Red Macroalgae: History
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Red Seaweed “Rhodophyta” are an important group of macroalgae that include approximately 7000 species. They are a rich source of structurally diverse bioactive constituents, including protein, sulfated polysaccharides, pigments, polyunsaturated fatty acids, vitamins, minerals, and phenolic compounds with nutritional, medical, and industrial importance. Polysaccharides are the main components in the cell wall of red algae and represent about 40–50% of the dry weight, which are extensively utilized in industry and pharmaceutical compounds, due to their thickening and gelling properties. The hydrocolloids galactans carrageenans and agars are the main red seaweed cell wall polysaccharides, which had broad-spectrum therapeutic characters. Generally, the chemical contents of seaweed are different according to the algal species, growth stage, environment, and external conditions, e.g., the temperature of the water, light intensity, nutrient concentrations in the ecosystem. Economically, they can be recommended as a substitute source for natural ingredients that contribute to a broad range of bioactivities like cancer therapy, anti-inflammatory agents, and acetylcholinesterase inhibitory. This entry touches on the main
points of the pharmaceutical applications of red seaweed, as well as the exploitation of their specific compounds and secondary metabolites with vital roles.

  • bioactive compounds
  • drugs
  • seaweed
  • Rhodophyta

1. Introduction

‏Macroalgae are macroscopic benthic marine algae (seaweed) living in the intertidal zone. They are characterized by autotrophic nutrition and fast-growth; they do not need land for cultivation and their growth rate is faster than terrestrial plants [1].

Red seaweed are the critical source of numerous bioactive compounds, in contrast with the other two groups of green and brown seaweed like polysaccharides “floridean starch and sulfated galactans, such as carrageenans or agars”, minerals, unsaturated fatty acids, amino acids, vitamins, phycobiliproteins, other pigments, phycolectins and mycosporine-like amino acids, which have many biological and industrial applications [2][3].

The protein content in red seaweed varied between 10–50% of the dry weight and being higher than macroalgal groups and some foods [4]. In addition, they contain the essential amino acid, about 25–50% of the total amino acids, is like other protein sources like leguminous plants [4].

Red and green seaweed contain the largest amount of phenolic compounds like flavonoids, phenolics acids, and bromophenols, which had different medical applications, due to the reaction of these components with proteins, e.g., enzymes or cellular receptors. While, phlorotannins, are the major polyphenolic secondary compounds synthesized only in marine brown seaweed [5].

For decades and at present, seaweed is used in food in many countries, as well as in traditional drugs and cosmetics, due to their richness in natural metabolites. The therapeutic trend has begun searching forward for new medications from natural products like algae. Since ancient times, macroalgae are used for treating different diseases. The approximate numbers of biochemicals are more than up 700 from red species. The majority of these contents have shown promising biological abilities, including antimicrobial, antiviral, antitumor, antioxidant, anticoagulant, anti-inflammatory, antidiabetic, antiallergic, and analgesics efficiencies [5][6].

2. Anti-Obesity Activity

Obesity is excessive fat accumulation, and is known to increase the risk of many dangerous diseases like type II diabetes, hypertension, hyperlipidemia, and cardiovascular diseases. Obesity is gaining increased attention because of the high expense and dangerous symptoms of anti-obesity drugs. Rhodophyta species were shown to have anti-obesity properties [7].

The ethanolic extract of Grateloupia elliptica (60%) reduced the accumulation of the lipid in 3T3-L1 cells and inhibited the adipogenic proteins expression. In addition to a significant decreasing in body weight of C57 BL/6J male mice, as well as reducing white adipose tissue (WAT) weight, e.g., fatty liver, leptin, total cholesterol, and serum triglycerides contents in vivo without cytotoxic effect [8]. Forty % of Plocamium telfairiae ethanolic extract showed anti-obesity ability via reducing the fat accumulation and suppressed the expression of major adipogenesis factors, like peroxisome proliferator-activated receptor-γ (PPAR-γ),CCAAT/enhancer-binding protein (C/EBP)-α, sterol regulatory element-binding protein 1 (SREBP-1), and phosphorylated ACC (pACC) in 3T3-L1 cells [9]. Seo et al. [10] demonstrated the antidiabetic activity of extract from Gelidium amansii via reduction the accumulation of lipid in 3T3-L1 adipocyte cell line.

