Coronarin D, a Metabolite from the Wild Turmeric, Curcuma aromatica, Promotes the Differentiation of Neural Stem Cells into Astrocytes

Plants in the genus Curcuma have been widely used as traditional medicines in Asian countries. These plants contain bioactive compounds with neuroprotective properties or activities that increase neural stem cells (NSCs) and neurons. However, bioactive components in Curcuma that promote the differentiation of NSCs into astrocytes have not yet been reported. Here, the effects of Curcuma extracts on the in vitro differentiation of embryonic stem-cell-derived NSCs were evaluated. The extract of the wild turmeric, Curcuma aromatica, strongly promoted the differentiation of NSCs into astrocytes. Bioassay-guided isolation yielded coronarins C (1) and D (2), as well as (E)-labda-8(17),12-diene-15,16-dial (3) as the bioactive compounds. Coronarin D (2) markedly promoted the differentiation of NSCs into astrocytes up to approximately 4 times (3.64 ± 0.48) and increased the expression level of GFAP at the mRNA and protein level, while compounds 1 and 3 exhibited only weak effects, suggesting that the 15-hydroxy-Δ12-γ-lactone moiety is important for bioactivity. Moreover, compound 2 increased the number of pSTAT3-positive cells, suggesting that compound 2 promoted astrocytic differentiation through JAK/STAT signaling pathway.