BACKGROUND: The viral main protease (Mpro) of SARS-CoV-2 has been recently proposed as a key target to inhibit virus replication in the host. Therefore, molecules that can bind the catalytic site of Mpro could be considered as potential drug candidates in the treatment of SARS-CoV-2 infections. Here we proposed the application of a state-of-the-art analytical platform which combines metabolomics and protein structure analysis to fish-out potential active compounds deriving from a natural matrix, i.e., a blueberry extract.
METHODS: The experiments focus on finding MS covalent inhibitors of Mpro that contain in their structure a catechol/pyrogallol moiety capable of binding to the nucleophilic amino acids of the enzyme\'s catalytic site.
RESULTS: Among the potential candidates identified, the delphinidin-3-glucoside showed the most promising results. Its antiviral activity has been confirmed in vitro on Vero E6 cells infected with SARS-CoV-2, showing a dose-dependent inhibitory effect almost comparable to the known Mpro inhibitor baicalin. The interaction of delphinidin-3-glucoside with the Mpro pocket observed was also evaluated by computational studies.
CONCLUSIONS: The HRMS analytical platform described proved to be effective in identifying compounds that covalently bind Mpro and are active in the inhibition of SARS-CoV-2 replication, such as delphinidin-3-glucoside.

Anthocyanin pigments, which the peel of eggplant is rich in, contribute to food quality because of their function in color, appearance, and nutritional advantages. For the first time, this study aimed to optimize the composition of the extracting solvent as three factors: factor A (ratio of ethanol to methanol 0-100% v/v), factor B (ratio of water to alcohol 0-100% v/v), and factor C (citric acid in the final solvent 0-1% w/v) using response surface methodology (RSM), central composite design (CCD) with α 2, and two repeats in axial and factorial points and four central points, for maximum total phenolic content, total anthocyanin content, extraction yield, antioxidant activity in terms of DPPH radical scavenging activity and ferric reducing antioxidant power (FRAP) assay of the eggplant peel dry extract assisted by ultrasound (200 watts power, frequency of 28 kHz) in 60 °C for 45 min has been investigated. The best optimal formulas determined using RSM for the final solvent comprised optimal formula 1 (i.e., ethanol-to-methanol ratio 59% and water-to-alcohol ratio 0%, and citric acid in final solvent 0.47%), and optimal formula 2 (i.e., ethanol-to-methanol ratio 67% and water-to-alcohol ratio 0%, and citric acid in final solvent 0.56%). In general, an alcoholic-acidic extract of eggplant peel made with an ethanol-methanol solvent including citric acid can be used in the food industry as a natural source of antioxidants and pigment.

Anthocyanins are the most important polyphenolic substances contained in blackcurrant fruits. They are responsible for the various health benefits caused, in particular, by their high antioxidant activity. Anthocyanins derived from anthocyanidins cyanidin and delphinidin are typical for blackcurrant fruits, especially their rutinoside and glucoside forms. These four anthocyanins usually represent about 97-98% of total anthocyanins in blackcurrant fruits. In this study, we developed and validated a new HPLC-DAD method for rapid anthocyanin separation and determination in fifteen perspective blackcurrant cultivars (\'Ruben\', \'Ben Lomond\', \'Ben Conan\', \'Ceres\', \'Moravia\', \'Ometa\', \'Lota\', \'Fokus\', \'Tenah\', \'Sejanec\', \'Consort\', \'Triton\', \'Ben Hope\', \'Ben Gairn\', and one gooseberry hybrid \'Josta\'). Eight of them were monitored throughout the three-year experiment. The most represented anthocyanins in all monitored blackcurrant cultivars were delphinidin-3-rutinoside (36.7-63.6%), cyanidin-3-rutinoside (26.4-40.6%), delphinidin-3-glucoside (6.1-17.9%), and cyanidin-3-glucoside (1.3-9.9%). The individual anthocyanin proportion (%) in each cultivar was specific, and a similar profile was verified in a three-year period for eight available cultivars. Total anthocyanin content expressed as a sum of four major anthocyanins present in blackcurrants was compared with values expressed as the equivalent of cyanidin-3-glucoside, as many authors do. We revealed an underestimation of about 20% with the latter method. Cultivars with the highest average total anthocyanin content were \'Ben Gairn\' (294.38 mg/100 g), \'Ceres\' (281.31 mg/100 g), and \'Ometa\' (269.09 mg/100 g).

