Medicinal plants are very important worldwide, both when used alone and as a supplement to traditional medication ^{[1][2][3][4][5]}[1,2,3,4,5]. For many years, humans have employed plants as a source of food, flavoring, and medicines ^{[6][7][8][9][10]}[6,7,8,9,10]. Various parts of medicinal plants such as seeds, leaves, flowers, fruits, stems, and roots are rich sources of bioactive compounds ^[11][12][13][11,12,13]. Bioactive compounds should be considered as important dietary supplements ^{[14][15][16][17][18][19]}[14,15,16,17,18,19]. Polyphenols are a group of secondary metabolites involved in the hydrogen peroxide scavenging in plant cells [20]. Phenolic compounds are second only to carbohydrates in abundance in higher plants, and they display a great variety of structures, varying from derivatives of simple phenols to complex polymeric materials such as lignin ^{[21][22][23][24][25][26]}[21,22,23,24,25,26]. Phenolic compounds are known for their notable potential activity against various human viruses, and phenolic compounds also have immunomodulatory and anti-inflammatory activity [27]. The most abundant phenolic compounds are phenolic monoterpenes (carvacrol and thymol) and diterpenes (carnosol, carnosic acid, and methyl carnosate), hydroxybenzoic acids (p-hydroxybenzoic, protocatechuic, gallic, vanillic, catechol, and ellagic), phenylpropanoic acids (p-coumaric, caffeic, rosmarinic, chlorogenic, ferulic, cryptochlorogenic, and neochlorogenic), phenylpropenes (eugenol), coumarins (herniarin and coumarin), flavanoes (naringenin, eriocitrin, naringin, and hesperidin), flavones (apigenin, apigetrin, genkwanin, luteolin, luteolin 7-glucuronide, cynaroside, scolymoside, salvigenin, and cirsimaritin), and flavanols (catechin, astragalin, kaempferol, methyl ethers, quercetin, hyperoside, isoquercetin, miquelianin, and rutin) ^[28][29][28,29].

Plant phenolics are considered promising antibiofilm and antifungal agents ^[30][31][30,31]. Diaz et al. [32] also reported that the levels of phenolic and flavonoid compounds were correlated with the anti-inflammatory and antioxidant activities of medicinal plants. Tukun et al. [33] reported that phenolic content is significantly connected to antioxidant activity, and halophytes have high content of nutrients and phenolic metabolites. Some of the most important phenolic compounds recognized from medicinal plants are syringic acid and gallic acid from Moringa oleifera [34]; gallic acid, vanillic acid, 4-hydroxybenzoic acid, and syringic acid from Peganum harmala [35]; rosmarinic acid from Rosmarinus officinalis L. and Mentha canadensis L. [36]; vanillin from Thymus vulgaris [37]; caffeic acid and p-coumaric acid from Ocimum basilicum L., Thymus vulgaris L., Salvia officinalis L., and Origanum vulgare L. [36]; piceatannol glucoside, resveratroloside, and piceid from Polygonum cuspidatum [38]; trans-rhapontin, cis-rhapontin, and trans-desoxyrhaponticin from Rheum tanguticum Maxim. Ex Balf. [39]; herniarin from Matricaria chamomilla [40]; kayeassamin I, mammeasin E, and mammeasin E from Mammea siamensis [41]; scopoletin, fraxetin, aesculetin, fraxin, and aesculin from Fraxinus rhynchophylla [42]; phyllanthin, niranthin, hypophyllanthin, nirtetralin, virgastusin, heliobuphthalmin lactone, and bursehernin from Phyllanthus amarus [43]; schisanchinin A, schisanchinin B, schisanchinin C, and schisanchinin D from Schisandra chinensis [44]; 7-methyljuglone from Drosera rotundifolia [45], rhein, physcion, chrysophanol, emodin, and aloe-emodin from Rheum palmatum and Rheum hotaoense [46]; curcumin, demethoxycurcumin, and bis-demethoxycurcumin from Curcuma longa [47]; luteolin, apigenin, orientin, apigenin-O-glucuronide, and luteolin-O-glycoside from Origanum majorana [48]; glycitein, genistein, formononetin, daidzein, prunetin, biochanin A and daidzin, and genistin from Medicago spp. [49]; kaempferol 3-O-glucoside and isorhamnetin 3-O-galactoside from Tephrosia vogelii [50]; rutin, kaempferol 3-O-rhamnoside, and quercetin 3-O-glucoside from M. oleifera [34]; gallocatechin and catechin from Mentha pulegium [48]; taxifolin, taxifolin methyl ether, and dihydrokaempferide from Origanum majorana [48]; hesperidin, naringenin-O-rhamnoglucoside, and isosakuranetin-O-rutinoside from Mentha pulegium [48]; and punicalagin, pedunculagin I, granatin A, ellagic acid, ellagic acid pentoside, ellagic acid glucoside, and punigluconin from Punica granatum [51]. Phenolic phytochemicals include flavonoids, flavonols, flavanols, flavanones, flavones, phenolic acids, chalcones, isoflavones, tannins, coumarins, lignans, quinones, xanthones, curcuminoids, stilbenes, cucurmin, phenylethanoids, and several other plant compounds, owing to the hydroxyl group bonded directly to an aromatic hydrocarbon group [52]. The classes of phenolic compounds in plants are shown in Table 1.

