Study On Chemical Composition And Fuzhuan Tea Antioxidant Activity

Fuzhuan brick tea contains many chemical components such as polyphenols, caffeine, amino acids, polysaccharides, trace elements and has the capacity of antibacterial, hypolipidemic, antiobesity, hypoglycemic, antitumor and so on. In addition, Fuzhuan brick tea also owns the activity of scavenging free radical, protecting cells from oxidative damage, but there were just sporadic reports about antioxidant activity of the water extract of Hunan Fuzhuan brick, which were confined to the level of crude extract and fractions, and were not systematic and comprehensive. Therefore, this paper surveyed the compounds from Fuzhuan brick, and the phenolics and flavonoids contents of different extracts from fuzhuan brick tea were detected, the antioxidant activities of different extracts from fuzhuan brick tea and the compounds separated from fuzhuan brick tea were also evaluated.First, this researeh concerned on a study of the chemical compositions of Fuzhuan brick tea. Silica gel column chromatography, gel column chromateraphy, thin layer chromatography and high performance liquid chromatography were used to separate and purify compounds from ethyl acetate and n-butanol extracts from Fuzhuan brick tea.11compounds’structures were identified by NMR, MS and comparison with authentic compounds. These compounds are:(1) caffeine,(2) diisooctyl phthalate,(5)4,6,10,4’-tetrahydroxyaurone,(6) dibutyl phthalate,(10) echinulin,(17) Neoechinulin A,(19)(-)-epigallocatechin3-O-gallat,(20) gallocatechin3-O-gallate(GCG),(21)(-)-epicatechin3-O-gallate(ECG),(22)(+)-catechin,(23)3,5,7,2’,5’-pentahydroxyflavan. Compounds10and17were isolated from Fuzhuan brick tea for the first time.Total phenolics contents of different extracts from fuzhuan brick tea were determined by the Folin-Ciocalteu color method, the content was60.05-292.09mg-g-1. The flavonoid contents of different extracts from fuzhuan brick tea were determined by the AICI3color method, the content was83.24-222.86mg-g-1The antioxidant activities of different extracts from fuzhuan brick tea were evaluated by several in vitro experiments including DPPH assay, ABTS assay and FRAP assay with ascorbic acid as a positive control. It turned out that the different extracts from fuzhuan brick tea all showed certain antioxidant capacity, and the ethyl acetate extract showed highest antioxidant activities of scavenging DPPH and ABTS+radicals, with IC50values of0.043and0.027g-L-1, respectively (the positive control Vc showed IC50values of0.031and0.017g-L-1, respectively). A highly linear relationship was attained between total phenolics contents and antioxidant capacity, but the correlation coefficient between flavonoid contents and antioxidant capacity was not significant. These results indicated that total phenolics rather than flavonoids contributed significantly to the total antioxidant activity of fuzhuan brick tea.In addition, the antioxidant activities of compounds1,3,4,5,9,10,12,14,15,16,17,18,19,20,21,22,23from fuzhuan brick tea were also detected by DPPH assay and ABTS assay. The results indicated that compounds4,19,20,21,23own remarkable higher antioxidant activity than positive control Vc; the IC50of compound15was equal to Vc, so their antioxidant activity were nearly same. Compounds9and22exhibited remarkable greater antioxidant effects than Vc in DPPH scavenging assay, while not so good in ABTS assay; the antioxidant effect of compounds5,12,16and17in the two methods were not so good. Compounds1,3,10,14and18showed no antioxidant activity.