Stereostructure of rhodojaponin I, II, and 3, toxins of Rhododendron japonicum, and of asebotoxin 3, toxin of Pieris japonica

Rhodomollosides A and B, glycosides of methyl everninate from the aerial parts of Rhododendron molle

Two new glycosides of methyl everninate, rhodomollosides A (1) and B (2), were isolated from the aerial parts of a medicinal plant Rhododendron molle. The structures of 1 and 2 were elucidated on the basis of detailed spectroscopic analyses as well as HPLC analyses for thiazolidine derivatives of their sugar moieties. The sugar moiety of rhodomolloside A (1) was elucidated to be a rare monosaccharide, D-allose, while rhodomolloside B (2) was assigned as a D-glucoside of methyl everninate. Furthermore, they were evaluated for their cytotoxicity against RAW264.7 cells, and for their inhibitory effects with a lipopolysaccharide (LPS)-stimulated murine macrophages RAW 264.7 cells model.

The basic chemical substances of three medicinal parts from Rhododendron molle G. Don

Rhododendron Molle G. Don belongs to Ericaceae family. As a toxic traditional Chinese medicine, its roots, flowers, and fruit are often mixed and substituted arbitrarily to treat rheumatoid arthritis in clinic. To clarify the main chemical basis of each medicinal part, and provide sufficient scientific basis for clinical application, analysis using HPLC-ELSD of the roots, flowers, and fruit from R. molle was established, and characteristic chemical constituents of them were separated by tracking. The structures were determined by NMR methods. Finally, 16, 21, and 18 compounds were obtained from the roots, flowers, and fruit, respectively. Overall, 49 compounds were obtained, of which 25 were identified for the first time in R. molle. Meanwhile, among the obtained compounds, 12, 11, and 6 characteristic peaks were identified from the roots, flowers, and fruit, respectively. Thus, the basic chemical substances of the medicinal parts of R. molle were determined initially.

Discovery of highly functionalized 5,6-seco-grayanane diterpenoids as potent competitive PTP1B inhibitors

Three competitive PTP1B inhibitory diterpenoids with a 5,6-seco-grayanane carbon skeleton (1–3) were isolated and identified fromRhododendron molle. A more potent competitive PTP1B inhibitor (9) was designed and prepared based on a docking study.

Antinociceptive Grayanane Diterpenoids from the Leaves of Pieris japonica

Thirteen new grayanane diterpenoids (1-13) and 15 known analogues (14-28) were isolated from a leaf extract of Pieris japonica. Their structures were determined by spectrometric and spectroscopic methods, including HRESIMS, NMR, IR, and UV. The absolute configurations of 1, 3, 7-9, and 16 were defined by single-crystal X-ray diffraction analysis. 17-Hydroxygrayanotoxin XIX (1) represents the first example of a 17-hydroxygrayan-15(16)-ene diterpenoid. Diterpenoids 1-28 were evaluated for their antinociceptive activities, and 4, 9, 13, 21, and 26-28 displayed significant antinociceptive activities at a dose of 5.0 mg/kg (ip) in the HOAc-induced writhing test in mice. 17-Hydroxygrayanotoxin XIX (1) exhibited potent antinociceptive effects with writhe inhibition rates of 56.3% and 64.8% at doses of 0.04 and 0.2 mg/kg, respectively, which were almost equivalent to the positive control, morphine. Rhodomollein X (26) and rhodojaponin VI (27) showed more potent antinociceptive effects than morphine at doses of 0.04 and 0.2 mg/kg. A preliminary structure-activity relationship for the antinociceptive effects of diterpenoids 1-28 is discussed.

Rhododendron Molle (Ericaceae): phytochemistry, pharmacology, and toxicology

Rhododendron molle G. Don, belonging to the Ericaceae family, is a traditional Chinese medicinal plant with a wide spectrum of pharmacological effects. This paper aimed to review the phytochemistry, pharmacology and toxicology of R. molle, and to discuss the tendency of future investigations on this plant. A systematic review of literature about R. molle was carried out using resources including classic books about Chinese herbal medicine, and scientific data bases including CNKI, Pubmed, SciFinder, Scopus, and Web of Science. Over 67 compounds, including diterpenes, triterpenes, flavonoids, and lignans, had been extracted and identified from R. molle. The extracts/monomers isolated from the root, flower and fruits of this plant were used as effective agents for treating pains, inflammatory diseases, hypertension, and pest, etc. In addition, diterpenes, such as rhodojaponin III, were considered as the toxic agents associated with the toxicities of this plant. These findings will be significant for the discovery of new drugs from this plant and full utilization of R. molle.

