2.5. Chemical characterization
Chemical characterization of pure active compound was performed through
UV–vis spectra, IR, GC–MS and NMR analyses. UV-analysis was carried out using a
Shimadzu UV–vis scanning spectrophotometer (Model No. UV-2101 PC). Scanning
was performed in a range between 200 and 700 nm wavelength. For IR analysis, the
sample was kept in vacuum desiccators over KOH pellets for 48 h, followed by IRspectral analysis with 1 mg sample in a FTIR (FT/IR-420 Jasco, USA). GC–MS analysis
was carried out using Shimadzu QP5000 spectrometer fitted with a Supelcowax
10 capillary column, having 0.32 mm ID, 30 m length, and 30 m film thickness. The
product obtained was compared to the molecules reported in the literature and NIST
(National Institute of Science and Technology, USA) library that was installed for
reference. NMR spectra were recorded in CDCl3 at room temperature using Bruker
WM 500 spectrometer [500 MHz ( 1 H NMR) and 125 MHz ( 13 C NMR)]. Chemical shifts
were given in ı-scale and were referenced to the solvent and to the TMS as internal
standard.
2.6. Antibacterial plate assay
Antibacterial activities of red pigments were examined by solid media bioassay test. Assay plates were prepared using Muller-Hinton agar (25 mL) poured in
90 mm × 15 mm Petri plates. The agar surface of the Petri plates was seeded with
0.1 mL of saline suspension of a 24-h grown test bacteria. A paper disc impregnated
with the sample compound was placed in the centre of the seeded agar plates and
incubated at 37 ◦C. Size of inhibition zones around paper discs was measured after
24 h of incubation. Data presented in Table 1 were the mean value of three replicates
in each case with standard deviation.