In order to develop new anti-photoaging agents, we examined the antioxidative activity and the inhibition effect of matrix metalloproteinase-1 (MMP-1) on the extracts of a marine product, Zostera marina L., which is known for its potent activity. Three compounds (compounds 1, 2, and 3) were isolated from an ethyl acetate (EtOAc) soluble fraction of the product; they were identified as apigenin-7 -O-$eta$-D-glucoside (1), chrysoeriol (2), and luteolin (3). These compounds were found to scavenge radicals and reactive oxygen species (ROS) and were measured to have $SC_{50}$/ values of 0.18 mM, 0.68 mM, and 0.01 mM against the 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical and 0.04 mM, 0.03 mM, and 0.01 mM against the superoxide radical in the xanthine/xanthine oxidase system, respectively. Compound 3 suppressed the expression of MMP-1 by up to 44％ at 4.0 $mu$M and inhibited the production of interleukin 6 (IL-6), which is known as a cytokine that induces MMP-1 expression. From these results, compound 3 and the other compounds were determined to have antioxidative activity and to inhibit MMP-1 expression. Thus, the three compounds are expected to be useful for preventing the photoaging of skin.