Phytochemical and chemotaxonomic study on the leaves of Rhododendron amesiae (2023)

Chemical investigation of the whole plant of Sauropus hirsutus Beille led to the isolation of eight quinolines and two known flavonoids. Furthermore, five quinolines were new, two were reported in plant for the first time and one was known. Cytotoxicity evaluation against cholangiocarcinoma, KKU-M156, showed that the most active compound was 4-hydroxy-6-methoxy-7,8-methylenedioxyquinaldine (IC₅₀ 20.54±6.82 µM) which was a little more active than the cisplatin standard (IC₅₀ 24.39±1.14 µM).

Chinese Journal of Natural Medicines, Volume 19, Issue 3, 2021, pp. 181-187

Rhododendron molle G. Don is first recorded in Shengnong’s Herbal Classic, and its fruits, which are termed as Liuzhouzi, are often used to treat rheumatoid arthritis in Chinese folk. During our ongoing investigation to develop a safer and potential new arthritis therapy, a process for the preparation of diterpenoid fraction from Rhododendron mollefruits was established. In order to evaluate the main components and the anti-rheumatoid arthritis effect of the diterpenoid fraction, phytochemical and pharmacological experiments were used. As the result, the main components of diterpenoid fraction were identified as rhodojaponin III (1), rhodojaponin VI (2), 2-O-methylrhodojaponin (3), and 5′-β-D-glucopyranosy-loxyjasmonic acid (4). These four components constitute greater than 95% of diterpenoid fraction using area normalization method of HPLC-ELSD. The results of CIA rat experiment showed that high dose of diterpenoid fraction (0.6 mg·kg^–1·d^–1) significantly alleviated the symptoms of rheumatoid arthritis, similar to tripterygium polyglycosides, an effective RA therapy. Preliminary mechanism studies indicated that diterpenoid fraction significantly inhibited the abnormal proliferation of T and B lymphocytes, and remarkably reduced the levels of pro-inflammatory cytokines IL-6, IL-1β and TNF-α. Overall, our findings may provide a more effective and safe alternative treatment for RA using common clinical Chinese medicines like tripterygium polyglycosides.

Biochemical Systematics and Ecology, Volume 94, 2021, Article 104184

Phytochemical investigation of roots from Solanum asterophorum led to the identification of 37 compounds, including 9 phenolic acid derivatives, 2 alkamides, 7 hydroxy-carboxylic acid derivatives, and 19 steroidal alkaloids. The dereplication of compounds was performed by extensive analysis by ultra-performance liquid chromatography coupled with a diode array and quadrupole time-of-flight mass spectrometry. With the exception of alkaloid isojurubidine, all compounds were reported from Solanum asterophorum for the first time. The chemotaxonomic significance of the isolated compounds was discussed.

Biochemical Systematics and Ecology, Volume 95, 2021, Article 104228

Eight phenolic compounds, including two catechins (1 and 2), two proanthocyanidins (3 and 4), three lignans (5–7), and one phenol (8), were isolated from roots of Vaccinium dunalianum Wight (Ericaceae), together with two triterpenes (9 and 10). All of them were isolated from the title plant for the first time. Their chemical structures were established based on the extensive MS and NMR spectroscopic analysis. Compounds 6–10 acquired initially from the genus Vaccinium, showed some significances in chemotaxonomy.

Phytochemistry, Volume 196, 2022, Article 113083

Five undescribed triterpenoids, two unusual omphalane-type sesquiterpenoids together with twenty-five known compounds were isolated from the leaves and stems of Rhododendron minutiflorum Hu. The absolute configurations of 1–3 and 6 were established by single-crystal X-ray diffraction analysis and electronic circular dichroism (ECD). Compounds 6–7 feature the rare omphalane-type sesquiterpene skeleton and are verified by single-crystal X-ray diffraction analysis for the first time. In the biological activity assay, most of the triterpenoids have different degrees of inhibitory effects on α-glucosidase, with IC₅₀ values ranging from 6.97 to 229.3μM (the positive control drug acarbose has an IC₅₀ value of 3.07×10⁻³μM). Structure and activity relationship (SAR) study reveals that the oxidation degrees of C-3, C-8, or C-11 to C-13 of the ursane-type triterpenoid influence the inhibitory activity dramatically.

Phytochemistry, Volume 180, 2020, Article 112524

Eight pairs of meroterpenoid enantiomers and four achiral meroterpenoids were isolated from Rhododendron anthopogonoides Maxim. Seventeen of them, named (+)-/(−)-anthoponoids A−G, (+)-daurichromene D, and anthoponoids H and I, are undescribed compounds with structural diversity. Their structures were characterized herein by a combined application of spectroscopic techniques, X-ray crystallographic analysis, ECD calculation, and the modified Mosher's method. (+)-/(−)-Anthoponoid A and anthoponoid I are the first Rhododendron meroterpenoids found to possess a hexahydroxanthene motif and a diterpene unit, respectively. Some isolates were identified as NF-κB pathway inhibitors, and (+)-anthoponoid E, (−)-anthoponoid G, and anthoponoid H showed suppressive effects on LPS-induced inflammatory responses in RAW 264.7 macrophages.

Tetrahedron, Volume 70, Issue 29, 2014, pp. 4317-4322

Six new grayanane diterpenoids, principinols A–F (1–6), were isolated from Rhododendron principis. Compounds 1 and 2 possess unprecedented 6,10-epoxy and 5α-OH moieties, and 1 and 3 are the first two examples of 9α-H in grayanoids. Their structures were determined by extensive spectroscopic analysis, and the absolute configurations of 1–4 were assigned by single-crystal X-ray crystallography. Compounds 4 and 5 inhibit PTP1B phosphatase activity invitro. A preliminary structure–activity relationship discussion is presented.