Tong quan tra_xanh

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1. 1.1. Tng quan v tr xanh1.1.1. Gii thi u chungCy tr c tn khoa hc l Camellia sinensis thuc h Theaceae. T lucon ngi nhn bit c tnh u vit v tnh a chc nng ca loi cy ny.Nhiu tc gi nghin cu v cc c tnh ca cy tr v ch ra hai c tnhsinh hc tiu biu ca tr l c tnh chng oxy ha v kh nng khng khun.Theo Trnh Xun Ng (2009) cy tr c ngun gc t ng Nam Chu .y l mt loi cy cng nghip lu nm, cho hiu qu kinh t cao, c trng hn 30 quc gia. Tr c nhiu ging khc nhau, cc ging tr ph bin hin nayl: Thea Jiunnanica, Thea Assamica, Thea Ainensis, c ngun gc t TrungQuc v min Bc nc ta. Ngy nay, hu ht cc tnh c u kin thun liu trng tr, song ba vng trng tr ln nht. Vng ch thng du (H Giang, Tuyn Quang, Lai Chu, Yn Bi) chimkhong 25% sn lng ch min Bc. Vng ch trung du (Vnh Phc, Ph Th, Bc Cn, Thi Nguyn). y l vngch ch yu chim n 75% sn lng ch min Bc vi nhiu nh my sn xutln. Vng ch Ty Nguyn (Gia Lai, Kon Tum, Lm ng, c Lc) ch yu trngging ch n v ch shan, ch Long.V phn loi khoa hc cy tr c th hin trong bng sau:Phn loi khoa hcGii PlanteeNgnh MagnoliopsidaB EricaleH TheaceaeChi CamelliaLoi C.Sinensis(Ngun: Trnh Xun Ng, 2009) 2. 1.1.2. Thnh phn ha hc ca l trThnh phn chnh ca l tr l nc n chim 75-82%, c quan h n qu trnhbin i sinh ha trong bp tr v n s hot ng ca cc men, l cht quantrng khng th thiu c duy tr s sng ca cy. Bn cnh thnh phnchnh l nc th thnh phn v hm lng cc cht ha tan trong ch l mttrong nhng mi quan tm hng u i vi cc nh nghin cu v tr xanh.Trong nhm cht tanin c xem nh thnh phn chnh, chim khong 27 34% cht kh trong ch. Vi mc ch nghin cu c tnh chng oxy ha vkhng khun ca tr xanh, trong bi bo co ny chng ti ch xt n hp chtPolyphenol tanin v n nh hng n kt qu th nghim.Bng thnh phn ha hc ca l trThnh phnHml ng(%)Polyphenol 36Methylxanthines 3.5Aminoacids 4Acid hu c 1.5Carotennoids < 0.1Volatiles < 0.1Carbonhydrate 25Protein 15Lignin 6.5Lipids 2Chlorophyll 0.5Tro 5Theo Chi-Tang Ho (2008) trong l tr cha hm lng polyphenol tng i 3. cao, thnh phn chnh ca polyphenol trong l tr c trnh by trong bngThnh phn cc hp cht polyphenol trong l tr xanhThnh phnHml ngTng s 18-36%Flavan-3-ols(catechin)12-24%Flavonol vglycosides3-4%Anthocyanins,Leucoanthocyanidin2-3%Phenolic ~5%Tanin l mt trong nhng thnh phn chyu quyt nh n phm cht tr.Tanin cn gi chung l hp cht phenol thc vt bao gm cc polyphenol ngin v cc polyphenol a phn t, bn cnh chng cn km theo cc hpcht phenol thc vt phi tanin c mu v v rt ng. T l cc cht trong thnhphn hn hp ca tannin tr khng ging nhau v ty theo tng gingT l cc cht trong thnh phn hn hp ca tanin ch khng ging nhau v tytheo tng ging ch m thay i. Tuy nhin, ngi ta xc nh c trong chtanin gm c 3 nhm ch yu l catechin, flavonol v glycoside, anthocyanidinv leucoanthocyanidin.1.1.2.1. CatechinMt hp cht khng mu, tan trong nc, c v ng cht mc khc nhauv c kh nng chng oxi ha. Catechin chim khong 85-90% tng lngtannin trong tr. Chng d dng b oxy ha v to hp cht phc tp vi nhiuvi nhiu cht khc nhau nh methylxanthine. 4. Trong l tr c 6 loi catechin chnh l epicatechin (EG), epigallocatechin-3-gallate (EGCG), epigallocatechin (EGC), epicatechin (EC),epigalocatechin-3-gallate (EGCG), epigallocatechin (EGC), epicatechingallate (ECG),gallocatechin (GC), v catechin (C). Trong EGCG l thnh phn polyphenolch yu trong tr chim khong 12% khi lng cht kh trong tr k n lEGC, ECG v EG. T l cc thnh phn c th hin trong bng sau.Thnh phn catechin trong l trThnh phn Hm lngEpicatechin (EC) 1-3%Epigallocatechin (EGC) 3-6%Epicatechin gallate (ECG) 3-6%Epigallocatechin gallate(EGCG)8-12%Catechin (C) 1-2%Gallocatechin (GC) 3-4%Hnh nh cng thc cu to ca mt s catechin: 5. Hnh 1.1: Cng thc cu to mt s loi catechin 6. 