Triterpenoid saponins from Pterocephalus hookeri

Bioactive pentacyclic triterpenoids from the whole plants of Pterocephalus hookeri

Eight undescribed triterpenoids (pterohoonoids A-H) including four oleananes, one nor-oleanane and three nor-ursanes, along with seven known analogues, were isolated from the whole plants of Pterocephalus hookeri (Dipsacaceae). The structures with relative stereochemistries of these molecules were elucidated mainly by spectroscopic analyses, and the absolute configurations of the undescribed ones were assigned by a variety of methods, including time-dependent density functional theory (TD-DFT) based electronic circular dichroism (ECD) calculation, Rh₂(OCOCF₃)₄-induced ECD experiment and chemical transformation. The inhibitory effects toward the diabetes target α-glucosidase of all the isolates were assessed, and four of them exhibited pronounced activity with IC₅₀ values ranging from 6.8 to 55.8 μM. In addition, four compounds also showed inhibition against the nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW264.7 macrophage cells (IC₅₀ = 12.4-63.7 μM). Further assays demonstrated that the most active compound pterohoonoid A inhibited the release of two key pro-inflammatory cytokines TNF-α and IL-6 in a dose-dependent manner.

Pterocephanoside A, a new iridoid from a traditional Tibetan medicine, Pterocephalus hookeri

This work obtained and identified pterocephanoside A (1), one new iridoid glucoside derivative with rare structure of three iridoid glycosides linked to cyclopenta[c]pyran-3(1H)-one, and 10 known iridoids (2-11) from Pterocephalus hookeri through silica gel column chromatography and semi-preparative HPLC. The structure of the new compound was confirmed by 1D and 2D NMR and HRMS data analysis. Compounds 1 and 2 were isolated from this plant for the first time. The iridoids mostly possessed seco-iridoid subtype and iridoid subtype skeletons from P. hookeri. Compounds 1, 3, 4, and 6-11 showed weak anti-inflammatory activity.

Pterocephin A, a novel Triterpenoid Saponin from Pterocephalus hookeri induced liver injury by activation of necroptosis

BACKGROUND

Pterocephalus hookeri (C. B. Clarke) Höeck, a Tibetan medicine widely used for treatment of rheumatoid arthritis, was recorded in Chinese Pharmacopoeia (2020 version) with slight toxicity. The liver injury was observed in mice with administration of n-butanol extract (BUE) in our previously study. However, the toxic components and the mechanism were still unrevealed.

PURPOSE

The present study was aimed to isolate and structural elucidate of the toxic compound pterocephin A (PA), as well as evaluate its liver toxicity and investigate its mechanism.

METHODS

PA was isolated from the BUE of P. hookeri. Its structure was determined by analysis of HRMS, NMR and ECD data. L-02 cellular viability, LDH, ALT, AST, ROS, intracellular Ca²⁺ and the fluidity of cell membrane were assessed by multifunctional microplate reader. The PI staining, cell membrane permeability assessment, and mitochondrial fluorescence staining analysis were determined through the fluorescence microscope. Liver samples for mice were assessed by pathological and immunohistochemistry analysis. Expression levels of indicated proteins were measured by western blotting assays.

RESULTS

PA was determined as a previously undescribed oleanolane-type triterpenoid saponin. In vitro study revealed PA significantly induced hepatotoxicity by inhibition of L-02 cell growth, abnormally elevation of ALT and AST. Mechanically, PA induced the damage of cell membrane, fragmentation of mitochondria, and subsequently increase of intracellular Ca²⁺ and ROS levels, which trigged by necroptosis with the activation of RIP1 and NF-κB signaling pathways. In vivo study confirmed PA could induce liver injury in mice with observation of the body weight loss, increasing of serum ALT and AST, and the histopathological changes in liver tissues.

CONCLUSION

Our present study indicated that PA was an undescribed toxic constituent in P. hookeri to induce liver injury in mice by activation of necroptosis and inflammation. And the findings are of great significance for the clinical use safely of this herb.

