title: Spatial accumulation pattern of citrulline and other nutrients in immature and mature watermelon fruits.
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.
  
  
  CONCLUSIONS
  These observations suggested that citrulline accumulation may be regulated in a distinct manner from other nutrients during watermelon fruit maturation. © 2016 Society of Chemical Industry.
authors.affiliation: School of Agricultural, Biological and Environmental Sciences, Faculty of Agriculture, Tottori University, 4-101 Koyama Minami, Tottori 680-8553, Japan.
authors.forename: Kinya
authors.initials: K
authors.lastname: Akashi
authors.affiliation: School of Agricultural, Biological and Environmental Sciences, Faculty of Agriculture, Tottori University, 4-101 Koyama Minami, Tottori 680-8553, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Mifune
authors.affiliation: Tottori Prefectural Horticultural Research Center, 2048 Yurashuku, Hokuei, Tottori 689-2221, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Morita
authors.affiliation: Tottori Prefectural Horticultural Research Center, 2048 Yurashuku, Hokuei, Tottori 689-2221, Japan.
authors.forename: Souichi
authors.initials: S
authors.lastname: Ishitsuka
authors.affiliation: Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Tsujimoto
authors.affiliation: Tottori Prefectural Horticultural Research Center, 2048 Yurashuku, Hokuei, Tottori 689-2221, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ishihara
mesh_terms: D050260:Carbohydrate Metabolism; D002338:Carotenoids / Q000378:metabolism; D002956:Citrulline / Q000378:metabolism* / Q000494:pharmacology; D029773:Citrullus / Q000378:metabolism*; D005638:Fruit / Q000378:metabolism*; D006801:Humans; D000077276:Lycopene; D009569:Nitric Oxide / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D025341:Principal Component Analysis
chemical_list: D010940:Plant Proteins; D002956:Citrulline; D009569:Nitric Oxide; D002338:Carotenoids; D000077276:Lycopene
keywords: arid region; citrulline; fruit maturation; lycopene; soluble sugar; watermelon