β-Carbolines are bioactive pyridoindole alkaloids occurring in foods, plants and the human body. Their activity as hydroxyl radical (OH) scavengers is reported here by using three different methods: deoxyribose degradation, hydroxylation of benzoate and hydroxylation of 2'-deoxyguanosine to give 8-hydroxy-2'-deoxyguanosine (8-OHdG) as assessed by RP-HPLC (MS). Fenton reactions (Fe(2+)/Fe(3+) plus H2O2) were used for OH generation, and the radical increased in the presence of ascorbic acid or 6-hydroxydopamine as pro-oxidants. β-Carbolines were scavengers of OH in the three assays and in the presence of pro-oxidants. Tetrahydro-β-carboline-3-carboxylic acids were active against the hydroxylation of 2'-deoxyguanosine. β-Carbolines reacted with hydroxyl radicals (OH) affording hydroxy-β-carbolines, whereas tetrahydro-β-carbolines gave oxidative and degradation products. On the basis of IC50 and reaction rates (k), β-carbolines (norharman and harman), and tetrahydro-β-carbolines (tetrahydro-β-carboline, 1-methyltetrahydro-β-carboline and pinoline) were good OH radical scavengers and their activity was comparable to that of the indole, melatonin, which is an effective hydroxyl radical scavenger and antioxidant.
Keywords: 1,2,3,4-Tetrahydro-beta-carboline (PubChem CID: 107838); 1,2,3,4-Tetrahydro-beta-carboline-3-carboxylic acid (PubChem CID: 98285); 1-Methyl-1,2,3,4-tetrahydro-beta-carboline (PubChem CID: 91522); 1-Methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (PubChem CID: 73530); 6-Hydroxydopamine (PubChem CID: 4624); 8-Hydroxy-2′-deoxyguanosine; Antioxidants; Ascorbic acid (PubChem CID: 54678501); Benzoate; Deoxyribose; Harman (PubChem CID: 5281404); Hydroxyl radical scavengers; Indoles; Melatonin; Melatonin (PubChem CID: 896); Norharman (PubChem CID: 64961); Pinoline (PubChem CID: 1868); Pyridoindoles; Tetrahydro-β-carbolines; β-Carboline alkaloids.
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