Antioxidant activities, polyphenol, flavonoid, and

Journal of the Saudi Society of Agricultural Sciences xxx (2018) xxx–xxx

Contents lists available at ScienceDirect

Journal of the Saudi Society of Agricultural Sciences journal homepage: www.sciencedirect.com

Full length article

Antioxidant activities, polyphenol, flavonoid, and amino acid contents in peanut shell Bishnu Adhikari a, Sanjeev Kumar Dhungana a, Muhammad Waqas Ali a, Arjun Adhikari a, Il-Doo Kim b, Dong-Hyun Shin a,⇑ a b

School of Applied Biosciences, Kyungpook National University, Daegu 41566, Republic of Korea International Institute of Agriculture Research & Development, Kyungpook National University, Daegu 41566, Republic of Korea

a r t i c l e

i n f o

Article history: Received 3 November 2017 Revised 14 January 2018 Accepted 11 February 2018 Available online xxxx Keywords: Antioxidant activity Cosmetic Free amino acid Peanut shell Polyphenol

a b s t r a c t Peanut shell; a byproduct of an important leguminous crop, peanut; is a potential source of different functional compounds. Antioxidant activities, secondary metabolites and amino acid contents in peanut shells of six Korean cultivars were studied in the present study. Peanut shells showed remarkable antioxidant potentials with high amounts of total polyphenol (428.1–739.8 mg gallic acid equivalents/g), flavonoid (142.6–568.0 mg quercetin equivalents/g), and amino acid (5.76–34.56 mg/g) contents. 2, 2diphenyl-1-picrylhydrazyl (DPPH), 2,20 -azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), superoxide dismutase (SOD)-like activity, and reducing power potential of the peanut shells were considerable. The results suggest that the shells of Korean peanut cultivars could be a potential source of natural antioxidants and functional compounds for various industrial uses including cosmetics. Ó 2018 Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction Peanut (Arachis hypogaea L.) is a protein rich leguminous crop grown across the world mainly for seed and oil (Bertioli et al., 2011). In 2014 it was grown on 26.5 million ha worldwide with a total production of 43.9 million ton (FAOSTAT, 2014). Peanut shells, a by-product of peanut crop, comprise about one third by weight of peanut pod and are quite abundant and inexpensive product (Gao et al., 2011; Radhakrishnan et al., 2013). However, they can be utilized on various purposes such as feedstock (De Camargo et al., 2012), food, fuel, filler in fertilizers (Fengweng, 2008; Rui-he, 2010), in bio filter carriers (Ramırez-López et al., 2003) and even in reuse of organic wastes (Torkashvand et al., 2015). Protein, fat, carbohydrate, sugars, and minerals are noticeably present in peanut shell (USDA, 2017) with lignocellulosic compositions such as hemicellulose, cellulose and lignin (Prabhakar et al., 2015). Peanut shell contains many bioactive and functional compounds which are safe

⇑ Corresponding author. E-mail address: [email protected] (D.-H. Shin). Peer review under responsibility of King Saud University.

Production and hosting by Elsevier

for human consumption (Francisco and Resurreccion, 2008; Gao et al., 2011). Along with polyphenols and flavonoids (RosalesMartínez et al., 2014; Zhang et al., 2013) peanut shells also contain luteolin, carotene, isosaponaretin (Yu et al., 2014). Peanut shell has shown antioxidant and antimicrobial activities as well as inhibitory effect against insect pest attack (Wee et al., 2007; Wee and Park, 2001). Due to these readily available natural antioxidants in peanut shells, many chemists and nutritionists have been attracted on it (Qiu et al., 2012). It is gaining attention on therapeutic and pharmaceutical aspects as it was used for relieving coughs, decreasing blood pressure and eliminating mucus from lungs (Vaughn, 1995). Due to safe and health promoting issues, consumers’ demand for cosmetic products containing natural ingredients is increasing (Soto et al., 2015). Because of different useful biological properties polyphenolic compounds are attractive ingredients for cosmetics. They are promisingly used in skin problems like disease, aging, damage, and disorders (Działo et al., 2016). Amino acids are protein metabolism regulators commonly used in cosmetic ingredients, mainly as skin and hair conditioning agents (Burnett et al., 2013). Various agricultural by-products rich in the polyphenols, dietary fibers and/or amino acids have been used in the cosmetic industries. For instance, citrus cake, a by-product of citrus fruit, has been used as cosmetic formulations for treating skin pigmentation disorders (Barbulova et al., 2015); grape byproducts are employed for skin care cosmetic formulations (Soto

https://doi.org/10.1016/j.jssas.2018.02.004 1658-077X/Ó 2018 Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Please cite this article in press as: Adhikari, B., et al. Antioxidant activities, polyphenol, flavonoid, and amino acid contents in peanut shell. Journal of the Saudi Society of Agricultural Sciences (2018), https://doi.org/10.1016/j.jssas.2018.02.004

2

B. Adhikari et al. / Journal of the Saudi Society of Agricultural Sciences xxx (2018) xxx–xxx

et al., 2015); mango by-products have been used in the cosmetic and pharmaceutical industries (Jahurul et al., 2015). Peanut shells may possess the potentiality of being used as an inexpensive source of natural ingredients for the expensive cosmetic industries as a huge amount (about 14 million tons) of peanut shells is often discarded or burned as waste (Gao et al., 2011; Qiu et al., 2012; Radhakrishnan et al., 2013). Although few studies have reported the antioxidant potentials and phenolic contents of peanut shell, to the best of our knowledge, there has been no study on amino acid contents of peanut shells. Since amino acids are important constituents of cosmetic products (Burnett et al., 2013), the aim of this study was to measure the amino acid contents as well as to determine the antioxidant activities and phenolic compounds in the shells of six Korean peanut cultivars.

