AUTHOR=Wang Yan-Duo , Yang Jian , Li Qi , Li Yuan-Yuan , Tan Xiang-Mei , Yao Si-Yang , Niu Shu-Bin , Deng Hui , Guo Lan-Ping , Ding Gang 

TITLE=UPLC-Q-TOF-MS/MS Analysis of Seco-Sativene Sesquiterpenoids to Detect New and Bioactive Analogues From Plant Pathogen Bipolaris sorokiniana

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.807014

DOI=10.3389/fmicb.2022.807014

ISSN=1664-302X

ABSTRACT=<p><italic>Seco</italic>-sativene sesquiterpenoids are an important member of phytotoxins and plant growth regulators isolated from a narrow spectrum of fungi. In this report, eight <italic>seco</italic>-sativene sesquiterpenoids (<bold>1</bold>–<bold>8</bold>) were first analyzed using the UPLC-Q-TOF-MS/MS technique in positive mode, from which their mass fragmentation pathways were suggested. McLafferty rearrangement, 1,3-rearrangement, and neutral losses were considered to be the main fragmentation patterns for the [M+1]<sup>+</sup> ions of <bold>1</bold>–<bold>8</bold>. According to the structural features (of different substitutes at C-1, C-2, and C-13) in compounds <bold>1</bold>–<bold>8</bold>, five subtypes (A–E) of <italic>seco</italic>-sativene were suggested, from which subtypes A, B/D, and E possessed the diagnostic daughter ions at <italic>m</italic>/<italic>z</italic> 175, 189, and 203, respectively, whereas subtype C had the characteristic daughter ion at <italic>m</italic>/<italic>z</italic> 187 in the UPLC-Q-TOF-MS/MS profiles. Based on the fragmentation patterns of <bold>1</bold>–<bold>8</bold>, several known compounds (<bold>1</bold>–<bold>8</bold>) and two new analogues (<bold>9</bold> and <bold>10</bold>) were detected in the extract of plant pathogen fungus <italic>Bipolaris sorokiniana</italic> based on UPLC-Q-TOF-MS/MS analysis, of which <bold>1</bold>, <bold>2</bold>, <bold>9</bold>, and <bold>10</bold> were then isolated and elucidated by NMR spectra. The UPLC-Q-TOF-MS/MS spectra of these two new compounds (<bold>9</bold> and <bold>10</bold>) were consistent with the fragmentation mechanisms of <bold>1</bold>–<bold>8</bold>. Compound <bold>1</bold> displayed moderate antioxidant activities with IC<sub>50</sub> of 0.90 and 1.97 mM for DPPH and ABTS<sup>+</sup> scavenging capacity, respectively. The results demonstrated that <italic>seco</italic>-sativene sesquiterpenoids with the same subtypes possessed the same diagnostic daughter ions in the UPLC-Q-TOF-MS/MS profiles, which could contribute to structural characterization of <italic>seco</italic>-sativene sesquiterpenoids. Our results also further supported that UPLC-Q-TOF-MS/MS is a powerful and sensitive tool for dereplication and detection of new analogues from crude extracts of different biological origins.</p>