Orengedokuto (OGT) is a Kampo prescription characterized by a strong bitter taste, consisting of Coptidis Rhizoma (CR), Phellodendori Cortex (PC), Scutellariae Radix (SR), and Gardeniae Fructus (GF). OGT is a multicomponent drug and one of the constituents contained is the alkaloid berberine, which is widely recognized for its bitter taste. Berberine is known to bond with baicalin, one of the constituents of SR, in the decoction to form a precipitate. However, the extent to which this precipitation is responsible for the bitter taste of OGT is unknown. In this study, we quantitatively evaluated the bitter taste of OGT extracts utilizing a taste-sensing system that can objectively measure taste intensity and investigated the effects of the constituents of OGT on bitter taste.

Eight samples (OGT, CR, PC, SR, GF, CR + SR, PC + SR, and OGT without SR (OGT－SR)) were tested, and the content of free berberine in each extract was then determined. The response values to the bitter taste sensor were OGT－SR >> CR ≥ PC > OGT > CR + SR and PC + SR, in agreement with the previous reports. A strong positive correlation was observed between the response value of each sample to the bitter taste sensor and the content of free berberine. Therefore, when decocted with SR, the berberine-baicalin complex formed and precipitated, reducing the bitter taste values attributed to berberine as detected by the taste-sensing system.

This study quantitatively evaluated the bitter taste of OGTs and objectively validated the results of human sensory tests.

The family name for the botanical origin of crude drugs in the Japanese Pharmacopoeia (JP) is based on the modified Engler system. However, the Angiosperm Phylogeny Group (APG) system, which is a novel classification system for Angiospermae using DNA information, was reported in 1998 and revised three times to date. Now, the APG system is widely accepted in not only plant systematics but also other fields. In this study, we prepared the comparison table between the two systems for family names of crude drug items in the JP. The resultant table was provided for General Information for the JP.

In Japan, it is illegal to sell herbal products and powders that contain psychoactive compounds. Many of these illegal herbal products are presumed to be manufactured by artificially adding synthetic cannabinoids to plant pieces that do not naturally have any psychoactive properties, particularly products that are expected to have cannabis-like effects. In recent years, semi-synthetic cannabinoids prepared by performing simple chemical transformations of Cannabis plant extracts have appeared on the illegal drug market and are often distributed as vape products. Although semi-synthetic cannabinoids are known not to be detected in plants, plant pieces containing the semi-synthetic cannabinoid tetrahydrocannabinol-O-acetate (THC-O) were found in this study. Therefore, we investigated the botanical origin of this illegal herbal product by performing GC-MS and liquid chromatography–mass spectrometry analysis, DNA sequence analysis, and morphological observation with a stereoscopic microscope. Cannabidiol (CBD), THC-O, and cannabidiolic acid, which is the inactive precursor of CBD in plants, were detected in this product. DNA sequence analysis revealed that most of the plant pieces were from Cannabis sativa L. In combination with the results from the morphological observation, most of the plant pieces were identified as coming from the Cannabis plant. Accordingly, it was suggested that the investigated illegal herbal product consisted of Cannabis plant pieces, the main component of which was CBD, with THC-O artificially added to the pieces.