Antioxidant and Antimicrobial Properties of Stachys maritima via Quantum Dots and Molecular Docking

Abstract

Stachys maritima is a species of plant belonging to the Lamiaceae, commonly known as common sea lavender. The extraction of S. maritima involves drying the aerial parts, grinding them into powder, followed by extraction with methanol. ST-CQDs (S. maritima carbon quantum dots) were synthesized from S. maritima extract via pyrolysis. An optimal synthesis condition of 7 hours of pyrolysis was determined to yield ST-CQDs with high absorption in the visible-UV range. Characterization techniques such as UV-visible spectroscopy and TEM (Transmission Electron Microscopy) confirmed the spherical and homogeneous nature of the carbon quantum dots. S. maritima methanol extract exhibited strong antioxidant activity with a DPPH (2,2-Diphenyl-1-picrylhydrazyl) IC₅₀ value of 0.114±0.001 mg/mL. Similarly, ST-CQDs showed strong antioxidant properties with a DPPH IC₅₀ value of 0.69±0.03 mg/mL. Moreover, the methanol extract of S. maritima demonstrated antimicrobial activity against E. coli ATCC 25922 and S. aureus ATCC 25923, with effective MIC values of 25 mg/mL and 6.25 mg/mL, respectively. However, ST-CQDs did not show antimicrobial effects against the tested microorganisms (E. coli ATCC 25922, S. aureus ATCC 25923, K. pneumoniae ATCC 13883, and C. albicans ATCC 10231). Molecular docking simulations suggested that compounds derived from S. maritima (such as 9,12,15-octadecatrienoic acid and palmitic acid) could interact effectively with TNF-α (Tumor Necrosis Factor Alpha), indicating potential anti-inflammatory properties. This study highlights that the methanol extract of S. maritima possesses potent antioxidant and antimicrobial activities, and ST-CQDs exhibit similar antioxidant properties. However, ST-CQDs did not demonstrate antimicrobial activity against the tested pathogens. Molecular docking simulations also suggest potential anti-inflammatory properties of compounds derived from the plant.

Keywords: Antimicrobial activity Antioxidant Carbon quantum dots Molecular docking Stachys maritima.