Evaluation of conventional and ultrasonic techniques in Plant byproduct extraction as antimicrobial agents for food pathogens and spoilage microorganisms .

Bioactive chemicals are extracted from a variety of plant by-product sources, including leaves,
seeds, and peels, to create plant by-product extracts. These sources are rich in bioactive compounds such
as total phenolics, flavonoids, and antioxidant activity. These compounds have antioxidant and
antimicrobial effects; therefore, they are widely used as natural preservatives. The antimicrobial activity
of organic extracts of some plant by-products was determined by the disk diffusion method. The results
revealed that the solvent (70%, 50% ethanol, and water extraction) and extraction methods (conventional
and ultrasound extraction) significantly affected the amounts of photochemical compounds, total
phenolics, total flavonoids, and antioxidant activity. Compared with the conventional method, ultrasound
extraction significantly affected the antimicrobial activity and was more effective against Fusarium
solani, Penicillium digitatum, E. coli, and Erwinia carotovora in most of the extracts. The aqueous extract
of pomegranate peels by ultrasound extraction showed the greatest inhibitory effect on the diameter of
Escherichia coli (34.67±0.58 mm) and Erwinia cartova (30.67±0.58 mm) as well as fungi (, Penicillium
digitatum., 32.00±1.0 mm). However, the ultrasound ethanolic extract of 50% Sidr leaves was highly
effective against Fusarium solani as it was )36.00±1.7 mm( . The activity of bioactive compounds was
increased by ultrasonic extraction. The total flavonoid amount increased to 1734.00 ± 1.41 mg/100 mL.
On the other hand, the antioxidant activity of the aqueous pomegranate peel extract rose from 72.00% to
86%. This study demonstrated that the extraction method and solvent used enhanced the antibacterial
activity, and that pomegranate peels exhibited a higher inhibition rate than the chemical preservatives
used in the experiment.