Smallanthus Sonchifolius and Lepidium Meyenii – Prospective Andean Crops for the Prevention of Chronic Diseases

Smallanthus sonchifolius (yacon) and Lepidium meyenii (maca) were the traditional crops of the original population of Peru where they are also still used in folk medicine. These plants are little known in Europe and Northern America although at least yacon can be cultivated in the climatic conditions of these regions. This article deals with the botany and the composition, the structure of main constituents, biological activity of these plants and the cultivation of yacon in the Czech Republic. The potential of yacon tubers to treat hyperglycemia, kidney problems and for skin rejuvenation and the antihyperglycemic and cytoprotective activity of its leaves seems to be related mostly to its oligofructan and phenolic content, respectively. Maca alkaloids, steroids, glucosinolates, isothicyanates and macamides are probably responsible for its aptitude to act as a fertility enhancer, aphrodisiac, adaptogen, immunostimulant, anabolic and to influence hormonal balance. Yacon and maca are already on the European market as prospective functional foods and dietary supplements, mainly for use in certain risk groups of the population, e.g. seniors, diabetics, postmenopausal women etc. INTRODUCTION An optimal diet is frequently a good preventive measure against chronic diseases. Classic examples abound in the use of diet in the control of blood cholesterol levels, blood glucose level regulation and control, arteriosclerosis and diabetes risk factor lowering, dietary substitution of estrogenic hormones in menopause, influence on osteo-arthritis development, osteoporosis and digestive tract cancer, amelioration of some neurological illnesses, improvement of impaired immunity and lowering of food contaminant toxic effects. Plant products that have positive physiological effects on the human organism can be classified as follows: (i) functional foods and (ii) dietary supplements (nutraceuticals), that is, concentrated, chemically characterised and standardised mixtures of compounds originating from plants, e.g. plant extracts. In all food products with demonstrable physiological effects, there is a specific group of compounds responsible, these include biogenic elements, flavonoids, phytosterols, poly-saccharides including fiber, β-D-glucans, polyunsaturated fatty acids and other components with positive physiological activity. The health status of people in developed countries is becoming so alarming, that market expansion in preventive , inexpensive, physiologically effective and safe functional foods and dietary supplements for risk groups of the population including the elderly is desirable. Of these foods, most traditional Andean crops, apart from potatoes and maize are practically unknown in Europe despite the fact that they served for centuries to enable native populations to survive severe climatic conditions 1. Tuber and root crops are …


INTRODUCTION
An optimal diet is frequently a good preventive measure against chronic diseases.Classic examples abound in the use of diet in the control of blood cholesterol levels, blood glucose level regulation and control, arteriosclerosis and diabetes risk factor lowering, dietary substitution of estrogenic hormones in menopause, influence on osteoarthritis development, osteoporosis and digestive tract cancer, amelioration of some neurological illnesses, improvement of impaired immunity and lowering of food contaminant toxic effects.Plant products that have positive physiological effects on the human organism can be classified as follows: (i) functional foods and (ii) dietary supplements (nutraceuticals), that is, concentrated, chemically characterised and standardised mixtures of compounds originating from plants, e.g.plant extracts.In all food products with demonstrable physiological effects, there is a specific group of compounds responsible, these include biogenic elements, flavonoids, phytosterols, polysaccharides including fiber, β-D-glucans, polyunsaturated fatty acids and other components with positive physiological activity.
The health status of people in developed countries is becoming so alarming, that market expansion in preventive, inexpensive, physiologically effective and safe functional foods and dietary supplements for risk groups of the population including the elderly is desirable.Of these foods, most traditional Andean crops, apart from potatoes and maize are practically unknown in Europe despite the fact that they served for centuries to enable native popu-lations to survive severe climatic conditions 1 .Tuber and root crops are predominantly cultivated in the Andes: these include several potato varieties, Solanum tuberosum, S. andigenum, S. ajanhuiri, S. stenotomum, S. goniocalyx, S. phureja 2 (Solanaceae), also ahipa (Pachyrhizus ahipa, Leguminosae), arracacha (Arracacia xanthorrhiza, Apiaceae), mashua or añu (Tropaeolum tuberosum, Tropaeolaceae), sweet potato (Ipomoea batata, Convolvulaceae), mauka (Mirabilis expansa, Nyctaginaceae) 3 yacon (Smallanthus sonchifolius) 4 and maca (Lepidium meyenii) 5,6 .This review focuses on the two last crops, yacon and maca.The former can be successfully cultivated in the European climate.Yacon (S. sonchifolius, Asteraceae (Compositae)) is a Jerusalem artichoke (Helianthus tuberosus) related plant.Maca (L.meyenii, Brassicaceae (Cruciferae)) is related to watercress (L.sativum) and among ethnopharmacologists known as Peruvian ginseng.

