Two new ent-labdane diterpenoids, hypoestesins A-B (1-2) and five new labdane diterpenoids, hypopurolides H-L (3-7), were isolated from the aerial parts of Hypoestes purpurea. All of the structures were fully determined based on extensive analysis of 1H, 13C, 2D NMR, and HRESIMS data. The absolute configurations of 1-3 was established through comparing the experimental and calculated ECD curves and the structure of 5 was confirmed by single crystal X-ray diffraction experiment. Compounds 5-7 were unusual C23 labdane diterpenoids having a γ-acetonyl-α, β-unsaturated γ-lactone unit and each assigned as C-15 epimeric mixture. Furthermore, cytotoxic and anti-inflammatory activities of 3-7 were evaluated. The results showed that 3 had remarkable cytotoxic activity against HL-60, A549, SMMC-7721, MDA-MB-231, and SW480 cancer cell lines with IC50 values ranging from 2.35 to 17.06 μM. Compound 4 showed moderate cytotoxic activity against HL-60 and SMMC-7721 cancer cell lines with IC50 values of 15.12 ± 0.53 and 12.92 ± 0.60 μM, respectively. Furthermore, compound 4 was also found to exhibit inhibitory activity against NO production in RAW 264.7 macrophages with IC50 values of 23.56 ± 0.99 μM, compared to the positive control L-NMMA with an IC50 value of 41.11 ± 1.34 μM.

Seven new labdane diterpenoids, hypopurolides A-G (1-7) were discovered from the aerial part of Hypoestes purpurea, along with one known analog, hypopurin D (8). The structures of 1-7 were characterized based on 1 H-, 13 C-, and 2D-NMR, and HR-ESI-MS spectra. The absolute configurations of 1-7 were defined by single-crystal X-ray diffraction and electronic circular dichroism (ECD) data. Compounds 1-8 were tested for their nitric oxide (NO) inhibitory and cytotoxic effects. Compound 6 displayed moderate inhibitory effect toward LPS-induced NO release in RAW 264.7 cells with an IC50 value of 41.50 μM.