Farmakognosi flavonoid
FarmakognosiflavonoidDosen : Yasmiwar Susilawati
FLAVONOIDPendahuluan :
Flavonoid merupakan golongan fenol alam yang terbesar, hampir
semua tumbuhan hijau mengandung flavonoid.
Menurut perkiraan 2% dari seluruh karbon yang difotosintesis
oleh tumbuhan atau + 1x 10 9 ton/tahun karbon diubah menjadi
flavonoid atau senyawa yang berkaitan erat dengannya (Smith,
1972).
Flavonoid pada tumbuhan Merupakan kandungan khas tumbuhan hijau
dan terdapat pada hampir semua bagian tumbuhan (daun, akar, kayu,
kulit kayu, nektar, tepung sari, bunga, buah, dan biji). Merupakan
pigmen tumbuhan yang paling umum, walaupun ada beberapa flavonoid
yang tidak berwarna.
Flavonoid pada hewan ???Flavonoid pada hewan jarang. Yang pernah
dilaporkan terdapat pada :kelenjar bau berang-berangpropolis
(sekresi lebah)dalam sayap kupu-kupuTetapi ini pun diperkirakan
bukan hasil biosintesis hewan
Penyebaran flavonoidpada tumbuhan yang terbesar terdapat pada
Angiospermaeterdapat kecendrungan : tumbuhan yang secara taksonomi
berkaitan akan menghasilkan flavonoid yang jenisnya serupa Dasar
Chemotaxonomi
DivisiNama UmumFlavonoid yang ditemukanProkariot
:SizofitaSianofitaBakteriAlga hijau - biru--Eukariot
:KlorofitaFeofitaRodofitaFungusBriofitaTrakeofita
AngiospermaeAlga hijauAlga coklatAlga merahFungusLumut
kerakLumut
hatiPsilofitaLycopodiumGimnospermae---Dihidrokalkon-glikosida
flavon, glik. flavonol (jarang)biflavon, O dan C -glikosida
flavonbiflavon, O dan C -glikosida flavonFlavon, biflavonoid,
flavanon,glikosida flavon, isoflavon,proantosianidin,
antosianin,flavonol, dihidroflavonol
Terdapat semua jenis flavonoid
Peran Flavonoid dalam tumbuhan :
Pengaturan tumbuhPengaturan fotosintesisKerja antimikroba dan
antivirusKerja terhadap seranggaFitoaleksin
Penggunaan Flavonoid
Antioksidan (cth : silimarin dari Silibum marianum sebagai
protektor hati dengan menghambat sintesis prostaglandin) Menghambat
reaksi oksidatif seperti fosfodiesterase, aldoreduktase, monoamina
oksidase, reverse transkriptase, DNA polimeraseMenghambat
lipooksigenaseMenurunkan agregrasiplatelet (mengurangi pembekuan
darah)
- Menghambat pendarahan- Melindungi asam askorbat dari oksidasi
(pengobatan skorbut) : turunan katekin pada buah jeruk-
Antihipertensi (menghambat enzim pengubah angiotensin)- Merangsang
pembentukkan estrogen pada mamalia (isoflavon)
Struktur Umum Flavonoid :
15 atom C yang tersusun dalam konfigurasi C6C3 C6
Struktur phenilbenzopiren
Flavonoid O-glikosidaFlavonoid dalam tumbuhan umumnya terdapat
dalam bentuk O-glikosida (jarang yang C-glikosida) : O-glikosida :
satu gugus hidroksil flavonoid (atau lebih) terikat pada satu gula
(atau lebih) dengan ikatan hemiasetal.Gula yang umum : glukosa Gula
lain : galaktosa, ramnosa, xilosa, arabinosaGula yang jarang :
alosa, manosa, fruktosa, apiosa, asam glukoronat, galakturonat.
