| dc.description.abstract | From the ancient time herbs and spices have attended in traditional medicinal
treatments against minor disease such as cough, flu, etc. Due to their natural
origin, these plant materials are safe and can be exploited for many purposes. This
study aimed to evaluate the antimicrobial and antioxidant capacity of four Allium
species of Vietnam: purple onion, white onion, purple shallot and white shallot.
Under ethanolic extraction, the highest total phenolic and total flavonoid content
was detected in purple onion (22.66 ± 1.35 mg FAE/gDW and 11.00 ± 3.74
mgRE/gDW, respectively), which correlated to the strong antioxidant activity
(84.70% for 50 mg/ml extract concentration) measured by DPPH-radical
scavenging assay; white onion ranked second, neutralized 67.82% DPPH-radical;
while purple shallot and white shallot ranked third for three mentioned criteria. The
antimicrobial activities were tested against two gram-positive pathogenic bacteria:
S. aureus and B. cereus (VTCCB-1005); and two gram-negative pathogenic
bacteria: P. aeruginosa (ATCC-9027) and S. typhi - by agar well diffusion method
and measuring the minimum inhibitory concentration (MIC). Although not being a
prominent antioxidant in four test subjects, white shallot was appreciated for
expressing the best antimicrobial activity, followed by purple onion and white onion.
S. typhi resisted against all extracts while purple shallot showed no antimicrobial
activity against reference strains. The distinction in growth suppression between
gram negative and gram positive bacteria were not significant.
Key words:
Onion
Shallot
Antioxidant activity
Antimicrobial activity
Total phenolic compounds
Total flavonoid compounds | en_US |
