2.6.1. Elastase Inhibition

The antiwrinkle potential of the *S. perfoliata* was tested using the elastase inhibition assay as described by Aumeeruddy et al. [18]. The reaction mixture contained 100 mM Tris buffer (pH 8.0), 0.5 M HCl and the ethanolic extract of *S. perfoliata*. The test concentration ranged between 3.13 and 250 μg/mL for the extract and the positive control (ursolic acid). Porcine pancreatic elastase (PPE) (5 mM, 0.02 mL) was added to the reaction mixture and incubated for 15 min at 37 ◦C followed by the addition of the substrate, 4 mM N-succinyl-(Ala)3-p-nitroanilide. The change in the absorbance of the reaction mixture was measured kinetically at 405 nm for 15 min at 37 ◦C using KC Junior software and a BIO-TEK Power-Wave XS multiwell plate reader (A.D.P, Weltevreden Park, South Africa). One unit of elastolytic activity is defined as the release of 1 μM of p-nitroaniline/min from N-succinyl-(Ala)3-p-nitroanilide. The IC50 value of *S. perfoliata* was calculated.
