Phenolic Content, Antioxidant Potential, and Antimicrobial Activities of Fruit and Vegetable By-Product Extracts

Figures & data

Table 1  Fruit and vegetable by-products examined

Common name	Scientific name	Families	Variety	Examined products
Fruits
Pomegranate	Punica granatum	Lythraceae	Dente di cavallo	Pomace–Peel
Apple	Malus domestica	Rosaceae	Grigia di Torriana	Pomace–Peel
Dog rose	Rosa canina	Rosaceae	—	Pulp–Seeds
Cornelian cherry	Cornus mas	Cornaceae	—	Pulp–Seed
Hazelnut	Corylus avellana	Corylaceae	Round the Kind Trilobata	Skin
White grapes	Vitis vinifera	Vitaceae	Chardonnay	Marc
Red grapes	Vitis vinifera	Vitaceae	Nebbiolo	Marc
Vegetables
Potato	Solanum tuberosum	Solanaceae	Viola	Pulp–Peel
Potato	Solanum tuberosum	Solanaceae	Desirée	Pulp–Peel
Potato	Solanum tuberosum	Solanaceae	Piatlina	Pulp–Peel
Leek	Allium porrum	Liliaceae	Monstrueux di Carentan	Non-edible leaves

Table 2  Total phenolic content (TPC) in the plant extracts obtained with the three solvents

	TPC (mg GAE^†/g dry weight)
	Solvent A^††	Solvent B^††	Solvent C^††
Hazelnut (skin)	124.6 ± 2.44^h,A	116.5 ± 5.25^e,A	166.3 ± 5.43^f,B
Pomegranate (peel)	197.1 ± 1.76^g,B	173.2 ± 3.54^f,A	212.3 ± 3.31^g,C
Apple (peel)	32.3 ± 1.14^e,B	20.1 ± 8.99^c,A	61.3 ± 4.65^e,C
“Viola” potato (peel)	9.5 ± 0.29^bc,A	8.9 ± 1.40^ab,A	8.9 ± 0.08^a,A
“Desiree” potato (peel)	5.9 ± 0.22^ab,A	7.4 ± 0.52^a,B	7.5 ± 0.08^a,B
“Piatlina” potato (peel)	4.2 ± 0.09^a,A	4.2 ± 0.22^a,A	5.2 ± 0.07^a,B
Leek (leaves)	5.9 ± 0.08^ab,A	6.4 ± 0.50^a,AB	7.0 ± 0.31^a,B
Cornelian cherry (seed)	36.6 ± 5.51^f,A	33.3 ± 2.82^d,A	37.7 ± 3,32^c,A
Dog rose (seeds)	21.2 ± 0.38^d,B	16.3 ± 0.31^bc,A	21.5 ± 0.33^b,B
White grape (marcs)	34.2 ± 1.25^ef,A	35.8 ± 9.76^d,A	50.5 ± 6.57^d,B
Red grape (marcs)	10.4 ± 1.68^c,B	6.6 ± 0.88^a,A	24.1 ± 0.75^b,C
Dog rose (pulp)	19.9 ± 1.00^e,B	16.7 ± 0.64^d,A	85.5 ± 1.44^f,C
Cornelian cherry (pulp)	32.6 ± 1.32^d,B	26.8 ± 3.00^e,A	50.1 ± 2.77^e,C
Pomegranate (pomace)	9.9 ± 0.24^c,B	8.7 ± 0.45^c,A	13.2 ± 0.29^d,C
Apple (pomace)	8.9 ± 0.18^c,A	9.8 ± 1.55^c,A	10.4 ± 0.25^c,A
“Viola” potato (pulp)	3.1 ± 0.20^b,B	2.4 ± 0.19^ab,A	2.6 ± 0.04^ab,A
“Desiree” potato (pulp)	2.1 ± 0.42^b,A	4.2 ± 0.10^b,B	4.4 ± 1.04^b,B
“Piatlina” potato (pulp)	0.5 ± 0.40^a,A	0.8 ± 0.43^a,A	1.6 ± 0.24^a,B
Data are means ± SD (n = 3).
^†Gallic acid equivalent.
^††Solvent A = methanol (90%) in acidified water; solvent B = ethanol (80%) in water; solvent C = acetone (70%) in water.
^a–hValues within column with the same letters are not significantly different at p ≤ 0.05.
^A–CValues within row with the same letters are not significantly different at p ≤ 0.05.

