{"title":"<sup>11</sup>C-labeling of 20(S)-protopanaxadiol, an aglycon of ginsenoside, based on the use of Pd(0)-mediated rapid C-[<sup>11</sup>C]methylation of boronic precursors.","authors":"Yoshiki Ooshima, Hiroko Koyama, Aya Ogata, Hiroshi Ikenuma, Takashi Yamada, Hiroyuki Kojima, Takashi Kato, Yasuyuki Kimura, Masaaki Suzuki","doi":"10.1016/j.bmcl.2025.130356","DOIUrl":null,"url":null,"abstract":"<p><p>Ginsenosides, the pharmacologically active components of Panax ginseng, are widely used in herbal medicine and reportedly exert diverse biological effects, including anticancer, anti-inflammatory, and neuroprotective activities. However, their pharmacological mechanisms remain poorly understood, owing to the lack of chemical probes suitable for in vivo analyses. Herein, we report the development of a <sup>11</sup>C radiolabeling of 20(S)-protopanaxadiol (PPD), a major aglycone-type active ginsenoside metabolite, for positron emission tomography (PET) imaging. For the <sup>11</sup>C labeling of PPD, we focused on the terminal vinyl methyl group of the dammarane-type triterpene backbone, a common structural element found in ginsenosides. A boronic precursor applicable for rapid <sup>11</sup>C-methylation was efficiently synthesized via steps focusing on the controlled cross-metathesis of an internal olefin. The subsequent Pd(0)-mediated rapid <sup>11</sup>C-methylation was conducted in N,N-dimethylformamide (DMF)/H₂O using [Pd₂(dba)₃], P(o-tolyl)₃, and sodium ascorbate, which functioned as a base and a radical scavenger. After formulation, the resulting [<sup>11</sup>C]PPD was obtained in a decay-corrected radiochemical yield of 15 ± 2 % (n = 3), with a total radioactivity of 1.0 ± 0.3 GBq (n = 3) and molar activity of 124 ± 7 GBq/μmol (n = 3). Radiochemical purity was ≥99 %, and the total synthesis time was 29 min. Using [<sup>11</sup>C]PPD, PET imaging of the brains of healthy rats and abdomens of healthy mice demonstrated low brain uptake and pronouncedly clear hepatobiliary excretion of radiolabeled species. These findings may provide a foundation for the general labeling of ginsenoside structures with <sup>11</sup>C radioisotopes, thereby enabling systematic in vivo pharmacokinetic analyses of PPD derivatives to advance ginsenoside-based drug development.</p>","PeriodicalId":256,"journal":{"name":"Bioorganic & Medicinal Chemistry Letters","volume":" ","pages":"130356"},"PeriodicalIF":2.2000,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Bioorganic & Medicinal Chemistry Letters","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1016/j.bmcl.2025.130356","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/8/5 0:00:00","PubModel":"Epub","JCR":"Q3","JCRName":"CHEMISTRY, MEDICINAL","Score":null,"Total":0}
引用次数: 0
Abstract
Ginsenosides, the pharmacologically active components of Panax ginseng, are widely used in herbal medicine and reportedly exert diverse biological effects, including anticancer, anti-inflammatory, and neuroprotective activities. However, their pharmacological mechanisms remain poorly understood, owing to the lack of chemical probes suitable for in vivo analyses. Herein, we report the development of a 11C radiolabeling of 20(S)-protopanaxadiol (PPD), a major aglycone-type active ginsenoside metabolite, for positron emission tomography (PET) imaging. For the 11C labeling of PPD, we focused on the terminal vinyl methyl group of the dammarane-type triterpene backbone, a common structural element found in ginsenosides. A boronic precursor applicable for rapid 11C-methylation was efficiently synthesized via steps focusing on the controlled cross-metathesis of an internal olefin. The subsequent Pd(0)-mediated rapid 11C-methylation was conducted in N,N-dimethylformamide (DMF)/H₂O using [Pd₂(dba)₃], P(o-tolyl)₃, and sodium ascorbate, which functioned as a base and a radical scavenger. After formulation, the resulting [11C]PPD was obtained in a decay-corrected radiochemical yield of 15 ± 2 % (n = 3), with a total radioactivity of 1.0 ± 0.3 GBq (n = 3) and molar activity of 124 ± 7 GBq/μmol (n = 3). Radiochemical purity was ≥99 %, and the total synthesis time was 29 min. Using [11C]PPD, PET imaging of the brains of healthy rats and abdomens of healthy mice demonstrated low brain uptake and pronouncedly clear hepatobiliary excretion of radiolabeled species. These findings may provide a foundation for the general labeling of ginsenoside structures with 11C radioisotopes, thereby enabling systematic in vivo pharmacokinetic analyses of PPD derivatives to advance ginsenoside-based drug development.
期刊介绍:
Bioorganic & Medicinal Chemistry Letters presents preliminary experimental or theoretical research results of outstanding significance and timeliness on all aspects of science at the interface of chemistry and biology and on major advances in drug design and development. The journal publishes articles in the form of communications reporting experimental or theoretical results of special interest, and strives to provide maximum dissemination to a large, international audience.