Contoh Flavonoid O-glikosida :
Apigenin 7-O--D-glukopiranosida (R = H)
Flavonoid C-glikosida
Gula terikat pada atom karbon Flavonoid (terikat langsung pada
inti benzen dengan satu ikatan C-C)
Contoh flavonoid c-glikosidaApigenin 8-C--D-glukopiranosida
(Viteksin
)
Jenis Jenis Aglikon flavonoid :
FlavonFlavonolAntosianidinIsoflavonFlavanonKalkonAuronBiflavonoid
BIOSINTESIS flavonoidPrazat dari alur sikimat dan alur
asetat-malonat membentuk flavonoid Khalkon yang dianggap sebagai
flavonoid pertama yang terbentuk, semua jenis flavonoid lain
diturunkan darinya melalui berbagai alur
Important flavonoids1. QuercetinQuercetin is a flavonoid that
forms the "backbone" for many other flavonoids, including the
citrus flavonoids rutin, hesperidin, naringin and tangeritin. In
studies, quercetin is found to be the most active of the
flavonoids, and many medicinal plants owe much of their activity to
their high quercetin content. Quercetin has demonstrated
significant anti-inflammatory activity because of direct inhibition
of several initial processes of inflammation. For example, it
inhibits both the manufacture and release of histamine and other
allergic/inflammatory mediators. In addition, it exerts potent
antioxidant activity and vitamin C-sparing action.
2. Oligomeric proanthocyanidins (OPC)
Proanthocyanidins extracts demonstrate a wide range of
pharmacological activity. Their effects include increasing
intracellular vitamin C levels, decreasing capillary permeability
and fragility, scavenging oxidants and free radicals, and
inhibiting destruction of collagen, the most abundant protein in
the body.
3. Epicatechin
Epicatechin improves blood flow and thus seems good for cardiac
health. Cocoa, the major ingredient of dark chocolate, is loaded
with epicatechin and has been found to have nearly twice the
antioxidant content of red wine and up to three times that of green
tea.
Important dietary sources
Good sources of flavonoids include all citrus fruits, berries,
onions, parsley, legumes, green tea, red wine, seabuckthorn, and
dark chocolate (that with a cocoa content of seventy percent or
greater).
Citrus
The citrus bioflavonoids include hesperidin, quercetin, rutin (a
sugar of quercetin), and tangeritin. In addition to possessing
antioxidant activity and an ability to increase intracellular
levels of vitamin C, rutin and hesperidin exert beneficial effects
on capillary permeability and blood flow. They also exhibit some of
the anti-allergy and anti-inflammatory benefits of quercetin.
Quercetin can also inhibit reverse transcriptase, part of the
replication process of retroviruses (Spedding et al. 1989). The
therapeutical relevance of this inhibition has not been
established. Hydroxyethylrutosides (HER) have been used in the
treatment of capillary permeability, easy bruising, hemorrhoids,
and varicose veins.
Green Tea
Green tea polyphenols are potent antioxidant compounds that have
demonstrated greater antioxidant protection than vitamins C and E.
Green tea may also increase the activity of antioxidant enzymes.
Green tea polyphenols may inhibit cancer by blocking the formation
of cancer-causing compounds and suppressing the activation of
carcinogens. The major polyphenols in green tea are flavonoids
(catechin, epicatechin, epicatechin gallate, epigallocatechin
gallate(EGCG), and proanthocyanidins).Though both green tea and
black tea are derived from the same plant (Camellia sinensis), they
possess different antioxidants. In producing black tea the leaves
are allowed to oxidize, during which enzymes present in the tea
convert many polyphenols to larger molecules with different
biological effects. However, green tea is produced by lightly
steaming the fresh-cut leaf, which inactivates these enzymes, and
oxidation does not occur
Subgroups : Over 5000 naturally occurring flavonoids have been
characterized from various plants. They have been classified
according to their chemical structure, and are usually subdivided
into 6 subgroups :
Flavonols: Quercetin, Kaempferol, Myricetin, Isorhamnetin
Flavones: Luteolin, Apigenin Flavanones: Hesperetin, Naringenin,
Eriodictyol Flavan-3-ols: (+)-Catechin, (+)-Gallocatechin,
(-)-Epicatechin, (-)-*Epigallocatechin, (-)-Epicatechin 3-gallate,
(-)-Epigallocatechin 3-gallate, Theaflavin, Theaflavin 3-gallate,
Theaflavin 3'-gallate, Theaflavin 3,3' digallate, Thearubigins
Isoflavones: Genistein, Daidzein, Glycitein Anthocyanidins:
Cyanidin, Delphinidin, Malvidin, Pelargonidin, Peonidin,
Petunidin
