Exploration of Wendan Pomelo (Citrus maxima (Burm.) Merr. cv. Wentan) Peel from Four Different Growing Regions by Liquid Chromatography-Mass Spectrometry and Bioactivity Analysis

Wendan (a type of pomelo), a popular fruit in China, is less known in other countries. Its peel is widely used in food and traditional medicine. Four different origins (Xuzhou, Taizhou, Zhangzhou, and Meizhou) of Wendan pomelo were selected, and crude extracts were obtained by the Soxhlet extraction method. The composition of Wendan peel was analyzed by high-performance liquid chromatography-mass spectrometry (HPLC-MS) in positive ion mode. The compounds were identified by searching the Metabolite Link (METLIN), the Spectral Database for Organic Compounds (SDBS), and by referring to literature reports. A total of 20 compounds were identified among the samples from the four origins, of which 8 compounds were common. The majority of the compounds belonged to the flavonoid and coumarin classes; Meranzin hydrate was identified for the first time in pomelo peel. In vitro antioxidant activity experiments showed that samples from Taizhou, Zhejiang, exhibited the highest antioxidant activity in the DPPH, ABTS, and FRAP assays, with values of 0.59 mg/mL, 97.06 mu mol TE/g, and 60.62 mu mol Fe2+/g, respectively. Samples from Zhangzhou, Fujian, showed antioxidant activity second only to the samples from Taizhou, Zhejiang. The sample from Zhangzhou, Fujian Province, showed excellent inhibitory activity in the alpha-glucosidase inhibition assay (IC50 = 7.99 mg/mL).