1.1.2.2. Flavonol v glycosideChim khong 1-2% cht kh v bao gm cc thnh phn chnh quercetin (0,27-0,48%), kaempferol (0,14-0,32), myricitin (0,07 -0,2%). Cc glucoside caflavonol l dng lin kt ca Flavonol vi monosacchaside (nh glucose,rhamnose, galactose, arabinose) hoc disaccharide (nh rutinose). Nhngflavonol glucoside c bn trong tr bao gm: rutin (0,05-0,1%), querceringlycoside (0,2 0,5%) v kaempferol glycoside (0,16 -0,35%). Cc flavonol vglucoside thng c mu vng sng. C t nht 14 cht c tm thy. Ccflavonol t b bin i trong qu trnh ln men. Chng l cc thnh phn c licho sc khe trong ch m khng c c tnh. Sau khi vo c th chng xuthin trong mu, th hin hot tnh m khng tch ly li.Hnh 1.2. cng thc ha hc ca flavonol1.1.2.3. Anthocyanidin v LeucoanthocyanidinAnthocyanidin l mt hp cht khng mu, nhng khi tc dng vi dung dchacid v c th c mu , d b oxi ha v trng hp. Anthocyanidin thng tnti di dng glycozit, cn gi l anthocyanin.Anthocyanidins bao gm pelargonidin, cyanidin, delphinidin, and tricetinidin,chng chim khong 0.01% khi lng l tr kh. 7. Cc cng thc cu to ca cc anthocyanidinBn cnh cc cht Anthocyanidin, trong l tr cn thy c Leucoanthocyanidin(Flavadiol 3,4) v cc dn xut glucoside ca chng. Leucoanthocyanidin hpcht khng mu, d dng b oxy ha v ngng t hnh thnh sc t trong qutrnh ln men tr. Chng l tin t ca nhm cht mu quan trng lanthocyanidin v anthocyanin (Anthocyanidin glucoside).Ngoi cc nhm flavonoid nu trn, ch cn cha cc cht c gi tr khc nhtinh du, cc carotenoid, vitamin, cc cht khong vi lng, v caffein. Ty theotng chng loi, ch c 1,5 5% caffein. Trong y hc, caffein c dng rngri vi paracetamol lm thuc h st.1.1.2.4. Acid phenolicAcid phenolic l mt nhm cht bao gm cc acid chnh sau: acid gallic (0.5-1.4%), acid chlorogenic (0.3%), v theogallin (1-2%). Trong tr xanh, acidphenolic l tin t ca catechin gallate. 8. Cng thc cu to ca cc acid phenolicNgoi cc hp cht polyphenol, tr cn c nhiu hp cht khc, bao gmalkaloid, amino acid, protein, glucid, volatile v kim loi dng vt.Protein chim 15% hm lng cht kh trong tr, protein ny bao gm ccenzym nh: polyphenol oxydase (xc tc phn ng oxy ha catechin),glucosidase (xc tc phn ng thy phn cc hp cht mi), lipooxydase (xctc s hnh thnh cc andehyde d bay hi) v mt s enzym xc tc cho stng hp methyl xanthine.Hn na trong tr cn c mt s cht nh canxi, mangan, crom, flo. Mt shp cht bay hi bao g m: alcohol, carbonyl, ester, v cc hp cht vng.1.1.3. c tnh sinh hc ca tr1.1.3.1. Hot tnh chng oxy haC nhiu nghin cu khng nh hot tnh chng oxy ha chnh ca tr l dohot tnh ca cc hp cht polyphenol. Tht vy trong mt bi bo khoa hc caMai Tuyn, V Bch Lan v Ng i Quang nghin cu hot tnh chng oxy haca polyphenol tch chit t l tr xanh bo qun ht du ci a ra ktlun polyphenol chit xut t l tr xanh th phm c tc dng khng oxy ha rtr rt v mnh hn nhiu so vi acide ascorbic v tocopherol. Tc dng sinh hcca cc polyphenol tr hay ca dch chit l tr xanh c gii thch l do chngc tc dng kh cc gc t do, ging nh tc dng ca cc cht antioxidant.Trong cc polyphenol tr, nhng gc c chc nng chng oxy ha l gc ortho-3,4-dihydroxyl (catechol), hoc cc v tr 3,4,5-trihydroxyl (gallate) ca vng B,nhm