Journal of Food and Nutrition Research (ISSN 1336-8672) Vol. 55, 2016, No. 4, pp. 283–293
REVIEW
Review of the health benefits of Faba bean (Vicia faba L.) polyphenols
Imma Turco – Gianna Ferretti – Tiziana Bacchetti
Summary The dietary consumption of legumes is associated with a lower incidence of chronic degenerative diseases. Among legumes, a growing interest is devoted to Faba bean (Vicia faba L.), also known as broad bean. Faba bean nutritional properties have been previously studied and several polyphenols (mainly flavonoids) have been evaluated in broad bean extracts. In our study, the literature on polyphenol content in different varieties of Faba bean and on factors that modulate their levels was reviewed. Also, data on bioaccessibility and bioavailability of the main polyphenols contained in Faba bean were reviewed. The molecular mechanisms, antioxidant, anti-inflammatory and anti-diabetic properties, by which Faba bean polyphenols could be involved in the protection against the development of human diseases are described.
Keywords legumes; Faba bean; phytochemicals; nutrition; functional foods; polyphenols, flavonoids
Legumes have beneficial health implications significantly improve in vitro availability of iron related to their nutritional properties [1–5]. They and zinc [9, 10]. are an important source of macronutrients, con- Among legumes, a growing interest is devoted taining almost twice the amount of proteins com- to Faba bean (Vicia faba L.) for its positive nutri- pared to cereal grains. In addition, they are an tional properties [10–14]. Faba bean, commonly excellent source of dietary fibre, choline, lecithin, named broad bean, horse bean and field bean, be- folate and secondary metabolites such as polyphe- longs to the family of Fabaceae. It is one of the ma- nols, which exert many biological properties and jor winter-sown legume crops. It has an important have a key role in human health [1–5]. Legumes place in the traditional diets of the Mediterranean, are also a good source of different mineral ele- Indian, Chinese, English, Middle Eastern, African ments such as calcium, iron and zinc, however, and South American, and has considerable impor- their bioavailability is low [6]. The low bioavail- tance as a low-cost food rich in proteins and car- ability is related to phytochemicals such as phytic bohydrates [10–14]. Broad beans are harvested at acid and polyphenols [6–8]. The problem deserves vegetative stage when the pods and seeds are fresh attention among populations that derive minerals and green, and used as a vegetable. Alternatively, primarily from raw plant-based diets. However, re- they can be harvested at maturity stage after the cent studies demonstrated that different polyphe- pods and beans dry out. V. faba beans composition nols exert opposite effects on iron bioavailability (carbohydrates, fibres, proteins, vitamins and mi [7]. Moreover, various processing methods such nerals) and non-protein anti-nutritional factors as roasting, soaking, germination or fermentation (saponins, phytic acid alkaloids and tannins) was decrease the levels of anti-nutritional factors and previously studied [13–15]. Interestingly, in con-
Imma Turco, Gianna Ferretti, Department of Clinical Experimental Science and Odontostomatology, Polytechnic University of Marche, Via Ranieri 65, 60100 Ancona, Italy. Tiziana Bacchetti, Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Ranieri 65, 60100 Ancona, Italy. Correspondence author: Gianna Ferretti, e-mail: [email protected]; tel.: +39-071-220-4968
