Antioxidant Activity and Tyrosinase Inhibition of Red Seaweed (<i>Kappaphycus alvarezii</i>) Extracted Using Different Solvents

The common type of seaweed in Indonesia is Kappaphycus alvarezii . Since this seaweed thrives in tropical waters, antioxidants are suspected to protect it from the adverse effects of UV radiation. Studies also suggest that extracts from this seaweed can also protect skin from damage caused by UV exposure by inhibiting tyrosinase activity. This study aimed to determine the antioxidant activity and tyrosinase inhibition of K. alvarezii extracted using the maceration method with three different solvents: 70% ethanol, ethyl acetate, and n-hexane. K. alvarezii extracts are active in the antioxidant mechanism through electron transfer, shown by the result of the FRAP antioxidant capacity of ethyl acetate extract (36,550±0,127 μmol TE/g CE). The 70% ethanol extract demonstrated the highest DPPH antioxidant capacity (9,785±0,084 μmol TE/g CE) and showed no significant difference with ethyl acetate extract (9,540±0175 μmol TE/g CE). The 70% ethanol extract also exhibited the highest inhibition of lipid peroxidation (88,663±0,246%) at 10 mg/mL. All extracts showed tyrosinase inhibition but to a lesser extent than that of the positive control kojic acid. The inhibition percentages at 10 mg/mL were respectively 70% ethanol extract (43,016±3,064%), ethyl acetate extract (41,474±1,365%), and n-hexane extract (37,515±0,467%). This study concluded that K. alvarezii extracts can be used as an antioxidant and tyrosinase inhibitor when extracted using ethanol or ethyl acetate.