Efficacy of sweet orange peels (citrus sinensis l.) 0.1% extract cream on improvement of axillary postinflammatory hyperpigmentation

Introduction

The trend of having even and bright skin was considered attractive and widely known as a sign of beauty and youth in several countries.¹ Skin hyperpigmentation was usually a complaint, and 8.5% of dermatologic consultation was because of it. Hyperpigmentation is defined as an increasing accumulation and production of melanin or increasing in melanocytes amount.² Axillae are one of the common areas to experience hyperpigmentation.^3,4 Hyperpigmentation in the skin fold, such as the axilla, is known as acquired hyperpigmentation due to trauma and repeated irritation from hair plucking, shaving, the cleaning method, tight clothes, or the use of deodorant and antiperspirant.^4,5

Currently, the treatment of axillary hyperpigmentation often does not give satisfactory results and becomes a challenge in its implementation. The target treatments for hyperpigmentation are photoprotection and using agents that can disrupt melanogenesis and reduce excessive melanin. Several therapies that have been introduced to treat hyperpigmentation include topical whitening agents, chemical peeling, oral agents, microdermabrasion, microneedle, and laser therapy.^6,7

Extract from plants as skin whitening has been used in traditional medicine in Indonesia. Orange was one of the most common fruits cultivated in Indonesia. Berastagi Highland located in North Sumatera, Indonesia was well known as the center of oranges commodity and sweet orange was a flagship product. Sweet orange (Citrus sinensis L.) has a chemical composition of ascorbic acid, vitamin E, vitamin A, and polyphenols. The whitening effect of sweet orange, one of which is the ascorbic acid, was due to the mechanism that decreases oxidized dopaquinone, suppression of NF-kß and TNF-α, and photoprotection.^6,8 Sweet orange peel extract also contains components that have antioxidant, antiinflammation, and anti-tyrosinase effects. Tyrosinase was a key enzyme in melanogenesis. Its function is to catalyze a reaction in melanin biosynthesis from tyrosine in melanin. Nobiletin, one of the sweet orange peel components, is a tyrosinase inhibitor.^8–10 Melanogenesis inhibition can also happen because sweet orange peel extract contains flavonoids.¹¹ Yoshizaki, Hashizume and Masaki found that polymethoxyflavones extracted from orange peel can suppress the localization from tyrosinase to melanosome and simultaneously inhibition of melanogenesis due to organelle cell acidification, including melanosome.^12,13 This study aimed to determine the efficacy of sweet orange peel extract cream on axillary hyperpigmentation.

Methods

This study is a quasi-experimental study with a pretest–posttest design group carried out from August 2022 to December 2022 at the Department of Dermatology and Venereology, Prof. Dr. Chairuddin Panusunan Lubis, Universitas Sumatera Utara Hospital. All subjects had signed informed consent prior to participating in this study and consent for publication was obtained, which was conducted in accordance with the Declaration of Helsinki. This study was conducted after approval from the health research ethics committee No: 658/KEPK/USU/2022 on 25 July 2022 obtained from the University of North Sumatera Research Ethics Committee.

Sweet orange fruit is obtained from Brastagi Highland, North Sumatera, then the process of 0.1% sweet orange peel extract cream is carried out at the Medicinal Plant Research and Development Laboratory of Indonesian Herbal Traditional Medicine Association, Medan.

This study subjects were axillary hyperpigmentation patients, 32 of them were female, aged 18-35 years, who came to the outpatient clinic of the Department of Dermatology and Venereology, Prof. Dr. Chairuddin Panusunan Lubis, Universitas Sumatera Utara Hospital, Indonesia. All participants were evaluated through anamnesis and dermatological examination. Participants were omitted if they were pregnant or breastfeeding, had received topical care products containing retinoids and their derivatives, hydroquinone, azelaic acid, kojic acid, antioxidants, vitamin C, other depigmenting agents, had received oral products such as carotenoid, glutathione, melatonin or tranexamic acid, had received interventions such as chemical peeling, microneedle or laser within the past month. Patients were excluded from the study if they did not use the cream for three consecutive days and the total use of the cream was less than seven weeks.

In this study, subjects were asked to apply one fingertip unit of cream on each axilla every morning and night and evaluated every two weeks. The melanin index was assessed before and after using the 0.1% sweet orange peel extract cream, and clinical evaluation was assessed with Physician Global Assessment (PGA). In addition, this study evaluated side effects, including dry skin, desquamation, erythema, burning, and itching, and the participants’ satisfaction.

All data collected from weeks 0, 2, 4, 6, and 8 were analyzed using SPSS version 22.0 software. They were analyzed using the Shapiro-Wilk normality test. The Friedman test was used to compare the melanin index before and after the application of 0.1% sweet orange peel extract cream because the data were not normally distributed. A p-value <0.05 was considered significant.

Results

In this study, all participants were females, and most were in the age range of 18-25 years (65.6%) (Table 1).²⁶ The mean age of the subjects was 25.31 years, with the youngest at 19 and the oldest at 34. After the data were collected, the Shapiro-Wilk normality test was carried out, which showed that the data had an abnormal distribution, so it was continued with the Friedman test to assess the comparison of lesions before and after the application of 0.1% sweet orange peel extract cream. At the beginning of the study, the average value of the melanin index was 349.04±109.84 AU. After using sweet orange peel extract cream for eight weeks, a significant decrease in melanin index was found to be 253.06±96.36 AU. The p-value obtained through the Friedman test is <0.001 (Table 2).