Table 3  Antioxidant capacity (AC) evaluated for extracts obtained with the three solvents

	IP (%)			TEAC (μM TE^†/g dry weight)
	Solvent A^††	Solvent B	Solvent C	Solvent A	Solvent B	Solvent C
Hazelnut (skin)	79.51 ± 5.18 ^e,A	86.58 ± 5.54 ^h,AB	92.90 ± 2.45 ^h,B	0.71 ± 0.01 ^f,A	0.71 ± 0.01 ^f,A	0.71 ± 0.01 ^e,A
Pomegranate (peel)	95.73 ± 0.04^f,A	95.27 ± 0.57^i,A	95.62 ± 0.03^h,A	0.70 ± 0.01^f,A	0.71 ± 0.01^f,A	0.71 ± 0.01^e,A
Apple (peel)	49.33 ± 2.19^d,B	20.89 ± 2.26^c,A	63.44 ± 2.58^ef,C	0.71 ± 0.01^f,A	0.71 ± 0.01^f,A	0.71 ± 0.01^e,A
“Viola” potato (peel)	23.50 ± 0.60^b,B	19.26 ± 0.80^c,A	20,34 ± 0.02^c,A	0.26 ± 0.01^c,A	0.26± 0.01^c,A	0.30 ± 0.02^c,B
“Desirée” potato (peel)	10.15 ± 0.61^a,A	12.83 ± 0.88^b,A	14.87 ± 0.93^bc,A	0.15 ± 0.01^b,A	0.19 ± 0.01^b,B	0.22 ± 0.01^a,C
“Piatlina” potato (peel)	8.42 ± 0.43^a,A	7.76 ± 0.61^a,A	10.17 ± 1.21^ab,B	0.13 ± 0.01^a,A	0.13 ± 0.01^a,A	0.20 ± 0.01^a,B
Leek (leaves)	5.19 ± 0.87^a,A	5.79 ± 0.92^a,A	5.89 ± 0.22^a,A	0.13 ± 0.01^a,A	0.19 ± 0.01^b,B	0.25 ± 0.04^b,C
Cornelian cherry (seed)	81.95 ± 7.66^e,A	76.44 ± 2.48^g,A	77.44 ± 6.86^g,A	0.71 ± 0.01^f,A	0.71 ± 0.01^g.A	0.71 ± 0.01^e,A
Dog rose (seeds)	36.16 ± 2.22^c,B	31.74 ± 2.09^d,A	45.40 ± 0.05^d,C	0.53 ± 0,01^d,B	0.44 ± 0,01^d,A	0.62 ± 0,01^d,C
White grape (marcs)	41.68 ± 5.25^c,A	40.91 ± 4.99^e,A	58.34 ± 6.18^e,B	0.67 ± 0.01^e,A	0.67 ± 0.01^e,A	0.70 ± 0.01^e,B
Red grape (marcs)	52.96 ± 9.96^d,A	62.84 ± 3.21^f,A	65.98 ± 4.03^f,A	0.71 ± 0.01^f,A	0.71 ± 0.01^f,A	0.71 ± 0.01^e,A
Dog rose (pulp)	72.48 ± 1.11^d,A	73.79 ± 2.34^d,A	74,37 ± 2.57^d,A	0.51 ± 0.02^e,B	0.40 ± 0.02^c,A	0.71 ± 0.01^e,C
Cornelian cherry (pulp)	59.03 ± 10.22^c,B	41.98 ± 3.51^c,A	54.44 ± 4.88^c,A	0.71 ± 0.01^f,A	0.69 ± 0.01^d,A	0.70 ± 0.01^e,A
Pomegranate (pomace)	26.19 ± 1.23^b,B	16.71 ± 3.08^b,A	24.91 ± 3.50^b,B	0.37 ± 0.02^d,A	0.37 ± 0.07^c,A	0.46 ± 0.03^d,A
Apple (pomace)	7.67 ± 0.28^a,B	5.55 ± 0.66^a,A	8.73 ± 1.06^a,B	0.26 ± 0.03^c,A	0.28 ± 0.01^b,AB	0.32 ± 0.02^c,B
“Viola” potato (pulp)	8.48 ± 0.17^a,C	4.66 ± 0.24^a,A	6.93 ± 0.03^a,B	0.11 ± 0.01^b,A	0.14 ± 0.01^a,B	0.17 ± 0.01^b,C
“Desiree” potato (pulp)	4.88 ± 0.10^a,A	5.58 ± 1.29^a,A	5.81 ± 0.27^a,A	0.07 ± 0.01^a,A	0.11 ± 0.01^a,B	0.12 ± 0.01^a,B
“Piatlina” potato (pulp)	4.75 ± 0.08^a,A	4.01 ± 0.35^a,B	4.01 ± 0.13^a,A	0.08 ± 0.01^a,A	0.15 ± 0.07^a,A	0.10 ± 0.01^a,A
Data are means ± SD (n = 3).
^†Trolox equivalent.
^††Solvent A = methanol (90%) in acidified water; solvent B = ethanol (80%) in water; solvent C = acetone (70%) in water.
^a–hValues within column with the same letters are not significantly different at p ≤ 0.05.
^A–CValues within row with the same letters are not significantly different at p ≤ 0.05.

