Original Article

Antioxidant Activities of Essential Oils from Citrus × natsudaidai (Yu. Tanaka) Hayata Peels at Different Ripening Stage

Jiyoon YANG1, Won-Sil CHOI2, Su-Yeon LEE1, Minju KIM3, Mi-Jin PARK1,https://orcid.org/0000-0002-7748-3886
Author Information & Copyright
1Division of Forest Industrial Materials, Department of Forest Products and Industry, National Institute of Forest Science, Seoul 02455, Korea
2National Instrumentation Center for Environmental Management, Seoul National University, Seoul 08826, Korea
3Citrus Research Institute, Jeju 63607, Korea
Corresponding author: Mi-Jin PARK (e-mail: lionpmj@korea.kr)

Copyright 2022 The Korean Society of Wood Science & Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: May 24, 2022; Revised: Jun 13, 2022; Accepted: Jul 08, 2022

Published Online: Jul 25, 2022


The essential oil extracted from Citrus × natsudaidai (Yu. Tanaka) Hayata peels is known to have various biological properties. However, the chemical composition of essential oil is influenced by the ripening stages of fruits, which then affects related biological activities. This study investigates the antioxidant activities of essential oils extracted from Citrus × natsudaidai peels at different ripening stages (immature, mature, and overripe). The essential oils were extracted using the hydro-distillation method. As a result of gas chromatography-mass spectrometry (GC-MS) analysis, d-limonene was dominant and was increased as matured. However, γ-terpinene was decreased. The antioxidant properties and their total phenolic content (TPC) were influenced by the ripening stages. The TPC was highest in the immature stage of essential oil (1,011.25 ± 57.15 mg GAE/100 g). 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity was excellent in the immature stage (EC50 = 15.91 ± 0.38 mg/mL). 2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity was superior in overripe stage (EC50 = 20.43 ± 0.37 mg/mL). The antioxidant activity measured using ferric reducing antioxidant power (FRAP) assay showed higher values for the essential oils in immaturity (1,342.37 ± 71.07 mg Fe2+/100 g). Comprehensively, the essential oil in the immature stage showed the best antioxidant activity. Finally, knowing the chemical composition and antioxidant activity at different ripening stages will provide data for selecting the right fruit.

Keywords: Citrus × natudaidai; amanatsu; essential oil; antioxidant; fruit ripening


Citrus spp. is a large genus of flowering plants belonging to the Rutaceae family. Citrus fruits such as lemons, grapefruits, limes, oranges, tangerines, and mandarins are the most widely cultivated fruits in the world, with production increasing every year as consumer demand increases (Khan et al., 2021). This is because citrus fruits provide important nutrients such as vitamin C and other health-promoting compounds, including its distinctive flavonoids, which are beneficial for human health (Liu et al., 2012). Therefore, they provide several nutritional and health benefits and are consumed as fruits or processed products such as peels, pulps, juice, and other commercialized extracts, and used as additives in the food industry. For example, bitter orange extracts are used as additives in several beverages, desserts, sweets, drinks, and ice creams. Thus, Citrus has a substantial commercial value.

Biologically important active constituents of secondary metabolites are reported in this genus, such as limonoids, coumarins, carotenoids, alkaloids, polyphenols, and essential oils, which can be used in food, cosmetic and pharmaceutical industries (Lv et al., 2015). Among them, essential oils have various biological activities such as antioxidant, antibacterial, anti-anxiety, anti-inflammatory, anti-obesity, chemoprotective, and anti-tumor (Dosoky and Setzer, 2018; Ham et al., 2020; Jeong et al., 2017; Lee et al., 2021; Yang et al., 2019). Due to their biological properties, Citrus essential oils are widely used in the food preservation, perfume, pharmacological, and cosmetic industries (Palazzolo et al., 2013).