Phenolic acids include two subgroups, i.e., hydroxybenzoic and hydroxycinnamic acids [53]. Hydroxybenzoic acids consist of gallic, p-hydroxybenzoic, vanillic, protocatechuic, and syringic acid, which, in common, have the C₆-C₁ structure [53]. Hydroxycinnamic acids, on the other hand, are aromatic compounds with a three-carbon side chain (C₆-C₃), with caffeic, p-coumaric, ferulic, and sinapic acids being the most common [52]. Gallic acid is present in cloves (Eugenia caryophyllata Thunb.), while protocatechuic acid can be found in coriander (Coriandrum sativum L.), dill (Anethum graveolens L.), and star anise (Illicium verum Hook. f.) [54]. Caffeic acid is found among others in parsley (Petroselinum crispum L.), ginger (Zingiber officinale Rosc.), and sage (Salvia officinalis L.), and p-coumaric acid is found in oregano (Origanum vulgare L.), basil (Ocimum basilicum L.), and thyme (Thymus vulgaris L.) [54]. Some samples of hydroxybenzoic and hydrozycinnamic acids are presented in Table 2.

Flavonoids include the largest group of plant phenolics, responsible for over half of the eight thousand naturally occurring phenolic constituents ^[55][56][55,56]. Flavonoids are low molecular weight compounds, including fifteen carbon atoms, arranged in a C₆-C₃-C₆ configuration [53]. The genetic structure of main classes of flavonoids are shown in Table 3.

Phenolic phytochemicals play a variety of protective roles against abiotic stresses, such as ultraviolet (UV) light, or abiotic stresses, namely predator and pathogen attacks [57]. Phenolic phytochemicals are utilized by humans to treat several ailments including bacterial, protozoal, fungal, and viral infections, inflammation, diabetes, and cancer. Biosynthesis and accumulation of polyphenol and other secondary metabolites in plants is considered as an evolutionary reaction of biochemical pathways under adverse environmental influences, i.e., biotic/abiotic limitations, including increased salinity and drought stress ^[58][59][60][58,59,60]. Some of the extraction methodologies of phenolic components from medicinal and aromatic plants are maceration, digestion, infusion, decoction, Soxhlet extraction, percolation, aqueous alcoholic extraction by fermentation, counter-current extraction, ultrasound extraction, supercritical fluid extraction, and phytonics stage. The principle factors shaping the production of phenolic components are the water supplied to plants and the time of stress exposure, and, among the various quantification methods, HPLC and colorimetric tests are the most utilized to quantify the phenolic compounds analyzed [61]. Djeridane et al. [62] reported that the phenolics in medicinal plants provide substantial antioxidant activity. A positive, significant linear connection between antioxidant activity and total phenolic content revealed that phenolic components were the dominant antioxidant constituents in medicinal plants ^[63][64][63,64]. Various groups of tests on phenolics indicated significant mean alterations in radical scavenging activity; tannins demonstrated the strongest activity, while most quinones, isoflavones, and lignans tested revealed the weakest activity ^[65][66][65,66]. The most abundant flavone in Cytisus multiflorus is the chrysin derivative, Kaempferol-3-O-rutinoside is the major flavonol in Malva sylvestris, and Quercetin-3-O-rutinoside is the principle flavonol in Sambucus nigra [66]. Nepeta italica subsp. cadmea and Teucrium sandrasicum are rich in phenolics, which indicated antioxidant and cytotoxic properties [67]. Through LC-ESI-MS analysis, five phenolic acids (quinic acid, syringic acid, gallic acid, p-coumaric acid, and trans-ferulic acid) and five flavonoids (catechin, epicatechin, quercetrin, rutin, and naringenin) were predominant and common in some desert shrubs of Tunisian flora (Pituranthos tortuosus, Ephedra alata, Retama raetam, Ziziphus lotus, Calligonum comosum, and Capparis spinosa) [68].

