A comparison of the hydroxyl radical scavenging properties of the shark bile steroid 5β‐scymnol and plant pycnogenols

The hydroxyl radical (OH·) quenching abilities of the following compounds were compared in the deoxyribose degradation system (initiated by the ferrous‐ascorbate Fenton reaction): (a) 5β‐scymnol, the hepatoprotective shark bile sterol, and its mono‐ and di‐sulfate esters; (b) three marketed pycnogenol preparations (syn: proanthocyanidin ‐ natural plant‐derived polyphenolic bioflavonoids) extracted from pine tree (Pinus maritima) bark and grape (Vitis vinifera) seeds; and (c) two known hydroxyl radical scavengers, dimethyl sulfoxide and mannitol, and the peroxyl radical scavenger TroloxTM (the α‐tocopherol analogue). 5β‐scymnol was a more potent OH· quencher than dimethyl sulfoxide, mannitol and Trolox, and markedly more potent than the pycnogenol preparations. Increased sulfation of 5β‐scymnol progressively reduced its free radical scavenging activity, thus clearly attributing the potent OH· quenching properties to its novel tri‐alcohol‐substituted aliphatic side chain. The favourable interaction of these bile steroids with reactive oxygen species in an aqueous environment, makes them attractive candidates for evaluation as protective agents against disorders in which oxidative stress is implicated.