Phytochemical Content and Toxicity Test of Kappaphycus Alvarezii Hot Water and Methanol Using BSLT Method

Investigating both the beneficial bioactive compounds and the potential toxicity of seaweed extracts provides crucial information to guide their development for nutritional, antioxidant activity, and even cytotoxicity against cancer cells. This study investigated the toxicity and phytochemical composition of hot water and methanol extracts of Kappaphycus alvarezii using a brine shrimp lethality test (BSLT) with Artemia salina larvae. K. alvarezii samples were extracted using hot water and methanol, and the extracts were subjected to phytochemical screening and toxicity testing. The hot water extract yielded 8.4%, comprising alkaloids, saponins, and flavonoids, whereas the methanol extract yielded 2.4%, consisting of alkaloids and saponins. The BSLT results showed that larval mortality increased with higher extract concentrations, indicating a dose-dependent toxicity. Probit analysis revealed LC₅₀ values of 180.90 µg/mL for the hot water extract and 961.97 µg/mL for the methanol extract, classifying both as toxic according to Meyer's toxicity categories. The hot water extract demonstrated higher toxicity, potentially owing to its higher yield and presence of flavonoids. The bioactive compounds in K. alvarezii extracts, such as alkaloids, saponins, and flavonoids, may contribute to their toxic effects on A. salina larvae. These findings suggest that K. alvarezii extracts have potential applications as antitumor and antibacterial agents. Antibacterials should be further explored for their immunostimulatory properties in aquaculture.