The main phenolic compounds in Matico (Piper angustifolium R.), Guascas (Galinsoga parviflora), and Huacatay were chlorogenic acid and hydroxycinnamic acid derivatives [69]. High phenolic and antioxidant activity-containing medicinal plants and species such as Chanca Piedra (Phyllanthus nirui L.), Yerba Mate (Ilex paraguariensis St-Hil), Zarzaparrilla (Smilax officinalis), and Huacatay (Tagetes minuta) have the highest anti-hyperglycemia-relevant in vitro α-glucosidase inhibitory activities with no effect on α-amylase [69]. Nineteen phenolic compounds from different groups are used in wound treatment, and the compounds are tyrosol, curcumin, hydroxytyrosol, luteolin, rutin, chrysin, kaempferol, quercetin, icariin, epigallocatechin gallate, morin, silymarin, taxifolin, hesperidin, naringin, puerarin, isoliquiritin, genistein, and daidzein ^{[70][71][72][73]}[70,71,72,73]. The most important identified phenolics in Phlomis angustissima and Phlomis fruticosa, medicinal plants from Turkey, by RP-HPLC-DAD were hesperidin, catechin, kaempferol, epicatechin, eupatorin, and epigallocatechin, and chlorogenic, syringic, vanillic, p-coumaric, ferulic, and benzoic acids [74]. Quercetin of Cordia dichotoma G. Forst. (Lashusa) is the most notable phytoconstituent responsible for the therapeutic efficacy [75]. Vanillic acid, nepetin, verbascoside, and hispidulin, of Clerodendrum petasites S. Moore (CP) were chosen as potential phenolic active compounds in Thai traditional medicine for the treatment of different kinds of skin diseases ^[76][77][78][76,77,78]. Bouyahya et al. [79] reported that compounds such as terpenoids, alkaloids, flavonoids, phenolic acids, and fatty acids of Arbutus unedo L., Thymus capitatus managed diabetes by several mechanisms such as enzymatic inhibition, interference with glucose and lipid metabolism signaling pathways, and the inhibition and the activation of gene expression involved in glucose homeostasis.

Grewia tenax, Terminalia sericea, Albizia anthelmintica, Corchorus tridens, and Lantana camara are frequently used to treat gastroenteritis and include higher total phenolic and flavonoid contents in Namibia ^{[80][81][82][83][84][85]}[80,81,82,83,84,85]. The most important phenolics identified from pomegranate are punicalin, gallic acid, ellagic acid, pyrogallol, salycillic acid, coumaric acid, vanillic acid, sesamin, and caffeic [86], and phenolic compounds have been discovered to have inhibitory effects again α-glucosidase activities [87]. Two new phenolics, leucoxenols A and B, were obtained and identified as major secondary metabolites from the leaves of Syzygium leucoxylon [88]. Phenolics are main phytochemicals found in Cyathea species, and Cyathea has been considered to be a potential source of novel cancer therapeutic compounds [89]. Purified phenolic compounds from the bark of Acacia nilotica showed insecticidal potential against Spodoptera litura, and they could provide substitutes to synthetic pesticides for controlling various pests [90]. Bellumori et al. [91] reported that the roots of Acmella oleracea L. had about twice as many phenols as the aerial parts, and caffeic acid derivatives were the main phenolic compounds in roots and aerial parts. Kaempferol was found as the most abundant phenolic compound in basil leaf extract after using an HPLC-UC method (61.4 mg.kg⁻¹) [92]. Apple fruit (Annona squamosa L.) has a specific spatial distribution of microbes and phenolics, its peel phenolics contain antimicrobial activity against several Gram-positive bacteria, and its peel phenolics had a growth-promoting effect toward autochthonous yeasts ^{[93][94][95][96]}[93,94,95,96]. The phenolic contents of Cyathea dregei (root and leaves), Felicia erigeroides (leaves and stems), Felicia erigeroides (leaves and stems), Hypoxis colchicifolia (leaves), Hypoxis colchicifolia (leaves), and Senna petersiana (leaves) have shown high antimicrobial and cyclooxygenase (COX) inhibitory activities [97].

