Profiling of bioactive compounds and antioxidant activity of aquatic weed Ipomoea aquatica

Water spinach, Ipomoea aquatica, is a common semi-aquatic weed that is used as an ingredient in fish feed to support its growth and defence system. The present study aimed to identify and quantify bioactive polyphenols through HPLC-DAD (High Performance Liquid Chromatograpgy - Diode Array Detector) analysis and to evaluate the antioxidant activity of the aquatic weed I. aquatica available in Bangladesh. Different bioactive phytochemical groups were qualitatively appraised in crude ethanol extract, aqueous and n-hexane fractions of water spinach. The total polyphenol and flavonoids content were spectrophotometrically discerned using Folin-Chiocalteu and aluminium chloride, respectively. Bioactive compounds of the extracts were identified by the HPLC-DAD method. Furthermore, 2,2-diphenyl-1-picryldydrazyl (DPPH) and hydroxyl-radical scavenging and reducing power assays were followed to assess antioxidant activity. The experimental extracts confirmed the presence of different bioactive phytochemical groups. The crude extract contained the highest content of both polyphenol (94.93 mg gallic acid (GA) equivalent per gram dry extract) and flavonoids (373.30 mg quercetin equivalent per gram dry extract). Besides, in HPLC (High Performance Liquid Chromatogrphy) analysis, ellagic acid was present at the highest concentration both in crude (337.26 mg/100 g dry extract) and aqueous (280.06 mg/100 g dry extract) extracts. However, the n-hexane fraction only contained GA (13.91 mg/100 g dry extract). Also, some other bioactive polyphenols were identified in crude and aqueous fraction extracts. The crude extract revealed superior antioxidant activity in DPPH (Half maximal inhibitory Concentration (IC50) = 149.30 +/- 1.43 mu g/ml) and hydroxyl radical scavenging assays (IC50 = 327.257 +/- 1.36 mu g/ml) in comparison to the rest of the extracts. Furthermore, all of the extracts showed dose-dependent reducing power activity. HPLC-identified bioactive compounds may be responsible for antioxidant activity. Because of these identified compounds, I. aquatica holds the potential feed ingredient in aquaculture.