Effects of Riboflavin Photosensitization on Daidzein and Its Photosensitized Derivatives

Abstract

Photosensitized compounds from daidzein were studied in a riboflavin model system under visible light irradiation by high-performance liquid chromatography (HPLC). As the period of light irradiation increased, concentration of daidzein decreased significantly (P < 0.05) and new peaks of daidzein derivatives were observed and changed during photosensitization. Three new peaks from photosensitized daidzein were tentatively identified as 7-, 3', 4'-trihydroxyisoflavone (or 3'-hydroxydaidzein) and 2 dimmers of daidzein by a combination of HPLC-mass spectrometry (MS) and retention times of standard compounds by HPLC. Addition of sodium azide and removal of headspace oxygen treatment affected the formation of newly formed peaks. The type I pathway of riboflavin photosensitization played more important roles than type II pathways on the formation of daidzein derivatives. Practical Application: Isoflavones are important phytochemicals found in soy foods. Generally, many foods containing soy ingredients are displayed under visible light irradiation. Also, riboflavin can be found in many foods containing vegetables. The results of this study can be used to understand the stability and changes of isoflavone aglycones in soy and soy-based foods under visible light irradiation.

Changes in isoflavone profiles and antioxidant activities in isoflavone extracts from soybeans and soyfoods under riboflavin photosensitization

“…Isoflavones from each sample were recovered according to a previously reported method (11,12). Recovered isoflavones were confirmed using HPLC.…”

“…The final concentration of riboflavin was 0.40 mM. Extract samples containing mixtures of riboflavin and isoflavone extracts were stored in a custom-made light box containing 6 fluorescent lights producing 1,330 Lux at room temperature for a total of 120 min in 30 min intervals (11,12). Extract samples were prepared in triplicate.…”

“…Almond-incubated extract samples had higher aglycone contents (Table 2), which may indicate appropriate precursors for enhancement of antioxidant activities, compared with other derivatives, including malonyl forms, acetyl forms, and β-glucoside forms. Riboflavin photosensitization generated genistein and daidzein with an additional hydroxyl group from the original genistein and daidzein forms (12,13). Seol et al (13) reported that the radical scavenging activity in a mixture of genistein and riboflavin under visible light irradiation increased significantly, perhaps due to the aglycones of isoflavones with additional hydroxyl groups.…”

“…Photolysis of benzo[a]pyren can generate 1,6-benzo[a]pyren-dione, 3,6-benzo[a]pyren-dione, and 6,12-benzo[a]pyren-dione derivatives (8). Moreover, 7',3',4' trihydroxyisoflavone (or 3'-hydroxydaidzein) and genisteins with an additional hydroxyl group were identified after daidzein and genistein, respectively, were subjected to riboflavin photosensitization (12,13).…”

Modification of isoflavones by processing and photosensitization in model and food systems

“…Singlet oxygen can deactivate physically or react with substrates possessing double The so called phototransformation can be observed in model systems containing riboflavin and daidzein [Park et al, 2010b]. Visible light irradiation in the presence of riboflavin generates three new peaks from daidzein, which were tentatively identified as 7, 3',4' trihydroxyisoflavone (or 3'-hydroxydaidzein) and two dimmers of daidzein [Park et al, 2010b]. Formation of dimmers of daidzein and 3'-hydroxydaidzein may be influenced by both type I and type II pathways.…”