Ulva fasciata Deliles antioxidant properties for the sesquiterpenoids were discovered in green algae when using the free-radical-scavenging assays [98]. The Ulva lactuca is enormously acknowledged to have antioxidant properties in flavonoids [99,100]. Info from animal studies unveiled free-radical-scavenging effects of a reticulate hot water extract, due to which hepatic oxidative stress remained reduced [101]. The total content of phenol from the extract of Cassytha filiformis filiformis (39.31 ± 0.39 mg of AGE/g extract) was markedly higher (p < 0.05) by carrying out Cassytha filiformis antioxidant power ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2′-diphenylpicrylhydrazyl) assays. The extract of C. filiformis (IC50 = 3.49 ± 0.01 and 2.18 ± 0.02 mg/mL) was importantly greater (p < 0.05), so it is indorsed that the C. filiformis’s methanol extract is considered as a treasure of secondary metabolites with antioxidant properties [102].

Green algae are an offering source for cosmetic colorants, phenolic compounds, sterols, vitamins and other therapeutic agents [103]. Some of the bioactive agents (cosmetics) of isolated green algae compounds are used as skin moisturizing and protecting agents, creams with antistretch markings, body ointments, eye balms, face masks, antiaging washing gel, natural sunscreen, body scrubs, face peeling and face salves, firming body liniment, body unguents, purgative gels, fluids, stimulants, shampoos, day and/or night face cream, antielastase, collagen synthesis stimulation, chelating, inducement of collagen making via TGF-β, elastin, proliferation of collagen biosynthesis, anti-photo-aging agents, radical scavengers, colorants, cytoprotective Nrf2-ARE pathway, antiadhesive agents, antiwrinkling, emulsion stabilizers, immune-stimulants, potential for the treatment of histamine-related inflammatory illnesses including atopic dermatitis (AD), inhibition of hyaluronidase, antiallergic, hair growth, adipogenesis inhibitory effect, tyrosinase inhibitors, whitening agents, anticoagulant and topical cosmetic formulations to treat or avoid cellulite, augmented illumination for age spots and skin fall, UV emission defending and comforting, emollient, humectant, oral care, skin conditioning, antifungal and antiseptic, maintaining skin consistency and elasticity, antiacne makeup and many others uses [104].

A further relevant target of algal extracts comprises oral microbes. Ulva linza extracts have antibacterial agents against intermedia Porphyromonas gingivalis and P. intermedia. Bioactive compounds (stearidonic acid) SA and (gamma-linolenic acid) GLA segregated from Ulva linza proved efficient antibacterial activity against P. intermedia and Porphyromonas gingivalis with MIC values of 39.06 µg/mL and 9.76 µg/mL, respectively [105]. Ulva lactuca showed an important antibacterial action against Escherichia coli while Ascophyllum nodosum was extra perceptive on Micrococcus luteus and Brochothrix thermosphacta. Avrainvillea sp. consists of bromophenols that pointed out inhibitory activity against both Bacillus subtilis and Staphylococcus aureus, which were also active against Pseudomonas aeruginosa as well as Escherichia coli, Serratia marcesens and Candida albicans [8]. Utricularia rigida composed of fatty acid obtained from Ghar el Melh lagoon can be used for the development of innovative antibacterial ingredients against human marine diseases [106].

Currently, there is an urge of vaccine which might proceed to immunization against the deadly virus SARS-CoV-2 (COVID-19), but some traits of numerous sea weeds may provide an insight into possible remedies to this global pandemic in the near future. Several marine algae species possess large numbers of hierarchical sulfated polysaccharides which are proved to arrest the replication phase of enveloped viruses such as Ulvans [107] and Caulerpa [108]. A well-known alkaloidal compound caulerpin was studied In-silico for its antiviral activity against SARS-CoV-2 proteases as a monotherapy and also as a combination therapy with other predicted compounds having efficacy against SARS-CoV-2 such as chloroquine, hydro chloroquine, lopinavir and simeprevir. The results have revealed that caulerpin and its derivatives have shown high binding energies towards SARS-CoV-2 protein receptors as compared to all other predicted drugs. Furthermore, it has been revealed that, by adding different functional groups to the caulerpin structure like vinyl, halogen and NH₂ enhanced the antiviral activity; as well, by adding alkyl groups, are decreased the binding affinities which in turn also decline antiviral activity. In addition, the molecular simulations data showed that the control drug simeprevir and caulerpin derivatives in combination have not shown any fluctuations in the protein and was stable, evidencing that caulerpin and its derivatives can be used as a combinational agent with other drugs, in order to destabilize the SARS-CoV-2 spikes protein [108].

