67 NATURAL ACTIVE INGREDIENTS AND SKIN HYDRATION achieved maximum effects of skin hydration and consumer acceptability, a moisturizer should be able to reduce and prevent water loss in the skin help restore the lipid barrier properties of the skin by enhancing its moisture retention mechanisms provide immediate hydration be immediately absorbed into the skin be nonsensitizing and be cosmetically acceptable and affordable for a consumer to purchase (4). Studies on the influence of moisturizers on the skin’s barrier properties have shown that they are able to enhance skin hydration, reduce skin roughness and scaling of the skin, and help improve dry skin conditions (10). The functions and uses of natural sources and the properties of their active ingredients are further discussed in this review. Figure 3. Flow diagram of the study selection process.

68 JOURNAL OF COSMETIC SCIENCE Table I Plant-Based Sources Used in Cosmetics Sources Bioactive ingredients Therapeutic value/s Reference Turmeric Curcuminoids Moisturizing Antioxidant (83) Aloe vera Phenolic Vitamins Sugars Anthraquinones Moisturizing Anti-inflammatory (88) (87) Papaya peel Vitamin A Moisturizing Smoothness Lightening, restore, rebuild damage skin (105) Palm oil Tocopherol Tocotrienol Vitamin E Antioxidant Emollient Moisturizing (32) (31) (86) Shea butter Vitamin A Vitamin E Vitamin F Moisturizing Emollient Anti-inflammatory Restore skin (24) (11). Mango butter Tocopherol Triterpenes Phytosterol Vitamin E Moisturizing Anti-inflammatory Skin rejuvenating (85) Cocoa butter Vitamin E Vitamin F Palmitic acid Linoleic acid Antioxidant Anti-inflammatory moisturizing Smoothness (32,66) (89,109) (108) Avocado oil Pumpkin seeds Phytosterols Fatty acids Moisturizing Antioxidant Anti-inflammatory (90) (66) (89) Comfrey root Allantoin Moisturizing Keratolytic (91) Sweet potato Hyaluronic acid Moisturizing Skin rejuvenating (17) (16) Cucumber Vitamin C Cucurbitacin Moisturizing Skin rejuvenating (92) (93) (94) (95) Sweet almond oil α-tocopherol Vitamin A Vitamin E Unsaturated fatty acids Moisturizing Smoothness (38) (39) (37) (97) (96) C asiatica Centelloid Flavonoid Phytosterols Moisturizing Anti-inflammatory Skin regeneration (98) Calendula flowers Essential oil Fatty acids Tocopherol Moisturizing Skin regeneration (99) (100) Jojoba oil Sunflower seed oil Argan oil Fatty acids Linoleic acid Moisturizing Antioxidant (101) (90)