An Overview of Traditional Uses, Phytochemical Compositions and Biological Activities of Edible Fruits of European and Asian Cornus Species

Cornus species are widely distributed in central and southern Europe, east Africa, southwest Asia, and America. Several species are known for edible fruits, especially Cornus mas and Cornus officinalis. These delicious fruits, characterized by their remarkable nutritional and biological values, are widely used in traditional medicine. In contrast to the other edible Cornus species, C. mas and C. officinalis are the most studied for which little information is available on the main phytochemicals and their biological activities. Fruits are characterised by several classes of secondary metabolites, such as flavonoids, phenolic acids, lignans, anthocyanins, tannins, triterpenoids, and iridoids. The available phytochemical data show that the different classes of metabolites have not been systematically studied. However, these edible species are all worthy of interest because similarities have been found. Thus, this review describes the traditional uses of Cornus species common in Europe and Asia, a detailed classification of the bioactive compounds that characterize the fruits, and their beneficial health effects. Cornus species are a rich source of phytochemicals with nutritional and functional properties that justify the growing interest in these berries, not only for applications in the food industry but also useful for their medicinal properties.


Introduction
The genus Cornus L. (Cornaceae) comprises about 65 species widely distributed in central and southern Europe, east Africa, southwest Asia, and America [1]. Among the edible species of the genus, Cornus, Cornus mas L., C. officinalis Sieb. et Zucc, C. kousa Hanse, and C. controversa Hemsl. have fruits widely consumed in Europe and Asia [2].
C. mas (cornelian cherry) is native to southern Europe and southwest Asia [3]. This plant comes from the foothills of the Caucasus, and from there, it spreads over Romania, Bulgaria, Italy, Turkey, and the inland European continent [4]. Ripe (cherry red or dark) Turkey [28] Gastrointestinal disorders and inflammation Turkey [18] Greece [24] Slovakia [15] Albania [22] Serbia [21] Azerbaijan, Russia [12,14] Bowel disease Iran [17] Stomach ulcers and colitis Iran, Azerbaijan, Armenia, Georgia and Turkey [12][13][14] Dyspepsia and colitis Italy [29] [47] In Chinese traditional medicine, C. officinalis is known as a tonic to protect and nourish the kidney and liver [8]. In addition, it is accepted in the Chinese Pharmacopoeia (2010), and it is recognised as a principal and active herb in many medical prescriptions [44]. It is used alone or in combination with other herbs to ameliorate the clinical symptoms of liver and kidney disorders. In fact, the symptoms caused by kidney and liver deficiency, such as dizziness, weakness of the waist and knees, and tinnitus, were cured with C. officinalis and other plants [43]. Moreover, it is used to treat urinary disease, cough, asthmatic problems, diabetes, night sweats, frequent urination, impotence and seminal emission [48]. C. controversa is used in Korea and China as an astringent and tonic [46]. In traditional Korean medicine, C. kousa is employed to treat diarrhoea and as a haemostatic agent [47].
In conclusion, the traditional uses of these Cornus, mainly by the oral route, are very diverse. Some indications are often found: gastrointestinal disorders, throat and pulmonary infections, and kidney diseases. However, C. mas appears to be used to treat a wider range of infections.
C. mas fruits have been the subject of numerous phytochemical studies, and many of its compounds are described. The fruits are rich in flavonoids, iridoids, triterpenes and fatty acids.
The literature shows that the chemical composition of the fruits of C. officinalis has also been extensively studied. Similarly, flavonoids, tannins, and iridoids are the main chemical constituents of this species. In addition, the presence of organic acids, polysaccharides, sterols, phenylpropanoids, lignans, furans and mineral substances has also been described. Early work on the fruits of C. kousa concerned the identification of triterpene glycosides [54] and lignans [55,56].
Recently, a comprehensive chemical profile of anthocyanins, flavonoids and organic acids was published [57]. Currently, only a few studies have investigated the chemical composition of other Cornus species. The identification of flavonoids was performed in C. sanguinea, and a description of the anthocyanins in C. controversa was carried out.
The literature revealed that few studies of the chemical profile of C. sanguinea drupes have been conducted. Popović et al. [20] reported the presence of several quercetin 3-Oglycosides in the methanolic extract of the fruits. These are essentially quercetin glycosides that differ in the nature of the sugar part. Quercetin 3-O-glucuronide, 3-O-glucoside, 3-O-galactoside, 3-O-rhamnoside and 3-O-rutinoside (rutin) were found [20].
The flavonoids reported in C. officinalis have been characterised by naringenin, kaempferol and quercetin aglycons [59]. In addition, it should be noted that quercetin and kaempferol heterosides are numerous. Epicatechin 3-O-gallate is only found in C. officinalis fruits [60].
Among Cornus fruits, the lowest amounts of anthocyanins were found in the fruits of C. kousa. [11]. The anthocyanins isolated in Cornus fruits are reported in Table 3.

Lignans
Lignans were studied only in C. officinalis and C. kousa fruits. They were found by analysing an aqueous extract of C. officinalis and a hydroalcoholic extract of C. kousa.

Tannins
Analysis of the literature on iridoid plants showed that tannins are scarcely or not present in the fruits. Among the Cornus edible fruits, tannins have been reported only in C. officinalis and C. mas [73].
For C. mas, the determination of tannins in fruit extracts revealed their presence in small or medium quantities, and so far, no tannins have been isolated and identified [74,75]. However, it should be noted that ellagic acid, a marker of hydrolysable ellagitannins, has been described in fruits and that hydrolysable tannins, such as cornusiins, are numerous in the stones of these fruits [49].
While so far, no data concerning identifying tannins in C. mas fruits are available, many tannins have been isolated from C. officinalis fruits. Therefore, the richness of hydrolysable tannins in C. officinalis was considered a remarkable difference compared to C. mas. The main constituents are ellagitannins and gallotannins such as 7-O-galloyl-Dsedoheptulose [9,73,[76][77][78]. Among these tannins, dimers and trimers have molecular weights sometimes higher than 1000 D, such as cornusiins A−F and camptothins A−B. It should be noted that cornusiins were first found in the fruits of C. officinalis, and that recently, some of these compounds have been found in the stones.