METHODS: Oxidized LDL (oxLDL) induced vascular endothelial cell injury is a key event in the pathogenesis of atherosclerosis (AS). In our previous studies, we showed that delphinidin-3-glucoside (Dp), a natural anthocyanin, attenuated oxLDL-induced injury in human umbilical vein endothelial cells (HUVECs), indicating its potential role in preventing AS. However, the involved mechanism is not fully understood.
RESULTS: Via methyl thiazolyl tetrazolium and flow cytometry assay, we found that Dp-attenuated oxLDL-induced cell viability decrease and apoptosis in HUVECs. Depending on confocal microscopy, transmission electron microscopy, and Western blot assay, we found that Dp-induced autophagy in HUVECs, whereas suppression of autophagy significantly abolished the protective role of Dp against oxLDL-induced endothelial cell injury. Furthermore, Dp upregulated sirtuin 1 (SIRT1) expression and SIRT1 knockdown notably suppressed Dp-induced autophagy in HUVECs. Dp also increased the expression of phosphorylated adenosine monophosphate-activated protein kinase, while adenosine monophosphate-activated protein kinase (AMPK) knockdown remarkably abolished Dp-induced SIRT1 expression and subsequent autophagy.
CONCLUSIONS: Our data suggested that Dp protected HUVECs against oxLDL-induced injury by inducing autophagy via the adenosine monophosphate-activated protein kinase/SIRT1 signaling pathway. This new finding might shed light to the prevention and therapy of AS.

BACKGROUND: Maqui (Aristotelia chilensis) is a Chilean species which produces small berries that are collected from the wild. Anthocyanins, because of their health benefits, are the major focus of interest in maqui fruit. For this study, we examined anthocyanin and phenolic content of maqui fruits from individuals that belonged to four geographical areas in Chile, and used DNA marker analysis to examine the genetic variability of maqui populations that had distinctly different fruit anthocyanin content.
RESULTS: Twelve primers generated a total of 145 polymorphic inter simple sequence repeat-polymerase chain reaction (ISSR-PCR) bands. ISSR-PCR showed different banding patterns for the individuals evaluated, confirming that maqui populations belonged to different genotypes. Maqui fruit from four different geographical regions during two consecutive growing seasons showed high total anthocyanin (6.6-15.0 g cy-3-glu kg⁻¹ fresh weight (FW)) and phenolic (10.7-20.5 g GAE kg⁻¹ FW) contents and different anthocyanin profiles.
CONCLUSIONS: Three maqui genotypes exhibited significantly higher anthocyanin content than the others, as measured by pH differential method and high-performance liquid chromatography-mass spectrometry. Significant genetic diversity was noted within each ecological population. ISSR-PCR analysis provided a fingerprinting approach applicable for differentiation of maqui genotypes.

Anthocyanins exhibit colour variation over wide pH range but the colour stability is relatively low at the physiological pH. To improve the stability of anthocyanins in neutral to weakly acidic pH region, effects of metal cations and polysaccharides on the colour stability of cyanidin-3-glucoside (C3G) were examined by ultraviolet-visible and resonance Raman spectroscopies. C3G was thermally stabilized by the addition of Fe(3+) but formed aggregation. However, further addition of anionic polysaccharides enhanced the thermal stability of C3G without aggregation. Similar stabilisation was confirmed for delphinidin-3-glucoside (D3G) but not for pelargonidin-3-glucoside. The stability of anthocyanins considerably varied depending on pHs and kinds of metal cations, polysaccharides and buffer molecules. The characteristic resonance Raman bands of C3G-Fe(3+) and D3G-Fe(3+) complexes were significantly affected by the addition of alginate, (18)O/(16)O-isotope substitution, and Fe(2+)/Fe(3+)-replacement. These results suggest that alginate associates with C3G through Fe(3+) to form a stable complex, which enhances the thermal stability of C3G.