Southeast-ern Asia is the center of origin of citrus ( Blench, 2008), where it originated in the area between India, South China and Indonesia (Timmer et al. 2003). Today, citrus is cultivated in the subtropical and tropical regions of the world. The most commonly propagated citrus species are sweet orange (C. sinensis), mandarin (C. reticulata), grapefruit
(C. paradisi ), calamondin (C. mitis), citron ( C. medica), wild orange (C.
macroptera ), lemon (C. limon), Kaffir lime ( C. hystrix), pummelo (C. grandis ),
sour orange (C. aurantium ) and lime (C.
Aurantifolia) (Manner et al. 2006). Some species, such as sweet orange and lemon, grow best in the subtropics, whereas limes and pommelo are produced primarily in the lowland tropics (Timmer et al. 2003). Although sweet orange (Citrus sinensis) is the major fruit in this group accounting for about 70% of citrus output (Okwu,2008).
Citrus is consumed as a fresh fruit and as processed product, and is unique taste. Citrus are rich of phytochemical compounds such as ascorbic acid,
flavonoids, limonoids, phenolic compounds, carotenoids, glucarates, monoterpenes and pectins. Phytochemicals can be defined as substances found in edible fruits and vegetables that, daily ingested, may exhibit a potential for modulating human metabolism in a manner favourable for the prevention of chronic and degenerative diseases. Those phytochemicals react by different mechanism by maintaining cellular oxidation-reduction
balance, protecting cells against free radical mechanism, chelating of heavy metals, direct detoxification of
xenobiotics, control of membran permeability and by unkown mechanism.
As a example, investigation breast cancer have identified oxidation damage, action of hormones and the action of kinds prostaglandins as
promotors of neoplastic proliferation see the Figure 1 (Pierson, 1992). Figure 1 also shows the influence of phytochemicals diet against cancer.
 |
| Figure 1: Breast cancer promotion and phytochemicals mechanism to protect (Pierson 1992 in Ngy and Atawi, 1992) |
1. Carotenoids
Carotenoids concentration and composition vary greatly among citrus varieties and depend on the growing conditions (Gross, 1987) carotenoid accumulated on maturation process, but concentration of carotenoids was highly regulated by the coordination among the expression of the carotenoid biosynthetic genes(Kato, et.al, 2004). There are two type of carotenoids base on its solubility i.e. Carotene and Xantophylls. Carotene (i.e. β-carotene,α-carotene, lycopene, ect.) has more soluble on non polar solution and xantophylls ( i.e lutein, zeaxanthin, ect.) has more soluble on polar solution like water. Some carotenoids serve as precursors for vitamin A, which is essential to human and animal diets, and as antioxidants, which play a role in reducing the risk of certain forms of cancer (Olson, 1989).
2. Ascorbic acid
Ascorbic acid also known as Vitamin C,
L-ascorbic acid and watersoluble vitamin, found especially in
citrus fruits and vegetables. It is synthesized by most
organisms from glucose but man and other primates and
various other species must obtain it from their diet. Ascorbic acid is required in the synthesis of
collagen in connective tissues, neurotransmitters, steroid
hormones, carnitine, and conversion of cholesterol to bile
acid and enhances iron bio-availability. Ascorbic acid is
a great antioxidant and helps to protect the body against
pollutants. It is also a biological reducing agent linked
to prevention of degenerative disease such as cataracts,
certain cancers and cardiovascular diseases (Igwe, 2014). Ascorbic acid is widely used as antioxidant in frozen fruits, canned meat, beverages, beer and other food items.
