Seaweed as a Source of Natural Antioxidants: Therapeutic Activity and Food Applications

Department of Food Science and Technology, National Institute of Food Technology Entrepreneurship andManagement, Kundli, Sonipat 131028, Haryana, India Department of Food Engineering, National Institute of Food Technology Entrepreneurship and Management, Kundli, Sonipat 131028, Haryana, India Livestock Production and Management Section, ICAR-Indian Veterinary Research Institute, Izzatnagar, Bareilly 243 122, Uttar Pradesh, India


Introduction
"Good food, good health," this phrase means a lot itself. Nowadays, people bear a lot of stress in their life due to their burdened schedule. e intense stress leads to the generation of free radicals in the body that facilitates rapid ageing. To eliminate stress, one can perform meditation, eat healthy food, do yoga and exercise, etc. Out of these, the most important source to eradicate stress is to eat healthy food, enriched in antioxidants, minerals, vitamins, proteins, fibres, etc. It has been seen that processed food contains synthetic preservatives which oxidize functional component in the food causing oxidative stress, hypertension, and cardiovascular diseases, among others. To replace the synthetic preservatives or additives in processed foods, natural bioactive compounds may be extracted from natural commodities that can be added to processed foods to neutralize oxidation. Macroalga or seaweed is one such natural commodity that is enriched in antioxidants, polyphenols, protein, minerals, and vitamins and possesses various therapeutic activities such as antibacterial, antiviral, anticancer, and antioxidant properties [1]. erefore, seaweed is a more preferable source of bioactive compounds as it has more stable antioxidants as compared to terrestrial plants [2] and helps in preventing oxidative stress and other mammalian diseases.
Seaweeds are primary plants that do not bear flowers, roots, stems, and leaves [3]. ey are found at the bottom of the sea up to 180 m and are mostly found in solid substrates onto a depth of 30-40 m. ey grow in estuaries and are attached to rocks, shells, stones, and other plant materials [3].
seaweeds is due to carotenoids, polysaccharides, vitamins, and its precursor and polyphenols, which contribute to the inhibition of oxidation processes [11]. Seaweeds are also used as a supplement in traditional foods and for the extraction or isolation of bioactive compounds for the development of nutraceutical supplements. Since there is an increasing demand of nutrient-rich food, this review discussed the possible use of seaweeds as a natural source of bioactive compounds and antioxidant. e utilization of seaweeds as a functional ingredient in various food matrix to develop diverse biological activities, such as antimicrobial, anti-inflammatory, anticoagulant, anticancer, and antihypertension activity, has also been discussed.

Classification of Macroalgae
Different species of macroalgae are found in different coastlines of the world which are classified into three taxonomic groups based on pigments as shown in Table 1 [12,13].

Green Seaweed (Chlorophyta).
e color of green seaweeds is yellow to green due to the presence of beta-carotene, chlorophyll a and chlorophyll b, and xanthophylls [14]. ey are small in size similar to red seaweeds [7]. Some Indian green seaweeds are Rhizoclonium riparium, Ulva intestinalis (formerly Enteromorpha intestinalis), Chaetomorpha ligustica (formerly Lola capillaris), and Ulva lactuca [15] while Monostroma sp. is a Japanese green seaweed [17].
tenerrimum, Codium tomentosum, and Hypnea valentiae can be found [18]. In the Tuticorin coast of Southeast India, Turbinaria ornata and Gracilariopsis longissima (formerly Gracilaria verrucosa) can be found [19]. From the coastal regions of Chilika Lake of India is Ulva rigida [20]; from the sea coast of Rameshwaram, Tamil Nadu, India, is Kappaphycus alvarezii [21]; from the east coast of India are Caulerpa racemosa, Ulva lactuca (formerly Ulva fasciata), Chnoospora minima, Padina gymnospora, and Acanthophora spicifera [22]. Even within the same country, the seaweed composition in different coast varies due to different microenvironments. Table 2 shows the basic composition of different seaweed classes.

