A Rapid and Sensitive In vitro Method to Ascertain Antioxidative Capacity*

By: Hongbo Zhai, MD, and Howard I. Maibach, MD, University of California San Francisco

Posted: January 29, 2010, from the February 2010 issue of Cosmetics & Toiletries.

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Antioxidant samples: A solution of 3% NAOC in water was prepared (v/v). In addition, 1 g of idebenone was mixed with 100 mL of methanol (w/v). As noted, a standard curve was established with a series concentrations using these samples with synthetic vitamin E.

Results
Results of the solubility test indicated that the ACL reagent 1 was suitable for both test materials, hence it was used for this study. The NAOC retained a wide solubility range: from the hydrophilic solvent and ACW reagent 1, to the five liphophilic solvents tested. The solubility range of idebenone, however, was relatively narrow.

As far as the standard calibration curve for vitamin E (see Figure 1), the X and Y axis reciprocal and linear regression followed: 1/Y(X) = 94.69251 * and (1/X)2 + 53.56752 * (1/X) + 0.57010; R2 = 0.9938.

Antioxidant capacity: The quantity of antioxidant capacity measured for the 3% NAOC and 1% idebenone were 525 ± 23 (nmol) and 213 ± 14 (nmol), respectively; these are equivalent to the antioxidant activity of synthetic vitamin E. The 3% NAOC, however, showed significant (p < 0.0001) antioxidative capacity and measured nearly 2.5 times stronger than the 1% idebenone.

Discussion
This study demonstrates that the antioxidant capability of 3% NAOC as a superoxide anion radical quencher, as measured by photochemiluminescence, exceeded idebenone by a factor of 2.5. One possible explanation for this result could be a synergistic effect between the NAOC plant extracts, which include known antioxidants such as anthocyanins, ferulic acid, caffeic acid and other polyphenols. This combination could generate benefits beyond that of a single antioxidant.