Acids and Phenolic Acids
Twelve organic acids, namely malic, maleic, malonic, oxalic, succinic, citric, isocitric, tartaric, fumaric, quinic, shikimic, and ursolic acid, are identified in C. mas fruits [65,69,75,79,80]. Malic acid, followed by tartaric acid and citric acid, are the principal acids reported in the acidified aqueous extract of C. mas fruits collected in Bosnia and Herzegovina [65]. Fruits of C. mas collected in the Czech Republic possessed citric acid as the major organic acid [67]. Thirteen phenolic acids have also been described. Ellagic acid together with chlorogenic and gallic acids are the predominant phenolic acids found in hydroalcoholic extracts of C. mas fruits collected in Serbia [49]. Conversely, fruits from the Czech Republic reported chlorogenic acid as the principal phenolic acid. Other phenolic acids, including neochlorogenic acid, p-coumaric acid, vanillic acid, and ferulic acid, are reported in the methanol extract of C. mas fruits [81,82].
These metabolite classes have not yet been referenced for other edible Cornus. However, it can be noted that among these common metabolites, only ursolic, malic, citric and neochlorogenic acid have been identified in C. mas, C. officinalis and C. kousa. Table 5 reports the main acids and phenolic acids identified in Cornus fruits.

Iridoids
The taxonomic classification of the Cornus genus belongs to the super division Spermatophyta, division Magnoliophyta, class Magnoliopsida (dicotyledon), sub-class Rosidae, order Cornales, family Cornaceae and genus Cornus L. [1]. This classification is in accordance with iridoids as taxonomic markers of this genus [94,95]. Since Jensen et al. [94] and Bate-Smith et al. [95], it has been established that the taxonomically informative chemical compounds reported are cornin and loganin. Morroniside, whose formation was established in vivo derivation from secologanin, is only found in C. officinalis [94].
Cornel iridoid glycoside is one of the main components of C. officinalis, together with morroniside and loganin [96].
To the best of our knowledge, among the edible Cornus, the presence of iridoids in the fruits has only been investigated in the species C. mas and C. officinalis. Table 6 shows that all identified iridoids have a C10 skeleton. In the fruits of C. mas, the taxonomic markers of the genus Cornus were identified, as well as some derivatives such as sweroside, loganic acid and cornuside, an iridoid frequently found in the genus Cornus. Loganic acid, loganin, and sweroside have been detected in the hydroalcoholic extract of fruits and juice [52,82].
In addition to the iridoids found in C. mas extract, many other iridoids are described in the fruits of C. officinalis. For example, derivatives of loganin esterified with malic acid are present [105]. Secoiridoids are numerous; in addition to those mentioned above, demethoxycornuside, secologanoside, secoxyloganin were identified. However, the main secoiridoid is morroniside, whose isomeric forms are in equilibrium (α and β morroniside) [105].
Probably due to the solvent's nature, the α and β isomeric forms of morroniside ethyl and methyl were also isolated.
α,β-Morronisides are precursors of many derivatives. Glycosylation reactions between the C-7 of morronisides and glucose or fructose alcohol functions yielded twelve morroniside diglycosides (Cornusdiglycosides A−J) [114]. The alcohols of the morronisides reacted with the C-7 carbon of a second morroniside, forming dimers of methyl and ethyl morronisides (Cornuside A-J, Williamsoside D). The links between the two morronisides units are  [99]. In addition, unusual compounds such as logmalicides A and B [8], cornusfurosides A−D [110], and cornus phenosides A-I [111] were identified.

Other Constituents
Glucose, fructose and sucrose are present in high concentrations in the hydroalcoholic extract of C. mas fruits. Glucose is the major carbohydrate, followed by fructose and sucrose [74,115]. Contrary to what is observed in C. mas, fructose is the main sugar in C. kousa, followed by glucose. C. kousa presents a sweet taste and a higher total sugar content than other Cornus edible fruits [57]. In C. officinalis fruits, only sucrose is found [64]. C. mas fruits are rich in potassium, calcium, magnesium and sodium content. Other minerals such as phosphorus, iron, zinc, copper and manganese are present in smaller quantities. Variability was found in dependence on the collection site [74,[116][117][118]. For example, fruits from the Czech Republic showed a variability in potassium (3798-3411 mg/kg), calcium (656-301 mg/kg), magnesium (290-241 mg/kg), and sodium (82-58 mg/kg) depending on the type of cultivar [116]. Fruits from cultivars of Serbia exhibited 5609-1845 mg/kg of potassium, 466-27 mg/kg of calcium, 315-40 mg/kg of sodium, and 161-10 mg/kg of magnesium [74]. Variability in mineral content was also found in the samples collected in Croatia and Greece. In the C. mas fruits collected in Croatia, the main mineral was potassium (4019 mg/kg), followed by calcium (2074 mg/kg), magnesium (288 mg/kg) and sodium (22.9 mg/kg) [118]. A different composition was reported for fruits from Greece, with potassium (1320-880 mg/kg), phosphorus (90-80 mg/kg), magnesium (50-40 mg/kg), iron (45-19 mg/kg) and calcium (30-20 mg/kg) identified as the main minerals [117]. Compared with other fruit juices (pear, plum and apple juices), the C. mas fruit juice was richer in various minerals such as potassium, calcium, sodium, iron, zinc, copper and manganese [119]. There was little difference in the mineral composition between C. mas and C. officinalis fruits. These last species did not demonstrate the presence of sodium and phosphorus in their composition [120].
The vitamins identified in the aqueous extracts of C. mas fruits are ascorbic acid, αtocopherol, biotin, and riboflavin. Their concentration varies depending on the cultivar and climatic conditions [121]. As far as C. officinalis, only γ-tocopherol has been identified in the essential oil obtained from its fruits, and other data concerning vitamins are completely missed [122]. Regarding C. kousa, ascorbic acid, α-tocopherol and γ-tocopherol are found in its fruits [57]. In a recent study, only ascorbic acid was described in C. sanguinea [71].
Most published works do not mention the quantification of isolated metabolites or the different compounds in the extracts. The study of C. mas cultivars showed that the concentration of the latter changes, and these differences might explain the role of metabolites. For example, for fruits from C. mas cultivars, it has been shown that total phenolic content and ascorbic acid content are correlated with high biological efficiency in antioxidant activity [3].

