Traditional plants as source of functional foods: a review
Plantas tradicionales como fuente de alimentos funcionales: una revisión

Abstract

The aim of this work was to assess the following plants as functional foods that can be found in Mexico: white sapote (Casimiroa edulis), jicama (Pachyrhizus spp.), amaranth (Amaranthus hypochondriacus), sweet fennel (Foeniculum vulgare), oregano (Lippia graveolens), pitahaya (Hylocereus sp.), agave (Agave americana), pelitre (Heliopsis longipes), and purslane (Portulaca oleracea L). The main characteristics, components and active substances, forms of use in traditional medicine, nutritional properties, evaluation of biological assays, and the potential possibilities of research with the plants and/or extracts were reviewed.

El propósito de este estudio fue llevar a cabo una revisión de las siguientes plantas como alimentos funcionales que pueden ser encontradas en México: zapote blanco (Casimiroa edulis), jícama (Pachyrhizus spp.), amaranto (Amaranthus hypochondriacus), hinojo (Foeniculum vulgare), orégano (Lippia graveolens), pitaya (Hylocereus sp.), agave (Agave americana), pelitre (Helipsis longipes) y verdolaga (Portulaca oleracea L.). Las características principales, los componentes, sustancias activas, formas de uso en la medicina tradicional, propiedades nutricionales, evaluación en ensayos biológicos y el potencial de investigación con estas plantas y/o sus extractos fueron revisadas.

Keywords:

• nutraceuticals
• functional foods

Palabras clave:

• nutraceuticos
• alimentos funcionales

Introduction

Functional foods are defined as foods that have positive physiological effects beyond their nutritional function of providing nutrients. Nutraceutical substances with commercial value can be obtained from functional foods which have demonstrated a physiological benefit or are capable of providing some sort of protection against a chronic or infectious disease (Lajolo, 2002).

Mexico has tremendous potential for developing a nutraceutical industry. There are several research projects (Ganellin, 2005; Lajolo, 2002) underway in an attempt to find new sources of nutraceutical products, and the necessary extraction, concentration and stabilization methods and technology. Therefore, new products with enhanced nutritional properties, or new food additives, can be commercially available.

In this work, nine functional foods from Mexico were reviewed and summarized the following concerns: active substances and forms of use; traditionally demanded medicinal and/or nutritional properties; evaluation of biological assays; recommendations for their production and consumption; some examples of research being done regarding each plant or plant extracts, possible applications in food industry and patents already issued.

The functional plants included in this review are: white sapote (Casimiroa edulis), jicama (Pachyrhizus spp.), amaranth (Amaranthus hypochondriacus), sweet fennel (Foeniculum vulgare), oregano (Lippia graveolens), pitahaya (Hylocereus sp.), agave (Agave americana), pelitre (Heliopsis longipes), and purslane (Portulaca oleracea L).

Casimiroa edulis (white sapote)

White sapote is a 6–10 m high perennifolium tree, with a wide crown and a thick trunk with gray bark. Its fruit is drupaceous and round, yellowish or greenish in color, about 10 cm in diameter, and somewhat pear-shaped, although the shape depends on the variety. The parts of the tree that are used are the fruit and pits, and the raw leaves in cooking (Argueta-Villamar, 1994; Martínez, 1987). White sapote grows in warm areas with an altitude of over 1600 m high. It flowers in May, June, and July. It bears fruit in those same months and its fruits are available during June and July and they are eaten as a seasonal fruit. The species does not require specific handling. It propagates through its seeds. The use of this species is generally domestic. It is grown in family gardens. This is one of the fruit and tropical trees that best withstands cold weather, surviving temperatures of −4°C. In addition, it is one of the tropical species that best resists drought, although a regular supply of water is necessary during the development of the fruit (Casas, Viveros, & Caballero, 1994; Felger & Moser, 1976; Morton, 1987). The fruit is rich in vitamins A and C (180 and 800 mg/kg, wet weight respectively) and it possesses a high content of carbohydrates (160 g/kg wet weight) (Linares & Bye, 1990; Pennington & Sarukhán, 1991).

