PSV-25 Comparative analysis of condensed tannins in Lespedeza cuneata: Structural composition and relative abundance.

Abstract Condensed tannins (CTs) are polyphenolic compounds that contribute to plant defense mechanisms, nutritional properties, and medicinal applications. Lespedeza cuneata, a leguminous plant, contains diverse CTs with varying structural compositions. This study analyzed the structural composition and relative abundance of CTs extracted from two different plots (Plot 29 and Plot 105) using liquid chromatography-mass spectrometry (LC-MS). The samples were extracted using aqueous acetone (70% acetone, 30% water), purified to remove pigments and impurities, and analyzed using a Thermo Q Exactive mass spectrometer coupled with a Vanquish LC system. LC-MS analysis revealed sixteen distinct tannins in Plot 29 and eight in Plot 105. The most abundant tannins in Plot 29 included ions at m/z 565 (25.6%), m/z 595 (15.3%), and m/z 449 (12.4%), whereas Plot 105 exhibited a dominant peak at m/z 535 (38.4%), which was absent in Plot 29. Moderate similarities were observed for m/z 344 and 207 across both samples, but overall, qualitative and quantitative differences indicated variability in tannin biosynthesis. The observed compositional differences suggest potential influences of environmental factors or genetic variation. Structural predictions for several tannins were made using MS1 and MS2 fragmentation data, though some masses remained unidentified due to a lack of reference data in existing literature. The study underscores the complexity of CT profiles in L. cuneata and highlights the necessity for further validation through nuclear magnetic resonance (NMR) spectroscopy. These findings contribute to the broader understanding of condensed tannin diversity, offering insights into their ecological functions and potential applications in agriculture, medicine, and food science. Future research should focus on confirming the predicted structures, assessing bioactivity, and exploring the environmental factors influencing tannin biosynthesis.