Synthesis of Gold Nanoparticles (AuNPs) Using Ricinus communis Leaf Ethanol Extract, Their Characterization, and Biological Applications

The purpose of this study was to explore the collective biological properties of Ricinus communis ethanol leaf extract (RcExt) and extract-fabricated gold nanoparticles (RcExt-AuNPs). AuNPs were synthesized using RcExt. Fingerprint data of the biochemicals putatively found in RcExt were obtained using gas chromatography–mass spectrometry (GC-MS/MS) and high-performance liquid chromatography/ultraviolet-visible (HPLC/UV-VIS) analyses. RcExt-AuNPs were characterized by UV-Vis spectroscopy, scanning electron microscopy (SEM), and Fourier- transform infrared radiation (FTIR) spectroscopy. Cytotoxic activity on the Hela and HepG2 tumor cell lines was tested through cell viability, antimicrobial activity against bacterial and fungal pathogens through a well diffusion assay, hemolytic activity on red blood cells through absorbance reading, and stimulatory/inhibitory effects on splenic cells by cell viability. AuNPs of 200 nm size were synthesized. GC-MS/MS analysis revealed 12 peaks and HPLC/UV-VIS analysis resulted in 18, 13, and five peaks at the wavelengths of 220, 254, and 300 nm, respectively. Cytotoxicity screening revealed that RcExt had stimulatory effects (6.08%) on Hela cells and an inhibitory effect (−28.33%) on HepG2 cells, whereas RcExt-AuNPs showed inhibitory effects (−58.64% and −42.74%) on Hela and HepG2 cells, respectively. Antimicrobial activity of RcExt-AuNPs against tested pathogens was significantly higher (average diameters of inhibition zones were higher (ranging from 9.33 mm to 16.33 mm)) than those of RcExt (ranging from 6.00 mm to 7.33 mm). RcExt and RcExt-AuNPs showed 4.15% and 100% lytic effects, respectively. Inhibitory effects on splenic cells for RcExt-AuNPs were observed to be significantly higher (−30.56% to −72.62%) than those of RcExt (−41.55% to −62.25%) between concentrations of 25 to 200 µg/mL. RcExt-AuNPs were inhibitory against HepG2 and Hela cells, while RcExt inhibited HepG2 but stimulated Hela cells. RcExt-AuNPs showed comparatively more antimicrobial activity. RcExt was safe while RcExt-AuNPs harmful to red blood cells (RBCs). RcExt and RcExt-AuNPs showed inhibitory effects on splenic cells irrespective of dose.