*Participation of Platelets in Atherothrombosis*

Platelets represent the bridge between an inflammatory process and thrombosis, a fundamental process for the development of atherothrombosis and complication of atherosclerotic plaque [39]. Plaque rupture leads to the formation of a thrombus rich in platelets, a process characteristic of arterial thrombosis (Figure 2). During the atherothrombotic process, platelets participate in both the initial and final stages [40]. In the initial phase, platelets adhere to the CVRF-damaged endothelium, secreting and exposing molecules that amplify the inflammatory process [35,40]. In the final stage, after the plaque ruptures, the

platelets adhere at endothelium formatting to aggregates and thus contribute significantly to thrombus formation [41].

It has been observed that some bioactive compounds in fruits and vegetables, polyphenols and flavonoids, when consumed regularly may inhibit platelet activation and therefore reduce the risk of CVD. The importance of natural antioxidants to provide cardiovascular protection has been highlighted before [3,42,43], as well as the reports about the antithrombotic activity of fruits and vegetables [44,45]. In the case of Maqui, these studies are scarce [20,30].

#### **3. Chemical Characterization of Maqui**

The development of chromatographic and spectrophotometric techniques such as highperformance liquid chromatography (HPLC), coupled with diode detectors (DADs) and a mass spectrometer (MS) have favored advances in the identification and quantification of anthocyanins and other polyphenolic compounds [46,47].

The main bioactive compounds already reported in Maqui include phenolic acids (caffeic and gallic), flavonols (quercetin, rutin, and myricetin), flavonoids (catechin and epicatechin), and anthocyanins (delphinidin and its derivatives, malvidin, petunidin, cyanidin, and peonidin) [18] (Figure 3).

**Figure 3.** The chemical structure of the main chemical compounds present in the fruits of Maqui. Chemical structures corresponding to **a**, Delphinidin-3-glucoside; **b**, Cyanidin-3-glucoside; **c**, Ellagic acid; **d**, Quercetin; **e**, Kaempferol-3-glucoside; **f**, Myricetin; **g**, Isorhamnetin-3 -rutinoside; **h**, Granatin B; **i**, Eriodic-tyol-7-rutinoside; **j**, Hesperetin-7-rutinoside; **k**, 5-*O*-caffeoylquinic acid; **l**, Rutin; **m**, Ferulic acid and **n**, Sinapic acid.

Aqueous extracts of the fruits of Maqui contain a high content of phenolic acids (ferulic acid, gallic acid, caffeic acid), flavonoids (quercetin, myricetin, kaempferol, delphinidin, and cyanidin) and tannins (ellagitannins) [48]. On the other hand, the hydroalcoholic extract of the Maqui fruit presents high values of phenols and the presence of hydrophilic compounds, coumaric, gentisic, ferulic, and gallic acids, delphinidin-3,5-*O*-diglucoside, cyanidin-3-*O*-glucoside, and proanthocyanidin B, as well as hydrophobic compounds, catechins, quercetin, rutin, and anthocyanidins [49–51]. Cespedes et al. evaluated an ethanolic extract by extracting first with EtOH/H2O (6:4) followed by a subsequent extraction with H2O. This extract presented a composition based on gentisic acid, ferulic acid, gallic acid, p-coumaric acid, sinapic acid, 4-hydroxybenzoic acid, delphinidin, cyanidin, vanillic acid, delphinidin gallate, gallocatechin gallate, quercetin, rutin, myricetin, catechin and epicatechin, and anthocyanin glycosides [52]. Another study indicates the phytochemical

characterization of several Maqui berries by HPLC-DAD-ESI/MSn. Eight glycosylated anthocyanins, derived from cyanine and delphinine, have been reported: delphinidin-3-*O*sambubioside-5-*O*-glucoside, delphinidin-3,5-*O*-diglucoside, cyanidin-3,5-*O*-diglucoside, cyanidin-3-*O*-sambubioside-5-*O*-glucoside [53]. Sonication has been reported as an ideal alternative to obtain extracts from Maqui berries with high bioactivity, increasing the content of anthocyanins in Maqui berries, 3-glucosides, 3,5-*O*-diglucosides, 3-*O*-sambubiosides, and 3-*O*-sambubioside-5-*O*-glucosides of delphinidin and cyanidin as determined by HPLC with photodiode array and MS detection [46]. Maqui fruit extracts' main components are summarized in Table 1.

Only a few studies refer to the phytochemical analysis of leaf extracts of Maqui. The presence of indole and quinoline alkaloids has been reported in the leaves [19], being identified as aristoteline, serratoline, aristone, horbatinol, and horbatina [54,55]. Studies performed on ethanolic extracts of Maqui leaves reported the presence of some polyphenols such as gallic acid, coumaric acid, quercetin, myricetin, rutin, pelargonidin, and catechin. Interestingly, these compounds have been associated with the prevention of some CVD [56].


**Table 1.** Anthocyanins and phenolic compounds identified and quantified in Maqui fruit extracts.

Average % (range): percentage in which the compound is present in the Maqui fruit.

A study carried out in different regions of Chile showed that the total anthocyanin concentrations (TA) vary between 660 and 1500 mg cyanidin-3-*O*-glucoside/100 g of dried fruit, while the TP ranges between 1070 and 2050 mg GAE/100 g of dried fruit [17]. The total content of anthocyanins and polyphenols in Maqui is highly variable, depending on growing conditions, harvest times, plant genotype [17], and the different extraction procedures [57]. Maqui fruits have higher total polyphenol (TP) levels and antioxidant activity than other species recognized for their high phenolic content such as blueberries, pomegranates, blackberries, and red raspberries [58,59]. If we compare the Maqui with other berries, for example, Euterpe oleracea, better known as açai, which has also stood out for being one of the most nutritious fruits in South America, the phenolic content does not exceed the values referenced for Maqui [60].
