme 1. Reagents and conditions: DIPEA, DMF, 60 °C.

Scheme 2. Reagents and conditions: (a) THF, NaOH (4:1, v/v), r.t.; (b) DMAP, DCM, r.t.

Scheme 3. Reagents and conditions: EDCI, DMAP, DCM, r.t.

Table 1. NO-release concentrations of β-elemene derivatives at 100 μM.

Compounds	Concentrations of NO at seven-time points (Mean ± SD, μM)
	5 min	10 min	20 min	30 min	60 min	90 min	120 min
Ia	1.73 ± 0.06	2.31 ± 0.09	2.90 ± 0.41	4.04 ± 0.05	7.76 ± 0.18	12.67 ± 0.59	17.21 ± 0.35
Ib	2.10 ± 0.20	2.40 ± 0.02	2.84 ± 0.10	3.79 ± 0.11	6.74 ± 0.30	10.72 ± 1.00	14.97 ± 0.59
Ic	10.78 ± 0.10	12.02 ± 0.64	15.83 ± 0.43	19.79 ± 0.14	32.99 ± 0.56	48.39 ± 1.26	58.84 ± 0.44
Id	12.53 ± 0.08	14.80 ± 0.26	19.55 ± 0.48	23.65 ± 0.92	42.31 ± 0.79	66.97 ± 1.53	93.18 ± 0.50
IIa	0.59 ± 0.08	41.61 ± 1.28	48.58 ± 1.54	2.57 ± 0.02	5.58 ± 1.25	9.22 ± 0.56	13.64 ± 0.63
IIb	3.38 ± 0.28	5.87 ± 2.84	4.62 ± 0.19	6.22 ± 0.14	9.97 ± 0.33	15.53 ± 0.86	20.60 ± 0.54
IIc	5.68 ± 0.07	7.17 ± 0.63	9.51 ± 1.00	9.04 ± 2.53	20.74 ± 0.44	30.04 ± 1.34	40.44 ± 0.43
IId	10.55 ± 0.19	12.34 ± 0.72	15.52 ± 0.79	18.95 ± 1.01	29.50 ± 0.79	43.00 ± 0.72	55.33 ± 0.46
IIIa	3.25 ± 0.12	3.90 ± 0.41	5.98 ± 0.57	7.59 ± 0.45	11.11 ± 0.74	17.29 ± 0.29	23.48 ± 0.27
IIIb	8.39 ± 0.10	9.44 ± 0.29	10.65 ± 0.63	12.22 ± 0.31	18.15 ± 0.56	26.49 ± 0.05	34.97 ± 0.06
IIIc	9.49 ± 0.25	10.79 ± 1.24	14.43 ± 0.77	15.97 ± 1.48	24.58 ± 1.10	37.37 ± 0.53	50.99 ± 0.01
IIId	13.20 ± 0.43	16.04 ± 0.20	21.29 ± 0.79	26.90 ± 1.11	46.58 ± 1.17	74.45 ± 1.89	103.92 ± 0.53
IVa	11.09 ± 0.11	12.18 ± 0.07	14.69 ± 0.10	17.14 ± 0.10	25.80 ± 0.16	38.78 ± 0.29	51.94 ± 0.62
IVb	12.34 ± 0.04	13.53 ± 0.64	15.94 ± 0.14	18.96 ± 0.07	29.94 ± 0.90	45.42 ± 1.59	62.49 ± 1.97
IVc	8.67 ± 0.13	10.07 ± 0.61	12.98 ± 0.23	15.92 ± 0.25	25.47 ± 1.41	36.31 ± 0.96	48.15 ± 1.23
IVd	16.97 ± 0.47	18.93 ± 0.28	22.62 ± 0.03	27.04 ± 0.13	42.47 ± 0.156	64.24 ± 0.92	86.29 ± 1.33
Va	4.84 ± 0.22	5.66 ± 0.33	6.95 ± 0.17	8.44 ± 0.17	12.43 ± 0.20	17.81 ± 0.41	22.91 ± 0.58
Vb	8.89 ± 0.05	10.18 ± 0.28	12.42 ± 0.92	14.32 ± 0.56	21.50 ± 0.89	32.40 ± 1.44	42.83 ± 1.22
Vc	13.76 ± 0.60	15.87 ± 0.01	19.21 ± 0.43	22.88 ± 0.45	34.60 ± 0.88	48.73 ± 0.61	56.52 ± 1.58
Vd	15.19 ± 0.20	17.57 ± 0.96	21.31 ± 0.45	25.52 ± 0.79	39.29 ± 1.17	58.12 ± 1.32	77.28 ± 1.14
VIa	0.08 ± 0.04	0.41 ± 0.22	0.99 ± 0.36	1.64 ± 0.43	2.98 ± 0.48	6.43 ± 0.07	10.20 ± 0.17
VIb	0.33 ± 0.13	0.89 ± 0.07	1.35 ± 0.00	1.91 ± 0.16	4.05 ± 0.36	7.20 ± 0.21	10.51 ± 0.29
VIc	4.74 ± 0.07	5.95 ± 0.59	7.49 ± 1.22	7.63 ± 0.88	8.44 ± 1.76	13.57 ± 0.66	17.82 ± 1.74
VId	10.64 ± 0.07	11.37 ± 0.63	12.38 ± 0.15	13.68 ± 0.36	18.24 ± 0.17	25.90 ± 0.28	34.64 ± 0.06

Table 2. Proliferation inhibition of β-elemene and β-elemene derivatives at 1 μM.

