Modified Radical Scavenging and Antioxidant Activity Measurement of β-Carotene with β-Cyclodextrins Complexation in Aqueous Medium

In order to evaluate the antioxidant capacity/activity of beta-carotene (BC) in aqueous media, we investigated the inclusion complexes of BC with methyl-beta-cyclodextrin (Me-beta-CD), 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and 2-hydroxyethyl-beta-cyclodextrin (HE-beta-CD) that enhance water solubility and chemical stability. The inclusion complexes (monitored by FTIR) exhibited higher solubility than free BC, and phase solubility studies showed a linear increase in the solubility with the Me-beta-CD concentration. Cupric ion-reducing antioxidant capacity (CUPRAC), ABTS-persulfate, peroxyl and hydroxyl radical scavenging assays were applied. CD-complexed beta-carotene exhibited less effective antioxidative and radical scavenging than free BC dissolved in acetone. beta-Carotene showed the highest antioxidant capacity in the presence of HE-beta-CD, and the lowest with Me-beta-CD, probably due to the deeper and more hydrophobic cavity of the latter. We believe that this is the first report on devising simple spectrophotometric methods for the wholistic assessment of antioxidant activity/capacity, hydroxyl and peroxyl radical scavenging activity of beta-carotene in aqueous solution with CDs.