Neoflavonoids

In addition to the flavonoids with ring B attached to the C2 position of ring C, other types of flavonoids, particularly those with ring B attached to C3 (isoflavones), C4 (neoflavonoids), and open C ring (chalcones), have also been commonly found in fruits and vegetables. 

Korec R, Sensch KH, Zoukas T. (2000) Effects of the neoflavonoid coutareagenin, one of the antidiabetic active substances of Hintonia latiflora, on streptozotocin-induced diabetes mellitus in rats. Arzneimittelforschung 50 122-128. 

Bekker, M. et al., An isoflavanoid-neoflavonoid and an 0-methylated isoflavone from the heartwood of Dalbergia nitidula, Phytochemistry, 59, 415, 2002. 

Flavonoids can be classified according to their biosynthetic origins. Some flavonoids are both intermediates in biosynthesis and end-products, e.g. chalcones, flavanones, flavanon-3-ols and flavan-3,4-diols. Other classes are only known as the end-products of biosynthesis, e.g. anthocyanins, flavones and flavonols. Two further classes of flavonoids are those in which the 2-phenyl side-chain of flavonoid isomerizes to the 3-position (giving rise to isoflavones and related isoflavonoids) and then to the 4-position (giving rise to the neoflavonoids). The major classes of flavonoids, with specific examples, are summarized helow. 

Isoflavones, isoflavanones and neoflavonoids are also members of the flavonoid group. They all have the C6-C3-C6 stmcture but the B-ring is in a different position on the oxygen heterocycle. Examples are isoflavone (1.33) and the neoflavonoid dalbergin (1.34). 

Flavones, coumarins (neoflavonoids), and other oxygen-containing compounds were found to inhibit monoamine oxidases A and B in a reversible and time-independent manner. 

Finally, the neoflavonoid latifolin, a major constituent of Daltergia latifolia, and its dimethyl and diethyl derivatives, undergo aryl-di-7i-methane rearrangements on both direct and triplet-sensitized irradiation [27d,e] Thus, Pyrex filtered irradiation of the dimethyl derivative 69 affords the -cyclopropane 70 in 90% yield (Sch. 26). 

Hintonia latiflora (copalchi bark) has been advocated as a hypoglycemic agent, an effect that has been attributed to the neoflavonoid coutareagenin (1). Its use has been associated with liver toxicity but a causal relation could not be established (2). 

L. Charles, F. Laure, P. Raharivelomanana, J.-P. Bianchini, Sheath liquid interface for the coupling of NPLC with ESI-MS and its application to the analysis of neoflavonoids, J. Mass Spectrom., 40 (2005) 75. 

The N. occur in dyer s woods, examples are brazilin, the main pigment in red woods and the blue wood pigment haematoxylin. They are colorless precursors of the neoflavonoid pigments. Brazilin is oxidized to bra-zilein (see brazilin) and hematoxylin to hematein (see... 

Brazilin and hematoxylin were first isolated a long time ago from the heart wood of Caesalpinia spp. and Haematoxylon campechianum L. (Leguminosae) respectively. Aqueous plant extracts have been widely used as mordant dyes especially on silk and furs (63). The extract of the Mexican species H. braziletto was found to exhibit antibacterial activity (59). It was assumed that these compounds belong to the class of the neoflavonoids (20, 31). 

The notable resistance to decay of rosewoods (usually from the genera Dalbergia and Machaerium) is due to the presence of several types of phenolic compounds the neoflavonoids are major among these (Donnelly, 1982 Donnelly and Cannon, 1986). 

Fig. 11.37. Biosynthesis of neoflavonoids (Gottlieb et al., 1970 modified and used with permission of the copyright owner. Academia Brasileira de Ciencias, Rio de Janeiro).

Neoflavonoids Flavonoids (see) with a 4-phenyl-chroman (neoflavan) skeleton, or a corresponding structure in which the C3 chain (C2, C3, C4) is not cy-clized with oxygen. 

The third class of flavonoids, neoflavonoids, is closely structurally related to flavonoids and isoflavonoids. They have a 4-phenylchroman (4) skeleton. 4-Arylcoumarin (21), 3,4-dihydro-4-arylcoumarin (22), and neoflavene (23) fall into this group. 

Nemaliales, 2887 Nematolepis, 734 Neocarzinostatin producer, 990 Neodictyoprolenol, 2895 Neoflavenes, 1555 Neoflavonoids, 1555, 1620 Neoisomenthol, 2979 Neolignans, 1557 Neomarchantin, 1918 Neomenthol, 2979 Neonatal T, 2419 Neopetrosia, 1291 Neophysalin, 3468 Neopinone, 430... 

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