In this study crude extracts of Turbinaria decurrens, Padina pavonica, Sargassum muticum and Sargassum acinarium (Phaeophyta); Ulva lactuca (Chlorophyta) and Pterocladia capillacea (Rhodophyta) seaweeds were tested to evaluate their antioxidant properties and antidiabetic potential on α-amylase and α-glucosidase starch hydrolyzing enzymes. The results showed that all analyzed seaweeds exhibited antioxidant effects using DPPH (2,2-Diphenyl-1-picrylhydrazyl), reducing power and total antioxidant capacity assays in addition to antidiabetic activity that all depended on the species and the extract solvent. Among the tested extracts, acetone extract of Turbinaria decurrens showed the highest antioxidant activity and inhibitory effects for α-amylase (96.1%) and α-glucosidase (97.4%), respectively which was related with its total phenolic content and antioxidant activity. In vitro, the extract showed no toxicity against fibroblast normal cell lines at lower concentration of 250 µg/ml. Gas Chromatography-Mass Spectrum analysis (GC-MS) of this acetone extract showed the presence of different bioactive compounds mainly cyclotrisiloxane, hexamethyl which could be responsible for its antioxidant and antidiabetic activities. The study results suggest that brown seaweeds especially T. decurrens can be used as antioxidant ingredients and as potent reducing drug for postprandial hyperglycemia.

Currently, algae arouse a growing interest in the pharmaceutical and cosmetic area due to the fact that they have a great diversity of bioactive compounds with the potential for pharmacological and nutraceutical applications. Due to lifestyle modifications brought on by rapid urbanization, diabetes mellitus, a metabolic illness, is the third largest cause of death globally. The hunt for an efficient natural-based antidiabetic therapy is crucial to battling diabetes and the associated consequences due to the unfavorable side effects of currently available antidiabetic medications. Finding the possible advantages of algae for the control of diabetes is crucial for the creation of natural drugs. Many of algae’s metabolic processes produce bioactive secondary metabolites, which give algae their diverse chemical and biological features. Numerous studies have demonstrated the antioxidant and antidiabetic benefits of algae, mostly by blocking carbohydrate hydrolyzing enzyme activity, such as α-amylase and α-glucosidase. Additionally, bioactive components from algae can lessen diabetic symptoms in vivo. Therefore, the current review concentrates on the role of various secondary bioactive substances found naturally in algae and their potential as antioxidants and antidiabetic materials, as well as the urgent need to apply these substances in the pharmaceutical industry.

Microalgae are rich sources of structurally novel and biologically activemetabolites. Primary and secondary metabolites produced by theseorganisms which have drawn interest of the pharmaceutical industries.In this regard, the study aimed to screening of phytochemicalcompounds and evaluate the total phenolic content and the antioxidantactivity of Chlorella vulgaris. The antioxidant activity of C. vulgariswas tested by 2,2-diphenyl-1-picrylhydrazyl DPPH radical scavengingmethod, reducing power assay and the total antioxidant capacity (TAC).The phytochemical screening exhibited the presence of alkaloids,flavonoids and phenols in all tested solvents which exhibited severalbiological activities. Among the different solvents, acetone extractexhibited the highest scavenging activity with (50.81%). Also, showedreducing power activity estimated with 1.95 mg AAE/g DW andantioxidant capacity recorded 2.58 mg AAE/g DW. In addition,considerable amount of the total phenolic has been detected in acetoneextract recording 3.17 mg GAE/g DW. The results revealed that there isa strong correlation between the antioxidant activity assays and thephenolic content of Chlorella vulgaris.Thus, the green microalga Chlorella vulgaris in dietary supplements willbe effective mediator in scavenging free radicals as it contains widevariety of bioactive compounds.

