Zinc ascorbate has superoxide dismutase-like activity and in vitro antimicrobial activity against Staphylococcus aureus and Escherichia coli

Figures & data

Figure 1 Superoxide dismutase (SOD)-like activity of ascorbic acid derivatives and zinc. (A) Ascorbic acid derivatives and zinc (0.1%) and (B) zinc ascorbate (AZn) (0.1%–3%) in 20 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (pH 7.2) were subjected to the measurement of SOD-like activity (%), as described in the text. Data are indicated as mean ± standard deviation of triplicate assays.

Notes: ***Significantly different from ascorbic acid (AA), magnesium ascorbyl phosphate (APMg), sodium ascorbyl phosphate (AP), and zinc (Zn) (P < 0.001, respectively).

Table 1 Superoxide dismutase (SOD)-like activity of 25 μM ascorbic acid derivatives and zinc

Drug	SOD-like activity (%)
Ascorbic acid	18.4 ± 1.7
Sodium ascorbyl phosphate	ND
Magnesium ascorbyl phosphate	1.4 ± 0.6
Zinc	9.7 ± 0.6
Zinc ascorbate	26.7 ± 0.1

Notes: Ascorbic acid derivatives and zinc (25 μM) in 20 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (pH 7.2) were subjected to measurement of SOD-like activity (%), as described in the text. Data are indicated as mean ± standard deviation of triplicate assays.

Abbreviation: ND, not detected.

Table 2 Susceptibility of Staphylococcus aureus JCM 2874 and Escherichia coli JCM 5491 to zinc ascorbate

Bacterial species	MIC
S. aureus	640
E. coli	1280

Abbreviation: MIC, minimum inhibitory concentration (μg/mL).

Table 3 Combined effects of zinc ascorbate and antimicrobial agents on the twelve clinical strains each of Staphylococcus aureus and Escherichia coli

Drug combination	S. aureus		E. coli
	FIC range (average)	Interaction	FIC range (average)	Interaction
Zinc ascorbate + clindamycin	0.50–1 (0.79)	Additive	2 (2)	Indifference
Zinc ascorbate + erythromycin	0.75–1 (0.90)	Additive	2 (2)	Indifference
Zinc ascorbate + imipenem	0.28–0.75 (0.59)	Additive	0.38–0.75 (0.64)	Additive
Zinc ascorbate + minocycline	2 (2)	Indifference	2 (2)	Indifference
Zinc ascorbate + levofloxacin	2 (2)	Indifference	2 (2)	Indifference

Notes: The interaction was defined as synergistic if FIC index was less than 0.5; it was defined as additive if FIC index was between 0.5 and 1.0; it was defined as indifferent if FIC index was between 1.0 and 2.0; and it was defined as antagonistic if FIC index was >2.

Abbreviation: FIC, fractional inhibitory concentration.