Superoxide anion scavenger properties of sparteine, a quinolizidine alkaloid from Lupinus

Peroxidase activity in lupin (Lupinus albus cv. Multolupa) hypocotyls is located, as are quinolizidine-type alkaloids, in epidermal tissues. Since these alkaloids have been shown to suffer a rapid turnover and degradation in lupin tissues, the ability of sparteine (a typical tetracyclic quinolizidine alkaloid) and cytisine (a typical tricyclic alpha-pyridone quinolizidine alkaloid) to act as peroxidase substrates was studied. However, neither alkaloid was oxidized by a partially purified lupin peroxidase fraction, or by horseradish peroxidase, as was ascertained by spectrophotometric and GC-MS studies. Likewise, these quinolizidine-type alkaloids were not substrates of a laccase of fungal origin. However, sparteine, unlike cytisine, acted as a superoxide scavenger, when the superoxide anions were generated in a phenazin methosulphate-NADH system and determined by the superoxide dismutase-sensitive reduction of nitroblue tetrazolium. The IC50 value was 2.0 mmol/L. These results are discussed in the light of a possible protective role against oxidative damage of sparteine in Lupinus.