J Food Bioact

Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online

Journal website www.isnff-jfb.com

Original Research

Volume 8, December 2019, pages 92-98

Wood extracts as unique sources of soluble and insoluble-bound phenolics: reducing power, metal chelation and inhibition of oxidation of human LDL-cholesterol and DNA strand scission

Figure 1. Agarose gel electrophoresis of inhibition of peroxyl radical-induced DNA scission by soluble wood extracts. N (nicked), S (supercoiled) DNA. TA, tannic acid; BW, banana wood; PW, pinewood; QW, quibracho wood; OW, oak wood; OPW, old date palm wood; SPW, seedling date palm wood.

Figure 2. Agarose gel electrophoresis of inhibition of hydroxyl radical-induced DNA scission by soluble wood extracts. N (nicked), S (supercoiled) DNA. ; SPW, seedling date palm wood; OPW, old date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana ; TA, tannic acid.

Figure 3. Inhibition of cupric ion-induced human low-density lipoprotein (LDL) peroxidation. TA, tannic acid; SA, syringic acid; CAT, catechin; GA, gallic acid; SPW, seedling date palm wood; OPW, Saudi old date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood.

**Table 1.** Total phenolic contents (TPC) of woods extracts (mg GAE/g of WE)*
Feedstock	Fraction
*GAE, gallic acid equivalents; WE, wood extract; OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood. Data represent mean values ± standard deviation (n = 3). Values followed by the same letters within a column are not significantly different (p > 0.05).
OPW	74.65 ± 2.62^b	19.67 ± 0.87^a
SPW	80.03 ± 4.47^a	21.05 ± 0.60^a
OW	59.45 ±4.82^c	10.80 ± 0.10^b
PW	24.76 ± 0.26^d	7.54 ± 0.33^d
QW	43.34 ± 0.72^c	12.41 ± 0.14^b
BW	19.76 ± 1.01^d	5.98 ± 0.01^c

Table 1. Total phenolic contents (TPC) of woods extracts (mg GAE/g of WE)*

Feedstock

Fraction

soluble

insoluble-bound

*GAE, gallic acid equivalents; WE, wood extract; OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood. Data represent mean values ± standard deviation (n = 3). Values followed by the same letters within a column are not significantly different (p > 0.05).

OPW

74.65 ± 2.62^b

19.67 ± 0.87^a

SPW

80.03 ± 4.47^a

21.05 ± 0.60^a

59.45 ±4.82^c

10.80 ± 0.10^b

24.76 ± 0.26^d

7.54 ± 0.33^d

43.34 ± 0.72^c

12.41 ± 0.14^b

19.76 ± 1.01^d

5.98 ± 0.01^c

**Table 2.** Phenolic compounds identified in woods by MALDI-TOF-MS
MW	Identification	OPW	SPW	OW	PW	QW	BW
OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood.
110	catechol			+	+	+	+
154	protocatechuic acid	+	+		+	+
178	coniferilaldehyde	+	+			+
182	homovanillic acid	+	+		+	+
196	hydroxycaffeic acid			+		+
198	syringic acid	+	+		+	+	+
208	sinapaldehyde	+	+
272	3′-hydroxydihydrodaidzein			+	+	+	+
286	kaempferol			+	+	+	+
290	(+)-catechin	+	+	+	+		+
306	(+)-gallocatechin	+		+	+	+	+
316	rhamnetin				+	+	+
326	p-coumaric acid 4-O-glucoside	+	+		+	+

Table 2. Phenolic compounds identified in woods by MALDI-TOF-MS

Identification

OPW

SPW

OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood.