Protein and Amino
Acids. According to the above species of seaweeds, the protein content ranges from 1.8 to 18.9%. e maximum protein content was recorded in Phaeophyceae members and a minimum in Chlorophyta members [31]. A total of 16 amino acids have been reported in seaweeds (Caulerpa racemosa, Ulva lactuca (formerly Ulva fasciata), Chnoospora minima, Padina gymnospora, and Acanthophora spicifera) collected from the east coast of India. Acanthophora spicifera contain the highest concentration of glutamic acid and aspartic acid of 17.4% and15.7%, respectively [22]. Protein content variation among different species of seaweed is due to the surrounding water quality as reported by Dhargalkar et al. [32].
ere is a need to evaluate the total dietary fibre of different species of seaweed as very less work has been reported for dietary fibre estimation in recent studies.
3.5. Vitamins. Generally, seaweeds are rich in water-soluble vitamins and commonly contain vitamins A, B 12 , C, ßcarotene, pantothenate, folate, riboflavin, and niacin. Seaweeds also contain higher amounts of vitamins than fruits and vegetables. e class Phaeophyceae is rich in watersoluble vitamins such as vitamins B 1 (thiamine), B 2 (riboflavin), B 6 , and nicotinic acid [31]. erefore, seaweeds have the potential to solve the problem of iodine and other mineral and vitamins deficiency [31]. ese biological activities of seaweeds play an important role in the development of functional food which prevents many harmful diseases.

Bioactive Compounds in Seaweeds
4.1. Agar. Agar is a polysaccharide extracted from the red seaweeds (Gracilaria sp. and Gelidium sp.). It is a mixture of agarose and agaropectin where agarose [37] (Figure 1) is a linear chain of polymer consisting of 1,4-linked α-3,6anhydro-L-galactose and 1,3-linked β-D-galactose repeating units and agaropectin is a sulphated polysaccharide composed of agarose and other components such as D-glucuronic acid, ester sulphate, and a small amount of pyruvic acid [38]. Agar-Agar has an important biological activity as it acts as an antitumor agent, reduces oxidative stress, and reduces the level of blood glucose in the human body. Other applications are used as cell culture medium and manufacture of capsules [37]. It has various applications in the food industries including its use as a texture improver in dairy products like cheese, cream, and yogurt and use as a stabilizer in the processing of ices and sherbets. In alcoholic industries, it is used as a clarifying agent for wines, especially plum wines [39].

Carrageenan.
Carrageenan is a linear chain polysaccharide, extracted from red seaweed, Chondrus crispus, and Kappaphycus sp. that contains up to 71% and 88% of carrageenan, respectively. Polysaccharide chains consist of sulphate half-esters that are attached to the sugar unit. Carrageenan has three forms, viz., kappa, lambda, and iota, each with its own gelling property [37] (Figure 2). Kappa carrageenan is 4-sulfated on the 3-linked residue and has a 3,6anhydro bridge on the 4-linked residue while lambda carrageenan has 2,6-disulfated 3-linked residue and 70% sulfation at position 2 of the 4-linked residues. Kappa carrageenan is potassium-sensitive and may be precipitated from dispersions by potassium, while lambda carrageenan is not sensitive to potassium [38]. Carrageenan has many food applications such as in canned food products, dessert mousses, salad dressings, and bakery fillings, as stabilizer in ice cream and instant dessert preparations, in canned pet foods, and in clarifying beer, wines, and honey [37].

Algin.
Stanford discovered the algin in 1881 where it found that sodium carbonate treated with Laminariaceae macroalgae produces the viscous solution known as alginic acid. Alginic acid is a polysaccharide composed of β-Dmannuronic acid and α-L-guluronic acid residues joined by β-1,4-linkage [38]. In pyranose conformation, two uronic acid residues offer three different sequences after partial acid hydrolysis [40]. Algins are also called alginates and can be extracted from brown seaweeds which make up 10% to 30% algin of their dry weight [38]. Alginates are commercially extracted from seaweeds such as Durvillaea antarctica, Ascophyllum nodosum, Macrocystis pyrifera, Lessonia nigrescens, Sargassum turbinaroides, and Ecklonia maxima [40]. Alginates are used in the stabilization of ice-lollies and the manufacture of sausages, thickening agents, and gelforming agents, in the food industry [40,41]. Alginates are polyelectrolytes that selectively bind the alkaline Earth metals such as calcium and sodium ions that help in gel formation [40].

