Antioxidant Capacity and Proanthocyanidin Composition of the Bark of Metasequoia glyptostroboides

Table 2

Relationship between free radical scavenging, antioxidant activities, and the content of total phenolic, flavonoid, and proanthocyanidin of the extracts and fractions from the bark of M. glyptostroboides.

	𝑅
	Total phenolics	Total flavonoids	Total proanthocyanidins
DPPH radical scavenging capacity	0.9127	0.9114	0.9311
Hydroxyl radical scavenging capacity	0.8244	0.7679	0.9242
Superoxide anion radical scavenging capacity	0.8710	0.8251	0.9626
Total antioxidant capacity	0.9319	0.9215	0.9430
Lipid peroxidation inhibitory activity	0.4521	0.4665	0.6941
Fe^2+ chelating activity	0.6932	0.7387	0.7662

The contents of total phenolics, flavonoids, and proanthocyanidins were expressed as gallic acid equivalents (mg GAE/g sample), rutin equivalents (mg RE/g sample), and proanthocyanidin equivalents (mg PE/g sample). The DPPH, hydroxyl, superoxide anion radical scavenging capacity and total antioxidant capacity were calculated as gram ascorbic acid equivalents per gram sample (g ascorbic acid eq./g). The lipid peroxidation inhibitory activity and Fe²⁺ chelating activity were calculated as half inhibitory concentration (IC₅₀) value. Each regression line and correlation coefficient (𝑅) were analyzed by the correlation and regression program in Microsoft Office Excel.