Novel phenylpropanoid–amino acid adducts from Ligusticum chuanxiong†
Eight new amino acid derivatives (1–8) and two known compounds (9–10) were isolated from the rhizome of Ligusticum chuanxiong Hort. Their structures were established using UV, IR, HRESIMS, and NMR data. Notably, phenylpropanoid–amino acid adducts 1–6 are the first reported natural products, which possess a unique adduct structure. In addition, their analogues (1–5) were successfully synthesized by nucleophilic substitution and hydrolysis. The absolute configurations of 1–5 were determined by comparison of the specific rotations with those of their analogues and the natural amino acid methyl ester hydrochloride in acetic acid. In addition, these compounds were all evaluated for their neuroprotective effects, and compound 9 showed a moderate protective effect towards human neuroblastoma SH-SY5Y cell injury induced by H2O2.