Dichloromethane methanol extracts are derived from two green algae named as Udotea flabellum and U. Conglutinate chlorophycean algae. The anticancer activity was observed on human melanoma cell line HeLa [109] comparing 22.5 vs. 22.2 µg/mL, respectively. It has been stated that Udotea flabellum extracts present antiproliferative activities of the cell lines HeLa, SiHa and KB [109]. Enteromorpha intestinalis and Rhizoclonium ripariums’ methanol extracts with IC50 values 309.048 ± 3.083 µg/mL and 506.081 ± 0.714 µg/mL were proved to be antiproliferative against cervical cancer cell line HeLa [110]. Enteromopha prolifera is another genus of green algae that had a suppressive activity with 51.7% for Erhlich’s carcinoma inhibition [111]. Caulerpa-isolated compounds were assayed against human cancer cell lines A 549 (human cancer carcinoma) and HL-60 (promyelocytic leukemia cells), among isolated compounds, α-tocopherol quinone showed restrained cytotoxicity towards HL-60 and low cytotoxicity towards A-549 [14,55]. Caulerpin’s IC50 values were recorded 20 µM against certain cancer cell lines (T47-D, MCF-7, MDA-MB-231, PC3 DU145, HMEC, HCT116, HT29, LOVO and SW480) but its mechanism of action disclosed that caulerpin obstructs hypoxia-inducible factor 1 (HIF-1) at 10 µM concentration and blocks the induction of HIF-1α protein, an essential oxygen-regulated subunit, under hypoxic circumstances. Caulerpin also has an effect on the migration of tumor cells when the concentration-dependent migration of metastatic MDA-MB-231 cells has been suppressed, with better results being noticed at 30 µM. Operation with Caulerpin in vivo combines with 3-bromopyruvate on xenografts implanted on an athymic nude mouse model carrying SW480. Combination therapy with caulerpin presented fabulous tumor regression. Additional inspection shows that in this combination therapy proliferating cell nuclear antigen (PCNA) and phosphorylated mammalian target phrase rapamycin (p-mTOR) are prevented, showing the important role of adenosine monophosphate-activated protein kinase (AMPK)/mTOR pathway in anticancer therapy. The cultivation of green algae is the best practice to increase the phenol and lipid content and thus improve SI on cancer cells, mostly on the SiHa and Hep-2 cell lines [112]. Through the P13K/Akt pathway, the hot water extract of Capsosiphon fulvescens’s polysaccharides determined apoptosis of gastric cancer cells, as well as dimethyl sulfoniopropionate and tertiary sulfonium metabolites, presented anticancer activity in mice with Ehrlich ascites carcinoma [113]. Nigricanosides A is a glycolipid obtained from Avrainvillea nigricans, being used in breast cancer cells in mitosis; sesquiterpenoid, known as Caulerpenyne from Caulerpa taxifolia, is used in colorectal cancer; sulfated polysaccharide, from Ulva intestinalis, is used in reducing tumor mass; sterol, from Codium fragile, is used in inducing apoptosis; glycoprotein from Codium decorticatum is used to induce apoptosis on MDA-MB-231 breast cancer cells [114]. A novel compound named as 25-hydroperoxy-6β-hydroxycholesta-4,23(E)-dien-3-one, extracted from Galaxaura marginata, displayed cytotoxicity against P338 (lymphocytic leukemia cells), A549 (human lung adenocarcinoma epithelial cell lines) and KB (KERATIN-forming tumor cell line HeLa). Cladophoropsis vaucheriaeformis shows tumorigenic behavior against murine lymphoid leukemia L1210 cells [115]. Chaetomorpha compressa, the marine green algae, has been proven to be a better anticancer agent against human breast carcinoma cells [116] and shows its antiapoptotic effects against human colon cancer cells HCT-116 [117] In short, green algae are the treasure of bioactive anticancer metabolites.