Content and stability of B complex vitamins in commercial cosmetic products

Abstract

Background: Individual B vitamins have many favorable effects on the skin and are common cosmetic ingredients. However, their formulation is demanding due to stability issues, which consequently affect the products' quality.

Aims: We aimed to determine the quality (labeling accuracy, content determination, and content-related quality control) and stability under long-term and accelerated storage conditions of a representative sample of commercial cosmetics containing the most common B vitamins - nicotinamide, dexpanthenol, pyridoxine, and cyanocobalamin.

Methods: Cyanocobalamin was determined by a previously published stability-indicating HPLC- diode array detector (DAD) method for the simultaneous determination of all hydrophilic vitamins. This method was additionally simplified and adjusted for the time-effective analysis of nicotinamide, dexpanthenol, and pyridoxine. Both methods were properly validated.

Results: All labeled B vitamins were present in the 36 tested products, mostly in contents, reported effective on the skin. Thus, a straightforward correlation between vitamin contents and product prices were not observed. The content-related quality control of eight products, which quantitively specify their content, revealed significantly lower nicotinamide contents (47% and 57%) in two products and appropriate or higher nicotinamide (102%-112%) and dexpanthenol (100%-104%) contents than declared in the remaining products. The 6-month long-term and accelerated stability studies demonstrated the products' physical stability, but also revealed dexpanthenol, pyridoxine, and cyanocobalamin degradation, while nicotinamide was mostly stable in the tested products.

Conclusions: The obtained results provide an inside into the quality of commercial vitamin B cosmetics and highlight the importance of stability testing in the formulation of quality, efficient, and safe cosmetics.

Keywords: D-panthenol; cosmeceuticals; cosmetic formulation; niacinamide (nicotinamide); stability; vitamin B3.

FIGURE 1

Determined contents of nicotinamide (B3), dexpanthenol (B5), pyridoxine (B6), and cyanocobalamin (B12) in the tested cosmetic products (C), medical devices (MD), and medicinal product (MP), expressed as a mass percentage (%) (average ± SD, [n = 3]) in relation to the price of the products (per 50 ml). *the labels of individual products are retained throughout the manuscript.

FIGURE 2

Determined contents of nicotinamide (B3) and dexpanthenol (B5) in the tested medicinal (MP) and cosmetic products (C) with their declared contents, expressed as an average % of the declared content (average ± SD, [n = 3]).

FIGURE 3

The remaining content of nicotinamide (B3), dexpanthenol (B5), pyridoxine (B6), and cyanocobalamin (B12) in the tested cosmetic products (C), medical devices (MD), and medicinal product (MP) after 6 months of storage at 25°C and 40°C, expressed as a % of the initial content (average ± SD, [n = 3]).