The most important techniques for analysis of phenolic compounds and extracts are nuclear magnetic resonance (NMR), high performance liquid chromatography (HPLC) with ultraviolet-visible (UV-Vis) or photodiode array (PDA) detector or coupled to mass spectrometry (MS), derivatization (silylation, alkylation, etc.) as well as gas chromatography (GC) or GC-MS analysis, phytochemical screening such as total flavonoid content (TFC), total phenolic content (TPC), etc., and antioxidant potential tests such as 2,2-dipehnyl-1-picrylhydrazyl (DPPH), etc. ^{[97][98][99][100][101][102][103][104][105][106][107]}[97,98,99,100,101,102,103,104,105,106,107]. Solid-liquid extraction (SLE) is one of the main methods for extraction of phenolic compounds, specially syringic acid, catechin, and p-coumaric acid, which is simple, well established, and widely used [108]. Ultrasound-assisted extraction (UAE) is often used for extraction of gallic acid and rutin, which is easy to execute, uses inexpensive equipment, and consumes less solvents, and has fast extraction, good extraction yield, and low impacts on the environment [109]. Supercritical fluid extraction (SFE) usually applies for gallic acid, anthocyanin, and protocatechuic acid, which has high selectivity, cheaper and safer solvent, easily controlled extraction conditions, environmental friendliness, low operating temperature, and easy separation of solvent from solutes [110]. Microwave-assisted extraction (MAE) is used for extraction of 3-caffeoylquinic acid, 5-caffeoylquinic acid, and ellagic acid, which has short extraction time and low solvent consumption [111]. Pressurized liquid extraction (PLE) applies for extraction of rutin and quercetin, which consumes fewer organic solvents, has higher probability to avoid organic solvents by using water only, and is fast and efficient [112]. For extraction of proanthocyanidin, naringin, and hesperidin, enzyme-assisted extraction (EAE) is proposed, which is safe and green and does not need complex paraphernalia [113]. Key points about phenolic acids and their derivatives are shown in Table 4.

Flavonoids and phenolics are commonly known as the largest phytochemical molecules with antioxidant characteristics [124]. Traditional Chinese medicinal plants that contain phenolic acids and flavonoids have shown high antioxidant activity. Nepeta italica subsp. Cadmea and Teucrium sandrasicum are rich in phenolic, tannin, and flavonoids content, which showed antioxidant and cytotoxic properties. Bauhinia variegata L. contained flavonoid compounds and revealed antioxidant properties against oxidative damage by radical neutralization, iron binding, and decreasing power abilities [125]. The rhizome extracts of Polygonatum verticillatum (L.) All. exhibited antioxidant activity, which is connected to the level of phenolic composition [126]. Singh and Yadav [127] have reported that, among medicinal plants, oregano, clove, thyme, and rosemary contain the highest amounts of phenolic compounds. Flavan-3-ol oligomers and monomers were potent antioxidant compounds abundantly identified in Camellia fangchengensis [128].

Bellis perennis L. was rich in phenolic compounds, and it can be used for wounds, cancer, inflammation, and eye diseases [129]. A total of 27 kinds of phenolic compounds were identified by HPLC-ESI-QTOF-MS/MS, and okra (Abelmoschus esculentus) polyphenols exhibited great antioxidant activity in vitro [130]. The Althaea officinalis extracts showed stronger antioxidant activity and excellent α-glucosidase, 5-lipoxygenase, and nitric oxide inhibitory properties [131]. Dendrobium densiflorum was rich in flavonoid, alkaloid, and antioxidant activity, Acampe papillosa was rich in total phenol, total tannin, and total saponin content, and Coelogyne nitida exhibited higher antioxidant activity because of its higher quercetin content [132]. Cirak et al. [133] showed that Achillea arabica Kotschy is an important source of natural antioxidants. The antioxidant property and bioactive constituents from the fruits of Aesculus indica (Wall. Ex Cambess.) Hook, which were quercetin and mandelic acid, were the major bioactive molecules with notable antioxidant properties to decrease oxidative stress caused by reactive oxygen species (ROS) [134]. The phytochemical compounds and biological activity of Pinus cembra L. contain higher concentration of total phenolics and flavonoids than that of needle extract, and its bark extract showed better ability as a free radical scavenger [135]. Higher antioxidant activity in normal-tannin lentil seed coats than low-tannin ones was reported; kaempferol tetraglycoside was dominant in low-tannin seed coats, and procyanidins, kaempferol tetraglycoise, and catechin-3-O-glucoside in normal-tannin has been found [136]. Zhang et al. [137] also reported that antioxidant activity and prebiotic impacts were positively correlated for oat phenolic compounds. 3,4-dihydroxybenzoic, rutin, vanillic acid, and quercetin were detected from aqueous extracts of azendjar and taamriouth figs, and a dark peel variety consisted of more phenolics and exerted a higher antioxidant capacity [138]. Although gallic acid was the most important compound in carob (Ceratonia siliqua L.) pulp extract, geographic origin strongly influenced the contents of bioactive compounds and antioxidant activities [139].