2. Materials and methods 2.1. Peanut Six Korean peanut cultivars; Daekwang, Akwang, Baekjung, Alogi, Pungan, and Heugttangkong were obtained from Gyeonsangbukdo agricultural research and extension services, Daegu, Korea in September 2016. They were among the widely grown peanut cultivars in Korea. 2.2. Chemical and reagents DPPH (2,2-diphenyl-1-picrylhydrazyl), HPLC-grade H2O, Folin– Ciocalteu phenol reagent, sodium carbonate (Na2CO3), sodium hydroxide (NaOH), aluminium chloride (AlCl3), quercetin, 2,20 azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), potassium persulfate, ethylene diamine tetra acetic acid (EDTA), and Tris [tris(hydroxymethyl)aminomethane] were obtained from Sigma chemicals, USA. All the used chemicals and reagents were of analytical grade. 2.3. Peanut shell extract preparation Peanuts were deshelled using hands and the shells were kept in 70 °C before subjected to freeze drying. The shells were ground into powders using a commercial grinder (HIL-G-501, Hanil Co., Seoul, Korea). The samples were subjected to extraction in absolute methanol (1:10 w/v) using shaking incubator (25 °C, 150 rpm) for 6 h and centrifuged (13,000g) at room temperature for 10 min. The supernatants were filtered through syringe filter (PVDF filter, Woongki science co. ltd, Seoul, Korea). 2.4. Antioxidant activities 2.4.1. DPPH free radical scavenging activity The DPPH free radical scavenging activities of peanut shell extracts were measured according to the method described by Xu and Chang (2007) with some modifications. Freshly prepared DPPH solution (0.1%) in absolute methanol was used in this study. An equal volume (100 mL) of 0.1% DPPH solution and sample extracts were mixed in microplates. The reaction mixture was kept for 30 min at room temperature (22–25 °C) in dark. Equal proportion (100 mL) of DPPH and methanol was mixed for the control. The absorbance value of the reaction mixtures was measured at 517 nm using a microplate spectrophotometer (Multiskan GO, Thermo Fischer Scientific, Vantaa, Finland). The DPPH radical scavenging activity was calculated by using the following equation:

DPPH radical scavenging activity% ¼ ½1 ððA AO Þ=ðB BO ÞÞ 100

where A = absorbance of DPPH and sample; AO = absorbance of methanol and sample; B = absorbance of DPPH and methanol; BO = absorbance of methanol. The experiments were performed in triplicate. 2.4.2. ABTS radical scavenging activity The ABTS radical scavenging activity of peanut shell extracts was carried out following the procedure of Lee et al. (2010) with a slight modification. Stock solutions of 7 mM ABTS and 2.4 mM potassium persulfate were prepared in double distilled water. The ABTS cation radical was produced through the working solution, a mixture of the two stock solutions in equal quantities and allowed to react in dark for 12–16 h. The working solution was diluted by mixing 1 mL of the solution to 20 mL of double distilled water to get an absorbance value near to 0.7. Twenty microliters of sample extracts was mixed with 180 mL of the working solution and absorbance was measured at 734 nm using a microplate spectrophotometer (Multiskan GO, Thermo Fischer Scientific, Vantaa, Finland). The ABTS radical scavenging potential of the sample extracts was calculated using the following equation:

ABTS radical scavenging activityð%Þ ¼ ½ðAC AS Þ=ðAC Þ 100 where AC is the absorbance of ABTS radical cation and AS is the absorbance of a mixture of ABTS radical solution and sample extract. The experiments were performed in triplicate. 2.4.3. Superoxide dismutase (SOD)-like activity The SOD-like activity of peanut shell extracts was measured following the method described by Lee et al. (2003) with some modifications. A reaction mixture was prepared by adding 0.3 mL of Tris–HCl buffer (10 mM EDTA, 50 mM Tris, pH 8.5), 0.2 mL of 7.2 mM pyrogallol and 0.2 mL sample extracts. The mixture was allowed to react at room temperature (22–25 °C) in dark for 10 min. After incubation in dark, a 50-mL of 1 N HCl was added into the mixture in order to terminate the reaction. The pyrogallol autoxidation inhibition of the sample extracts was assayed through the absorbance values measured at 420 nm using a microplate spectrophotometer (Multiskan GO, Thermo Fischer Scientific, Vantaa, Finland). For control Tris-HCl buffer was taken instead of the sample extracts. The difference in the absorbance values between the experimental and the control groups was recorded as a percentage. The SOD-like activity was calculated using the following equation:

SOD-like activityð%Þ ¼ ðSO SÞ=SO 100 where SO = Change in the absorbance value measured with Tris-HCl buffer instead of sample extracts and S = Changes in absorbance value measured with the sample extracts. Experiments were performed in triplicate. 2.4.4. Reducing power potential Reducing power potential of the peanut shell extracts was assayed following the procedure explained by Sanjukta et al. (2015). A 900-mL of 0.2 M phosphate buffer (pH 6.6) was added to 100 mL of the peanut shell extract and then 900 mL of 1% potassium ferric cyanide was mixed to the solution. The mixture was kept at room temperature (22–25 °C) for 20 min. Nine hundred microliters of 10% trichloroacetic acid was added into the reaction mixture and centrifuged (3000g) for 15 min. From the supernatant (upper layer), 900 mL of the solution was taken and mixed with each 900 mL of double distilled water and 0.1% ferric chloride. The absorbance reading of the solutions was taken at 700 nm using a microplate spectrophotometer (Multiskan GO Thermo Fischer Scientific, Vantaa, Finland). The absorbance values indicate the relative reducing powder potential of the sample extracts that is increased absorbance value shows the elevated reducing power


