Three unprecedented thioether-linked dimeric pyrimidines isolated from the medicinal-edible herb Ligusticum striatum DC.

Three unprecedented thioether-linked dimeric pyrimidines, namely ligusticumines A-C, together with twelve known compounds were isolated and identified from the traditional Chinese medicinal-edible herb, Ligusticum striatum DC. The structures of all the isolated compounds were determined from NMR, HRESIMS and X-ray diffraction spectroscopies. Additionally, a novel 3-step synthetic route was developed to synthesize ligusticumine C by substitution, thiolation and coupling, with an overall yield of 5.4%. The inhibitory activities of the isolated compounds against phosphatidylinositol 3-kinase (PI3K) were tested, of which, (3S)-butylphthalide, a characteristic component of L. striatum, showed a potent inhibitory effect on PI3Kα (IC50: 3.6 µg/mL).