Topical Activity of Ascorbic Acid: From in vitro Optimization to in vivo Efficacy

Abstract

We present here a new cosmetic formula system containing 3% ascorbic acid based on an optimized oil-in-water (O/W) emulsion. This formulation demonstrated a good long-term stability of the active ingredient and also of the emulsion itself. It could be deduced from in vitro release studies that this O/W emulsion enabled a better release of the hydrophilic active agent than an alternative W/O emulsion. By measuring the ultraweak photon emission, which is a well-established parameter for the oxidative stress in the skin, the high in vivo antioxidant capacity of 3% ascorbic acid was demonstrated after 1 week of product application. This placebo-controlled study also proved that ascorbic acid in an O/W cream reduced oxidative stress in human skin significantly better than the derivative sodium ascorbyl-2-phosphate, a more stable vitamin C replacement commonly used in cosmetic formulations. With increasing age, the number of papillae in the epidermal-dermal junction zone in human skin are reduced. This implies a possible consequence of reduced mechanical resistance of the skin and impaired supply of the epidermis with nutrients. In a 1-month placebo-controlled study on 25 human volunteers, a significant increase in the number of dermal papillae after application of the 3% ascorbic acid cream was demonstrated, using a confocal laser scanning microscope. Fine lines and wrinkles are a characteristic sign of aged and especially photo-aged skin. Application of 3% ascorbic acid in a 12-week placebo-controlled usage study indicated a significant reduction of facial wrinkles. Altogether, 3% ascorbic acid in a cosmetic O/W emulsion has been shown to be appropriately stable and to enable a good release of the active agent in vitro as a precondition for a high efficacy in vivo. Application in vivo resulted in a significant reduction of oxidative stress in the skin, an improvement of the epidermal-dermal microstructure and a reduction of fine lines and wrinkles in aged skin. These results were received within a relatively short period of time of product application.

Photostability and Interaction of Ascorbic Acid in Cream Formulations

“…It is sensitive to air and light (2,3) and is degraded by chemical (4) and photochemical oxidation (5)(6)(7)(8)(9)(10). Ascorbic acid is an ingredient of antiaging cosmetic products (11)(12)(13)(14)(15) and exerts several functions on the skin as collagen synthesis, depigmentation, and antioxidant activity (16). As an antioxidant it protects skin by neutralizing reactive oxygen species generated on exposure to sunlight (17).…”

Objective and Self-Perceived Facial Skin Status Using Whitening Efficacy of Cosmetic Products on Taiwanese Women

“…In addition, antioxidants are becoming increasingly important in whitening cosmetics according to their anti-inflammatory effects. Particularly, 3% sodium ascorbyl phosphate is a stable antioxidants in a cosmetic oil-in-water emulsion and enable a good release of the active agent in vitro as a precondition for a high efficacy in vivo [21] [22]. In present study, the whitening efficacy products contains both tranexamic acid and sodium ascorbyl phosphate active ingredients were provided participants, and then observing the changes in self-perceived and objective facial skin status.…”

Dermal and Transdermal Delivery of Active Substances from Semisolid Bases

“…Hydrogels are not proper bases for substances that are susceptible for oxidation in aqueous media (e.g. ascorbic acid) [30] . In contrast, anhydrous PEG ointments may provide increase in the stability of these substances (e.g.…”

“…The gelling agents increase the viscosity of the external phase and thus stabilize the emulsion and adjust the consistency of the semisolid base [20] . The use of gelling agents may enable to obtain stable emulsions without using typical emulsifiers [30] . Bigel is a mixture of a hydrogel and an oleogel and may be obtained without using emulsifiers [20] .…”