Linaburiosides A-D, acylated iridoid glucosides from Linaria buriatica

Meroterpenes and prenylated benzoylphloroglucinol from the flowers of Hypericum formosanum

Formohyperins A-F, previously undescribed meroterpenes, and grandone, a prenylated benzoylphloroglucinol being considered to be one of their biogenetic precursors, were isolated from the flowers of a Hypericaceous plant, Hypericum formosanum Maxim. Detailed spectroscopic analyses showed that formohyperins A-D were meroterpenes with an enolized 3-phenylpropane-1,3-dione moiety. Formohyperins E and F were elucidated as meroterpenes having a 4-benzoyl-5-hydroxycyclopent-4-ene-1,3-dione moiety. Formohyperins A-C and E were optically active, and their absolute configurations were deduced by comparison of the experimental and TDDFT calculated ECD spectra. In contrast, formohyperin D was concluded to be a racemate. Formohyperins A-F and grandone were found to show inhibitory activities against LPS-stimulated IL-1β production from murine microglial cells with EC50 values of 13.2, 6.6, 8.5, 24.3, 4.1, 10.9, and 3.0 μM, respectively.

Dauferulins A-L, daucane-type sesquiterpenes from the roots of Ferula communis: Their structures and biological activities

Phytochemical study on the roots of a medicinal plant Ferula communis L. (Apiaceae) resulted in the isolation of 20 sesquiterpenes including 12 previously undescribed compounds, dauferulins A-L (1-12). The detailed spectroscopic analysis revealed 1-12 to be daucane-type sesquiterpenes with a p-methoxybenzoyloxy group at C-6. The absolute configurations of 1-12 were deduced by analysis of the ECD spectra. Dauferulins A-L (1-12), known sesquiterpenes (13-20), and analogues (14a-14l) derived from 6-O-p-methoxybenzoyl-10α-angeloyloxy-jeaschkeanadiol (14) were evaluated for their effects on AMPK phosphorylation in human hepatoma HepG2 cells as well as inhibitory activities against erastin-induced ferroptosis on human hepatoma Hep3B cells and IL-1β production from LPS-treated murine microglial cells.

Communiferulins, farnesylated coumarins from the roots of Ferula communis and their anti-neuroinflammatory activity

Three new farnesylated coumarins, communiferulins A-C (1-3), and a farnesylated chromone, ferchromone (4), were isolated from the roots of an Apiaceous plant Ferula communis. Their structures including the relative configurations were elucidated by a combination of spectroscopic analyses and calculations of the NMR data. Communiferulins A-C (1-3) had dihydrofuran rings fused to C-3 and C-4 of their coumarin moieties, while 3 possessed one additional furan ring. HPLC analyses using a chiral column showed 1-4 to be racemates, and the absolute configurations of (+)-1, (-)-1, (+)-2, and (-)-2 were deduced by comparison of their ECD spectra with TDDFT-calculated spectra. Communiferulins A (1) and B (2), and ferchromone (4) showed inhibitory activities on IL-1β production from LPS-stimulated microglial cells.

Lanicepines A and B, Sesquiterpenes with Amino Acid-Derived Substituents from the Flowering Aerial Parts of Saussurea laniceps

Two new guaianolide sesquiterpenes, lanicepines A (1) and B (2), possessing unusual amino acid-derived substituents at C-13, were isolated from the flowering aerial parts of Saussurea laniceps, a traditional herbal medicine also known as "snow lotus". The structures of 1 and 2 were elucidated based on spectroscopic analysis including applications of the modified Mosher's method and Marfey's method as well as ECD calculations. Lanicepine A (1) contains a dihydropyridinone moiety with a carbamoyl and a hydroxymethyl group. This substituent was considered to consist of asparagine and a C₄ unit. In contrast, lanicepine B (2) has a substituent that seems to be derived from l-proline and a C₄ unit. Lanicepines A (1) and B (2) and two related known sesquiterpenes isolated from the same plant material, 11β,13-dihydrodesacylcynaropicrin (3) and 11β,13-dihydrodesacylcynaropicrin 8-O-β-d-glucoside (4), demonstrated inhibitory activity against IL-1β production from LPS-stimulated microglial cells.

Phytochemical studies on traditional herbal medicines based on the ethnopharmacological information obtained by field studies

Traditional herbal medicines, which have been used in the matured traditional medical systems as well as those have been used in ethnic medical systems, are invaluable resources of drug seeds. Ethnobotanical and ethnopharmacological survey may provide useful information of these herbal medicines, which are valuable for searching new bioactive molecules. From this viewpoint, we have been performing the ethnobotanical and ethnopharmacological field studies in Yunnan Province and Guangxi Zhuang Autonomous Region, China, and Mongolia. Phytochemical studies on traditional herbal medicines were performed based on the information obtained by our ethnobotanical survey. Herbal medicines used in Uzbekistan and Bangladesh were also investigated on the basis of the ethnopharmacological information obtained from collaborative researchers in the respective regions. Some studies were carried out for searching active substance(s) based on bioassay-guided fractionation and isolation. Over 150 new molecules were isolated in these studies, and their various biological activities were also demonstrated. This review summarizes the results of phytochemical studies of those traditional herbal medicines as well as biological activities of the isolated molecules.