Compounds	Inhibitory rate ± SEM (%, 1 μM)
	SW620	U87MG	NCI-H520
β-elemene	2.5 ± 4.1	4.3 ± 2.2	3.2 ± 0.7
13,14-bischloro-β-elemene	3.3 ± 1.0	3.5 ± 1.0	0.9 ± 3.0
Ia	30.7 ± 3.5	39.5 ± 2.1	28.8 ± 0.8
Ib	42.3 ± 3.7	56.0 ± 2.1	48.5 ± 3.0
Ic	30.1 ± 5.2	34.9 ± 0.6	35.0 ± 2.2
Id	47.5 ± 3.7	55.5 ± 1.9	48.7 ± 2.0
IIa	33.0 ± 2.5	47.1 ± 0.9	44.2 ± 1.3
IIb	35.6 ± 2.8	54.3 ± 1.3	43.4 ± 1.5
IIc	46.6 ± 1.2	56.7 ± 0.9	44.5 ± 2.2
IId	10.8 ± 3.2	4.5 ± 1.0	5.6 ± 1.6
IIIa	39.3 ± 4.2	51.3 ± 1.3	44.5 ± 2.8
IIIb	45.9 ± 3.9	53.1 ± 1.4	46.7 ± 2.0
IIIc	30.5 ± 3.3	42.0 ± 6.5	46.0 ± 1.0
IIId	31.7 ± 1.4	47.8 ± 1.1	39.1 ± 0.7
IVa	53.6 ± 2.4	52.6 ± 1.7	48.5 ± 2.5
IVb	55.4 ± 1.5	54.8 ± 1.9	50.1 ± 1.1
IVc	31.3 ± 0.3	40.5 ± 3.3	45.9 ± 1.4
IVd	39.8 ± 1.9	52.2 ± 3.4	52.3 ± 1.1
Va	38.3 ± 3.0	51.0 ± 2.2	45.4 ± 1.9
Vb	46.1 ± 0.9	48.3 ± 1.5	43.9 ± 1.0
Vc	40.6 ± 2.8	41.9 ± 1.1	46.1 ± 2.7
Vd	43.2 ± 1.8	53.9 ± 0.6	44.5 ± 2.4
VIa	43.6 ± 2.5	52.6 ± 1.0	47.3 ± 2.6
VIb	42.8 ± 0.5	52.4 ± 2.0	44.1 ± 2.4
VIc	21.2 ± 2.1	33.4 ± 1.5	30.3 ± 2.9
VId	43.2 ± 5.5	50.3 ± 1.2	46.8 ± 2.1

Table 3. IC₅₀ values of compounds against threes tumour cell lines.

Compounds	IC50 ± SEM (μM)
	SW620	U87MG	NCI-H520
β-elemene	>100	>100	>100
13,14-bischloro-β-elemene	>100	>100	>100
Ib	–	0.358 ± 0.023	0.777 ± 0.024
Id	0.858 ± 0.033	0.369 ± 0.013	0.719 ± 0.017
IIa	–	0.369 ± 0.025	–
IIb	–	0.366 ± 0.019	–
IIc	1.111 ± 0.115	0.882 ± 0.034	–
IIIa	–	0.323 ± 0.013	–
IIIb	1.022 ± 0.09	0.343 ± 0.029	0.848 ± 0.053
IIIc	–	–	1.019 ± 0.041
IIId	–	0.898 ± 0.054	–
IVa	1.069 ± 0.101	1.119 ± 0.022	1.301 ± 0.043
IVb	0.814 ± 0.068	0.477 ± 0.011	0.846 ± 0.027
IVc	–	–	1.038 ± 0.033
IVd	–	2.160 ± 0.548	1.046 ± 0.013
Va	1.088 ± 0.04	0.811 ± 0.016	–
Vb	–	–	1.212 ± 0.152
Vc	–	0.985 ± 0.012	–
Vd	–	1.114 ± 0.052	1.175 ± 0.066
VIa	–	0.926 ± 0.052	–
VIb	–	0.372 ± 0.006	0.962 ± 0.054
VId	–	0.960 ± 0.075	1.062 ± 0.002

Figure 4. The anti-tumour activity of β-elemene and compound Id against brain malignant glioma (n = 5). (A) Body weight (model group as 100%). (B) Brain weight. (C) Boluminescence signal intensity of brain tumour. (D) Inhibitory rates of β-elemene and compound Id from week 1 to week 3. (E) Representative brain glioma images of the model, β-elemene, and compound Id groups. (F) Histological analysis of the brain glioma tumour tissue (**P < 0.01 vs. model group; ^##P < 0.01 vs. β-elemene group).