One new flavonoid glycoside, 3-O-kaempferol 4-O-(galloyl)-beta-D-glucoside, one new bergenin derivative, 11-0-caffeoylbergenin, along with other known flavonoids and phenolic derivatives, were isolated from the leaves of Securinega virosa. Their structures were established on the basis of detailed spectral analysis. In vitro biological analysis of the isolated compounds showed that they were able to quench DPPH radicals and had a direct scavenging activity on superoxide anion. Kaempferol 3-O-(4-galloyl)-beta-D-glucopyranoside (1), 11-0-caffeoylbergenin (2), and glucogallin (6) exhibited the highest antioxidant capacity, being also able to modulate hydroxyl radical formation more efficiently than the other compounds, acting as direct hydroxyl radical scavengers and chelating iron.