Biological Properties
C. mas demonstrated antioxidant, antibacterial, antidiabetic, hypolipidemic, antiinflammatory, anticancer, and anticoagulant properties [1]. Additionally, C. officinalis is known to have different biological properties, such as antimicrobial, antineoplastic, hypoglycaemic, antioxidant, anti-inflammatory, cardioprotective, and neuroprotective activities, and has been traditionally used to improve and protect kidney and liver functions [48]. Conversely, few studies assessed the bioactivities of C. sanguinea, C. kousa and C. controversa [123] until now. Herein, we described the most investigated properties. The main investigated biological activities are summarized in Table 7.

Antioxidant Activity
The fruits of C. mas are a good source of antioxidants [3,70,81,[124][125][126][127]. Bayram and Ozturkcan [75] reviewed the antioxidant properties of different extracts, juice, liqueur and wine of C. mas. In a study by Serteser et al. [127], the hydroalcoholic extract of fruits from C. mas collected in Turkey showed an interesting inhibition against DPPH radical and H 2 O 2 activity and a high Fe 2+ chelating activity.
Another study analyzed the antioxidant capacities of the Cornus species typically found in the Mediterranean area. The hydroalcoholic extract obtained by C. mas fruits from Northern Greece showed high protection (98.6%) in the deoxyribose protein assay, along with the Hull thornless blackberry (red-black, Rubus fruticosus) (98.9%).
Raspberries and gooseberries presented a low capacity [125]. The antioxidant activity is influenced by the phytochemical content, which is influenced by different factors, including genotype, site of collection, maturity stage, climatic conditions, and extraction procedures. The methanol extract of C. mas air-dried fruits showed a lower FRAP value (83.9 µM ascorbic acid equivalent (AAE)/g, dry weight (DW)) compared with lyophilized fruits (FRAP value of 190 µM AAE/g, DW) [81,125].
During the drying process, a decomposition of bioactive compounds such as anthocyanins and ascorbic acid was observed, which is the reason for a reduced FRAP activity. Tural and Koca [70] investigated various C. mas genotypes of Turkey and reported different FRAP activity (16.21-94.43 µM AAE/g, fresh weight (FW)). In addition, the presence of pelargonidin 3-O-glucoside was the main pigment found in these fruits. Stanković et al. [128] used solvents of different polarities, such as methanol, water, ethyl acetate, petroleum ether, and acetone, to obtain different C. mas fruit extracts. The highest antioxidant activity was reported for the ethyl acetate extract with an IC 50 value of 11.06 µg/mL in the DPPH test.
Serteser et al. [127] compared the antioxidant activity of the hydroalcoholic extract of C. sanguinea fruits with other plants collected in Turkey, demonstrating that C. sanguinea has the highest DPPH radical scavenging activity. A similar trend was observed with Fe 2+ chelating and H 2 O 2 inhibition activities. Moreover, this extract was more active in the H 2 O 2 inhibition test than extracts of other plants. The methanol extract of C. sanguinea fruits collected in Iran showed an interesting antioxidant activity in the DPPH test, with an IC 50 value of 94.83 µg/mL [123]. A lower DPPH radical scavenging activity was found by Stanković and Topuzović [129], who analysed different C. sanguinea fruit extracts. The acetone extract showed a high capacity to reduce DPPH radicals with an IC 50 value of 247.83 µg/mL, followed by methanol extract (358.59 µg/mL), water extract (384.85 µg/mL), ethyl acetate extract (537.83 µg/mL) and petroleum ether extract (1202.85 µg/mL).
Previously, Lee et al. [130] studied the antioxidant activities of n-hexane, chloroform, ethyl acetate, ethanol, and water extracts of C. officinalis dried fruits. Antioxidant activity was investigated in a linoleic acid emulsion system by measuring the peroxide value, while radical scavenging activity was determined through the DPPH test. All extracts reported significantly higher DPPH radical scavenging activity than the positive control.
Water and ethanol extracts exhibited higher activities compared to other extracts. The same trend was observed in the linoleic acid emulsion system [130]. Additionally, in the same study, the protective effects of C. officinalis extract against apoptotic damage in H 2 O 2treated human umbilical vein endothelial cells (HUVECs) were assessed. Ethanol extract decreased cell death, preserving morphological normality by eliminating hydroxyl radicals.
In another study, Kim et al. [131] investigated the in vivo antioxidant effect of C. officinalis aqueous extract. In diabetic rats treated with a dose of 500 mg/kg, the activities of xanthine oxidase (XO), catalase (CAT), and glutathione-S-transferase (GST) were lower than the diabetic group. In contrast, the superoxide dismutase (SOD) activity increased by 26%. Thus, it is possible to deduce that antioxidant activity could be linked to the regulation of enzymes.
Successively, West et al. [102], investigated the antioxidant capacities of C. officinalis juice. This juice showed a promising DPPH radical scavenging activity (82.32 percent DPPH radical scavenging activity), moderate reducing power (30.71 mmol Fe 2+ /mL) and oxygen radical absorbance capacity (22.31 µmole Trolox equivalent/mL). Interestingly, the C. officinalis juice reducing power activity is greater than reported for other juices such as apple, pomegranate, açaí, black cherry, blueberry, cranberry, Concord grape, and orange juices [132]. The hydroalcoholic (70% ethanol) extract of C. officinalis fruits showed an interesting antioxidant activity in the DPPH test, with an IC 50 value of 99.32 µg/mL. In addition, in the ABTS test, this extract demonstrated a scavenging activity of 40.7% at a 100 µg/mL concentration. Additionally, it exhibited a high ability to reduce ferric complex (241.5 mM), similar to the positive control (256.1 mM). This high antioxidant activity should be associated with phenolic compounds found in this species [133].

