5.2.1. Biomedical Applications of Seaweeds

Bioactive chemicals found in seaweeds have features that make them appealing for biomedical applications. Many species of seaweeds have been employed in traditional medicine for a long time, notably in Asian nations, against goiter, nephritic disorders, anthelmintic, catarrh, and a few other ailments as medicaments or pharmaceutical auxiliaries, long before scientific study information [316]. *Fucus vesiculosus* has been used as a medicinal drug, primarily due to its iodine content, for obesity defects and goiters [316], for the treatment of sore knees [317], healing wounds [318], and also as herbal teas for their laxative effects [319]. The application of different seaweeds is presented in Table 10.

**Table 10.** Biomedical effects of seaweed bioactive compounds.



#### **Table 10.** *Cont.*

Chondrus crispus (Rhodophyta) carrageens have been used as mucilage against diarrhea, dysentery, gastric ulcers, and as a component of several health teas, such as for colds, for a long time. *Gelidium cartilagineum* (Rhodophyta) has been used in pediatric medicine in Japan for colds and scrofula [284]. *Ulva lactuca* (Chlorophyta) has been used for gout and as an astringent in folk medicine [284]. Rhodophyta extracts are very promising natural chemicals that could be used in biomedicine. Many species of Asian seaweeds are employed in traditional medicine, including *Gracilaria* spp. (Rhodophyta), which is used as a laxative, *Sargassum* spp. (Phaeophyceae), which is used to treat Chinese influence, and *Caloglossa* spp., *Codium* spp., *Dermonema* spp., and *Hypnea* spp. (Rhodophyta) [327].

Carrageenans' biological actions make them attractive candidates for future antitumoral therapeutics since they activate antitumor immunity [328]. Kappaphycus species (Rhodophyta), for example, are used to treat ulcers, headaches, and tumors [327]. Antitumoral efficacy of carrageenans derived from Kappaphycus striatum against human nasopharyngeal carcinoma, human gastric carcinoma, and cervical cancer cell lines [329]. The bioactivity of chemicals from various Laurencia species (Rhodophyta) was investigated. In vitro, certain halogenated metabolites of *Laurencia papillosa* showed action against Jurkat (acute lymphoblastic leukemia) human tumor cells [330]. Laurencia obtuse extracts, specifically three sesquiterpenes, have been extracted and tested against Ehrlich ascites cancer cells. The sesquiterpenes were found to have antitumoral action against Ehrlich ascites cells [331]. *Gracilaria edulis* ethanol extracts showed antitumor efficacy in mice with ascites tumors [332].

*Undaria pinnatifida* (Phaeophyceae) has anti-inflammatory qualities and can be used to treat postpartum depression in women. This alga can also be used to treat edema and as a diuretic. Celikler et al. [333] investigated the antigenotoxic effect of *Ulva rigida* extracts in human cells in vitro (Chlorophyta).

Seaweeds have been suggested as a way to avoid neurogen-erative illnesses in investigations over the last decade [334]. Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and Amyotrophic Lateral Sclerosis (ALS) are the most frequent [334]. According to Bauer et al., several studies highlighted the use of algal polysaccharides for the treatment of neurodegenerative illnesses [335]. Park et al. [336] found that mice treated with fucoidan extracts from Ecklonia cava had better memory and learning; consequently, the study implies favorable results in future human trials. In comparison to the control group, mice treated with polysaccharide isolated from *Sargassum fusiforme* demonstrated enhanced memory and cognition [337]. Dieckol and phlorofucofuroeckol, two phlorotannins from Ecklonia cava, are linked to an increase in the main central neurotransmitters in the brain, particularly Acetylcholine (ACh) [338]. Ahn et al. [339] investigated *Eisenia bicyclis* phlorotannins and found that 7-phloroeckol and phlorofucofuroeckol A were powerful neuroprotective agents against induced cytotoxicity, while eckol had a weaker impact.