BOTANY AND HISTORY
Yacon and related plants were originally classified under the genus Polymnia (Asteraceae, Heliantheae, Melampodinae) 4,[7][8][9] , although the genus Smallanthus (Asteraceae, Heliantheae), rediscovered by Robinson 10 in 1978 along with 21 other species, had already been proposed in 1933.The new classification, Smallanthus sonchifolius (Poepp.& Endl.), is currently preferred while the old name Polymnia sonchifolia Poepp.& Endl. is considered as synonymous 4,11 .The name Polymnia edulis also appears in the literature 11 .Yacon is a perennial plant forming a clump of more then twenty 12,13 big underground tubers weighing from 100-500 g, exceptionally more than one kilogram.These resemble dahlia tubers 9 .Their shape and size depend on the particular clone, but in most cases the tubers are irregularly spindle-shaped, sometimes almost round-shaped.They are edible and colourless if freshly harvested.The epidermis becomes rapidly dark after exposure to air.Under the epidermis, cortex tissue with a slightly resinous taste is found and under this, mild yellowish flesh with a fruit taste 6 .The whole plant is much less resistant to frost than the Dahlia which is why its cultivation is limited to a much shorter period in European climates compared to its country of origin 6 .Apart from tuberous roots, yacon also forms short caudices, growing directly on the basal part of the main stem.These are usually used for the vegetative propagation of yacon (generative reproduction capability was lost during evolution 4 ).Yacon propagation through tissue leaf culture is currently studied 14 .The stem can reach 2 m in height; it is densely foliaged with dark green leaves and covered by violet-coloured trichomes.The inflorescence is small, about 30 mm in diameter, with a yellow or orange colour.It grows at the top of the main stem and also on other stems growing from lower nodal buds.Flower production is quite limited in yacon, more so than in barren Smallanthus species.The fruits are black, about 2 mm small achenes.The somatic chromosome number has been found 15 to be 2n = 60 and this is in accordance with the cytological analysis of our clone material.In early evolutionary periods, Andean farmers had already recognized the properties of yacon and had transformed the plant into a cultivated crop.Yacon is found in burial grounds from centuries before the Incas 2 .The oldest yacon representation on textile and ceramics has been found in a littoral archaeological deposit Nazca (500-1200 A.C.) 4 .The first written allusion on yacon comes from the chronicler Padre Bernabé Cobo 12 (1653).In the Andes, yacon is cultivated at altitudes of 880 to 3500 m.Its cultivation extends from Venezuela to northwestern Argentina 12 .In most cases, just a few plants are cultivated for family consumption 4 .From the Andes, yacon was transferred in the 80'ies of the 20 th century through the New Zealand to Japan 6 .Its cultivation was successfully introduced into Italy, Germany, France and USA though yacon is still not remarkably diffused there.In Italy, yacon tubers are used to produce alcohol and inulin 12 .In 1993, it was introduced into the Czech Republic in the form of caudices originating from New Zealand 6 .More recently, it has also been introduced into Russia 16,17 .
The genus Lepidium belongs to the family Brassicaceae (Cruciferae) like other important crops such as, e.g.rape, cabbage, head cabbage, radish, garden cress or mustard; members of this genus are distributed throughout all continents 5 .The genus probably originates in the Mediterranean basin; long-distance dispersal during the late Tertiary and Quaternary period was probably responsible for the colonization of these species to the Americas and Aus-tralia.The genus consists of approximately 175 species; some of them are cultivated, e.g.garden cress (L.sativum).Maca (L.meyenii Walp.syn.L. peruvianum Chacón, reviews 6,18,19 ) is cultivated over the whole of South America as a starch crop.L. peruvianum Chacón is found exclusively in Peru 20,21 .The aerial part of L. meyenii forms a rosette of 12-20 leaves like in radish, but the foliage forms a mat, growing in close contact with the soil.The main stem is reduced while the underground part is a storage organ resembling turnip 1,20 .For simplicity, we will call this organ, formed by the taproot and the lower part of the hypocotyl, just "hypocotyl".This is the economic product of maca.The hypocotyls display a variety of colours from purple to cream and yellow (the Peruvians distinguish 4 cultivars, cream, purple, red and black 1,22 ).They are about 10-14 cm in length and 3-5 cm in width, with a solid consistency 20 .Maca is an annual crop completing its life cycle within a year when climatic conditions are favourable.The seeds, its only means of propagation, have no dormancy, germinating in 5-7 days at 25 °C under good moisture conditions.A single plant of maca produces approximately 14 g of seeds 5 .It is probably an autogamous species.The basic genomic chromosome