The Effect of Variety and Fertilizer Application on Functional Properties of ‘Mukunuwenna’ (Alternanthera sessilis)

The study investigated the functional properties, such as antioxidant activity, phenolic content and ascorbic acid content of the popular leafy vegetable, Alternanthera sessilis (‘Mukunuwenna’). Two varieties such as Piliyandala and Colombo Selection grown under four different fertilizer application types namely, Inorganic fertilizer mixture recommended by the Department of Agriculture (Urea 9 kg/1000 m2 , MOP 13.5 kg/1000 m2 , TSP 10 kg/1000 m2 ), Integrated treatment [mixture of inorganic (Urea, MOP and TSP) and organic fertilizer (cattle manure and gliricidia)], Organic fertilizer (cattle manure and gliricidia) and Homescale cultivation (No fertilizer) were used. Antioxidant activity (AOA) of the methanolic leaf extract was determined by using 2, 2- diphenyl-1-picryl hydrazyl (DPPH) Radical Scavenging Assay. Phenolic content (PC) and ascorbic acid content (AAC; IC50 value) were measured by the Folin-Ciocalteu method and 2, 6-Dichlorophenol-indophenol titration method, respectively. A 2-factor factorial experiment was used in the study. Varieties Piliyandala (7.92 mg/mL) and Colombo Selection (9.50 mg/mL) did not differ in their AOA while variety Colombo Selection recorded a higher phenolic content (472.67 mg GAE/100 g) compared to Piliyandala (343.83 mg GAE/100 g). Ascorbic acid contents of Piliyandala and Colombo Selection varieties were 11.48 and 12.44 mg/100 mg, respectively. Home-scale cultivation and organic fertilizer treatment resulted in significantly higher (p˂0.05) AOA of 3.364 and 8.034 mg/mL and PC of 410.87 and 404.99 mg GAE/100 g, respectively. Organic fertilizer application significantly increased (p˂0.05) the antioxidant activity of variety Piliyandala but not in Colombo Selection. Results indicated that, A. sessilis grown with inorganic fertilizer and a mixture of inorganic and organic fertilizer contained significantly lower antioxidant levels and phenolic contents compared to those grown organically and in home-scale without fertilizer application.