© 2016 National Agricultural and Food Centre (Slovakia) 283 Turco, I. – Ferretti, G. – Bacchetti, T. J. Food Nutr. Res., Vol. 55, 2016, pp. 283–293 trast to cereals, Faba bean was found to contain by starch (410–530 g·kg-1). Lipids are contained high levels of lysine and arginine, which may com- at 12–40 g·kg-1. Dietary fibre ranges between plement the low levels of those in cereals. 150 g·kg-1 and 300 g·kg-1, which depends on the For the first time, in 1913, Guggenheim identi- seed variety, hemicellulose being the major com- fied l-3,4-dihydroxyphenylalanine (l-DOPA) [16], ponent [10–13]. the precursor of dopamine, in the seedlings, pods and beans of V. faba. More recently, a potential Micronutrients role of V. faba intake in management of Parkin- Vitamin C son disease has been suggested [17, 18]. However, The effect of processing on vitamin C has been more research is necessary to determine the role studied in different varieties by Kmiecik et al [25]. of Faba beans in Parkinson’s disease. The vitamin C content decreased with increasing Broad beans also contain alkaloids that should degree of seed ripeness in the range from 25 % be taken into account for certain people suffer- to 40 %. Blanching decreased the vitamin C con- ing from favism, an inherited disease in which tent by 14–43 %. Freezing of blanched seeds and the enzyme glucose-6-phosphate dehydrogenase a 6-month storage of frozen goods decreased (G6PD) is deficient [19]. Vicine and convicine are the vitamin content by approximately 24–56%. natural pyrimidine glucosides found in the Faba Frozen whole seeds contained 93–138 mg·kg-1 bean plant and are likely to be involved in plant of vitamin C after cooking (compared with fresh defense mechanisms against pathogens. The agly- seeds, the losses reached 56–73 %) and appertized cone derivatives, divicine and isouramil, are re- canned seeds contained 82–117 mg·kg-1 (compared sponsible for favism occurrence [19]. Some com- with fresh seeds, the losses reached 63–73 %). mon treatments induce modifications of alkaloids content and l-DOPA in Faba beans [20, 21]. Folate The role of Faba bean as a source of protein Faba beans are also a source of folate. Indus- in human diet and the role of non-nutritional fac- trial food processing (e.g., canning or freezing), tors (saponins, lectins, tannins, phytic acid) which germination, cultivar, and maturity stage modu- modulate nutrient bioavailability was recently re- late the folate content [26]. The folate content in viewed [15]. Recent papers suggest that Faba bean four cultivars of green Faba beans ranged from and derivatives could represent a suitable food 1.1–1.3 mg·kg‑1 fresh weight, which was four- to in treatment of diabetics, in hypertension and six fold higher than in dried seeds [26]. Industrial may help to prevent cardiovascular disease [22]. canning of dried seeds resulted in significant folate Among bioactive molecules involved in the mo- losses of approximately 20 %, while industrial lecular mechanisms, which contribute to preven- freezing had no effect [26]. Germination of Faba tion of chronic-degenerative disease, a key role beans increased the folate content by > 40 % [26]. is exerted by plant polyphenols [1, 23, 24]. This is the first review on Faba bean nutritional proper- Carotenoids and tocopherols ties with particular attention to its polyphenols Grain legumes are included among the dietary and their potential protective effect against the sources of carotenoids (including provitamin A) development of human diseases. Therefore, the and tocopherols (vitamin E), which play pivotal literature on polyphenol content in different va- roles in the prevention of inflammatory process- rieties of Faba bean and on factors that modulate es, as well as coronary, neuromuscular and visual their levels was reviewed. Also, data on polyphe- disorders. Fernández-Marín et al. [27] demon- nol bioaccessibility and bioavailability, as well as strated that domestication of grain legumes was on molecular mechanisms by which polyphenols accompanied with a reduction in carotenoids con- could be involved in the protection against the de- tents. velopment of human diseases were reviewed. Polyphenols Polyphenol content Faba bean composition Among phytochemicals, phenolic compounds are gaining an increasing interest for their health- Macronutrients and dietary fibres promoting properties [23, 24, 28]. They are widely The protein content of Faba bean seeds distributed in fruits, vegetables and beverages ranges from 200 g·kg-1 to 410 g·kg-1, which de- (tea, coffee, wine) [23, 24, 28, 29]. All polyphenols pends on the variety. Faba bean seeds contain contain one or more aromatic rings with one or 510 g·kg-1 to 680 g·kg-1 of carbohydrates in to- more hydroxyl group as substituents. Depending tal, the major proportion of which is constituted on the number of these phenol rings and on the