Citrus × natsudaidai (Yu. Tanaka) Hayata (natsudaidai) is a popular fruit with medical benefits in many countries. It contains numerous bioactive compounds such as vitamin C and flavonoids. Many flavonoids such as hesperidin, neohesperidin, naringin, nobiletin, tangeretin, and auraptene are obtained from natsudaidai, and have been studied for pharmacological properties such as anti-inflammatory, anticarcinogenic, and antioxidant, cytotoxic effects (Ahn et al., 2021; Nakayama et al., 2011; Yamaura et al., 2012). Treatment with C. × natsudaidai extract significantly attenuated the increase in ear edema and improved dermatitis scores. Additionally, the increase in serum d-ROM was attenuated by C. × natsudaidai extract. In another study, following the administration of 300 mg/kg acetaminophen, all mice died within 6 h. However, pretreatment with C. × natsudaidai extract (300 and 1,000 mg/kg) improved the survival rate to 16.7% and 33.3%, respectively, at 24 h. These results indicate that C. × natsudaidai has a relaxation effect on inflammatory.

However, it has been found that the ripening stages of fruits have influenced the chemical composition and related activities of the essential oil (El-Gamal and Ahmed, 2017; Ella Nkogo et al., 2022; Harhar et al., 2019; Manurung et al., 2019). Jonas’s study investigated the influence of the fruit maturity stage on the physicochemical properties of Jatropha seed oil and the produced biodiesel (Jonas et al., 2020). This investigation revealed that free fatty acid content and peroxide value of seed oil vary as Jatropha fruits mature from green to brown dry. The free fatty acid content in Jatropha seed oil increases continuously with seed maturity. Similarly, the peroxide value of Jatropha seed oil increases gradually with fruit maturity. Results from this investigation have revealed that using seed oil from the early stages of fruit maturity can improve the quality of seed oil and hence of derived biodiesel in contrast to the final maturity stage. Therefore, further studies on the antioxidant activity of essential oils according to ripening stages are required to make optimal use of these fruits.

The study investigates the chemical components and antioxidant activities of essential oils extracted from C. × natsudaidai peels during fruit ripening. The purpose of these results is to understand the phytochemical changes that occur during the ripening stage of Citrus × natsudaidai and to recommend the best harvesting time for bioactive compounds extraction. Finally, the presented results can serve various industries as guidelines for high-quality pharmaceuticals and foods.


2.1. Material

Citrus × natsudaidai (Yu. Tanaka) Hayata peels used in this study were collected from Citrus Research Institute (National Institute of Horticultural and Herbal Science) in Jeju Island, Korea. The samples were collected thrice (March, September, and December) according to ripening stages.

2.2. Extraction of the essential oil

To extract the essential oil from the Citrus × natsudaidai peel with that of moisture content from 80.06% to 81.37%, we used the previously used extraction method (Yang et al., 2021a). C. × natsudaidai peels (2 × 2 cm) were hydro-distillated at atmospheric pressure using a Clevenger-type apparatus. A 10 L round-bottom flask containing 1.0 kg of peels was placed in a digital heating mantle (MS-DM 608, MTOPS®, Yangju, Korea), and 5 L of distilled water was poured into it, which was then connected to the Clevenger-type apparatus. The peel was extracted for 30 h. The collected essential oils were dried over anhydrous sodium sulfate (98.5%, Cat No. 834605125, Samchun, Seoul, Korea) and filtered using a 0.45 μm membrane disk filter. The essential oils were transferred to dark vials and stored at 4°C for further analysis. The yield of the essential oils was calculated using Equation (1):

Essential oil yield  ( % ( w/w ) ) = Mass of the essential oil obtained ( g ) Mass of the oven-dry matter ( g ) × 100
2.3. GC-MS analysis

To identify the volatile components therein, the essential oils during fruit ripening were analyzed using GC-MS equipped with a VF-5MS capillary column (Table 1). These analysis conditions were based on our prior research (Yang et al., 2021b).

Table 1. GC/MS operating conditions
Column VF-5MS capillary column
(60 m × 0.25 mm, 0.25 μm; Agilent Technologies, Santa Clara, CA, USA)
GC oven 50°C, hold 5 min
10°C/min to 65°C, hold 30 min
5°C/min to 210°C, hold 10 min
20°C/min to 325°C, hold 10 min
Carrier gas He (1 mL/min, 25 psi)
Linear velocity 19.8 cm/s
Injection mode Split 1:20
Injection temperature 250°C
MS parameters FID parameters
MS ionization mode EI FID temperature 300°C
Scan time 0.2 s Hydrogen flow 35.0 mL/min
Mass range 35–550 amu Air flow 350.0 mL/min
Ion source temperature 270°C Make up flow 40.0 mL/min
Interface temperature 250°C
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The components of essential oils according to maturity stage were identified on the basis of the peaks with the highest spectral matching when the S/N ratio reached ≥ 50 in total-ion chromatography using the NIST library search program (version 11; National Institute of Standards and Technology, Gaithersburg, MD, USA). The Kovats retention index (KI) values of the individual compounds were determined based on the comparison of their relative retention times with an n-alkanes mixture (C8-C20, Cat No. 04071, Merck KGaA, Darmstadt, Germany) using the VF-5MS column. The essential oils’ components were assigned based on the comparison of their calculated KI values to literature values (e.g., NIST Chemistry WebBook).

