LC-MS/MS detection of citrus unshiu peel-derived flavonoids in the plasma and brain after oral administration of yokukansankachimpihange in rats

1. Yokukansankachimpihange (YKSCH), a Kampo formulation combining Citrus unshiu peel (CUP) and Pinellia tuber (PT) with yokukansan (YKS), has been recently used to treat the behavioral and psychological symptoms of dementia. Several flavonoids derived from CUP and PT reportedly exhibit psychopharmacological activity, but it remains unclear whether these flavonoids reach the brain after oral administration of YKSCH. 2. In this study, we first measured eight target flavonoids in the plasma and brain in rats orally administered YKSCH. Among these flavonoids, hesperidin, narirutin, nobiletin, and heptamethoxyflavone (HMF) were detected in the plasma, and nobiletin and HMF were detected in the brain. 3. Next, to clarify whether CUP and PT affect the pharmacokinetics of YKS ingredients in YKSCH, the plasma pharmacokinetics of geissoschizine methyl ether (GM) as a representative active ingredient in YKS was examined in rats orally administered YKSCH or YKS. There was no significant difference between the two groups, inferring that the pharmacokinetics of GM may not be affected by the two additional crude drugs. 4. Taken together, this study suggests that the CUP-derived flavonoids nobiletin and HMF may be responsible for the psychopharmacological effects of YKSCH in addition to YKS ingredients.

1. 加味抑肝散（Yokukansankachimpihange, YKSCH）是一种由温州蜜柑皮（Citrus unshiu peel, CUP）、半夏块茎（Pinellia tuber, PT）与抑肝散（YKS）配伍组成的汉方药复方，近期被应用于痴呆的行为与精神症状治疗。据报道，源自CUP与PT的多种黄酮类化合物均具有精神药理活性，但目前尚不明确口服给予YKSCH后，此类黄酮类化合物能否进入脑部。
2. 本研究首先对口服给予YKSCH的大鼠血浆及脑组织中的8种目标黄酮类化合物进行了定量检测。结果显示，血浆中可检测到橙皮苷（hesperidin）、野漆树苷（narirutin）、川陈皮素（nobiletin）以及七甲氧基黄酮（heptamethoxyflavone, HMF）；而脑组织中仅检出川陈皮素与HMF。
3. 为明确CUP与PT是否会影响YKSCH中YKS成分的药代动力学特征，本研究进一步考察了分别口服给予YKSCH或单纯YKS的大鼠体内，抑肝散代表性活性成分吉斯禅碱甲醚（geissoschizine methyl ether, GM）的血浆药代动力学过程。两组大鼠的GM药代动力学参数无显著差异，由此推测，额外添加的两味生药并不会对GM的药代动力学过程产生影响。
4. 综合以上研究结果，本研究提示，除YKS原有活性成分外，源自CUP的川陈皮素与HMF或许是YKSCH发挥精神药理作用的关键物质基础。