Effect of solvents on bioactive compounds and antioxidant activity of Padina tetrastromatica and Gracilaria tenuistipitata seaweeds collected from Bangladesh

Seaweeds are now recognized as a treasure of bioactive compounds. However, the bioactivity of seaweed originating in Bangladesh is still unexplored. So, this study was designed to explore the secondary metabolites and antioxidant activities of solvent extracts of Padina tetrastromatica and Gracilaria tenuistipitata. Phytochemical screening and FTIR spectra confirm the diverse type of bioactive compounds. Antioxidant activity of extracts were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2, 2-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), reducing power (RP), phosphomolybdenum, hydrogen peroxide and nitric oxide (NO) scavenging assays. Here, methanolic extract of P. tetrastromatica showed highest amount of total phenolic content (85.61 mg of GA/g), total flavonoid content (41.77 mg of quercetin/g), DPPH (77.07%), ABTS (77.65%), RP (53.24 mg AAE/g), phosphomolybdenum (31.58 mg AAE/g), hydrogen peroxide (67.89%) and NO (70.64%) assays compared to its methanolic extracts of G. tenuistipitata. This study concluded that methanol as a solvent extract of brown seaweed (P. tetrastromatica) exhibited bioactivity and antioxidant potentiality which will be useful for pharmacological as well as in functional food application.

Effect of Solvents on Bioactive Compounds and Antioxidant Activity of Padina Tetrastromatica and Gracilaria Tenuistipitata Seaweeds Collected From Bangladesh

Seaweeds are now recognized as a treasure of bioactive compounds. However, the seaweed of Bangladesh is still unexplored. So, this study was designed to explore the secondary metabolites and antioxidant activities of solvent extracts of Padina tetrastromatica and Gracilaria tenuistipitata. Phytochemical screening and Fourier transform infrared (FTIR) confirm the diverse type of bioactive compounds. Antioxidant activity of extracts were evaluated by 1, 1-diphenyl-2- picrylhydrazyl (DPPH), 2, 2-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), reducing power (RP), phosphomolybdenum and hydrogen peroxide assays. Here, methanolic extract of P. tetrastromatica showed the highest amount of total phenolic content (85.61 mg of GA/g), total flavonoid content (41.77 mg of quercetin/g), which showed as potent antioxidant properties confirmed by DPPH (77.07%), ABTS (77.65%), RP (53.24 mg AAE/g), phosphomolybdenum (31.58 mg AAE/g) and hydrogen peroxide (67.89%) assays followed by ethanol and water. This study concluded that bioactive compound and antioxidant activities are dose and solvent-dependent and seaweed type.

New records of seaweeds from southeastern coasts of Cox’s Bazar district, Bangladesh

Gracilaria tenuistipitata var. liui Zhang et Xia 1988 from sand-flat at Nuniachara, Cox’s Bazar, Ulva linza Lin. from west coast of Naf R. at Noapara, Teknaf and Fishary Ghat in River Bakkhali, at Cox’s Bazar, and Caulerpa fergusonii Murray from St. Martin’s Island (SMI), have been newly recorded and illustrated from Bangladesh. C. chemnitzschi (Esper) Weber-van Bosse var. irregulare Aziz & Alfasane var. nov. and C. sertularioides (S.G. Gmelin) M. Howe var. robusta Aziz & Alfasane var. nov. from SMI, Cox’s Bazar District, Bangladesh are new to science. Total number of marine algal taxa so far recorded from Bangladesh coasts is now 210. Bangladesh J. Plant Taxon. 27(2): 335-343, 2020 (December)

An Investigation on Zinc Biosorption with Agar Extraction Waste from Gracilaria tenuistipitata

This study determined the biosorption capacity of algal waste, obtained through agar extraction from Gracilaria tenuistipitata, a common red seaweed in the Philippines and potential biosorbent, on Zn2+ ions. Agar was extracted from the seaweed and characterized through Fourier-transform infrared spectroscopy (FT-IR). The algal waste was then subjected to a biosorption study involving various Zn2+ standards. Atomic absorption spectroscopy (AAS) and FT-IR were employed to evaluate sorption processes. Biosorption data was analyzed using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms which yielded values of 0.9680, 0.8103, and 0.5254, respectively. The Langmuir ( ), Freundlich ( ), and D-R ( ) constants garnered were 0.0231 L/mg, 0.9829 mg/g, and 2.159 10-6 mol2 J-2 respectively, qualifying the adsorption of Zn2+ ions onto the algal waste as a favorable and physical process. FT-IR spectra analysis suggests that carboxylic acid and amide groups are involved in biosorption, possibly an ion-exchange process taking place for the uptake of Zn2+ ions. It was concluded that G. tenuistipitata waste is a promising biosorbent for Zn2+ ions. Performing the biosorption procedure in triplicates and the inclusion of kinetic studies are recommended to improve and ensure the accuracy in determining biosorption capacity and optimization in future studies.