The results of the present work indicated that the methanol extract of H. valentiae was a fairly active scavenging assay system. The present findings seem promising to facilitate further experiments on the identification and characterization specific of compounds which are responsible for the relatively high antioxidant activities. Importantly, this research may contribute to a rational basis for the application of marine algal extract in possible therapy of diseases associated with oxidative stress and further supported that the antioxidant-rich extracts or fractions may be used as a dietary supplement, promoting good health.