Coumarin-monoterpenes from Gerbera anandria (Linn.) Sch.-Bip and their neuroprotective activity

Four new glycosides isolated from Gerbera delavayi Franch

Phytochemical investigation of the whole plant of Gerbera delavayi afforded four new glycosides including three coumarin glycosides, Gerbelavinside A (1), Gerbelavinside B (2) and Gerbelavinside C (3) and one acetophenone glycoside, Gerbelavinside F (4). The structures of isolated compounds were elucidated by analysis of 1D and 2D NMR, HR-ESI-MS, acid hydrolysis, as well as comparing with the literature. The isolated compounds were examined the effects of nitric oxide (NO) production inhibition in lipopolysaccharide (LPS)-induced RAW264.7 macrophage cells, and Gerbelavinside C presented a certain inhibitory activity.

New 5-methyl-4-hydroxycoumarin polyketide derivatives from Gerbera delavayi with anti-inflammatory activity

Five new 5-methyl-4-hydroxycoumarin polyketide derivatives (MPDs), delavayicoumarins A-E (1-5), were isolated from the whole plants of Gerbera delavayi. Among them, compounds 1-3 are the common monoterpene polyketide coumarins (MPCs), while 4 is a modified MPC with both the lactone ring contracted to a five-membered furan ring and a carboxyl at C-3, and 5 is a pair of unusual phenylpropanoid polyketide coumarin enantiomers (5a and 5b), featuring a phenylpropanoid unit at C-3. The planar structures were elucidated by spectroscopic methods and biosynthetic arguments, and the absolute configurations of 1-3, 5a and 5b were confirmed by calculated electronic circular dichroism (ECD) experiment. Furthermore, compounds 1-3, (+)-5 and (-)-5 were tested for the nitric oxide (NO) inhibitory activity by using lipopolysaccharide (LPS)-induced RAW 264.7 cells in vitro. The results showed that compounds 1-3, (+)-5 and (-)-5 remarkably inhibited NO production at the concentration of 10.0 μM, exhibiting that they have significant anti-inflammatory activity.

1H-NMR-guided isolation of enantiomeric coumarin-monoterpenes with anti-inflammatory activity from Gerbera piloselloides

¹H-NMR guided fractionation led to the isolation of twenty-two coumarin monoterpenes from the whole plant of Gerbera piloselloides, among which fourteen were undescribed. All coumarin monoterpenes were initially found to be racemates without optical activity. Subsequently, eleven pairs of optically pure enantiomers were successfully separated by chiral phase HPLC. Their structures and absolute configurations were unambiguously determined based on their spectroscopic data, calculated/experimental electronic circular dichroism (ECD) data, and X-ray diffraction analysis. Bioassays in LPS-treated RAW 264.7 cells revealed that the four compounds possessed moderate anti-inflammatory activity. In addition, the correlations between the cotton effect (CE) from δ-lactone at approximately 210-220 nm in CD spectra and γ-C or the ring fused at γ-C of the skeleton were reported for the first time.

Highly Oxidized Germacranolides from Elephantopus tomentosus and the Configurational Revision of Some Previously Reported Analogues

Highly oxidized germacranolides are mainly found in the genus Elephantopus, contain a characteristic ten-membered molecular core that is highly flexible, and exhibit potential cytotoxic properties. However, their configurations were assigned ambiguously in previous reports due to spectroscopic observation of macrocyclic systems. Herein, 17 highly oxidized germacranolides, including 12 new germacranolides (1-12), were isolated from Elephantopus tomentosus. Their structures were characterized by spectroscopic data analysis combined with X-ray crystallography and ECD calculations, and it was possible to propose configurational revisions of five previously reported analogues (13-17). Cytotoxic activities for 1-17 against two hepatocellular carcinoma cell lines (HepG2 and Hep3B) were tested, and compounds 1-10 and 13-16 generated IC₅₀ values of 2.2-9.8 μM. Furthermore, the observed cytotoxic activity of 1 was determined as being mediated by inducing the apoptosis of HepG2 and Hep3B cells via mitochondrial dysfunction.

Bioactive constituents from Gerbera piloselloides with anti-inflammatory and antiproliferative activities

A phytochemical investigation of the 95% ethanol extract from Gerbera piloselloides obtained fourteen compounds, including three undescribed phenone-monoterpenes (1a/1b and 2), seven undescribed chromone-monoterpenes (3a/3b-5a/5b and 6), and one undescribed coumarin-monoterpene (8). Among them, four pairs of enantiomers (1a/1b and 3a/3b-5a/5b) were successfully isolated by the chiral-phase HPLC resolution. The structures and absolute configurations were unambiguously determined based on comprehensive spectroscopic data, electronic circular dichroism (ECD) data, and X-ray diffraction analysis. Structurally, compound 1 is the first 5-methylphenone monoterpene formed through a circular 6-membered carbocycle. And their anti-inflammatory and antiproliferative activities were evaluated via LPS stimulated RAW 264.7 cells and five human cancer lines (HepG2, MDA-MB-231, SCG-7901, A549 and MCF-7), respectively. Compounds 4b, 5a and 5b showed moderate inhibitory effect against nitric oxide (NO) production with IC₅₀ values ranging from 12.52 to 15.75 μM. Compound 8 significantly inhibited the proliferation of MDA-MB-231 human cancer line in a dose-dependent manner. Furthermore, the connection between phenone-monoterpenes, chromone-monoterpenes, and coumarin-monoterpenes in biosynthesis were also discussed.