The oleaginous genera Nannochloropsis and Microchloropsis are recognized for their lipid accumulation capacity. Microalgal lipid accumulation is triggered by nitrogen starvation, negatively affecting photosynthesis and growth. Moreover, light and temperature play pivotal roles in microalgal physiology, lipid accumulation and composition. This study focuses on comparing the responses of eight microalgal strains from Nannochloropsis (N. oceanica Necton, N. oceanica IMET1, Nannochloropsis. sp. CCAP211/78, N. oculata, and N. limnetica) and Microchloropsis (M. gaditana CCFM01, M. gaditana CCMP526, and M. salina) to light, temperature, and nitrogen availability. Biomass, lipid content and productivities were monitored under different light intensities (150 (LL) and 600 μmol photons m⁻² s⁻¹ (HL)) and temperatures (15, 25, 30℃) under nitrogen (N-) starvation and replete conditions. Under N-starvation and HL, N. sp. exhibited the highest lipid content (59%) and productivity (0.069 g L^-1 day^-1), while N. oculata had the lowest lipid content (37.5%) and productivity (0.037 g L^-1 day^-1) among the eight strains. Notably, M. gaditana CCFM01 achieved the highest EPA content (4.7%), contrasting with N. oceanica IMET1 lowest EPA content (2.9%) under 150 μmol photons m⁻² s⁻¹ and N-repletion. The response to temperature fluctuations under LL was strain-dependent. Microchloropsis salina and M. gaditana CCFM01 demonstrated the highest and lowest lipid productivities (0.069 g L^-1 day^-1 and 0.022 g L^-1 day^-1, respectively) at 15℃ under N-starvation. Moreover, significant EPA accumulation across various strains was observed in N. oculata (5.7%) under N-repletion at 15°C, surpassing M. gaditana CCFM01 by 40%. Ultimately, the physiological responses to cultivation conditions vary markedly among microalgal strains, even within the same genus or species. This knowledge is essential for selecting suitable strains for the efficient microalgal lipid production industry. Graphical Abstract Optimi zing cultivation conditions for the maximal lipid production in Nannochloropsis andMicrochloropsis

The study evaluated different extracts of Spirulina platensis using acetone, methanol, ethanol as well as water solvents for their antioxidant and antidiabetic potential. The results showed that all S. platensis extracts exhibited antioxidant activity by using DPPH (2, 2-Diphenyl-1-picrylhydrazyl), reducing power and total antioxidant capacity assays; in addition to their antidiabetic activity which was dependent on the used solvent. Among the tested extracts, S. platensis methanolic extract exhibited the highest antioxidant activity for all the tested assays and the maximum inhibitory effects for α-amylase (96.46 %) and α-glucosidase (97.42 %) diabetic enzymes. Spirulina methanolic extract showed no toxicity on normal cell lines using MTT assay. Gas Chromatography-Mass Spectrum (GC-MS) analysis of the methanolic extract revealed the presence of different bioactive compounds mainly phytol, 1-monolinoleoylglycerol trimethylsilyl ether, cholestan-3-ol, 2-methylene-(3β,5α) and fatty acids. These compounds might be acted synergistically to exert their obtained antioxidant and antidiabetic activity. For the in vivo study, administration of S. platensis methanolic extract (at 15 and 10 mg/Kg body weight (BW) caused antihyperglycemic activity by reducing the elevated blood glucose level. A remarkable decrease in different liver, kidney functions and hyperlipidemia related to diabetes were also detected. Furthermore, the methanolic extract treatment increased the body weight, total protein, albumin and hemoglobin levels as compared with the alloxan induced diabetic rats. Furthermore, treatment of diabetic rats with the extract improved liver and pancreas histopathological disorders related to diabetes. These results recommended using S. platensis methanolic extract in developing medicinal preparations for treatment of diabetes and its related symptoms.

Upon Seeking natural and safe alternatives for synthetic medicines to treat many chronic diseases, seaweeds have offered a promising resource to produce numerous bioactive secondary metabolites. Through in vivo investigations, Turbinaria decurrens acetone extract (AE) revealed its antidiabetic activity against alloxan-induced diabetic rats. Treatment of rats with T. decurrens AE at 300 and 150 mg/Kg doses revealed antihyperglycemic activity by reducing the elevated blood glucose level. A remarkable decrease in the liver, kidney functions, and hyperlipidemia related to diabetes were also detected. Administration of the same extract also showed a recovery in body weight loss, total protein, albumin, and haemoglobin levels compared with untreated diabetic rats. Furthermore, treatment of rats with the same extract improved liver and pancreas histopathological disorders related to diabetes. These effects may be attributed to the presence of bioactive phytochemicals and antioxidant components in T. decurrens AE mainly cyclotrisiloxane, hexamethyl, and cyclic diterpene 3,7,11,15-tetramethyl-2-hexadecen-1-ol (phytol alcohol). Besides, other valuable secondary metabolites, as phenols, flavonoids, alkaloids, terpenoids, steroid and glycosides, which were documented and published by the same authors in a previous study. The obtained results in the present study recommended using T. decurrens AE in developing medicinal preparations for treatment of diabetes and its related symptoms.