Extraction and determination of polyphenols and betalain pigments in the Moroccan Prickly pear fruits (Opuntia ficus indica)

1 Introduction

The prickly pear (Opuntia ficus indica) is a tree originating in Mexico. It has the particularity to grow in arid semi-arid regions. It has been introduced in 16th century in several continents, notably in northern Africa. It yields an edible fruit called the prickly pear. In Morocco the prickly pear is realized for traditional uses as hedges of demarcation, to struggle against the erosion, for improvement of pastoral perimeters or else for the fruits consumption in expenses. Recently, in some countries as Mexico, Italy and South Africa, the Prickly pear is cultivated on considerable surfaces for industrial ends in Mexico, its culture stretches on a surface of 300,000 ha, while to Morocco, the surface of the culture of the Prickly pear is of about 120,000 ha (Boujghagh and Chajia, 2000; Arba, 2006) except Sahara and mountainous regions, the Prickly pear is broadly present in the Moroccan country, but its culture is badly organized and structured. Several searches show that the Prickly pear is a plant very rich in vitamins, minerals (Stintzing and Scheiber, 2003), amino acids and in sugars. It is used as foodstuffs, for medical applications, cosmetics and for production of the cochineal. Betalains concentrate in blooms and plants fruits of the generality of families Caryophyllals (Clement and Mabry, 1996). Those pigments are by-products of the betalamic acid. Betalains are pigments soluble in waters and are identified for the first time in the plant of the red beetroot (Dull vulgaris) (Wohlpart and Mabry, 1968).

The betalain pigments are in amaranth (Amaranthaceae) (Cai et al., 2005), bractées bougainvillaeas (Nyctaginaceae), and flowers (Minale et al., 1967) or other groups of plants in the Aizoaceae, Basellaceae, Didieraceae, Phytolaccaceae and Portulaceae (Glassgen et al., 1993; Schliemann et al., 1996; Gandia-Herrero et al., 2005). They are equally present in some mushroom kinds of the genus Amanita and Hygrocybe (Dopp and Musso, 1973). Betalains are a class of pigments, yellow Chromoes-alkaloids (betaxanthins). Some cultivars of the prickly pear are characterized by a deep red color caused blush by the presence of betacyanin pigments.

Several searchers have quantified and have identified betalains pigments in prickly pear of Mexican or Spanish origin (Castellanos-Santiago and Yahia, 2008; Fernandez-Lopez and Almela, 2001).

Other studies have shown that the juice of prickly pear is rich in polyphenols (Enza et al., 2003). Polyphenols have been studied for their protective effects against pathogenic bacteria and the virus infecting plants, or the radiance UV. As antioxidants, polyphenols have the property to trap free generated radicals continuously by our body or formed as a defense to attack on our environment (tobacco, pollution, infections, etc.) (Scalbert and Williamson, 2000; Arnaud et al., 2001). A long time set aside to conventional society, the fruit production of the prickly pear (Opuntia ficus indica) is in clean progress to see the socioeconomic importance an environmental of this culture. Those fruits are rich in C vitamin, pigments of specimen betalains, phenolic compounds, sugar reducers and inorganic salts (Maataoui and et Hilali, 2004). In this frame, the study itself is interested to estimate the amounts of total polyphenols and betalain pigments of different fruits and juice of Prickly pear of Moroccan origin.

2 Materials and methods

2.1

2.1 Samples

The plant material used in this study is composed of prickly pears from two different cultivars Moroccans: Ait Baamrane (Fig yellow variety Moussa) and Essaouira (Fig red crimson variety El Akri). The sampling was conducted between July and September 2008. All experiments were performed three times to ensure repeatability. Our results are expressed as mean values (see Fig. 1).

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Figure 1

Structure of indicaxanthin and betaxanthin pigments.

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3 Results

The concentration of polyphenols (Table 1) varies depending on the nature of the sample analyzed (whole fruit or juice, red or yellow). The content of red polyphenols in prickly pear is about 15.34 ± 0.73 mg/kg of juice and 17.81 ± 0.10 mg/kg for whole fruit. In the yellow prickly pear the polyphenols content was 15.03 ± 1.36 mg/kg for juice and 15.03 ± 1.36 mg/kg for whole fruit. The average concentration of the polyphenol content of the whole fruit is higher than that of the juice alone, for the prickly pears red and yellow. This means that the pulp and seeds contain a quantity of polyphenols. The juice and whole fruit of red prickly pear contains a higher content of polyphenols compared with that of fig yellow.

The determination of betalain pigments is done in the juice of both prickly pears, red and yellow. The absorbances were measured at the wavelength corresponding to maximum absorption of betaxanthin (482 nm) and indicaxanthin (532 nm). The first remark is the absence of red pigments, indicaxanthin absorbs at 532 nm in the yellow prickly pear. However, yellow pigments (betaxanthin) are present with a relatively large content of an average value of 37.822 mg/kg.

The mean level of the juice of betaxanthin prickly yellow is 37.822 ± 0.151 mg/kg. This value is similar to that found by Stintzing and Scheiber (2003) for Italian fruit. The content in the fruit is about 48.30 mg/kg of juice, lower than that found by Butera et al. (2002), which is 84.20 mg/kg of juice. Betaxanthin content found is much lower than that of the prickly pear juice from Spain, work reported by Fernandez-Lopez and Almela (2001) (Table 2).

Regarding the composition indicaxanthin yellow fruit juices, we see that levels vary widely between regions. We noticed that indicaxanthin is either absent or present in trace amounts. These results are consistent with the work of Fernandez-Lopez and Almela (2001) who mentioned the lack of juice in indicaxanthin yellow Prickly pear from Spain. In the case of Italian yellow fruit, Stintzing and Scheiber (2003) cited very low levels in indicaxanthin. The reported values are of the order of 1.30 mg/kg of juice. However, Butera et al. (2002) mentioned that indicaxanthin is present at levels of about 10.40 mg per 1 kg of juice (Table 2). In the juice of Prickly pear red, pigment analysis of betalains indicates the presence of two types of pigments: betaxanthin and indicaxanthin.

The average content of the juice of betaxanthin Prickly red analyzed is about 45.87 ± 0.123 mg/kg of juice. This value is slightly higher than that found by Stintzing and Scheiber (2003) for Italian fruit. These latter values are equal to 36.40 mg/kg of juice, which show that they are superior to those found by Butera et al. (2002) for the fruits of the same origin and which is close to 26.10 mg/kg of juice. The values found in this work are lower than those reported by Fernandez-Lopez and Almela (2001) which was about 300 mg/kg of juice (Table 3).

The average content in the juice of indicaxanthin prickly red analysis is about 56.53 ± 0.263 mg/kg of juice. This value is similar to that found by Butera et al. (2002) for Italian fruit (51.20 mg per 1 kg of juice), lower than that found by Stintzing and Scheiber (2003) for the fruits of the same origin (73.90 mg/kg juice) and much lower than that cited by Fernandez-Lopez and Almela (2001) (190 mg per 1 kg of juice), corresponding to the fruit juice from Spain (250 mg/kg).

4 Conclusion

The extract of Moroccan prickly pear then presents an important source of poly-phenols. Our work shows that the levels of polyphenols are particularly higher in red fruits. These results also show that the red juice of Opuntia ficus indica is very rich in betalain pigments. This juice is characterized by a a higher content of red pigments in yellow pigments. The differences in results between regions are notably due to variability in the ecotypes cactus, physiology and growth conditions. Structural diversity in the sample of fig, makes it an exceptional product rich in natural antioxidants. The Moroccan prickly pear has also an important source of natural dyes that are in high demand in the food industry and trusted by consumers.