In traditional Mexican medicine, this plant has been used as a sedative. Bioassay-directed fractionation of the methanolic extract of seeds of C. edulis led to the isolation of seven constituents with activity in the cardiovascular system, namely the new compound (synephrine acetonide) and the known compounds (N-monomethylhistamine, N,N dimethylhistamine, proline, N-methylproline, γ-aminobutyric acid, and casimiroedine). In anesthetized rats, both histamine derivatives produced transient hypotension mediated via H1-histaminergic receptors and via nitric oxide release. Synephrine acetonide produced transient hypertension and tachycardia, via α and β-adrenergic receptors, respectively (Aguilar-Contreras, 1982; Lara & Márquez, 1996).

Pachyrhizus spp. (jicama)

Jicama has an appearance similar to a turnip or a large radish. Its skin is thin and it can be gray, light brown or maroon. In addition, it has a short root and its flesh is white. Only the tubercle is edible. The best land for culturing this plant is a frank-sandy type. Sowing takes place during July and August and is normally monocultured. Harvesting takes place at the end of November. The jicama has a skin that can be easily peeled. This plant contains fructans, triterpenes, steroids, phytosterols and phenols in its leaves, stem and the roots. It contains vitamin C, found in roots about 2570 mg/kg wet weight), and has significant amounts of iron (6 mg/kg) and potassium (1750 mg/kg) in leaves. Rotenone, a substance with insecticide properties that may be toxic to humans, is also found in leaves, stems, sheath, and seeds (Hung et al., 2007). It has been found that ethanol extracts of the seed decreased locomotor activity, produced muscle relaxation and showed anxiolitic and anti-aggressive activity (Abid, Hrishikeshavan, & Asad, 2006).

The white flesh is for consumption, usually juicy, and having a moderately sweet to very sweet flavor. It is also commonly used as a juice drink and as a syrup rich in fructans. It is also eaten as a vegetable. Raw jicama has a taste similar to that of a pear or an apple. It does not lose its color when exposed to air. As a result of the aforementioned, raw jicama is used as an additional dish prepared with raw vegetables (Hunter, 1999).

The leaves can be used in the elaboration of medicinal infusions, due to the phytochemical components present. The oleoresin in the jicama is known to have antifungal activity because it inhibits the growth of Fusarium sp. strains up to 80% of development of this fungus in corn. In addition, it has toxic properties for the control of the diamondback moth and bean worm (Juárez, Narro, Castro, & Fernández, 2004; Song et al., 2005). In addition, the large amounts of iron and potassium (2460 mg/kg) in the leaves, together with protein content (75%), make this part of the plant an important alternative for its industrial use in livestock nutrition (Cervantes, 1986). Jicama is also used as a water binding ingredient to help to inhibit microbial (especially fungus) propagation in food compositions that have 15–50% moisture (Friedman, Lysak, & Hornyak, 1975).

Amaranthus hypochondriacus (amaranth)

The average vegetative cycle of the amaranth lasts 180 days. It adapts to different types of soils and climates, and supports the lack of water very well. However, the harvesting of amaranth as a vegetable requires greater humidity (Nieto, 1990). For human use, the whole grain or milled as flour can be used, toasted, or boiled. With new leaves and the whole or ground grain, Amaranth is often used for preparing breakfasts, soups, desserts, refreshments, and other meals. A dish known as “Atole” and “Pinole” is prepared with “toasted” seeds, or ground or whole grains (Casillas, 1986a,b; Irving, Betschart, & Saunders, 1981; Prakash, Joshi, & Pal, 1995; Tapia, 1997).

