Is 18α-Glycyrrhizin a real natural product? Improved preparation of 18α-Glycyrrhizin from 18β-Glycyrrhizin as a positive standard for HPLC analysis of licorice extracts h-honda 【2022】 Kritamorn Jitrangsri1), Kazuaki Kamata2), Mana Akiba2), Yoshie Yajiri2), Masami Ishibashi1), Jin Tatsuzaki2) & Tsutomu Ishikawa2) 1) Chiba University2) Tokiwa Phytochemical Co., Ltd. Journal of Natural Medicines (2022)