Comparative study of proteasome inhibitory, synergistic antibacterial, synergistic anticandidal, and antioxidant activities of gold nanoparticles biosynthesized using fruit waste materials

Figures & data

Figure 1 Fruit peels of oriental melon (Cucumis melo) (A) and peach (Prunus persica) (B) used for the synthesis of AuNPs.

Abbreviation: AuNPs, gold nanoparticles.

Figure 2 UV–visible spectroscopy and change in color of the reaction mixture at different time intervals of the synthesized OMP-AuNPs and PE-AuNPs.

Notes: (A) OMP-AuNPs; (B) PE-AuNPs.

Abbreviations: AuNPs, gold nanoparticles; OMP, oriental melon peel; PE, peach extract; UV, ultraviolet.

Figure 3 SEM image of synthesized OMP-AuNPs and PE-AuNPs.

Notes: (A) OMP-AuNPs; (B) PE-AuNPs.

Abbreviations: AuNPs, gold nanoparticles; OMP, oriental melon peel; PE, peach extract; SEM, scanning electron microscopy.

Figure 4 EDX analysis of synthesized OMP-AuNPs and PE-AuNPs.

Notes: OMP-AuNPs (A–C) and PE-AuNPs (D–F).

Abbreviations: AuNPs, gold nanoparticles; EDX, energy dispersive X-ray; OMP, oriental melon peel; PE, peach extract.

Figure 5 XRD spectra of synthesized OMP-AuNPs and PE-AuNPs.

Notes: (A) OMP-AuNPs; (B) PE-AuNPs.

Abbreviations: AuNPs, gold nanoparticles; OMP, oriental melon peel; PE, peach extract; XRD, X-ray powder diffraction.

Figure 6 FT-IR analysis of synthesized OMP-AuNPs and PE-AuNPs.

Notes: (A) OMP-AuNPs; (B) PE-AuNPs.

Abbreviations: AuNPs, gold nanoparticles; FT-IR, Fourier transform infrared spectroscopy; OMP, oriental melon peel; PE, peach extract.

Figure 7 TG/DTG analysis of synthesized OMP-AuNPs and PE-AuNPs.

Notes: (A) OMP-AuNPs; (B) PE-AuNPs.

Abbreviations: AuNPs, gold nanoparticles; Deriv., derivative; DTG, derivative thermogravimetric; OMP, oriental melon peel; PE, peach extract; TG, thermogravimetric.

Table 1 Comparative synergistic antibacterial activity of OMP-AuNPs (25 μg) and PE-AuNPs (25 μg) with standard antibiotics, kanamycin (5 μg) or rifampicin (5 μg), against foodborne pathogenic bacteria

Bacteria	Antibacterial activity (control samples)							Synergistic antibacterial activity
								AuNPs with kanamycin		AuNPs with rifampicin
	OMP extract	PE	OMP-AuNPs	PE-AuNPs	Kanamycin	Rifampicin	DMSO	OMP-AuNPs + kanamycin	PE-AuNPs + kanamycin	OMP-AuNPs + rifampicin	PE-AuNPs + rifampicin
B. cereus ATCC 13061	0	0	0	0	0	0	0	11.42±0.74^c,*	10.47±0.50^c,d	10.04±0.19^c	9.52±0.14^d
E. coli ATCC 43890	0	0	0	0	0	0	0	11.03±0.52^c	20.45±0.51^a	9.78±0.38^c,d	10.01±0.21^c,d
L. monocytogenes ATCC 19115	0	0	0	0	0	0	0	9.38±0.27^d	13.48±0.56^b	0.00±0.00^e	0.00±0.00^e
S. aureus ATCC 49444	0	0	0	0	0	0	0	13.26±0.90^b	13.98±0.07^b	22.39±0.53^b	25.23±0.90^a
S. Typhimurium ATCC 43174	0	0	0	0	0	0	0	11.23±0.28^c	13.07±0.21^b	0.00±0.00^e	0.00±0.00^e

Notes:

* Data are expressed as the mean zone of inhibition in millimeter ± SD. Values with different superscript letters in the columns with kanamycin and in the columns of AuNPs with rifampicin are significantly different at P<0.05.

Abbreviations: AuNPs, gold nanoparticles; ATCC, American Type Culture Collection; B. cereus, Bacillus cereus; DMSO, dimethyl sulphoxide; E. coli, Escherichia coli; L. monocytogenes, Listeria monocytogenes; OMP, oriental melon peel; PE, peach extract; S. typhimurium, Salmonella typhimurium; S. aureus, Staphylococcus aureus.

Table 2 Comparative synergistic anticandidal activities of OMP-AuNPs (50 μg) and PE-AuNPs (50 μg) mixed with amphotericin B (5 μg), a standard antifungal agent against pathogenic Candida species

Candida species	Anticandidal activity (control samples)						Synergistic anticandidal activity
	OMP extract	PE	Amphotericin B	DMSO	OMP-AuNPs	PE-AuNPs	OMP-AuNPs + amphotericin B	PE-AuNPs + amphotericin B
Candida albicans KACC 30003	0	0	0	0	0	0	10.96±0.93^e,*	10.97±0.41^d,e
Candida albicans KACC 30062	0	0	0	0	0	0	14.45±0.53^b	15.47±0.27^a
Candida glabrata KBNO6P00368	0	0	0	0	0	0	10.66±0.47^d,e	11.09±0.66^d
Candida geochares KACC 30061	0	0	0	0	0	0	13.27±0.28^c	14.25±0.22^b
Candida saitoana KACC 41238	0	0	0	0	0	0	10.09±0.30^e	11.08±0.28^d,e

Notes:

* Data are expressed as the mean zone of inhibition in millimeter ± SD. Values with different superscript letters are significantly different at P<0.05.

Abbreviations: AuNPs, gold nanoparticles; DMSO, dimethyl sulphoxide; OMP, oriental melon peel; PE, peach extract; SD, standard deviation.

Figure 8 Antioxidant potential of synthesized OMP-AuNPs and PE-AuNPs.

Notes: (A) DPPH free radical scavenging potential; (B) nitric oxide scavenging potential; (C) ABTS radical scavenging potential; and (D) reducing power potential. Values with different superscript letters are significantly different at P<0.05.

Abbreviations: ABTS, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid); AuNPs, gold nanoparticles; BHT, butylated hydroxyl toluene; DPPH, 1,1-diphenyl-2-picrylhydraxyl; OMP, oriental melon peel; PE, peach extract.

Figure 9 Proteasome inhibitory potential of both OMP-AuNPs and PE-AuNPs and standard reference compound, Epox.

Notes: 100 μg/mL (OMP-AuNP_100, PE-AuNP_100); 10 μg/mL (OMP-AuNP_10, PE-AuNP_10); 1 μg/mL (OMP-AuNP_1, PE-AuNP_1) and 5.56 μg/mL (Epox_10); 2.78 μg/mL (Epox_5) and 0.56 μg/mL (Epox_1).

Abbreviations: AuNPs, gold nanoparticles; FU, fluorescence units; Epox, epoxomicin; OMP, oriental melon peel; PE, peach extract.