Effects of pH and Temperature on the Profile of Bioactive Compounds in Seaweed: A Marine Chemistry Perspective

Abstract

The red seaweed Eucheuma cottonii is a coastal biological resource rich in bioactive compounds such as phenolics, antioxidants, and soluble polysaccharides (carrageenan), which hold potential for applications in the food, pharmaceutical, and cosmetic industries. Optimization of extraction conditions is essential to maximize the utilization of these compounds. This study aims to examine the effects of temperature and pH on total phenolic content, antioxidant activity (DPPH), and soluble polysaccharides in E. cottonii collected from Takalar, South Sulawesi. A factorial 3 × 3 laboratory experimental design was applied, involving variations in temperature (40°C, 60°C, 80°C) and pH (4, 7, 9). Analyses included total phenolic content using the Folin–Ciocalteu reagent, antioxidant activity through the DPPH method, and soluble polysaccharide content using gravimetric methods. The results showed that 60°C and pH 7 yielded the highest values for all three parameters: total phenolics 28.3 ± 1.4 mg GAE/g, antioxidant activity 65.4 ± 2.1% inhibition, and soluble polysaccharides 23.7 ± 1.1%. ANOVA indicated a significant interaction effect (p < 0.05) between temperature and pH on all measured parameters. It is concluded that the combination of 60°C and neutral pH is the optimal condition for extracting bioactive compounds from E. cottonii, and can serve as a reference for developing sustainable natural products based on red seaweed.