Amaranth is a highly nutritive plant with a wide range of nutritive constituents such as proteins (130 g/kg), vitamins A, B₁ and B₂ (10 mg/kg, 140 mg/kg and 3 mg/kg, respectively) as well as folic acid and niacin (10 mg/kg each), and minerals (calcium, 1620 mg/kg; iron, 100 mg/kg; phosphorous, 4550 mg/kg), which make it vegetal food with better nutritional properties than human milk and the rest of the cereals. The amount of protein in the seed is greater than that of all cereals. It contains twice as much protein than corn and rice, and 60–80% more than wheat. It has an excellent balance of amino acids and contains an important amount of lysine (16%), an essential amino acid for human nutrition and commonly limited in other cereals (Stallknecht & Schulz-Schaeffer, 1993). Lipid content ranges between 7 and 8%. Diverse studies have found a relatively high content of squalene, ∼8% of the oil from the seed (He, Cai, Sun, & Corke, 2002).

The nutritional value of the amaranth leaves has been widely studied (Casillas, 1986a,b). Growing Sprague-Dawley male rats were used in two experiments to determine the nutritional adequacy of four cultivars of amaranth grain. The authors concluded that three of the four amaranth cultivars tested have superior promoted growth effects in rats compared to that obtained with maize and comparable to that obtained with a 16% maize-soy diet (Santa-Cruz and Marban, 1986).

To date, no anti-nutrient has been found in amaranth; however there is controversy regarding the effect of oxalate levels on human health. Gélinas and Seguin (2007) reported that the oxalate found in 30 genotypes analyzed were within the acceptable range (average between 1780 and 2780 mg/kg), but other reports have indicated that under conditions of hydric stress, the leaves may contain a higher level of oxalates and nitrates which can have adverse effects on human nutrition. Nevertheless, when boiling the leaves, the concentration of these components decreases (Gélidas & Seguin, 2007; Gómez, & Tena, 1986). Other studies reported the effects amaranth has on hypercholesterolemia in animal models such as rats and hamsters (Berger et al., 1994; Chaturvedi, Sarojini, & Devi, 1993; Burri, Dionsi, Allan, & Lambelet, 2003; Shin, Heo, Lee, & Kim, 2004).

Starch is the main component in the amaranth seed, representing between 50 and 60% of its dry weight. Amaranth starch has two distinct characteristics that make it a promising product for the food industry: its unusual agglutinating properties and the very small size of the molecules, approximately one tenth the size of corn starch. These characteristics can be used for thickening or pulverizing certain foods or for imitating the consistency of fat. In the food industry, the compound amaranthine, derived from amaranth, is used for food coloring (Sánchez, 1980).

In traditional Mexican medicine, amaranth “Atole” is used to cure persistent diarrheas. Because of its high energetic content (4000 kcal/kg), it is also useful in patients with high caloric requirements. Some studies using animal models have demonstrated that amaranth has anti-hypertensive properties and a positive effects in plasma lipid profile (Czerwinski et al., 2004; Silva-Sánchez et al., 2008).

Foeniculum vulgare (sweet fennel)

It is a grass of meaty stems and petioles, with a strong arising odor, reaching upto 1 m height. This species multiplies from its seeds. Harvesting occurs from mid-fall to the beginning of spring, depending on the area and the regional climate. A temperate to warm climate is required. The most adequate soils are those of medium consistency, permeable and somewhat calcareous without excess humidity, but not dry (Fuentes & Granda, 1984). Its fruit is small, dry, long and slightly curved. It contains condensed glucides, phytosterols (β-sitosterols, stigmasterol), coumarin, essential oils (2–6%); anethole (60–85%), stragol (5%), and traces of α-pinene, limonene, mircene, fencone, canfene, sabinene, β-mircene, β-pinene, α-feladrene and α-terpinene; the leaves contain flavonoids and traces of essential oils. There are notable differences in the contained percentages of these components between the “vulgare” and “dulcis” strains (Kresanek, 1989).

Fennel is scarce as nutritional source, although it is rich in carbohydrates, including fiber. The variety and amount of vitamins that it contains is discrete (folates, 270 μg/kg; vitamin B₃, 6.4 mg/kg; vitamin C, 8.7–340 mg/kg). Fennel contains potassium (4.24–5.85 g/kg), the most abundant mineral by far, low amounts of phosphorous (500 mg/kg), calcium (5.6–363 mg/kg), magnesium (8.2–389 mg/k) and sodium (7.7–512 mg/kg) (Koudela & Petrikova, 2008). In the composition of fennel, there are large amounts of anethole found throughout the plant, yet mostly concentrated in the seeds. The digestive and carminative action of fennel is attributed to this substance and its pleasant taste and distinct perfume convert fennel into an appetizing vegetable to be included in meals.

