These different types of marine macroalgae are illustrated in Figure 1. There is an increasing demand for bioactive constituents in cosmetic and cosmeceutical applications from macroalgae. The applications of macroalgae-derived compounds to the cosmetic industry are based on their potential biological activities [26; 27; 28]. These are lipids, fatty acids, polysaccharides, vitamins, minerals, amino acids, phenolic compounds, proteins, pigments, etc., which have attracted attention for their skin cosmeceutical benefits [29; 30; 31]. Marine algae are one of the natural resources of phytochemical compounds, which confer potential biological activities [32; 33]. Phenolic compounds are one of the bioactive compounds produced in seaweeds, are made of an aromatic ring with one or more hydroxyl groups, and their structures diversify from simple to complex, higher molecular weight compounds [34; 35]. Many previous studies have been carried out in which phenolic compounds were isolated from marine algae and they include simple phenolic compounds or polyphenols such as flavonoids, phlorotannins, mycosporine-like amino acids (MAAs), bromophenols, and terpenoids [36]. The biological action of phenolic compounds is determined by the position of the hydroxyl groups, and the number of phenyl rings in the structure [37]. Brown algal species contain a high amount of phlorotannins whereas green and red algae mainly produce flavonoids, bromophenols, terpenoids, and mycosporine amino acids in response to environmental conditions [36; 37; 38; 39; 40]. Marine algae-derived phenolic compounds have a wide variety of applications such as enzyme inhibitory effects (for example, tyrosinase inhibition, elastase inhibition, collagenase inhibition, matrix metalloproteinase inhibition in photoproduction, inhibition of angiotensin-converting enzyme-1 (ACE-1), pro-inflammatory cyclooxygenase and lipoxygenase (COX-1, 2 and 5-LOX) as well as dipeptidyl peptidase-4 (DPP-4) inhibition, and hydroxymethyl glutaryl coenzyme A reductase (hMGCR) inhibition) antibacterial, antifungal, antioxidant, and anti-inflammatory properties, which can be very attractive when utilized in cosmetics and cosmeceutical product preparations [41; 42; 43; 44; 45; 46; 47]. In cosmetics, phlorotannin provides hyaluron activation, antiallergic, anti-wrinkle, anti-aging, skin whitening, photoprotection, and skin health improvement benefits [48; 49]. This review represents marine algae-derived phenolic compounds, their chemical structures, together with their skin benefits and their potential in the skin cosmetics industries. Figure 1: _Cont._  
Phenolic compounds are one of the most researched marine macroalgae-derived biologically active compounds and are already utilized in various cosmeceutical preparations [50]. Normally, these phenolic compounds are not extracted because seaweed extracts contain a good number of phenolic compounds. According to [PERSON] and [PERSON] [51], [PERSON] et al. [52], and [PERSON] [53], phlorotannin is one of the marine algae-derived phenolic compounds with less toxicity than other natural antioxidant molecules and its anti-aging benefit is attracting the attention of researchers looking to use it as an ingredient in cosmetic formulations. Some marine algae extracts are rich in different phenolic compounds such as phlorotannin, phloroglucinol, eckol, dieckol, fucol, phlorothol, fuhalols, lignans, bromophenol, flavonoid, phenolic terpenoids, and mycosporine amino acids (MAAs). These phenolic compounds contribute to skin benefits, with antiaging, photoprotection, antiwrinkle, antiallergic, anti-inflammation, antioxidant, antimicrobial, antifungal, tyrosinase inhibition, anti-melanogenic, skin whitening, UVB protector, and antiacene properties, etc. [54; 55; 56]. [PERSON] et al. [57], and [PERSON] et al. [58] reported not only cytotoxicity but also the antibacterial effect of a phenolic fraction from the _Ulva calthrata_ and _Ulva flexuosa_ species that can be utilized for skin benefits. In addition, [PERSON] et al.