As flavonas (do latín flavus, 'amarelo'), son unha clase de flavonoides baseada nun esqueleto de 2-fenilcromen-4-ona (2-fenil-1-benzopiran-4-ona) (imaxe da dereita).
As flavonas son comúns nos alimentos, principalmente nas especias, e froitos e vexetais vermellos e púrpuras. Entre as flavonas comúns están a apixenina (4',5,7-trihidroxiflavona), luteolina (3',4',5,7-tetrahidroxiflavona), tanxeritina (4',5,6,7,8-pentametoxiflavona), crisina (5,7-dihidroxiflavona) e 6-hidroxiflavona.
Inxestión e eliminación
As flavonas encóntranse principalmente en especias e plantas vermellas e púrpuras. O consumo diario estimado de flavonas é duns 2 mg. As flavonas non presentan efectos fisiolóxicos no corpo humano e non teñen ningún poder como antioxidantes. Despois da súa inxestión e metabolización, as flavonas, outros polifenois e os seus metabolitos son absorbidos bastante pouco polos órganos do corpo e son excretados rapidamente pola urina, o que indica a súa presumida ausencia de papeis no metabolismo do corpo.
Interaccións con fármacos
Química orgánica
En química orgánica hai varios métodos para a síntese de flavonas:
- Reacción de Allan–Robinson
- Síntese de Auwers
- Rearranxo de Baker–Venkataraman
- Reacción de Algar–Flynn–Oyamada
Outros métodos son a ciclación deshidratante de certas 1,3-diaril dicetonas.
Rearranxo de Wessely–Moser
O rearranxo ou redistribución de Wessely–Moser (1930) foi unha feramenta importante para a dilucidación da estrutura dos flavonoides. Implica a conversión da 5,7,8-trimetoxiflavona en 5,6,7-trihidroxiflavona con hidrólise dos grupos metoxi a grupos fenol. Tamén ten un potencial sintético, por exemplo:
Esta reacción de redistribución ten lugar en varios pasos: A apertura do anel á dicetona, B rotación do enlace con formación dunha interacción favorable con fenil-cetona tipo acetilcetona, e C hidrólise de dous grupos metoxi e peche do anel.
Flavonas comúns
| Nome | Estrutura | R3 | R5 | R6 | R7 | R8 | R2' | R3' | R4' | R5' | R6' |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Esqueleto de flavona | – | – | – | – | – | – | – | – | – | – | |
| Primuletina | – | –OH | – | – | – | – | – | – | – | – | |
| Crisina | – | –OH | – | –OH | – | – | – | – | – | – | |
| Tectocrisina | – | –OH | – | –OCH3 | – | – | – | – | – | – | |
| Primetina | – | –OH | – | – | –OH | – | – | – | – | – | |
| Apixenina | – | –OH | – | –OH | – | – | – | –OH | – | – | |
| Acacetina | – | –OH | – | –OH | – | – | – | –OCH3 | – | – | |
| Genkwanina | – | –OH | – | –OCH3 | – | – | – | –OH | – | – | |
| Equinoidina | – | –OH | – | –OCH3 | – | –OH | – | – | – | – | |
| Baicaleína | – | –OH | –OH | –OH | – | – | – | – | – | – | |
| Oroxilon | – | –OH | –OCH3 | –OH | – | – | – | – | – | – | |
| Negleteína | – | –OH | –OH | –OCH3 | – | – | – | – | – | – | |
| Norwogonina | – | –OH | – | –OH | –OH | – | – | – | – | – | |
| Wogonina | – | –OH | – | –OH | –OCH3 | – | – | – | – | – | |
| Geraldona | – | – | – | –OH | – | – | –OCH3 | –OH | – | – | |
| Titonina | – | – | – | –OCH3 | – | – | –OH | –OCH3 | – | – | |
| Luteolina | – | –OH | – | –OH | – | – | –OH | –OH | – | – | |
| 6-Hidroxiluteolina | – | –OH | –OH | –OH | – | – | –OH | –OH | – | – | |