Generally, marine algal polysaccharides are considered to be dietary fibers so they are not digested by humans [11]; hence SPs can hinder adipogenesis through the mitogen activated protein kinase (MAPK) in 3T3-L1 pre-adipocytes [12].

3. Antihypertensive Activity

Seaweed exhibits significant anti-hypertensive activities [13]. Macroalgae consumption led to decreased blood pressure, which might be linked to the hypotensive effects of the dietary fiber and their rich nitrate content [14]. The antihypertensive effects of macroalgal peptides maintained a healthy heart by stimulating circulation in the blood vessels, and avoiding deadly conditions, such as heart breakdown, atherosclerosis, and peripheral vascular disease [15].

The secondary metabolites of seaweed act as hypoglycemic agents, reduce blood pressure and regulate cholesterol levels, inhibition of hepatic cholesterol biosynthesis, also for hyperplasia prevention, gastrointestinal, regenerative Nori-peptides from Porphyra yezoensis have the important antihypertensive ability in hypertensive patients, as well as spontaneously hypertensive rats [16].

4. Acetylcholinesterase Inhibitory ‘’Alzheimer’s Disease”

Alzheimer’s disease (AD) is a progressive and degenerative problem in brain regions, chiefly campus, and neocortex responsible for mental functions that reduced neurotransmitter acetylcholine (ACh). AD can prompt amnesia, abnormalities, and cognitive disturbances [17]. In the cholinergic theory, serious damage of cholinergic neurotransmitter AChE in the central nervous system (CNS) gives AD indications [87]. The principle therapeutic strategy against AD is acetylcholinesterase hindrance.

There is very few research reporting on the AChE inhibitory (AChEI) impact of seaweed. The AChEI ability of plant extracts is classified into potent inhibitors (> 50% inhibition), moderate inhibitors (30–50% inhibition), and weak inhibitors (< 30% inhibition) [18]. As clarified in Figure 1, Ochtodes secundiramea extracts exhibited moderate potency (48.59 ± 0.8%), while the red algae Hypnea musciformis (7.21%) and Pterocladia capillacea (5.38%) extracts had a weak action. The AChEI abilities of these algae are related to solely compose of halogenated monoterpenes [19].

Figure 1. TLC qualitative AChEI assay. PC: +ve control, physostigmine (0.03 μg). DCM/MeOH extracts (100 μg) of (1) Hypnea musciformis, (2) Pterocladia capillacea, and (3) Ochtodes secundiramea. TLC elution system: hexane:ethyl acetate:methanol (2:7:1 v/v/v) [19].

The alcoholic extract of Gracilaria corticata (IC50 9.5) and G.; salicornia (IC50 8.7 mg/mL) extracts showed moderate AChEI efficiency [20]. The sulfated polysaccharides from Gelidium pristoides exhibited inhibitory potency on acetylcholinesterase that related to their antioxidant and neuroprotective potentials [21].

Some red seaweed species synthesize homotaurine, aminosulfonate compounds, which could be a promising medicine for Alzheimer’s disease prevention [22].

5. Macroalgae for Skincare

Macroalgae metabolites reduced the appearance of redness and blemishes, the appearance of sun damage, brightening, re-mineralizing, hydrating and firming skin [23]. They have a reaction mechanism toward the hazardous ultraviolet ‘UV-A and -B’ impacts via delivering phenolic compounds, mycosporine, amino acid, and carotenoids, which act as UV-absorbing [24]. The extracts of red seaweed Asparagopsis armata, Gelidium  corneum, Corallina officinalis had skin softness, whitening/lightening, and elasticity restoring anti-aging properties so they can be used as skincare products including creams, oil, soap, mask, or lotion [25]. Agarose from Gracilaria cornea and G.; lemaneiformis are used for skin whitening, due to its anti-melanogenic activity by inhibiting melanin synthesis [26][27]. Fatty acid-like palmitic acid and its derivated ascorbyl palmitate from seaweed are used in cosmetics as emulsifiers and antioxidant agents for anti-wrinkle and anti-aging characteristics [28]. Amino acid extracted from Asparagopsis armata is inserted in some anti-aging lotions [29]. Mycosporine from different Rhodophyta species act as photoprotective substances for skin care products with antioxidant properties [3].

