###### Abstract  
Due to the rapid increase in the use of anti-aging cosmetic products, there is a need to develop valid analytical methods to control their quality. The present work deals with the development and validation of a new chromatographic method for the quantitative determination of five lipophilic components (resveratrol, ferulic acid, quercetin, retinol, and \(\alpha\)-tocopherol), with anti-aging properties, in a cold cream (\(w/o\)). For the HPLC-UV separation of the active ingredients, an HS, Discovery(r) Supelco (Supelco Inc., Bellefonte, PA, USA), C\({}_{18}\) column (25 cm \(\times\) 4.6 mm), 5 \(\upmu\)m (at 40 \(\lx@math@degree\)C) was used as a stationary phase while a binary system of A: Acetonitrile with formic acid 0.2% and B: H\({}_{2}\)O with formic acid 0.2%, in gradient elution (flow 1.5 mL-min\({}^{-1}\)), was used as mobile. The analytical method was validated according to ICH guidelines Q2(R2), where linearity (r\({}^{2}\geq\) 0.998), selectivity, precision (% recovery 97.1-101.9), and accuracy (%RSD \(<\) 2) were evaluated. The processing of the samples for the recovery of the five analytes from the cream was investigated by experimental design methodology and the cross D-optimal technique (% recovery 98.5-102.9, %RSD \(<\) 2%, n = 5). Finally, the same analysis was applied to study the transdermal penetration of the active ingredients incorporated in cold cream (over a period of 8 h). Their behavior was compared with the corresponding one in suspension using Franz cells in a vertical arrangement. The new method is considered reliable for the analysis of the anti-aging product. HPLC-DAD; anti-aging cold cream; experimental design methodology; permeability study 2  
promote both regeneration and restoration of their normal integrity [7]. Aged skin is biologically characterized by the decomposition of the dermal extracellular matrix, where collagen, elastin fibers [2], glycosaminoglycans, and hyaluronic acid decrease. Nowadays, many people, especially women, spend a lot of money on cosmetics and drugs for the treatment and prevention of aging. Thus, in recent decades, this problem has been a field of interest for scientific groups for the development of new cosmetic products. Creams have a wide application in cosmetology and are the most frequent forms of cosmetics for daily use. By the term \"cream\", we mean a solid or semi-solid emulsion (\(o/w\) or \(w/o\)), which is intended for application to the skin or mucosa [8]. Resveratrol (RSV), ferulic acid (FERA), quercetin (QR), retinol, RTN (vitamin A), and \(\alpha\)-tocopherol, \(\alpha\)-TOC (vitamin E) are five active pharmaceutical ingredients (APIs) that, according to the existing literature, contribute to the reduction in facial aging. Their use in cosmetic products is mainly due to their antioxidant and anti-inflammatory effects. The substances are presented as regulators in cellular functions, in the expression of genes that reduce oxidative stress, and in the control of free radical formation [9]. Therefore, their use contributes to the hydration and vascularization of the skin, with the result that wrinkles are removed, and the skin, due to an increase in collagen, acquires elasticity and hardness [10; 11; 12; 13]. Sunlight is another reason that leads to premature aging. [PERSON] and [PERSON] utilized resveratrol (5-100 uM) in UV/B-irradiated HaCaT keratinocytes and observed that it increased keratinocyte survival [14; 15]. Accordingly, vitamin E can reduce hyperpigmentation caused by UV radiation because it exhibits photoprotection [16]. Resveratrol may also slow down the skin aging process due to its role as a surtuin activator (regeneration and cellular enzyme) [17] while exhibiting antibacterial, antiviral, antifungal, and anti-inflammatory properties [18]. Likewise, retinol is essential for the growth, reproduction, and maintenance of epithelial tissues as well as for wound healing [19].