The effect of crude betalains from beet root on (in - vitro) hypochlorous acid induced low density lipoprotein oxidation

Abstract

Studies have shown a decreased risk of atherosclerosis linked to the intake of fruits and vegetables rich in bioactive phytonutrients. This study investigated the effect of crude beet root betalains on low density lipoprotein (LDL) oxidation induced by hypochlorous acid (HOCl). Crude betalains antioxidant potential was determined by use of 2, 2 – diphenyl - 1 – picrylhyrayl radical (DPPH assay) and was compared to lycopene and ascorbic acid. HOCl oxidizing ability and betalains antioxidant capabilities were determined by incubating heparin precipitated LDL from rat (Rattus norvegicus) blood serum with varying concentrations of HOCl or 10μM HOCl plus crude betalains at 37 oC in phosphate buffer saline (pH 7.4). The oxidation process was monitored by measuring conjugated dienes formed at 234 nm at 5 minute intervals over a 3 hour period using a Spectrum lab Gold S54T UV- Visible spectrophotometer. Lycopene was used as control. DPPH assay results indicated significant (p < 0.05) variation in antioxidant activity between crude betalains, lycopene and l - ascorbic acid and amongst varying concentrations of each sample. Generally, crude betalains had greater antioxidant ability than both lycopene and l – ascorbic acid. At 160μM concentration, crude betalains, lycopene and ascorbic acid had an antioxidant activity of 99%, 61.7% and 77.8% respectively. Tests on the oxidizing potential of HOCl revealed significant (p < 0.05) increase in LDL oxidation with time for HOCl concentrations 10μM, 30μM and 50μM but a significant (p < 0.05) drop in LDL oxidation activity below that of 10μM HOCl for HOCl concentrations 70μM and 100μM. At 50μM HOCl, LDL oxidation activity was 2.43% higher than that at 10μM HOCl and 1.46% higher than that at 30μM HOCl. However, at 70μM and 100μM HOCl, a drop in LDL oxidation activity of 1.64% and 1.85% respectively, was recorded compared to that of 10μM HOCl. At 100μM crude betalains showed significant (p < 0.05) inhibition of 10μM HOCl induced LDL oxidation. However, lycopene’s ability to inhibit LDL oxidation surpassed that of crude betalains at all concentrations. Crude betalains of 100μM, 50μM and 10μM concentration registered a drop in LDL oxidation activity of 8.4%, 3.9% and 1.5% respectively against the control (10μM HOCl) while lycopene of similar concentrations had a drop of 39.9%, 27.6% and 19.5% respectively, against the control. Results confirm that crude betalains possess significant antioxidant ability and proposes that betalains may be useful in the reduction of in - vivo LDL oxidation.