3


potential and vice versa. Ascorbic acid was used as a standard and the results were expressed as microgram ascorbic acid equivalents (AAE) per gram sample. The experiments were performed in triplicate. 2.5. Total polyphenolic content Total polyphenolic content of peanut shell extracts was determined using Folin–Ciocalteu reagent and gallic acid following the previous report (Singleton et al., 1999). A 50-mL of the extract was mixed thoroughly with 1 mL of 2% sodium carbonate solution using a vortexer and allowed to stand for 3 min. After 3 min, a 50mL of 1 N Folin–Ciocalteu reagent was added to the mixture and kept for 30 min at room temperature (22–25 °C) in dark for color development. The absorbance value was taken at 750 nm using a microplate spectrophotometer (Multiskan GO Thermo Fischer Scientific, Vantaa, Finland). Gallic acid was used as a standard to plot the calibration curve. The total polyphenol content of the shell extracts was expressed as microgram gallic acid equivalent (GAE) per gram sample. The experiment was conducted in three replications. 2.6. Total flavonoid content Total flavonoid content of the peanut shell extracts was determined following the method described earlier (Zhu et al., 2010) with some modifications. Three hundred microliters of sample extract was mixed with an equal volume of double distilled water followed by an addition of 30 mL of 5% NaNO2. The mixture was allowed to stand at room temperature for 5 min and then 60 mL of 10% AlCl3 was added into the mixture. After allowing the mixture to stand for 5 min, 200 mL of 1 M NaOH was added to the mixture. The spectrophotometric absorbance reading was taken at 500 nm using a microplate spectrophotometer (Multiskan GO Thermo Fischer Scientific, Vantaa, Finland). Quercetin was used as a standard to draw the calibration curve. The total flavonoid content was expressed in microgram quercetin equivalent (QE) per gram sample. The experiment was conducted in three replications. 2.7. Free amino acid content The free amino acid content of peanut shell sample was analyzed following the method described by Yoo and Chang (2016). Fifty milligrams of the sample powder was hydrolyzed with 1 mL of 6 N HCl for 24 h in an ampulla tube at 110 °C. After completion of the hydrolysis, the suspension was filtered and evaporated under vacuum. The solid residue was dissolved in 2 mL of deionized water filtered and evaporated as described earlier. The process was repeated two times. Finally, the solid residue was dissolved in 10 mL of 0.01 N HCl solution, vortexed and filtered through a 0.45 mm cellulose acetate membrane. The free amino acid composition was measured using an automatic amino acid analyzer (L-8900 Hitachi, Tokyo, Japan). The amount of amino acids present in the samples was determined using the amino acid standards (Wako Pure Chemical Industries, Ltd., Osaka, Japan). All of the analyses were carried out in duplicate and the amount of amino acid was expressed in microgram per gram sample. 2.8. Statistical analysis Data were subjected to analysis of variance by using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA). Significant variation among treatment means was identified using least significant difference (LSD) test at 95% confidence interval. All the results were expressed as means ± SE in which the mean values were the averages of triplicate experiments unless otherwise mentioned.

3. Results and discussion 3.1. DPPH radical scavenging activities The DPPH radical scavenging activity of peanut shells varied from 61.9 to 87.6% in the order of Heugttangkong > Akwang > Alogi > Pungan > Daekwang > Baekjung (Table 1). The high DPPH radical scavenging potential of the peanut shells might be due to the presence of different antioxidant compounds (Qiu et al., 2012; Wee et al., 2007). In the shells of legume crops including peanut phenolic compounds are the major contributor for the DPPH radical scavenging capacities (Fidrianny et al., 2014). Not only the seeds but also the shells of peanuts constitute a number of polyphenolic compounds with relatively high antioxidant potential and also other health promoting compounds, which could be effectively used in the food industries (Duncan et al., 2006). 3.2. ABTS radical scavenging activities The peanut shells of different cultivars contained ABTS radical scavenging activities (39.6–58.1%) in the order of Akwang > Heugttangkong > Baekjung > Alogi > Pungan > Daekwang (Table 1). As in the DPPH assay, Akwang and Heugttangkong showed significantly higher ABTS radical scavenging activity than the other four cultivars. Similar results were found by De Camargo et al. (2012) in which the in-shell peanuts showed higher ABTS radical scavenging activities than the blanched peanuts. The results of ABTS potential in the peanut shells also agree with the previous findings of Fidrianny et al. (2014). The high ABTS radical scavenging activity in the peanut shells might be due to the presence of phenolic compounds (Yen et al., 1993). The seed coats and shells are also the major contributors to the total antioxidant capacity of the whole peanuts (Attree et al., 2015). The nutritionists and food chemists are attracted on peanut shell as it is a good source of readily available natural antioxidant (Zhao et al., 2012). 3.3. SOD-like activities The SOD-like activities of peanut shells of different cultivars were in the range of 12.8–21.2% (Table 2). The shells of Daekwang exhibited the highest SOD-like activity followed by Pungan. Heugttangkong had the lowest SOD-like activity among the six cultivars. The high SOD-like activities of the peanut shells might be due to the presence of polyphenolic compounds (Nakamura et al., 2010; Win et al., 2011). Along with an appreciable antioxidant potential, the shells also showed an anti-mutagenic effect (Duh and Yen, 1997). Furthermore, the peanut shells did not cause any clinical abnormalities which gave an additional evidence to be used as a potential natural antioxidant (Gao et al., 2011). The interest of using naturally occurring antioxidants is ever increasing because of the growing concerns about the potential health hazards of synthetic antioxidants (Nepote et al., 2002).

