Lipophilized apigenin derivatives produced during the frying process as novel antioxidants

To investigate whether apigenin, a common flavone in celery, can be esterified with carboxylic acids generated during frying leading to the consequently change of its antioxidant activity, we prepared a group of apigenin esters using fatty acids of varying chain lengths (C3:0-C18:0) and further checked their presence in celeries fried in soybean oil, rapeseed oil, and palm oil. Apigenin-7, 4'-O-dioctanoate was detected in celeries fried in soybean and rapeseed oil. Apigenin-7, 4'-O-dilaurinate was detected in celeries fried in all the three oils. In addition, all the apigenin esters exhibited lower ABTS and DPPH radical scavenging activity but improved lipophilicity and stronger cellular antioxidant activity than the parent compound, apigenin. These results demonstrated for the first time that apigenin could be esterified by carboxylic acids generated from lipid peroxidation under thermal processing, and these esters showed enhanced lipophilicity and cellular antioxidant activity.