6. Conclusions

There are some species from Rhodophyta whose feasibility medical potential is higher, like Gracilaria spp., Pterocladia spp. Jania spp. and Corallina spp. Due to the economic importance of seaweed, more studies should be undertaken, focusing on improving seaweed production on a large scale by adjusting the culture conditions. Cultivation of economic species in seaweed aquaculture may be the future road for the sustainability of seaweed and controlling the production of active compounds. Optimization extraction methods, purification, and fractionation of bioactive compounds led to the production of more active and safe compounds. Therefore, more clinical studies should be carried out on a large scale for economic production.

This entry is adapted from the peer-reviewed paper 10.3390/molecules25194411


  1. Wan, A.H.; Davies, S.J.; Soler-Vila, A.; Fitzgerald, R.; Johnson, M.P. Macroalgae as a sustainable aquafeed ingredient. Rev. Aquac. 2019, 11, 458–492.
  2. Ismail, M.M.; Gheda, S.F.; Pereira, L. Variation in bioactive compounds in some seaweed from Abo Qir bay, Alexandria, Egypt. Rend Lincei-Sci. Fis. 2016, 27, 269–279.
  3. Torres, M.D.; Flórez-Fernández, N.; Domínguez, H. Integral utilization of red seaweed for bioactive production. Mar. Drugs 2019, 17, 314.
  4. Paiva, L.; Lima, E.; Patarra, R.F.; Neto, A.I.; Baptista, J. Edible Azorean macroalgae as source of rich nutrients with impact on human health. Food Chem. 2014, 164, 128–135.
  5. Gómez-Guzmán, M.; Rodríguez-Nogales, A.; Algieri, F.; Gálvez, J. Potential role of seaweed polyphenols in cardiovascular-associated disorders. Mar. Drugs 2018, 16, 250.
  6. Abu-Khudir, R.; Ismail, G.A.; Diab, T. Antimicrobial, antioxidant, and anti-Tumor activities of Sargassum linearifolium and Cystoseira crinita from Egyptian Mediterranean Coast. Nutr. Cancer 2020.
  7. Kang, M.-C.; Ko, N.K.; Kim, Y.-B.; Jeon, Y.J. Anti-obesity effects of seaweeds of Jeju Island on the differentiation of 3T3-L1 preadipocytes and obese mice fed a high-fat diet. Food Chem. Toxicol. 2016, 90, 36–44.
  8. Lee, H.-G.; Lu, Y.A.; Li, X.; Hyun, J.-M.; Kim, H.-S.; Lee, J.J.; Kim, T.H.; Kim, H.M.; Kang, M.-C. Anti-Obesity effects of Grateloupia elliptica, a red seaweed, in mice with high-fat diet-induced obesity via suppression of adipogenic factors in white adipose tissue and increased thermogenic factors in brown adipose tissue. Nutrients 2020, 12, 308.
  9. Lu, Y.A.; Lee, H.G.; Li, X.; Hyun, J.-M.; Kim, H.-S.; Kim, T.H.; Kim, H.-M.; Lee, J.J.; Kang, M.-C.; Jeon, Y.J. Anti-obesity effects of red seaweed, Plocamium telfairiae, in C57BL/6 mice fed a high-fat diet. 2020.
  10. Seo, M.-J.; Lee, O.-H.; Choi, H.-S.; Lee, B.-Y. Extract from edible red seaweed (Gelidium amansii) inhibits lipid accumulation and ros production during differentiation in 3T3-L1 cells. Prev. Nutr. Food Sci. 2012, 17, 129–135.
  11. Mabeau, S.; Fleurence, J. Seaweed in Food Products, Biochemical and Nutritional Aspects. Trends Food Sci. Technol. 1993, 4, 103–107.
  12. Kim, K.-J.; Lee, O.-H.; Le, B.-Y. Fucoidan, a sulfated polysaccharide, inhibits adipogenesis through the mitogen-activated protein kinase pathway in 3T3-L1 preadipocytes. Life Sci. 2010, 86, 791–797.
  13. Seca, A.M.L.; Diana, C.G.A.; Pinto, D.C.G.A. Overview on the Antihypertensive and Anti-Obesity Effects of Secondary Metabolites from Seaweeds. Mar. Drugs 2018, 16, 237.