| Crisoeriol | – | –OH | – | –OH | – | – | –OCH3 | –OH | – | – | |
| Diosmetina | – | –OH | – | –OH | – | – | –OH | –OCH3 | – | – | |
| Pilloína | – | –OH | – | –OCH3 | – | – | –OH | –OCH3 | – | – | |
| Velutina | – | –OH | – | –OCH3 | – | – | –OCH3 | –OH | – | – | |
| Norartocarpetina | – | –OH | – | –OH | – | –OH | – | –OH | – | – | |
| Artocarpetina | – | –OH | – | –OCH3 | – | –OH | – | –OH | – | – | |
| Escutelareína | – | –OH | –OH | –OH | – | – | – | –OH | – | – | |
| Hispidulina | – | –OH | –OCH3 | –OH | – | – | – | –OH | – | – | |
| Sorbifolina | – | –OH | –OH | –OCH3 | – | – | – | –OH | – | – | |
| Pectolinarixenina | – | –OH | –OCH3 | –OH | – | – | – | –OCH3 | – | – | |
| Cirsimaritina | – | –OH | –OCH3 | –OCH3 | – | – | – | –OH | – | – | |
| Mikanin | – | –OH | –OCH3 | –OCH3 | – | – | – | –OCH3 | – | – | |
| Isoscutelareína | – | –OH | – | –OH | –OH | – | – | –OH | – | – | |
| Zapotinina | – | –OH | –OCH3 | – | – | –OCH3 | – | – | – | –OCH3 | |
| Zapotina | – | –OCH3 | –OCH3 | – | – | –OCH3 | – | – | – | –OCH3 | |
| Cerrosilina | – | –OCH3 | –OCH3 | – | – | – | –OCH3 | – | –OCH3 | – | |
| Alnetina | – | –OH | –OCH3 | –OCH3 | –OCH3 | – | – | – | – | – | |
| Tricetina | – | –OH | – | –OH | – | – | –OH | –OH | –OH | – | |
| Tricina | – | –OH | – | –OH | – | – | –OCH3 | –OH | –OCH3 | – | |
| Corimbosina | – | –OH | – | –OCH3 | – | – | –OCH3 | –OCH3 | –OCH3 | – | |
| Nepetina | – | –OH | –OCH3 | –OH | – | – | –OH | –OH | – | – | |
| Pedalitina | – | –OH | –OH | –OCH3 | – | – | –OH | –OH | – | – | |
| Nodifloretina | – | –OH | –OH | –OH | – | – | –OCH3 | –OH | – | – | |
| Jaceosidina | – | –OH | –OCH3 | –OH | – | – | –OCH3 | –OH | – | – | |
| Cirsiliol | – | –OH | –OCH3 | –OCH3 | – | – | –OH | –OH | – | – | |
| Eupatilina | – | –OH | –OCH3 | –OH | – | – | –OCH3 | –OCH3 | – | – | |
| Cirsilineol | – | –OH | –OCH3 | –OCH3 | – | – | –OCH3 | –OH | – | – | |
| Eupatorina | – | –OH | –OCH3 | –OCH3 | – | – | – | –OCH3 | –OH | – | |
| Sinensetina | – | –OCH3 | –OCH3 | –OCH3 | – | – | – | –OCH3 | –OCH3 | – | |
| Hipolaetina | – | –OH | – | –OH | –OH | – | –OH | –OH | – | – | |
| Onopordina | – | –OH | – | –OH | –OCH3 | – | –OH | –OH | – | – | |
| Wightina | – | –OH | – | –OCH3 | –OCH3 | –OCH3 | –OH | – | – | – | |
| Nevadensina | – | –OH | –OCH3 | –OH | –OCH3 | – | – | –OCH3 | – | – | |
| Xantomicrol | – | –OH | –OCH3 | –OCH3 | –OCH3 | – | – | –OH | – | – | |
| Tanxeretina | – | –OCH3 | –OCH3 | –OCH3 | –OCH3 | – | – | –OCH3 | – | – | |
| Serpilina | – | –OH | – | –OCH3 | –OCH3 | –OCH3 | –OCH3 | –OCH3 | – | – | |
| Sudaquitina | – | –OH | –OCH3 | –OH | –OCH3 | – | –OCH3 | –OH | – | – | |
| Acerosina | – | –OH | –OCH3 | –OH | –OCH3 | – | –OH | –OCH3 | – | – | |
| Himenoxina | – | –OH | –OCH3 | –OH | –OCH3 | – | –OCH3 | –OCH3 | – | – | |
| Gardenina D | – | –OH | –OCH3 | –OCH3 | –OCH3 | – | –OH | –OCH3 | – | – | |
| Nobiletina | – | –OCH3 | –OCH3 | –OCH3 | –OCH3 | – | –OCH3 | –OCH3 | – | – | |
| Escaposina | – | –OH | –OCH3 | –OH | –OCH3 | – | –OCH3 | –OCH3 | –OH | ||
| Nome | Estrutura | R3 | R5 | R6 | R7 | R8 | R2' | R3' | R4' | R5' | R6' |
Véxase tamén
Ligazóns externas
- Flavones Medical Subject Headings (MeSH) na Biblioteca Nacional de Medicina dos EUA.