110

catechol

154

protocatechuic acid

178

coniferilaldehyde

182

homovanillic acid

196

hydroxycaffeic acid

198

syringic acid

208

sinapaldehyde

272

3′-hydroxydihydrodaidzein

286

kaempferol

290

(+)-catechin

306

(+)-gallocatechin

316

rhamnetin

326

p-coumaric acid 4-O-glucoside

**Table 3.** Reducing power (RP) and iron (II) chelation capacity (CC) of wood extracts
Feedstock	RP (mmoles TE/g WE)	CC (μmoles EE/g WE)
TE, trolox equivalent; EE, EDTA equivalents; OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood. Data represent mean values ± standard deviation (n = 3). Values followed by the same letters within a column are not significantly different (p > 0.05).
OPW	1.18 ± 0.32^a	0.13 ± 0.004^d	10.82 ± 1.60^b	11.42 ± 1.67^b
SPW	1.37 ± 0.02^a	0.81 ± 0.03^a	21.17 ± 1.44^a	12.95 ± 1.85^a
OW	0.55 ± 0.04^b	0.30 ± 0.008^c	10.68 ± 1.33^b	10.28 ± 2.44^c
PW	0.59 ± 0.14^b	0.70 ±0.05^b	6.94 ± 1.65^c	3.08 ± 4.46^d
QW	1.15 ± 0.27^a	0.68±0.007^b	9.86 ± 1.55^b	8.59 ± 7.48^c
BW	0.35±0.03^c	0.10±0.004^d	5.54 ± 1.25^c	2.28 ± 2.48^d

Table 3. Reducing power (RP) and iron (II) chelation capacity (CC) of wood extracts

Feedstock

RP (mmoles TE/g WE)

CC (μmoles EE/g WE)

Soluble

Insoluble-bound

Soluble

Insoluble-bound

TE, trolox equivalent; EE, EDTA equivalents; OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood. Data represent mean values ± standard deviation (n = 3). Values followed by the same letters within a column are not significantly different (p > 0.05).

OPW

1.18 ± 0.32^a

0.13 ± 0.004^d

10.82 ± 1.60^b

11.42 ± 1.67^b

SPW

1.37 ± 0.02^a

0.81 ± 0.03^a

21.17 ± 1.44^a

12.95 ± 1.85^a

0.55 ± 0.04^b

0.30 ± 0.008^c

10.68 ± 1.33^b

10.28 ± 2.44^c

0.59 ± 0.14^b

0.70 ±0.05^b

6.94 ± 1.65^c

3.08 ± 4.46^d

1.15 ± 0.27^a

0.68±0.007^b

9.86 ± 1.55^b

8.59 ± 7.48^c

0.35±0.03^c

0.10±0.004^d

5.54 ± 1.25^c

2.28 ± 2.48^d

**Table 4.** Inhibition of DNA strand scission (%) of soluble wood phenolics towards hydroxyl- and peroxyl-induced oxidation*
Feedstock	DNA strand scission inhibition (%)
OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood. Data represent mean values ± standard deviation (n = 3). Values followed by the same letters within a column are not significantly different (p > 0.05).
SPW	36.54 ± 2.39a	98.42 ± 0.91a
OPW	38.64 ± 0.74 a	86.39 ± 1.94 b
OW	29.85 ± 1.93 b	69.41 ± 1.97 c
PW	19.05 ± 0.63 c	51.85 ± 2.66 c
QW	27.07 ± 3.69 b	89.06 ± 0.89 b
BW	24.88 ± 4.66 b	77.89 ± 2.13 c

Table 4. Inhibition of DNA strand scission (%) of soluble wood phenolics towards hydroxyl- and peroxyl-induced oxidation*

Feedstock

DNA strand scission inhibition (%)

Hydroxyl radical

Peroxyl radical

OPW, old date palm wood; SPW, seedling date palm wood; OW, oak wood; PW, pinewood; QW, quibracho wood; BW, banana wood. Data represent mean values ± standard deviation (n = 3). Values followed by the same letters within a column are not significantly different (p > 0.05).

SPW

36.54 ± 2.39a

98.42 ± 0.91a

OPW

38.64 ± 0.74 a

86.39 ± 1.94 b

29.85 ± 1.93 b

69.41 ± 1.97 c

19.05 ± 0.63 c

51.85 ± 2.66 c

27.07 ± 3.69 b

89.06 ± 0.89 b

24.88 ± 4.66 b

77.89 ± 2.13 c