4.4.
Mannitol. D-mannitol is an acyclic hexanol (first sugar alcohol) [42] which was extracted from brown seaweed in 1884 by Stenhouse [38]. Brown seaweed is composed of mannitol up to 20-30% of the dry weight and its level varies in green and red seaweeds [42]. Many functional activities are imparted for mannitol such as carbohydrate storage, translocatable assimilate, source of reducing power, osmoregulation, and scavenging of active oxygen species [43]. Mannitol can be extracted from seaweeds such as Laminaria sp., Sargassum pacificum (formerly Sargassum mangarevense), and Turbinaria ornata [44].

Iodine.
It was reported that many Indian and Japanese seaweeds contain iodine content which is present in low molecular weight iodate form (83%-86%) and easily absorbed in the human alimentary tract.
e Japanese seaweeds like Saccharina japonica (formerly Laminaria japonica), Ecklonia sp., Sargassum fusiforme (formerly Hizikia fusiformis), and Undaria pinnatifida consist of 145, 315, 60, and 5.7 mg/100 g dry matter of iodine content, respectively. It was also reported that green and red seaweeds have more iodine content than brown seaweeds [38]. Iodine is essential for thyroid hormone synthesis and imparts antioxidant and antiproliferative activity in the prevention of cancer and cardiovascular diseases [45].

Laminaran.
Laminaran is a storage polysaccharide (β-glucan) that consists of 20 glucose residues joined by β-1,3-linkage. ere are two types of laminaran, viz., a "soluble laminaran" and an "insoluble laminaran" obtained from Laminaria hyperborea (formerly Laminaria cloustonii) and L. digitata, respectively; the latter is soluble in hot water. Based on the amount of mannitol present in both laminarans, two chains, M-and G-chains, are produced (Figure 4) where mannitol residues occupy the reducing terminal region in M-chains and glucose residues occupy the terminal region in G-chains [38]. e biological activity of laminaran includes antitumor activity, antiapoptosis activity, and immunomodulatory effects [49].

4.9.
Carotenoids. Carotenoids are tetraterpenoids that are used for the classification of seaweeds (red, green, and brown) [55]. Based on metabolism and function, they are divided into two groups, primary and secondary carotenoids. Primary carotenoids are the structural and functional components that help in photosynthesis. Secondary carotenoids are the extraphotosynthetic pigments which are produced through carotenogenesis under specific environmental conditions. Primary carotenoids include α-carotene, β-carotene, violaxanthin, neoxanthin, fucoxanthin, zeaxanthin, and lutein, whereas secondary carotenoids include astaxanthin, canthaxanthin, and echinenone [56]. Carotene is a primary precursor of vitamin A, which prevents night blindness and cataract and helps in the formation of glycoprotein, secretion of mucus from epithelial tissues, cell differentiation, overall development of body and bones, and reproduction. Carotenoids have many functional activities such as antioxidant activity and immune boosting activity and reduce the risk of chronic diseases such as cardiovascular diseases, inflammation, age-related muscular diseases, cancer, obesity, and neurological diseases [56,57]. Seaweeds that contain primary carotenoids include Fucus sp., Undaria pinnatifida, Sargassum sp., Sargassum fusiforme (formerly Hizikia fusiformis), and Saccharina japonica (formerly Laminaria japonica) [56].

