Analysis of Isoflavones in Foods

Abstract

In recent years the nutritional and bioactive properties of foods are being intensively investigated with a view to control, in addition to food quality, their possible influence on human health. Because of this, there is a growing demand for rapid, selective, sensitive, and validated methods for analysis and quantification. Bioactive plant compounds include those with weak estrogenic activity (phytoestrogens), among which are the isoflavones. Some of the beneficial activities that have been attributed to isoflavones are anticarcinogenic activity, the prevention of cardiovascular disease, the improvement of bone health, and antioxidant activity. The objective of this work is to provide an updated review of the methods used in sample preparation and subsequent analysis for the determination of isoflavones in food samples, including both soybean and soy products, as well as other foods with low isoflavone contents. The review focuses on the most common sample preparation techniques used during the last 10 years, including both conventional solvent extraction and other more recent extraction techniques. Separation and detection methods, including current trends in liquid chromatography analysis, such as the use of monolithic columns or ultra-high-pressure liquid chromatography, are also discussed.

Isoflavones

“…The content of isoflavones in soy beans is approximately 1.5 mg/g, whereas the contents in soy-derived foods are usually lower [37]. Other dietary sources of isoflavones include chickpeas and beans, and small amounts of isoflavones are also contained in other plant products, such as fruits, vegetables, and nuts [38]. Apart from this, in the western (primarily American) population, the consumption of cow’s milk and dairy products was found to participate in the total isoflavone intake [39].…”

Polyphenols: A concise overview on the chemistry, occurrence, and human health

“…Isoflavones are found almost exclusively in the leguminous family of plants. Other sources are reported in apple, apricot, blackcurrant, cherry, cabbage, sweet potato, plum, date, onion, wheat, and melon pinapple (Abrankó, Nagy, Szilvássy, Stefanovits‐Bányai, & Hegedus, ; Bustamante‐Rangel, Delgado‐Zamarreño, Pérez‐Martín, Rodríguez‐Gonzalo, & Domínguez‐Álvarez, ; Konar, Poyrazoglu, Demir, & Artik, ; Kuhnle et al, ). Isoflavone‐containing preparations are promoted for alleviating menopausal symptoms.…”

Evaluation of the status quo of polyphenols analysis: Part II—Analysis methods and food processing effects

“…Modern techniques combine extraction and purification of isoflavonoids and include microwave‐assisted (MA) extraction, UAE, negative pressure cavitation extraction (NPCE), supercritical fluid extraction (SFE), accelerated solvent extraction (ASE) and pressurized hot water extraction (PHWE), and matrix solid‐phase dispersion (MSPD). This topic has been recently reviewed and a comprehensive summary of the most interesting extraction methods is reported (Blicharski, & Oniszczuk, 2017; Bustamante‐Rangel, Delgado‐Zamarreno, Perez‐Martin, Rodriguez‐Gonzalo, & Dominguez‐Alvarez, 2018); therefore, a detailed analysis of the above‐mentioned techniques is beyond the scope of the present review.…”

“…UV/Vis spectra of the majority of isoflavonoids exhibit two main peaks, the first in the range of 240 to285 nm (Band II, associated to ring A or benzoyl moiety) and the second in the range of 300 to 400 nm (Band I, originated from ring B, or cinnamoyl moiety). Consequently, UV/Vis detection is generally performed at 254 to 260 nm, while with the use of DAD it is possible to monitor the characteristic range of Band I (Bustamante‐Rangel et al., 2018). However, liquid chromatography combined with UV detection has doubtful specificity for separating and identifying isoflavonoids of highly similar structures since they frequently display quite similar UV absorption characteristics.…”