Profiling of bioactives and in vitro evaluation of antioxidant and antidiabetic property of polyphenols of marine algae Padina tetrastromatica

Abstract

This study aimed to characterize and quantify the phenolics, hydrocolloids, lipids and carotenoids and to study antioxidant and antidiabetic property of phenolics of marine brown algae Padina tetrastromatica. Extraction using 1% acidic methanol yielded 3.6mg/g total polyphenol, 2.86mg/g flavonoid and 21.8μg/g tannin. Ultra high performance liquid chromatography-high resolution mass spectrometry/mass spectrometry (UPLC-HRMS/MS) analysis resulted in free phenolics: danshensu, quercetin derivative, luteolin, genistein, and hydroxyl-ferulic acid derivative; bound phenolics: luteolin, acacetin derivative, dioxinodehydroeckol derivative, and rosmarinic acid. The radical scavenging activities of the phenolic extracts were 10.83±2.81 and 58.85±2.28μg/mL by the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) methods, respectively. The total antioxidant activity of seaweed phenolics was 29.13±2.31μg of ascorbic acid equivalent, and the reductive capability was 32.39±3.11μg of quercetin equivalent. In addition, the extract exhibited a half maximal inhibitory concentration (IC50) of α-amylase (47.2±2.9μg) and α-glucosidase (28.8±2.3μg) inhibitory activities. Fatty acids methyl-palmitate and methyl-palmitoleate were present in neutral-, glyco-, and phospholipid fractions of total lipids (0.82%). The seaweed is rich in bioactives fucoxanthin (96.66%), polysaccharides (mg/g dry wt.) laminarin (14.78), fucoidan (1.38) and alginate (70.16) respectively. Based on the nutraceutical density, there will be potential food and pharma applications for P. tetrastromatica.