Understanding the infrared and Raman spectra of ganoderic acid A: An experimental and DFT study Guohua Yao a , Yuhan Ma a,b,c , Muhammad Muhammad a,b , Qing Huang a,b,c, ⁎ a Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China b University of Science & Technology of China, Hefei 230026, China c College of Life Science, Anhui Science and Technology University, Fengyang 233100, China abstract article info Article history: Received 11 August 2018 Received in revised form 18 October 2018 Accepted 12 November 2018 Available online 13 November 2018 Ganoderic Acids (GAs) are the major medicinal compounds in Ganoderma lucidum used as traditional Chinese medicine since ancient times. Ganoderic acid A (GAA) is the first discovered ganoderic acids reported in the lit- erature, which is also one of most abundant triterpenoids of Ganoderma lucidum. Especially, GAA has been exten- sively investigated in recent decades for its positive medicinal activities. However, the vibrational properties of GAs have rarely been studied or reported. In this work, we focused on the typical GAA and studied the infrared (IR) and Raman spectra based on both experiments and DFT calculations. As such, we could not only achieve the assignments of the vibrational modes, but also from the IR and Raman spectra, we found that the spectral re- gion from 1500 cm -1 to 1800 cm -1 is particularly useful for distinguishing different types of GAs. In addition, its dehydrogenated derivative ganoderenic acid A (GOA) was also studied, which could be identified due to its spec- tral feature of strong IR and Raman bands around 1620 cm -1 . This work therefore may facilitate the application of IR and Raman spectroscopies in the inspection and quality control of Ganoderma lucidum. © 2018 Elsevier B.V. All rights reserved. Keywords: Ganoderic acids (GAs) Ganoderic acid A (GAA) Infrared spectroscopy Raman spectroscopy Ganoderenic acid a (GOA) DFT-M06-2X-D3 1. Introduction Ganoderma lucidum (G. lucidum), namely, Lingzhi in Chinese and Reishi in Japanese, has been widely used as a well-known traditional medicinal mushroom for several thousand years in Asia due to its positive medicinal effects including improving immunity and promoting health [1,2]. G. lucidum contains terpenoids, polysaccharides, proteins and small amounts of amino acids and vitamins as well. The pharmacological and clinical application of the aqueous/ethanol extracts of G. lucidum is pre- vention/treatment of various types of human diseases, such as allergy, bronchitis, hyperglycemia, inflammation, nephritis, hepatopathy, arthri- tis, hypertension, neurasthenia and chronic hepatitis [3]. Ganoderic acids (GAs), which are highly oxygenated C30 lanostane‑type triterpenoids, are responsible for the pharmacological activities of G. lingzhi [4,5]. Amongst terpenes and triterpenes, GAs are considered as one of major medicinal compounds in G. lucidum. Since 1982, a lot of studies found that GAs have antitumor activity, such as inhibiting proliferation of human cervical carcinoma, exhibiting cyto- toxicity against hepatoma, suppressing growth and invasive behavior of breast cancer cells, inhibiting tumor growth and lung metastasis, inhibiting proliferation of prostate cancer and osteoclast differentiation [5–7]. Since the first isolation of GAA and GAB from G. lucidum by Kubota and Asaka [8], a series of GAs (like Ganoderma acid C, D, E, F… X, Y, Z, Df, DM, Me, Mk, et al.) have been isolated from the fruiting bodies, spores, and mycelia of G. lucidum and similar species, and there are more than one hundred isoforms of ganoderic acids which have been isolated and characterized [9–16]. While the basic lanosterol scaffold in the GAs remains the same, the side chains or functional units of different GAs vary and determine the function of particular ganoderic acid [17]. Ganoderic acid A (GAA) is the first discovered GA which is also one of the most abundant triterpenoids in G. Lingzhi, and it is generally con- centrated in the Ganoderma genus. GAA exhibits hypolipidemic, antinociceptive, anti-inflammatory, antioxidative, hepatoprotective and anticancer activities [18–20]. Recently, GAA has gained special at- tention due to its apparent antitumour activities on human osteosar- coma, lymphoma, meningioma and breast cancer cells. It may become a promising candidate for new drug development [18]. Normally, GAs are separated through extraction and chromatogra- phy from Ganoderma lucidum, and then the molecular structures of the GA types can be determined by the techniques such as mass spec- troscopy, NMR and X-ray diffraction [15,18,21]. The disadvantages of the methods of MS, NMR and X-ray diffraction are their instrumental expense and time-consuming operation. Nowadays, infrared (IR) Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 210 (2019) 372–380 ⁎ Corresponding author at: Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China. E-mail address: huangq@ipp.ac.cn (Q. Huang). https://doi.org/10.1016/j.saa.2018.11.019 1386-1425/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa