A PPARγ ligand present in Actinidia fruit (Actinidia chrysantha) is identified as dilinolenoyl galactosyl glycerol

Abstract

Activity-guided fractionation of Actinidia fruit species, including Kiwifruit, has identified DLGG (dilinolenoyl galactosyl glycerol) as a potent PPARγ (peroxisome-proliferator-activated receptor γ) ligand. DLGG is a type of MGDG (monogalactosyl diacylglycerol) and is present in all chloroplasts, and therefore all green fruits and vegetables. PPARγ is a ligand-activated transcription factor that regulates glucose metabolism and inflammation. An ethyl acetate extract of Actinidia chrysantha was fractionated by HPLC and the PPARγ-binding activity was detected by FP (fluorescence polarization). Linoleic and α-linolenic acids in A. chrysantha were readily detected as PPARγ ligands. Slow-binding PPARγ ligands were detected in several hydrophobic fractions. High-resolution MS identified DLGG as one of these ligands and confirmed that its binding is non-covalent. DLGG is a slow-binding PPARγ ligand with an IC50 of 1.64 μM, ±0.093 achieved after 45 min equilibration. DLGG is the first example of a form of DAG (diacylglycerol) that is a PPARγ ligand. In addition, DLGG is the first reported glycolipid ligand for PPARγ and also the first non-covalent, slow-binding PPARγ ligand.