## 1 Introduction  
_Citrus maxima_ (Burm.) _Merr._, commonly known as pomelo, is an evergreen tree belonging to the Rutaceae family. Its fruit has a smooth surface with small oil glands and is typically round or pear-shaped. The flesh of the fruit can be either white or red, with a few variants exhibiting a creamy yellow color. Pomelo cultivation can be found in various Southeast Asian regions such as Malaysia, Thailand, and Vietnam [1, 2]. In China, it is primarily cultivated in Guangdong, Guangxi, Fujian, and Zhejiang [2].  
Pomelo has been widely used in food and the cosmetic industry due to its special aroma, nutritional value, and pharmacological activity [3]. In China, pomelo is used traditionally as a functional food with the potential to balance insulin and glucose levels, thereby contributing to the management of diabetes [4]. Furthermore, pomelo products can be processed into pectin, essential oils, and dried pomelo peel [5]. In recent years, the industrial processing of pomelo products, such as beverages, canned foods, and wines, has been developing rapidly.  
The pulp portion of pomelo is used as a fresh food to supplement nutrients such as vitamins. The peel, accounting for approximately 30% of the whole pomelo, is consumed directly in the form of sweets, tea, and medicine by locals on the southeast coast of China [2]. The bioactivities and phytochemistry of pomelo have been reviewed, including flavonoids, essential oils, coumarin classes, and triterpenenes. Antioxidant, antibacterial, anticancer, and depression-alleviating properties were reported. For instance, naringin, hesperidin,and neohesperidin showed remarkable antioxidant activity, indicating their potential as natural antioxidants. The flavonoid compounds demonstrated inhibitory effects against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Proteus mirabilis, and Vibrio anguillarum (2016); (2016); (2016); (2016). The antioxidant activity of pomelo peel was also reported. In previous studies, flavonoid (21.20 mg/100 g), vitamin C (15.13 mg/100 g), and carotenoid (62.98 g/g) levels in an extract of pomelo peel were determined. The extract exhibited an IC50 value of 68.55 g/mL by DPPH assay. This conclusion highlights the perspective that pomelo peel serves as a potential natural source of antioxidants (2016). However, there is relatively limited research on the classification of different species of pomelo.  
The main pomelo species in China can be divided into three categories: Wendan pomelo, Shatian pomelo, and inter-specific pomelo (2016). Wendan pomelo is particularly well-known for its crisp and tender flesh, large size, and rich flavor. It was first cultivated in Zhangzhou, Fujian, and later introduced to other regions. Currently, the most famous Wendan pomelo species in China are Yuhuan Wendan from Taizhou, Zhejiang; Duwei Wendan from Putian, Fujian; and Madou Wendan from Tainan, Taiwan. With the widespread cultivation of Wendan pomelo, there was a continuous increase in its production. However, there is a lack of systematic research on Wendan pomelo peel, especially in terms of comparing the chemical composition and biological activities of Wendan pomelo peel from different cultivation regions.  
Therefore, the present work investigated the composition and antioxidant activity of Wendan pomelo peel grown in China from four different origins.