Licorice-derived compounds inhibit linoleic acid (C:18:2 omega 6) desaturation in soybean chloroplasts

Although glycyrrhizic acid, a major constituent of licorice root, has important pharmacological effects in humans, the biological activity of glycyrrhizic acid and its aglycone glycyrrhetinic acid in plants is unknown. Here we report that these licorice-derived compounds and the analog carbenoxolone inhibit desaturation of linoleic acid (C18:2 omega 6) in soybean chloroplasts using monogalactosyldiacylglycerol and phosphatidylcholine substrates in an in vitro assay for desaturase activity. At 10 nM glycyrrhetinic acid, there is significant inhibition of desaturation of linoleic acid suggesting that licorice-derived compounds could prove useful in investigating biochemical pathways of linoleic acid desaturation in plant chloroplasts and plant desaturase regulation, which has application in modification of plant response to environmental stress, as well as optimization of oil seed composition.