The development of antibacterial compounds using natural products, particularly nano-sized antibacterial products, has been intensively investigated in recent years. This study was conducted to compare the antibacterial activity of nanocurcumin with bulk curcumin against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. Curcumin was extracted from turmeric rhizome using the Soxhlet extraction with ethanol. A physicochemical fabrication method was used to synthesize nanocurcumin from extracted curcumin. The particle size of nanocurcumin was 87 ± 8 nm. The 1H NMR spectrum of nanocurcumin show that all the peaks are well separated and can be interpreted to those of curcumin. According to the in vitro antibacterial assay, nanocurcumin shows better antibacterial activity against both Gram-positive and Gram-negative bacteria than bulk curcumin, with increased inhibition zones of 29.91 ± 0.53 mm (S. aureus) and 24.58 ± 1.12 mm (E. coli) when compared to 24.82 ± 0.54 mm (S. aureus) and 19.70 ± 1.18 mm (E. coli) of the latter. Subsequently, antibacterial creams were formulated, and the inhibition zones of nanocurcumin cream were larger than that of curcumin cream for both S. aureus and E. coli, exhibiting its superior antibacterial activity. Different storage periods of up to 1 month did not affect the inhibition zones significantly (p < 0.05), where nanocurcumin cream maintained its better antibacterial quality over bulk curcumin cream. There is no significant cytotoxicity in either of these formulations.

Highlights• ICI based immunotherapy is a novel approach in cancer immunotherapy.• ICI therapy mainly targets the immune checkpoints, namely PD-1 and CTLA-4.• Gut microbiota affects the ICI therapy by modulating both PD-1 and CTLA-4.• Different gut bacteria have shown varying responses with ICI therapy.• Individual variation of gut microbiota challenges its application in ICI therapy.