RAMAN MICRO-SPECTROSCOPY OF RED CAROTENOIDS FROM POTAMOGETON CRISPUS L.

Potamogeton crispus L. is a kind of nature aquatic plant and widely dispersed over the world with important value in ecology and economy, it was reported that there were many nutritious elements such as proteins,fats, amino acids, fibres, Ca, P, vitamins etc. in it, and the utilizable value of feedstuffs has been understood preliminarily. The appearance that ducks fed with Potamogeton crispus could produce natural red-yolk eggs with good quality and price had been known long ago in Xiantao and Honghu area, Hubei province, the P. R. China, we have preliminarily found a high contents of carotenoids (especially a kind of red pigments) in Potamogeton crispus,the egg yolks color values could increase greatly when ducks were fed with it, and the red and some yellow pigments of the red-yolk eggs were in correspondence with the pigments in Potamogeton crispus by thin-layer chromatography, IR, and LC-MS, etc. Many researches showed that carotenoids not only was a kind of important natural pigments, but also possessed important biological functions including antioxidant activity, enhancing the immune system and the cell gap junctional communication, inducing cellular apoptosis, and regulating gene expression, so it is hot-point to find the biological resources abundant in carotenoids, we must make systematic studies on carotenoids of Potamogeton crispus so as to exploit this natural resources well. Three red pigments r1, r2 and r3 were extracted and separated by means of MgO-Diatomaceous Earth(1∶2,W/W) column and silica-gel G TLC from Potamogeton crispus L., the good separating solvent mixtures on the silica G TLC were:hexane-ethyl acetate-acetone-methanol=27∶4∶2∶2 (v/v/v/v), the R f of r1, r2 and r3 on the TLC were 0.32, 0.34 and 0.38, respectively, the arrangement in accordance with the polarity were astaxanthin>r1>r2>r3>canthaxanthin>β-carotene. Raman spectroscopy can provide detailed information on molecular vibrations, among naturally occurring chromophores, carotenoids have proved to be very suitable for studies in Raman spectroscopy, vibrational spectra can be obtained at very low concentration (until 10 -8 M). The Raman spectra of r1, r2 and r3 were recorded by micro Raman and compared with as taxanthin and β-carotene. Raman measurements were performed directly on the dry sample with a RM-1000 Confocal Laser Raman Micro-spectroscopy (Made in Renishaw Co., England), Ar+ Laser (514.5nm), Objective (×50), Silt 50μm, Time 10s,Range from 150-4000 cm-1,Resolution at 2cm-1. The Raman spectra in the "finger print region" (-1) of r1, r2 and r3 have strong characteristic bands at 1527cm-1 assigned to υ c=c, the second characteristic bands were r1 at 1162cm-1, r2 and r3 at 1157cm-1 assigned to υ c-c, the third characteristic bands were r1, r2 and r3 at 1007cm-1 mainly assigned to rocking modes of methyl group bond. r1, r2 and r3 have very similar Raman spectra in the region of 2000-4000cm-1 as well. It were important evidence of r1, r2 and r3 as carotenoids based on these characteristic Raman spectra. Compared with astaxanthin and β-carotene, there were small difference in the Raman spectra of r1, r2 and r3, it suggested that r1, r2 and r3 might have different fine structure.