Tautomeric phytosterols from Vernonia amygdalina Delile and their anti-cervical cancer activity.

Vernonia amygdalina Delile is generally used as green vegetables for cuisine in Nigeria and health tea or products in southeast of china. It was also used as folk medicine for the treatment of anti-helminth, febrifuge, digestive tonic and wounds. In this study, eleven undescribed phytosterols (1-2, 4-12) and six known analogues (3, 13-17) were isolated from the stems of V. amygdalina. Their structures including absolute configurations were elucidated by comprehensive spectroscopic methods (1D and 2D NMR, HRESIMS), X-ray diffraction and comparison of their ECD spectra. Besides, the tautomerism of phytosterols (1, 3-6, 12-17) with hemiacetal moiety were analyzed by solution NMR with different deuterated solvent and variable-temperature experiments. In addition, the cytotoxic activities of isolates against HeLa cells were evaluated. As a result, compound 10 exhibited the most potent anti-cervical cancer activity with the IC50 of 22.44 µM. Mechanism studies indicated that 10 triggered HeLa cells apoptosis through activating caspase signaling pathway. Furthermore, 10 could arrest the cell cycle in S phase and suppress the activation of the PI3K/AKT/mTOR pathway, leading to the inhibition of HeLa cells proliferation.

[Lignans from Agrimonia pilosa].

Thirteen lignans were isolated from 60% ethanol extract of Agrimonia pilosa by column chromatography over silica gel, ODS, and MCI and preparative high performance liquid chromatography(HPLC). Their chemical structures were identified by physiochemical properties and spectral data as(7S,8S)-threo-4,7,9,9'-tetrahydroxy-3,3',5'-trimethoxy-8-O-4'-neolignan(1),(+)-4,9,9'-trihydroxy-3-methoxy-3',7-epoxy-8,4'-oxyneolignan(2), dihydrodehydro-diconiferyl alcohol(3), 4,9,9'-trihydroxy-3,3',5-trimethoxy-4',7-epoxy-8,5'-neolignan(4),(-)-secoisolariciresinol(5), 4,7,9,9'-tetrahydroxy-3,3',5'-trimethoxy-8-O-4'-neolignan(6),(+)-isolariciresinol(7), 4,7,9,9'-tetrahydroxy-3,3'-dimethoxy-8-O-4'-neolignan(8), burselignan(9),(-)-evofolin B(10), icariol A2(11), ciwujiatone(12), and(+)-4″,4-dihydroxy-3,3',3″,3,5,5'-hexamethoxy-7,9';7',9-diepoxy-4,8″;4',8-bisoxy-8,8'-dineolignan-7″,7,9″,9-tetraol(13). Compound 1 was a new compound, and compounds 1-13 were isolated from Agrimonia plant for the first time. This study can enrich the chemical components in A. pilosa and provide material conditions for the follow-up study of its biological activity and the elucidation of its pharmacodynamic substances.

Inhibitory effects of phenolic glycosides from Trollius chinensis Bunge on α-glucosidase: inhibition kinetics and mechanisms.

Two undescribed phenolic glycosides, trochinenols B and C (1 and2), together with four known analogues (3-6), were isolated from the functional tea Trollius chinensis Bunge and their α-glucosidase inhibitory kinetics and mechanisms were investigated. It was found that 1 inhibited α-glucosidase in a noncompetitive manner with an IC50 value of 25.96 µM, while 3 showed a notable inhibitory effect against α-glucosidase in an uncompetitive manner with an IC50 value of 3.14 µM. Analysis of synchronous fluorescence and circular dichroism spectroscopy indicated that the binding of 1 to α-glucosidase led to the rearrangement and conformational alteration of the α-glucosidase enzyme. Furthermore, molecular docking indicated that 1 had a high affinity close to the active site pocket of α-glucosidase and indirectly inhibited the catalytic activity of the enzyme. However, 3 was bound to the entrance part of the active center of α-glucosidase and could hinder the release of the substrate as well as the catalytic reaction product, eventually suppressing the catalytic activity of α-glucosidase.