1. Introduction
Cosmetics are the materials used to enhance or alter the function and appearance of the skin and hair [
1]. Kligman created the term “cosmeceutical” to hightlight cosmetic products that can combine the use of both cosmetic and pharmaceutical uses [
2]. Cosmeceuticals are often used in dermatology to enhance the skin tone, skin glow, and provide anti-aging benefits [
3]. The cosmeceutical industries are most fascinating, profitable, and constantly growing in the world economy. According to reports, an average woman spends
$15,000 on beauty products in her lifetime [
4]. The cosmetics industry has predicted an annual gross revenue of US
$170 billion according to the financial exploration stated by a French-based company, Eurostaf [
5]. In 2016, the European cosmetics market was top in the world, esteemed at €77 billion in a wholesale rate, trailed by the US and Brazil [
4]. The global beauty market stated that the cosmetic industry will continue to develop due to the growth of the middle class in many developing countries [
6]. Based on this encouraging future of the cosmetics industry, many cosmetic products without any side effects have been developed to satisfy the customers’ needs. Currently, many synthetic chemicals have been used in cosmetic products, many of them did not get synthetic customer satisfaction due to high cost and unsafe nature in terms of side effects. For example, chemicals like hydroquinone, arbutin, and kojic acid are being used as a skin whitening agent, but they are reported to be unstable and they also cause dermatitis and induce cancer [
7,
8,
9]. Thus, in recent years, the demand for cosmetic products that containing natural ingredients is rapidly expanding. The advantages of natural ingredients are environmentally friendliness, fewer side effects, and safe use [
1,
10]. Hence, Cosmeceutical industries are persistently seeking active compounds from natural sources. From this perspective, the marine environment provides numerous marine organisms, including seaweeds with potential bioactive compounds. Seaweeds are rich in bioactive compounds that could be exploited as functional ingredients for cosmetic applications [
11]. This review focusses on the cosmetic properties of seaweed bioactive compounds and provides an overview of skin problems and the potential of seaweed bioactive compounds against skin problems.
5. Seaweeds a Potential Source in the Cosmetic Industry
Nowadays People prefer cosmetic products that have natural ingredients than chemical ones. As the products with natural ingredients are safe to use without any side effects, many consumers go in search of natural products to keep themselves look young with healthy skin. Due to this, the cosmetic industry has also focussed on the ingredients that are derived from natural resources like plant, algae, microbes, and their metabolites. The marine world is extremely demanding for a wide variety of species with multiple bioactive compounds. Macroalgae are major resources for the active compound with a wide variety of applications in many fields (
Figure 3) [
16].
Macroalgae or seaweeds are the aquatic, photosynthetic organisms taxonomically categorized as algae, and they divided into three groups based on their pigment, the Rhodophyceae (red algae), Phaeophyceae (brown algae), and Chlorophyceae (green algae). Marine algae are considered as sea vegetables which are also used for consumption. Since ancient times seaweeds are also used as an alternative medicine for skin-related diseases. Many studies revealed the potentiality of seaweeds and their major role in antioxidant, antitumor, anti-inflammatory, anti-lipedemic, anti-microbial, and also their anti-allergic properties. Wide applications of seaweeds are based on the valuable bioactive compounds and potent bioactivity. In addition, the compounds derived from marine algae have been given considerable importance in developing a cosmeceutical product [
41]. Seaweed compounds—including phenolic compounds, polysaccharides, pigments, PUFA, sterols, proteins, peptides, and mycosporine-like amino acid (MAA)—exhibited a wide range of bioactivity that can be used as active ingredients in cosmetic products (
Figure 3) [
7,
42]. Phenolic compounds are the water-soluble secondary metabolites that have numerous biological activities [
43]. It is a diverse group of compounds and the common structural features shared by all the phenol groups. Based on the number of substituents, phenolic compounds can be divided into simple phenols or polyphenols. Flavonoids and gallic acid are the building blocks of polyphenols. Phenolic compounds from seaweeds, like
Ecklonia cava Kjellman and
Ishige okamurae Yendo, are proven to have many bioactivities—including anti-oxidant, anti-microbial, anti-inflammatory, anti-cancer, etc. Antioxidant activity of seaweeds is mainly due to the presence of phenolic compounds [
43,
44]. Among the many phenolic compounds extracted from seaweeds, phlorotannins from brown seaweed are the most important secondary metabolites, with a wide range of functional bioactivity [
45]. Phlorotannins are phloroglucinol-based polyphenols found in Marine brown algae. Phloroglucinol units linked to each other in various ways to form phlorotannins [
46]. Marine brown algae such as
Ecklonia cava Kjellman,
E. stolonifera Okamura,
E. kurome Okamura,
Ishige okamurae Yendo,
Hizikia fusiformis (Harvey) Okamura,
Eisenia bicyclis (Kjellman) Setchell Undaria pinnatifida (Harvey) Suringar,
Sargassum thunbergii (Mertens ex Roth) Kuntze, and
Laminaria japonica. Areschoug have been studied the biological activity of phlorotannins [
47,
48]. Phlorotannins are well known for their wide-ranging applications which include anti-melanogenesis, anti-aging, and antioxidant [
49,
50,
51,
52]. As a result of the bioactivities, the application of phlorotannins on pharmaceutical, nutraceutical, and cosmeceutical advances [
43,
53,
54].
