Table 1. Comparison of the chemical composition of the outer bark of Quercus variabilis and Quercus suber across different regions

	Q. variabilis		Q. suber
	Republic of Korea	China	Portugal	Italy
Ash	0.82 (± 0.03)^a	0.56 (± 0.02)^b	1.99 (± 0.12)^a	1.82 (± 0.63)^a
Total extractive	10.12 (± 1.49)^a	11.18 (± 0.07)^a	13.65 (± 0.22)^a	9.68 (± 1.42)^a
CH₂Cl₂	1.22 (± 0.23)^c	6.18 (± 0.08)^b	3.26 (± 0.17)^a	3.25 (± 1.29)^a
EtOH	4.38 (± 0.52)^a	2.37 (± 0.31)^b	5.53 (± 0.14)^a	5.83 (± 0.80)^a
H₂O	4.52 (± 0.90)^a	2.63 (± 0.46)^a	4.86 (± 0.41)^a	0.60 (± 0.52)^b
Suberin	50.19 (± 1.45)^a	44.12 (± 1.63)^a	30.09 (± 2.33)^b	47.63 (± 1.53)^a
Total lignin	18.65 (± 0.30)^a	21.80 (± 0.17)^b	24.90 (± 0.39)^c	19.42 (± 0.36)^a
Klason lignin	18.31 (± 0.22)^a	20.30 (± 0.25)^b	24.57 (± 0.45)^a	19.22 (± 0.41)^a
Acid-Soluble lignin	0.34 (± 0.12)^a	1.50 (± 0.08)^b	0.33 (± 0.08)^a	0.20 (± 0.10)^a
Polysaccharide	17.11 (± 0.37)^a	20.38 (± 0.42)^a	27.46 (±0.56)^a	20.12 (± 0.47)^a
Monosaccharide
Glucose	7.36 (± 0.49)^a	8.13 (± 0.76)^a	13.20 (± 0.44)^a	9.77 (± 0.64)^a
Galactose	1.31 (± 0.50)^a	1.94 (± 0.36)^a	1.82 (± 0.47)^a	1.17 (± 0.71)^a
Xylose	5.09 (± 0.73)^a	5.47 (± 0.62)^a	9.30 (± 0.67)^b	6.72 (± 0.43)^a
Arabinose	3.33 (± 0.85)^a	4.85 (± 1.62)^a	3.14 (± 0.35)^a	2.55 (± 0.40)^a
Total content	96.89 (± 0.73)	98.04 (± 0.46)	98.09 (± 0.72)	98.76 (± 0.88)

Values are expressed as mean ± SD.
Different superscript letters within the same row indicate statistically significant differences among groups (p < 0.05, one-way ANOVA, Tukey’s HSD).
ANOVA: analysis of variance, HSD: honest significant difference.