number in Lepidium is x = 8.Maca is an octoploid with 2n = 8x = 64 chromosomes 21 .The direct ancestor of L. meyenii are unknown, but they are none of the three main wild Lepidum species from the Andes i.e.L. bipinnatifidum, L. kalenbornii nor L. chichicara.Cultivated maca (L.meyenii) is also the only species in the entire genus that produces fleshy roots 23 .The first farmers and herdsmen lived in the Andes before 2000 B.C. and maca was probably domesticated between 1300 and 2000 years ago.Primitive maca cultivars have been found in archaeological sites from about 1600 B.C. (ref. 2 ).Interestingly, maca is not depicted on old Peruvian ceramics, so rich in agricultural crop pictures 1 .Knowledge of this plant and its activities was transferred from generation to generation.During Spanish colonization, the native people used maca as currency 20 .Although maca is adapted to high altitudes and extremely low temperatures (it even grows more quickly at lower temperatures 21 ), it can be successfully transplanted to the Peruvian seacoast 20 .It is a plant with a neutral reaction to day length 5,21 and it can be successfully cultivated outside its natural localities 5 .We have obtained maca hypocotyls in the Czech Republic, but these are smaller than the Peruvian ones.More recently, maca has been introduced into Russia 24 .It is not yet entirely known, how the climate changes influence its spectrum of components.According to some researchers 25 , particularly harsh conditions give to maca its strength and potency.In lower altitudes, such as in Germany, maca does not form hypocotyls 25 .In the Czech Republic, hypocotyls are formed only in fields, not in greenhouses and differences in chemical composition (higher content of proteins and nitrates and lower content of saccharides) compared to commercial maca powder were observed 26 .It seems that for hypocotyl formation a cold climate is important.Smallanthus sonchifolius and Lepidium meyeniiprospective Andean crops for the prevention of chronic diseases

CHEMISTRY
The chemical composition of aerial and underground parts of yacon and of dried maca 27 hypocotyls (fresh maca contains up to 80 % of water and its composition was not found in the literature) is shown in Table 1.Yacon composition differs according to author 4,9,28 .For comparison, composition of the Jerusalem artichoke (Helianthus tuberosus) 29 and of radish (Raphanus sativus) 30 is also presented in Table 1.

Saccharides
Yacon tubers contain as storage compounds mainly fructans with low glucose content.Their structure is of the inulin type, i.e. β(2→1)fructofuranosylsaccharose (see Table 2), of the same type as in other Asteraceae species, e.g.Jerusalem artichoke 31 .Similar low DP fructans have been used as sucrose substitutes; they are considered dietetic.They have a favourable influence on the human intestinal flora and can modify some hyperlipidemias.Humans have no enzyme capable of hydrolysing the β(2→1)bond 2 .β(2→1)fructans of the inulin type are thus dietary fibre or the indigestible residues of plant origin in human diet 32 .
Recently, oligofructans have been classified as prebiotics 33 .These are not digested in the human gastrointestinal tract and they are transported to the colon where they are fermented by selected species of gut micro-flora, especially Bifidobacterium and Lactobacillus, both indicators of a balanced gut flora.Studies in voluntary subjects have demonstrated that prebiotic consumption modifies gut flora composition and its metabolic activities.Probably through this action they also modulate lipid metabolism, calcium absorption, childhood immune systems and gut function.The prebiotic effect of yacon tuber extracts has been demonstrated by their fermentation by several common gut bacteria Lactobacillus plantarum, L. acidophilus and Bifidobacterium bifidum 34 .β(2→1)fructans are related to β-glucans, native polysaccharides from yeast and fungi, which act as non-specific immunostimulators.They bind specifically to macrophages, activate them and initiate the immunity cascade.β-Glucans are recommended for the treatment of immunity defects, infections, allergies, chronic fatigue syndrome, high cholesterol levels, stomach problems and as an adjuvant in carcinoma therapy 35 .
Yacon tubers are also rich in free fructose, glucose and sucrose 8 .Saccharide and the related enzyme content in tubers fluctuates during cultivation and storage; during cultivation, the degree of polymerisation in the fructans increases while it declines during storage, increasing in content of fructose, glucose and sucrose 34,36,37 .Similar changes in composition occur also in the Jerusalem artichoke, so far the greatest source of inulin and fructose 38 .The enzymes involved in oligofructans metabolism and also the oligosaccharides themselves have been recently isolated and identified from yacon tubers and caudices in different stages of growth.According to one study 39 , eight months after planting is the best yacon harvest time in tropical regions.