#### 5.2.2. Pharmaceutical Applications of Seaweeds

Bioactive chemicals from seaweeds are used in the pharmaceutical industry to help develop new formulations for revolutionary treatments and to replace synthetic components with natural ones. Bioactive chemicals found in seaweeds have important pharmacological properties, including anticoagulant, antioxidant, antiproliferative, antititumoral, anti-inflammatory, and antiviral effects [340] (Table 11).

**Table 11.** The potential pharmacological activity of brown, red and green seaweeds.


Fucoidans extracted from *Laminaria cichorioides*(Phaeophyceae) [351] and Fucus evanescens [352] behave like heparin in both in vitro and in vivo experiments, demonstrating anticoagulant activity by accelerating the development of antithrombin III to inhibit the effect against thrombin.

Fucoidans have a variety of characteristics. Pozharitskaya et al. [353] investigated the antioxidant, anti-inflammatory, anti-hyperglycaemic, and anticoagulant bioactivities of fucoidans isolated from *Fucus vesiculosus*. Even though their free-radical scavenging activity was lower than that of synthetic antioxidants, it was comparable to that of the natural antioxidant quercetin, which is found in plants. Furthermore, inhibition of both isoforms of the pro-inflammatory cyclooxygenase (COX-1) enzymes has been demonstrated, making fucoidans isolated from *Fucus vesiculosus* interesting substances for anti-inflammatory natural medicines [353]. Fucoidans from *Fucus vesiculosus* also have a role in fucoidan's suppression of the enzyme DPP-IV. This enzyme is involved in the breakdown of incretin hormones, which prevents greater levels of glucose in the blood (postprandial hyperglycemia); a new

pharmaceutical company is developing DPP-IV inhibitors to lower blood glucose levels and ensure anti-hyperglycaemic effects. As a result, according to Pozharitskaya et al. [353], fucoidans may be engaged in anti-hyperglycaemic activity via DPP-IV inhibition. *Sargassum fulvellum* (Phaeophyceae) has been found to contain a variety of bioactive compounds, including phlorotannins, grasshopper ketone, fucoidan, and polysaccharides, according to previous research. For years, *Sargassum fulvellum* extracts have been researched for their various pharmacological effects, including antioxidant, anticancer, anti-inflammatory, antibacterial, and anticoagulant properties [354].

Sargassum fulvellum extracts were studied for disorders such a lump, swelling, testicular discomfort, and urinary tract infections [355]. Agar made from red algae is frequently used in biomedicine as a suspension component in medicinal solutions and prescription goods, as well as anticoagulant and laxative agents in capsules [356]. The red algae *Gracilaria edulis* is well-known around the world for its biological and medicinal qualities. *Gracilaria edulis* extract exhibited antidiabetic, antioxidant, antibacterial, anticoagulant, anti-inflammatory, and antiproliferative characteristics [357]; consequently, these compounds could be used in new pharmaceutical formulations. Furthermore, Gunathilaka et al. [358] investigated the in vitro hypoglycemic efficacy of *Gracilaria edulis* phenolic, flavonoid, and alkaloid extracts. The suppression of carbohydrate-digesting enzymes, glucose absorption, and the generation of antiglycation end products demonstrated the red alga's hypoglycemic potential. In vivo, *Ulva rigida* (Chlorophyta) has been shown to have a hypoglycemic impact [359].

Seaweeds' antiviral qualities make them an excellent alternative for improving the health of infected persons; also, their use in pharmaceuticals will provide new and natural antiviral drugs that can replace synthetic chemicals. Furthermore, when compared to the creation of synthetic antivirals, the use of bioactive components from seaweeds is less expensive [360]. Antiviral activity of macroalgae has been discovered to protect against a variety of viruses, including HIV, Herpes Simplex Virus (HSV), genital warts [361], and hepatitis C (HCV) [362]. HSV [363], Encephalomyocarditis virus, Influenza "A" virus [364], and human metapneumovirus [365] are only a few of the viruses that Chlorophyta species have been shown to be effective against. The antiviral action of macroalgae is linked to a variety of substances such as as fatty acids and diterpenes, but most notably to the presence of Seaweed bioactive compounds [366], which can inhibit virus multiplication or help the immune system combat viral infection.
