66 JOURNAL OF COSMETIC SCIENCE MATERIALS AND METHODS SEARCH STRATEGY For this review, the published articles and reviews on the use of natural active ingredients in cosmetic formulations were retrieved from electronic databases including ScienceDirect, PubMed, National Center for Biotechnology Information databases, and ResearchGate. Some of the keywords included “natural cosmetics,” “active ingredients,” “skin hydration,” “moisturizing effect,” and “formulations.” DATA EXTRACTION From articles searched, the inclusion and exclusion criteria were used in the extraction of data. The included criteria consisted of publications from various database sites, such as English language articles, abstract articles, review articles, full text articles, and experimental studies. These were about natural active ingredients used in cosmetic formulations for skin hydration, and articles published in languages other than English were excluded from the search. Data extracted included information on basic details and functions of the natural active ingredients used in cosmetic formulations on therapeutic values, such as hydrating and moisturizing effects on the skin. This review collected all of the data related to the efficiency of the natural sources on skin hydrating levels and compiled them into one review article. Some of the studies also analyzed the biological and pharmacological activities of the natural resources that have good hydrating effects those data were also included in this review. RESULTS A total of 75 studies from ScienceDirect, 35 studies from PubMed, 45 studies from the National Center for Biotechnology Information, and 20 studies from ResearchGate were selected. After removing duplicates, 115 studies remained. After reviewing their titles and abstracts, 20 studies were excluded. The remaining 105 articles were assessed in more detail for eligibility by examining the full texts. Among them, 9 were excluded due to lack of relevant outcome measurements, and 11 were excluded due to lack of detailed information. Finally, 75 studies were used for the data extraction. The flowchart of the literature search is presented in Figure 3. Data extracted from the final studied articles are presented in table format to understand and identify different types of active ingredients commonly found and used in cosmetic formulations to date. Table I displays different plant-based sources used in cosmetic formulations. Meanwhile, Table II shows several animal and marine sources used as the active ingredients in cosmetic formulations. DISCUSSION It is widely known that moisturization is the first step toward skin health. It helps to maintain the skin’s appearance, strengthen skin elasticity, and play a role as a barrier against harmful environmental factors (12,13). Moisturization also helps to prevent skin aging. To

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.