We have already described the presence of caffeic, chlorogenic and ferulic acids in yacon leaves detected using HPLC/DAD-MS in ethyl acetate extract from the leaves of yacon 46 .The presence of the phenolic acids was then confirmed by HPLC coupled with electrochemical detection (HPLC-ECD) 47 together with identification of gallic and gentisic acid.Recently, we have described a detailed analysis of phenolic compounds from three extracts of S. sonchifolius leaves 44 .We confirmed chlorogenic, caffeic and ferulic acid, three isomers of dicaffeoylquinic acids (M r = 516), an additional still unknown derivative of chlorogenic acid (M r = 562) and an equally unknown flavonoid by HPTLC and HPLC/MS.These compounds were then also confirmed in yacon leaves, stems, caudices and tubers 48 .Flavonoid compounds with antimitotic activity have been isolated from related S. fruticosus, particularly centaureidin (X) (4,5,7-trihydroxy-3,6-dimethoxy-flavone) 49 (Fig. 2).

Fig. 1. Caffeic acid derivatives found in yacon tubers
123 Smallanthus sonchifolius and Lepidium meyeniiprospective Andean crops for the prevention of chronic diseases Catechins (2.5 mg/g of hypocotyls DW) have also been identified in maca hypocotyl aqueous extract.This displayed antioxidant activity.From comparison with green tea the authors concluded that this activity is due to maca isothiocyanates rather than to the catechins 50 .

Glucosinolates and isothiocyanates
Some authors 5 believe, that active maca constituents are aromatic isothiocyanates, i.e. benzylisothiocyanate XXVII and 4-methoxybenzylisothiocyanate XXVIII or prostaglandins and sterols.Aromatic isothiocyanates are present in mashua (Tropaeolum tuberosum), known for its aphrodisiac and contraceptive activity in men and increasing female fertility 71 .
The above-mentioned maca relative garden cress (L.sativum) is an interesting vitamin C (52 mg in 100 g), B 1 , K and β-carotene source.Its typical spicy flavour is due to its content of glucosinolates and isothiocyanates, especially glycotropaeolin and benzylisothiocyanate. Garden cress improves digestion.Another European maca relative, radish (Raphanus sativus var.nigra), contains ceteri paribus glucobrassicin XXX (3-indoyl-methylglucosinolate), isothiocyanates and it is traditionally used as choleretic, cholagogue, to treat bronchitis and burns 80,81 .In local Andean markets yacon is classified as a fruit and sold together with apples, avocados and pineapples and not together with potatoes or tuber crops as one could expect.Its tubers have a delicious sweet flavour, they are crispy and native people commonly expose them to sunlight to increase their sweetness.They are consumed, peeled, usually in fruit salads together with e.g.bananas or oranges.They can also be eaten steamed when they conserve their crispiness to a certain extent and it is possible to cook or fry them in many different ways 6 .Refreshing juices or concentrates suitable as sweetener for diabetics can be made from the tubers 4 .Also young stems can be used as vegetable; the main stem is used as celeri 2 .In Japan, yacon tubers are processed into juices, bakery products, fermented beverages, lyophilized powder or pulp 82 .The suitability of yacon foodstuffs for diabetic dishes, diets for weight reduction and for patients with chronic liver diseases has been shown in a clinical study performed at Olomouc Faculty Hospital 6 Yacon tubers were used for centuries by original Peruvian populations as a traditional folk medicament to treat hyperglycemia, kidney problems and for skin rejuvenation.In Brazil, medicinal properties have been ascribed to yacon leaves that are used to prepare a medicinal tea.In Japan, yacon leaves and stems are mixed with tea leaves 83 .Yacon aerial parts, containing large amounts of proteins, can be also used as green stuff for livestock 4 .
