Development of magnetic solid phase extraction platform for the purification of bioactive γ-glutamyl peptides from garlic (Allium sativum)

A magnetic solid phase extraction (MSPE) platform was developed as an alternative to industrial chromatography for purification of bioactive gamma-glutamyl peptides from crude garlic extract. Core-shell C18-functionalized Fe₃O₄–SiO₂ nanoparticles were prepared and characterized for use as magnetic adsorbents. Key MSPE variables, i.e. (1) garlic extract's pH, (2) eluent type, (3) adsorbent concentration, and (4) extraction time, were investigated to determine the optimal MSPE condition. The results showed that the purification favored weakly-acidic pH for both the garlic extract and eluent due to the higher solubility of the peptides and the impurities at acidic pH. At the optimal condition, nearly 80% of the impurities were removed, while the peptides present in the crude garlic extract were mostly retained in the final product. Mass spectrometry verified that the peptides' molecular structure remained intact after purification. The nanoparticle adsorbent remained effective after multiple cycles of MSPE and prolonged storage. The present work successfully established MSPE as a simple, cost-effective, and environmentally-friendly purification technique for bioactive peptides.