Features of citrus terpenoid production as revealed by carotenoid, limonoid and aroma profiles of two pummelos (Citrus maxima) with different flesh color.
BACKGROUND
Terpenoids are major components of carotenoids, limonoids and aromas in citrus fruits, resulting in fruit coloration, bitterness and aroma. In this study the carotenoid, limonoid and volatile profiles of red-flesh Chuhong pummelo (CH) and pale green-flesh Feicui pummelo (FC) were investigated by HPLC and GC/MS.


RESULTS
Large differences were found in constituents of carotenoids and limonoids in juice sacs and flavedo and of aromas in flavedo of the two pummelos. For carotenoids in juice sacs, CH contained 57 times the amount in FC, mainly all-trans-lycopene and phytoene, whereas in flavedo it contained only 25% of that in FC, the latter showing a high proportion of β-carotene and other chloroplastic carotenoids. In comparison with FC, limonin and nomilin aglycone production was boosted in juice sacs of CH while being almost absent in flavedo. For volatiles in flavedo, the total amount was significantly higher in CH. PCA suggested that germacrene-type sesquiterpenoids, etc. were principal in distinguishing volatile profiles of the two pummelos.


CONCLUSIONS
The data showed a different tissue-biased pattern of carotenoid and limonoid aglycone synthesis in pummelos with different flesh color, and the possible independently regulated synthesis of those metabolites in different fruit tissues. Furthermore, decreased carotenoid and limonoid aglycone production accompanied by increased accumulation of volatile terpenoids in flavedo of red-flesh CH was identified, indicating that a total capacity or a balance of production of various terpenoids might exist in pummelo fruit tissues. It was also suggested that substrate concentration is not the key factor affecting product concentrations during the synthesis of monoterpene derivatives.
Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry, Huazhong Agricultural University, Wuhan, 430070, China.
Cuihua
C
Liu
Fuhua
F
Yan
Huijun
H
Gao
Min
M
He
Zhuang
Z
Wang
Yunjiang
Y
Cheng
Xiuxin
X
Deng
Juan
J
Xu
D001584:Benzoxepins / Q000032:analysis; D002338:Carotenoids / Q000032:analysis* / Q000096:biosynthesis*; D002851:Chromatography, High Pressure Liquid; D002957:Citrus / Q000737:chemistry* / Q000378:metabolism; D005638:Fruit / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D036701:Limonins / Q000032:analysis* / Q000096:biosynthesis*; D000077276:Lycopene; D010858:Pigmentation; D012903:Smell; D013045:Species Specificity; D013729:Terpenes / Q000032:analysis / Q000378:metabolism; D055549:Volatile Organic Compounds / Q000032:analysis*
D001584:Benzoxepins; D036701:Limonins; D013729:Terpenes; D055549:Volatile Organic Compounds; D002338:Carotenoids; C100185:(all-E) phytoene; C059405:nomilin; C001546:limonin; D000077276:Lycopene
Citrus maxima; carotenoids; limonoid aglycones; terpenoids; volatiles