Evaluation of the cytotoxic potential of a new pentacyclic triterpene from Rhododendron arboreum stem bark

Figures & data

Table 1. ¹H and ¹³C NMR of 15-oxoursolic acid (1) [500 MHz (¹H NMR) and 125 MHz (¹³C NMR), CDCl_3, δ in ppm, J in Hz].

C. No.	δC	δH/ppm (multi, integral, J/Hz)	HMBC
1	38.61	1.37, 1.62 m	C3
2	28.01	1.84, 0.92 m
3	79.04	3.2 dd (5.0, 10.0)	C2, C24
4	38.75	–
5	55.22	0.77 d (10.0)
6	18.2	1.35.1.53 m
7	30.6	1.65,1.71 m
8	39.5	–
9	47.5	1.49m
10	37.1	–
11	23.3	0.93 t (10), 1.91 dd (5,10)	C12, C13
12	125.9	5.24 s	C10, C11, C14
13	137.9	–
14	42.0	–
15	212.1	–
16	36.7	1.65 m, 2.15 s	C15, C28
17	47.9	–
18	52.7	2.18 d (15.0)	C13, C13, C28
19	38.8	0.84 d (5)
20	39.0	1.63 m
21	24.2	1.64, 1.89 m
22	32.4	1.36, 1.46 m
23	28.1	1.06 s
24	15.6	0.72 s	C3, C4, C5
25	15.4	0.87 s
26	17.1	0.80 s
27	23.5	1.06 s	C8, C14
28	181.4	–
29	17.0	0.77 d (5)
30	21.1	0.84 d (10)

Figure 1. Structure of compound 1.

Figure 2. Important HMBC correlation of compound 1.

Figure 3. NOESY and COSY correlation.

Table 2. Anti-cancer activity of 15-oxoursolic acid (1).

Cancer cell line	IC50 (μM)
Squamous cell carcinoma (H157)	9.2 ± 0.23
Renal cell carcinoma (A498)	32.8 ± 1.54
Human hepatocellular carcinoma (Hep G2)	4.9 ± 0.02
Non-small cell lung (NCI-H226)	10.3 ± 0.01
Human ovarian carcinoma (MDR 2780AD)	2.3 ± 0.04

SEM: standard error mean of three experiments.