Human hair, a significant skin appendage, plays a crucial role in appearance, thermoregulation, sensory input, and barrier protection [1]. Hair follicles continually regenerate throughout life, producing hair shafts primarily composed of keratins—proteins with a relatively high cysteine content. These cysteine residues form disulfide and polysulfide bonds, contributing to the hair fibre's mechanical strength and antioxidant capacity [2,3]. There are seventeen keratin subtypes varying by molecular weight, isoelectric point, and their location within the hair shaft. The shape of hair—whether straight or curly—is influenced by the geometric and molecular effects of keratins. Straight hair exhibits an even distribution, while curly hair shows asymmetric differentiation of the precortex [4]. The elasticity and strength of textured hair are closely associated with disulfide bonds, which serve as cross-linking structures that support fibre shape and are essential for hair treatments involving the transient breaking and reformation of these bonds. The structure of textured hair is further defined by the formation and arrangement of keratins and water-soluble keratin-associated proteins (KAPs) that contribute to the hair's main compartments: the cuticle, cortex, and medulla. Additionally, lipids such as 18-methyl eicosanoid acid (18-MEA) protect against mechanical and chemical stress and vary among different ethnic hair types [5].
There is a growing need for specialised hair care products designed specifically for textured hair, particularly those that offer protection against ultraviolet radiation (UVR). Textured hair accounts for 70% of the world’s population, with prevalence varying by skin ethnicity—ranging from 40% for wavy hair to 12% for curly types in European and Asian populations and up to 95% for curly types in African populations [5]. This hair type has distinct structural characteristics that make it more vulnerable to environmental stressors like UVR, which primarily impacts the cuticle and hair surfaces by reducing lipid content and tensile strength [6]. Curly hair is especially prone to frizz and dryness, while coily or kinky hair types, particularly of African origin, are more susceptible to brittleness and breakage due to lower tensile strength [7,8]. For instance, the relatively low fibrous protein content in African hair may contribute to its increased susceptibility to breakage [9]. Moreover, UV exposure can intensify hair bleaching through oxidation and loss of melanin’s protective function in the cortex, while common hair styling practices like chemical relaxation and the use of mechanical or thermal tools can further exacerbate these issues [10]. This vulnerability is compounded by the fact that a significant portion of the global population with textured hair resides in regions with high UV indices, reaching values of ~10 in West Africa, ~9 in South Asia, and up to 15 in South Africa [11–12]. These conditions increase the risk of hair fibre damage, including thinning, breakage, and colour degradation, underscoring the importance of targeted solutions for textured hair.
As a result, there is a growing trend in global research and the industry market towards developing personalised, hair-protective products with a stronger focus on the unique needs of textured hair [13,14]. Conditioning products are designed with various ingredients, such as natural or synthetic polymers, oils, and proteins, to meet the needs of different hair types by restoring moisture, strengthening the cuticle, and improving overall hair structure. There is also high demand for next-generation hair care products that use bioactive compounds with predicted or proven activity towards the specific requirements of different hair types [9,14]. Creating these products involves advanced technologies to identify and test active ingredients, ensuring they effectively address the unique physical and biochemical properties of hair.
This present study investigated the protective effect of a novel conditioner against the hair damage caused by UVR. The conditioner has been formulated with natural active ingredients—mangiferin, ferulic acid, and naringin—selected for their UV-absorbing and antioxidative properties. The study provides fascinating insight and consistent evidence that curly hair shafts are more sensitive to UVR damage than straight hair shafts. In particular, the alterations to textured hair by UVR appeared to be associated chiefly with changes to the hair surface, permeability and keratin organisation. Moreover, pre-treatment of the hair with conditioner significantly reduced these damaging effects. These results show that these ingredients protect textured hair from damage. Furthermore, consumers, particularly those with textured hair, should be aware of and select ingredients compatible with their specific hair type.
The study investigated the effects of UV radiation on hair and the protective properties of the conditioner at structural and molecular levels. UV absorption and Antioxidant capacity was evaluated for the bioactive compounds (Mangiferin, ferulic acid, and naringin) and conditioner. Hair samples of South American origin were treated with the conditioner and exposed to UV radiation. and analyzed for damage using Rhodamine B dye. Various techniques such as light and fluorescence microscopy, ATR-FTIR, and Scanning Electron Microscopy were used to assess molecular changes in hair thickness, darkness, and keratin structure.
Results showed that mangiferin had the most potent UV-absorbing properties covering UVC, UVB and UVA. While ferulic acid and naringin covered the UVC-UVB ranges (Figure 1a). All three demonstrated strong antioxidant potential, with mangiferin having the highest total antioxidant capacity (TAC), followed by ferulic acid and naringin (Figure 1b). When blended in a conditioner, the formulation's absorbance profile covered UVC, UVB, and UVA (Figure 2a). This suggests that the bioactive compounds individually and, in the conditioner, effectively protected hair from oxidative damage caused by UVR. After UV exposure, the antioxidant capacity of both straight and curly hair remained unchanged. However, pre-treatment with the conditioner increased the antioxidant capacity in both hair types, and this effect was more pronounced after exposure of curly hair to UVR (Figure 2b).
Hair fibre thickness was significantly reduced by UV exposure, with curly hair being more affected than straight hair, indicating its greater sensitivity to UV damage. Pre-treatment with the conditioner slightly increased hair thickness and provided partial protection against UV-induced thinning for both hair types (Figure 3a). UVR also caused noticeable hair bleaching, particularly in curly hair. Pre-treatment with conditioner preserved hair darkness in both hair types (Figure 3b). Penetration of the Rhodamine B dye was used to assess the degree of damage. Curly hair showed an increased permeability to the dye after UV exposure, indicating higher damage than straight hair. The conditioner effectively reduced dye uptake, demonstrating its protective effect on the structural integrity of hair fibres (Figure 4 a,b).
To understand molecular changes, the spectral absorbance of keratin extracts from control and UVR-treated straight and curly hair —with and without conditioner pre-treatment—- was analysed. In the control condition, both hair types showed similar absorbance peaks, indicating intact keratin structures. UV exposure significantly reduced keratin absorbance, especially in curly hair, reflecting greater structural damage. Pre-treatment with the conditioner before UVR protected keratin structure, particularly for textured hair. ATR-FTIR spectroscopy confirmed this, showing that UV exposure disrupted key keratin bonds, particularly in curly hair, while the conditioner restored the absorbance patterns. This suggests that the protective effects occurred on a molecular level. SEM images further demonstrated significant surface damage and thinning in UV-exposed curly hair, while the conditioner protected hair structure and fibre volume.
This report highlights a novel hair conditioner formulated with a trio of natural compounds: mangiferin, ferulic acid, and naringin. What distinguishes this formulation from others is its exceptional ability to protect hair from UV damage on a structural and molecular level. The conditioner's natural compounds deliver broad-spectrum UV defence and high antioxidant capacity, shielding hair from oxidative stress. This prevents thinning and bleaching while preserving hair's natural strength and colour. Importantly, it protects the keratin structure at a molecular level. This feature is particularly beneficial for curly hair, which is inherently more susceptible to UV damage. This conditioner delivers targeted and effective care, making it an ideal solution for those seeking to safeguard and enhance their hair's health against environmental stressors.
Contact: Sola@LaylaKays.com