2.4. Determination of total phenolic content (TPC)

The TPC of the essential oils was determined by the Folin-Ciocalteu method (Singleton and Rossi, 1965). Using a standard curve as a reference, the TPC was determined and represented as mg gallic acid equivalents (mg GAE/100 g).

Ethanol (≥ 99.5%, Cat No. 459836, Merck KGaA) was used to dilute the essential oils to be analyzed. Afterward, in a 10 mL volumetric flask, 500 μL of oil was added to 2.5 mL of 2N Folin-Ciocalteu reagent (eCat No. F9252, Merck KGaA) alongside 2 mL Na2CO3 (7.5%, Cat No. 222321, Merck KGaA). After incubation for 60 min at 37°C, the absorbance versus prepared blank was read at 760 nm. The standard reference curve for gallic acid was made for the following concentrations: 1, 2, 4, 6, 8, and 10 mg/mL, respectively. The correlation coefficient and regression equation were determined and expressed in mg GAE/100 g. All measurements were performed in triplicates.

2.5. DPPH free-radical scavenging capacity

The free-radical scavenging assay of 2,2-diphenyl-1-picrylhydrazyl (DPPH, Cat No. D9132, Merck KGaA) was used to examine the antioxidant properties of the essential oils. The measurement was based on the method described in (Sayuti et al., 2018). The essential oils were prepared by diluting 100 mg of peel oil in 1 mL of ethanol, producing a concentration of 1 mg/mL. The stock solution was sonicated to ensure sample homogeneity. Six other concentrations were prepared at 1, 2, 4, 6, 8, and 10 mg/mL, diluted from the 100 mg/mL stock solution. Approximately 1 mL of 0.2 mM solution of DPPH in ethanol was each added into six series of prepared concentrations (1, 2, 4, 6, 8, and 10 mg/mL) of the sample solution (4 mL). The solution was vigorously mixed and allowed to stand at room temperature for 30 minutes in the dark, after which its absorbance was measured spectrophotometrically at 517 nm using a Micro-plate spectrophotometer. Ethanol was used as blank (only ethanol) and negative control (4 mL ethanol mixed with 1 mL DPPH), while ascorbic acid was used as the standard.

2.6. ABTS radical scavenging assay

The scavenging activity of ABTS+ was conducted to determine the radical scavenger activity. The ABTS [2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), Cat No. 10102946001, Merck KGaA] radical scavenging activity of the essential oils was determined using Re et al. (1999) method. ABTS+ was generated by reacting an ABTS+ aqueous solution (7 mM) with K2S2O8 (2.45 mM, final concentration, Cat No. 216224, Merck KGaA) in the dark for 16 h and adjusting the absorbance of 734 nm to 0.7 ± 0.02 with ethanol. The sample with different concentrations (1, 2, 4, 6, 8, and 10 mg/mL) was diluted with 0.2 mL of the required amount to react with the ABTS+ solution (2 mL). After 30 min, the absorbance was measured at 734 nm. All measurements were conducted in triplicate.

2.7. Ferric reducing antioxidant power (FRAP) assay

The total antioxidant potential of the samples was determined using the ferric reducing capacity of plasma FRAP assay by Fernandes et al. (2016) as a measure of antioxidant capacity. The analysis was based on the compound’s reducing power. A potential antioxidant can reduce the ferric ions (Fe3+) to ferrous ions (Fe2+). The latter forms a blue complex (Fe2+/TPTZ) that promotes absorption at 593 nm. The FRAP reagent was prepared by mixing a solution of acetate buffer (300 mM, pH 3.6), 10 mM TPTZ (≥ 98%, Cat No. T1253, Merck KGaA) in 40 mM HCl (1 M, Cat No. H1202, TCI, Tokyo, Japan), and 20 mM FeCl3+ (97%, Cat No. 236489, Merck KGaA) at 10:1:1 (v/v/v). Reagent and sample solution were added to each well and mixed thoroughly. After 30 min, absorbance was measured at 593 nm. A standard curve was generated using different concentrations of Trolox. All solutions were used on the day of manufacture. The results were expressed as mg Trolox equivalent/100 g. Analysis was conducted in triplicate for each essential oil.

