Picpuranes A-E, structurally diverse diterpenoids from Picea purpurea

Phytochemical investigation on the cones of Picea purpurea led to the isolation of four previously undescribed abietane diterpenoids ( 1 – 4 ) and one new isopimarane diterpenoid ( 5 ), alongside 23 known abietane analogues ( 6 – 28 ). Compounds 1 and 2 represent two unusual 19- nor -abietanes, while 3 features a rare naturally occurring 13,14- seco -abietane skeleton. Their structures were established by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. All isolates were evaluated for the inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. The results showed that 1 and 2 exhibited moderate inhibition of NO production.