The isolation and identification of the different active principles in fennel are of great therapeutic interest due to the wide spectrum of uses in traditional medicine where they have been recommended as anti-anorexigenic. Parejo et al. (2004) identified 42 phenolic substances, 27 of which had not previously been reported in fennel, including hydroxycinnamic acid derivatives, flavonoid glycosides, and flavonoid aglycons. The anethole contained in the essential oil is also neurotoxic (Roig, 1988). A extraction procedure for the essential oils has been described by Kawai, Nishibe, Ando, and Ando (1991). In industry, it is used for flavoring and aromatizing, and as organoleptic flavor corrector, and it is also a common component in toothpaste, soaps, and lotions (Muñoz, 1987).

Lippia graveolens (oregano)

Oregano plants are thin bushes of ∼2 m height; short hairy branches. They produce a small fruit, closed within the calyx. It is planted in seedbeds or nurseries at random. The composition and amount of secondary metabolites of these plants depends on climatic factors, the season when harvested and its state of growth. Because of the aforementioned, the study of these factors and their influence on the harvest is important for better use and exploitation of the plant (Arriaga, Cervantes, & Vargas-Mena, 1994).

In oregano, the active compounds are phenols derived from cafeic and romeric acids. It contains carioptosidic acid, naringenine, pinocembrine, felandrene, 1,8-cineol, p cymenene, but methyl thymol, carvacrol and thymol are the compounds of main commercial interest. In addition, the flavonoids, such as apigenine and luteoline, have been identified as well as aglicons, aliphatic alcohols, terpenic compounds and phenylpropane derivatives (Compadre, Hussain, Leon, & Enríquez, 1987). The essential oils of Lippia contain limonene, cariofilene, cymenene, camphor, linalool, pinene and thymol, which may vary according to plant strains. In the methanolic extract of the L. graveolens leaves, several minority iridoids can be found. It also contains flavonoids, such as lapachenol and icterogenine (Rastrelli, Caceres, Morales, De Simone, & Aquino, 1998). Oregano is used exclusively as a food condiment. One of the main biological activities of oregano is as antioxidant (Martínez-Rocha, Puga, Hernández-Sandoval, Loarca-Piña, & Mendoza, 2008); however Lippia species has both traditional culinary and medicinal uses. Oregano is also a strong source of vitamin C (0.5 mg/g) and other anti-oxidant compounds, such as carotenoids. The anti-oxidant effect of the methanolic extracts of oregano are due to the presence of cafeic and rosmarinic acids. The dry leaves of L. graveolens, are of common culinary use in Mexico (Arriaga et al., 1994).

The essential oil of oregano has the ability to induce an increase in the activity of the detoxifying enzyme glutathion S-transferase (GST) when administered orally, which suggests that it could be a potent anti-carcinogenic. The phenols, carvacrol and thymol, derivatives of oregano possess the highest levels of activity against Gram-negative microorganisms, except for P. aeruginosa, and with thymol being the most active. The minimum inhibitory concentration (MIC) values for essential oils have been established between 0.28 and 1.27 mg/mL for bacteria, and 0.65–1.27 mg/mL for fungi (Arriaga et al., 1994; Salgueiro, Cavaleiro, Gonçalves, & Proença da Cunha, 2003).

Among the different varieties of oregano, high levels of antioxidants (>1.40 mol/kg) have been found. The antioxidant potential of the oregano extracts has been determined for its ability to inhibit lipid peroxidation. The oregano extracts have been shown to be effective, in some cases higher than those exhibited by propyl gallate. However, their industrial applications are limited due to the aroma and flavor that they confer to foods to which they are applied and therefore, research into deodorizing processes must be looked into. The antioxidant activity depends on the type and polarity of the extracting solvent; for example, the antioxidants obtained with lipophyllic agents are more effective in emulsions. The essential oil represents an alternative for the protection of the harvest against plagues as is effective against parasitic infections. It possesses a wide spectrum of activity against insects, accarus, fungi, and nematodes, such as Rhyzopertha dominica, Tribolium castaneum and Sitophilus oryzae, plagues that attack stored grains, and against Musca domestica (Arcila-Lozano, Loarca-Pina, & Lecona-Uribe, 2004).