284 Review of the health benefits of Faba bean (Vicia faba L.) polyphenols structural elements bound to them, polyphenols gallocatechin and catechin), proanthocyanidins are classified into different groups [28]. Polyphe- (prodelphynidins and procyanidins), flavonols nols in Faba beans are located in several parts of (glycosylated derivates of myricetin, quercetin and the plant (e.g. leaves, roots and seeds) [30, 31]. kaempferol), flavanonols, isoflavones (genistein Faba bean cotyledons have higher contents than and daidzein) and flavanones. Moreover, other their respective hulls or whole seeds [32]. Previous phenolic compounds were found in Faba beans, studies provided data mainly the levels of total including phenolic acids (caffeic acid, ferulic acid, polyphenols, total flavonoids and total tannins p-coumaric acid and synaptic acid) [36–38]. The in seeds of different Faba bean varieties [31–35]. contents of individual phenolic compounds in As summarized in Tab. 1, a large variability of Faba bean samples are shown in Tab. 3. the levels of total polyphenols in seeds of differ- In addition to genetic factors, total phenolic ent varieties has been observed. The comparison content in seeds is modulated by other factors of polyphenol levels of extracts obtained using dif- such as growing stage (vegetative, reproductive ferent solvents demonstrated that ethanol extracts and mature). Immature Faba bean fractions have contained higher levels of polyphenols compared significantly higher phytochemical contents and with extracts obtained using acetone [32]. display a better antioxidant activity than those of Recently, Abu-Reidah et al. [36] identified mature ones [34, 39]. a total of 104 phenolics, mainly flavonoids in Faba beans. The main classes are shown in Tab. 2. Fla- Effect of processing on polyphenol levels vonoid compounds found in Faba beans, include Faba beans can be consumed fresh or after flavanol monomers (such as gallocatechin, epipa- cooking. Their polyphenol profiles are affected
Tab. 1. Levels of total polyphenols in seeds of different Faba bean varieties.
Total Total Variety Country polyphenols Extraction Variety Country polyphenols Extraction [mg·kg-1] [mg·kg-1] Subspecies Vicia Algeria 9 530 A G4 Tunisia 35 170 B major [32] 30 930 B G5 [34] 27 840 B Subspecies Vicia 4 490 A G6 25 630 B minor 42 440 B G7 30 200 B TF(Ic*As)*483/13 Australia 2 800 A G8 24 460 B Doza [33] 8 600 A G9 16 980 B Nura 10 900 A G10 38 100 B Icarus 10 800 A G11 45 590 B Rossa 11 200 A G12 43 930 B 5%LSD 500 A G13 41 050 B Super Aguadulce Chile 1 060 C G14 67 470 B Agrical [31] AO155 Canada 30 940 * B Super Aguadulce 1 180 C AZ10 [35] 34 990 * B Anasac Disco 5 590 * B Portuguesa INIA 1 140 C Divine 6 180 * B Luz de Otono 820 C Fatima 31 770 * B Reina Mora 1 320 C FB25-56 40 630 * B Alargà 1 340 C Florent 30 920 * B Retaca 940 C Imposa 37 780 * B Verde Bonita 1 010 C Melodie 6 170 * B HBP/SO A/2005 1 100 C NPZ4-7540 35 330 * B HBP/SO B/2005 1 110 C Snowbird 37 760 * B G1 Tunisia 21 480 B SSNS-1 36 740 * B G3 [34] 28 650 B Taboar 36 060 * B Data are presented as milligrams of gallic acid equivalent per kilogram of Faba bean seeds on dry matter basis (* – data are presented as milligrams of catechin equivalent per kilogram of Faba bean seeds on dry matter basis). Solvent used to prepare extracts: A – acetone/water, B – ethanol, C – methanol/water.
