Identification of molecular species of acylglycerols of Philippine wild edible mushroom, Ganoderma lucidum

Authors: Hou, Ching; Lin, Jiann; DULAY, RICH MILTON - Central Luzon State University; Ray, Karen

Submitted to: Biocatalysis and Agricultural Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2016
Publication Date: 2/15/2017
Citation: Hou, C.T., Lin, J.T., Dulay, R.R., Ray, K.J. 2017. Identification of molecular species of acylglycerols of Philippine wild edible mushroom, Ganoderma lucidum. Biocatalysis and Agricultural Biotechnology. 9:19-27.

Interpretive Summary: Wild edible mushrooms are widely consumed in many countries. Recently, we successfully cultivated four edible medicinal Philippine mushrooms in liquid culture. We found that Ganoderma lucidum (G. lucidum) contains 1.67% of total lipids and identified the lipid species of the solvent extract from liquid-cultured mycelium of G. lucidum. One hundred-three molecular species of acylglycerols containing all normal fatty acids were identified. The chain lengths of the constituent fatty acids were from 14 to 26 carbon atoms and the numbers of double bonds were from zero to three. Forty-one molecular species of acylglycerols out of 103 contained fatty acids with odd numbered carbon atoms. The fatty acids with odd numbered carbon atoms were 15:0, 17:0, 17:1, 19:0, 19:1, 21:0, 23:0, and 25:0. The total content of fatty acids with odd numbered carbon atoms was about 6.6% of all of the fatty acids of the triacylglycerols containing three normal fatty acids. The contents of individual fatty acids with odd numbered carbon atoms were as: 15:0 (2.76%), 17:0 (2.13%), 17:1 (1.35%), 19:0 (0.20%), and 19:1 (0.17%). This is the first report on C15 – C25 odd carbon-numbered fatty acids in mushrooms. The contents of fatty acids with odd numbered carbon atoms in mushrooms were high compared to those in other plants. This is the first report on the molecular species of acylglycerols in mushrooms. This study will advance not only the knowledge of mushroom lipid contents of these Philippine mushrooms, but also will serve for comparison to those lipids from mushrooms produced in the U.S. Studies of oils and lipids contents of agricultural materials (mushrooms) are of mutual interest to both countries.

Technical Abstract: Wild edible mushrooms are widely consumed in many countries. Recently, we successfully cultivated four edible medicinal Philippine mushrooms in liquid cultures. One of these is Ganoderma lucidum. With the aim to elucidate the functional bioactive lipids, we identified the lipid species of the solvent extract from liquid-cultured mycelium of G. lucidum. The mycelia biomass was freeze-dried and extracted with ethyl acetate. The solvent extract analyzed by TLC and HPLC showed the presence of the different lipid species. An internal standard, tricaprylin was used for HPLC to quantify lipid species in three groups. The solvent extract (0.371g) obtained from 22.15 g of dry mushroom mycelium consists of: retention time 4 – 8 min (polar lipids group) 238.28mg; 11 – 16 min (DAGs group) 45.78mg; and 26 – 32 min (TAGs group) 87.58mg. The molecular species of acylglycerols containing all normal fatty acids were identified by the MS2 of the lithium adducts of the molecular species of acylglycerols in the HPLC fractions of mushroom lipid extract using electrospray ionization mass spectroscopy. The molecular species were quantified by HPLC with ELSD and the MS ion signal intensities of the molecular ions. One hundred and three molecular species of acylglycerols containing all normal fatty acids (straight chain fatty acid without any functional group) were identified by the MS fragmentation involved their constituent fatty acids. The chain lengths of the constituent fatty acids were from 14 to 26 carbon atoms and the numbers of double bonds were from zero to three. The contents of the molecular species of triacylglycerols in the mushroom lipid extract in decreasing order were: OOP (2.45%), OOO (1.94%), LLP (1.92%), OLP (1.80%), LLO (1.57 %), OPP (1.30%), OOL (1.09%), OOS (0.88%), and LLL (0.85%). Forty one molecular species of acylglycerols out of 103 contained fatty acids with odd numbered carbon atoms. The fatty acids with odd numbered carbon atoms were 15:0, 17:0, 17:1, 19:0, 19:1, 21:0, 23:0, and 25:0. The total content of fatty acids with odd numbered carbon atoms was about 6.6% of all of the fatty acids of the triacylglycerols containing three normal fatty acids, and contents of individual fatty acids with odd numbered carbon atoms were as: 15:0 (2.76%), 17:0 (2.13%), 17:1 (1.35%), 19:0 (0.20%), and 19:1 (0.17%). It is interesting to see so many odd carbon-numbered fatty acids (C15 – C25) in this mushroom. The contents of fatty acids with odd numbered carbon atoms in mushroom were high compared to those in higher plants. This is the first report on the molecular species of acylglycerols in mushroom.