Table 1 DPPH and ABTS radical scavenging potential of peanut shells. Cultivar

DPPH (%)

ABTS (%)

Daekwang Akwang Baekjung Alogi Pungan Heugttangkong

63.3 ± 0.82c 87.5 ± 1.13a 61.9 ± 2.43c 83.5 ± 1.66a 70.9 ± 1.71b 87.6 ± 1.21a

39.6 ± 2.13c 58.1 ± 1.88a 53.2 ± 2.31ab 48.4 ± 1.34b 42.4 ± 1.80c 57.5 ± 1.97a

The values are expressed as mean ± SE (n = 3). The mean values followed by different superscripts in the same column are significantly different (p < 0.05).


4


3.4. Reducing power potential

Table 2 SOD-like activity and reducing power potential of peanut shells. Cultivar

SOD-like activity (%)


a

Reducing power (mg AAE/g) d

21.2 ± 0.11 16.9 ± 0.53b 19.1 ± 1.94ab 16.6 ± 0.98bc 20.2 ± 1.68ab 12.8 ± 1.18c

2.87 ± 0.010 3.07 ± 0.007b 3.06 ± 0.014b 3.14 ± 0.007a 2.92 ± 0.008c 3.12 ± 0.003a

The values are expressed as mean ± SE (n = 3). The mean values followed by different superscripts in the same column are significantly different (p < 0.05). AAE: ascorbic acid equivalent. Table 3 Total polyphenol and total flavonoid content of peanut shells. Cultivar

Polyphenol (mg GAE/g)


Flavonoid (mg QE/g)

e

249.3 ± 8.45d 568.0 ± 10.48a 333.1 ± 12.22c 476.8 ± 21.99b 192.7 ± 16.71e 142.6 ± 12.25f

428.1 ± 4.86 739.8 ± 7.71a 556.5 ± 6.67d 606.4 ± 9.29c 638.9 ± 9.17b 556.9 ± 12.96d

Reducing power potential of the peanut shells was in the range of 2.87–3.14 mg AAE/g (Table 2). Alogi showed the highest reducing power potential followed by Heugttangkong, whereas Daekwang had the lowest potential. Phenolic compounds of different plants have shown various degrees of antioxidant potentials (Scalbert et al., 2005). The high reducing power of the peanut shells indicates the presence of substantial amounts of antioxidants (Zhang et al., 2013). The antioxidant activities of the peanut shells were comparable with that of other natural antioxidants. Due to a significant antioxidant potential of the peanut shells they could be used as a raw material in food and cosmetic industries (El-Baroty et al., 2014). Duh and Yen (1997) found the peanut shell as an antioxidant in the peanut and soybean oil. This result confirms that the peanut shell is a potential source of the antioxidants for using in the food products.

3.5. Total phenolic content

The values are expressed as mean ± SE (n = 3). The mean values followed by different superscripts in the same column are significantly different (p < 0.05). GAE: gallic acid equivalent. QE: quercetin equivalent.

Total phenolic content of the peanut shells significantly varied with cultivar which was in the range of 428.1–739.8 mg GAE/g (Table 3). The total phenolic contents of peanut shells were in the following order: Akwang > Pungan > Alogi > Heuttangkong >

Table 4 Free amino acid content (mg/g of dry weight) of peanut shells. Amino acid