Hyperdioxanes, dibenzo-1,4-dioxane derivatives from the roots of Hypericum ascyron

Six dibenzo-1,4-dioxane derivatives (1-6) were isolated from the roots of a Hypericaceous plant Hypericum ascyron. Spectroscopic analyses revealed 2 and 4-6 to be new compounds. The partial racemic natures of 1-3 were concluded by chiral HPLC analyses, while 5 was confirmed to be a racemate. The absolute configurations 1-4 were deduced on the basis of ECD calculations. Biological activity evaluation of the dibenzo-1,4-dioxane derivatives along with two related compounds: hyperdioxanes A (7) and B (8), previously isolated from the same plant material by our group demonstrated that 7 exhibit an anti-HIV activity (IC₅₀ 5.3 μM, TI 7.2) while 8 showed an inhibitory effect on IL-1β production (inhibition rate: 72.3% at 6.3 μM) from LPS-stimulated microglial cells.

Characteristic metabolites of Hypericum plants: their chemical structures and biological activities

Plants belonging to the genus Hypericum (Hypericaceae) are recognized as an abundant source of natural products with interesting chemical structures and intriguing biological activities. In the course of our continuing study on constituents of Hypericum plants, aiming at searching natural product-based lead compounds for therapeutic agents, we have isolated more than 100 new characteristic metabolites classified as prenylated acylphloroglucinols, meroterpenes, ketides, dibenzo-1,4-dioxane derivatives, and xanthones including prenylated xanthones, phenylxanthones, and xanthonolignoids from 11 Hypericum plants and one Triadenum plant collected in Japan, China, and Uzbekistan or cultivated in Japan. This review summarizes their chemical structures and biological activities.

Studies on non-medicinal parts of plant materials: Triterpenes from the roots of Schisandra chinensis

Phytochemical study on a non-medicinal part of a plant material for herbal medicine, the roots of Schisandra chinensis, was conducted to isolate five new triterpenes, schinensins A-D (1-4) and 3-O-methylchangnanic acid (5), together with 21 known compounds including 10 triterpenes, one sterol, two sesquiterpenes, seven lignans, and one flavonoid. The structures of new triterpenes (1-5) were assigned on the basis of spectroscopic analyses aided with TDDFT ECD calculations. Schinensin A (1) was a dinortriterpene possessing 28-norschiartane skeleton, while schinensins B-D (2-4) were assigned as 3,4:9,10-disecocycloartane, 3,4-secocycloartane, and cycloartane triterpenes, respectively. In an evaluation of antiproliferative activities against human cancer cell lines, some triterpenes exhibited significant activities against human breast carcinoma MCF-7 cells as compared to the other cell lines (A549, HeLa, and RPMI8226).

Diterpenes from an Uzbek medicinal plant Perovskia scrophulariifolia: Their structures and anti-neuroinflammatory activity

Phytochemical investigation on the aerial parts of a Lamiaceous medicinal plant Perovskia scrophulariifolia collected in Uzbekistan resulted in the isolation of two new 20-norabietane diterpenes, along with thirteen known diterpenes including one 20-norabietane, eight abietanes, one 6,7-secoabietane, and three icetexanes. The structures of new 20-norabietane diterpenes, perovsfolins C (1) and D (2), were elucidated by spectroscopic analyses aided with calculations of ECD spectra. Perovsfolin C (1) is the first 20-norabietane diterpene possessing a 1,11-epoxy moiety, while perovsfolin D (2) is a 20-norabitetane diterpene with a 2-hydroxy-1,4-quinone moiety as C-ring. Anti-neuroinflammatory activity of the isolated diterpenes on microglial cells was evaluated.

Diterpenoids caryopterisoids D - Q and iridoid glucoside derivatives caryopterisides F - H from Caryopteris glutinosa

Fourteen undescribed diterpenoids caryopterisoids D - Q, three undescribed iridoid glucoside derivatives caryopterisides F - H, and 8 known diterpenoids were isolated from the 95% aqueous ethanolic extract of Caryopteris glutinosa. Their structures were elucidated on the basis of spectroscopic data analysis and chemical derivation studies. The structure and absolute configuration of caryopterisoid D were confirmed by X-ray crystallographic analysis. Caryopterisoids K and R, royleanone, 6α-hydroxydemethylcryptojaponol, and teuvincenone E were shown to reduce the biosynthesis of estrogen E2 with IC₅₀ values from 0.25 to 3.06 μM in cell-based estrogen biosynthesis assays system.