Antidiabetic and Anti-Obesity Activities
Diabetes mellitus is a chronic metabolic disorder of multiple aetiology. Type 2 diabetes represents over 90% of diabetes and is associated with reduced sensitivity to insulin by peripheral tissues. One therapeutic approach for treating type 2 diabetes is to reduce postprandial hyperglycemia by inhibiting carbohydrate-hydrolysing enzymes, such as α-glucosidase and α-amylase [134].
C. officinalis, whose dried and mature fruits have traditionally been used for preventing diabetes mellitus, diabetic nephropathy, chronic inflammatory diseases and liver disease, is mainly distributed in Eastern Asia, Southern and Central Europe, and Eastern North America [135]. The antidiabetic properties of C. officinalis were studied in non-insulin-dependent diabetes mellitus (NIDDM) rats by oral administration (1 once daily for 30 d). In NIDDM, the expression of GLUT4 mRNA was significantly reduced. Still, the administration of C. officinalis alcohol extract notably increased the GLUT4 mRNA and protein expression, thus increasing insulin secretion and accelerating the metabolism of glucose [136].
Treatment with C. officinalis extract (oral administration of 300 mg/kg) in streptozotocin (STZ)-induced diabetic rats for 4 weeks reduced blood glucose and triglycerides (TG), significantly alleviating polyuria, polyphagia, polydipsia and weight loss. In addition, the oral administration of C. officinalis protected against damage to diabetes-induced pancreas and kidney injury, increased the pancreas's beta cells, and consequently increased insulin levels [137]. Previously, Yamabe et al. [138] assessed the antidiabetic properties of C. officinalis fruits in STZ-induced diabetic rats by gavage. The experimental groups that received the extract at doses of 50, 100, and 200 mg/kg body for 10 days presented a reduction in proteinuria, hyperglycemia, renal advanced glycation end-product (AGE) formation, and the expression of related proteins, such as the receptor for AGEs, nuclear factor-κB (NF-κB), transforming growth factor-β1, and Nε-(carboxymethyl)lysine [138].
Moreover, Park et al. [139] demonstrated that C. officinalis extract could reduce serum glucose levels by inhibiting the α-glucosidase enzyme. In another study, the insulin-mimetic action of C. officinalis on dexamethasone and 8-bromo-cAMP-induced phosphoenolpyru-vate carboxykinase (PEPCK) expression in H4IIE cells (rat hepatoma cell) was studied. C. officinalis methanol extract showed potent insulin mimic activity on PEPCK expression, increasing the cell viability and promoting insulin secretion [140]. The therapeutic effects of C. officinalis extract were also confirmed by Gao et al. [141]. Extract was administered at doses of 100, 200, or 400 mg/kg by oral gavage to STZ-induced diabetic rats. Reduction in blood glucose, high-density lipoprotein (HDL), low-density lipoprotein (LDL), TG, urinary protein levels and water consumption was observed. At the highest doses tested (200 and 400 mg/kg), creatinine and serum albumin levels were significantly reduced. The expression of peroxisome proliferator-activated receptor-gamma (PPARγ) was improved with SOD, CAT and glutathione peroxidase (GPx) activities. Thus, decreasing oxidative stress and enhancing the PPARγ expression can improve diabetic nephropathy.
Iridoids and secoiridoids are characteristic and active constituents of C. officinalis. They have been reported to possess anti-diabetic, antioxidant and anti-inflammatory properties [114]. The iridoid glycosides cornusdiglycosides A−J, isolated from the fruits of C. officinalis, were recently assessed for their potential α-glucosidase inhibitory activity. All iridoids inhibited α-glucosidase, with IC 50 values ranging from 78.9 to 162.2 µM [114]. Cornusdiglycosides A−H revealed better inhibitory activity than acarbose, used as a positive control.
An et al. [142] obtained total saponins from C. officinalis by using ultrasonic microwaveassisted extraction. This extract, purified by a non-polar copolymer styrene type macroporous resin (HPD-300), improved the glucose and lipid metabolism of streptozotocininduced diabetic mice and ameliorated liver and pancreas damage, inflammation as well as oxidative stress. The C. officinalis total saponin extract regulated insulin receptor-, phosphatidylinositol 3-kinase-, glucose transporter 4-, and protein kinase B-associated signaling pathways.
A literature survey also reported several studies that analysed C. mas for its potential antidiabetic activity. The hydroalcoholic extract of C. mas fruits (100 mg/kg, intraperitoneal (i.p.)) exhibited antidiabetic activity in alloxan-induced diabetic rats by reducubg serum glucose, LDL, TG, and very-low-density lipoprotein (VLDL) levels and by increasing HDL [143].
The oral administration of C. mas fruits (5, 10 and 15 g/meal) as a diet supplement for 20 days in hamsters decreased body weight and increased insulin levels [144]. Successively, Shamsi et al. [145] demonstrated that the oral administration of C. mas fruits (2 g/kg/day (d) for 4 weeks in alloxan-induced diabetic rats exhibited antidiabetic effects comparable to the positive control glibenclamide (0.6 mg/kg/d) [146].
In a clinical study, 60 patients with type 2 diabetes were randomly assigned to two groups receiving a C. mas anthocyanin-rich extract or placebo capsules (2 capsules twice daily after main food) orally along with their usual diet and physical activity. Each capsule contained 150 mg of anthocyanins isolated from the aqueous ethanol extract of C. mas fresh fruits. After 6 weeks, a significant increase in insulin levels and a decrease in haemoglobin AIc (HgbAIC) and TG levels were observed in the treated group in comparison to the placebo. These results suggested that the consumption of C. mas fruits might improve glucose intolerance in type 2 diabetic patients by increasing insulin levels and reducing the HgbAIC and TG levels [147].
Anthocyanins, of which C. mas fruits are very rich, have been shown to reduce the development of obesity through suppressed fat accumulation, significantly increasing the enzyme activity responsible for lipolysis of TG [148,149]. Jayaprakasam et al. [150] demonstrated that cyanidin and delphinidin glucosides stimulated insulin production in vitro. In contrast, Zhang et al. [151] showed that ursolic acid decreases blood glucose through insulin receptor phosphorylation and the stimulation of glucose uptake.
The consumption of lyophilized C. mas fruit powder (doses of 500 and 1000 mg/kg bw/d) reduced mice's fasting plasma glucose levels after 12 weeks without affecting the homeostatic model assessment of insulin resistance [152].
Similar results were obtained in the study by Dzydzan et al. [153], which demonstrated that red and yellow C. mas fruit ethanol extracts (20 mg/kg intraperitoneal injection (i.p.) for 14 days) were able to reduce the fasting plasma glucose levels and increase glucose intolerance. Moreover, the hydroalcoholic (75% ethanol) extract of C. mas fruits (100 mg/kg bw/d for 3 days) decreased serum glucose, TG, LDL, and VLDL levels and HDL levels. These effects were similar to glibenclamide treatment (50 mcg/kg i.p.) (an anti-diabetic drug), while reductions in TG and VLDL by hydroalcoholic extract of C. mas fruits were greater than glibenclamide [143]. Different extracts (obtained by different extraction procedures) and constituents of C. mas, including anthocyanins, iridoids, and ursolic acid, showed anti-diabetic effects by using several in vitro and in vivo procedures. However, more studies are needed to confirm which extract or compound is more effective.

