Investigation of ex vivo Skin Penetration of Coenzyme Q10 from Microemulsions and Hydrophilic Cream

Introduction: Coenzyme Q10 (CoQ10) has been widely used in topical and cosmeceutical products due to its cutaneous antioxidant and energizer effects. CoQ10 is found in a higher concentration in the epidermis compared to dermis. The epidermal level of CoQ10 can be reduced due to several factors such as skin UV irradiation and photoaging. Various dermal nano-formulations have been investigated to overcome the skin barrier and enhance the poor penetration of CoQ10. The nanocarriers are designed to target and concentrate the CoQ10 in the viable epidermis. Most of these studies, however, failed to show the depth and extent of penetration of CoQ10 from the various carrier systems. Objective: The distribution of CoQ10 across the various skin layers has to be shown using skin slices representing the different skin layers. Methods: To realize this objective, a sensitive and selective HPLC method was developed and validated for the quantification of CoQ10 in the different skin slices. The method applicability to skin penetration (using excised human skin) as well as stability studies was investigated using CoQ10-loaded lecithin-based microemulsion (ME) and hydrophilic cream formulations. Results: It could be shown that the highest concentration of CoQ10 in the viable epidermis, the target skin layer for CoQ10, was observed after application of the CoQ10 in the hydrophilic cream. This cream contains 10% of 2-ethylhexyl laurate which works obviously as a penetration enhancer for CoQ10. In contrast, the penetration of CoQ10 was lower from the ME. Just in the deeper dermis, a certain amount of CoQ10 could be detected. Conclusions: The HPLC method quantified the trace quantities of the CoQ10 distributed across the various skin layers and, hence, can be used to investigate the skin penetration of CoQ10 from various dermal standard and nano-formulations.