Structural Diversity and Biological Activity of the Genus Pieris Terpenoids

Secondary metabolites, particularly the grayanane diterpenoids produced by the members of genus Pieris, have been investigated in past decades for their remarkable antifeedant and insecticidal activities and toxicity. Grayanoids exhibit diverse biological properties such as antifeedant, insecticidal, cAMP regulatory, and sodium-channel-modulating activities. Structural complexity and diverse bioactivity of grayanoids have made them attractive targets for chemical, biological, and synthetic purposes. The current review synthesized findings published from 1966 to 2017, which include 135 reports that describe 130 terpenoids, including 103 grayanoids. The distribution, structure, skeleton, as well as the antifeedant and insecticidal activity of terpenoids, particularly the grayanane diterpenoids, are discussed in detail in this review. In cases where sufficient information is available, the structure-activity relationships of their antifeedant activity are also presented. We hope that this contribution will prompt more scientists to pay attention to these diterpenoids, which may be potentially applied in the agricultural field.

Tandem solid-phase extraction followed by HPLC-ESI/QTOF/MS/MS for rapid screening and structural identification of trace diterpenoids in flowers of Rhododendron molle

INTRODUCTION

'Naoyanghua', composed of the flowers of Rhododendron molle G. Don, is a traditional Chinese medicine that is widely known for its toxicity. Grayanane-type diterpenoids are the main active ingredients in R. molle, as well as possibly their toxicity: they are, however, difficult to isolate and analyse using common chromatographic methods, due to their small amounts and absence of conjugated groups, such as phenyl and α, β-unsaturated ketone.

OBJECTIVE

To establish a highly sensitive, selective and reliable method for the qualitative evaluation of trace diterpenoids in the flowers of R. molle by using tandem solid-phase extraction followed by high-performance liquid chromatography with electrospray ionisation quadrupole-time-of-flight mass spectrometry (HPLC-ESI/QTOF/MS/MS).

METHODS

Tandem solid phase extraction (SPE) was undertaken using a polyamide cartridge and a C18E cartridge in succession to enrich the trace diterpenoids. HPLC-ESI/QTOF/MS/MS was used to determine the fragmentation patterns of diterpenoids and to tentatively characterise their fragmentation pathways.

RESULTS

HPLC-ESI/QTOF/MS/MS detected a total of 14 diterpenoids, eight of which were identified by comparison with literature sources and six based on fragmentation analysis. Among the latter six, rhodojaponin VI-3-glucoside was tentatively identified as a new diterpenoid glycoside and rhodojaponin VII, rhodojaponin IV and rhodojaponin I were reported from R. molle for the first time.

CONCLUSION

By qualitative research of diterpenoids in this plant by HPLC-ESI/QTOF/MS/MS, a reliable methodology for the analysis of these active constituents of R. molle was established for the first time.

Phytochemicals and Biological Activities of Poisonous Genera of Ericaceae in China

The family Ericaceae is comprised of about 70 genera of which about 20 are found throughout China. Of these Ledum, Rhododendron, Enkianthus, Pieris, Craibiodendron, Gaultheria, Vaccinium, and Leucothoe are regarded as poisonous. Many species of these poisonous genera are used as Chinese herbal medicines for the treatment of, for example, inflammation, asthma, and coughs. Modern research has demonstrated that the toxic ingredients of these poisonous genera are chiefly tetracyclic diterpenes, which have adverse effects on the digestive, cardiovascular and nervous systems. Because various species of these poisonous genera also have medicinal functions, extensive studies of these plants have led to the identification of many kinds of compound. This paper compiles 306 compounds from the eight poisonous genera, reported in 141 references.

Three new highly acylated 3,4-seco-grayanane diterpenoids from the fruits of Pieris formosa

Phytochemical investigation on the fruits of Pieris formosa resulted in the isolation of three new highly acylated 3,4-seco-grayanane diterpenoids, pierisformotoxins E-G (1-3). Their structures were elucidated on the basis of extensive spectroscopic analysis, including 1D-, 2D-NMR, electrospray ionization-mass spectra (ESI-MS) and high resolution (HR)-MS.