Hypolipidemic and Anti-Atherosclerotic Properties
The effects of C. mas fruits on hypercholesterolemic rabbits were evaluated [154]. The administration of C. mas fruits to rabbits (1 g/kg body weight (b.w.)/d for 60 days) decreased serum fibrinogen levels. This effect was better than the anti-fibrinogenic drug, lovastatin (10 mg/kg b.w./d for 60 days). Therefore, the consumption of C. mas fruits as a diet supplement might be beneficial to reduce the risk of cardiovascular diseases in atherosclerotic patients. Authors applied the same protocol to rabbits, with a significant decrease in LDL, malondialdehyde (MDA), TG, total cholesterol (TC), fibrinogen and atherogenic index parameter. Additionally, an increase in antioxidant activity was observed. Probably, this effect is related to the number of phenolic compounds and vitamins (ascorbic acid and tocopherol) [155].
In another study on postmenopausal women, participants were randomly separated into two groups. One group received C. mas fruit extract (300 mg) 3 times a day for 8 weeks, and another group received a placebo. After the treatment, body weight, waist circumference, BMI, LDL/HDL ratio, TC/HDL ratio, and fibrinogen decreased. Moreover, C. mas supplementation increased Apo A1 and HDL levels compared to the control group. However, although both groups' fasting plasma glucose levels decreased, no change in leptin levels, serum insulin, insulin resistance index and insulin sensitivity were appreciated. This work revealed that daily consumption of C. mas fruits might help decrease blood sugar parameters and lower the risk of cardiovascular diseases. Successively, Sozanski et al. [68] investigated the protective effect of C. mas fruits against atherosclerosis and hypertriglyceridemia in a rabbit model. Fruits (100 mg/kg b.w.) or simvastatin (5 mg/kg b.w.) were administered orally for 60 days. A significant increase in liver peroxisome proliferator-activated receptor α (PPARα) protein expression and a significant decrease in serum triglyceride levels (44%), pro-inflammatory cytokines, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) was demonstrated. Based on these results, C. mas fruits showed protective effects against diet-induced hypertriglyceridemia and atherosclerosis across increased PPARα protein expression by regulating oxidative stress and inflammation [68]. It was demonstrated that the activation of PPARα leads to the increased tissue-specific expression of crucial genes involved in fatty acid uptake and β-oxidation [156].
PPARα decreases triglycerides by increasing free fatty acid β-oxidation, hepatic lipoprotein lipase expression, and expression of apolipoprotein V, and by decreasing expression of apolipoprotein CIII. Furthermore, PPARα activation regulates HDL metabolism by stimulating hepatic expression of apoA-I and apoA-II, thus raising HDL production in the liver, promoting HDL-mediated cholesterol efflux from macrophages, and inhibiting cellular cholesteryl ester formation activity, as well as contributing to an enhanced efflux of free cholesterol to extracellular receptors. PPARα activation may indirectly influence atherosclerosis development through the effects of glucose and lipid homeostasis on adi-pose tissue, liver, and skeletal muscle. In addition, PPARα activation may directly affect inflammation by modification of NF-κB and activator protein-1 (AP-1).
By regulating oxidative stress and inflammation, it is possible to conclude that both loganin and cornuside are responsible for the hypolipidemic activity of the extract. In fact, loganin showed anti-inflammatory capacities in various disease models, including acute pancreatitis and Parkinson's disease ( [157,158]. The iridoid was able to inhibit inflammatory cytokines and deactivation of the NF-κB signalling pathway. Moreover, it was demonstrated that the administration of loganin could improve memory-enhancing long-term memory in hippocampal tissues [159]. Cornuside was demonstrated to dilate vascular smooth muscle through endotheliumdependent nitric oxide signalling [160] and showed anti-inflammatory activity in the lipopolysaccharide (LPS)-induced inflammation model via the inhibition of NF-κB activity [161]. Previously, Kang et al. [162] observed that the addition of cornuside to human umbilical vein endothelial cell cultures reduced the mRNA expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) and diminished TNFα-induced NF-κB activation. In a carrageenan-induced mouse paw edema model, loganic acid exhibited a strong anti-inflammatory activity [163].
Loganic acid and cornuside were shown to increase PPAR-α levels by reducing atherosclerotic plaque formation in cardiovascular diseases [164].
The hypocortisol and hypolipidemic effects of C. mas fruits (5-15 g/daily) were studied in a hamster model [165]. At the highest dose, a decrease in cholesterol (108.3 mg/mL) and LDL (21 mg/mL) level were observed, as well as increased HDL (54 mg/mL) and TG (191.7 mg/mL) levels. The hamsters treated with C. mas fruits also showed a decrease in cortisol levels (28.8 ng/mL) compared with control (45.8 ng/mL).
As demonstrated by the different described works, the consumption of C. mas fruits may benefit lipid disorders. A recent systematic review and meta-analysis of the effects of cornelian fruit supplementation on the blood lipid profile of animal studies revealed that the supplementation considerably reduced the levels of LDL, TG, and cholesterol and increased HDL levels compared to the control group [166].
Consequently, these findings suggest that C. mas fruits supplementation may have lipid-modifying properties, which might be because these fruits are a good source of polyphenols and anthocyanins. However, long-term clinical studies and well-designed human studies should be necessary to further evaluate the impacts of cornelian consumption on various health outcomes.
C. officinalis was evaluated for its hypolipidemic activity [167]. The extract was able to reduce serum and hepatic total cholesterol levels and lipid peroxidation at an oral dose of 50, 100, or 200 mg/kg for 10 days. Moreover, expression of the sterol regulatory elementbinding protein (SREBP)-2 was reduced, whereas expression of the PPARα protein was enhanced. These results suggest using C. officinalis to prevent cardiovascular disease by controlling cholesterol levels and the expression of proteins related to lipid metabolism.