Polysaccharides are the most important compounds present in seaweeds and are well documented for its biological activity. The green seaweed-like Ulva has the high content of polysaccharide comprises of 65% of dry weight. The other seaweeds that have a large amount of polysaccharide are Ascophyllum, Porphyra, and Palmaria species. The important polysaccharides are ulvan from green seaweeds, fucoidan, alginate, and laminarin from brown seaweeds, agar, and carrageenan from red seaweeds. In this, agar and alginate are used widely in the food industry as thickening and gelling agents. Fucoidan, ulvan, and carrageenan are sulfated polysaccharides that have wide application in many fields. Among these polysaccharides, the fucoidan from brown seaweed has been studied enormously for their bioactivity including antioxidant, anticancer, antimicrobial, hyperlipedemic, anti-inflammatory, etc. [
4]. In recent days, many studies recommend the use of polysaccharide as an active ingredient in cosmetic formulations. Polysaccharides have a huge number of cosmetic roles such as hair conditioners, moisturizers, emulsifiers, wound-healing agents, and as a thickening agent [
55,
56].
Proteins are macromolecules made up of one or more amino acids. Seaweeds are a good source of amino acid. Amino acids are one of the important constitutes of natural moisturizing factor which prevents the water loss in the skin [
57]. Seaweeds have amino acids, such as alanine, proline, arginine, serine, histidine, and tyrosine. Palmaria and Porphyra have the maximum amount of arginine, which is considered a natural moisturizing factor that can be used in cosmetic products. Mycosporine-like amino acids are water-soluble low molecular weight molecules. They are categorized by cyclohexane joined with nitrogen as a substitute for amino acid, amino alcohol, or amino group [
57]. For seaweeds exposed to extreme stress including UV radiation, Mycosporine-like amino acids defend seaweed from UV radiation and act as a potent photo protector candidate. It also involved in radical scavenging and DNA repair systems. Hence, they have received more attention as UV protection and antioxidant agents in the cosmetic industry [
3,
16,
58]. Furthermore, in recent years, peptides have drawn attention in the field of skincare due to their binding specificity to the target cells and their ability to change the physiological functions in the skin. Bioactivity depends on the composition of amino acids.
Macroalgae contain a large variety of pigments which absorb the light for photosynthesis. The green algae contain the pigment similar to the plants namely chlorophylls a, b, and carotenoids. The red algae have photosynthetic pigments such as chlorophyll a and the phycobilins such as R-phycocyanin and R-phycoerythrin and carotenoids, mostly β-carotene, lutein, and zeaxanthin. The brown algae pigments include the chlorophylls a and c, fucoxanthin, and carotenoids. The pigment act as a shield to the cells from UV irradiation [
59]. Seaweeds are an important source of vitamin A, vitamin B, vitamin C, vitamin D, and vitamin E which are widely used in skincare.
The lipid content of seaweeds is generally low and less than 4% of the dried mass, whereas
Sargassum kjellmaniamum Yendo contains more than 6% [
60]. Lipids such as essential fatty acid, glycolipids, sterols, triglycerides, and phospholipids are found in seaweeds. Polyunsaturated fatty acid (PUFA) present in seaweeds is higher than in terrestrial plants. Seaweed fatty acids have anti-allergic and anti-inflammatory activities and also act as an emollient that protects the skin from water loss [
61].