Antioxidant Activity of a Sicilian Almond Skin Extract Using In Vitro and In Vivo Models

Specific Antimicrobial Activities Revealed by Comparative Evaluation of Selected Gemmotherapy Extracts

Nowadays, unprecedented health challenges are urging novel solutions to address antimicrobial resistance as multidrug-resistant strains of bacteria, yeasts and moulds are emerging. Such microorganisms can cause food and feed spoilage, food poisoning and even more severe diseases, resulting in human death. In order to overcome this phenomenon, it is essential to identify novel antimicrobials that are naturally occurring, biologically effective and increasingly safe for human use. The development of gemmotherapy extracts (GTEs) using plant parts such as buds and young shoots has emerged as a novel approach to treat/prevent human conditions due to their associated antidiabetic, anti-inflammatory and/or antimicrobial properties that all require careful evaluations. Seven GTEs obtained from plant species like the olive (Olea europaea L.), almond (Prunus amygdalus L.), black mulberry (Morus nigra L.), walnut (Juglans regia L.), blackberry (Rubus fruticosus L.), blackcurrant (Ribes nigrum L.) and bilberry (Vaccinium myrtillus L.) were tested for their antimicrobial efficiency via agar diffusion and microbroth dilution methods. The antimicrobial activity was assessed for eight bacterial (Bacillus cereus, Staphylococcus aureus, Salmonella enterica subsp. enterica, Proteus vulgaris, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Listeria monocytogenes), five moulds (Aspergillus flavus, Aspergillus niger, Aspergillus ochraceus, Penicillium citrinum, Penicillium expansum) and one yeast strain (Saccharomyces cerevisiae). The agar diffusion method revealed the blackberry GTE as the most effective since it inhibited the growth of three bacterial, four moulds and one yeast species, having considered the total number of affected microorganism species. Next to the blackberry, the olive GTE appeared to be the second most efficient, suppressing five bacterial strains but no moulds or yeasts. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were then determined for each GTE and the microorganisms tested. Noticeably, the olive GTE appeared to feature the strongest bacteriostatic and bactericidal outcome, displaying specificity for S. aureus, E. faecalis and L. monocytogenes. The other GTEs, such as blueberry, walnut, black mulberry and almond (the list indicates relative strength), were more effective at suppressing microbial growth than inducing microbial death. However, some species specificities were also evident, while the blackcurrant GTE had no significant antimicrobial activity. Having seen the antimicrobial properties of the analysed GTEs, especially the olive and black mulberry GTEs, these could be envisioned as potential antimicrobials that might enhance antibiotic therapies efficiency, while the blackberry GTE would act as an antifungal agent. Some of the GTE mixtures analysed have shown interesting antimicrobial synergies, and all the antimicrobial effects observed argue for extending these studies to include pathological microorganisms.

A Green Bioactive By-Product Almond Skin Functional Extract for Developing Nutraceutical Formulations with Potential Antimetabolic Activity

(1) Background: almond peels are rich in polyphenols such as catechin and epicatechin, which are important anti-free-radical agents, anti-inflammatory compounds, and capable of breaking down cholesterol plaques. This work aims to evaluate the biological and technological activity of a "green" dry aqueous extract from Sicilian almond peels, a waste product of the food industry, and to develop healthy nutraceuticals with natural ingredients. Eudraguard® Natural is a natural coating polymer chosen to develop atomized formulations that improve the technological properties of the extract. (2) Methods: the antioxidant and free radical scavenger activity of the extract was rated using different methods (DPPH assay, ABTS, ORAC, NO). The metalloproteinases of the extracts (MMP-2 and MMP-9), the enhanced inhibition of the final glycation products, and the effects of the compounds on cell viability were also tested. All pure materials and formulations were characterized using UV, HPLC, FTIR, DSC, and SEM methods. (3) Results: almond peel extract showed appreciable antioxidant and free radical activity with a stronger NO inhibition effect, strong activity on MMP-2, and good antiglycative effects. In light of this, a food supplement with added health value was formulated. Eudraguard® Natural acted as a swelling substrate by improving extract solubility and dissolution/release (4) Conclusions: almond peel extract has significant antioxidant activity and MMP/AGE inhibition effects, resulting in an optimal candidate to formulate safe microsystems with potential antimetabolic activity. Eudraguard® Natural is capable of obtaining spray-dried microsystems with an improvement in the extract's biological and technological characteristics. It also protects the dry extract from degradation and oxidation, prolonging the shelf life of the final product.