Neuroprotective Effects
A literature survey revealed the presence of several studies that have proposed C. officinalis and C. mas as potential therapeutic agents to treat neurodegenerative diseases, including Alzheimer's disease (AD).
By using APP/PS1/tau triple transgenic (3 × Tg) mice as a model of AD, Yang et al. [168] revealed that cornel iridoid glycoside, the dominant active constituent of C. officinalis, could ameliorate learning and memory impairments of 3 × Tg mice by downregulating the expression of Aβ and full-length amyloid precursor protein, as well as decreasing the hyper-phosphorylation of tau protein. These results were confirmed by Ma et al. [169], which demonstrated that this iridoid could reduce the hyperphosphorylation and aggregation of tau protein in the amygdala, prevent neuronal loss, and suppress the hyperactivity phenotype of AD. Tian et al. [170] used immobilization stress that induced depressive-like and anxiety-like behaviours and hippocampal neuronal damage in rodents to investigate the protective properties of C. officinalis extract on nerve injury. Results showed that C. officinalis successfully alleviated oxidative stress, decreased immobility time in the forced swim test, increased serotonin levels and significantly reduced corticosterone and β-endorphin levels. Iridoid glycosides of C. officinalis could reduce corticosterone-induced PC12 cell damage [97]. Corticosterone-induced PC12 injury is considered an in vitro experimental model for depression, and PC12 cells have typical neuron characteristics and are widely used to study neurological diseases [171]. In another study [172], a decoction of C. officinalis fruits exhibited protective effects against neurodegenerative diseases. Treatment with an extract (60 µg/mL) stimulated neurite extension similarly to a prominent neurotrophic factor, increasing the percentage of adrenal gland pheochromocytoma (PC12) cells bearing neurites.
The administration of freeze-dried C. mas fruits protected the brain tissue by reducing the amount of free radicals generated in the brain tissue. These effects were demonstrated in three types of diet: control, fructose and high-fat diets in rats with increased activity of catalase (CAT) and paraoxonase (PON) in brain tissue and decreased levels of the protein carbonyl group and thiol groups in brain tissue as well as in plasma [173]. PON is responsible for the anti-atherogenic effects of HDL in blood, possesses anti-inflammatory properties and prevents the oxidation of lipoproteins [174]. Phenolic compounds and ascorbic acid in C. mas fruits probably play a significant role in increasing PON-1 levels [175].
Some Cornus constituents have been studied as potential neuroprotective agents. Among them, morroniside can promote both the proliferation and differentiation of endogenous neural stem cells and the migration of neural stem cells in vivo. Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are important bioactive molecules in the nervous system for their role in developing the central nervous system while maintaining the normal functions of the mature central and peripheral nervous system neurons. Morroniside enhanced the function of NGF and the expression of BNDF [176,177]. The effects of morroniside on the expression of the Wnt7a gene and adenomatous polyposis coli (APC) were assessed in rats with focal cerebral ischemia-reperfusion injury [178]. The Wnt is a pathway that can regulate cell proliferation and differentiation during the growth and development of humans and animals, particularly in brain plasticity. Wnt7a is an important ligand that can regulate the acceleration of cell growth and differentiation and inhibit glial regeneration. Conversely, the APC gene inhibits the Wnt signaling pathway. Morroniside promoted the expression of Wnt7a and inhibited the expression of APC.

