Comparative study of chemical composition, antioxidant and anticancer activities of both Turbinaria decurrens Bory methanol extract and its biosynthesized gold nanoparticles

Turbinaria decurrens Bory (T. decurrens), an Egyptian marine brown macroalga scattered along the coastline of the red sea, is used in some countries as food and medicine containing a diverse group of phytochemicals with unique bioactivities. Biosynthesis of gold nanoparticles (AuNPs) has also received a lot of attention as an alternative to physical and chemical methods. Thence, the primary goal of this work is to develop a green synthesis of AuNPs using hydromethanolic extract (HME) of T. decurrens. UV-visible spectra, Fourier transform infrared (FTIR) spectroscopy, XRD, and TEM analyses were used to investigate the size, shape, crystal structure, and agglomeration of biogenic AuNPs. AuNPs were virtually spherical and had a medium size ranges between 10.07 and 19.72 nm. The presence of functional groups of algal extract compounds adsorbed on the surface of AuNPs was confirmed using FTIR spectroscopy. HME was assayed for polyphenols (28.86 +/- 0.57 mg gallic acid equivalent/g extract), flavonoids (11.63 +/- 0.17 mg quercetin equivalent/g extract), total protein (35.05 +/- 0.45 mg/g extract), and soluble sugars (15.45 +/- 0.26 mg/g extract). Also, the HPLC analysis was used to analyze the phenolic profile of HME. Using the MTT assay against four cell lines of human cancer, the efficacy of both HME and biogenic AuNPs as cytotoxic agents was investigated and compared to both normal WI-38 cell lines and Doxorubicin as a standard drug. Results of the acridine orange/ethidium bromide (AO/EB) dual staining method, DNA fragmentation, and upgrade of the caspase activity confirmed the apoptotic mechanisms for cytotoxicity. In the case of HME, there was a discriminative inhibition of cancer cell growth of HEPG-2, whereas AuNPs had strong activity against three cancer cell lines and moderate activity against A549. Besides, HME and AuNPs were tested for antioxidant activity using DPPH and ABTS assays in comparison to Trolox, a standard drug, and the results revealed that both HME and AuNPs have effective antioxidant activity in a dose-based way. Our findings confirm the antioxidant and anticancer activities of HME and its AuNPs, as well as their potential as a therapeutic candidate in the treatment of oxidative stress diseases, particularly cancer.