Table 1.

The antioxidant activity of CGA isomers evaluated by chemical assays.

Chemical Assays	End-Point Measure	CGA Isomer	Concentration/Exposure Time	Results	References
DPPH assay	DPPH	5-CQA	5–80 μM for 3 h	10%~90% inhibition on DPPH	[51]
Xanthine/xanthine oxidase system	DMPO/·OOH adducts	5-CQA	20 μM for 2.5 min	↓ 30% ·OOH	[51]
FeSO4 + H2O2	DMPO/·OH adducts	5-CQA	20 μM for 2.5 min	↓ 51% ·OH	[51]
FeSO4 + H2O2	DMPO/·OH adducts	5-CQA	100–400 μM for 1 min	↓ 50% to 80% ·OH	[52]
ABTS assay	ABTS·+	5-CQA	Serials concentration for 15 min	The ability of 100 g of CGA in scavenging ABTS·+ is equivalent to 3.7 mmol Trolox	[53]
Rat brain homogenates + sodium nitroprusside	MDA	5-CQA	1.56–6.25 μg/mL	No significant inhibition of MDA	[53]
Liposome system containing AAPH	MDA	5-CQA	0.1–0.5 mM	Second order rate of constant of the reactions of LOO· with CGA is 1.28 ± 0.11 × 105 M−1·s−1	[54]
Pulse radiolysis to generate O2-	O2-	5-CQA	0.2–0.75 mM	Second order rate of constant of the reactions of O2- with CGA is 0.96 ± 0.01 × 106 M−1·s−1	[54]
Fenton-type reaction to generate ·OH	·OH	5-CQA	0.1–0.75 mM	Second order rate of constant of the reactions of ·OH with CGA is 3.34 ± 0.19 × 109 M−1·s−1	[54]
Potassium phosphate to generate ONOO-	ONOO-	5-CQA	80 μM	Second order rate of constant of the reactions of ONOO- with CGA is 1.6 ± 0.7 × 105 M−1·s−1	[54]
DPPH assay	DPPH	3-CQA,	5 μg/mL–60 μg/mL	EC50 a 3-CQA:13.4 μg/mL	[55]
		4-CQA,		4-CQA: 13.2 μg/mL
		5-CQA,		5-CQA: 13.8 μg/mL
		3,5-diCQA,		3,5-diCQA: 9.3 μg/mL
		3,4-diCQA,		3,4-diCQA: 9.4 μg/mL
		4,5-diCQA		4,5-diCQA: 7.5 μg/mL
ABTS assay	ABTS·+	3-CQA	50 μg/mL–150 μg/mL	EC50 a 3-CQA: 91.4 μg/mL	[55]
		4-CQA,		4-CQA: 87.5 μg/mL
		5-CQA,		5-CQA: 91.5 μg/mL
		3,5-diCQA,		3,5-diCQA: 77.6 μg/mL
		3,4-diCQA,		3,4-diCQA: 77.4 μg/mL
		4,5-diCQA		4,5-diCQA: 67.3 μg/mL
FRAP assay	Reducing power	3-CQA	25–125 μg/mL	4,5-diCQA > 3,5-diCQA > 3,4-diCQA > 5-CQA = 4-CQA = 3-CQA	[55]
		4-CQA,
		5-CQA,
		3,5-diCQA,
		3,4-diCQA,
		4,5-diCQA
DNA damage protective effect assay	DNA damage	3-CQA	50 μg/mL	↓ 43.1 to 62.4% DNA damage	[55]
		4-CQA,
		5-CQA,
		3,5-diCQA,		4,5-diCQA > 3,4-diCQA > 3,5-diCQA > 5-CQA > 4-CQA > 3-CQA
		3,4-diCQA,
		4,5-diCQA
Plasmid pUC18 + NH2Cl	Supercoiled DNA, nicked circular DNA and linear duple	5-CQA	0.01 mM–1.23 mM	Prevented a stepwise conversion of plasmid DNA form supercoiled DNA, nicked circular DNA and linear duplex DNA	[50]
LDL + copper	Conjugated dienes	5-CQA	0.25–1.0 μM	↑ lag time of LDL oxidation	[56]
LDL + metmyoglobin + H2O2	ROS	5-CQA	1 molar ratio to metmyoglobin	Effectively blocked LDL oxidation	[57]

^a EC₅₀ represents the concentration of the tested compound that results in half-maximal response.