Autographic Assay for the Rapid Detection of Antioxidant Capacity of Liquid and Semi-solid Pharmaceutical Formulations Using ABTS•+ Immobilized by Gel Entrapment

An autographic assay suitable for the detection of antioxidant compounds in a complex matrix (liquid and semi-solid pharmaceutical formulations) or in isolated compounds was described. The preformed radical monocation of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(center dot+)) was generated by oxidation of ABTS with potassium persulfate and reduced in the presence of hydrogen-donating antioxidants. For a further comparative estimation of its applicability and sensitivity, different medicinal plant extracts, hydrogels and antioxidant compounds were dot seeded or chromatographed on silica gel (TLC) and revealed with ABTS(center dot+) solution (System I) or ABTS(center dot+) immobilized by gel entrapment (System II). Both systems were effective and able to detect antioxidant activity in a micromolar range in seconds. System II was more sensitive and reproducible than System I. This micromethod is quick, inexpensive, and particularly helpful whether it works with numerous samples or on a small scale.