Extracts of Passiflora ligularis Juss. (granadilla) residues (peel, seed and mixed peel, seed) were initially evaluated for antimicrobial potential against Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens, Escherichia coli and Salmonella enteritidis. Notably, 80 acetone granadilla seed extract showed inhibitory activity against major bacteria (five) compared to the other extracts. Next, the extraction conditions of this extract were optimised, varying the solid/solvent ratio (0.5: 10-6.0: 10), incubation time (10-60 min) and temperature (30-60 degrees C), to obtain maximum antimicrobial activity, total phenolic content (TPC) and total flavonoid content (TFC). A central composite rotatable design (2(3) factorial arrangement with six axial points and three central points) was used. The temperature and solid/solvent ratio were most significant parameters to obtain extracts with antibacterial potential and significant bioactive compounds content (TPC and TFC). The response surfaces indicated that extracts obtained with increased solid/solvent molar ratio and temperature possess maximum inhibitory potential against most of the tested bacteria. However, extracts obtained with decreased molar ratio and increased temperature will have maximum TPC and TFC, respectively. Collectively, the data demonstrate that granadilla residue extracts have excellent potential as a source of natural antimicrobial and bioactive compounds, under optimised extraction conditions.
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