Fucoxanthin.
Fucoxanthin is a carotenoid-xanthophyll containing two functional groups, oxygenic and carboxyl groups, linked by allenic bond in the polyene hydrocarbon chain which provides high antioxidant activity [54]. Also, it binds with chlorophyll and proteins to form a stable fucoxanthin-chlorophyll-protein complex that distinguishes it from other plant carotenoids [1]. Fucoxanthin contains more antioxidant activity than other carotenoid pigments due to the presence of conjugated double bonds with epoxide and acetyl substituent groups attached to a polyene [1], whereas carotenoid synthesis in algae may highly depend on the environmental factors, temperature, salinity, irradiance, nutrient concentration, etc. In brown seaweeds, the common species from which fucoxanthin is extracted are Undaria pinnatifida, Sargassum fusiforme, Sargassum fulvellum, Saccharina japonica, Padina tetrastromatica, Sargassum siliquastrum, Turbinaria turbinata, and Sargassum plagiophyllum [58]. e fucoxanthin-chlorophyll-protein complex might be the reason for the therapeutic activity of fucoxanthin such as antioxidant, anti-inflammatory, anticancer, antiobesity, and antidiabetic activity [54]. e major

Antioxidant Activity.
Antioxidants are the substances that scavenge the reactive oxygen species (superoxide anion (O 2-), hydrogen peroxide (H 2 O 2 ), hydroxyl radical (OH))/ reactive nitrogen species (NO), and free radicals which develop oxidative stress in the human body [62]. Due to oxidative stress, biological macromolecules such as DNA, proteins, and nucleic acid are damaged and lead to various harmful diseases such as cancer, diabetes, stroke, Alzheimer's, Parkinson's, and cardiovascular diseases [63]. erefore, antioxidant compounds play an important role to prevent health from harmful factors. It is known that seaweeds contain several bioactive compounds with potential/ higher antioxidant activity as compared to the terrestrial plants due to the presence of up to eight interconnected polyphenols rings [64]. Antioxidant activity of seaweeds is due to the presence of pigments chlorophylls, xanthophylls (fucoxanthin), carotenoids, vitamins (vitamins B1, B3, C, and E) and vitamin precursors such as α-tocopherol, β-carotene, lutein, and zeaxanthin, phenolics such as polyphenols (gentisic acid, phloroglucinol, gallic acid, protocatechuic acid), flavonoids (i.e., rutin, quercetin, myricetin, flavones, flavonols, flavanones, chalcones, hesperidin and flavan-3-ols, isoflavones, methylated flavones), lignins, tocopherols, tannins, and phenolic acids and hydroquinones, phospholipids particularly phosphatidylcholine, terpenoids, peptides, and other antioxidative substances, which directly or indirectly contribute to the inhibition or suppression of oxidation processes [65][66][67][68]. Phenolic phytochemicals act as antioxidants to stop the formation of free radical and oxidation of unsaturated lipids and low-density lipoprotein which is responsible for cardiovascular diseases [69]. Fujimoto and Kaneda [70]   marine algae out of which 60% showed the antioxygenic effect and chloroform soluble extract of brown algae showed the maximum antioxygenic effect. Anggadiredja et al. [71] reported that the antioxidant activity in methanol extract of Sargassum polycystum and n-hexane of Laurencia obtusa was more active than the diethyl ether.