Asplenium nidus L. contained gliricidin 7-O-hexoside and quercetin-7-O-rutinoside that can fight against three pathogens, i.e., Proteus vulgaris Hauser, Proteus mirabilis Hauser, and Pseudomonas aeruginosa (Schroeter) Migula [140]. Flavones, which were extracted from the root of Scutellaria baicalensis Georgi, were proven as potential antibacterial agents against Propionibacterium acnes-induced skin inflammation both in in vitro and in vivo models [141]. Kaempferol that was isolated from the Impatiens balsamina L. exhibited potential activity to inhibit the growth of P. acnes [142]. Phenolics from kernel extract Mangifera indica L. also showed anti-acne properties to inhibit the growth of P. acnes [143]. Medicinal plants such as Albizia procera, Atalantia monophylla, Asclepias curassavica, Azima tetracantha, Cassia fistula, Costus speciosus, Cinnamomum verum, Nymphaea stellata, Osbeckia chinensis, Punica granatum, Piper argyrophyllum, Tinospora cordifolia, and Toddalia asiatica have shown antifungal activity [144]. The strictinin isolated from the leaves of Camellia sinensis var. assamica (J.W. Mast.) Kitam was a good substitute for antibacterial activities [145]. Phenolic compounds, especially flavonoids, have long been reported as chemopreventive factors in cancer therapy ^{[146][147][148]}[146,147,148]. The extract of Curcuma longa L. rhizome has been suggested as a promising source of natural active compounds to fight against malignant melanoma due to its potential anticancer property in the B164A5 murine melanoma cell line [149]. Glircidia 7-O-hexoside and Quercetin 7-O-rutinoside, which were flavonoids isolated from the medicine fern (Asplenium nidus), were also proposed as potential chemopreventives against human hepatoma HepG2 and human carcinoma HeLa cells [140]. Quercetin can induce miR-200b-3p to regulate the mode of self-renewing divisions of the tested pancreatic cancer [150], and a soy isoflavone genistein inhibited the activation of the nuclear factor kappa B (NF-KB) signaling pathway that maintains the balance of cell survival and apoptosis; this soy isoflavone could also take its action to fight against cell growth, apoptosis, and metastasis, including epigenetic modifications in prostate cancer [151]. Curcumin exhibits anticancer impacts towards skin cancers, as this phenolic can influence the cell cycle by acting as a pro-apoptotic agent [152]. Curcumin acts as a non-selective cyclic nucleotide phosphodiesterase (PDE) inhibitor to inhibit melanoma cell proliferation, which is associated with epigenetic integrator UHRF1 [153]. Curcumin inhibited proliferation of the selected cell lines in prostate cancer and induced apoptosis of the cancer cells with a dose-dependent response [154].