The oregano leaves are used not only as a food condiment, but also in the manufacturing of cosmetics, drugs, and liquor. Because of the antioxidant ability of the oregano aqueous extracts, it is suggested that they can be used as substitutes of synthetic antioxidants in foods. Lipid peroxidation is one of the main problems in the meat industry, during its processing, preparation, and storage. To solve this problem, the antioxidant effect of the leaves, extracts and essential oil have been tested, yielding positive results. Another interesting way to avoid peroxidation of fatty acids in meat is to use oregano essential oils as food supplements to feed livestock destined for human consumption. In the case of turkey and chicken whose feed is enriched with oregano, a significant decrease in lipid oxidation was observed in raw meat and refrigerated cooked meat, representing a good alternative to the use of α-tocopherol. The aforementioned is evidence that the antioxidant compounds present in oregano are absorbed and enter the circulatory system once ingested (Arcila-Lozano et al., 2004).

A patent describing the anti-parasitic activity of oregano has been issued. According to the invention, it has been discovered that oil of oregano administered orally, particularly after emulsification and tableted in a sustained release form, is capable of reducing the quantity and number of intestinal parasites detected by stool analysis, and in certain instances, totally eradicating intestinal parasites (Deluca, De Luca, Ronzio, & Sparks, 2003).

Hylocereus sp. (pitahaya)

Pitahaya is a xerophytic rustic plant belonging to the cactaceous family, a climbing perennial plant, and of bush-like conformation. The flowers are large, white and velvet-like, in the shape of a funnel, and are hermaphrodites conformed by abundant yarns laid in spirals and a lobulated stigma.

The pitahaya propagates by its seeds or through shoots. It grows in the wild on trees, dry trunks, rocks and walls. As it is a cactaceous, it is tolerant to high temperatures and long periods of drought, but not to water accumulations, for which the soil should be well drained. Another aspect that highlights the value of the Hylocereuses genera is their wide geographic distribution and climatic adaptation to different species. Each species has optimum developmental conditions. (Castillo & Cálix, 1995; Castillo, Cálix de, & Rodríguez, 1996).

Most of the species of the Stenocereus genera produces edible fruit generically called “pitahayas”, with a revealing characteristic; once mature, they lose their spines and areoles, making it much easier to eat. They also have pigments that can have application in the food industry.

The fruit is a bay of up to 7 to 14 cm long and 5 to 9 cm wide with a red epicarpium and a mucilaginous white or red pulp. Each fruit contains numerous small black shiny seeds. Its flavor is delicate to intensely sweet. It contains alkaloids, triterpenes, phenolic oxydrils, and saponines. The fruit contains flavones and leukoanthocyanines, saponines and unspecified alkaloids. It is consumed as fresh fruit, but may also be used in cocktails and refreshments. The stems of the Pitahaya play a very important role from an economic standpoint, since the young plants can be eaten by humans as vegetables.

The main use of the pitahaya is as food, consumed as fresh fruit or prepared with water and lemon. In Mexico, white pulps pitahayas have been processed to produce dehydrated fruits and liquor, although in the latter, the results have not been very satisfactory as it is not very aromatic. In addition to the special taste that the pitahayas have, the bromatologic analyses have shown they are rich in sugars (90–140 g/kg) and minerals (iron 3–7 mg/kg, calcium 60–100 mg/kg), although low in vitamin C (40–250 mg/kg) and with trace amounts of other vitamins (A, B₁, B₂). The seeds have large amounts of proteins (22.59% wet weight), while the plant has about 0.5% of total proteins (Perez, Vargas, & Ortiz, 2005).

