Nutritional Composition and Bioactive Properties of Four Duckweed Varieties in Sri Lanka

Abstract Duckweed is well known for its high protein content and is gaining attention as a sustainable food source due to its rapid growth and excellent nutritional properties. This study on four duckweed varieties in Sri Lanka; Spirodela polyrhiza (SP), Lemna mino r(LM), Lemna perpusilla (LP), and Landoltia puntata (LaP) revealed their nutritional composition and some bioactive properties. The carbohydrate, protein, fat, ash, and crude fiber content in these duckweed varieties ranged from 5.26–9.49%, 17.34–26.45%, 3.69–3.92%, 8.03–9.55% and 5.26–9.49% (DW), respectively. K, Na, and Ca content varied from 45.62–20.17 mg/g, 5.61–37.73 mg/g, and 11.03–25.46 mg/g, respectively. High levels of omega-3 fatty acids (44.42–50.38%) were also found. FTIR analysis showed five distinct absorption bands associated with amides and carbohydrates. Among the varieties, Spirodela polyrhiza and Landoltia puntata demonstrated significant (P ≤ 0.05) α-amylase inhibition (IC₅₀ = 0.14 µg/mL), while Spirodela polyrhiza exhibited the highest (P ≤ 0.05) lipase inhibition (IC₅₀ = 1.39 µg/mL). Additionally, Spirodela polyrhiza showed notable inhibition (P ≤ 0.05) against A. niger and E. coli, and Landoltia puntata showed notable inhibition against (P ≤ 0.05) C. albicans, A. niger, and S. aureus. Rutin content is relatively more affluent than the other polyphenols analyzed (2.9612–3.0588 µg/mg DM). These duckweed varieties showed low to moderate toxicity (LC50 > 4000 ppm), highlighting their potential as nutrient-dense food sources with therapeutic properties.