Effect of Extraction Conditions on the Antioxidant Activity of Olive Wood Extracts

Table 3

Extraction yields and radical scavenging percentages of several extracts prepared by the extraction procedure E7 from the olive wood sample A.

Extract^a	Pretreatment^b	Time^c	Reextracted material^d	Yield^e	RSP ± SD^f
A21	H2SO4 in H2O	1 h	Acidic extract	29.2	49.7 ± 0.6
A22	H2SO4 in H2O	1 h	Pre-treated wood	8.8	37.4 ± 0.1
A23	H2SO4 in H2O	3 h	Acidic extract	23.6	49.6 ± 0.8
A24	H2SO4 in H2O	3 h	Pre-treated wood	4.7	59.6 ± 0.4
A25	H2SO4 in H2O	5 h	Acidic extract	34.8	49.2 ± 0.9
A26	H2SO4 in H2O	5 h	Pre-treated wood	5.5	59.6 ± 1.6
A27	H2SO4 in H2O : EtOH	1 h	Acidic extract	25.7	54.0 ± 1.3
A28	H2SO4 in H2O : EtOH	1 h	Pre-treated wood	5.2	29.9 ± 1.9
A29	H2SO4 in H2O : EtOH	3 h	Acidic extract	71.2	48.1 ± 2.9
A30	H2SO4 in H2O : EtOH	3 h	Pre-treated wood	5.9	38.4 ± 1.7
A31	H2SO4 in H2O : EtOH	5 h	Acidic extract	74.5	45.7 ± 1.2
A32	H2SO4 in H2O : EtOH	5 h	Pre-treated wood	2.3	63.1 ± 0.6
A33	HCl in H2O	1 h	Acidic extract	27.5	56.6 ± 0.5
A34	HCl in H2O	1 h	Pre-treated wood	4.9	38.1 ± 0.9
A35	HCl in H2O	3 h	Acidic extract	26.4	58.5 ± 2.1
A36	HCl in H2O	3 h	Pre-treated wood	6.1	68.7 ± 1.1
A37	HCl in H2O	5 h	Acidic extract	23.5	48.8 ± 0.4
A38	HCl in H2O	5 h	Pre-treated wood	9.0	64.5 ± 0.4
A39	HCl in H2O : EtOH	1 h	Acidic extract	40.0	43.0 ± 1.2
A40	HCl in H2O : EtOH	1 h	Pre-treated wood	7.5	53.8 ± 0.3
A41	HCl in H2O : EtOH	3 h	Acidic extract	58.5	41.6 ± 0.8
A42	HCl in H2O : EtOH	3 h	Pre-treated wood	7.1	56.4 ± 1.8
A43	HCl in H2O : EtOH	5 h	Acidic extract	94.1	45.9 ± 2.4
A44	HCl in H2O : EtOH	5 h	Pre-treated wood	3.6	60.9 ± 1.9
Rosemary oleoresin (reference extract)^g					95.0 ± 0.3

aExtracts A21–A44 were prepared from the olive wood sample A, collected in April, 2003 (during the pruning period) at the village of Fuensanta, Jaén province, Spain.
bThe olive wood sample A was subjected to a hydrolysis pre-treatment with 0.5 M H₂SO₄ in H₂O (extracts A21–A26), 0.5 M H₂SO₄ in H₂O : EtOH (50 : 50, v/v) (extracts A27–A32), 1 M HCl in H₂O (extracts A33–A38), and 1 M HCl in H₂O : EtOH (50 : 50, v/v) (extracts A39–A44) (see Figure 7).
cTime of the hydrolysis pre-treatment on the olive wood sample A at 130°C.
dThe hydrolysis pre-treatment of olive wood sample A afforded a liquid acidic extract and a solid pre-treated wood on which further extractions were performed (see Figure 7).
eYield is expressed as grams of extract per kilogram of olive wood sample.
fRadical scavenging percentage (RSP) is expressed as DPPH^• scavenging (%). Values are means of three replicates ± SD (standard deviation).
gCommercially available rosemary extract was used as reference, at the same concentration (50 𝜇g mL⁻¹).