2.8. Statistical analysis

The results of the tests were repeated in triplicate, and results were presented as mean ± standard deviations. Statistical analysis was conducted using R x64 (ver.4.0.3).


3.1. Yield and chemical composition

The yield of the essential oils largely varied with the ripening stages. Among the essential oils, immaturity showed the highest yield (5.88 ± 0.23%) followed by overripe (3.62 ± 0.12%) and maturity (2.06 ± 0.09%). According to a previous study, the yield of immature C. × natsudaidai was 0.6%, and that of matured C. × natsudaidai peel was 1.7% (Baik et al., 2008; Oh et al., 2007). Despite the same ripening stage, the essential oil was extracted using the steam distillation method for only 6 hours, resulting in a big difference in yield. This difference in yield is due to the extraction time (about 30 h).

The chemical composition of the essential oils during fruit maturation was identified by GC-MS. As shown in Table 2, the chemical composition at different stages of ripening was identified by GC-MS.

Table 2. Chemical composition of the essential oils extracted from Citrus × natsudaidai peels during fruit ripening (only components with S/N > 50)
Classification Compound name1) Immaturity Maturity Overripe KI2)
Monoterpene hydrocarbons α-Pinene 0.57 0.46 0.52 926
β-Pinene 0.17 0.21 0.21 970
β-Myrcene 1.17 1.09 1.30 986
α-Terpinene 0.17 0.10 0.08 1,024
Cymene 0.15 0.21 0.36 1,033
D-Limonene 86.44 90.34 90.45 1,041
β-Ocimene 0.27 0.19 0.23 1,057
γ-Terpinene 6.32 5.03 4.75 1,068
Terpinolene 0.67 0.37 0.34 1,089
Oxygenated monoterpenes Linalool oxide 0.26 0.11 0.12 1,078
Linalool 0.32 0.17 0.11 1,099
β-Terpineol 0.41 0.13 0.10 1,146
Terpinen-4-ol 0.25 0.15 0.11 1,179
α-Terpineol 2.16 0.77 0.61 1,194
Sesquiterpene hydrocarbons β-Elemene - 0.09 0.06 1,395
Oxygenated sesquiterpenes (+)-Nootkatone - - 0.14 1,828
Organic compound Octanal 0.15 0.04 - 1,003
Unknown compound 0.49 0.52 0.44

1) Compounds are listed in order of their elution from a VF-5MS column.

2) Retention index experimentally determined on VF-5MS column with reference to n-alkanes (C8–C20).

KI: Kovats retention index.

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As a result, the proportion of the constituents in the essential oil was also different. D-Limonene was the major constituent in all oil samples (86.44% to 90.45%), followed by γ-terpinene and β-myrcene ranged between 4.75% to 6.32% and 1.09% to 1.30%, respectively. According to Vekiari et al. (2002), harvesting time is a critical parameter influencing the chemical compositions of the essential oil significantly. As C. × natsudaidai matured, the contents of β-pinene, cymene, and d-limonene were increased. On the other hand, the contents of α-terpinene, γ-terpinene, terpinolene, linalool, β-terpineol, terpinene-4-ol, α-terpineol, and octanal, were gradually decreased. Dugo et al. investigated the seasonal variation of the chemical composition of the essential oil extracted from two cultivars, Sicilian mandarin (Citrus × deliciosa Tenore. cv Avana and Tardivo di Ciaculli), and reported an increase of limonene content from September to February (from immature stage to mature stage) (Dugo et al., 2011). In contrast to the behavior observed from October to February, limonene content decreased at the overripe stage (from February to March). This result showed a similar tendency to our study result. According to Dugo et al., limonene is compensated by the other constituents of the monoterpene hydrocarbons, so it decreases sharply in March when each monoterpene hydrocarbon exhibits the same decreased behavior. Furthermore, it was found that the yield and composition of these essential oils were different depending on soil properties (Moretti et al., 1998).

