| Soil salinization and soil secondary salinization are increasingly serious around the world. In China, both the area of the saline soil and the extent of secondary soil salinization due to unsuitable irrigation are very serious, especially in the coastal area. According to salinity tolerance, plants are divided into halophytes and nonhalophytes. Halophytes can survive and reproduce in saline environment where the salt concentration is around 200 mM NaCl or more, so, there must be a certain strategy in the salt tolerance of halophytes. Suaeda salsa is a typical salt-dilution halophyte that is distributed widely in the Yellow River Delta. In the natural habitat, S. salsa produces dimorphic seeds, and the dimorphic seeds show great differences in seed color, germination characteristic and salt tolerance. There are no differences in the embryo of the dimorphic seeds. The color of the dimorphic seeds of S. salsa is mainly determined by the seed coats. However, the pigment composition and their properties of the seed coats are largely unknown. In this paper, the pigment composition and their properties such as the pigment species, extraction, isolation and identification in the dimorphic seeds of S. salsa were investigated by UV spectrophotometry, HPLC, NMR and HPLC/MS techniques to reveal the relationship between pigments species and the seed dimorphism of S. salsa.The main results were as follows:1. There were carotenoids in the dimorphic seeds and seed coats of S. salsa. The optimum extraction conditions of carotenoids from the brown seeds were obtained: solid-liquid ratio of seed : extraction agent equaled to 1:50, the extraction solvent was petroleum ether and acetone(V/V = 1:1), ultrasonic time was 10 min, two times. Carotenoid contents in the brown seeds and brown seed coats were higher than those of the black seeds and black seed coats, respectively. HPLC analysis showed that carotenoids in S. salsa seed coats containing lutein rather than ?-carotene. The content of lutein in the brown seed coats was higher than that in the black seed coats.2. When the pigments in dimorphic seeds of S. salsa were extracted by water, carotenoids were removed by pre-extracting with methanol. The color of the water extraction from the brown seeds was brown, which was similar with the native color of the seeds. But the color of the water extraction from the black seeds was white and transparent. The water extraction from the seed coats of S. salsa had no betanin. However, there were different substances between the black and brown seed coats of S. salsa by HPLC analysis. In the water extraction from black seed coats, two peaks at 6.869 min and 9.960 min might be special substances. But the species and structures need to be further identified.3. Red pigments could be extracted from the dimorphic seeds of S. salsa by hydrochloric acid-methanol solution. The optimum extraction conditions of the red pigments from the black seeds were obtained: solid-liquid ratio of seed : extraction agent equaled to 1:100, pre-extracted by acetone, the extraction solvent was hydrochloric acid and methanol(V/V = 5:95), warm bath at 60? two times, 1.5 h each time. Red pigments only existed in the seed coats. The content of the red pigment in the brown seed coats was higher than that in the black seed coats. Red pigments from the seed coats of S. salsa dimorphic seeds had no betanin. But there were different substances between the black and brown seed coats of S. salsa when analyzed by HPLC analysis. Four compounds were isolated successfully from the hydrochloric acid-methanol extraction of the black seed coats. It was speculated that the structure of compound 4 contained benzene rings and azo, because it had a maximum absorption at 253 nm and 347 nm. HPLC/MS analysis indicated that the molecular weight of the compound 4 was 680. And the carbon skeleton of compound 4 was determined according to its 13C-NMR and 1H-NMR, while the exact structure needs to be further identified. |
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