2.1. Plant materials and sample preparation
Dried mature seeds, leaves, stems, and roots of S. japonica were
obtained from National Baekdudaegan Arboretum, 2019. The voucher
specimen was identified by Dr. Y. S. Kim, National Baekdudaegan
Arboretum and deposited at the herbarium of the Natural Product
Institute of Science and Technology, Chung-Ang University, Anseong,
Republic of Korea. Five grams of dried mature seeds, leaves, stems, and
roots of S. japonica were repeatedly extracted with 70% ethanol
(100 mL × 3) at 80°C for 3 h and then filtered using 0.45 µm of
polyvinylidene fluoride (PVDF) membrane filter for high-performance
liquid chromatography (HPLC).