3.2. Total phenolic content (TPC)

Phenolic compounds are related to several biological roles, such as activities of antioxidant free radical scavenging (Salar and Seasotiya, 2011). We were determined to compare the TPC of essential oils according to the ripening stages.

The results, as shown in Table 3 indicated that TPC in all essential oils was seen to be significantly different amounts. Among them, the highest TPC was found in immaturity (1011.25 ± 57.15 mg/100 g) followed by overripe (961.76 ± 124.55 mg/100 g) and maturity (895.77 ± 69.99 mg/100 g). One-way ANOVA analysis was performed to prove whether TPCs of essential oils according to the ripening stage were significantly different. As a result, the ripening stages do not make significant differences in TPC (P = 0.4503). The TPC contents decreased in the ripening stage but increased in overripe. That can be related to a shift in the biosynthetic pathway of secondary metabolites toward the production of essential oils in the plant. When the plant encounters oxidative stress due to a sudden change of temperature in summer and early winter, the biosynthetic pathway of secondary metabolites in the plant is directed toward the production of essential oils rather than phenolic compounds (Boveiri Dehsheikh et al., 2019). These phytochemical compounds support bioactivity in medicinal plants and are thus responsible for the antioxidant activities of the essential oils extracted from C. × natsudaidai peels according to ripening stages (Altemimi et al., 2017).

Table 3. Total phenolic content in essential oils during fruit ripening
Stage properties\Maturity Immaturity Maturity Overripe
mg GAE/100 g 1,011.25 ± 57.15 895.77 ± 69.99 961.76 ± 124.55
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3.3. DPPH radical scavenging ability

In this analysis, the abilities of the test compounds to donate hydrogen atoms or electrons were measured spectrophotometrically. Table 4 shows the results of the DPPH inhibition assay using different essential oils and control (Ascorbic acid).

Table 4. DPPH radical scavenging effects of the essential oils extracted from Citrus × natsudaidai peels according to ripening stages
Immaturity Maturity Overripe Ascorbic acid
DPPH EC50 (mg/mL) 15.91 ± 0.38 16.98 ± 0.40 16.21 ± 0.32 0.064 ± 0.002

DPPH: 2,2-diphenyl-1-picrylhydrazyl.

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It showed that all the essential oils can reduce the pink-colored free radical to yellow-colored diphenyl picrylhydrazine, indicating that these essential oils possessed DPPH radical scavenging activity. The EC50 values of DPPH free-radical scavenging capacity were 15.91 ± 0.38, 16.98 ± 0.40, and 16.21 ± 0.32 mg/mL for immaturity, maturity, and overripe, respectively. The mechanism of the DPPH assay depends on the structural conformation of the antioxidant. Some compounds react very quickly with DPPH·, reducing the number of DPPH· molecules equal to the hydroxyl groups (Bondet et al., 1997). In Table 2, the proportion of oxygenated terpene components in the essential oil at the immaturity period is higher than in other ripening stages. In particular, the proportion of α-terpineol was high at 2.16% in the immaturity stage, but it significantly reduced as the maturation stage progressed. The proportion of other oxygenated monoterpene-based components also gradually decreased as the C. × natsudaidai matured. This was consistent with the DPPH radical scavenging ability. Also, this tendency was consistent with the change in the proportion of monoterpene components (α-pinene, β-ocimene, and linalool oxide). Choi et al. (2000) were investigated thirty-four species of citrus essential oils and their components for radical scavenging activities using DPPH assay (Choi et al., 2000). Citrus ichangensis, Citrus × aurantiifolia, and Citrus limon showed higher radical-scavenging activities than other citrus cultivars. These excellent radical scavenging activities were found to be γ-terpinene and terpinolene. Therefore, the high radical scavenging ability in the immature stage is due to the higher proportion of γ-terpinene and terpinolene than in other stages.

3.4. ABTS radical scavenging assay

Although the DPPH· free radical is ubiquitously used to estimate the potential free radical scavenging activity of natural products, the ABTS+ free radical is commonly used when issues of solubility of interference arise, and the use of DPPH based assay becomes inappropriate (Medini et al., 2011). In Table 5, the results of ABTS radical scavenging activity of peel essential oils according to ripening stages.