285 Turco, I. – Ferretti, G. – Bacchetti, T. J. Food Nutr. Res., Vol. 55, 2016, pp. 283–293
Tab. 2. Phenolic compounds characterized in Vicia faba L. seeds extract [36]. Class Compounds Flavanol monomers gallocatechin, (epi)gallocatechin, (epi)gallocatechin hexose I, (epi)gallocatechin dihexoside, catechin, epicatechin, (epi)catechin di-C-glucoside, (epi)afzelechin, 4’- or 5’-O-methyl-(epi)catechin I Prodelphynidins (epi)gallocatechin-(epi)gallocatechin I, (epi)gallocatechin-(epi)gallocatechin II, (epi)gallocatechin-(epi) gallocatechin III, (epi)gallocatechin-(epi)gallocatechin IV, (epi)gallocatechin-(epi)catechin I, (epi)gallo catechin-(epi)catechin II, (epi)gallocatechin-(epi)catechin III, (epi)gallocatechin-(epi)gallocatechin V, (epi)catechin-(epi)gallocatechin II, (epi)gallocatechin-(epi)gallocatechin VI, (epi)catechin-(epi)gallocate- chin III, (epi)catechin-(epi)gallocatechin IV, (epi)gallocatechin-(epi)gallocatechin VII, (epi)gallocatechin- (epi)gallocatechin VII, (epi)catechin-(epi)gallocatechin VI Procyanidin (epi)catechin-(epi)catechin(procyanidin B I), (epi)catechin-(epi)catechin II (procyanidin B II), (epi) catechin-(epi)catechin II (procyanidin B III), (epi)catechin-(epi)catechin II (procyanidin B IV) Phenolic acid salicylic acid O-glucoside, protocatechuic acid hexoside, 3’-O-methyl(3’,4’-dihydroxybenzyl tartaric acid)(3’-O-methylfukiic acid), hydroxyeucomic acid, hydroxybenzyl-malic acid (eucomic acid) Flavanone naringenin 7-glucoside (prunin), dihydrochrysin (pinocembrin) Flavone isoschaftoside, apigenin 8-or-6-C-glucoside (vitexin or isovitexin)
Flavonol myricetin hexose I, quercetin hexose deoxyexose II, kaempferol3-O-α-l-arabinopyranosyl-7-O-α-l- rhamnopyranoside, myricetin hexose III
Stilbene resveratrol, resveratrol 3-O-ß-d-glucoside Dihydrochalcone phloretin 3’,5’-di-C-glucoside Isoflavone genistein, formonetin, daidzein
by processing such as soaking, sprouting, freez- Boiling was shown to be a better method than ing, boiling, pressure cooking and steaming [33, autoclaving in retaining phenolic compounds, and 40–42]. Roasting Faba beans for 120 min de- the authors suggested that home-cooked Faba creased the total phenolic, flavonoid and proan- beans may contain higher levels of phenolic com- thocyanidin contents by 42 %, 42 % and 30 %, pounds than industrially processed Faba beans respectively, but also caused generation of new [33]. Even sprouting, a process involving germi- phenolic compounds [40]. Soaking, boiling and nation and drying of legume seeds, was found to autoclaving caused loss in phenolic compounds decrease total polyphenol content and was associ- and antioxidant activities due to leaching of com- ated with improvements in the nutritive value in pounds into the soaking and cooking medium. sprouted seeds [10]. A significant decrease in tan- nin content was also observed in irradiated Faba beans [43]. Due to the aforementioned inhibitory Tab. 3. Contents of individual polyphenols effect of tannins and other anti-nutritional factors in Vicia faba seeds. on mineral bioavailability, all the treatments sig- Polyphenol nificantly improved in vitro availability of minerals Polyphenols level Reference [9]. [mg·kg-1] (+)-Catechin 84–978 [31] (–)-Epicatechin 140–700 [31] Bioactive roles of Faba bean polyphenols Total flavonols + flavones 100–370 [31] The biological activities of Faba bean polyphe- Proanthocianidins 542–3 363 [31] nols was recently evaluated using different experi- Total phenolic acids 156 ± 13.3 [37] mental models. Faba bean polyphenols behave as Caffeic acid 7.8 ± 0.3 [37] antioxidants and modulate other cell functions p-coumaric acid 16.8 ± 0.7 [37] with an interesting potential for various fields of Sinapic acid 25.8 ± 2.3 [37] medicine.