Antimicrobial Activity.
Antimicrobials are the substances that kill or inhibit the growth of microorganisms while antibiotics and antifungals are the medicines which help to kill bacteria and fungus, respectively. Antimicrobial substances generally affect the microbial cells, attacking the cell membrane's phospholipid bilayer, degrading the enzyme systems, and disrupting the genetic material of the microorganisms [72]. Secondary metabolites from seaweeds such as polyphenols can disrupt the microbial cell permeability, interfere with membrane function/cellular integrity, and cause cell death [73]. Sieburth detected the first antibiotic compound acrylic acid, formed from dimethylpropiothetin in the microalga Phaeocystis pouchetii (class Coccolithophyceae). Acrylic acid is isolated from Ulva (formerly Enteromorpha) and Ulva australis (formerly Ulva pertusa) which is responsible for antibacterial action [38]. Sodium alginate from red seaweeds showed antibacterial action against E. coli and Staphylococcus [37]. Halogenated aliphatic compounds (halogenated heptanones, haloacetones, and halobutanone) occurring in genera Asparagopsis and Bonnemaisonia (Rhodophyta) showed antibiotic activity against Bacillus subtilis, Staphylococcus, Fusarium, and Vibrio [38]. Rajauria et al. [74] suggested that the algal polyphenols such as tannins, quinones, flavones, flavonols, phlorotannins, and flavonoids are responsible for the antimicrobial activity. Methanolic extracts of Himanthalia elongata showed antibacterial activity against food spoilage (E. faecalis and P. aeruginosa) and pathogenic bacteria (L. monocytogenes and S. abony) [74]. Terpenes, phlorotannins (isolated from Ecklonia cava subsp. kurome formerly E. kurome, Ecklonia cava, and Fucus vesiculosus), and lipophilic compounds have shown antimicrobial action against Gram-positive and Gram-negative bacteria [75]. Along with polyphenols, algal polysaccharides also represent antimicrobial activity by recognizing and binding on glycoprotein receptors of bacterial surface which is attributed to disrupting the bacterial cell [72].

Anti-Inflammatory Activity.
Anti-inflammatory substances are those which reduce inflammation or swelling. Inflammation occurs due to the movement of increasing leucocytes from blood to tissues [76] and causes dysfunction and various diseases such as carcinogenesis, rheumatoid arthritis, Crohn's disease, osteoarthritis, ulcerative colitis, and sepsis [77]. Macrophages release inflammatory factors, viz., nitric oxide (NO), inducible nitric oxide synthase (iNOS) tumor necrosis factor-α, interleukin-1β, and prostaglandin E2. Lipopolysaccharides (LPS) trigger inflammation in macrophages and induce the production of proinflammatory cytokines by activating a set of intracellular signalling cascades [78]. e first example of diphenyl ether extract from green seaweed Cladophora vagabunda (formerly Cladophora fascicularis) was isolated to develop an anti-inflammatory compound, 2-(20,40-dibromophenoxy)-4,6-dibromoanisole.
is compound helps to prevent the growth of bacteria such as Bacillus subtilis, Escherichia coli, and Staphylococcus aureus [79]. Other anti-inflammatory compounds include macrolides, lipophorins A 142 and B 143, and bromophenol metabolites named vidalols A and B which have been isolated from the surface of the brown alga Lobophora variegata [80] and red algae Osmundaria obtusiloba (formerly Vidalia obtusiloba), respectively, and compound vidalols A and B that act through the inhibition of phospholipase enzyme [81]. Alginate also showed an antiinflammatory effect, and it has no adverse effect on human health [37]. Along with this seaweed, sulphated polysaccharides from the brown seaweeds (Sargassum wightii and   [82][83][84]. Seaweeds can therefore be an effective source to combat the symptoms of SARS-CoV-2 virus (coronavirus). Polysulphates contain negative charge due to the presence of sulphate residues and interact with positively charged viral glycoproteins that provide cell contact. Generally, it was known that the antiviral activity of sulphated polysaccharides increases with an increase of molecular weight and degree of sulfation. erefore, the entry of viruses to host cells is restricted due to this complex process involving the binding of the virion envelope with the polyanionic substances [83]. e antiviral compounds isolated from different seaweeds have been presented in Table 3.

Antilipidemic and Hypocholesterolaemic Activity.
e rise of cholesterol level and blood pressure causes cardiovascular diseases in the human body. Bioactive compounds present in seaweeds could prevent hyperlipidemic and hypercholesterolemic effects. e hypocholesterolemic and hypolipidemic response is produced by increasing faecal cholesterol content and by lowering of systolic blood pressure, respectively [110]. Alginates, a sulphated polysaccharide (molecular weight ≥50 kDa), and alginic acid produced from Laminaria sp. could prevent the onset of diabetes, hypocholesterolemia, and obesity [111]. Dietary fibres of seaweeds absorb substances like cholesterol and eliminate them from the digestive system, resulting in hypocholesterolemic and hypolipidemic response [37]. Ethanolic extracts of Caulerpa racemosa, Colpomenia sinuosa, Spatoglossum asperum, Iyengaria stellata, and Solieria robusta are responsible for hypolipidemic activities [110].

