Antiradical, antimicrobial and cytotoxic activities of commercial beetroot pomace

Abstract

The by-product of food processing is often utilized as feed, and for the preparation of dietary fiber and biofuel. However, these products are also promising sources of bioactive antioxidants and color giving compounds, which could be used as additives in the food, pharmaceutical and cosmetic industry. The aim of this study was to investigate the phytochemical profile, and the antiradical, antimicrobial and cytotoxic activities of industrial beetroot pomace extract (BPE). The content of phenolics (45.68 mg gallic acid equivalents g⁻¹), flavonoids (25.89 mg rutin equivalents g⁻¹) and betalains (4.09 mg betanin g⁻¹; 7.32 mg vulgaxanthin I g⁻¹) were determined spectrophotometrically. The antiradical activity on DPPH (EC₅₀^DPPH˙ = 0.0797 mg ml⁻¹), hydroxyl (EC₅₀˙^OH = 0.0655 mg ml⁻¹) and superoxide anion (EC₅₀^O2˙⁻ = 1.0625 mg ml⁻¹) radicals were measured by electron spin resonance (ESR) spectroscopy. The antimicrobial activity was determined using the agar-well diffusion method. Gram(−) bacteria (Salmonella typhimurium, Citrobacter freundii) and Gram(+) bacteria, (Staphylococcus aureus, Staphylococcus sciuri, Bacillus cereus) showed high susceptibility, while yeasts and moulds were resistant. BPE exhibits cytotoxic properties against Ehrlich carcinoma (EAC) cells in vivo due to induction of oxidative stress. The largest decreases in EAC cell numbers were observed in the pre-treated male (approximately 53%) and female (approximately 47%) mice, and also the EAC cell viability was decreased after administration of BPE. The activities of the antioxidant enzymes, xanthine oxidase (XOD) and peroxidase (Px), were significantly different between the untreated EAC control group and all other groups that were treated with BPE. The XOD and Px activities were very low in untreated malignant cells, but increased significantly after administration of BPE. Our results show that BPE holds promise in the food industry as a source of bioactive compounds.