Ferulic acid 105.6 ± 15.8 [37] Antioxidant properties Total isoflavone 24.9 [38] Antioxidant activity and scavenging properties Daidzein 5 [38] A wide variety of antioxidants, such as vita- Genistein 19.9 [38] mins C, vitamin E, carotenoids, terpenoids and
286 Review of the health benefits of Faba bean (Vicia faba L.) polyphenols polyphenols, contribute to the antioxidant capacity bean extracts against peroxyl radical-induced of plant foods [28]. The antioxidant capacity of DNA strand scission was observed using peroxyl extracts from Faba bean was widely investigated free radicals (ROOH) produced from thermal de- using different methodological approaches such as composition of 2,2’-azobis(2-amidinopropane hy- ferric-reducing antioxidant power assay (FRAP), drochloride) (AAPH) on Bluescript-SK+ plasmid oxygen radical absorbance capacity (ORAC), de- DNA. A protective effect was exerted also against termination of the scavenging effect on 2,2-diphe- hydroxyl radical-induced DNA strand scission nyl-1-picrylhydrazyl (DPPH) radicals and by generated by UV photolysis of hydrogen peroxide evaluation of total equivalent antioxidant capacity (H2O2) [45]. ROO• radicals comprise one of the (TEAC). major factors initiating the cascade reactions of The antioxidant properties of extracts of Faba lipid peroxidation [46], therefore, it is possible to beans are related to total phenolics and total fla- suggest that Faba bean polyphenols may prevent vonoids contents. Differences were observed for lipid peroxidation. It was hypothesized that the different genotypes collected during three dif- protective activity of Faba bean extracts against ferent growing stages (vegetative, reproductive hydroxyl radical-induced DNA damage may be and mature) [39]. The results showed also differ- due to their ability to prevent the reaction of hy- ent antioxidant properties for the same genotype droxyl radical with hydrogen atoms at C3’, C4’ and when considering the different parts of the plant. C5’ sites of the sugar moiety of DNA [45]. Higher contents of total phenolics and flavonoids were found during vegetative and reproductive Inhibition of enzyme activities stages, which also showed the highest antioxidant The enzymes whose activity is inhibited by activity (FRAP values ≥ 1.157 mol·kg-1) and the polyphenols obtained from Faba beans are shown highest DPPH radical-scavenging capacity. Using in Tab. 4. an ORAC assay, it was reported that the anti- oxidant capacity ranged from 109 mmol·kg-1 to Angiotensin-converting enzyme 149 mmol·kg-1, expressed as Trolox equivalents. Siah et al. [43] demonstrated that polyphe- The effects of food processing on DPPH radi- nols of three Australian-grown Faba beans geno- cal-scavenging activity, TEAC, ORAC and FRAP types (Nura, Rossa and TF(Ic*As)*483/13 variety) of Faba bean genotypes were studied [33, 40]. exerted inhibitory effects on angiotensin-convert- A significant loss of phenolic compounds after ing enzyme (ACE), a key blood pressure regulator, soaking, boiling, autoclaving and roasting correlat- which is responsible for vasoconstriction that leads ed with the decrease of antioxidant capacities [33, to an increase in blood pressure [47]. Extracts 39, 40–42]. from Nura variety exhibited the greatest ACE in- hibitory activity both in raw and roasted beans, Protective effect against free-radical-mediated followed by extracts from Rossa variety. Roasting damage to DNA treatment reduced significantly ACE inhibitory Various chemical agents cause DNA single- activity. The decrease was related to roasting-in- strand breaks [44]. A protective effect of Faba duced decrease of polyphenol content [43]. Inhi-
Tab. 4. Molecular mechanisms by which Faba bean polyphenols could exert a protective role against the development of human diseases. Protective role Molecular mechanism Protective effect against Antioxidant effect oxidative stress Scavenging properties Inhibition of peroxyl radicals–triggered damage to DNA Inhibition of the enzyme 15-lipoxigenase Inhibition of the enzyme xanthine oxidase Antihypertensive effect Inhibition of angiotensin-converting enzyme (ACE) Chemopreventive effect Inhibition of topoisomerase I Regulation of proliferation and apoptosis Antidiabetic properties Inhibition of the enzyme α-glucosidase Inhibition of protein glycation (triggered by glucose or methylglyoxal) Modulation of production of receptors for advanced glycation end-products in endothelial cells.
