Abstract

Tea which is one of the most widely consumed beverages after water, contains diverse polyphenols such as flavonoids and other catechins. These polyphenols confer anti-oxidant properties on tea with the capacity to slow down or prevent oxidation of other molecules. Ten instant tea brands were tested for purity and anti-oxidant properties. Qualitative tests for anti-oxidant activities were visualized by thin layer chromatography (TLC) and DPPH (2, 2-diphenyl-1-picrylhydrazyl) spray. The extent of purity was determined by tests for extractable matter, ash values and moisture content whereas total polyphenolic content was determined by the colorimetric method using Folin-Ciocalteu reagent. Antioxidant activity was determined by DPPH free radical scavenging assay using rutin, vitamin C and gallic acid as standards. The test with TLC-DPPH spray showed that all ten brands had anti-oxidant components and the tea with the highest total phenolic content had a value of 360.62 ± 31.47mg GAE/g whereas the lowest was 150.76 ± 23.13mg GAE/g in contrast to 33.24 ± 15.89 and 6.47 ± 1.20mg RE/g for flavonoid content. The tea (black tea) with the most potent anti-oxidant activity had a potency value of 5.90 while the least potent (green tea) had a value of 4.20. The results are suggestive of good antioxidant properties of instant tea.

Key words: Instant tea, DPPH, anti-oxidant assay, polyphenol and flavonoid contents, radical scavenging