  14. Mendis, E.; Kim, S.K. Present and future prospects of seaweed in developing functional foods. Adv. Food Nutr. Res. 2011, 64, 1–15.
  15. Fitzgerald, C.; Gallagher, E.; Tasdemir, D.; Hayes, M. Heart health peptides from macroalgae and their potential use in functional foods. J. Agricul. Food Chem. 2011, 59, 6829–6836.
  16. Saito, M.; Kawai, M.; Hagino, H.; Okada, J.; Yamamoto, K.; Hayashida, M.; Ikeda, T.P. Antihypertensive effect of Nori-peptides derived from red alga Porphyra yezoensis in hypertensive patients. Amer. J. Hypertension. 2002, 15, 210A.
  17. McNamara, Y. Alzheimer’s association international conference (AAIC) copenhagen, denmark-July 12–17, 2014. Drugs Future 2014, 39, 651–656.
  18. Vinutha, B.; Prashanth, D.; Salma, K.; Sreeja, S.L.; Pratiti, D.; Padmaja, R.; Radhika, S.; Amit, A.; Venkateshwarlu, K.; Deepak, M. Screening of selected Indian medicinal plants for acetylcholinesterase inhibitory activity. J. Ethnopharmacol. 2007, 109, 359–363.
  19. Machado, L.P.; Carvalho, L.R.; Young, M.C.M.; Cardoso-Lopes, E.M.; Centeno, D.C.; Zambotti-Villela, L.; Colepicolo, P.; Yokoya, N.S. Evaluation of acetylcholinesterase inhibitory activity of Brazilian red macroalgae organic extracts. Rev. Bras. Farmacogn. 2015, 25, 657–662.
  20. Ghannadi, A.; Plubrukarn, A.; Zandi, K.; Sartavi, K.; Yegdaneh, A. Screening for antimalarial and acetylcholinesterase inhibitory activities of some Iranian seaweeds. Res. Pharm. Sci. 2013, 8, 113–118.
  21. Olasehindea, T.A.; Mabinyaa, L.V.; Olaniranc, A.O.; Okoha, A.I. Chemical characterization, antioxidant properties, cholinesterase inhibitory and anti-amyloidogenic activities of sulfated polysaccharides from some seaweeds. Bioact. Carbohydr Diet. Fibre 2019, 18, 1–10.
  22. Caltagirone, C.; Ferrannini, L.; Marchionni, N.; Nappi, G.; Scapagnini, G.; Trabucchi, M. The potential protective effect of Tramiprosate (homotaurine) against Alzheimer’s disease, A review. Aging Clin. Exp. Res. 2012, 24, 580–587.
  23. Pereira, L. Seaweeds as source of bioactive substances and skin care therapy-cosmeceuticals, algotheraphy and thalassotherapy. Cosmetics 2018, 5, 68.
  24. Chan, J.N.; Poon, B.P.; Salvi, J.; Olsen, J.B.; Emili, A.; Mikhail, A. Perinuclear cohibin complexes maintain replicative life span via roles at distinct silent chromatin domains. Dev. Cell 2011, 20, 867–879.
  25. Leandro, A.; Leonel Pereira, L.; Gonçalves, A.M.M. Diverse applications of marine macroalgae. Mar. Drugs 2020, 18, 17.
  26. Jin, M.; Liu, H.; Hou, Y.; Chan, Z.; Di, W.; Li, L.; Zeng, R. Preparation, characterization and alcoholic liver injury protective effects of algal oligosaccharides from Gracilaria lemaneiformis. Food Res. Int. 2017, 100, 186–195.
  27. Kim, J.H.; Yun, E.J.; Yu, S.; Kim, K.H.; Kang, N.J. Different levels of skin whitening activity among 3,6-Anhydro-L-galactose, agarooligosaccharides, and neoagarooligosaccharides. Mar. Drugs 2017, 15, 321.
  28. Yarnpakdee, S.; Benjakul, S.; Senphan, T. Antioxidant activity of the extracts from freshwater macroalgae (Cladophora glomerata) grown in northern Thailand and its preventive effect against lipid oxidation of refrigerated eastern little tuna slice. Turk. J. Fish. Aquat Sci. 2018, 19, 209–219.
  29. Cotas, J.; Leandro, A.; Monteiro, P.; Pacheco, D.; Figueirinha, A.; Gonçalves, A.M.M.; da Silva, G.J.; Pereira, L. Seaweed Phenolics, From Extraction to Applications. Mar. Drugs 2020, 18, 384.
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