Photoaging is a progressive and multifactorial skin aging process primarily triggered by prolonged exposure to ultraviolet (UV) radiation. This condition results in significant structural and functional impairments in the skin, including the formation of wrinkles, loss of elasticity, pigmentation irregularities, and an elevated risk of skin malignancies. At its core, photoaging involves the accumulation of reactive oxygen species (ROS), which generate oxidative stress, initiate chronic inflammation, cause DNA damage, and accelerate the breakdown of the extracellular matrix (ECM), largely through the activity of matrix metalloproteinases (MMPs).
Given that skin aging impacts not only physiological function and health but also aesthetic appearance and quality of life, there is increasing scientific and commercial interest in effective strategies to protect and rejuvenate skin cells and components. Naturally derived bioactive substances have gained significant attention due to their inherent antioxidant, anti-inflammatory, and photoprotective properties, making them a promising avenue for addressing the effects of photoaging. This review provides a comprehensive analysis of various natural substances, including antioxidants, anti-inflammatory agents, photoprotective compounds, and emerging regenerative treatments, highlighting their potential in preventing and treating photoaging.
Key Findings
The review identified a wide array of natural substances with significant anti-photoaging potential, categorized by their chemical nature and primary mechanisms of action:
• Polyphenols:
◦ Phenolic Acids (e.g., caffeic acid, ferulic acid, sinapic acid) exhibit strong antioxidant and anti-inflammatory properties, preventing photoaging by inhibiting UV-induced MMP-1 expression, reducing ROS production, and enhancing cellular defense mechanisms.
◦ Curcumin (from turmeric) possesses antioxidant, anti-inflammatory, and anti-collagenase properties, inhibiting UVB-induced MMP-1 and MMP-3 expression, reducing ROS, and blocking MAPK/NF-κB/AP-1 pathways.
• Tannins: Proanthocyanidins and tannic acid, found in nuts, seeds, and bark, demonstrate significant antioxidant and anti-inflammatory properties, decreasing ROS, inhibiting MMPs, COX-2, collagenase, and elastase, thus reducing UV damage and improving skin structure.
• Flavonoids: This diverse group of polyphenolic compounds is recognized for its antioxidant, anti-inflammatory, and anti-photoaging effects.
◦ Isoflavones (e.g., genistein, coumestrol) inhibit kinase activation, reduce MMP-1 expression, and enhance collagen synthesis, preserving skin elasticity and preventing UV-induced inflammation.
◦ Flavan-3-ols (e.g., EGCG from green tea) are potent antioxidants that inhibit tyrosinase activity, reduce melanin production, scavenge ROS, prevent elastase activity, and suppress UV-induced MMP production.
◦ Flavonols (e.g., quercetin, myricetin, fisetin) inhibit MMP-1 production and pro-inflammatory cytokines, enhance collagen synthesis, and protect the extracellular matrix from UV degradation.
◦ Flavones (e.g., baicalin) suppress MMP-1, MMP-3, and MMP-9 expression, reduce inflammatory markers, and promote collagen I and III production, leading to significant photoprotective effects.
◦ Flavanones (e.g., hesperitin, hesperidin, naringenin) reduce MMP activity and collagen degradation, exhibit antioxidant and anti-inflammatory effects, and improve skin hydration and reduce wrinkles.
◦ Aloe vera is recognized for its immunomodulatory, anti-inflammatory, and antioxidant activities, mitigating photoaging by activating the Nrf2/ARE pathway, reducing ROS and inflammation, and restoring collagen and elastic fibers.
• Stilbenes (e.g., resveratrol, piceatannol, pterostilbene) show anti-inflammatory, antiviral, anticancer, and antioxidant activities by scavenging ROS, inhibiting MMPs, enhancing collagen synthesis, and modulating immune responses.
• Lignans (e.g., sesamin, silymarin) possess antioxidant, anti-inflammatory, and antitumor properties, protecting against UV-induced oxidative stress and collagen degradation by inhibiting MMPs and enhancing collagen synthesis, with silymarin also absorbing UV light.
• Coumarins (e.g., urolithin A, decursin, umbelliferone, hydrangenol, esculetin, scopoletin) demonstrate anti-UVA-induced photoaging activity, inhibit ECM degradation, suppress senescence-associated enzyme activity, reduce ROS accumulation, and exhibit anti-inflammatory properties.
• Cannabinoids (e.g., Cannabidiol (CBD), Cannabigerol (CBG)) interact with the endocannabinoid system, exhibiting potent anti-inflammatory and antioxidant properties by inhibiting NF-κB activation, TNF-α production, and MMPs, while activating the Nrf2/ARE pathway and preserving collagen and elastin.
• Vitamins:
◦ Vitamin C (L-Ascorbic Acid) is a potent water-soluble antioxidant essential for collagen synthesis, neutralizing free radicals, reducing hyperpigmentation, and stabilizing Vitamin E.
◦ Retinoids (e.g., all-trans-retinoic acid (ATRA), bakuchiol) regulate cell proliferation and differentiation, promote collagen synthesis and epidermal renewal. ATRA is highly effective but can cause irritation, while Bakuchiol is a natural analogue offering similar benefits without photosensitivity or irritation.
◦ Vitamin E is a lipid-soluble antioxidant with anti-inflammatory and anti-glycation effects, significantly inhibiting ROS production, preserving cellular membrane integrity, and reducing wrinkle development.
• Carotenoids (e.g., β-carotene, lycopene, astaxanthin) are lipophilic pigments with potent antioxidant, anti-inflammatory, and photoprotective properties, accumulating in the skin to scavenge ROS, prevent collagen degradation, and maintain skin elasticity. Astaxanthin stands out as one of the most potent and versatile agents, combining antioxidant, anti-inflammatory, and collagen-preserving activities simultaneously, significantly improving skin elasticity and reducing MMP expression.
The future implications of this work are significant. The growing incidence of skin cancer and increasing global awareness of skin health necessitate the development of safe, effective, and scientifically validated anti-photoaging solutions. Continued research, particularly well-designed clinical trials, is essential to confirm the long-term safety, efficacy, and therapeutic relevance of these natural substances and their derivatives. The agents reviewed in this paper represent a hopeful future for integrative, evidence-based skincare and photoprotection strategies, paving the way for innovative and safe approaches to prevent and reverse UV-induced skin damage.
Link to the study: https://www.mdpi.com/1422-0067/26/16/8061
