The industrial processing of widely consumed Cucurbitaceae fruits, such as watermelon (Citrullus lanatus), melon (Cucumis melo), and pumpkin (Cucurbita pepo), generates substantial quantities of seed by-products. These residues, often discarded or relegated to low-value uses like animal feed or biofuel, pose a significant global environmental burden due to their high moisture and microbial loads. In light of escalating climate change and the depletion of non-renewable resources, there is an urgent and growing emphasis on waste prevention and the valorization of agro-industrial food waste, aligning with waste hierarchy and circular economy directives.
Within this context, Cucurbitaceae seeds have gained recognition as promising, yet underexplored, renewable sources of bioactive compounds. Their potential extends beyond nutrition to high-value applications, particularly in the cosmetics industry. This aligns with increasing consumer demand for natural, plant-based ingredients in skincare formulations, driven by the “green beauty” movement and ecological concerns. By transforming these underutilized by-products into functional cosmetic resources, the approach not only adds value to agricultural waste but also significantly reduces environmental impact and supports sustainability goals.
Key Findings
The seeds of the Cucurbitaceae family are rich in a diverse array of bioactive compounds, making them highly valuable for dermocosmetic applications:
• Rich Biochemical Composition: These seeds are packed with polyunsaturated fatty acids, proteins, carbohydrates, and phytochemicals, including vitamins, minerals, dietary fiber, carotenoids, and polyphenols (alkaloids, saponins, flavonoids, and phenolic acids).
• Multifaceted Skin and Hair Benefits: Incorporating extracts from these seeds into cosmetic formulations offers extensive benefits for both skin and hair. This includes antioxidant activity, deep hydration, and support in managing conditions such as hyperpigmentation, acne, and psoriasis. For hair, they contribute to improving oil balance, reducing frizz, and enhancing strand nourishment.
• Superior Moisturizing and Emollient Properties: High levels of essential fatty acids, primarily linoleic and oleic acids, provide significant moisturizing and emollient effects. These oils are lightweight, quickly absorbed, and form a protective barrier that reduces transepidermal water loss, crucial for maintaining healthy, supple skin.
• Potent Antioxidant and Anti-aging Effects: Due to their content of phenolic compounds, vitamins C and E, and specific amino acids, these seeds effectively neutralize free radicals, preventing oxidative damage and premature skin aging. Phenolic acids promote collagen synthesis, enhancing skin resilience. Tocopherols offer anti-aging benefits, and phytosterols, especially β-sitosterol, stimulate collagen and hyaluronic acid production, improving moisture retention.
• Targeted Treatment for Skin Conditions:
◦ Hyperpigmentation: Phenolic acids like gallic and caffeic acid exhibit depigmenting effects by inhibiting tyrosinase, which reduces melanin synthesis, making them promising for skin-lightening products. Ellagic acid also acts as a skin whitening agent.
◦ Acne, Psoriasis, and Dermatitis: Their anti-inflammatory and antimicrobial properties (from phenolic compounds and zinc) are beneficial for treating inflammatory conditions such as acne, seborrheic dermatitis, and atopic skin. Flavonoids are specifically cited for managing psoriasis and dermatitis.
◦ Wound Healing: Arginine enhances collagen deposition and promotes type I collagen secretion, supporting wound healing and tissue regeneration. Glutamate, especially as an arginine-glutamate ion pair, significantly enhances skin elasticity and reduces damage by stimulating collagen synthesis. Syringic acid, gallic acid, and vitamin K also show promise in wound healing.
• Hair Health Promotion: Amino acids strengthen hair strands, improve their condition, and help prevent split ends. Linoleic acid stimulates hair growth. Specific amino acids like arginine, glutamate, leucine, and valine are important for hair follicle maintenance, while histidine and phenylalanine improve hair tensile strength.
• Species-Specific Dermocosmetic Contributions:
◦ Citrullus lanatus (Watermelon): Its seed oil is a lightweight emollient, rich in essential fatty acids, and has been traditionally used for dermatological conditions and soap-making. It boasts high concentrations of vitamins A and C, crucial for skin health.
◦ Cucumis melo (Melon): Notably rich in flavonoids such as catechin and naringenin-7-O-glycoside, and contains the highest overall phenolic acid content. It is particularly high in linoleic acid (up to 69%), vital for skin barrier repair and photoprotection. Melon seed oil is also an exceptional source of vitamin E.
◦ Cucurbita pepo (Pumpkin): Stands out with high levels of oleic acid, which acts as a skin penetration enhancer, making it ideal for targeted delivery systems. It is also highly concentrated in stigmasterol and β-sitosterol, indicating strong anti-aging potential, and consistently provides high levels of γ- and δ-tocopherol.
• Enhanced Efficacy through Nanoencapsulation: Nanoencapsulation techniques (e.g., nanoemulsions, liposomes, nanostructured lipid carriers) significantly improve the physicochemical stability, dermal absorption, and bioavailability of these seed oils. This strategy allows for controlled and sustained release, extended bioactive effects, and improved sensory attributes like reduced greasiness, thereby maximizing their efficacy in anti-aging, skin regeneration, and photoprotective products.
From a dermocosmetic perspective, the demonstrated compatibility of these seed oils, especially Cucurbita pepo, with nanoencapsulation techniques represents a significant advancement. This approach not only addresses their inherent instability and limited dermal permeability but also enhances their bioavailability, stability, and absorption, thereby expanding their application potential in high-performance formulations.
The future implications of this research are substantial. The valorization of Cucurbitaceae seeds for cosmetics not only drives the development of innovative, high-performance, and eco-conscious products but also critically aligns with circular bioeconomy principles and global sustainability goals by repurposing agricultural by-products and adding economic value to agro-industrial chains. Future research should prioritize comprehensive clinical trials to rigorously validate their efficacy and safety in human skin applications. Advancing multifunctional nanoencapsulation systems and integrating these oils into synergistic formulations with other botanicals could further unlock their potential. Ultimately, by focusing on innovation, standardization, and sustainable sourcing, Cucurbitaceae seed oils are poised to become highly valued, eco-conscious ingredients for the next generation of cosmetic formulations.
Link to the study: https://www.mdpi.com/2674-1024/4/3/36