The traditional Mexican medicine uses the stem ground and dissolved in water for gastritis. Among the native and rural population, the cactaceous have been an important source of food because of the water contained in their tissues and because of the large amount of carbohydrates (60% wet weight) in their fruits and proteins and fat in the seeds.

A patent related to the use of a plant or an extract or isolated molecules of a plant in the Hylocereus genus as a medicament has been issued, and relates to the use thereof in the preparation of compositions that are intended to prevent or treat lithiasis or a related disease and the invention further relates to methods of obtaining extracts or isolated molecules and the aforementioned compositions (Rakoto-Ratsimamanga et al., 2005).

Agave americana L (agave)

Agave is a perennial plant, acaulescent, resistant in arid terrain. The parts used are the roots, the leaves, and the sap (ASERCA, 2000; Chanzaro, 1989; M Irish & G Irish, 2000; Jin, Liu, & Yang, 2003). It grows in very sunny areas, although it also grows well in spite of not being totally under the sun; it requires well-drained soil, tolerates drought, and is frequently the sole survivor of abandoned gardens. They are plants that do not require watering or being taking care of. They multiply by basal sprouts that grow around the mother plant or by seeds at 20°C at the beginning of spring (Gentry, 1998). It contains saponines, inulin, fructans, and steroidal glucosides. It contains dietary fiber (64.2 g/kg), fructose (9 g/kg), glucose (11 g/kg). The “Aguamiel” from the agave is a sweet liquid, of pleasant taste, unstable, and if the weather is warm or hot, should be processed daily to avoid fermentation. It contains 53 g/kg of non-nitrogenated extract and 28 g/kg of proteins. Although this last amount seems small, it is interesting due to its composition in essential amino acids such as lysine (270 mg/kg), tryptophan (78 mg/kg), hystidine (78 mg/kg), phenylalanine (189 mg/kg), leucine (250 mg/kg), tyrosine (89 mg/kg), methionine (89 mg/kg), valine (221 mg/kg), and arginine (1.06 g/kg). It contains complex B vitamins, (4–5 mg/kg) and vitamin C (70–110 mg/kg). The main mineral contents are iron (17 mg/kg), calcium (4.17 g/kg) and phosphorus (710 mg/kg) (Bucasov, 1981; Islas-López, Sanjuan-Galindo, Rodríguez-Hernández, & Chavarría-Hernández, 2005; Pardo, 2002).

From agave, diverse alcoholic beverages are produced with high degrees of alcohol, such as “Pulque”, “Mezcal”, and “Tequila” (González & Galván, 1992).

The inhibitory concentration of the ethanolic extract of the agave on the in vitro growth of Entamoeba histolytica, Trichomonas vaginalis and Giardia lamblia, showing a greater susceptibility than the IMSS (Instituto Mexicano del Seguro Social; trans. Mexican Institute of Social Security): 0989 of Giardia. Entamoeba histolytica was shown to be twice as less susceptible to Trichomonas vaginalis and six times to Giardia lamblia to the ethanolic extracts (Oranday, Rivas, Morales, Mata, & Gutiérrez, 2004). The fructans present have been effective in laboratory animals in avoiding obesity and overweight, for which the ingredient could be part of the formulas to prepare milk-products, candies and bread products and, in fact, could be useful in the refreshment industry (Zhou, 2002).

In traditional Mexican medicine, saponines are used because of their diuretic effect, and are often used with good results in cases of edema and fluid retention. Externally, the juice or sap is applied on contusions and skin lesions. It is cleansing and a good source of steroidal saponines used in industry. Saponines are considered growth stimulants of the intestinal floral (prebiotic), are calorie-free, and often recommended in diets for weight control, as well as inhibitor of pathogenic bacterial growth (Escherichia coli, Listeria, Shigella and Salmonella) (Cruz-Ramirez, Valdez-Morales, Chacon-Lopez, Rosas-Cárdenas, & Cruz-Hernández, 2006). González and Galván (1992) reported the characterization of lyophilized aqueous extracts obtained from A. americana L (Agavaceae) with regard to their steroidal sapogenin content. Extracts of A. americana and sapogenins isolated from them were evaluated for anti-inflammatory properties by testing their effects on carrageenin-induced edema (Peana, Moretti, Manconi, Desole, & Pippia, 1997).

