Antioxidation and Radical Scavenging Activities and Tyrosinase Inhibition of Fresh Tea Leaves, Camellia Sinensis

Assam tea, a common name of Camellia sinensis var. assamica, is grown in the northern part ofThailand. Fresh Assam tea leaves have been consumed by the local Thai people as well as Burmese.Reflux extractions with several types of solvents, and selected solvent with ultrasonic assistedextraction were studied for the extraction efficiency. The extracts were determined for antioxidativeactivities, total phenolic acids and tyrosinase inhibition. It was found that methanolic ultrasonicassisted reflux extraction (methanolic UAE) was appropriate for fresh Assam tea extraction as it gavehigher active components than that of the extraction without ultrasonic assisted one. The methanolicUAE gave the highest total phenolic content by Folin–Ciocalteu’s method at 105.5±2.4 milligrams ofgallic acid equivalent per gram of dried weight (mgGAE/g DW), the antioxidant activities expressedas IC50 values; the concentration of sample required for 50% inhibition of 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt cation radical (ABTS +) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH ) were 35.5 and 48.8 ppm, respectively. The inhibitory effect ontyrosinase activity; IC50 value, was 22.0 ppm.