Flavonoid dimers from the total phenolic extract of Chinese dragon's blood, the red resin of Dracaena cochinchinensis.

Eight new flavonoid dimers, named cochinchinenins I-M (1-5), including three pairs of enantiomers (1a/1b-3a/3b) and two optically pure flavonoid dimers (4-5), along with a known analogue (6), were isolated from total phenolic extract of the red resin of Dracaena cochinchinensis (Chinese dragon's blood). The planar structures of 1-5 were elucidated by extensive spectroscopic analysis including HRESIMS and 1D/2D NMR. Their absolute configurations were determined on the basis of experimental and calculated electronic circular dichroism (ECD) data. Compounds 4 and 5 exhibited significant inhibition of nitric oxide production in lipopolysaccharide-stimulated BV-2 microglial cells with IC50 value of 4.9±0.4 and 5.4±0.6μM, respectively.