Five selaginellin derivatives, including two new selaginellins termed selaginellins M (1) and N (2), and three previously identified compounds, selaginellin (3), selaginellin A (4), and selaginellin C (5), were isolated from the Selaginella tamariscina (Beauv.) Spring plant. In addition, four known biflavonoids, namely neocryptomerin ( 6), hinokiflavone (7), pulvinatabiflavone (8), and 7''- O-methylamentoflavone (9), were also isolated. The structures of new compounds 1 and 2 were elucidated by spectroscopic analysis. The cytotoxic activity of compounds 1- 9 was evaluated against a small panel of human cancer cell lines, including U251 (human glioma cells), HeLa (human cervical carcinoma cells), and MCF-7 (human breast cancer cells). The two new selaginellins, selaginellins M (1) and N (2), showed medium activity against the human cancer cell lines.

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Ternary nitride semiconductors with tunable electronic structure and charge transport properties have attracted increasing attention as optoelectronic materials. The recently discovered ternary MgTMN2 (TM=Ti,Zr,Hf) are predicted to be nondegenerate semiconductors with visible-range optical absorption onsets. In the present study, the electronic structure, elastic properties, optical absorption spectrum, and dynamic stability of the MgTMN2 system have been systematically studied by first-principles calculations based on the density functional theory. These compounds show semiconductor characteristics with a bandgap ranging from 1.0 to 1.5 eV predicted by the Heyd–Scuseria–Ernzerhof approach. Compared to the traditional semiconductors of Si and GaAs and III–V nitrides of GaN and AlN, these ternary nitrides have stronger resistance to external compression, shear strain, and deformation due to the larger elastic modulus. MgTiN2 shows a strong anisotropy characteristic along the xy plane and z axis, while for MgZrN2 and MgHfN2, a weak elastic anisotropy is predicted. The absorption regions of these compounds are mainly concentrated in the ultraviolet region, and MgTiN2 is more sensitive to visible light with respect to the other two compounds. The thermodynamic stability of MgTiN2, MgZrN2, and MgHfN2 is verified by the stable phonon dispersion relations. It is found that the most stable low Miller index surface is (110) for MgTiN2 and (100) for MgZrN2 and MgHfN2.

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