Table 5. ABTS radical scavenging effects of essential oils extracted from Citrus × natsudaidai peels according to ripening stages
Immaturity Maturity Overripe Ascorbic acid
ABTs EC50 (mg/mL) 22.43 ± 0.45 26.82 ± 0.48 20.43 ± 0.37 0.066 ± 0.001

ABTS: 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid).

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In the determination of ABTS radical scavenging capacity, the EC50 values of immaturity (22.43 ± 0.45 mg/mL), maturity (26.82 ± 0.48 mg/mL), and overripe (20.43 ± 0.37 mg/mL) were much higher than those of ascorbic acid (0.066 ± 0.001 mg/mL). The overripe stage showed the highest ABTS radical scavenging activity compared to the other stages. For ABTS, no correlation between EC50 and total phenols was found. However, the antioxidant activity was low in the maturity stage, as shown in the DPPH results. The ABTS radical scavenging activity was similar to the change of β-myrcene, and it is judged that β-myrcene affects the ABTS radical scavenging activity. In a previous study, rosemary essential oil had great free radical scavenging capacity; it was confirmed that myrcene contributed significantly to the free radical scavenging ability of rosemary essential oil (Ojeda-Sana et al., 2013). In vivoβ-myrcene demonstrate antioxidant effect (Bonamin et al., 2014). The antioxidant effects of orally administered β-myrcene against ethanol-induced gastric ulcers in male Wistar rats were confirmed. The β-myrcene showed antioxidant enzyme activity from the glutathione reductase system as evidenced by the decreased activity of superoxide dismutase (SOD) and increased levels of glutathione peroxidase, glutathione reductase, and total glutathione in gastric tissue. Future studies investigating antioxidant activity of β-myrcene, need to conduct appropriate dosage levels that have therapeutic effects in humans.

3.5. Radical scavenging ability of essential oils using ferric reducing antioxidant power (FRAP)

The FRAP assay, which provides fast reproducible results, measures the reducing potentials of an antioxidant reacting with a ferric tripyridyltriazine (Fe3+-TPTZ) complex to produce colored ferrous tripyridyltriazine (Fe2+-TPTZ). The results of the FRAP assay using different essential oils are shown in Table 6.

Table 6. Radical scavenging effects of the essential oils extracted from Citrus × natsudaidai peels according to ripening stages
Stage properties\Maturity Immaturity Maturity Overripe
mg Fe(II)/100 g 1,342.37 ± 71.07 815.21 ± 29.39 1,417.68 ± 0.00
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According to ripening stages, most essential oils showed reducing power from 815.21 ± 29.39 mg Fe(II)/100 g in maturity stage to 1,417.68 ± 0.00 mg Fe(II)/100 g in the overripe stage. The highest reducing power (FRAP) was shown in overripe and the reducing power in immaturity is comparable but less than the reducing power in overripe. This FRAP away tendency was similar as shown in the ABT results. In a previous study, the antioxidant activities of different 15 species flavonoids were measured by the FRAP assay (Firuzi et al., 2005). As a result, quercetin, fisetin, myricetin, and kaempferol were the highest reducing power. It has been shown that hydroxyl groups and especially catechol moiety, 3-OH, and 2,3-double bonds are the most important factors in determining high antioxidant activity. The proportion of β-myrcene is a constituent that shows a similar tendency compared to reducing power among the components in essential oils for each maturation stage. Since β-myrcene has a 2,3-double bond structure, it is considered a component is contributing to the high antioxidant activity of essential oils in the overripe.


This study provides useful information on the ripening stages of the quality and antioxidant activities of essential oil extracted from C. × natsudaidai peels. Our results revealed that the ripening stages affect the essential oil’s constituents and antioxidant activities. The total polyphenol contents are closely connected to the antioxidant activity. The relationship between polyphenol contents and antioxidant activity was observed in the results of this study. The essential oil in the immaturity stage was more susceptible to accelerated oxidation than the maturity and overripe stages. Therefore, understanding the chemical composition and antioxidant activities according to the ripening stages can help producers in selecting the best time to harvest plants and produce plant products richer in the required compounds for use in the pharmaceutical and food industries.


No potential conflict of interest relevant to this article was reported.


This research was funded by the National Institute of Forest Science grant number ‘FP0701-2021-01-2021’.



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