Table 4  Antibacterial activity of extracts obtained with the three solvents and evaluated by the agar-well diffusion assay. The concentration was 20 mg of dry extract/ml

	Pomegranate (peel)			Pomegranate (pomace)			Apple (peel)			Apple (pomace)			Cornelian cherry (pulp)			Dog rose (pulp)
Solvent^†	A^†	B	C	A	B	C	A	B	C	A	B	C	A	B	C	A	B	C
Salmonella Enteritidis O:103	+^a	−	+	−	−	−	−	−	−	−	−	−	−	−	−	−	−	+
Pseudomonas fluorescens	++	−	−	+	−	−	+	+	+	+	−	−	−	−	−	−	−	−
Pseudomonas aeruginosa	+	+	+	−	−	−	+	+	+	−	−	−	+	−	−	−	−	−
Escherichia coli ATCC 35150	+	+	+	−	−	−	−	−	−	−	−	−	−	−	−	−	−	−
Escherichia coli DH5α	+	−	+	+	−	−	+	−	+	+	−	−	−	−	+	+	−	+
Serratia marcescens	−	−	+	−	−	−	−	−	−	−	−	−	−	−	−	−	−	−
Staphylococcus aureus ATCC 10527	+	+	++	+	+	+	−	+	+	−	−	+	−	−	+	+	+	+
Listeria monocytogenes NCTC 10527	+	+	+	−	−	−	+	+	+	+	+	+	−	−	−	−	−	−
Bacillus cereus DSM 350	+	−	+	−	−	−	−	+	+	−	−	−	−	−	−	−	−	−
Lactococcus lactis DSM 4366	+	−	+	+	−	+	+	+	+	+	−	+	+	+	+	+	−	+
Lactobacillus sakei DSMZ 6333	−	−	−	−	−	−	−	−	+	−	−	−	−	−	−	−	−	−
Staphylococcus xylosus	+	−	−	−	−	−	−	−	−	−	−	−	−	−	−	−	−	−
^†Solvent A = methanol (90%) in acidified water; solvent B = ethanol (80%) in water; solvent C = acetone (70%) in water.
^a-: Inhibition zone ≤ 1 mm; +: 1 mm < inhibition zone ≤ 3 mm; ++: inhibition zone > 3 mm.