Antioxidant Characterization of Oak Extracts Combining Spectrophotometric Assays and Chemometrics

Table 2

Protein content, DPPH, NO, and O₂^•−-antiradical powers, permanganate reducing antioxidant capacity, ferric reducing antioxidant power, and lipid peroxidation in oak twigs, leaves, and acorns of two Serbian oak species Quercus robur L. and Quercus petraea L.

Plant organ	Locality	Prot. (mg/g)	DPPH-ARP ((1/IC50)⋅100)	NO-ARP ((1/IC50)⋅100)	O2^•−-ARP ((1/IC50)⋅100)	PRAC (A50)	FRAP (FRAP units)	LP (nmol/mg prot.)
Twigs	Q. robur	52.45^a	5.874^a	0.358^a	2.174^a	0.016^a	141.54^a	67.18^a
	Q. petraea	103.9^b	4.039^b	0.241^b	3.571^b	0.010^a	178.5^a	28.08^b
Leaves	Q. robur	427.0^c	7.628^c	0.531^c	3.448^b	0.304^b	873.8^b	11.01^c
	Q. petraea	159.6^d	8.779^d	0.400^d	4.785^c	0.235^c	1252.3^c	11.96^c
Acorns	Q. robur	352.1^e	9.066^d	0.188^e	5.359^d	0.411^d	370.0^d	3.282^d
	Q. petraea	95.60^b	6.734^e	0.202^e	4.098^e	0.543^e	614.6^e	2.023^d

∗Values with the same letter, in each colon, are not significantly different according to Duncan test (𝑃<0.05).
**Prot.: proteins; ARP: antiradical power; ARP = ((1/IC₅₀)⋅100); IC₅₀: the concentration of an sample at which 50% inhibition of free radical activity is observed; PRAC: permanganate reducing antioxidant capacity; A₅₀: antioxidant activity reflected in time until the sample induces a decrease of the oxidizing agent (potassium permanganate) up to one half, compared against a standard (ascorbic acid); A₅₀ = mmol ascorbate eq./g; FRAP: ferric reducing antioxidant power; 1 FRAP unit = 100 μmol/dm³ Fe²⁺; LP: lipid peroxidation.