Ahmed I. Foudah and Maged Saad Abdel-Kader

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http://dx.doi.org/10.5772/intechopen.68701

#### **Abstract**

Isoflavonoids are interesting class of natural products due to their positive effects on human health. Isoflavonoids include isoflavones, isoflavanones, isoflavans, rotenoids and pterocarpans. Although they are reported from many plant families, most isoflavonoids are produced by the subfamily *Papilionaceae* of the Fabaceae. Various chromatographic methods have been applied for the purification of isoflavonoids. Simple Ultra Violet (UV) absorption spectra as well as both One and two dimensional NMR (1D- and 2D-NMR) are critical for the identification of isoflavonoids. Each class of isoflavonoids has its unique feature in both 1 H- and 13C-NMR that enable their proper characterization. High Resolution Mass Spectrometry (HRMS) is a substantial tool in such challenge. *In vitro* experiments indicated that isoflavonoids possess antioxidant, antimutagenic, antiproliferative as well as cancer preventive effects. Epidemiological studies provide support for some of these effects on human. Members of this class also are reported to have antimicrobial activity. In this chapter, isoflavones, isoflavanones, isoflavans, homoisoflavonoids and isoflavenes will be discussed in relation to their occurrence, methods of purification, spectral characters helpful in structure elucidation as well as their biological importance.

**Keywords:** isoflavones, isoflavanones, isoflavans, homoisoflavonoids, isoflavenes

### **1. Introduction**

Genstin (**1**) was the first isolated isoflavone from *Genista tinctoria* known as Dyer's Brrom in 1899 [1]. Later in 1926 [2], the structure was identified. Genstin (**1**) was isolated from Soybeans in 1941 [3]. Although the main source of isoflavonoids is member of the Fabaceae [4], some were reported from other families such as Amaranthaceae [5, 6], Rosacease [7] and Poaceae [8]. Isoflavonoids were also reported from fungi [9] and Propolis [10]. The dietary consumption of isoflavonoid-rich sources is linked with health advantages toward osteoporosis, postmenopausal symptoms, cardiovascular diseases and chemo-prevention [11]. People from SE

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Asia have much lower risk of developing prostate cancer compared to Americans due to high consumption of soy rich in isoflavonoids. Upon immigration to the USA and changing the dietary components, this difference rapidly disappears [12]. Isoflavonoids are also classified as dietary antioxidants [13]. These facts were the driving force behind the use of isoflavonoidrich sources as nutraceutical and dietary supplements [14].

Isoflavonoids are a large subclass of the most common plant polyphenols containing 15 carbon atoms known as flavonoids [15]. In isoflavonoids (3-phenylchromans), the phenyl ring B is attached to heterocyclic ring C at position 3 rather than 2 in flavonoids [16]. Generally, flavonoids are biosynthesised via Shikimic acid pathway. Shikimic acid is also a precursor for the biosynthesis of phenylpropanoids and aromatic acids. At certain stages, the activity of the key enzyme chalcone isomerase (CHI) resulted in the formation of flavanones that converted to isoflavonoids under the influence of isoflavone synthase [17]. The biosynthesis of isoflavonoids, consequently, is considered as an offshoot from the flavonoids biosynthetic pathway [18]. Highest level of isoflavonoids occurs usually in roots, seedlings and seeds [18, 19].

Isoflavonoids are sub-classified into many subclasses based on the oxidation status of ring C as well as the formation of a forth ring 'D' by coupling between rings B and C. Subclasses free from ring D include isoflavones, isoflavanones, isoflavan-4-ol, homoisoflavonoids, isoflavans and isoflav-3-ene. Rotenoids, pterocarpans, coumaronochromones and coumaronochromene represent the subclasses with additional ring D formation [11].

This chapter will deal with the different aspects of the isoflavonoid subclasses keeping the original three-ring skeleton (**Figure 1**). Occurrence, isolation, key spectroscopic characters and biological activities will be covered starting from 2000 to date.

**Figure 1.** The skeletons of the isoflavonoids with three-ring structures.