Peanut shell samples Daekwang

Akwang

Baekjung

Alogi

Pungan

Heugttangkong

L-Histidine

0.19 ± 0.050c

0.26 ± 0.036c

1.21 ± 0.232a

0.70 ± 0.080b

0.35 ± 0.024bc

0.32 ± 0.053c

L-Isoleucine

0.43 ± 0.002c

0.63 ± 0.024c

1.59 ± 0.313a

1.18 ± 0.075ab

0.67 ± 0.040c

0.72 ± 0.063bc

Essential amino acid

L-Leucine

0.38 ± 0.037

L-Lysine

0.25 ± 0.04d

d

1.11 ± 0.101

bc

0.72 ± 0.045c b

ab

a

b

3.03 ± 0.290

1.45 ± 0.212

2.39 ± 0.143a

1.20 ± 0.162b

ab

a

cd

0.81 ± 0.044

0.82 ± 0.174cd

0.17 ± 0.084d

0.76 ± 0.066c

ab

0.04 ± 0.01ab

L-Methionine

0.03 ± 0.001

0.05 ± 0.01

0.05 ± 0.006

L-Phenylalanine

0.23 ± 0.062b

0.64 ± 0.148b

1.53 ± 0.261a

1.17 ± 0.061a

0.34 ± 0.099b

0.62 ± 0.020b

L-Threonine

0.13 ± 0.003e

0.26 ± 0.032de

1.49 ± 0.081a

0.76 ± 0.074b

0.48 ± 0.016c

0.31 ± 0.002d

a

a

c

b

0.07 ± 0.009

0.05 ± 0.006

L-Valine

0.52 ± 0.003

1.03 ± 0.138

0.98 ± 0.033

0.98 ± 0.061bc

Total essential amino acid

2.16

4.70

13.26

8.20

3.85

4.57

0.51 ± 0.024c

1.19 ± 0.095bc

2.83 ± 0.626a

1.93 ± 0.287ab

0.69 ± 0.011c

1.30 ± 0.361bc

0.65 ± 0.062e

1.19 ± 0.203de

4.92 ± 0.211a

2.70 ± 0.278b

2.07 ± 0.279bc

1.67 ± 0.043cd

d

b

1.97 ± 0.265

1.67 ± 0.159

bc

Non-essential amino acid L-Arginine L-Aspartic

acid

c

b

0.14 ± 0.002

0.24 ± 0.007

0.08 ± 0.015

L-Glutamic

0.12 ± 0.002c

0.27 ± 0.008c

5.18 ± 0.166a

0.79 ± 0.023b

1.03 ± 0.003b

0.23 ± 0.004c

0.05 ± 0.011d

0.32 ± 0.043bc

1.98 ± 0.026a

0.51 ± 0.142b

0.10 ± 0.003cd

0.22 ± 0.073cd

c

bc

a

acid

L-Tyrosine

0.08 ± 0.002

0.22 ± 0.044

0.45 ± 0.076

0.31 ± 0.041

0.11 ± 0.027

0.18 ± 0.024bc

Proline b-Alanine Total non-essential amino acid

0.89 ± 0.084d 0.79 ± 0.162c 3.23

1.32 ± 0.180c 1.27 ± 0.080bc 6.02

2.09 ± 0.193a 1.91 ± 0.068ab 19.44

1.78 ± 0.033ab 1.95 ± 0.287a 10.21

1.03 ± 0.099cd 0.72 ± 0.079c 5.82

1.37 ± 0.080bc 1.33 ± 0.314abc 6.59

L-Anserine

ND ND 0.31 ± 0.004cd ND ND

ND ND 0.43 ± 0.058ab ND ND

ND ND 0.35 ± 0.014bc ND ND

ND ND 0.48 ± 0.020a ND ND

ND ND 0.23 ± 0.004d ND ND

ND ND 0.45 ± 0.005a ND ND

L-Carnosine

ND

ND

ND

ND

ND

ND

L-Citrulline

ND

ND

ND

ND

ND

ND

L-Ornithine

ND

ND

ND

ND

ND

ND

L-Sarcosine

ND

ND

ND

ND

ND

ND

O-Phospho ethanol amine O-Phospho-L-Serine Phosphoserine Taurine Total other free amino acid Total free amino acid

ND 0.06 ± 0.001d ND ND 0.37 5.76

ND 0.14 ± 0.001cd ND ND 0.57 11.29

ND 1.51 ± 0.106a ND ND 1.86 34.56

ND 0.48 ± 0.172b ND ND 0.96 19.37

ND 0.42 ± 0.073bc ND ND 0.65 10.32

ND 0.10 ± 0.023d ND ND 0.55 11.71

Other free amino acid 1-methyl-L-histidine 3-methyl-1-Lhistidine Ammonia Hydroxylysine

ab

0.07 ± 0.007

0.29 ± 0.011a

L-Cystine

L-Gycine

0.24 ± 0.004

d

c

The values are expressed as mean ± SE (n = 2). The mean values followed by different superscripts in the same row are significantly different (p < 0.05). ND: Non detectable.



Baekjung > Daekwang. Since peanut pods mature in the ground, the phenolic compounds present in the peanut shells might be due to the self-defense mechanisms of the plants against microorganisms and oxidation in the soil (Jalili et al., 2011; Wee et al., 2007). By-products of peanuts like skin and shell contain a significant amount of phenolics and other health promoting compounds which can be used for preparing functional foods (Yu et al., 2005). The most abundant antioxidants in the diet are the polyphenols which are widespread constituents of cereals, fruits and vegetables (Pandey and Rizvi, 2009). High phenolic content might be associated with the high antioxidant activities of the peanut shells which could be considered as a potential natural antioxidant source (Yen et al., 1993). Polyphenols, a group of plant-derived compounds with several beneficial properties, have become an attractive natural antioxidant in pharmacy and cosmetics industries (Zillich et al., 2015). Polyphenolic extracts are attractive ingredients for cosmetics and pharmacy due to their beneficial bio-logical properties. 3.6. Total flavonoid content The flavonoid content of peanut shells ranged 142.6–568.0 mg QE/g (Table 3). Akwang showed the highest value of total flavonoid contents followed by Alogi. Heugttangkong had the lowest total flavonoid contents. Peanut shells contain high levels of flavonoids as they remain under the soil surface and are exposed against a number of unfavorable conditions such as fungal and other soil microorganisms attack (Vaughn, 1995). Peanut shells contain various flavonoids at different developmental stages as eriodictyol is the most predominant flavonoid during immature stage, whereas luteolin is the most predominant one in the matured peanut shells (Francisco and Resurreccion, 2008). Luteolin is a principal antioxidative component of peanut shells that increases with the maturity of peanut hulls (Yen et al., 1993). Flavonoids isolated from peanut shells could also benefit consumers’ health (De Camargo et al., 2012; Francisco and Resurreccion, 2008). Three major flavonoids; 5, 7-dihydroxychromone, eriodictyol, and luteolin; isolated from the peanut shells (Daigle et al., 1988) regulate blood glucose levels and show anticancer effects (Koo et al., 2014; Marín et al., 2017). Peanut shells contain a high amount of flavonoids which showed antimicrobial and pharmacological activities (Geetha et al., 2013). Peanut shells also showed antibacterial effects with a potential use to extend the shelf life of foods (Yu et al., 2016). 3.7. Free amino acid content Twenty-nine amino acids were analyzed in the peanut shell samples out of which eight were essential and 11 other free amino acids were not detected (Table 4). The sum of essential and total free amino acids in the peanut shells ranged from 2.16 to 13.26 mg/g and 5.76 to 34.56 mg/g, respectively. The amino acid contents play an important role in determining the quality and value of the peanut shell. Arginine, aspartic acid, glutamic acid and leucine were among the more, whereas ammonia, cystine, methionine, and tyrosine were the less abundantly found amino acids in the peanut shells. Amino acids like aspartic, histidine, glutamic, and phenylalanine are responsible for enhancing the flavor in peanuts (Wang et al., 2013). Glutamic acid, arginine, proline, and leucine help increase growth of skeletal muscles, regulate gene expression and lessen unnecessary body fat (Wu, 2009). Phenylalanine, leucine, isoleucine, and valine are the neuro-transmitters which can influence the function of central nervous system and improve brain performance (Fernstrom, 2013). Baekjung showed the highest amount of essential as well as total amino acid contents followed by Alogi. Daekwang had the lowest essential and