Antithrombotic and Anticoagulant
Activity. Alginate, a sulphated polysaccharide, has prothrombotic blood coagulation and platelet activation activity [37]. Fucan, a sulphated polysaccharide extracted from Fucus vesiculosus, possesses the same activity as heparin that suppresses blood coagulation in humans. As compared to heparin, fucan mostly retards the activity of thrombin on fibrinogen [38]. Fucans consist of homo-and heterostructure. Homofucans have α-(1⟶3) and α-(1⟶4) glycosidic linkages with sulphate groups at C-2 that yields antithrombotic and anticoagulant activity [112]. e extracts of seaweeds show activated partial thromboplastin time (APTT) anticoagulant activity, which means that they are mostly effective on the intrinsic and/or common pathways of the coagulation cascade, particularly the extracts of the brown algae, Laminaria digitata and Fucus vesiculosus, and the red alga, Chondrus crispus. L. digitata [113]. Along with these, sulphated-fucans, extracted from Sargassum vulgare and Ascophyllum nodosum, also show anticoagulant and antithrombotic activity [114,115]. Fucan with fucose sulphated at C-3 extracted from Padina gymnospora related to higher anticoagulant activity of heterofucan [112]. e activity is generally related to the molecular weight, charge density, chain length, and the three-dimensional structure of the sulphated polysaccharide that stimulates the coagulation proteins [116].

Anticarcinogenic and Antitoxic
Activity. Low molecular weight (less than 10 kDa) fucoidan obtained by the degradation through gamma-irradiation without removal of sulphate group showed higher cytotoxicity in cancer cells such as HepG-2, AGS, and MCF-7 than high molecular weight fucoidan [117]. e activity of fucoidan by irradiation depends on its low molecular weight, degree of branching/ chain conformation, and sulphate content [118]. Alginate and dietary fibre obtained from seaweeds protect from potential carcinogens [37]. Yamamoto et al. [119] investigated the idea that the hot water extract of brown seaweeds-such as Sargassum fulvellum, Sargassum miyabei (formerly S. kjellmanianum), Saccharina angustata (formerly Laminaria angustata), and Saccharina longissima (formerly L. angustata var. longissima)-contains a nondialyzable fraction of polysaccharide that suppresses the teratogenesis of sarcoma-180 cells hypodermically imbedded into mice. Polysaccharides of Sargassum wightii were extracted, and two fractions were obtained that inhibited the proliferation and migration of breast cancer cells [120]. Fucoidans are sulphated polysaccharides extracted from brown seaweeds like Sargassum wightii, which helps in the suppression of ontogenesis and migration of MDA-MB-231 human breast cancer cells and DMBA-induced tumors in rats by downregulating the PI3 K/AKT/GSK3b pathway [121]. Polyphenols such as phlorotannins and diterpenes synthesized from Desmarestia and Dictyota possesses anticarcinogenic activity [122]. Along with this, a bioactive diterpene from Desmarestia ligulata and Dictyota dichotoma reported a strong cytotoxic effect against leukemia cell lines [123]. Dichloromethane extracts from Dictyota kunthii and Chondracanthus chamissoi reported cytotoxicity against HT-29 and MCF-7 cell lines [124]. Secondary metabolites from Sargassum sp. (S. angustifolium, S. oligocystum, and S. boveanum) such as plastoquinones, polysaccharides, chromanols, tannins, flavonoids, sterols, saponins, and triterpenes showed strong toxicity against MCF-7, HT-29, and HeLa cell lines [125]. Drug (Detoxal) developed from the calcium alginate extract of brown seaweeds reduces the level of lipid peroxidation products, has antitoxic effects on hepatitis, and also normalizes the lipid and glycogen level in the liver [37].