Antimicrobial Activity
The n-hexane extract of C. mas fruits showed significant antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli at the tested dose of 10 µL/disc [179]. Methanol and ethanol extracts of C. mas fruits revealed antibacterial activity against E. coli, S. aureus, and Pseudomonas aeruginosa, but demonstrated no antifungal properties against Candida albicans and Aspergillus fumigates. However, Streptococcus pyogenes and Trichophyton mentagrophytes resulted in resistance [180].
The antimicrobial effects of a hydroalcoholic extract of C. mas fruits were successively investigated against 13 species of bacteria and yeast [49]. The Gram-positive strains Listeria monocytogenes, Bacillus cereus, S. aureus, and Sarcina lutea and the Gram-negative strains Proteus vulgaris, Shigella sonnei, and Salmonella enteritidis were the most sensitive. A positive correlation between antimicrobial activity and total phenol content was found. The scientifically proven antibacterial activity justified using C. mas fruits in traditional medicine to treat gastrointestinal disorders and diarrhoea, skin diseases, and urinary infections [181][182][183][184]. The antimicrobial effect of apple juice supplemented with C. officinalis fruits against E. coli O157:H7 was evaluated [185]. Results showed that adding C. officinalis fruits inactivates E. coli O157:H7 in apple juice. The most promising results were observed at 21 • C, while at 7 • C, only a reduction of 2.3 log cfu/mL was observed. Therefore, C. officinalis fruit extract can be used with temperature and storage time conditions to inactivate E. coli O157:H7 in apple juice.
The hepato-protective effect of C. mas was also proven. Fruits were administered at 200 and 500 mg/kg b.w., ameliorating the levels of aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) and reducing the oxidative stress and elevated hepatic MDA content in CCl4-induced hepatotoxicity in rats by Alavian et al. [188]. Another research group demonstrated that the hydroalcoholic extract of C. mas fruits exerted renal-protective effects by improving renal lesions, antioxidant enzymes, lipid peroxidation-induced MDA levels, and other biochemical parameters, including creatinine, uric acid and serum urea levels [189].
The oral administration of a hydroalcoholic extract of C. mas fruits (50, 200 and 400 mg/kg b.w./d) exhibited a significant reduction in the platelet distribution width (PDW) [190], a specific marker of platelet activation [191]. This marker is activated when blood coagulation is necessary and consequently decreases with platelets' inactivation.
In rats, CCl 4 injection can decrease antioxidant enzymes and increase creatinine kinase, lactate dehydrogenase and MDA, with consequent damage to different tissues, including the heart. Treatments with the hydroalcoholic extract of C. mas fruits at a dose of 300 and 700 mg/kg b.w./d for 16 days in CCl4-induced intoxicated rats showed cardioprotective effects. These effects were linked to attenuating myocardial lipid peroxidation levels and recovering the enzymatic defense system by increasing the levels of SOD, CAT, and GPx and modulating cardiac tissue's bioenergetics state [192].
Loganin, one of the most common iridoid glycosides isolated from Cornus species, was recently investigated on angiotensin II-induced cardiac hypertrophy [193]. Angiotensin II is a significant component of the renin-angiotensin system and plays an important role in triggering hypertension and myocardial hypertrophy. Loganin was demonstrated to inhibit angiotensin II-provoked cardiac hypertrophy and cardiac damage in the H9C2 cell line in mice. It showed cardio-protective effects through a decrease in pro-inflammatory cytokine secretion, the suppression of the phosphorylation of critical proteins including STAT3, JAK2, IκBα, and p65, and the attenuation of cardiac fibrosis. These promising results are supported by previous works that have shown the ability of loganin to suppress inflammatory responses by downregulating the activation of JAK2/STAT3 and NF-κB signaling pathways and decreasing the production of inflammatory cytokines [194][195][196][197].
The administration of loganic acid, isolated from C. mas fruits, at a dose of 0.7% aqueous solution containing 0.15% sodium hyaluronate significantly reduced (25%) conjunctivitis-induced intraocular pressure (IOP) of the eye in a rabbit model [82].
This activity is of certain interest as a possible treatment for diabetic retinopathy. The decrease in IOP was probably ascribed to reducing nitric oxide [198,199]. A similar effect was also observed in a glaucoma model. Glaucoma is characterised by high levels of nitric oxide that decrease after loganic acid treatment [198,199].
Osteoporosis is a chronic illness closely linked with the aging processes. Based on traditional medicine and modern findings in the pathogenesis and treatment of osteoporosis, a variety of natural products present in preparations of this plant play a beneficial role.
C. officinalis significantly inhibits receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclast differentiation in a dose-dependent manner and RANKLinduced phosphorylation of p38 and c-JUN N-terminal kinase. In addition, the protein expression of c-Fos and nuclear factor of activated T cells cytoplasmic 1 (NFATc1) is suppressed due to the RANKL-induced degradation of I-κB kinase [200]. The effects of the main constituents of C. officinalis fruits, such as morroniside, on osteoarthritis in human chondrocytes were studied. Morroniside supported the survival of chondrocytes with articular cartilage thickness, increasing the levels of type II collagen and improving the level of proteoglycans in the cartilage matrix [201].
Studies conducted on C. officinalis revealed a reduction in the incidence of infections or allergic illnesses by stimulating the innate immune system. In particular, Kim, Kim, and Lee [202] evaluated the therapeutic effects of C. officinalis in a mouse model of allergic asthma. This model demonstrated reduced production of Th2 cytokines (IL-5), eotaxin, and specific immunoglobulin E (IgE) and reduced eosinophil infiltration. C. officinalis fruits improve non-specific immunity, specific humoral immunity, and cellular immunity, as confirmed in a previous study conducted by Du et al. [203] in immuno-depressed mice.

Antidiabetic and anti-obesity activities
Hydroalcoholic extract of fresh fruits Antidiabetic activity in alloxan-induced diabetic rats by reductions in serum glucose, LDL, TG, and VLDL levels and increase in HDL [143] Fresh fruits Iran Decrease in body weight and increase in insulin levels [144][145][146] Hydroalcoholic extract of fresh fruit Iran Increase in insulin level, decrease in HgbAIC and TG levels [147] Aqueous extract of fresh fruits Slovakia Reduction in plasma glucose levels [152] Ethanol extract Reduction in plasma glucose levels and increase in glucose intolerance [153] Cyanidin and delphinidin glucosides Stimulation of insulin production [150] Ursolic acid Decrease in blood glucose and stimulation of glucose uptake [151] Hypolipidemic and anti-atherosclerotic properties

Fruit extract Iran
Decrease in body weight, waist circumference, BMI, LDL/HDL ratio, TC/HDL ratio, and fibrinogen, and increase in Apo A1 and HDL levels [204] Fresh fruits Poland Protective effects against diet-induced hypertriglyceridemia and atherosclerosis through an increase in PPARα protein expression and a significant decrease in serum triglyceride levels, pro-inflammatory cytokines, IL-6, and TNF-α [68] Fresh fruits Iran Decrease in cholesterol, LDL, and cortisol levels; increase in HDL and TG levels [165] Loganin Inhibition of inflammatory cytokines and deactivation of NF-κB signalling pathway [157,158] Cornuside Dilated vascular smooth muscle through endothelium-dependent nitric oxide signalling [160] Cornuside Anti-inflammatory activity via the inhibition of NF-κB activity [161] Loganic acid and cornuside Increase in PPAR-α levels with reduced atherosclerotic plaque formation in cardiovascular diseases [164] Neuroprotective effects

Fresh fruits Poland
Protection of the brain tissue by reducing the free radical content by increased activity of CAT and PON [173] Antimicrobial activity n-Hexane extract of fresh fruits Russian Antibacterial activity against S. aureus and E. coli [179] Methanol and ethanol extracts of fresh fruits Poland Antibacterial activity against S. aureus, E. coli P. aeruginosa [180] Hydroalcoholic extract of fresh fruits Serbia Antibacterial activity against L. monocytogenes, B. cereus, S. aureus, S. lutea, P. vulgaris, S. sonnei, and S. enteritidis [49] Cytotoxic activity Hydroalcoholic extract of dried fruits Iran Cytotoxic activity against MCF-7, PC-3, SKOV-3 and A549 cells [186] Hepatoprotective effect Hydroalcoholic extract of dried fruits Iran Amelioration of AST, ALT and ALP levels [188] Renal protective activity

