Immunosuppressive leucosesterterpane and penta-nor-leucosesterterpane sesterterpenoids from Leucosceptrum canum.

Five undescribed leucosesterterpane sesterterpenoids, leucosceptrines A-E, two undescribed penta-nor-leucosesterterpane (C20) sesterterpenoids, nor-leucosceptrines A and B, and three known analogues, were obtained from the aerial parts of Leucosceptrum canum of Chinese origin. Leucosceptrines A-C are the first examples of leucosesterterpane-type sesterterpenoids with unclosed dihydropyran rings and reverse configurations at chiral centers C-4 and/or C-12. Nor-leucosceptrines A and B possesses an unusual penta-nor-leucosesterterpane skeleton. Their structures were unambiguously elucidated through comprehensive spectroscopic analyses and single-crystal X-ray diffraction. A plausible biogenetic pathway for these sesterterpenoids was proposed. The immunosuppressive effects of these isolates on the secretion of the cytokine IFN-γ by T cells stimulated with anti-CD3/CD28 monoclonal antibodies were observed with different potencies.

Labdane diterpenoids from the heartwood of Leucosceptrum canum that impact on root growth and seed germination of Arabidopsis thaliana.

Eleven undescribed diterpenoids possessing labdane, 3,18-cyclo-labdane, 19 (4 â†’ 3)-labdane and 12-nor-labdane skeletons, named leucolactones A-K, were isolated from the heartwood of a large woody Lamiaceae plant, Leucosceptrum canum. Their structures were determined by NMR, MS, and in the case of leucolactones A by single crystal X-ray diffraction analysis. Plausible biosynthetic pathway of leucolactones were proposed. Leucolactones showed significant inhibitory effects against seed germination and root elongation of Arabidopsis thaliana in the Petri dish bioassay. Among them, the diastereomeric leucolactones G and H were the most potent, with EC50 values for root elongation of 6.53 ± 1.35 and 9.75 ± 1.25 µM, respectively. The preliminary structure-activity relationship of leucolactones was discussed. The increase of auxin reporter activity in A. thaliana DR5::GUS roots by leucolactone H was observed, indicating that leucolactones altered auxin accumulation and distribution. These findings suggested that leucolactones might be involved in regulation of plant growth and development through altering auxin accumulation and distribution, presumably contributing to the heartwood formation in L. canum.

[Concentration, profile distribution and source identification of PCDD/Fs in environmental medium around a HSWI].

The concentration and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the environmental air, soil and plant samples around a hospital solid waste incinerator (HSWI) in Northwest of China were determined by HRGC/HRMS, and the flue gas samples of the HSWI were also involved. The results showed that the average concentration (I-TEQ) of PCDD/Fs in the exhaust gas was 184 ng x m(-3), which seriously exceeds the emission standard (0.5 ng x m(-3)). And the average concentration of PCDD/ Fs was 7.30 pg x m(-3) in the ambient air samples, 52.5 pg x g(-1) in the soil samples, and 146 pg x g(-1) in the leaves samples. All of them were at quite high levels. The concentrations of PCDD/Fs in air samples of downwind were obviously higher than those of upwind. The concentration increased and then decreased with the increase of distance from the HSWI, and the highest concentration occurred at the distance of 700 m from the HSWI. The mass concentration (I-TEQ) proportional distributions of 2, 3, 7, 8 substitution toxic dioxins in downwind air and soil samples was similar to those in the exhaust gas samples. The analysis results of PCDD/Fs concentrations, profiles distributions and principal components all showed that the major source of PCDD/Fs in this area was from the HSWI flue gas emissions.