This article is an explanatory review on a study of licorice stored in Shosoin Repository reported in this journal by Dr. Shoji Shibata in 2003 (Proc. Jpn. Acad. Ser. B 79, 176–180). The study using new technologies at that time for identification of plant species was a follow-up research of his own study performed half a century before. The study revised previous results and elucidated that the licorice stored in Shosoin Repository was derived from Glycyeehiza uralensis.

Structural studies of natural products have been a driving force in the development of organic chemistry throughout its long history, especially in the early years. Recently, structure determination based on new concepts has also gained momentum. In this review we will mainly discuss the functional structures of natural products that account for the mechanisms of action largely from our studies. The topics include marine natural products, amphidinols, and ladder-shaped polyether compounds, which are known as potent antifungal agents and important marine biotoxins, respectively. Nuclear magnetic resonance studies for determining the stereochemistry of amphidinol 3 and its conformation in lipid-bilayer membranes will be presented in detail.

Photoredox catalysis, which facilitates organic transformations under visible-light irradiation, including sunlight, has garnered considerable attention as a cornerstone of green chemistry. Since the early days of this field around 2010, the author’s group has made substantial contributions to its advancement. This review article provides a concise overview of the history and fundamental principles of photoredox catalysis, along with highlights of the achievements by the author’s group. Although colorless organic compounds cannot be directly activated by visible light, photo-excited colored catalysts, with their two half-occupied frontier orbitals, play dual roles via electron transfer processes with organic substrates. The hole in the lower-energy orbital functions as a single-electron oxidant, whereas the electron in the higher-energy orbital acts as a single-electron reductant, enabling the formation of reactive radical intermediates from diverse organic compounds, including colorless ones. The discussion will focus on the key transformations developed by the author’s group, including bimetallic photocatalysis, fluoroalkylation, and catalysis in aqueous media.

In Japan, serious food poisoning among individuals who took supplement tablets for lowering plasma cholesterol levels have been publicized since late March 2024. The tablets were prepared from red yeast rice (RYR), a product of Monascus pilosus. Puberulic acid (PA) was detected as an unexpected compound in tablets that caused food poisoning. We conducted an on-site investigation at the RYR production factory to determine the cause of PA contamination of the tablets. Fungi capable of producing PA were detected in wipe samples from the factory and were identified as Penicillium adametzioides. To understand the route through which P. adametzioides contaminated RYR and produced PA, coculture experiments with M. pilosus and P. adametzioides were performed. P. adametzioides grew on rice covered with M. pilosus and produced PA. These results suggest that PA-producing P. adametzioides inhabited the RYR production factory and accidently contaminated the culture of M. pilosus. Consequently, RYR tablets contaminated with PA were manufactured and caused the food poisoning outbreak.