# Naturally Occurring Flavonoids and Isoflavonoids and Their Microbial Transformation: A Review
## 2 Isoflavonoids and Flavonoids from Actinomycetes and Fungi
### Isoflavonoids
#### 2.1.1 Simple Isoflavonoids  
Four known isoflavonoids, daidzein (**1**), genistein (**2**), daidzein-7-O-\(\alpha\)-L-rhammoside (**23**), and genistein-7-O-\(\alpha\)-L-rhammoside (**25**) were derived from Indonesian actinomycete _Streptomyces_ sp. TPU1401A. Compounds **1** and **2** could be transformed into 7-O-glycos, daidzein-7-O-\(\alpha\)-L-rhammoside and genistein-7-O-\(\alpha\)-L-rhammoside by strain TPU1401A, respectively. The strain TPU1401A grew better when adding daidzein-7-O-\(\alpha\)-L-rhammoside (**23**) and genistein-7-O-\(\alpha\)-L-rhammoside (**25**) instead of compounds **1** and **2**. This phenomenon suggested that the strain TPU1401A transformed isoflavones into isoflavone glycosides to hasten growth [32]. Five known isoflavones, genistein (**2**), prunetin (**3**), kakkatin (**4**), isoformonentin (**5**), and formononentin (**6**) were isolated from lichen-associated _Amycolatopsis_ sp. YIM 130642. These compounds exhibited weak antimicrobial activities against several pathogens [33]. EtOH extracts of the fungal strain, _Aspergillus_ sp. HK-388 afforded 8-hydroxydaidzein (**7**), which exhibited non-competitive inhibition on aldose reductase of human recombinant with its \(K_{\text{i}}\) value of 7.0 \(\upmu\)M [34]. During the chemical screening of a number of actinomycete strains from marine and terrestrial sources, six isoflavones were obtained from several _Streptomyces_ strains and identified to be daidzein (**1**), genistein (**2**), 7-O-methylgenistein (**3**), 4',6-dihydroxy-7-methoxyisoflavone (**4**), 4'-hydroxy-6,7-dimethoxyisoflavone (**8**), 4',7-bis-(\(\beta\)-cyanoryranosyl)-genistein (**28**), and genistein-4'-(6\"-methyl)-salicylate (**49**), in which compounds **8**, **28**, and **49** are new compounds [35]. Three isoflavonoids, 4',7,8-trihydroxyisoflavone (**7**), 3',4',7-trihydroxyisoflavone (**9**) and 8-chloro-3',4',5,7-tetrahydrooxyisoflavone (**10**) were obtained from the culture broth of _Streptomyces_ sp. OH-1049. These compounds showed antioxidant activity in vitro [36]. Compounds **9** and **10** were acetylated by adding pyridine and Ac\({}_{2}\)O to afford 3',4',7-triacetoxyisoflavone and 8-chloro-3',4',5,7-tetraacetoxyisoflavone, respectively [37]. Three new isoflavones, 3',5,7-trihydroxy-4',6-dimethoxyisoflavone (**11**), 3',5,7-trihydroxy-4',8-dimethoxyisoflavone (**12**) and 3',8-dihydroxy-4',6,7-trimethoxyisoflavone (**13**), were derived from _Streptomyces_ culture filtrates. Compounds **11** and **12** were able to suppress the catechol-O-methyltransferasease and dopa decarboxylase, and exhibit hypotensive action. Compound **13** was a specific inhibitor of catechol-O-methyltransferasease [38]. A novel isoflavone, 3',4',5,7-tetrahydrooxy-8-methoxy (**14**), and four known compounds, genistein (**2**), psi-tectorigenin (**15**), orobol (**16**), and 8-hydroxygenistein (**17**) were obtained from the culture filtrates of fungi and streptomyces during the screening of inhibiting dopa decarboxylase. Compounds **14** and **16** exhibited remarkable activity in restraining dopa decarboxylase. Compound **16** also showed an excellent hypotensive effect on spontaneously hypertensive rats [39]. Four isoflavone glycosides and two isoflavones were isolated from _Streptomyces xanthophaeus_. They were determined as daidzein (**1**), genistein (**2**), daidzein-4',7-di-\(\alpha\)-L-rhammoside (**22**), daidzein-7-\(\alpha\)-L-rhammoside (**23**), genistein-4',7-di-\(\alpha\)-L-rhammoside (**24**), and genistein 7-\(\alpha\)-L-rhammoside (**25**). All of these compounds showed \(\beta\)-galactosidase inhibiting activities [40]. Ten isoflavone glycosides and one isoflavone, daidzein (**1**), were obtained from _Streptomyces_ sp. RB1 associated with _Macrotermes natalensis_[17]. Later, seven isoflavone glycosides and one isoflavone, genistein (**2**) were additionally isolated from this strain [41]. Those glycosyl compounds are introduced in the following classification (Section 2.1.2).