Helipsis longipes (pelitre)

Pelitre is a perennial herbaceous plant with a tall stem and alternating leaves, pinnated, and hairy on the reverse side that grows in the wild. In the Heliopsis genera, only aliphatic (afinine) and acetylenic alcamides have been found. Its roots are used in infusions. It has insecticide properties being the afinine the alkamide responsible for the main biological effects of this root. When the roots are chewed they produce a hot flavor. It is used as a condiment on beans instead of hot sauce. It is also added to alcoholic beverages. In the kitchen, it is used in the preparation of hot sauces together with the “chiles”, where it complements and highlights its flavor (Cruz-Ramirez et al., 2006; Rios, Aguilar-Guadarrama, & Gutiérrez M. del C. 2007).

In the roots of H. longipes, two unsaturated aliphatic amides called alkamides have been reported. The afinine (N-isobutyl–2E, 6Z, 8E-decatrienamide) is the most abundant followed by N-2-methylbutyl-2E-6Z-8E-decatrienamide). In preliminary studies, the fungi Phytophthora infestans, as well as Sclerotium rolfsii, were found to be the most sensible, because at a concentration of 75 mg/kg of pure afinine, as well as in the raw extract, a 100% inhibition of the micelial growth of both fungi was achieved. It was also found that the afinine had good bactericide action on Pseudomonas solanacearum (Acree, Jacobson, & Haller, 1999; Berger et al., 1994).

In preliminary trials of the bioactive compounds in the root, an important inhibitory action of the alkamides in the chicuage was found in in vitro susceptibility tests to Escherichia coli, Pseudomonas solanacearum, Bacillus subtillis, and Saccharomyces cerevisiae and in some phytopathogenic fungi such as Sclerotium cepivorum, Sclerotium rolfssi, and Fusarium oxysporum. Additionally, inhibition studies on Erwinia cartovora, Rizhoctonia solanii, Phytophthora infestans, Botritis sinerea, and Verticillum sp. were reported (Molina-Torres, Salazar-Cabrera, Armenta-Salinas, & Ramírez-Chávez, 2004).

There is a marketing project on the Chilcuague plant for manufacturing creams, drops, mouthwash, insect repellant, shampoo, and aftershave lotion. Patents on compositions based on H. longipes for maintaining or improving oral hygiene have been issued, as local anesthetic, and as a cough suppressant. The herbal composition includes an extract from H. longipes root and an oral carrier for the extract. A suitable amount of extract is from about 0.1 to 100 g/kg wet weight. A variety of compositions include an oral carrier. The invention is also useful as an enhancer of flavor (Wolfson, 2002).

Portulaca oleracea L (purslane)

Purslane belongs to the family of portulacaceas. It contains large amounts of mucilage, its most important active ingredient, giving it emollient, anti-inflammatory, and laxative properties. It also contains amino acids (alanine, arginine, histidine, valine), organic acids (ascorbic, aspartic, glutamic, linoleic, oxalic, palmitic), minerals (calcium, iron, magnesium, potassium), proteins, fiber, vitamins, and trace elements.

This species is often harvested in family gardens, tolerated and fomented in fields. In certain areas in central Mexico, it is harvested intensively. It propagates through its seeds. The major part of the production is auto-consumed. It is frequently found and sold in local and regional markets, except for the seeds that should be dried once gathered, the leaves should always be fresh when eaten (Molina-Torres, Salazar-Cabrera, Armenta-Salinas, & Ramírez-Chávez, 1992).

All of the plant, flowers, leaves, stems, and fruit are used in traditional Mexican medicine (Bello, 1993; Trujado, 1990). The plant is always used while fresh; in fact, it is known more as food than as a medicinal plant. It can be eaten in salads or mixed with other plants, providing nutritional and dietary properties given by the large amount of amino acids, fiber, and mineral content. The aerial part is often consumed by animals (Bye, 1981; González, 1984; Vázquez et al., 1995) but this is a very toxic plant, due to its high content of oxalates, and it has also been proven to have similar toxicity for humans.