287 Turco, I. – Ferretti, G. – Bacchetti, T. J. Food Nutr. Res., Vol. 55, 2016, pp. 283–293 bition of ACE activity can potentially prevent the of atherosclerosis, participating in oxidative modi- enzyme ACE from elevating blood pressure, re- fications of low-density lipoproteins (LDL) [51] ducing the incidence of hypertension. The ethanol hull extracts inhibited 15-LOX in the order V. minor > V. major. Literature data suggest α-Glucosidase and lipase that the effect could be mediated by flavonoid Faba bean polyphenols inhibit also the en- compounds [32]. zymes α-glucosidase and lipase [43], which are important in the digestive tract, being responsible Tyrosinase for carbohydrate and lipid digestion. Inhibition Recently, it was reported that edible beans of α-glucosidase activity could potentially reduce have tyrosinase inhibitory activities [52]. It has starch digestion and sugar absorption, contribut- been shown that broad bean extract exerts a tyro- ing to a lower postprandial glycemic response. sinase inhibition activity that is significantly corre- Therefore, α-glucosidase has been recognized as lated with total phenols and antioxidant capacity a therapeutic target for modulation of postpran evaluated using DPPH assay. Acting as a key en- dial hyperglycaemia. The inhibition of lipase ac- zyme for synthesis of melanin pigments, tyrosinase tivity could reduce fat uptake. Among extracts catalyses two distinct reactions in melanin synthe- obtained from both raw and roasted beans, the sis, namely, hydroxylation of l-tyrosine to l-DOPA variety Rossa exhibited the highest α-glucosidase and oxidation of l-DOPA to dopaquinone, while inhibiory activity, followed by Nura variety [43]. from the latter compound, after further series of Roasting was found to decrease the level of conversions, melanin is produced [53]. Inhibitors α-glucosidase inhibitory activity of both genotypes. of tyrosinase have been used to treat some derma- The decrease of inhibition of α-glucosidase in tological hyperpigmentation illness connected with roasted beans was not related to roasting-induced overproduction of melanin. decrease of polyphenol content [43]. Regarding molecular mechanisms involved in the inhibition of the enzymes, formation of proanthocyanidin- Chemopreventive effect, regulation enzyme complexes was proposed [43]. of cell proliferation and apoptosis
Xanthine oxidase Previous studies suggested that polyphenols Xanthine oxidase (XO), the enzyme which also modulate cell signaling and could behave as participates in purine degradation, is the main potential anticancer agents [28, 29]. In the past contributor of free radicals during exercise [48]. few years, polyphenol antioxidant capacity has It uses molecular oxygen as the electron acceptor, been taken into account as one of the outstand- thereby resulting in production of superoxide radi- ing mechanisms of action to inhibit mutagenesis – cal (O2 •) and hydrogen peroxide (H2O2) [42]. XO and cancer initiation, by means of their capacity to is also involved in pathogenesis of several diseases scavenge reactive oxygen species (ROS), activate such as vascular disorders, diabetes, cancer and antioxidant enzymes, prevent carcinogen-induced gout [49]. Spanou et al. [50] demonstrated that ex- DNA adduct formation, enhance DNA repair tracts of Faba beans behaved as potent inhibitors and reduce overall oxidative DNA injury [28, 29, of XO. The concentrations of extracted compound 54]. Oxidative stress, peroxyl radicals and lipid mixtures required to give 50% inhibition (IC50) of peroxidation products can independently cause XO activity ranged from 40 µg·ml-1 to 135 µg·ml-1 mutations in DNA, which are known to be cru- [50]. The compunds identified as XO inhibitors cial for the initiation of the carcinogenic process were flavonoids (mainly quercetin and kaemp- [54]. As aforementioned, Faba bean fractions