Comparative Study: Extraction Conditions and Antioxidant and Antibacterial activities of Gracilaria fisheri

Gracilaria fisheri (G. fisheri), sourced from the southern region of Thailand and recognized for its sulfated polysaccharides with diverse health benefits, underwent extraction under varying conditions by adjusting the ratio of water to ethanol and the duration of maceration. Six extraction conditions were systematically investigated, and their yields of extraction, sulfate content, antioxidant activity, and antimicrobial activity were compared. Among the conditions examined, the extraction utilizing solely water for a duration of 2 hrs. yielded the highest quantity (7.20±0.99 g) and highest sulfate content (215.86±2.67 µg/10 mg of crude extract). Furthermore, this extraction exhibited superior antioxidant activity as evidenced by the lowest IC50 values in DPPH (4.75±0.05 µg/mL) and ABTS (31.75±0.22 µg/mL) assays. Additionally, the extracts (10 mg/mL) manifested significant efficacy in inhibiting the growth of both Staphylococcus aureus (16.28±4.75 mm) and Staphylococcus epidermidis (15.33±3.27 mm) in comparison with the standard antibiotic, ciprofloxacin (5 µg), which exhibited inhibition zone diameters of 20.47±0.70 mm (Staphylococcus aureus) and 30.91±0.80 mm (Staphylococcus epidermidis). In conclusion, the most effective method for extracting G. fisheri is to solely utilize water for a duration of 2 hrs.