PPARα and γ Activation Effects of New Nor-triterpenoidal Saponins from the Aerial Parts of Anabasis articulata.

Anabasis articulata , traditionally used to treat diabetes, is rich in saponin content. This study was performed to investigate the agonistic effect of its saponins on peroxisome proliferator-activated receptor- α and peroxisome proliferator-activated receptor- γ in human hepatoma (HepG2) cells to explore the possibility of the involvement of these nuclear receptors in the mechanism of the antidiabetic effect of the plant. Chemical investigation of the n -butanol fraction resulted in the isolation of three new and one known 30-noroleanane triterpenoid saponins. The structures of the new compounds were elucidated as 3 β -hydroxy,23-aldehyde-30-norolean-12,20(29)-dien-28-oic acid-28- O - β -D-glucopyranosyl ester (1: ), 3 β - O -D-galactopyranosyl-23-aldehyde-30-norolean-12,20(29)-dien-28-oic acid-28- O - β -D-glucopyranosyl ester (2: ), and 3 β - O -D-xylopyranosyl-30-norolean-12,20(29)-dien-28-oic acid 28- O - β -D-glucopyranosyl ester (3: ), while the known 30-nortriterpenoidal saponin was identified as boussingoside E (4: ). Although, the isolated saponins (1:  - 4: ) did not show > 1.5-fold activation of peroxisome proliferator-activated receptor- γ , but two of them (1: and 3: ) activated peroxisome proliferator-activated receptor- α to the higher extents of 2.25- and 1.86-fold, respectively. These results suggest that the reported antidiabetic action of the isolated saponins may not solely involve the activation of peroxisome proliferator-activated receptor- γ . However, the agonistic activity of the n -butanol fraction of A. articulata (1.71-fold induction) and two of its saponins (1: and 3: ) towards peroxisome proliferator-activated receptor- α may be beneficial in the cardiovascular condition that is closely associated with diabetes and other metabolic disorders.