Identification of a new metabolite of astilbin, 3'-O-methylastilbin, and its immunosuppressive activity against contact dermatitis.
BACKGROUND
Astilbin is a flavonoid isolated from the rhizome of Smilax glabra. In a previous study, we revealed its unique immunosuppressive activity, a selective inhibition against activated T lymphocytes. This characteristic of astilbin is beneficial for the treatment of human immune diseases.


METHODS
We incubated astilbin with rat liver microsomal/cytosolic fractions and isolated the metabolite of astilbin, which was fully characterized by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. We administered astilbin orally via a gastric tube to rats at 0.22 mmol/kg and collected whole blood samples after 30 min and urine samples after 0 to 12 h. We applied HPLC and liquid chromatography/MS to measure the metabolite in the samples, and we assayed cytokine expression by reverse-transcription PCR.


RESULTS
After incubation of astilbin with rat liver microsomal/cytosolic fractions, we detected a new metabolite of astilbin and isolated it from the culture solution. We characterized this metabolite by MS and NMR techniques as 3'-O-methylated astilbin. We detected the metabolite in both blood and urine samples after oral administration of astilbin, and the metabolite inhibited picryl chloride-induced ear swelling in mice and suppressed the expression of tumor necrosis factor-alpha and interferon-gamma, similarly to astilbin.


CONCLUSIONS
This is the first identification of 3'-O-methylastilbin as a new flavonoid, as well as an active metabolite of astilbin in vivo, and is helpful for studying the kinetics of astilbin and its clinical applications.
Guo
Jianming
J
State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Key Laboratory of Analytical Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China.
Qian
Feng
F
Li
Jianxin
J
Xu
Qiang
Q
Chen
Ting
T
D000818:Animals; D017449:Dermatitis, Allergic Contact / Q000188:drug therapy*; D004487:Edema / Q000139:chemically induced / Q000276:immunology; D005260:Female; D044948:Flavonols / Q000378:metabolism* / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D007166:Immunosuppressive Agents / Q000378:metabolism* / Q000494:pharmacology* / Q000627:therapeutic use; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008862:Microsomes, Liver / Q000378:metabolism; D010853:Picryl Chloride; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
C518533:3'-O-methylastilbin; D044948:Flavonols; D007166:Immunosuppressive Agents; D014409:Tumor Necrosis Factor-alpha; C099069:astilbin; D007371:Interferon-gamma; D010853:Picryl Chloride