5

total amino acid contents. Amino acids are safe and biodegradable ingredients and have been used in cosmetics for many decades. These are the key components of the natural moisturizing factors and contribute major in skin care ingredients (Lintner, 2007). The amino acids of peanut shells are plant based protein and carry unique additional components like bioactive compounds and fibers which give a new formulation of high protein-rich ingredients in food and cosmetics industries (Arya et al., 2016). 4. Conclusions Peanut shells, the by-product of peanut crop and which are generally discarded as wastes, showed high antioxidant potentials (DPPH, ABTS, SOD-like activity and reducing power) with considerable amounts of total polyphenol, flavonoid and amino acid contents. Results of the present study indicate that the peanut shells could be utilized in various industrial applications including food, pharmaceutical and cosmetics. However, further studies may be needed to declare peanut shells as safe food ingredients. Acknowledgement This research was supported by Kyungpook National University research fund, 2017. Conflicts of interest Authors declare no any conflict of interest.

References Arya, S.S., Salve, A.R., Chauhan, S., 2016. Peanuts as functional food: a review. J. Food Sci. Technol. 53 (1), 31–41. https://doi.org/10.1007/s13197-015-2007-9. Attree, R., Du, B., Xu, B., 2015. Distribution of phenolic compounds in seed coat and cotyledon, and their contribution to antioxidant capacities of red and black seed coat peanuts (Arachis hypogaea L.). Ind. Crops Prod. 67, 448–456. https://doi.org/ 10.1016/j.indcrop.2015.01.080. Barbulova, A., Colucci, G., Apone, F., 2015. New trends in cosmetics: By-products of plant origin and their potential use as cosmetic active ingredients. Cosmetics 2 (2), 82–92. https://doi.org/10.3390/cosmetics2020082. Bertioli, D.J., Seijo, G., Freitas, F.O., Valls, J.F., Leal-Bertioli, S.C., Moretzsohn, M.C., 2011. An overview of peanut and its wild relatives. Plant Genet. Resour. 9 (01), 134–149. https://doi.org/10.1017/S1479262110000444. Burnett, C.L., Heldreth, B., Bergfeld, W.F., Belsito, D.V., Hill, R.A., Klaassen, C.D., et al., 2013. Safety assessment of a-amino acids as used in cosmetics. Int. J. Toxicol. 32 (6_suppl), 41S–64S. https://doi.org/10.1177/1091581813507090. Daigle, D., Conkerton, E., Sanders, T., Mixon, A., 1988. Peanut hull flavonoids: their relationship with peanut maturity. J. Agric. Food Chem. 36 (6), 1179–1181. https://doi.org/10.1021/jf00084a013. De Camargo, A.C., de Souza Vieira, T.M.F., Regitano-d’Arce, M.A.B., Alencar, S.M.d., Calori-Domingues, M.A., Fillet Spoto, M.H., Canniatti-Brazaca, S.G., 2012. Gamma irradiation of in-shell and blanched peanuts protects against mycotoxic fungi and retains their nutraceutical components during long-term storage. Int. J. Mol. Sci. 13 (9), 10935–10958. https://doi.org/10.3390/ ijms130910935. Duh, P.D., Yen, G.C., 1997. Antioxidant efficacy of methanolic extracts of peanut hulls in soybean and peanut oils. J. Am. Oil Chem. Soc. 74 (6), 745–748. https:// doi.org/10.1007/s11746-997-0212-z. Duncan, C.E., Gorbet, D.W., Talcott, S.T., 2006. Phytochemical content and antioxidant capacity of water-soluble isolates from peanuts (Arachis hypogaea L.). Food Res. Int. 39 (8), 898–904. https://doi.org/10.1016/ j.foodres.2006.05.009. Działo, M., Mierziak, J., Korzun, U., Preisner, M., Szopa, J., Kulma, A., 2016. The potential of plant phenolics in prevention and therapy of skin disorders. Int. J. Mol. Sci. 17 (2), 160. https://doi.org/10.3390/ijms17020160. El-Baroty, G.S., Khalil, M.F., Mostafa, S.H.A., 2014. Natural antioxidant ingredient from by-products of fruits. Am. J. Agric. Biol. Sci. 9 (3), 311–320. https://doi.org/ 10.3844/ajabssp.2014.311.320. FAOSTAT, 2014. FAO Statistical Databases. http://www.fao.org/faostat/en/ (acessed 02 June 2017). Fengweng, S., 2008. Research progress on the comprehensive utilization of peanut hull. J. Shandong Forest. Sci. Technol. 6, 84–88.


