Neuroinflammatory inhibitors from Gardneria nutans Siebold & Zuccarini

Two new monoterpene indole alkaloid glycosides nutanoside A-B (1-2), two new phenolic glycoside esters nutanester A-B (6-7), together with five known compounds (3-5, 8-9) were isolated from the ethanol extract of Gardneria nutans Siebold & Zuccarini. Their structures were established on the basis of extensive spectroscopic analysis and TDDFT/ECD calculations. Compounds 1 and 2 are two rare monoterpene indole alkaloids with the glucosyl moiety located at C-12 and represent the first two examples of enantiomer of ajmaline type monoterpene indole alkaloids. Compounds 3, 4 and 6 displayed significant inhibitory effects on NO production in over-activated BV2 microglial cells, with the IC₅₀ values of 2.29, 6.36, and 8.78 μM, respectively. Compounds 1, 5, 7 could significantly inhibit the mRNA expression of inflammatory factors TNF-α and IL-6 induced by LPS in BV2 microglial cells at the effective concentration. Moreover, compound 3 exhibited stronger cytotoxicities against U87 and HCT116 cell lines than taxol with IC₅₀ values of 10.58 and 14.60 μM, respectively.