{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,10]],"date-time":"2026-09-10T05:09:38Z","timestamp":1789016978285,"version":"build-2803163510"},"reference-count":25,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T00:00:00Z","timestamp":1788825600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Doctoral Start-up Fund of Qufu Normal University","award":["613401"],"award-info":[{"award-number":["613401"]}]},{"award":["613401"],"award-info":[{"award-number":["613401"]}],"id":[{"id":"https:\/\/ror.org\/03ceheh96","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100007129","name":"Natural Science Foundation of Shandong province","doi-asserted-by":"crossref","award":["ZR2023MC190"],"award-info":[{"award-number":["ZR2023MC190"]}],"id":[{"id":"10.13039\/501100007129","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Metabolites"],"abstract":"<jats:p>Background: Flavonoid secondary metabolites accumulate in xylem during heartwood formation and critically influence wood color and economic value. However, the distribution patterns of individual flavonoids across sapwood, transition zone, and heartwood remain poorly characterized in Castanopsis hystrix, limiting mechanistic understanding of heartwood formation and rational resource utilization. Methods: Sapwood, transition zone, and heartwood samples were collected and analyzed using ultra-performance liquid chromatography coupled with Q-Exactive Orbitrap mass spectrometry (UPLC-QE-MS) for qualitative and quantitative flavonoid determination. Multivariate statistical approaches, including hierarchical clustering, principal component analysis (PCA), and orthogonal partial least-squares discriminant analysis (OPLS-DA), were applied to compare regional metabolic profiles and to identify characteristic differential markers. Results: A total of 26 flavonoids were identified, covering flavones, flavonols, flavanones, dihydroflavonols, and flavanols. Quantitative and cluster analyses revealed distinct region-preferential accumulation: dihydrorobinetin, dihydromyricetin, morin, and kaempferol were highly enriched in heartwood; fustin, taxifolin, and cyanidin predominated in the transition zone, whereas afzelin and astilbin were more abundant in sapwood. PCA and OPLS-DA further selected four characteristic markers, namely dihydromyricetin, dihydrorobinetin, kaempferol and (\u2212)-epicatechin, that effectively discriminated the three regions. Conclusions: This study establishes a clear radial gradient of flavonoid accumulation in C. hystrix xylem, demonstrating selective enrichment of specific metabolites from sapwood to heartwood. These findings provide essential data for deciphering the biochemical mechanisms of heartwood formation and offer a metabolic basis for quality assessment and high-value utilization of this timber species.<\/jats:p>","DOI":"10.3390\/metabo16090655","type":"journal-article","created":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T09:02:24Z","timestamp":1788858144000},"page":"655","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Identification of Flavonoids in the Xylem of Castanopsis hystrix and Their Content Variation Patterns During Heartwood Formation"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8632-0571","authenticated-orcid":false,"given":"Ruoke","family":"Ma","sequence":"first","affiliation":[{"name":"School of Life Sciences, Qufu Normal University, Qufu 273165, China"},{"name":"Shandong Key Laboratory of Wetland Ecology and Biodiversity Conservation in the Lower Yellow River, Qufu 273165, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"given":"Liuming","family":"Wei","sequence":"additional","affiliation":[{"name":"Guangxi Zhuang Autonomous Region Forestry Research Institute, Nanning 530002, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Pingchuan","family":"Zhu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning 530004, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"}]},{"given":"Heng","family":"Liu","sequence":"additional","affiliation":[{"name":"Experimental Center of Tropical Forestry, Chinese Academy of Forestry, Pingxiang 532600, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"}]},{"given":"Boling","family":"Liu","sequence":"additional","affiliation":[{"name":"School of Life Sciences, Qufu Normal University, Qufu 273165, China"},{"name":"Shandong Key Laboratory of Wetland Ecology and Biodiversity Conservation in the Lower Yellow River, Qufu 273165, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"given":"Jianhua","family":"Qi","sequence":"additional","affiliation":[{"name":"Heze  Forestry Technical Service Center, Heze 274000, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,8]]},"reference":[{"key":"ref_1","unstructured":"Liu, X., Li, C., Chen, S., Wei, L., Chen, G., and Tang, J. 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