抄録
Capsaicin is a pungent and orally ingested compound which is included especially in red pepper. Capsaicin has a variety of important biological activities to human health such as thermal sensing, perspiration, and pain relief etc.. Furthermore, capsaicin is a symbolic compound of vanilloid family which is associated with a receptor of vanilloid receptor subtype 1 (TRPV1). With the aim of demonstrating in vivo molecular imaging of capsaicin by positron emission tomography (PET), we have synthesized a PET molecule probe of 'IC-labeled capsaicin ([^<11>C]capsaicin) by 0-[^<11>C]methylation using [^<11>C]methyl iodide and a corresponding catechol precursor 1. The purified [^<11>C]capsaicin was intravenously injected in rat and the in vivo behaviors of [^<11>C]capsaicin in rat brain and whole body were observed by micro-PET. Interestingly, [^<11>C]capsaicin penetrated the blood-brain barrier and then was accumulated in the brain for approximately 10 min after the administration. In addition, [^<11>C]capsaicin was also accumulated in rat body surface which might be due to the binding of [^<11>C]capsaicin to TRPV1 receptor in the skin. Thus, the obtained PET images were positively correlated with the previously-reported in vitro and in vivo biological activities of capsaicin. Based on the synthesis of [^<11>C]capsaicin, we intend to further synthesize the diverse PET probes of ^<11>C-labeled capsaicin analogs with the objective of not only PET molecule imaging such as biologically important dietary constituents but also drug development focusing on TRPV1.
