ent-Clerodane diterpenoids from the stems of Croton krabas.

The first phytochemical investigation from the stems of Croton krabas resulted in the isolation of three new ent-clerodane diterpenoids, crotonkrabases A-C (1-3), along with two known compounds, 12-oxohardwickiic acid (4) and crotonpyrone B (5). Their structures were elucidated using extensive spectroscopic methods. The structure of 3 was unambiguously proven by X-ray crystallography. Furthermore, the absolute configurations of compounds 1-3 were identified by NOESY and the comparison of their experimental ECD spectra with those of calculated ECD spectra reported in the literature. Compounds 1, 2, and 5 showed antibacterial activities against two Gram-positive bacteria (Bacillus cereus and Bacillus subtilis); whereas compound 4 exhibited weak antibacterial against B. cereus. In addition, compound 4 showed potent α-glucosidase inhibitory activity, which was lower than the reference standard acarbose.

A new cytotoxic plumbagin derivative from roots of Diospyros undulata.

A new plumbagin derivative, 3-(5-oxohexyl)plumbagin (1), together with six known benzoquinone derivatives (2-7), four known triterpenoids (8-11) and coniferyl aldehyde (12) were isolated from Diospyros undulata roots. Their structures were elucidated by intensive spectroscopy including 1 D and 2 D NMR, UV, IR and MS spectrometric analysis. Compound 1 exhibited strong cytotoxicity against three cancer cell lines as lung cancer (NCI-H187), breast cancer (MCF-7), and oral cancer (KB) with IC50 values of 7.16, 12.85 and 28.67 µM, respectively. Moreover, it did not showed cytotoxicity to Vero cells. In addition, the antimicrobial activity of compound 1 was moderate that kill only S. aureus with MBC of 250 µg/mL while other compounds especially compound 4 showed a broader activity that kill all tested bacteria.

Phytochemical investigation and acetylcholinesterase inhibitory activity of bark of Hymenodictyon orixense.

The chemical investigation of the methanol extract of Hymenodictyon orixense bark, a Thai medicinal herb, provided five compounds. Their structures were identified on the basis of 1D NMR and MS data, as well as by comparison of the data with published values, as an iridoid glycoside: loganin (1), four coumarins: scopoletin (2), scopolin (3), hymexelsin (4) and scopoletin 7-O-ß-D-xylopyranosyl-(1→6)-ß-D-glucopyranoside (5). Compounds 1-5 showed acetylcholinesterase (AChE) inhibitory activity in the range of 13.92-34.18% at a concentration of 100 µg/mL. In addition, compounds 1 and 5 are reported for the first time from this genus.