Hong Liang

Arnebidin, a heptacyclic naphthoquinone dimer with a tricyclo[3.3.0.0^1,3]octane core, which was first isolated from Arnebia hispidissima and later found from A. euchroma. Its structure was identified by the analysis of NMR and EI-MS data. In the present work, a heptacyclic naphthoquinone dimer ((±)-1) was obtained from the petroleum ether portion of the ethanol extract of Arnebia euchroma. By comparing the NMR data of 1 with the literatures, compound 1 should be identified as arnebidin. However, the single-crystal X-ray diffraction analysis followed by reinterpretation of the NMR data revealed that the structure of 1 was a heptacyclic naphthoquinone dimer with a tricyclo[3.2.1.0^2,7]octane core. Thus, we proposed that arnebidin should be revised to 1.

Four p-coumaroylated sesquiterpenoids (1–4), including three new ones (1, 2, and 4), were isolated from the whole plants of Pilea cavaleriei. Their structures were established on the basis of comprehensive spectroscopic analysis and comparison with data reported in the literature. Compounds 1–4 were evaluated for their antimycobacterial activities, and 2 and 4 were active against Mycobacterium tuberculosis H₃₇Rv with the MIC values of 19.6 ± 0.19 and 17.4 ± 0.12 μg/mL, respectively.