Traditional uses, phytochemistry, pharmacology, and toxicology of Pterocephalus hookeri (C. B. Clarke) Höeck: a review

Pterocephalus hookeri (C. B. Clarke) Höeck is a member of the Dipsacaceae family and has been used in traditional Tibetan medicine for thousands of years. P. hookeri clears heat, detoxifies, stops dysentery, eliminates distemper, dispels wind, and relieves stagnation and is mainly prescribed for heat syndrome, dysentery, arthritis, and plague. Approximately 93 chemical compounds have been isolated and identified from P. hookeri, including iridoid glycosides, lignan and triterpenoids. Meanwhile, modern pharmacological studies have shown that P. hookeri has anti-inflammatory, anti-rheumatoid arthritis, analgesic, anticancer, and neuroprotection activities. However, studies on the in vivo pharmacokinetics and mechanism of action, discovery of quality markers, and qualitative and quantitative analysis are still insufficient. Hence, this paper provides a comprehensive review of the ethnic medicine, phytochemistry, pharmacology, and toxicology of P. hookeri to increase the understanding of the medicinal value of P. hookeri.

Pterocephalus hookeri (C. B. Clarke) Höeck has been used in traditional Tibetan medicine for thousands of years. The existing research results of P. hookeri are summarized, and will provide a basis for the further development of new drugs.

Semipapposides A-M, triterpenoid bidesmosides saponins from the roots of Scabiosa semipapposa

Phytochemical investigations of the roots of Scabiosa semipapposa Salzem ex D.C. have led to the isolation of 12 undescribed triterpenoid saponins named semipapposides A-L, one undescribed saponin semipapposide M obtained as an inseparable mixture, together with three known oleanolic acid glycosides. Their structures were elucidated by analysis of 1D and 2D-NMR (¹H-¹H COSY, TOCSY, HSQC-TOCSY, HSQC, ROESY or NOESY, and HMBC) spectroscopic data and mass spectrometry (HR-ESI-MS), and by comparison with those of related metabolites. All saponins possess a partial sequence rhamnopyranosyl-(1 → 2)-xylopyranosyl or rhamnopyranosyl-(1 → 2)-arabinopyranosyl- at C-3 of the aglycon and a gentiobiose unit at C-28. These results represent a contribution to the knowledge of the saponins of Scabiosa species and their chemotaxonomy.

Antinociceptive and anti-inflammatory activities of a standardizedextract of bis-iridoids from Pterocephalus hookeri

ETHNOPHARMACOLOGICAL RELEVANCE

Pterocephalus hookeri (C.B. Clarke) Höeck, one of the most popular Tibetan herbs, has been widely applied in Tibetan medicine prescriptions. Chemical investigations have led to the isolation of many bis-iridoids. However, the pharmacological activities of bis-iridoid constituents of this plant have never been reported before.

AIM OF THE STUDY

This study evaluated the anti-inflammatory and analgesic activities of afraction of bis-iridoid constituents of P. hookeri (BCPH) in order to provide experimental evidence for its traditional use, such as for cold, flu, and rheumatoid arthritis.

MATERIALS AND METHODS

The analgesic effects of BCPH were investigated using the hot-plate test and acetic acid-induced writhing test. The anti-inflammatory activities were observed using the following models: carrageenin-induced edema of the hind paw of rats and xylene-induced ear edema in mice. The effects of dexamethasone administration were also studied.

RESULTS

BCPH significantly increased the hot-platepain threshold and reduced acetic acid-induced writhing response in mice. Moreover, BCPH remarkably inhibited xylene-induced ear edema and reduced the carrageenin-induced rat paw edema perimeter.

CONCLUSION

The results reveal that BCPH has central, peripheral analgesic activities as well as anti-inflammatory effects, supporting the traditional application of this herb in treating various diseases associated with inflammation and pain.

The anti-arthritic activity of total glycosides from Pterocephalus hookeri, a traditional Tibetan herbal medicine

CONTEXT

Pterocephalus hookeri (C. B. Clarke) Hock., a traditional Tibetan herbal medicine rich in glycosides, has been used to treat several diseases including rheumatoid arthritis.

OBJECTIVE

To evaluate the anti-arthritic activity of total glycosides from P. hookeri, and its possible mechanisms of action.

MATERIALS AND METHODS

Anti-arthritic activity of total glycosides from P. hookeri (oral administration for 30 days at 14-56 mg/kg) was evaluated using paw swelling, arthritis scores and histopathological measurement in adjuvant-induced arthritis (AA) Sprague-Dawley rats. The NF-κB p65 expression in synovial tissues, and serum superoxide dismutase (SOD) activity, malondialdehyde (MDA) and nitric oxide (NO) levels was measured in AA rats, respectively. Further assessment of anti-inflammatory and analgesic activities of these glycosides were carried out using inflammation and hyperalgesia models induced by xylene, carrageenan, agar and acetic acid, respectively.