gallate v tr C3 ca vng C, nhm hydroxyl v tr C5, C7 ca vng A. 9. Hnh: Cc nhm c chc nng chng oxy ha ca cc polyphenolC ch chng oxy ha ca tr thuc c ch chng oxy ha ca cc hp chtphenol. Tnh chng oxy ha ca cc ankylphenol th hin ch chng c khnng v hiu ha cc gc peroxyt, do n c th ct mch oxy ha. Sn phmu tin xut hin l cc gc phenol to thnh do nguyn t hydro ca nhmhydroxyl c nhng cho gc peroxyt:Hnh: C ch chng oxy ha ca polyphenolCc gc phenol rt n nh, km hot tnh, nh vy chng khng c kh nngsinh mch oxy ha tip theo. Hot tnh chng oxy ha ca cc hp cht ankylphenolc tng ln bng cch hydroxyl ha vo phn t phenol, v cc hp cht polyphenolc hot tnh tt hn monophenol.Chng c mt s tnh cht sau: Dng kh ca chng c th phn ng vi cc gc t do, chuyn thnh dngoxy ha: 10. Dng hydroquinone(Dng kh)Dng quinon(Dng oxy ha) Dng oxy ha ca chng c th chuyn thnh dng lng gc v nh vychng c kh nng phn ng vi hai gc t do na. 11. c bit dng oxy ha v dng kh ca chng c th tng tc vi nhau thunnghch to gc Semiquinon:Ngoi ra, cc hp cht catechin trong tr cn c kh nng to phc kim loi chyu l Fe, Cu, y l nhng cht xc tc to ra nhng gc t do. T l EGC,EGCG, ECG v EC to phc vi kim loi l 3:2, 2:1, 2:1, 3:1.C 2 catechin v theaflavin c th to phc vi Fe (III). Theaflavin c th tophc vi Fe (III) to thnh dng phc, sau b oxy ha thnh o-quinon vc chuyn i thnh dehdro theaflavin, theanaph thoquinon v polymer.1.1.4. Hot tnh khng khunThng 8/1996 gio s T. Shimaura cng tc ti trng i hc y khoaShowa (Nht Bn) c cng trnh din thuyt v tc ng dit khun E-coli-157 ti hi tho chuyn dit khun ca tr xanh. ng khng nh rngcatechin trong tr xanh c kh nng tiu dit cc loi vi khun lm h hngthc phm v loi b cc c t do chng gy ra. Cc th nghim ca ng chothy tr xanh c th dit 100.000 khun E. Coli trong vng 5h. C ch hotng ca cc catechin l ph hy mng t bo bn ngoi ca vi khun.EGCG v ECG l catechin c kh nng khng khun mnh nht. Catechin lpolyphenol c th gy ra hin tng ngng kt bng cch to lin kt trc tipvi protein. y l tnh cht c trng ca catechin chu trch nhim cho hottnh khng khun.Nhiu nghin cu ch ra rng ra rng thnh phn ca thnh t bo lyu t quyt nh n kh nng khng EGCG ca vi khun. Peptidogly trongthnh t bo vi khun c khnng ngn chn cc hot ng dit khun caEGCG. Peptidoglycan l mt phc lin kt ngang ca polysaccharide vpeptide. Thnh t bo ca vi khun gm c 30-50 lp peptidoglycan bo v vi 12. khun trc p sut thm thu. EGCG c th trc tip lin kt vipeptidoglycan v lm t bo b ng t ngn cn hot ng sinh tng hp cavi khun. Catechin ca tr c kh nng c ch cc enzym c ngun gc t vikhun. c ch hot ng ca enzyme EGCG lin kt trc tip vi cc phn tsinh hc v gy ra hin tng ngng kt lm mt hot tnh ca enzym.1.1.5. Tc dng dc l ca tr xanhNghin cu ca cc nh khoa hc trong v ngoi nc, cho thy, ch xanhmang li nhiu tc dng tt nh thnh phn ha hc a dng vi cc cht h trsc kho v phng chng bnh tt.Theo ThS Ng c Phng, nguyn cn b Khoa Ti nguyn - Dc liu,Vin Dc liu a ra kt qu. V dc l hc, ch c v ng cht, tnhmt, c tc dng thanh nhit gii kht, tiu cm, li tiu, nh thn lm cho uno c th thi, khi chng mt xy xm, da tht mt m, bt mn nht vcm t l. Do c cafein v theophyllin, ch xanh c xem l mt cht kchthch no, tim v h hp, gip tng cng sc lm vic ca tr c v ca c,lm tng h hp, tng cng v iu ho nhp p ca tim.Thnh phn catechin c trong tr xanh c nhiu nghin cu chng minhc tc dng gim nguy c gy ung th, gim kch thc khi u, gim lngng trong mu, gim cholesterol, dit khun, dit virus cm, chng himing. Ngoi ra, cc nghin cu trn th gii c