Free and Bound Phenolic Profiles and Antioxidant Activities in Melon (Cucumis melo L.) Pulp: Comparative Study on Six Widely Consumed Varieties Planted in Hainan Province

Bound phenolic compounds in the melon pulp have seldom been investigated. This study revealed considerable differences in the total phenolic content (TPC) and antioxidant activity of the free and bound phenolic extracts in the pulps of six melon varieties from Hainan Province, China. Naixiangmi and Yugu demonstrated the highest free TPC, while Meilong showed the highest bound and total TPC and antioxidant activity. UHPLC-QQQ-MS identified and quantified 30 phenolic compounds. The melon cultivars markedly differed in the amount and content of their free and bound phenolic compounds. Xizhoumi No. 25 and Meilong afforded the most phenolic compounds. Hongguan emerged with the highest free phenolic compound content and total content of phenolic compounds; however, Meilong possessed the highest bound phenolic compound content. Hierarchical cluster analysis divided the melon varieties into four different taxa. The present study provides a scientific basis for developing the health-promoting effects of melon pulp.