6


Fernstrom, J.D., 2013. Large neutral amino acids: dietary effects on brain neurochemistry and function. Amino Acids 45 (3), 419–430. https://doi.org/ 10.1007/s00726-012-1330-y. Fidrianny, I., Puspitasari, N., Singgih, W., 2014. Antioxidant activities, total flavonoid, phenolic, carotenoid of various shells extracts from four species of legumes. Asian J. Pharm. Clin. Res. 7 (4), 42–46. Francisco, M.L.D.L., Resurreccion, A.V.A., 2008. Functional components in peanuts. Crit. Rev. Food Sci. Nutr. 48 (8), 715–746. https://doi.org/10.1080/ 10408390701640718. Gao, F., Ye, H., Yu, Y., Zhang, T., Deng, X., 2011. Lack of toxicological effect through mutagenicity test of polyphenol extracts from peanut shells. Food Chem. 129 (3), 920–924. https://doi.org/10.1016/j.foodchem.2011.05.046. Geetha, K., Ramarao, N., Kiran, R.S., Srilatha, K., Mamatha, P., Rao, V.U., 2013. An overview on Arachis hypogaea plant. Int. J. Pharm. Sci. Res. 4 (12), 4508–4518. Jahurul, M., Zaidul, I., Ghafoor, K., Al-Juhaimi, F.Y., Nyam, K.L., Norulaini, N., et al., 2015. Mango (Mangifera indica L.) by-products and their valuable components: a review. Food Chem. 183, 173–180. https://doi.org/10.1016/ j.foodchem.2015.03.046. Jalili, A., Alipour, S., Sadegzadeh, A., 2011. Antioxidant and antiradical activities of phenolic extracts from Juglanse regia hulls and shells. Int. Res. J. Plant Sci. 1 (11), 282–289. Koo, H.J., Kwak, J.H., Kang, S.C., 2014. Anti-diabetic properties of Daphniphyllum macropodum fruit and its active compound. Biosci. Biotechnol. Biochem. 78 (8), 1392–1401. https://doi.org/10.1080/09168451.2014.923289. Lee, J.S., Bok, S.H., Park, Y.B., Lee, M.K., Choi, M.S., 2003. 4-Hydroxycinnamate lowers plasma and hepatic lipids without changing antioxidant enzyme activities. Ann. Nutr. Metab. 47 (3–4), 144–151. https://doi.org/10.1159/000070037. Lee, M.Y., Kim, J.H., Choi, J.N., Kim, J., Hwang, G.S., Lee, C., 2010. The melanin synthesis inhibition and radical scavenging activities of compounds isolated from the aerial part of Lespedeza cyrtobotrya. J. Microbiol. Biotechnol. 20 (6), 988–994. https://doi.org/10.4014/jmb.0905.05054. Lintner, K., 2007. Peptides, amino acids and proteins in skin care? Cosmetics Toiletries 122 (10), 26–34. Marín, L., Gutiérrez-del-Río, I., Yagüe, P., Manteca, Á., Villar, C.J., Lombó, F., 2017. De novo biosynthesis of apigenin, luteolin, and eriodictyol in the actinomycete Streptomyces albus and production improvement by feeding and spore conditioning. Front. Microbiol. 8 (921). https://doi.org/10.3389/ fmicb.2017.00921. Nakamura, K., Ogasawara, Y., Endou, K., Fujimori, S., Koyama, M., Akano, H., 2010. Phenolic compounds responsible for the superoxide dismutase-like activity in high-brix apple vinegar. J. Agric. Food Chem. 58 (18), 10124–10132. https://doi. org/10.3389/fmicb.2017.00921. Nepote, V., Grosso, N.R., Guzman, C.A., 2002. Extraction of antioxidant components from peanut skins. Grasas Aceites 53 (4), 391–395. Pandey, K.B., Rizvi, S.I., 2009. Plant polyphenols as dietary antioxidants in human health and disease. Oxid. Med. Cell. Longev. 2 (5), 270–278. https://doi.org/ 10.4161/oxim.2.5.9498. Prabhakar, M., Shah, A.U.R., Rao, K.C., Song, J.I., 2015. Mechanical and thermal properties of epoxy composites reinforced with waste peanut shell powder as a bio-filler. Fiber Polym. 16 (5), 1119–1124. https://doi.org/10.1007/s1222-0151119-1. Qiu, J., Chen, L., Zhu, Q., Wang, D., Wang, W., Sun, X., et al., 2012. Screening natural antioxidants in peanut shell using DPPH-HPLC-DAD-TOF/MS methods. Food Chem. 135 (4), 2366–2371. https://doi.org/10.1016/j.foodchem.2012.07.042. Radhakrishnan, R., Pae, S.B., Lee, B.K., Baek, I.Y., 2013. Evaluation of luteolin from shells of Korean peanut cultivars for industrial utilization. Afr. J. Biotechnol. 12 (28). https://doi.org/10.5897/AJB2013.12911. Ramırez-López, E., Corona-Hernández, J., Dendooven, L., Rangel, P., Thalasso, F., 2003. Characterization of five agricultural by-products as potential biofilter carriers. Bioresour. Technol. 88 (3), 259–263. https://doi.org/10.1016/S09608524(02)00315-2. Rosales-Martínez, P., Arellano-Cárdenas, S., Dorantes-Álvarez, L., García-Ochoa, F., López-Cortez, M.d.S., 2014. Comparison between antioxidant activities of phenolic extracts from Mexican peanuts, peanuts skins, nuts and pistachios. J. Mex. Chem. Soc. 58 (2), 185–193. Rui-he, M., 2010. Study on comprehensive utilization of peanut hull. Modern Agric. Sci. Technol., 04 Sanjukta, S., Rai, A.K., Muhammed, A., Jeyaram, K., Talukdar, N.C., 2015. Enhancement of antioxidant properties of two soybean varieties of Sikkim himalayan region by proteolytic Bacillus subtilis fermentation. J. Funct. Foods 14, 650–658. https://doi.org/10.1016/j.jff.2015.02.033. Scalbert, A., Manach, C., Morand, C., Rémésy, C., Jiménez, L., 2005. Dietary polyphenols and the prevention of diseases. Crit. Rev. Food Sci. Nutr. 45 (4), 287–306. https://doi.org/10.1080/1040869059096.

