Eight new arnebinol B-based meroterpenoids with planar chirality in the constrained 6/10/5 tricyclic skeleton from Arnebia euchroma and their cytotoxicities.

Eight new arnebinol B-based meroterpenoids ((-)-1, 2, 3, (-)-5, and 7-10) with a constrained 6/10/5 tricyclic backbone were isolated from the roots of Arnebia euchroma. The planar and steric structures of these new compounds were unambiguously elucidated by extensive spectroscopic analyses, X-ray diffraction crystallography, and ECD calculations. The predominant relative orientation between H-7 and the Z double bond with a methyl substituent in the rigid 10-membered carbocycle, along with the planar chirality of the Z double bond was analyzed and discussed for the first time. The illustration of the planar chirality derived from the Z double bond should be paid great importance during the structure elucidation on these homologous meroterpenoids. All the isolated meroterpenoids were screened for their cytotoxicities against the HCT-8, PANC-1, HGC-27, HepG2, and PC9 cell lines, and compounds (+)-5 and (-)-5 exhibited the most potent cytotoxicity.

Photoinduced Irreversible Intramolecular Proton Transfer of Arnebinones B, D, and E: The Case of Photoenolization at the p-Benzoquinone-CH2/CH-π System.

Arnebinones B, E, and D (1-3) have been found to be sensitive to light, generating complex and diverse proton transfer products when triggered by light. A unique two-step irreversible intramolecular proton transfer of 1 produced five scalemic mixtures, of which four possessed intriguing dual planar chirality. The unprecedented orientation epimerization equilibrium of the intra-annular double bond was first observed and researched in the homologous meroterpenoids by HPLC monitoring and DFT calculations. A "p-benzoquinone-CH2/CH-π" moiety in the structure was the common key feature for the occurrence of this type of photoenolization reaction. The product transformation processes and universality of this photoinduced irreversible proton transfer reaction were analyzed together with the cytotoxic activities of arnebinones B, D, and E, and their photoreaction products.

Neophathalides A and B, two pairs of unusual phthalide analog enantiomers from Ligusticum chuanxiong.

Two pairs of unusual phthalide analog enantiomers, (+)- and (-)-neophathalides A and B [(+)- and (-)-1 and 2], were isolated from the rhizome of Ligusticum chuanxiong Hort. Notably, neophathalide A presented a novel spiro-[4.5]dec-6-ene skeleton that originated from an aldol condensation process from sedanonic acid. Neophathalide B is an unprecedented 3-substituted phthalide analog that possesses a four-membered lactone ring system. The structures of the compounds were established using UV, IR, HRESIMS, NMR and ECD methods. All of the compounds were evaluated for their hepatoprotective activity against N-acetyl-p-aminophenol-induced HepG2 cell injury. Compounds 1a, 1b, and 2a exhibited moderate hepatoprotective activity compared with the positive control drug bicyclol at a concentration of 10 µM (p < 0.01).

Archromones A-F, unusual polycyclic dearomatic geranylquinol derivatives from the roots of Arnebia euchroma.

Eight new geranylquinol derivatives (1-8) were purified from the roots of Arnebia euchroma. Compounds 1-6 possess an unprecedented dearomatic benzocogeijerene skeleton with a rare trans-fused hydronaphthalene moiety. Their structures and absolute configurations were elucidated by HRESIMS, NMR, ECD, and X-ray diffraction. A convenient strategy for rapid determination of the relative configuration of H-1/H-7/Me-16 and the absolute configuration at C-1 for 1-6 was summarized. Compound 2 exhibited cytotoxicity against all the tested cell lines, namely PC9, BGC823, HCT116, HepG2, HeLa, and U87-MG, with IC50 values ranging from 13.7 to 29.3 µM.

Eight new biflavonoids with lavandulyl units from the roots of Sophora flavescens and their inhibitory effect on PTP1B.

In the course of studying the components from the roots of Sophora flavescens, eight new unusual biflavonoids consisting of a flavanone fused with a dihydrochalcone skeleton were isolated. These new chemical structures were elucidated by means of UV, IR, HRESIMS, NMR and ECD spectroscopic data and a comparison of experimental ECD spectra with calculated ECD spectra. Some compounds were subjected to an antidiabetic bioassay on human recombinant PTP1B inhibition, and showed strong inhibitory activity.

An ingenious method for the determination of the relative and absolute configurations of compounds containing aryl-glycerol fragments by 1H NMR spectroscopy.

A concise method was established to determine the relative and absolute configurations of aryl-glycerols that depend on the chemical shift differences (Δδ) of the diastereotopic methylene protons (H-3) by 1H NMR spectroscopy. When using DMSO-d 6 as the preferred solvent, the threo configuration corresponded to a larger Δδ H3a-H3b value (>0.15 ppm), whereas the erythro configuration (<0.07 ppm) corresponded to a smaller value. Furthermore, the absolute configurations were determined with the aid of a simple acylation reaction through camphanoyl chloride. In the threo enantiomers, the Δδ value of the 1R,2R configuration was <0.15 ppm, and that of the 1S,2S configuration was >0.20 ppm. In the erythro enantiomers, the Δδ value of 1R,2S was >0.09 ppm, and that of 1S,2R was <0.05 ppm. Remarkably, this empirical rule is invalid in CDCl3. In addition, this method was also verified by a quantum 1H NMR calculation.