Stability of Isoflavone Daidzein and Genistein in Riboflavin, Chlorophyllb, or Methylene Blue Photosensitization

Abstract

Effects of photosensitizers including riboflavin, chlorophyll b, or methylene blue on the stability of daidzein and genistein were studied in model systems by high-performance liquid chromatography (HPLC). Concentration of daidzein and genistein in 80% methanol with riboflavin under light for 7 h was significantly decreased with the apparent 1st-order rate constants of 0.234 and 0.193/h, respectively, (P < 0.05), while those without riboflavin under light did not change significantly (P > 0.05). The stability of isoflavone aglycones in the dark did not change significantly irrespective of the presence of riboflavin (P > 0.05). The concentrations of daidzein and genistein in chlorophyll b or methylene blue model systems under light were not significantly different from those in the dark for 7 h (P > 0.05). Addition of sodium azide increased the stability of daidzein and genistein in riboflavin photosensitization with concentration dependent manner. However, the protective effects of beta-carotene addition on the photodegradation of isoflavones were not high. The stability difference of daidzein and genistein in riboflavin photosensitization may be due to the high reactivity of riboflavin through type I pathway, although singlet oxygen may be involved in part.

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

“…Major isoflavones in cheonggukjang have been reported as aglycones and β-glucosides (20,21), and the 2 new isoflavone metabolites succinyl-β-daidzin and succinyl-β-genistin were detected in laboratory-prepared and factory-produced cheonggukjang (22). These compounds were also found in natto (11,23). Major microorganisms in cheonggukjang and natto have been reported as B. subtilis and B. natto, respectively.…”

“…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.…”

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

“…Moreover, the stability of bisphenol A, an endocrine disrupting compound, was greatly reduced using riboflavin sensitization under visible light irradiation (9). Riboflavin photosensitization also influences the stability of beneficial nutrients and phytochemicals, including vitamin D 2 and isoflavones (10,11).…”

Distribution of Triacylglycerols and Fatty Acids in Soybean Oil with Thermal Oxidation and Methylene Blue Photosensitization

“…Several studies have reported that photosensitization can accelerate the chemical reactions in model and real food systems. Formation of sun-light flavor in riboflavin sensitized milk [4], oxidized volatile formation in chlorophyll sensitized lard [5] and linoleic acid [6], and the decrease of phytochemicals like isoflavones in a riboflavin model system [7] are some examples of detrimental influence of photosensitized oxidation on foods.…”