Phenolic profile of Cynara scolymus L. and Silybum marianum(L.) Gaertn and related antimicrobial properties

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.

Effects of gamma and electron-beam irradiation on the individual phenolics of Viola tricolor L. edible flowers.

Edible flowers are being used in culinary preparations to improve the sensorial and nutritional qualities of food, besides improving human health due to the profusion in bioactive compounds [1]. Nevertheless, edible flowers are highly perishable and must be free of insects, which is difficult because they are usually cultivated without using pesticides [2]. Food irradiation is an economically viable technology to extend shelf life of foods, improving their hygiene and quality, while disinfesting insects [3]. The efficiency and safety of radiation processing (using Co-60 or electronaccelerators) have been approved by legal authorities (FDA, USDA, WHO, FAO), as also by the scientific community, based on extensive research [4]. Viola tricolor L. (heartseases), from Violaceae family, is one of the most popular edible flowers. Apart from being used as food, it has also been applied for its medicinal properties, mainly due to their biological activity and phenolic composition [5]. Herein, the phenolic compounds were analyzed by HPLC-DAD-ESI/MS and linear discriminant analysis (LDA) was performed to compare the results from flowers submitted to different irradiation doses and technologies (Co-60 and electron-beam). Quercetin-3-O-(6-O-rhamnosylglucoside)-7-O-rhamnoside (Figure 1) was the most abundant compound, followed by quercetin-3-O-rutinoside and acetyl-quercetin-3-O (6-O-rhamnosylglucoside)-7-O-rhamnoside. In general, irradiated samples (mostly with 1 kGy) showed the highest phenolic compounds content. The LDA outcomes indicated that differences among phenolic compounds effectively discriminate the assayed doses and technologies, defining which variables contributed mostly to that separation. This information might be useful to define which dose and/or technology optimizes the content in a specific phenolic compound. Overall, irradiation did not negatively affect the levels of phenolic compounds, providing the possibility of its application to expand the shelf life of V. tricolor and highlighting new commercial solutions for this functional food.

A comparison of the bioactivity and phytochemical profile of three different cultivars of globe amaranth: red, white, and pink

The phytochemical profiles and bioactivities of red, white and pink globe amaranth (Gomphrena haageana K., Gomphrena globosa var. albiflora and Gomphrena sp., respectively), much less studied than the purple species (G. globosa L.), were compared. The chemical characterization of the samples included the analysis of macronutrients and individual profiles of sugars, organic acids, fatty acids, tocopherols, and phenolic compounds. Their bioactivity was evaluated by determining the antioxidant and anti-inflammatory activities; the absence of cytotoxicity was also determined. Red and pink samples showed the highest sugar content. Otherwise, the white sample gave the highest level of organic acids, and together with the pink one showed the highest tocopherol and PUFA levels. Quercetin-3-O-rutinoside was the major flavonol in white and pink samples, whereas a tetrahydroxy-methylenedioxyflavone was the major compound in the red variety, which revealed a different phenolic profile. The pink globe amaranth hydromethanolic extract revealed the highest antioxidant activity, followed by those of red and white samples. The anti-inflammatory activity was more relevant in red and pink varieties. None of the samples presented toxicity in liver cells. Overall, these samples can be used in bioactive formulations against inflammatory processes and in free radical production.