Syringenes A–L: Bioactive dimeric eremophilane sesquiterpenoids from Syringa pinnatifolia

Novel lignans from Syringa pinnatifolia and protective effect against H2O2-induced oxidative injury through regulating the expression of Nrf2/HO-1 in H9c2 cells

Phytochemical analysis of the peeled stems of Syringa pinnatifolia Hemsl. led to the discovery of 13 undescribed lignans, namely helanols A and B (1 and 2) and alashanenols W-G1 (3-13), as well as four known analogues, of which helanols A and B were lignans with novel skeleton of α-β' linkage. The structures were unambiguously established by extensive spectroscopic analyses, NMR calculations, ECD calculations, and single crystal X-ray crystallography. Five lignans (1, 2, 5, 11 and 13) exhibited a moderate protective effect against H2O2-induced oxidative injuries in H9c2 cells with the protective rates of 11.3-20.6 % at the concentration of 0.3-20 μM, while the positive control quercetin showed protective rates of 58.7 % at 10 μM. Further mechanism investigation suggested that 1 and 2 exerted the protective effect by regulating the expression of Nrf2/HO-1.

Dimeric eremophilane-type sesquiterpenoids from the peeled stems of Syringa pinnatifolia

A continued phytochemical investigation guided by 1H NMR and LC-MS data on the ethanol extract from the peeled stems of Syringa pinnatifolia Hemsl. led to the isolation of 16 undescribed dimeric eremophilane sesquiterpenoids, namely syringenes R-Z (1-9) and A1-G1 (10-16). These structures were elucidated by extensive analysis of spectroscopic data, including HRESIMS, NMR, quantum-mechanics-based computational analysis of NMR chemical shifts, and single-crystal X-ray diffraction analyses, and a concise rule for determination of relative configuration of angular methyl was proposed. The results of the cardioprotective assay demonstrated that 3 exhibits a protective effect against hypoxia-induced injuries in H9c2 cells. This effect was observed at a concentration of 10 μM, with a protective rate of 28.43 ± 11.80%.

Alashanines A-C, Three Quinone-Terpenoid Alkaloids from Syringa pinnatifolia with Cytotoxic Potential by Activation of ERK

Three quinone-terpenoid alkaloids, alashanines A-C (1-3), possessing an unprecedented 6/6/6 tricyclic conjugated backbone and quinone-quinoline-fused characteristic, were isolated from the peeled stems of Syringa pinnatifolia. Their structures were elucidated by analysis of extensive spectroscopic data and quantum chemical calculations. A hypothesis of biosynthesis pathways for 1-3 was proposed on the basis of the potential precursor iridoid and benzoquinone. Compound 1 exhibited antibacterial activities against Bacillus subtilis and cytotoxicity against HepG2 and MCF-7 human cancer cell lines. The results of the cytotoxic mechanism revealed that compound 1 induced apoptosis of HepG2 cells through activation of ERK.

Diverse lignans with protective effect against hypoxia/oxidative injuries to H9c2 cells from Syringa pinnatifolia Hemsl

A bioactivity-guided fractionation on the phenolic fractions from the peeled stems of Syringa pinnatifolia Hemsl., one of representative Mongolian folk medicine in China, led to the isolation and structural determination of 11 undescribed lignans and 12 known ones. These lignans cover diverse types, among them syringanones A and B represent an unprecedented carbon skeleton (proposed syringanane) and alashanenol A possesses a rare bicyclo [3.3.1]nonadienemethanol core. Their structures were established by extensive spectroscopic data analysis, X-ray diffraction, and quantum chemical calculations. All isolates were evaluated for their cardioprotective activities on H9c2 cardiomyocytes in vitro. The results showed that five lignans exhibited the protective effects against hypoxia-induced injury at the concentrations of 1.2-40 μM and six lignans exhibited anti-oxidative stress injury at 10-40 μM. These findings account to some extend for the traditional therapeutic effects of S. pinnatifolia for the treatment of ischemic heart diseases in clinic.

Gender differences pharmacokinetics, bioavailability, hepatic metabolism and metabolism studies of Pinnatifolone A, a sesquiterpenoid compound, in rats by LC-MS/MS and UHPLC-Q-TOF-MS/MS

BACKGROUND

Pinnatifolone A is a typical sesquiterpenoid and the primary active ingredient of Syringa oblata Lindl., has potent anti-inflammatory activity. However, Pinnatifolone A pharmacokinetic and metabolites analysis investigations in male and female rats, as well as its in vitro stability in male and female rat liver microsomes, have not been evaluated and compared.

PURPOSE

To investigate preclinical pharmacokinetic and metabolite in both genders, confirm gender differences, and provide usable information for the development of clinical applications.

METHODS

A quick, precise, and sensitive LC-MS/MS method was created and effectively used to determine the pharmacokinetics of oral (140 mg/kg) and intravenous (6.3 mg/kg) Pinnatifolone A in male and female rats, in vitro Pinnatifolone A elimination studies in male and female rat liver microsomes. Following that, a UHPLC-Q-TOF-MS/MS technique was established to identify the metabolic profiles of Pinnatifolone A obtained from rat plasma and excreta.

RESULTS

In the current study, we established for the first time an LC-MS/MS method for the quantitation of Pinnatifolone A with acceptable linearity and selectivity, recovery and matrix effect, accuracy and precision. The absolute oral bioavailability of Pinnatifolone A was approximately 30.36% in female rats, the clearance (CL) was 20.99±3.33 l/h/kg in female rats and 472.37±437.31 l/h/kg in male rats. This difference in rat genders may pertain to the sex-specific expression of hepatic enzymes as demonstrated in the metabolic stability evaluation in the present research; the male rats exhibited higher CL_int(mic) (158.83±9.57 μl/min/mg protein) than female rats (76.47±7.90 μl/min/mg protein) liver microsomes, indicating higher Pinnatifolone A clearance in male rats. Twenty-four metabolites were detected and identified in female and male rats; N-acetylcysteine conjugation metabolite was the most abundant metabolites in both rat feces and urine. Furthermore, male and female rats had significantly different levels of the N-acetylcysteine conjugation metabolite. Hydrogenation metabolite was particular to female rats both in rat fecal and urine. Glucuronide conjugation metabolite was the predominant metabolite in rat plasma, and its amount in female rats was double that of male rats.

CONCLUSIONS

The present research is the first to report the preclinical pharmacokinetics and metabolites of Pinnatifolone A in male and female rats, confirming the gender-based differences. The findings provide a comprehensive overview for further understanding of the pharmacokinetic and metabolic characteristics of Pinnatifolone A and serve as a guide for its future development and utilization.

Syringenes M - Q, Eremophilane Sesquiterpenoid Dimers from the Peeled Stems of Syringa pinnatifolia

As a part of systematic studies on Syringa pinnatifolia, a continued phytochemical investigation guided by ¹ H-NMR and LC/MS data on the ethanol extract afforded five new dimeric eremophilane sesquiterpenoids, namely syringenes M-Q (1-5). These structures were elucidated by extensive analysis of spectroscopic data, including infrared (IR), high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), nuclear magnetic resonance (NMR), quantum-mechanics-based computational analysis of NMR chemical shifts, and single-crystal X-ray diffraction. Compounds 4 and 5 showed inhibitory activities against NO production induced by lipopolysaccharide in RAW264.7 macrophage cells, with IC₅₀ values of 5.1 and 9.3 μM, compared to positive control indomethacin (IC₅₀ 33.6 μM). These dimeric eremophilane sesquiterpenoids may be potential markers for discriminating this species from the genus Syringa and the Oleaceae family.