Sunphenon (BG), a polyphenol rich fraction of green tea, which exhibits potent anti-oxidant and anticancer activity, was examined for its ability to react with free radicals and singlet oxygen using fast reaction kinetic tools. Employing nanosecond pulse radiolysis technique, hydroxyl (^•OH) radical scavenging ability of sunphenon was compared with a standard thiocyanate anion, which indicated that sunphenon reacts with ^•OH produced a transient absorption spectrum with l_max at 380 and 480 nm, which is characteristic of gallocatechin phenoxyl radicals. It also scavenges singlet oxygen very efficiently and decreases its life time from 64 to 21 ms on addition of 4.5 mg/mL of sunphenon and the nitric oxide (NO), superoxide (O₂ ^•-) and hydroxyl radical scavenging actions of sunphenon were estimated by steady state methods. Sunphenon showed higher reactivity towards 2,2`-diphenyl-1-picrylhydrazyl radicals as compared to ascorbic acid with an IC50 value of 6.9 mg/mL and possesses ~89 % ascorbate equivalents in scavenging 2,2`-azinobis (3-thylbenz-thiazoline-6-sulfonic acid^•-. Cyclic voltammetry of sunphenon showed two oxidation peaks with peak at a potential of 0.33 V and 0.74 V, indicative of its redox potential. Sunphenon protects peroxide-induced damage to mitochondrial superoxide dismutase (SOD) and inhibits radiation induced DNA damage in plasmid pBR322 DNA. Based on these studies, it is confirmed that sunphenon is one of the richest sources of free radical scavengers. The 3 free radical scavenging ability of sunphenon is as high as any pure compound, a property which is not seen in many extracts.