Ethanolic Extract of Polish Propolis: Chemical Composition and TRAIL-R2 Death Receptor Targeting Apoptotic Activity against Prostate Cancer Cells

Table 1

The content (mg/g) and characterization of phenolic compounds of the ethanol extract of Polish propolis determined using their spectral characteristic in negative ions in LC-ESI/MS.

Peak	Retention time 𝑡𝑟 (min)	(M−H)^−	MS/MS fragments	Compound name*	Quantity (mg/g of propolis)**
1	2.26	179.0349	161.0241/135.0440	Caffeic acid^a	3.90
2	2.53	121.0288	121.0288	Benzoic acid^bc	0.86^d
3	2.69	237.0772	163.0406/145.0284/117.0342	Ni	Tr
4	2.79	163.0406	119.0488	𝑝-Coumaric acid^a	28.65
5	2.88	267.0899	160.0154/133.0276	Ni	Tr
6	3.01	193.0492	178.0258/149.0613/134.0375	Ferulic acid^a	22.01
7	3.18	357.0989	279.0655/147.0441	Ferulic acid derivative^c	0.59^e
8	3.31	295.0815	161.0241/133.0299	Ferulic acid derivative^c	Tr
9	3.57	359.1129	163.0380/145.0284/119.0510	Coumaric acid derivative^c	0.16^g
10	3.72	389.1221	193.0492/134.0375/175.0399/160.0154	Ferulic acid derivative^c	0.75^e
11	3.88	279.086	145.0284/117.0342	Ni	Tr
12	4.15	415.1065	253.0730/179.0349/161.0241/135.0440	Caffeic acid derivative^c	0.11^f
13	4.27	355.1176	179.0349/163.0380/135.0440/119.0488	Caffeic and coumaric acids derivative^c	Tr
14	4.61	399.1051	253.0697/179.0349/163.0380/119.0488	Coumaric and caffeic acids derivative^c	1.83^g
15	4.70	429.1214	253.0697/193.0492/161.0241/134.0375	Ferulic acid derivative^c	2.12^e
16	4.86	269.0469	151.0042/117.0342	Apigenin^a	1.98
17	4.96	383.1137		Coumaric acid derivative^c	3.97^g
18	5.05	271.0616	253.0502/197.0596/161.0605/125.0241/107.0134	Pinobanksin^a	12.78
19	5.10	383.1137	163.0406/119.0510	Coumaric acid derivative^c	22.87^g
20	5.20	413.1240	193.0492/163.0380/134.0375/119.0488	Coumaric and ferulic acids derivative (metoxy-)^c	13.44^e
21	5.27	443.1320	193.0492/163.0380/134.0375/119.0488	Coumaric and ferulic acids derivative (dimetoxy-)^c	3.98^e
22	5.44	259.1917	193.0492/163.0380/134.0375/119.0489	Ferulic acid derivative^c	2.02^e
23	5.63	283.0594	193.0492/134.0375	Ferulic acid derivative^c	0.3^e
24	5.73	441.1179	179.0349/163.0406/135.0440/119.0388	Caffeic and coumaric acids derivative^c	Tr
25	5.79	315.0512	121.0288	Rhamnetin^a	0.49
26	5.86	471.1305	297.1136/193.0492	Ni	Tr
27	6.25	425.1242	163.0406/119.0510	Coumaric acid derivative^c	5.00
28	6.32	247.0982	179.0349/163.0380/135.0440	Coumaric and caffeic acids derivative^c	0.31^f
29	6.35	253.0502	143.0510	Chrysin^a	6.56
30	6.41	269.0804	178.0258/163.0380/134.0375/119.0488	Ni	—
31	6.56	269.0435	171.0446/151.0042/117.0342	Galangin^a	0.47
32	6.56	299.0572		Kaempferide^g	Tr
33	6.66	313.0745	253.0502	Pinobanksin-3-O-acetate^b	Tr
34	6.94	249.1131	161.0241/133.0299	Ni	—
35	7.13	253.0860	162.0308/151.0394/145.0284/117.0342	Methoxyflavanone^bc	20.50^h
36	7.25	283.0973	163.0380/145.0653/119.0488	Coumaric acid derivative^c	10.49^g
37	8.80	449.2537	361.2026/253.0502/121.0288	Benzoic acid derivative^c	5.20^d

Ni: not identified.
Tr: traces.
*a: confirmed by standard; b: confirmed by reference [41, 42]; c: confirmed by MS fragmentation.
**d: expressed as cinnamic acid; e: expressed as ferulic acid; f: expressed as caffeic acid; g: expressed as 𝑝-coumaric acid; h: expressed as apigenin.