Effects and Mechanisms of Acylated Flavonoid on Cancer Chemopreventive Activity

Many studies have shown that flavonoids have various physiological activities such as anti-inflammatory, antibacterial, anti-cancer, and hepatoprotective activities. Meanwhile, its hydrophilic nature has led to low absorption into the body and the limitations of its bioactivity. Many acylated flavonoids and their bioactivities, including those obtained as natural compounds and those synthesized biochemically or chemically, have been reported to improve their bioavailability. This review focuses on the recent developments of the cancer chemopreventive activity of acylated flavonoids. Novel acylated flavonoids have been identified from nature since 2015, and many of them have shown high cytoprotective and anti-inflammatory effects by acylation of glycosyl residues. A large number of acylated flavonoids have been synthesized by enzyme-catalyzed and chemical methods, and their bioactivity has been evaluated. The introduction of acyl groups in the sugar residues showed higher antioxidant activity with increased lipophilicity and improved anti-inflammatory and cytoprotective effects and the ability of apoptosis induction in cancer cells. In contrast, introducing acyl groups into the hydroxy groups of aglycones resulted in less antioxidant activity but improved cancer proliferation inhibition and anti-inflammatory effects. Acylation of flavonoids tends to increase their bioactivity over the parent compound. The increased bioactivity by acylation can be attributed to increased lipophilicity and improved membrane permeability. Acylated flavonoids are one of a group of promising compounds that have cancer chemopreventive effects. However, the study of ADME (Absorption, Distribution, Metabolism, Excretion) will be essential to elucidate the relationship between acylation of flavonoids and the improvement of their bioactivity.