Hydroalcoholic extract of dried fruits Iran
Renal protective effects via improving renal lesions, antioxidant enzymes, creatinine, uric acid and serum urea levels [189] Cardioprotective and antiplatelet activities

Hydroalcoholic extract of dried fruits Iran
Cardioprotective effects through a reduction in PDW, attenuating myocardial lipid peroxidation level and recovering enzymatic defence system by increasing the levels of SOD, CAT, GPx, and modulating the bioenergetics state of cardiac tissue [190,192]

Loganic acid
Reduction in nitric oxide with consequent decrease in IOP of the eye, ameliorating glaucoma [82,198,199] C. sanguinea

Alcoholic extract of fruits China
Increase in GLUT4 mRNA and protein expression with an increase in insulin production and accelerated glucose metabolism [136] Fresh fruits Japan Reduction in proteinuria, hyperglycaemia, renal AGE formation, and the expression of related proteins, such as the receptor for AGEs, NF-κB, transforming growth factor-β1, and Nε-(carboxymethyl)lysine [138] Methanol extract of fruits Increase in cell viability through insulin mimicked activity of PEPCK expression [140] Hydroalcoholic extract of fresh fruits China Decrease in blood glucose, HDL, LDL, TG, creatinine, and serum albumin levels [141]

Extracts or Compounds Country Effects Reference
Cornusiridoid A−F α-Glucosidase inhibition [99] Total saponin extract Amelioration of liver and pancreas damage, regulation of insulin receptor, phosphatidylinositol 3-kinase, glucose transporter 4, and protein kinase B-associated signalling pathways [142] Hypolipidemic and anti-atherosclerotic properties Fresh fruits Reduction in serum and hepatic TC levels and SREBP-2. Increase in PPAR-α levels [167] Neuroprotective effects

Aqueous extract of dried fruits South Korea
Alleviation of oxidative stress, decrease in immobility time in the forced swim test, an increase in serotonin levels and reduction in corticosterone and β-endorphin levels [170] Decoction of fresh fruits China Protective effects against degenerative disease through stimulation of the neurite extension, increasing the percentage of PC12 [172] Cornel iridoid glycoside Amelioration of learning and memory impairment by down-regulating the expression of Aβ and full-length amyloid precursor protein, as well as decreasing the hyperphosphorylation of tau protein [168,169] Morroniside Enhanced NGF function and BDNF expression. Promotion of the expression of Wnt7a and inhibition of the APC expression [176][177][178] Antimicrobial activity Decoction extract of fresh fruits China Antibacterial activity against E.coli O157:H7 [185] Cytotoxic activity Decoction extract of fresh fruits China Inhibited hepatocellular carcinoma cell and leukemic cell growth [187] Cardioprotective activity

Extract fruits Korea
Inhibited receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclast differentiation and RANKL-induced phosphorylation of p38 and c-JUN N-terminal kinase. Suppression of the protein expression of c-Fos and NFATc1 [200] Morroniside Increase in type II collagen levels and improvement of proteoglycan levels in cartilage matrix [201]

Immunomodulatory activity
Aqueous extract of fresh fruits Korea Reduction in the incidence of infections or allergic illnesses through the stimulation of the innate immune system; in particular, decreased production of IL-5, eotaxin, and IgE [202] Hydroalcoholic extract of dried fruits China Improvement of the non-specific immunity, specific humoral immunity and specific cellular immunity [203] 6. Toxicity C. mas has been analysed for its potential toxicity [102,189,205]. West et al. [102] investigated the acute toxicity of C. mas in both animal and human models. The authors found that 5 mL/kg bw of C. mas supplementation in rats for 14 days showed no adverse effects. The average lethal dose (LD 50 ) value was <5200 mg/kg. In a human study, it was demonstrated that 100 g/day for 6 weeks of fresh C. mas fruit consumption did not show any toxicity [205]. Previously, Es Haghi et al. [189] showed that doses of a water extract of C. mas fruits in the range 100-1650 mg/kg for 2 weeks in mice showed no toxicity (LD 50 value of 1270 mg/kg). Toxicity studies have shown C. mas consumption is safe and has no side effects; however, high doses and long-term toxicity evaluations are required.

Conclusions
Since ancient times, fruits from the Cornus genus have been used in traditional medicine for their beneficial health properties. Some species are edible, particularly the European C. mas and C. sanguinea. C. officinalis, C. kousa and C. controversa are the edible species diffused in the Asiatic continent.
C. mas and C. officinalis are extensively studied plants with a high biological value, which is mainly connected to their polyphenols and iridoid content.
In particular, C. mas fruits are well-known as traditional components of jams, liquors, and other fruit-based products and are a rich source of bioactive molecules. Significant amounts of anthocyanins, flavonoids, and iridoids were identified in the fruits. These phytochemicals are linked with remarkable antioxidant, anti-inflammatory, and cancer properties. Additionally, C. officinalis exhibits a broad range of pharmacological activities, including anti-inflammatory, antioxidant, antiaging, cardioprotective, neuroprotective, and antibacterial effects. As described in our review, iridoids, flavonoids, terpenoids, polysaccharides, organic acids, and other compounds have been isolated and identified from C. officinalis fruits. This interest has recently prompted researchers to investigate also interspecific hybrids of C. mas × C. officinalis [206]. These hybrids are characterized by more iridoids than C. mas and more anthocyanins than C. officinalis.
Few phytochemical studies are present for other edible Cornus species. According to this review, the fruits of these Cornus species are rich in bioactive compounds, such as flavonoids, iridoids, anthocyanins, carotenoids, and other secondary metabolites; thus, their use might represent some benefits to human health.
Fruit extracts could effectively counter the onset of various illnesses linked to diabetes, obesity, and kidney and gastrointestinal disorders. However, exhaustive future studies of C. sanguinea and C. controversa fruits' biological properties and chemical composition are still required. In addition, pharmacokinetic and pharmacodynamic studies on C. mas and C. officinalis fruits and their derived bioactive metabolites are necessary to confirm their effectiveness for human use. Moreover, toxicity studies on phytocomplex and single bioactive compounds are necessary to ensure the safety of these uses.