¹H NMR (500 MHz, DMSO) and ¹³C NMR (125 MHz, DMSO) spectral data for M-1 and M-2

No.	1α-Hydroxylcinobufagin (M-1)				5β-Hydroxylcinobufagin (M-2)
No.	¹H NMR	¹³C NMR	HMBC (H → C)	NOESY	¹H NMR	¹³C NMR
1	3.62 brs	71.8 d	C-2, C-10	H-5, Me-19	1.25	24.8 t
					1.70
2H_a H_b	1.93	32.0 t	C-1, C-3, C-4	H-3	1.48	27.2 t
	1.68			H-1	1.52
3	4.00 (brs)	66.7 d	C-2, C-4, C-5	H_a-2	3.02 (brs)	66.5 d
4H_a H_b	1.78	32.8 t	C-2, C-3, C-5, C-10	H-5	2.10 brd	36.5 t
	1.82
5	1.63	30.1 d	C-4, C-6, C-10	Me-19	—	73.5 s
6H_a H_b	1.32	25.0 t	C-5, C-8, C-10	H-5	1.15	33.8 t
	1.73				1.52
7H_a H_b	1.20	19.8 t	C-8, C-9	H-8	0.92	22.2 t
	1.33				1.39
8	1.87	32.8 d	C-9,C-11, C-14	Me-19	1.98	31.5 d
9	1.73	39.9 d	C-10, C-11, C-12, C-19	H_a-11	1.80	41.1 d
10		40.5 s				40.4 s
11H_a H_b	1.17	20.6 t	C-8, C-9, C-12, C-13	H-9	1.24	21.0 t
	1.40			H-19	1.50
12H_a H_b	1.48	38.7 t	C-9, C-11, C-13, C-18	H-18	1.41	38.8t
	1.65				1.65
13		44.6 s				44.3 s
14		71.9 s				71.9 s
15	3.75 (s)	59.3 d	C-14, C-16, C-17	H-16	3.75 (s)	59.3 d
16	5.45 (d, 9.5)	74.6 d	C-13, C15, C-25	H-15, H-17	5.42 (d, 9.5)	74.5 d
17	2.85 (9.5)	48.9 d	C-13, C-14, C-16, C-20	H-16	3.35 (d, 9.5)	48.8 d
18	0.71 (s)	16.9 q	C-12,C-13,C-14	H-8, H-21	0.62 (s)	16.5 q
19	0.99 (s)	18.7 q	C-1,C-5,C-10	H-1, H-5, H-8	0.91 (s)	16.8 q
20		116.1 s				116.1 s
21	7.48 (s)	152.2 d	C-20	Me-18	7.35 (s)	152.2 d
22	7.81 (brs)	148.6 d	C-20, C-23	H-23, H-26	7.80 (brs)	148.4 d
23	6.24 (d, 9.5)	112.9 d	C-22, C-24	H-22	6.23 (d, 9.5)	112.9 d
24		160.9 s				160.7 s
25		169.4 s				169.3 s
26	1.82 (s)	20.2 q	C-25	Me-18	1.81 (s)	20.2 q

DMSO, dimethyl sulfoxide; HMBC, heteronuclear multiple-bond correlation spectroscopy; NOESY, nuclear Overhauser effect spectroscopy.