Phenolic profile of Cynara scolymus L. and Silybum marianum(L.) Gaertn and related antimicrobial properties
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resumo
Cynara scolymus L. (artichoke) and Silybum marianum (L.)
Gaertn (milk thistle), belonging to the Asteraceae family, are
medicinal plants with well-reported antioxidant and
hepatoprotective effects. Widely consumed as infusions, these
plants can also be found in several formulations to allow an
easier consumption. The bioactivity of infusions, pills, and
syrups based on artichoke and milk thistle was previously
reported by our research group [1,2] and among the various
phytochemicals present in these dietary supplements, phenolic
compounds are pointed out as the most responsible for their
beneficial properties.
With the aim of studying the antimicrobial activity and possible
relation with the phenolic composition, two different
formulations of each plant were assessed (pills and syrups).
The phenolic profiles were obtained by HPLC-DAD-ESI/MS,
and the antimicrobial activity was performed with clinical
isolates from hospitalized patients, namely Escherichia coli,
Escherichia coli spectrum extended producer of β-lactamases
(ESBL), Proteus mirabilis, Pseudomonas aeruginosa, and
methicillin-resistant Staphylococcus aureus (MRSA).
Cynara scolymus L. (artichoke) and Silybum marianum (L.) Gaertn (milk thistle), belonging to the
Asteraceae family, are medicinal plants vo.ith well-reported antioxidant and hepatoprotective effects.
Widely consumed as infusions, these plants can also be found in several formulations to allow an easier
consumption. The bioactivity of infusions, pills, and syrups based on artichoke and milk thistle was
previously reported by our research group [1 ,2] and among the various phytochemicals present in these
dietary supplements, phenolic compounds are pointed out as the most responsible for their beneficial
properties. With the aim of studying the antimicrobial activity and possible relation vo.ith the phenolic
composition, two different formulations of each plant were assessed (pills and syrups). The phenolic
profiles were obtained by HPLC-DAD-ESIIMS, and the antimicrobial activity was performed with clinical
isolates from hospitalized patients, namely Escherichia coli, Escherichia coli spectrum extended producer
of P-lactarnases (ESBL), Proteus mirabilis, Pseudomonas aeruginosa, and methicillin-resistant
Staphylococcus aureus (MRSA).
Vanillic acid (5.58 J.tg/g) and luteolin-7-0-glucoside (2.2 J.tg/g) were the most abundant compounds in
artichoke syrup, that did not reveal antimicrobial activity against the studied strains, which could be due to
their low concentrations. On the other hand, artichoke pills presented a prevalence of 5-0-caffeoylquinic
(28.2 J.tg/g), 1,3-dicaffeoylquinic (24 J.tg/g), and 4-0-Caffeoylquinic acids (13.3 J.tg/g); revealing the
capacity to inhibit MRSA vo.ith a MIC value of 1.9 mg!g.
Regarding milk thistle, isorhamnetin-0-deoxyhexoside-0-hexoside, isorhamnetin-3-0-rutinoside, and
isorhamnetin-0-deoxyhexoside-0-dihexoside were the major compounds detected in the syrup, in
concentrations of 7.26, 5. 75, and 3.64 J.tg/g, respectively. This formulation proved to be able to inhibit the
growth of E. coli, ESBL, MRSA and P. aeruginosa, with MIC values ranging from 0.2 to 1.3 mg!mL.
Hydroxylated silibinin (1.565 J.!g/g) was the major flavonoid found in the pills, that revealed antimicrobial
activity against ESBL, with a MIC value of 15 mg!mL, but did not inhibit the growth of the remaining
bacteria None of the studied samples was able to inhibit P. mirabilis at the studied concentrations (1000
and 26.4 mg!mL for the syrups of artichoke and milk thistle, respectively; 150 mg/mL for both pills).
Overall, the studied syrups and pills of artichoke and milk thistle revealed to be a good source of phenolic
compounds, with some of these formulations revealing antimicrobial activity.
