Figure 1.
Structures of the major gingerols and shogaols in ginger; and key HMBCcorrelations of thiol-conjugates M1, M2, and M4; and key 1H-1H COSY and HMBC correlations of M13.
Figure 2.
Synthesis of thiol-conjugates M1, M2, M4, M5, and M13.
Reagents and conditions: i) L-cysteine, NaHCO3 (cat.), MeOH/H2O, rt, 24 h; ii) NaBH4, MeOH, 0°C, 2 h; iii) N-acetyl-L-cysteine, NaHCO3 (cat.), MeOH/H2O, rt, 72 h; iv) L-glutathione reduced, NaHCO3 (cat.), MeOH/H2O, rt, 3 h.
Figure 3.
Synthesis of metabolites M6–M12.
Reagents and conditions: i) H2, Pd/C (10% w/w), THF, rt, 18 h; ii) BBr3, DCM, −78°C -rt, 2 h; iii) NaBH4, MeOH, 0°C -rt, 2 h; iv) aq. 15% NaSCH3, THF, rt, 6 h; v) Na, MeOH, 0°C -rt, 4 h; vi) NaBH4, CeCl3.7H2O, MeOH, −78°C, 30 min.
Figure 4.
Key NOESY correlations in M13-1 and M13-2 and the major differences of the 1H and 13C NMR data of M13-1 and M13-2.
Figure 5.
Growth inhibitory effects of [6]-shogaol and its metabolites (M1, M2, and M4–M13) against human colon cancer cells HCT-116 and human normal colon cells CCD-18Co.
Bar, standard error (n = 6).
Figure 6.
Growth inhibitory effects of [6]-shogaol and its metabolites (M1, M2, and M4–M13) against human colon cancer cells H-1299 and human normal lung cells IMR-90.
Bar, standard error (n = 6).
Figure 7.
Growth inhibitory effects of [6]-shogaol, M13, M13-1, M13-2, and a physical mixture of M13-1 and M13-2 (molar/molar = 1∶2) against human colon cancer cells HCT-116.
Bar, standard error (n = 6).
Figure 8.
Effects of [6]-shogaol and its metabolites M2, M6, and M13 on the induction of apoptosis in HCT-116 (A) and H-1299 (B) cells after 24 hours of incubation; and effects of [6]-shogaol, M2, M13, M13-1 and M13-2 on the induction of apoptosis in HCT-116 after 6 hours of incubation (C).
TUNEL positive cells have been observed at 400X power. 10 fields per slide have been counted and averaged. Bar, standard error; o, not significant; +, p<0.05; *, p<0.01; **: P<0.0001. All statistical tests are unpaired Student t-test, 2 tailed, compared to DMSO or the corresponding [6]-shogaol concentration.