P. oleracea has been used throughout history for many different medicinal purposes. A patent was issued in 2002 directed to the novel use of P. oleracea for the treatment of cancer. More specifically, it has been disclosed that P. oleracea has a specific and distinct effect on the inhibition and/or suppression of gastric tumor cell growth in vitro and in vivo (Yoon, Ham, & Jun, 2002).

Final remarks

The main characteristics, traditional uses and scientific reports of some of the functional properties of nine plants used as food in Mexico were reviewed. Although not all of the health claims of such plants have been scientifically proven, the evidence available suggests that these plants are potential sources of a variety of nutraceuticals and that they could have potential use as therapeutic substances, especially antimicrobials for use in food conservation and enteric infections and as food additives, thereby possessing a high commercial potentiality. In Table 1, the main characteristics of each plant are shown as an outline.

Table 1. Main characteristics and composition of the plants.
Tabla 1. Principales características y composición de las plantas.

Plant	Macronutrients (g/kg)	Micronutrients (mg/kg)	Traditional uses, medical or food	Research/patents	Notes
White sapote	Carbohydrates, 160	Vitamins	Sedative	Proved cardiovascular activity
	Lipids, 4	A, 180
	Protein, 14	C, 800
Jicama	Carbohydrates, 110	Vitamins	Syrup fructans rich	Antifungal	Contains rotenone
	Lipids, 0.8	C, 2,570		Livestock nutrition
	x	Minerals		Water-binding in food conservation
	Iron, 6
	Potassium, 1,750
Amaranth	Starch, 500–600	Vitamins	Desserts, atoles, soups, food coloring Diarrhea treatment	Anti-hypertensive	Moderate oxalate content
	Lipids, 70–80	A, 10		Lowering lipid profile in animal models
	Proteins, 130	B1, 140
		B2, 3
		Niacin, 10
		Minerals
		Calcium, 1,620
		Iron, 100
		Phosphorus, 4,550
Sweet fennel	Carbohydrates, 520	Vitamins	Carminative and anti-anorexigenic	Anethole as food additive
	Lipids, 140	Folate, 27
	Proteins, 150	B3, 6
		C, 870–3,470
		A, traces
		Minerals
		Potassium, 4,000–5,000
		Phosphorus. 500
		Calcium. 500–3,500
		Magnesium. 800–3,500
		Sodium. 700–5,000
Oregano	Carbohydrates, 600	Vitamins	Food condiment	Antioxidant, potential anticancer, antimicrobial, food additive as antioxidant
	Lipids, 100	C, 5
	Proteins, 100	Folate, 2
		Mineral
		Calcium, 15,800
		Iron, 400
Pitahaya	Carbohydrates, 600	Vitamins	Consumed as fruit	Patent in treatment of lithiasis
	Lipids, 20	C, 40–250	For treatment in parasitic infections
	Protein, 220	Minerals
		Iron, 3–7
		Calcium, 60–100
Agave	Carbohydrates, 20	Vitamins	Diuretic, in skin lesion, alcoholic beverages production	Anti-inflammatory
	Lipids, 0	B complex, 4–5		Anti-parasitic
	Proteins, 28	C, 70–110		Weigh control
	Fiber, 60	Minerals
		Iron, 17
		Calcium, 4,170
		Potassium, 710
Pelitre	Carbohydrates, NR	NR	Natural insecticide, condiment, in hot sauces	Antifungal	High content of oxalates
	Lipids, NR			Antibacterial
	Protein, NR			Local anesthetic
				Flavor enhancer
Purslane	Carbohydrates, NR	Minerals	Salads, natural emollient, natural laxative	Proven effective against gastric cancer in vitro
	Lipids, NR	Calcium, NR
	Proteins, NR	Iron, NR
		Magnesium, NR
		Potassium, NR
Note: NR, not reported. Nota: NR, no reportado.

Acknowledgements

This work is part of the IUPAC project “Project 2005-031-2-700”.