5-epi-ent-Kaurane diterpenoids from the aerial parts of Isodon eriocalyx and their anti-atherosclerotic potential

The phytochemical investigation of the EtOAc extract from the aerial parts of Isodon eriocalyx afforded seventeen diterpenoids , including eight undescribed compounds. Eriocalyxins H?L have unique structural characteristics featuring a 5- epi - ent -kaurane diterpenoid scaffold with eriocalyxins H–K also possess an unusual 6,11-epoxyspiro-lactone ring while eriocalyxin L, a 1,7:3,20-diepoxy- ent kaurene, features an 1 ,7-oxygen linkage. The structures of these compounds were elucidated by spectroscopic data interpretation, and the absolute configurations of eriocalyxins H, I, L, and M were confirmed by single-crystal X-ray diffraction. The isolates were screened for their inhibitory activities against VCAM-1 and ICAM-1 at 5?μM. While eriocalyxin O, coetsoidin A and laxiflorin P were found to significantly inhibit both VCAM-1 and ICAM-1, 8 (17),13- ent -labdadien-15?→?16-lactone-19-oic acid displayed evidently inhibitory effect against ICAM-1.