Evaluation of the antioxidant activity of several naturally occurring coumarins and their synthesized analogues by “ferric reducing antioxidant power” assay

Figures & data

Table 1.  Structures and FRAP values at 4 and 60 min (±SD) of tested compounds..

No	Compound	R1	R2	R3	R4	R5	R6	FRAP value at 4 min (μM)	FRAP value at 60 min (μM)
1	Scopoletin	H	H	H	OMe	OH	H	19.8 ± 3.6	38.6 ± 6.1
2	4-OH-coumarin	H	OH	H	H	H	H	∼0	2.85 ± 1.1
3	Umbelliferon	H	H	H	H	OH	H	∼0	∼0
4	Scopolin	H	H	H	OMe		H	∼0	∼0
5	BHC-1 (hymecromon)	H	Me	H	H	OH	H	∼0	∼0
6	753	H	Me	H	H	OH	OH	20.3 ± 3.3	43.9 ± 5.9
7	784	CH2COOC2H5	Me	H	H	OH	OH	22.2 ± 1.6	45.4 ± 6.2
8	476	CH2CH2COOC2H5	Me	H	H	OH	OH	31.4 ± 5.3	71.4 ± 0.8
9	813	H	Me	H	OH	OH	H	38.3 ± 0.9	72.8 ± 5.2
10	777	H	Me	OH	H	OH	H	∼0	∼0
11	786	CH2COOC2H5	Me	OH	H	OH	H	0.3 ± 0.1	9.7 ± 0.4
12	779	CH2CH2COOC2H5	Me	OH	H	OH	H	0.28 ± 0.03	9.52 ± 0.7
13	730	H	Me	H	H	OAc	OAc	0.11 ± 0.01	3.4 ± 0.05
14	821	CH2COOC2H5	Me	H	H	OAc	OAc	0.29 ± 0.03	5.4 ± 0.05
15	796	CH2CH2COOC2H5	Me	H	H	OAc	OAc	7 ± 2.1	15.4 ± 1.3
16	764	CH2CH2COOC2H5	Me	OAc	H	OAc	H	∼0	2.5 ± 0.5
17	823	H	Me	H	H	OMe	OMe	∼0	∼0
18	827 (Trigocoumarin)	CH2COOC2H5	Me	H	H	OMe	OMe	∼0	∼0
19	733	H	Me	OMe	H	OMe	H	∼0	∼0
20	825	CH2COOC2H5	Me	OMe	H	OMe	H	∼0	2.5 ± 0.4
21	801	H	Me	OMe	OAc	OMe	H	∼0	2.5 ± 0.5
22	864							13.7 ± 1.5	25.5 ± 3.8
23	Trolox							19.3 ± 1.2	20.2 ± 1.4
24	(+)-Catechin							20.73 ± 0.3	44.1 ± 1.05
25	Quercetin							66.9 ± 5.2	98.3 ± 4.8

The FRAP values were calculated according to formula described in the “Materials and methods” section.

Figure 1. The results of FRAP values at 4 and 60 min of tested coumarins (±SD). The measured values are presented in Table 1.

Figure 2. Absorbance changes at 595 nm at different time intervals in the presence of some active tested compounds (10 µM) and the absorbance change of Fe²⁺ (10 µM) in the FRAP assay.

Figure 3. Dependence of absorbance change at 595 nm after 4 min on the concentration of the most reducing active compound 6,7-dihydroxy-4-methylcoumarin (9) assayed by the FRAP method.