Chemical Characterization and Antibiofilm Activities of Bulbs and Leaves of Two Aglione (Allium ampeloprasum var. holmense Asch. et Graebn.) Landraces Grown in Southern Italy

Abstract

The present study was carried out to determine some biochemical characteristics, in particular the total polyphenol content and the free radical scavenging activity, of the extracts recovered from bulbs and aerial parts (these last often considered as by-products) of two landraces of A. ampeloprasum var. holmense cultivated in Southern Italy. For the first time, the capacity of the extracts of these landraces to inhibit the formation of biofilm of different Gram-negative and Gram-positive bacteria and to affect the metabolism of the cells present within the bacterial biofilm was evaluated. All extracts exhibited an amount of total polyphenols not lower than 2.86 mg/g of dried product and revealed a noteworthy antioxidant activity, with EC50 values not exceeding 4.95 mg. In both cases, the aerial parts extracts were more effective than the bulb extracts, which also showed a minor amount of total polyphenols. The extracts inhibited mainly the adhesive capability of Pseudomonas aeruginosa and Staphylococcus aureus, by 95.78% and 85.01%, respectively. The extracts demonstrated to inhibit also the metabolism of the bacterial cells reaching levels up to 90%. Finally, as assessed by the assays performed on the 24-h preformed biofilms, all the extracts were also capable to cause a reduction in bacterial biomass and to affect their metabolism.

Comparison of the Mineral and Nutraceutical Profiles of Elephant Garlic (Allium ampeloprasum L.) Grown in Organic and Conventional Fields of Valdichiana, a Traditional Cultivation Area of Tuscany, Italy

“…A key feature of A. ampeloprasum is a reduced content of fibers and sulphur-containing compounds (alliin-related compounds) compared to common garlic [4], which makes this species preferred over garlic in cooking, having a similar but more delicate taste, and a higher digestibility. For this reason, A. ampeloprasum is also known as "kissing garlic" or "garlic for people who do not like garlic" [5]. Overall, elephant garlic is a leek-like plant, but producing cloves that are bigger and have a milder flavor than those of common garlic.…”

Polyphenols Content and In Vitro α-Glycosidase Activity of Different Italian Monofloral Honeys, and Their Effect on Selected Pathogenic and Probiotic Bacteria

“…The capacity of the honeys to affect the biofilm formation by the pathogenic bacteria was evaluated in flat-bottomed 96-well microtiter plates [ 29 ]. The overnight bacterial cultures were adjusted to 0.5 McFarland (1.5 × 10 7 cells/mL.…”

“…The capacity of the honeys to affect the bacterial adhesion was evaluated in flat-bottomed 96-well microtiter plates, modifying the method described by Caputo et al (2020) [ 29 ], with the addition of the two concentrations of honey, 5.71 μL/mL and 11.42 μL/mL, after 2 h of bacterial growth. The growth continued until 48 h. The successive steps of the experiment, including the calculation of the percent value of adhesion were performed as indicated in Section 2.2.3 .…”

“…The capacity of the honeys to affect the mature biofilm, considered after 24 h of bacterial growth was evaluated in flat-bottomed 96-well microtiter plates following, the same protocol described in Section 2.2.3 [ 29 ]. After 24 h of bacterial growth, planktonic cells were removed, and the two concentrations of the honeys, 5.71 μL/mL and 11.42 μL/mL of each sample and Luria-Bertani broth were added, to have a final volume of 250 μL/well.…”

“…The effect of two concentrations, 5.71 μL/mL and 11.42 μL/mL of the honeys (prepared as above described)—added at the beginning of the bacterial growth, after two hours of incubation and after 24 h of incubation—was also evaluated on the metabolic activity of the bacterial cells through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric method [ 29 , 30 ], using 96-well microtiter plates. The overnight bacterial cultures were adjusted to 0.5 McFarland and microtiter plates were prepared as described in the Section 2.2.3 .…”