Pigment identification, nutritional composition, bioactivity, and in vitro cancer cell cytotoxicity of Rivina humilis L. berries, potential source of betalains

Ripened berries of Rivina humilis L. (pigeon berry) were investigated for pigment and nutritional composition, in vitro bioactivities, and cancer cell cytotoxicity of its extracts. Ten betalain pigments (total content-0.35 g/100 g fresh weight, and 1.7 g/100 g dry weight) with high level of betaxanthins were characterised. Carbohydrates (6.2 g), proteins (1.1 g), lipids (0.7 g), phenols (105.7 mg gallic acid equivalent), niacin (5.3 mg), and total tocopherols (0.77 mg) in 100 g fresh weight were observed. Antioxidant bioactivity of MeOH extract (maximum at 100 μg/mL) against OH and β-carotene oxidation was studied. The extract (1000 μg/mL) effectively protected kidney lipid peroxidation compared to butylated hydroxy anisole. Betalains rich extract, and purified betacyanins and betaxanthins revealed EC50 against DPPH (51.0, 0.29, 0.11 μg/mL), and reducing power (39.3, 2.79, and 1.34 μg/mL) which was higher than that of gallic acid and ascorbic acid. In vitro cancer cell cytotoxicity was assessed through MTT assay on HepG2 cells after exposing to betalains rich extract, betacyanins and betaxanthins for 24 h; only betaxanthins exhibited cytotoxicity (EC50 12.0 μg/mL). After 48 h of exposure, betacyanins and betaxanthins showed elevated cytotoxicity.

► Ten betalains were identified in Rivina humilis berries (total content-0.35% fw). ► Nutrient composition including vitamins and phenols were determined. ► Methanol extract showed strong DPPH and OH scavenging activity and reducing power. ► MeOH extract protected β-carotene oxidation and lipid peroxidation. ► Crude extract and betacyanins were not cytotoxic, whereas betaxanthins were toxic.