Physician Global Assessment (PGA) was carried out to evaluate the clinical improvement at the end of the study. It was scored as poor (0–25%), mild (26–50%), good (51-75%), or excellent (>75%). The majority of the subjects had mild improvement (68.8%), followed by good improvement (25%) (Table 3). In this study, no side effects were noted in all participants, and all were satisfied with the application of 0.1% sweet orange peel extract cream.

Discussion

The subjects in this study were all female, the majority aged 18-25 years. This study was in accordance with a study conducted by Castanedo-Cazares et al., which shown that the mean of subjects with axillary hyperpigmentation was 21.7±1.6 years.⁵ In a study by Jusuf reported that skin hypermelanosis conditions such as postinflammatory hyperpigmentation is a cosmetic complaint that can affect patients’ quality of life, and females are most likely to come and seek treatment.¹⁴

There has been no single therapy that is truly satisfactory in getting rid of axillary hyperpigmentation. This research is a preliminary study on sweet orange peel extract’s use to improve axillary hyperpigmentation. The result of this study indicates that 0.1% sweet orange peel extract cream can improve the pigmentation seen through decreasing in melanin index from 349.04 AU to 253.06 AU at the end of the study. Improvement of hyperpigmentation can occur due to several components from sweet orange peel extract.

Melanin is an essential component in skin, eye and hair color, synthesized in melanosomes that transfer from melanocytes. Hyperactivity and abnormal synthesis in melanocytes, as well as melanin accumulation, can cause hyperpigmentation in the skin.^15–17 Potential targets of skin depigmentation agents include melanocyte stimulation inhibitors, tyrosinase enzyme inhibitors, melanosome transfer inhibitors, and degradation of melanin formed in keratinocytes.¹⁸

Flavonoids, a bioactive component in sweet orange peel, can act as a promising whitening agent through tyrosinase enzyme inhibition that controls melanin production.^15,19 All flavonoids inhibit tyrosinase enzymes by their ability to chelate copper from active sites. Badria and el Gayyar also found that flavonoid contains a keto group that had potent tyrosinase inhibition activity. So that it can explain the similarity between the dihydroxyphenyl group in L-DOPA and the keto group in flavonoid.²⁰ Hesperidin, a bioflavonoid in citrus peels, showed potent anti-tyrosinase activity in melanoma cell B16 that causes melanin synthesis inhibition without cytotoxicity.²¹ Yoshizaki, Hashizume and Masaki found that polymethoxyflavone extracted from orange peel can suppress the localization from tyrosinase to melanosome and simultaneously inhibit melanogenesis.¹³

Cellular oxidative stress was formed because of toxic hydrogen peroxide (H₂O₂) and reactive oxygen species (ROS) on the skin. As a result, ROS will accumulate and induce the melanogenesis process through interaction with the tyrosinase enzyme. Antioxidants’ role in controlling and minimizing the formation of free radicals in the skin by neutralizing, decreasing harmful radicals, and stimulating free radical degradation. The antioxidant also has the potential to improve hyperpigmentation by interaction with o-quinones, thus avoiding the oxidative polymerization of melanin intermediates or with copper at the active site of tyrosinase. In addition, antioxidant agents can regulate the signaling process by scavenging ROS in the skin.²²

All study subjects did not experience side effects such as dry skin, desquamation, erythema, burning, or itching after eight weeks of using the 0.1% sweet orange (Citrus sinensis L.) peel extract cream. According to the current study, Dosoky and Setzer showed that sweet orange essential oil neither causes irritation nor sensitizing in the skin at an 8% concentration.²³ In addition, there was noted clinical improvement, and all study subjects were satisfied with the pigmentary changes in axillary hyperpigmentation. Postinflammatory hyperpigmentation can cause emotional stress, so subjective evaluation of treatment efficacy is essential.^24,25 From this result, we concluded that using a 0.1% sweet orange (Citrus sinensis L.) peel extract cream was safe, well tolerated, and provided a good satisfaction.

This study still has limitations, whereas the preliminary study cannot exclude confounding factors from study subjects. Nevertheless, the data in this study can be used as primary data for further study, and further study with a randomized controlled trial design is needed to further evaluate the efficacy of sweet orange peel extract against axillary hyperpigmentation.

Conclusion

The 0.1% sweet orange (Citrus sinensis L.) peel extract cream can improve pigmentation in axillary hyperpigmentation. This current study shows that sweet orange peel was effective and has the potential to be used as axillary hyperpigmentation therapy.

Ethics and consent

This study was conducted after approval from the health research ethics committee No: 658/KEPK/USU/2022 on 25 July 2022 obtained from the University of North Sumatera Research Ethics Committee. All subjects had signed informed consent prior to participating in this study and consent for publication was obtained, which was conducted in accordance with the Declaration of Helsinki.

Author contributions

All authors contributed to the entire process of this study, from the preparation, data collection, and analysis, as well as drafting until the approval for publication of this manuscript.