|Naumann, Harley - UNIVERSITY OF MISSOURI|
|Sepela, Rebecka - MIAMI UNIVERSITY - OHIO|
|Rezaire, Aira - MIAMI UNIVERSITY - OHIO|
|Hagerman, Ann - MIAMI UNIVERSITY - OHIO|
|Robe, Jamison - UNIVERSITY OF WISCONSIN|
Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/17/2018
Publication Date: 3/21/2018
Citation: Naumann, H.D., Sepela, R., Rezaire, A., Hagerman, A.E., Reinhardt, L.A., Robe, J., Zeller, W.E. 2018. Composition and structural features of condensed tannins from Texas legumes exhibiting methane abatement activity during in vitro rumen digestion. American Chemical Society Abstracts. AGFD 203.
Technical Abstract: Previous studies showed that a series of purified condensed tannins (CTs) from warm-season perennial legumes exhibited high variability in their modulation of methane production during in vitro rumen digestion. The molecular weight difference of these CTs did not provide correlation with either the in vitro CH4 production or the ability to precipitate bovine serum albumin. In an effort to delineate other structure-activity relationships from these methane abatement experiments, the structures of purified CTs from legumes representing Papilionoideae (Desmodium paniculatum, Lespedeza stuevei, and Lespedeza cuneata [var. hitru and Missouri naturalized]) and Mimosoideae (Mimosa strigillosa, Leucaena retusa, Neptunia lutea, Desmanthus illinoensis, and Acacia angustissima) were assessed through a combination of methanolysis, quantitative thiolysis, ESI-MS, MALDI-TOF MS, and high-resolution 1H-13C HSQC NMR spectroscopy. The structural composition of these CTs was as follows: D. paniculatum: proanthocyanidin to proanthodelphinidin (PC/PD) ratio 55/45, cis/trans ratio 87/13, mDP ~20; L. stuevei: PC/PD ratio 42/58, cis/trans ratio 31/69 (NMR), 64/36 (thiolysis), mean degree of polymerization mDP (~10), and a trace of galloylated subunits; L. cuneata: PC/PD ratio 5/95, cis/trans ratio 75/25 (NMR), 93/7 (thiolysis), mDP ~14, and a trace of galloylated subunits; M. strigillosa: PC/PD ratio 15/85, cis/trans ratio 89/11, mDP ~10, and 43% of the flavan-3-ol subunits galloylated; L. retusa: PC/PD ratio 99/1, cis/trans ratio 98/2, mDP ~6, and ~25% of the flavan-3-ol subunits galloylated; N. lutea: PC/PD ratio 12/88, cis/trans ratio 94/6, mDP ~12, and 32% of the flavan-3-ol subunits galloylated; and D. illinoensis: PC/PD ratio 4/96, cis/trans ratio 99/1, mDP ~6, and 75% of the flavan-3-ol subunits galloylated. The CT isolated from A. angustissima presented an unusual challenge as it was resistant to standard thiolytic degradation conditions and exhibited an atypical set of cross-peak signals in the 2D-NMR. Efforts to elucidate the structure of this CT will be discussed.