Eudesmane sesquiterpenoid glycosides from the leaves of Pittosporum lenticellatum with anti-neuroinflammatory activity

Chemical investigation of the EtOAc extract of the leaves of Pittosporum lenticellatum led to the isolation of twenty-five previously undescribed eudesmane sesquiterpenoid glycosides, pitlencosides A－Y (1-25); their structures were elucidated by extensive spectroscopic analysis, including 1D and 2D NMR, HR-ESI-MS, ECD spectra, and X-ray crystallographic analysis. Among them, compounds 4, 5, 7, 8, 15 and 16 exhibited significant inhibitory effects on the production of nitric oxide in lipopolysaccharide-induced BV-2 microglial cells by suppressing the expression of inducible nitric oxide synthase and cyclooxygenase-2, with IC50 values ranging from 7.95 to 25.88 μM, which showed stereo-chemical and substituent dependents. Western blot analysis and molecular docking simulation confirmed the anti-inflammatory activity of compounds 4, 5, 7, 8, 15 and 16.

Pitsubcosides A-L, highly esterified eudesmane sesquiterpenoid glycosides with antibacterial activity from Pittosporum subulisepalum and their mechanism

BACKGROUND

Plants from the genus Pittosporum are traditionally used as antibacterial, antifungal and antiviral agents. A bioassay evaluation of the extract of Pittosporum subulisepalum revealed antibacterial activity. This study focused on the discovery of the antibacterial metabolism in P. subulisepalum, as well as the modes of action of its active components.

RESULTS

A chemical investigation of an ethyl acetate (EtOAc) extract of the aerial parts of P. subulisepalum led to the isolation of 12 previously undescribed eudesmane sesquiterpenoid glycoside esters (ESGEs), pitsubcosides A-L (1-12). Their structures were elucidated by extensive spectroscopic analysis, including one- and two-dimensional NMR, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism spectra and single-crystal X-ray crystallography analysis or by comparing with authentic samples. The new ESGEs were characterized by their highly esterified glycoside moieties. Among them, compounds 1-3, 5 and 8 showed a moderate inhibitory effect against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Bacillus cereus, Bacillus subtilis, Pseudomonas syringae pv. actinidiae (Psa) and Erwinia carotovora with minimum inhibitory concentrations (MICs) ranging from 3.13 to 100 μm. Among them, compounds 3 and 5 showed remarkable antibacterial activity against S. aureus and Psa with MIC values of 6.25 and 3.13 μm, respectively. Live bacterial mass and the biofilms of S. aureus and Psa were quantified using methyl tetrazolium and crystal violet assays. Fluorescence microscopy and scanning electron microscopy experiments revealed an antibacterial mechanism of cell membrane architectural disruption.

CONCLUSION

The results suggest that ESGEs possess great potential for the development of antibacterial agents to control plant pathogens. © 2023 Society of Chemical Industry.

Further sesquiterpenoids from Pittosporum qinlingense and their anti-inflammatory activity

Four new sesquiterpenoid glycoside esters, Pitqinlingoside N-Q (1-4), together with eleven known metabolites (5-15), were isolated from 95% EtOH extract of the twigs, fruits and leaves of P. qinlingense. The structures of new compounds were elucidated on the basis of extensive spectroscopic analyses, including IR, UV, HRMS, NMR and electronic circular dichroism spectra. Unusal glycoside esters are characterized by the presence of polyacylated β-D-fucopyranosyl and β-d-glucopyranosyl units. Pitqinlingoside N (1), O (2), P (3), boscialin (5) and arvoside C (6) showed significant nitric oxide production inhibition in lipopolysaccharide (LPS)-induced BV-2 microglial cells with IC₅₀ values ranging from 1.58 to 28.74 μM. Structure-activity relationships of the isolated compounds are discussed.

Structurally Diverse Sesquiterpenoid Glycoside Esters from Pittosporum qinlingense with Anti-neuroinflammatory Activity

Thirteen new sesquiterpenoid glycoside esters, including 11 aromadendrane-type compounds, pitqinlingosides A-K (1-11), one cadinane-type compound, pitqinlingoside L (12), and one eudesmane-type compound, pitqinlingoside M (13), together with seven known analogues (14-20) were isolated from the twigs, fruits, and leaves of Pittosporum qinlingense. Structures were elucidated by analysis of spectroscopic data, gas chromatography mass spectrometry (GC-MS), and chemical methods. The absolute configuration was confirmed by single-crystal X-ray crystallography analysis or electronic circular dichroism spectra. Unusual glycoside esters are characterized by the presence of polyacylated β-d-fucopyranosyl, β-d-glucopyranosyl, and β-d-xylopyranosyl units. Pitqinlingosides A (1), B (2), D (4), and F (6), pittosporanoside A₁ acetate (14), and pittosporanoside A₁ (16) showed significant nitric oxide production inhibition in lipopolysaccharide (LPS)-induced BV-2 microglial cells with IC₅₀ values ranging from 0.95 to 24.12 μM. Structure-activity relationships of the isolated compounds are discussed.

Structure and cytotoxic activity of sesquiterpene glycoside esters from Calendula officinalis L.: Studies on the conformation of viridiflorol

Topic applications of Calendula officinalis L. lipophilic extracts are used in phytotherapy to relieve skin inflammatory conditions whereas infusions are used as a remedy for gastric complaints. Such a different usage might be explained by some cytotoxicity of lipophilic extracts at gastric level but little is known about this. Therefore, we screened the CH2Cl2 extract from the flowers of C. officinalis by MTT and LDH assays in human epithelial gastric cells AGS. This bioassay-oriented approach led to the isolation of several sesquiterpene glycosides which were structurally characterized by spectroscopic measurements, chemical reactions and MM calculations. The conformational preferences of viridiflorol fucoside were established and a previously assigned stereochemistry was revised. The compounds 1a, 2a and 3f showed comparably high cytotoxicity in the MTT assays, whereas the effect on LDH release was lower. Our study provides new insights on the composition of C. officinalis extracts of medium polarity and identifies the main compounds that could be responsible for cytotoxic effects at gastric level.