RESULTS

Total glycosides (56 mg/kg) decreased the paw swelling (38.0%, p < 0.01), arthritis scores (25.3%, p < 0.01) and synovial inflammation in AA rats. The glycosides significantly (p < 0.05-0.01) attenuated the inflammation induced by xylene, carrageenan, acetic acid and agar, increased the pain threshold in acetic acid-induced writhing in mice and mechanical stimuli-induced hyperalgia in AA rats. The glycosides (14, 28, 56 mg/kg) also suppressed the NF-κB p65 expression (33.1-78.2%, p < 0.05-0.01), reduced MDA (21.3-35.9%, p < 0.01) and NO (20.3-32.4%, p < 0.05-0.01) levels, respectively, enhanced the SOD activity (7.8%, p < 0.05) at 56 mg/kg in AA rats.

DISCUSSION AND CONCLUSION

Our findings confirmed the anti-arthritic property of the total glycosides from P. hookeri, which may be attributed to its inhibition on NF-κB signalling and oxidative stress.

Four new bis-iridoids isolated from the traditional Tibetan herb Pterocephalus hookeri

Pterocenoids A-E (1-4), which Pterocenoids A(1) is one novel dimer containing a pyridine monoterpene alkaloid; and Pterocenoids B-E (2-4) are rare arranged non-glycosidic bis-iridoids were isolated from Pterocephlus hookeri. The structures of the compounds were established by 1D and 2D NMR spectroscopy and mass spectrometry. All bis-iridoids isolated from P. hookeri were found to possess secoiridoid/iridoid subtype skeletons. Hence, bis-iridoids can be regarded as the chemotaxonomic markers of P. hookeri. The origins of the new bis-iridoids (1-4) were postulated and their activities of inhibition of the NF-κB pathway were assayed and compounds 1-3 showed moderate activity in inhibiting NF-κB.

Monoterpenoid glucoindole alkaloids and iridoids from Pterocephalus pinardii

A new secondary metabolite, pterocephaline, along with the known cantleyoside, 7alpha-morroniside, 3beta,5alpha-tetrahydrodesoxycordifoline lactam, 5S-5-carboxyvincoside, sweroside, and loganin have been isolated from the aerial parts of P. pinardii (Dipsacaceae). Moreover, cantleyoside-methyl-hemiacetal and cantleyoside-dimethyl-acetal were obtained as seco-iridoid artifacts. The structures were elucidated by extensive spectroscopic methods including 1D-((1)H, (13)C and TOCSY) and 2D-NMR (DQF-COSY, HSQC and HMBC). Monoterpenoid glucoindole alkaloids were encountered for the first time in Dipsacaceae family.

Flavonoid C-Glycosides from Pterocephalus Sanctus Growing in Egypt

Two flavonoid C-glycosides, isolated from Pterocephalus sanctus (Dipsaceae), were identified as luteolin-6-C-β-D-glucoside-7-O-methyl ether and apigenin-6-C-β-D-glucoside-7-O-methyl ether on the basis of spectroscopic studies.

Capillary electrophoresis of phytochemical substances

Applications of capillary electrophoresis (CE) for analysis of phytochemical substances (e.g. flavonoids, alkaloids, terpenoids, phenolic acid, quinones and coumarins) are reviewed. For example, CE analysis of sixteen tea ingredients were achieved within 10 min with the good precision (RSDs% <1% for intra-day and 2% for inter-day) and linearity (R(2)>0.990). Quantitation of sanguinarine and chelerythrine, alkaloids from Sanguinaria canadensis L. or Macleaya cordata (Wild) Br. R. by CE showed excellent linearity (R(2)>0.998), precision (RSD%=1.8%) and detection limit (2.4-3.0 microM). Determination of antraquinone-1-sulphonate was also obtained by this technique with good linearity (R(2)>0.9999), precision (RSD%=2%) and detection limit (0.7 microg/ml). Results of CE analysis from several studies are comparable to those of high performance liquid chromatography (HPLC), but the former is more useful for complex mixture samples where the analysis demands higher resolving power. Advantages of CE are high efficiency, low cost, short analysis time and simplicity, whereas disadvantages include low sensitivity comparing to HPLC and limitation of the preparative scale.