Kinya Akashi1, Yuki Mifune1, Kaori Morita2, Souichi Ishitsuka2, Hisashi Tsujimoto3, Toshiyuki Ishihara2. 1. School of Agricultural, Biological and Environmental Sciences, Faculty of Agriculture, Tottori University, 4-101 Koyama Minami, Tottori 680-8553, Japan. 2. Tottori Prefectural Horticultural Research Center, 2048 Yurashuku, Hokuei, Tottori 689-2221, Japan. 3. Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan.
Abstract
BACKGROUND: Watermelon (Citrullus lanatus L.) originates from arid regions of southern Africa, and its fruit contains a large amount of the amino acid citrulline, an efficient hydroxyl radical scavenger. Citrulline is implicated in the production of nitric oxide in human endothelium, and potential health benefits including vasodilatation and antioxidant functions have been suggested. However, citrulline metabolism in watermelon fruits is poorly understood. RESULTS: This study examined the accumulation pattern of citrulline and other nutrients in immature and mature watermelon fruits. In mature fruits, highest citrulline concentration was observed in the outer peel, followed by the central portion of the flesh and inner rinds, whereas the level was lower in the peripheral portion of the flesh. Citrulline content was generally low in immature fruits. Spatial and developmental patterns of citrulline accumulation were largely different from those of the antioxidant lycopene, total proteins, and soluble sugars such as glucose, fructose, and sucrose. Principal component analysis suggested a clear distinction of the central flesh and outer peels in mature fruits from other tissues in terms of the levels of major nutrients. CONCLUSION: These observations suggested that citrulline accumulation may be regulated in a distinct manner from other nutrients during watermelon fruit maturation.
BACKGROUND:Watermelon (Citrullus lanatus L.) originates from arid regions of southern Africa, and its fruit contains a large amount of the amino acid citrulline, an efficient hydroxyl radical scavenger. Citrulline is implicated in the production of nitric oxide in human endothelium, and potential health benefits including vasodilatation and antioxidant functions have been suggested. However, citrulline metabolism in watermelon fruits is poorly understood. RESULTS: This study examined the accumulation pattern of citrulline and other nutrients in immature and mature watermelon fruits. In mature fruits, highest citrulline concentration was observed in the outer peel, followed by the central portion of the flesh and inner rinds, whereas the level was lower in the peripheral portion of the flesh. Citrulline content was generally low in immature fruits. Spatial and developmental patterns of citrulline accumulation were largely different from those of the antioxidant lycopene, total proteins, and soluble sugars such as glucose, fructose, and sucrose. Principal component analysis suggested a clear distinction of the central flesh and outer peels in mature fruits from other tissues in terms of the levels of major nutrients. CONCLUSION: These observations suggested that citrulline accumulation may be regulated in a distinct manner from other nutrients during watermelon fruit maturation.
Authors: Muhammad Jawad Umer; Luqman Bin Safdar; Haileslassie Gebremeskel; Shengjie Zhao; Pingli Yuan; Hongju Zhu; M O Kaseb; Muhammad Anees; Xuqiang Lu; Nan He; Chengsheng Gong; Wenge Liu Journal: Hortic Res Date: 2020-12-01 Impact factor: 6.793