The cardioprotective impacts from various kinds of phenolics and flavonoids occurring in medicinal plants have been investigated in many studies ^[155][156][155,156]. Many phenolic and flavonoid compounds have been studied and had reported their cardioprotective properties via different mechanisms including inhibition of ROS generation, apoptosis, mitochondrial dysfunction, NF-KB, p53, and DNA damage both in vitro and in vivo, and clinical studies [157]. Kaempferol, luteolin, rutin, and resveratrol showed their efficacy against doxorubicin-induced cardiotoxicity ^[158][159][158,159]. Isorhamnetin provided a cardioprotective effect against cardiotoxicity of doxorubicin and potentiated the anticancer efficacy of this drug [160]. The total phenolic and flavonoid contents of the aqueous fraction from Marrubium vulgare L. have effects on ischemia-reperfusion injury of rat hearts, which proved that the aqueous fraction from M. vulgare had cardioprotective potential [156]. Aspalathin and phenylpyruvic acid-2-O-β-D-glucoside, two of the major compounds from Aspalathus linearis (Burm.f.) R. Dahlgren, were demonstrated as potential protective compounds to protect myocardial infarction caused by chronic hyperglycemia [155]. Puerarin is a potential isoflavone that was reported as an interesting candidate for cardioprotection by protecting myocardium from ischemia and reperfusion damage by means of opening the Ca²⁺-activated K⁺ channel and activating the protein kinase C [161]. Quercetin, hesperidin, apigenin, and luteolin were reported as flavonoids containing potential anti-inflammatory impacts [162]. The flavonoids and phenolic compounds of Phyllanthus acidus leaves could be correlated with the analgesic, antioxidant, and anti-inflammatory activities [163]. Hydroxytyrosol and quercetin 7-O-α-L-rhamnopyranoside exhibited anti-inflammatory activity through lowering the levels of TNF-α, and hydroxytyrosol and caffeic acid showed significant anti-inflammatory activity at 100 μm by reducing the release of NO in LPS-stimulated macrophages comparable to positive control indomethacin [164].

The most important chemical compounds extracted from ethanol of Cardiospermum halicacabum were chrysoeriol, kaempferol, apigenin, luteolin, methyl 3,4-dihydroxybenzoate, 4-hydroxybenzoic acid, quercetin, hydroquinone, protocatechuic acid, gallic acid, and indole 3-carboxylic acid, which have shown high anti-inflammatory and antioxidant activities [165]. The most important phenolic components with antiviral effects against COVID-19 were curcumin, Theaflavin-3,3′-digallate, EGCG, Paryriflavonol A, Resveratrol, Quercetin, Luteolin, Scutellarein, Myricetin, and Forsythoside A [166]. In traditional Persian medicinal science, medicinal plants such as Glycyrrhiza glabra L., Rheum palmatum L., Punica granatum L., and Nigella sativa L. have been introduced for treating respiratory disorders and infections because of their phenolic compounds [167]. The anti-inflammatory activity of polyphenolic compounds in Gaillardia grandiflora Hort. Ex Van Houte and Gaillardia pulchella Foug from Egypt were reported [168]. Anti-inflammatory properties of two medicinal plant species, Bidens engleri O.E. Schulz from Asteraceae family as well as Boerhavia erecta L. from Nyctaginaceae family, were identified and reported in various fractions [169]. Plantago subulata has shown anti-inflammatory properties on macrophages and a protective effect against H₂O₂ injury [170]. Phenolic content changes with aromatic and medicinal plant species and extraction method used [171]. Astilbin, a dihydroflavonol, from Smilax glabra Roxb significantly inhibited nitric oxide production, tumor necrosis factor-α (TNF-α), and mRNA expression of inducible nitric oxide synthase in the tested cells [172]. Apigenin is a main flavone with skin protective impact against UV light; this flavone can be identified in various edible medicinal plants or plants-derived beverages, e.g., beer, red wine, and chamomile tea ^[173][174][173,174]. Quercetin is a flavonol that can be discovered in apple peel, onion skin, and Hypericum perforatum L. leaves [175]. Silymarin, a standardized extract of flavonolignans from the milk thistle (Silybum marianum (L.) Gaernt.) fruits, consists of silybin, a principle active component [176]. Genistein is a soybean isoflavone that was also reported as photoprotective molecule against photocarcinogenesis by inhibiting UV-induced DNA damage in human skin-equivalent in vitro model [177]. Equol is considered as an isoflavonoid metabolite from isoflavone daidzein or genistein produced by gut microflora ^[178][179][178,179]. Genistein is an obvious example of an interesting choice of a flavonoid phytoestrogen for improving endothelial roles in postmenopausal women with MetS [180]. A chrysin derivative was the most abundant flavone in Cytisus multiflorus, quercetin-3-O-rutinoside was the main flavonol in Sambucus nigra, and kaempferol-3-O-rutinoside was the main flavonol in Malva sylvestris [181].