Singleton, V.L., Orthofer, R., Lamuela-Raventós, R.M., 1999. Analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent. Methods Enzymol. 299, 152–178. https://doi.org/10.1016/S0076-6879 (99)99017-1. Soto, M.L., Falqué, E., Domínguez, H., 2015. Relevance of natural phenolics from grape and derivative products in the formulation of cosmetics. Cosmetics 2 (3), 259–276. https://doi.org/10.3390/cosmetics2030259. Torkashvand, A.M., Alidoust, M., Khomami, A.M., 2015. The reuse of peanut organic wastes as a growth medium for ornamental plants. Int. J. Recycl. Org. Waste Agric. 4 (2), 85–94. https://doi.org/10.1007/s40093-015-0088-0. USDA, 2017. Full report (all nutrients): 45213163. In: Shell peanuts, UPC: 011161033875. https://ndb.nal.usda.gov/ndb/ (accessed 22 June 2017). Vaughn, S., 1995. Phytotoxic and antimicrobial activity of 5, 7-dihydroxychromone from peanut shells. J. Chem. Ecol. 21 (2), 107–115. https://doi.org/10.1007/ BF02036645. Wang, L., Wang, Q., Liu, H., Liu, L., Du, Y., 2013. Determining the contents of protein and amino acids in peanuts using near-infrared reflectance spectroscopy. J. Sci. Food Agric. 93 (1), 118–124. https://doi.org/10.1002/jsfa.5738. Wee, J.H., Moon, J.H., Eun, J.B., Chung, J.H., Kim, Y.G., Park, K.H., 2007. Isolation and identification of antioxidants from peanut shells and the relationship between structure and antioxidant activity. Food Sci. Biotechnol. 16 (1), 116–122. Wee, J.H., Park, K.H., 2001. Isolation of 4-Hydroxycinnamic acid, 3-methoxy-4hydroxycinnamic acid, and 3, 4-dihydroxybenzoic acid with antioxidative and antimicrobial activity from peanut (Arachis hypogaea). Food Sci. Biotechnol. 10 (5), 84–89. Win, M.M., Abdul-Hamid, A., Baharin, B.S., Anwar, F., Sabu, M.C., Pak-Dek, M.S., 2011. Phenolic compounds and antioxidant activity of peanut’s skin, hull, raw kernel and roasted kernel flour. Pak. J. Bot. 43 (3), 1635–1642. Wu, G., 2009. Amino acids: metabolism, functions, and nutrition. Amino Acids 37 (1), 1–17. https://doi.org/10.1007/s00726-009-0269-0. Xu, B., Chang, S., 2007. A comparative study on phenolic profiles and antioxidant activities of legumes as affected by extraction solvents. J. Food Sci. 72 (2), S159– S166. https://doi.org/10.1111/j.1750-3841.2006.00260.x. Yen, G.C., Duh, P.D., Tsai, C.L., 1993. Relationship between antioxidant activity and maturity of peanut hulls. J. Agric. Food Chem. 41 (1), 67–70. Yoo, S.H., Chang, Y.H., 2016. Volatile compound, physicochemical, and antioxidant properties of beany flavor-removed soy protein isolate hydrolyzates obtained from combined high temperature pre-treatment and enzymatic hydrolysis. Prev. Nutr. Food Sci. 21 (4), 338–347. https://doi.org/10.3746/ pnf.2016.21.4.338. Yu, J., Ahmedna, M., Goktepe, I., 2005. Effects of processing methods and extraction solvents on concentration and antioxidant activity of peanut skin phenolics. Food Chem. 90 (1), 199–206. Yu, Y., Sun, X., Gao, F., 2014. Inhibitory effect of polyphenols extracts from peanut shells on the activity of pancreatic lipase in vitro. Asian J. Chem. 26 (11), 3401– 3403. https://doi.org/10.14233/ajchem.2014.17536. Yu, Y., Wang, L., Gao, F., Zhang, S., 2016. Quantitative analysis and bacteriostasis of polyphenols extracts from peanut shells by ultrahigh pressure extraction. In: 4th International Conference on Machinery, Materials and Computing Technology, 23–24 January 2016. Hangzhou, China. Zhang, G., Hu, M., He, L., Fu, P., Wang, L., Zhou, J., 2013. Optimization of microwaveassisted enzymatic extraction of polyphenols from waste peanut shells and evaluation of its antioxidant and antibacterial activities in vitro. Food Bioprod. Process. 91 (2), 158–168. https://doi.org/10.1016/j.fbp.2012.09.003. Zhao, X., Chen, J., Du, F., 2012. Potential use of peanut by-products in food processing: a review. J. Food Sci. Technol. 49 (5), 521–529. https://doi.org/ 10.1007/s13197-011-0449-2. Zhu, H., Wang, Y., Liu, Y., Xia, Y., Tang, T., 2010. Analysis of flavonoids in Portulaca oleracea L. by UV–vis spectrophotometry with comparative study on different extraction technologies. Food Anal. Methods 3 (2), 90–97. https://doi.org/ 10.1007/s12161-009-9091-2. Zillich, O., Schweiggert-Weisz, U., Eisner, P., Kerscher, M., 2015. Polyphenols as active ingredients for cosmetic products. Int. J. Cosmetic Sci. 37 (5), 455–464. https://doi.org/10.1111/ics.12218.

Further reading Li, Y., Ma, D., Sun, D., Wang, C., Zhang, J., Xie, Y., Guo, T., 2015. Total phenolic, flavonoid content, and antioxidant activity of flour, noodles, and steamed bread made from different colored wheat grains by three milling methods. Crop J. 3 (4), 328–334. https://doi.org/10.3389/fmicb.2017.00921.
