Applications of thin-layer chromatography in extraction and characterisation of ajoene from garlic bulbs

Novel and inexpensive methods of thin-layer chromatography (TLC) were employed for the extraction, characterisation and mechanism of quorum sensing inhibition by ajoene, a component from toluene garlic bulb (Allium sativum L.) extract (TGE). TLC profiling of TGE was carried out using ethyl acetate as solvent. Out of total spots extracted from TLC, four spots exhibited quorum sensing inhibitory (QSI) potential. Among those, spot 5 was identified as Z-ajoene by TLC and confirmed by NMR and MS. HPLC analysis indicated 97.7% purity for purified ajoene. TLC densitometric analysis quantified 221.08 μmol/g of ajoene in TGE and indicated that ajoene is stable at 4°C and at acidic pH. HPTLC profiling showed that ajoene exhibits QSI effect by inhibiting the production of both long-chain acyl homoserine lactones and Pseudomonas quinolone signal (PQS) by P. aeruginosa and also by inactivating PQS molecules.