Effect of extraction conditions on measured total polyphenol contents and antioxidant and antibacterial activities of black tea
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Tarih
2007Yazar
Türkmen, Nihal
Velioğlu, Yakup Sedat
Sarı, Ferda
Polat, Gökçe
Üst veri
Tüm öğe kaydını gösterÖzet
Black tea was extracted for 2, 8 and 18 h with absolute acetone, N,N-dimethylformamide
(DMF), ethanol and methanol and their 50% aqueous solutions. The extracts
were screened for total polyphenol contents, antioxidant and antibacterial activities. The
polyphenol content of the extracts was found to be in the range of 0.44-114.01 mg gallic
acid equivalents (GAE)/g dry weight tea, depending on the solvent used and the length of
the extraction process. In general, aqueous acetone or DMF extracts displayed the highest
polyphenol contents and antioxidant activity, while absolute acetone was the least
efficient solvent. Antioxidant activities of tea extracts tested using the reducing power
and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical methods ranged from 0.09 to 1.18 and
from 2.60 to 95.42 %, respectively, depending on the extraction conditions and the
antioxidant activities correlated well with the polyphenol concentrations. Aqueous
solvent black tea extracts also possessed antibacterial activity, depending on the solvent
used and bacterial species tested. Staphylococcus aureus was found to be the most
sensitive to all tea extracts, except for the methanol extract. Tea extracts were not
effective against Y. enterocolitica, L. monocytogenes and E. coli O157:H7.
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