Hypoglycemic effects of yacon leaf aqueous extracts have been demonstrated in normal and diabetic rats 4,83 .We have described the antioxidant activity of two extracts in relation to the content of phenolics 46 .Moreover, we have shown that extracts exhibited cytoprotective effects against tert-butyl hydroperoxide and allyl alcohol induced oxidative damage of rat hepatocytes in primary cultures.We have also demonstrated that yacon leaf extracts reduce glucose production in hepatocytes via both gluconeogenesis and glycogenolysis pathway, and their insulin-like effect was demonstrated on CYP2B and 2E mRNA expression in Fao cells 84 .Maca is eaten raw or cooked in pachamancas (underground ovens lined with hot stones) or stored dried for later consumption.Dried maca hypocotyls conserve their properties for years 5 .The dried roots are eaten after boiling in water or milk, and are sometimes mixed with honey and fruits for the preparation of juices, gelatines or jams, and addition of sugarcane rum for cocktails and other alcoholic beverages.Native herbalists recommend maca decoction in reconvalescence 20 .Flour is also prepared from the dried roots for making bread and cookies.Toasted and ground hypocotyls are used to prepare "maca coffee" 5 .Maca is fermented to prepare a beer in several Peruvian areas 75 .Maca leaves, like garden cress (L.sativum), are consumed in salads 2 .Complementary and alternative medicine recommend ground maca hypocotyls as fertility enhancers and aphrodisiacs for men and livestock.Indian women eat it when they want to get pregnant 1 .In South America maca is called Peruvian or Andean Ginseng 1,5,85 .Maca is also recommended as an adaptogen, immunostimulant, anabolic, in menopause and for influence on hormonal balance.Maca hypocotyls are ground and sold as a nutracetical 1 .In Peru, maca is offered in the form of powder, chips, liqueurs 75 etc., on the world market it is distributed under the commercial names Royal Maca™ (ref. 86), Maca750™ (ref. 87), MacaMagic™ (ref. 88), "Maca Andina" 89 , Vimaca®, Eregma power 90 and MACA 91 .Aphrodisiac effects of maca hypocotyls have been ascribed especially to its alkaloids, which according to Natural Health Consultants 86 affect the pituitary-hypothalamus axis.In contrast, MacaMagic™ producer HERBS AMERICA NETWORK 88 declare that unique maca properties are due exclusively to its composition of essential amino acids, fatty acids, vitamins and minerals.Chacón de Popovici 20 recommends maca use for treating malabsorption syndrome, protein deficiency disease, during chemotherapy for leukaemia, AIDS treatment, alcoholism and menopausal anaemia.Others mention its use to treat chronic polyarthritis, during allergy attacks and as laxative 71 .Traditional maca uses are also related to religious ceremonies; it was mixed with hallucinogens used in sacrificial ceremonies 71 .
Reliable pharmacological confirmation of all cited effects was missing until very recently.Chacón de Popovici 20 concluded that maca stimulates Graafian follicle maturation after an experiment on female rats fed maca, or maca alkaloid extracts for 6 months.In males she observed a clear stimulation of spermatogenesis.
A number of studies showing the aphrodisiac effects of maca have appeared over the last few years.Positive effects of a lipidic extract, containing mainly macaenes and macamides, on mice and rats were described in 2000 (ref. 92).The extract not only increased the number of complete intromissions and sperm-positive females in normal animals, but also decreased latent period of erection in rats with erectile dysfunction.Application of maca hypocotyl aqueous extract to male rats induced an increase in testis size and stimulation of spermatogenesis in its initial stages 93 .Enhanced sexual behaviour was also observed when Maca pulverized root was administered to sexually inexperienced rat males by a gastric tube.The effect on the parameters tested was already observable after acute administration and was independent of maca action on spontaneous locomotor activity 94 .In the same test, using maca successive hexanic, chloroformic and methanolic extracts, the hexanic extract was the most efficient 95 .In adult men, after 4 months maca treatment, significant sperm volume, total sperm count and sperm motility increase was observed.In contrast, serum sexual hormone level was not affected by the treatment [96][97][98] .Progesterone and testosterone levels were increased in maca treated mice but there were no marked changes in estradiol levels or in the rate of embryo implantation 99 .Some compounds with testosterone-like activity, probably phytosterols, are responsible for maca biological activity.We have also recently proved estrogenic activity of maca extracts on MCF-7 estrogen positive cell line 40 .
Maca nutritional properties were evaluated in white mice 100 .The growth curves in all groups fed maca were significantly better than in those of a control group.This study demonstrates, according to the authors, one of the traditionally attributed properties of maca, its nutritional capability.

CONCLUSION
Trends in nutraceuticals and functional foods containing biologically active natural substances are oriented towards intact plants or plant extract utilization in this millennium.Nutraceuticals are coming to be indispensable diet constituents for all population groups in the prevention or remedial treatment of many chronic diseases.Considering the fact that yacon and maca can be cultivated in the European climatic conditions we assume that nutraceuticals based on these plants could be a contribution to the prevention and remediation of diseases such as diabetes mellitus, cardiovascular disease, fatigue syndrome etc. Promising seem to be the combination of yacon with silymarin which has been shown to improve the metabolism of triacylglycerols and glucose in both humans and rats 101 .The preparations should be economically accessible to wide public, without adverse side effects and according to valid legislation 102 .Comprehensive yacon and maca investigation is related to low economic risk and ready application of results.
a Content of N-substances; b Content in solid matter; c Content in dried hypocotyl