Dual Evaluation of Malva Extract in Eye-Drop Formulations: Antioxidant Efficacy and Physicochemical Properties Relevant to the Treatment of Dry Eye Disease.

Background/

Objectives

Dry eye disease (DED) is a multifactorial condition affecting the ocular surface. It is characterized by tear film instability, hyperosmolarity, inflammation, and oxidative stress. First-line treatment for DED relies on lubricating and hydrating eye drops, usually containing hyaluronic acid (HA), which supports tear film stability and epithelial healing. However, HA alone cannot correct oxidative stress, a key driver of cellular damage and inflammation in DED. Accordingly, this study aimed to evaluate the antioxidant capacity of Malva sylvestris tincture (MalvaT) and its physicochemical properties in experimental eye-drop formulations containing HA.

Methods

The antioxidant activity of reconstituted MalvaT lyophilisate (Malva) was assessed in cell-free assays against several oxygen radicals and in cell-based assays using the human HaCat keratinocyte cell line. The refractive index was measured in eye-drop formulations containing 0.15% or 0.3% HA and 0.5% MalvaT. Surface tension was assessed in eye-drop formulations containing 0.15% HA and increasing concentrations (0.25-2.0%) of MalvaT.

Results

Malva showed potent oxygen radical scavenging activity in both cell-free and cell-based assays, indicating its antioxidant capacity and the efficient cellular uptake of antioxidant components. The refractive indices of experimental eye-drop solutions containing HA and MalvaT were close to that of tear fluid (1.334). The surface tension of the experimental eye-drop formulations, while not impacted by 0.15% HA, was significantly reduced by increasing concentrations of MalvaT (p < 0.0001). At the concentration of 0.5% MalvaT, the mean surface tension was reduced from 68.17 mN/m (HA control) to 59.80 mN/m (HA + MalvaT), thereby bringing it closer to that of tear fluid.

Conclusions

This pre-clinical study suggests that combining the antioxidant properties of Malva tincture with the lubricating and hydrating effects of HA in eye-drop formulations exhibiting optimal rheological characteristics may offer a promising therapeutic approach for managing DED.