JOURNAL OF RAMAN SPECTROSCOPY J. Raman Spectrosc. 2008; 39: 1464–1468 Published online 2 June 2008 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jrs.2023 Raman analysis of synthetic eritadenine Josefine Enman, 1 Kerstin Ramser, 2* Ulrika Rova 1 and Kris Arvid Berglund 1 1 Department of Chemical Engineering and Geosciences, Lule ˚ a University of Technology, SE-971 87 Lule ˚ a, Sweden 2 Department of Computer Science and Electrical Engineering, Lule ˚ a University of Technology, SE-971 87 Lule ˚ a, Sweden Received 10 March 2008; Accepted 24 April 2008 Eritadenine, 2(R),3(R)-dihydroxy-4-(9-adenyl)-butyric acid, is a cholesterol-reducing compound naturally occurring in the shitake mushroom (Lentinus edodes). To identify the unknown Raman spectrum of this compound, pure synthetic eritadenine was examined and the vibrational modes were assigned by following the synthesis pathway. This was accomplished by comparing the known spectra of the starting compounds adenine and D-ribose with the spectra of a synthesis intermediate, methyl 5-(6-Aminopurin-9H- 9-yl)-2,3-O-isopropylidene-5-deoxy-b-D-ribofuranoside (MAIR) and eritadenine. In the Raman spectrum of eritadenine, a distinctive vibrational mode at 773 cm -1 was detected and ascribed to vibrations in the carbon chain, n(C–C). A Raman line that arose at 1212 cm -1 , both in the Raman spectrum of MAIR and eritadenine, was also assigned to n(C–C). Additional Raman lines detected at 1526 and at 1583 cm -1 in the Raman spectrum of MAIR and eritadenine were assigned to n(N–C) and a deformation of the purine ring structure. In these cases the vibrational modes are due to the linkage between adenine and the ribofuranoside moiety for MAIR, and between adenine and the carbon chain for eritadenine. This link is also the cause for the disappearance of adenine specific Raman lines in the spectrum of both MAIR and eritadenine. Several vibrations observed in the spectrum of D-ribose were not observed in the Raman spectrum of eritadenine due to the absence of the ribose ring structure. In the Raman spectrum of MAIR some of the D-ribose specific Raman lines disappeared due to the introduction of methyl and isopropylidene moieties to the ribose unit. With the approach presented in this study the so far unknown Raman spectrum of eritadenine could be successfully identified and is presented here for the first time. Copyright  2008 John Wiley & Sons, Ltd. KEYWORDS: eritadenine; Raman spectroscopy; Raman line assignment; bioactive compound INTRODUCTION Hypercholesterolemia is an accepted risk factor for the development of cardiovascular disease which is one of the most serious health concerns in modern Western society. Frequently prescribed drugs against hypercholesterolemia are the statins which were originally isolated from fungi such as Aspergillus terreus. 1 Although the statins are efficient cholesterol-reducing agents, their side effects are a matter of debate. 2 Another fungal-derived cholesterol-reducing compound is eritadenine, 2(R),3(R)-dihydroxy-4-(9-adenyl)- butyric acid (Fig. 1(D)), 3,4 naturally occurring in the shitake mushroom, Lentinus edodes. The shiitake mushroom has been shown to lower blood cholesterol in both animals and humans 5,6 and the mechanism of action of eritadenine has been investigated in several studies on rats. 3,4,7–10 Unlike the statins, there are no indications of eritadenine inhibiting L Correspondence to: Kerstin Ramser, Department of Computer Science and Electrical Engineering, Lule˚ a University of Technology, SE-971 87 Lule˚ a, Sweden. E-mail: kerstin.ramser@ltu.se the biosynthesis of cholesterol. Rather, eritadenine has been suggested to accelerate the removal of blood cholesterol either by stimulated tissue uptake or by inhibited tissue release. 10 Since eritadenine exerts another mechanism for its hypocholesterolemic effect than the statins, it could potentially be used in combination with the statins to diminish the side effects of the latter such as liver damage, rhabdomyolysis, and myotoxicity. 2 In the process of developing pharmaceuticals, the solid state of the compound is of great importance since it will affect the properties and performance of a drug, such as stability and bioavailability. One convenient way of determining the solid-state structures of organic compounds is by Raman analysis. 11 – 13 Raman spectroscopy is a laser- light based spectroscopic technique that can be coupled to a microscope. Micro-Raman configurations have proven to be most valuable for the examination of structural properties as well as states of molecules. In the present investigation a Raman spectrum of the cholesterol-reducing compound eritadenine, was collected Copyright  2008 John Wiley & Sons, Ltd.