Nori.
e purple laver (red seaweed), Porphyra/Neoporphyra/Pyropia/Neopyropia genera, contains nearly 50 species in the world, of which 20 species are found in Japan that are used as seaweed food called nori [7]. e most Lambda-carrageenan HIV-1, AMV Nakashima et al. [109] common species used for nori are Neopyropia tenera (formerly Porphyra tenera), Neopyropia yezoensis (formerly Porphyra yezoensis), Pyropia columbina (formerly Porphyra columbina), and Porphyra umbilicalis [31]. In Japan, the dried sheets of laver (Porphyra sp.) are used to cover rice balls containing vegetables in sushi rice. Currently, nori is mixed with ready-to-eat foods such as wine, instant soup, and jam to enhance their nutritional content [7]. As per nutritive value, nori seaweed (Porphyra sp.) is rich in vitamin B complex mainly in vitamins B 6 and B 12 [126], dietary fibre, and protein content which are higher in Pyropia columbina. e main fatty acids present are palmitic and eicosapentaenoic acid. It also has high mineral content such as sodium and potassium with intermediate levels of phosphorus, calcium, and zinc [127]. Nori as food provides many health benefits. One such role is associated with the regeneration of red blood cells and decrease in the risk of pernicious anaemia. It also contributes to the normal working of the human neural network and development of the body [31].  ). At a commercial level, kombu items are processed in a dried form and rehydrated in water before use. It is used in the preparation of soup, salads, and condiments [31]. As per nutritive value, Saccharina japonica (formerly Laminaria japonica) consists of alginate gel network and cellulose, including fucoidan and glycoprotein. It is a good source of calcium, sodium, iron, potassium, iodine, and phosphate minerals [128]. It is also a rich source of glutamic acid which is responsible for the "umami" taste [31].

Wakame.
Wakame also belongs to class Phaeophyceae, which is a kelp that is used as food mostly in Japan and China. e most common species of Undaria are Undaria pinnatifida are used in soup preparation such as miso soup in Japan and as side salads with tofu. It is a good source of polysaccharide (fucoidan) and xanthophyll (fucoxanthin) and is rich in soluble dietary fibre that is used as supplement for weight loss [31].

Sea Lettuce.
Sea lettuce belongs to the class Chlorophyta. e nutrient content of seaweed incorporated recipes was higher than nonincorporated seaweed recipes in terms of proximate composition, minerals, and pigments [131]. Ironrich seaweed foods increase the haemoglobin content in the body and carotene acts as an antioxidant to scavenge free radicals and oxygen [131].

Seaweed Spices.
e study conducted by Amudha et al. [132] developed spice adjunct containing edible red seaweed Eucheuma (earlier Kappaphycus alvarezii) as an ingredient. Seaweed-spice adjunct showed an increase in the protein (by 10%), crude fibre content (by 9.4%), and ash content (22.2%) with high amounts of vitamin E and trace amounts of niacin and vitamin B 2 [132]. erefore, seaweed spices could be good sources of vitamins and proteins that are useful to reduce oxidative stress in the body [132].
6.9. Seaweed Pasta. Prabhasankar et al. [133] developed pasta with Japanese seaweed, wakame (Undaria pinnatifida), and Indian brown seaweed (Sargassum marginatum) which was acceptable with better functional activity. ey reported that fucoxanthin was not affected by the pasta making process [133] and antioxidative properties of seaweed incorporated pasta did not reduce with increasing seaweed content (>2.5%) [134].
6.10. Seaweed Noodles. Chang and Wu [135] in their study incorporated green seaweed (Monostroma nitidum) powder in different proportions with or without eggs to develop noodles. Chang and Wu [135] reported that breaking energy, springiness, and extensibility of freshly cooked noodles reduced, and cooking yield increased significantly with the incorporation of increased concentrations of seaweed [135]. Keyimu [136] incorporated Gracilaria seaweed powder to develop alkaline noodles with high nutritional quality that were rich in fibre content.
6.12. Seaweed Coffee. Kumar et al. [11] prepared seaweed infused coffee from Indian brown seaweed (Sargassum wightii) with 1%, 3%, and 5% seaweed powder. ey reported that, with an increase in the concentration of seaweed in coffee, there is an increase in antioxidant activity. Along with this, Kumar et al. [11] analysed thermal, spectral, and rheological characteristics of seaweed coffee. e authors found that all the seaweed coffee samples were acceptable from a sensory standpoint.

