Chemotype classification and biomarker screening of male Eucommia ulmoides Oliv. flower core collections using UPLC-QTOF/MS-based non-targeted metabolomics

Panfeng Liu; Lu Wang; Qingxin Du; Hongyan Du

doi:10.7717/peerj.9786

Chemotype classification and biomarker screening of male Eucommia ulmoides Oliv. flower core collections using UPLC-QTOF/MS-based non-targeted metabolomics

PeerJ. 2020 Aug 21:8:e9786. doi: 10.7717/peerj.9786. eCollection 2020.

Authors

Panfeng Liu^{1

2

3}, Lu Wang^{1

2

3}, Qingxin Du^{1

2

3}, Hongyan Du^{1

2

3}

Affiliations

¹ Paulownia Research & Development Center of China, National Forestry and Grassland Administration, Zhengzhou, Henan, China.
² Key Laboratory of Non-timber Forest Germplasm Enhancement & Utilization of State Forestry and Grassland Administration, Zhengzhou, Henan, China.
³ Non-timber Forestry Research & Development Center, Chinese Academy of Forestry, Zhengzhou, Henan, China.

Abstract

Background: In the Chinese health care industry, male Eucommia ulmoides Oliv. flowers are newly approved as a raw material of functional food. Core collections have been constructed from conserved germplasm resources based on phenotypic traits and molecular markers. However, little is known about these collections' phytochemical properties. This study explored the chemical composition of male E. ulmoides flowers, in order to provide guidance in the quality control, sustainable cultivation, and directional breeding of this tree species.

Methods: We assessed the male flowers from 22 core collections using ultra-performance liquid chromatography and quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) non-targeted metabolomics, and analyzed them using multivariate statistical methods including principal component analysis (PCA), hierarchical cluster analysis (HCA), and orthogonal partial least squares discriminant analysis (OPLS-DA).

Results: We annotated a total of 451 and 325 metabolites in ESI+ and ESI- modes, respectively, by aligning the mass fragments of the secondary mass spectra with those in the database. Four chemotypes were well established using the ESI+ metabolomics data. Of the 29 screened biomarkers, 21, 6, 19, and 5 markers corresponded to chemotypes I, II, III, and IV, respectively. More than half of the markers belonged to flavonoid and amino acid derivative classes.

Conclusion: Non-targeted metabolomics is a suitable approach to the chemotype classification and biomarker screening of male E. ulmoides flower core collections. We first evaluated the metabolite profiles and compositional variations of male E. ulmoides flowers in representative core collections before establishing possible chemotypes and significant biomarkers denoting the variations. We used genetic variations to infer the metabolite compositional variations of male E. ulmoides flower core collections instead of using the geographical origins of the germplasm resources. The newly proposed biomarkers sufficiently classified the chemotypes to be applied for germplasm resource evaluation.

Keywords: Biomarker screening; Chemotype classification; Eucommia ulmoides Oliv.; Non-targeted metabolomics; OPLS-DA.

Grants and funding

This research was funded by the Fundamental Research Funds for Central Public-interest Scientific Institution (CAFYBB2018QA008). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.