Vitamin C Stability Experiment with Ferulic Acid

It is interesting that your experiment showed faster yellowing in the Vitamin C solution containing Ferulic Acid compared to the one without. Based on the properties of the ingredients, here's a breakdown of why this might have happened:

Why the Ferulic Acid Solution May Have Yellowed Faster

1. Ferulic Acid's Natural Color: Ferulic Acid itself is typically a white to light yellow powder. When dissolved, it can impart a yellow color to the solution. This inherent color contributes to the overall yellow appearance, potentially making the solution look more yellow even if the Vitamin C degradation is similar or slightly slower than the control.
2. Solubility of Ferulic Acid: Pure Ferulic Acid is not easily soluble in water. While your formula includes Propylene Glycol, which can help with solubility, it's possible the Ferulic Acid wasn't perfectly dissolved or stable in your specific water/PG system. Poor solubility or stability of Ferulic Acid itself could lead to its own degradation or color change, contributing to the yellowing.
3. Synergy with Vitamin E is Key: The widely recognized stability benefit of Ferulic Acid for Vitamin C (L-Ascorbic Acid) is primarily observed when it is used in combination with Vitamin E (dl-alpha tocopherol). This combination creates a synergistic antioxidant network that is significantly more effective at protecting L-Ascorbic Acid from oxidation than either antioxidant alone. Your experiment tested Ferulic Acid in isolation (without Vitamin E). Without the synergistic effect of Vitamin E, Ferulic Acid alone may not provide sufficient or the expected level of stabilization for L-Ascorbic Acid, especially in a water-based solution where L-Ascorbic Acid is inherently unstable.

In essence, the yellowing you observed in the Ferulic Acid solution after 7 days is likely a combination of the natural color contribution of Ferulic Acid, potentially some degradation of Ferulic Acid itself, and the oxidation of L-Ascorbic Acid occurring because the crucial synergistic partner, Vitamin E, was absent.

Does Vitamin C E Ferulic Last Longer?

Yes, formulations combining Vitamin C (L-Ascorbic Acid), Vitamin E (dl-alpha tocopherol), and Ferulic Acid are known to have significantly improved stability and a longer shelf life compared to formulations with L-Ascorbic Acid alone in a water base.

The combination of these three antioxidants creates a powerful system that recycles and enhances each other's ability to neutralize free radicals, thereby protecting the highly unstable L-Ascorbic Acid from oxidation.

While the exact duration of the extended shelf life can vary depending on the specific formula concentration, packaging, and storage conditions (cool, dark storage is essential), this combination is a standard approach used in many commercial products to stabilize L-Ascorbic Acid and extend its potency. Specific data on exactly how much longer it lasts compared to a simple L-Ascorbic Acid solution is not universally fixed, as it depends heavily on the full formulation and testing conditions, but the improvement is generally substantial.