ex- ferol glycosides) and a structure-related inhibi- hibit a radical-scavenging capacity and protec- tory activity was demonstrated. The most potent tive ability against free radical-induced DNA inhibitor of XO in Faba bean extracts was kaemp- damage. They exert also an inhibitory role regard- ferol 3-O-(5-O-acetyl-β-d-apiofuranosyl)-7-O-α-l- ing topoisomerase I [43]. Topoisomerase I is one rhamnopyranoside [50]. of the enzymes playing a crucial role in replica- tion, transcription, recombination, chromosome 15-Lipoxigenase condensation and maintenance of genome stabil- Anti-inflammatory activity of ethanol hull ex- ity [55]. Because it is an essential enzyme for vital tracts from two Faba bean subspecies, Vicia major functions of DNA during normal cell growth, in- and Vicia minor, was evaluated testing the inhibi- hibitors of its activity are considered to be promis- tion of the enzyme 15-lipoxigenase (15-LOX) [32]. ing anticancer agents [55]. 15-LOX is involved in the molecular mechanisms The ability of Faba bean extracts to inhibit
288 Review of the health benefits of Faba bean (Vicia faba L.) polyphenols proliferation of different human cancer cell lines Bioavailability of Faba bean polyphenols (BL13, AGS, Hep G2 and HT-29) was observed in humans by Siah et al. [43]. Faba beans extracts, applied at a concentration range of 0.2–2.0 mg·ml-1, exhib- To exert their health effects, dietary polyphe- ited a dose-dependent suppression of prolifera- nols should be bioavailable. Concentrations and tion of all of the tested human cancer cells, while solubility of polyphenols modulate their bioavail- exhibiting a negligible anti-proliferation effect on ability. Moreover, their bioavailability depends the non-trasformed human colon CCD-18Co cells. on their release from the food matrix, which is re- Flow cytometric analyses showed that Faba bean ferred to as bioaccessibility [60–62]. On oral con- extracts successfully induced apoptosis of HL-60 sumption, the uptake of polyphenols into the body (acute promyelocytic leukaemia) cells [43]. is not complete, and a certain percentage is not absorbed [60–62]. It was suggested that the gas- Modulation of protein glycation and formation tro-intestinal tract may act as an extractor where of advanced glycation end-products polyphenols are progressively released from the Advanced glycation end-products (AGE) have solid matrix and made available for the absorption a role in the molecular mechanisms of diabetic or to exert their biological effects in the gastro- complications including neuropathy, nephropa- intestinal tract [60–62]. Prerequisites for polyphe- thy, retinopathy, atherosclerosis and cataracts nols to have any in vivo systemic effects are that [56]. Thus, the discovery and investigation of they must be absorbed from the gastrointestinal AGE inhibitors would offer a potential therapeu- tract after food consumption and, subsequently, tic approach for the prevention of diabetic com- reach sufficiently high plasma concentrations in plications. Yang Yao et al. [37] demonstrated the systemic circulation to induce biological activ- that Faba bean extracts inhibit glycation of bo- ity. Several studies evaluated bioaccessibility and vine serum albumin (BSA) triggered by glucose bioavailability of legume polyphenols in vitro and or methylglyoxal (MGO), and formation of AGE in vivo [60–64]. [37]. The authors demonstrated that inhibition of Among flavonoids contained in Faba bean, glycation of BSA significantly correlated with total there are isoflavones. They have structural similar- phenols [37]. ities to estrogens including the ability to bind to es- trogen receptors, and they are consequently clas- Modulation of esRAGE production sified as phytoestrogens. Previous studies showed on glucose-treated endothelial cells that genistein and its glycoside genistin, either as Receptors for