Seaweed Cookie and Sauce.
Oh et al. [138] reported the preparation of seaweed cookies from four different Korean seaweeds, viz., Ulva linza (formerly Enteromorpha linza), Codium fragile, Sargassum fulvellum, and Sargassum fusiforme (formerly Hizikia fusiformis). Cookies prepared from 5% seaweed powder were found to be similar to the control in spread factor, moisture content, and flavor (masking the fishy smell of seaweeds).
Afonso et al. [27] incorporated brown seaweed Gongolaria abies-marina (formerly Treptacantha abies-marina) for cookie and sauce preparation. Sauces and cookies differed in their elemental composition, whereas minerals (K, Ca, Mg, Na, P, and Zn), phenolic content, and antioxidant activity were present in higher quantities in the sauces. Also, 3% incorporation of seaweed in cookie and 2% in sauce were found to be acceptable.

Future Prospects
Caulerpa racemosa, Ulva lactuca (formerly Ulva fasciata), Chnoospora minima, Padina gymnospora, and Acanthophora spicifera are good sources for amino acids and are rich in lysine and methionine amino acids. erefore, these seaweeds are utilized for the formulation of highly nutritive food products with cereals and legumes such as seaweedbased bread, biscuits, and idly which provide a balanced diet to the individual.
Not only is acceptability of nutrient-rich seaweeds scarce, but also the processed food industry has not utilized them effectively to develop seaweed-based functional food products and nutraceuticals. Also, agricultural conditions are becoming hostile due to rapid urbanization and climate change which results in a reduction of agriculture produces. erefore, seaweed-based food is one such unexplored area that needs attention and can provide a suitable solution for this problem. Also, products formed from sulphated polysaccharides (agar, carrageenan, fucoidan, laminaran, and ulvan) of seaweeds may vary in their chemical composition because it depends on hostile environmental conditions such as location and time of harvest. erefore, there is a need to standardize the commercial product prepared from an algal polysaccharide. Also, sulphated polysaccharides from seaweeds may be used as encapsulating material for micro-and nanoencapsulation-based applications.
ere is a need to optimize the methods for extraction, quantification, and purification of bioactive compounds (fucoidan, ulvan, fucoidan, and phloroglucinol) from seaweeds. e combination of bioactive components of seaweed with drugs acts as high-value therapeutic agents which may significantly reduce the ill effects on health. To find the possibility of incorporating seaweeds in food for the development of value-added products, the antimicrobial activity of the seaweed against bacteria and fungi should be carried out.
Toxicity, allergen, and microbial studies should be examined for seaweeds before utilization to develop functional foods. e effect of incorporation of seaweeds in a food item and changes in physicochemical characteristics during processing and interaction with body metabolism is also an interesting idea that needs to be evaluated through in vivo studies.
Different types of seaweeds such as Gracilaria, Sargassum, Ulva, and Eucheuma have been used in different varieties of foods (noodles, pasta/coffee, pickle, and spices, respectively) for the development of seaweed-based food and beverages. erefore, to enhance seaweed application in food, more research will be needed to know the processing technologies, compositional standards, and human gut interaction.

Conclusions
e present findings provide information on the antioxidant potential, nutritional value, and therapeutic activity of seaweeds that will be helpful for the development of seaweed-based food and supplements for the food industry. e incorporation of seaweeds in food may solve health problems emerging as a result of protein, mineral, and carbohydrate deficiencies. e bioactive compounds extracted from seaweeds provide multifold therapeutic activities (antitumor, anticancer, antithrombin, etc.) that make it essential to popularize the use of seaweeds in commercial food products as a natural source of antioxidants.

Data Availability
All data used to support this study are available within the article.

Conflicts of Interest
e authors declare no conflicts of interest.