Isolation and identification of polar auxin transport inhibitors from Saussurea costus and Atractylodes japonica

Abstract

An intensive survey of naturally-occurring regulators of polar auxin transport (PAT) was conducted in two oriental medicinal species from the Asteraceae, Saussurea costus and Atractylodes japonica, using the radish hypocotyl bioassay system and physicochemical analyses. Costunolide and santamarine were identified as well as dehydrocostus lactone from S. costus roots, and atractylenolide II and (+)-eudesma-4(14),7(11)-dien-8-one from Atractylodes japonica rhizomes as physiologically novel compounds possessing inhibitory activities of PAT. Costunolide and santamarine showed ca. 40% inhibition of PAT in the radish hypocotyl segments at a dose of 2.5 μg/plant and 1 μg/plant, respectively. Inhibitory effects of atractylenolide II and (+)-eudesma-4(14),7(11)-dien-8-one were ca. 10 times lower than those of costunolide and santamarine. Structure–activity relationships and possible mechanisms to inhibit PAT are also discussed.

Keywords

• atractylenolide II
• Atractylodes japonica
• polar auxin transport inhibitor
• costunolide
• eudesma-4(14),7(11)-dien-8-one
• santamarine
• Saussurea costus