advanced glycation end-products pure compounds or from a soy protein isolate ex- (RAGE) are members of the immunoglobulin su- tract, are bioavailable. Genistin is partly absorbed perfamily and multiligand receptors for the late in its glycosidic form. Both intestine and liver are products of non-enzymatic glycation AGE [57]. involved in deglycosylation and uptake of these RAGE is also known to be involved in microvas- glycosylated flavonoids. Human studies showed cular complications in diabetes through oxidative that also daidzein is bioavailable. Both isoflavones stress generation, regulation of atherogenesis, the are recovered in urine samples. It was suggested angiogenic response, and vascular injury [57]. Hu- that plasma concentrations of daidzein and genis- man vascular cells express an endogenous secre- ten may be sufficient to exert some health-protec- tory receptor for advanced glycation end-products tive effects [64]. called esRAGE. These neutralize AGE action on Faba beans are also a source of proanthocyani- endothelial cells. Therefore, RAGE antagonists dins, also known as condensed tannins. The proan- are in clinical development as therapeutics for thocyanidins found in food cover a wide range of diabetes complications. Okada et al. [58] showed degree of polymerization (DP). Most of them pass that methanolic extracts from Faba bean and unaltered to the large intestine where they are ca other plant foods have a modulatory role regard- tabolized by the colonic microflora yielding a di- ing esRAGE production potential on glucose- versity of phenolic acids, which are absorbed into treated endothelial cells [58]. It was suggested the circulatory system and excreted in urine [65, that polyphenols of methanol extracts, in particu- 66]. However, recent studies suggest that only the lar quercetin, could be involved in the bioactive low-molecular-weight oligomers (DP < 3) are ab- effect. The results could have a physiopathological sorbed intact in the gastrointestinal tract [65, 66]. relevance because the interference with the activa- Flavonols are the most ubiquitous flavonoids in tion of RAGE was shown to prevent or ameliorate foods, with main representatives being myricetin, vascular complications in experimental studies quercetin and kaempferol [67]. The bioavailabil- [59]. ity of flavonols, in particular quercetin, has been
289 Turco, I. – Ferretti, G. – Bacchetti, T. J. Food Nutr. Res., Vol. 55, 2016, pp. 283–293 widely investigated in fruits and vegetables. Litera- beans represent a useful source of bioactive mo ture data indicate that, after ingestion, quercetin lecules and their intake contributes to prevention glycosides are metabolized, absorbed and circulate of chronic degenerative diseases. in the blood as types of conjugates [68]. Faba beans contain also phenolic acids. Previous studies demonstrated that phenolic acids References are bioavailable. When they are in aglycone form, they are generally absorbed in the upper part of 1. Rochfort, S. – Panozzo, J.: Phytochemicals for health, the gastro-intestinal tract. Gallic, caffeic, ferulic, the role of pulses. Journal of Agricultural and Food coumaric acids but also chlorogenic acid can be Chemistry, 55, 2007, pp. 7981–7994. DOI: 10.1021/ absorbed from the stomach [69]. jf071704w. 2. Bouchenak, M. – Lamri-Senhadji, M.: Nutritional quality of legumes, and their role in cardiometabolic risk prevention: A review. Journal of Medicinal Food, Conclusions 16, 2013, pp. 185–198. DOI: 10.1089/jmf.2011.0238. 3. Ofuya, Z. M. – Akhidue, V.: The role of pulses in Plant-based diets and an increase in legume human nutrition: A review. Journal of Applied intake exert health benefits. Several studies have Science and Environmental Management, 9, 2005, shown that the prevention of diabetes, cardio- pp. 99–104. ISSN: 1119-8362.
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