3. Flavonoids
Based on molecular structure flavonoids are divided into six classes: flavones, flavanones, flavonols, isoflavones,anthocyanidins and flavanols. The main chemical structures of some flavonoids isolated from Citrus fruits their structures (flavanone, flavone, or flavonol) and their chemical groups.The main flavonoids found in citrus species are hesperidine, narirutin, naringin and eriocitrin (Mouly et al., 1994; Schieber et al., 2001)
4. Limonoids
These water-insoluble aglycones are usually responsible for the bitter taste of citrus juices. More than seventeen limonoid glycosides were also reported so far. Limonoid glycosides are not bitter in taste and freely soluble in water. Beside their economic importance in the processing of citrus fruits, limonoids have a wide array of interesting biological activities. Limonoids are gaining more current interest as potential anticancer agents. Limonoids are reported to inhibit chemically-induced tumorigenesis formation in the mouth, stomach, small intestine, colon, lung, and skin of experimental animals (Champagne et al., 1992; Berhow et al., 2000). They also reported to inhibit proliferation of breast cancer cells in vitro (Berhow et al., 2000) and moult activity in mosquito Culex quinquefasciatus larvae (Jayaprakasha et al., 1997). Obacunone and limonin, the known citrus limonoids, were recently reported to inhibit azomethane-induced colon carcinogenesis in rats (Tanaka et al., 2000).
Based on molecular structure flavonoids are divided into six classes: flavones, flavanones, flavonols, isoflavones,anthocyanidins and flavanols. The main chemical structures of some flavonoids isolated from Citrus fruits their structures (flavanone, flavone, or flavonol) and their chemical groups.The main flavonoids found in citrus species are hesperidine, narirutin, naringin and eriocitrin (Mouly et al., 1994; Schieber et al., 2001)
4. Limonoids
These water-insoluble aglycones are usually responsible for the bitter taste of citrus juices. More than seventeen limonoid glycosides were also reported so far. Limonoid glycosides are not bitter in taste and freely soluble in water. Beside their economic importance in the processing of citrus fruits, limonoids have a wide array of interesting biological activities. Limonoids are gaining more current interest as potential anticancer agents. Limonoids are reported to inhibit chemically-induced tumorigenesis formation in the mouth, stomach, small intestine, colon, lung, and skin of experimental animals (Champagne et al., 1992; Berhow et al., 2000). They also reported to inhibit proliferation of breast cancer cells in vitro (Berhow et al., 2000) and moult activity in mosquito Culex quinquefasciatus larvae (Jayaprakasha et al., 1997). Obacunone and limonin, the known citrus limonoids, were recently reported to inhibit azomethane-induced colon carcinogenesis in rats (Tanaka et al., 2000).
5. Phenolic acid
Based on two basic structure, hidroxycinnamic with R1, R2, R3 variation and hidroxybenzoic with R1, R2, R3, and R4 variation of tails radical. The major phenolic acid found in juice of coated tangerine was identified as ferulic acid followed by sinapic, caffeic and p-coumaric acid (Puttongsiri, and Haruenkit 2010). Phenolic acid well known of antioxidant activity by donor hydrogen mechanism.
6. Glucarates
Calcium-D-glucarate has been shown to inhibit beta-glucuronidase, an enzyme involved in phase II liver detoxification. Elevated beta-glucuronidase activity is associated with an increased risk for various cancers, particularly hormone-dependent cancers such as breast cancer. In this pathway, glucuronic acid is attached to certain toxins as well as hormones such as estrogen to facilitate their removal by excreting them via bile into the intestinal tract (Bruno).
Based on two basic structure, hidroxycinnamic with R1, R2, R3 variation and hidroxybenzoic with R1, R2, R3, and R4 variation of tails radical. The major phenolic acid found in juice of coated tangerine was identified as ferulic acid followed by sinapic, caffeic and p-coumaric acid (Puttongsiri, and Haruenkit 2010). Phenolic acid well known of antioxidant activity by donor hydrogen mechanism.
6. Glucarates
Calcium-D-glucarate has been shown to inhibit beta-glucuronidase, an enzyme involved in phase II liver detoxification. Elevated beta-glucuronidase activity is associated with an increased risk for various cancers, particularly hormone-dependent cancers such as breast cancer. In this pathway, glucuronic acid is attached to certain toxins as well as hormones such as estrogen to facilitate their removal by excreting them via bile into the intestinal tract (Bruno).
Refferences:
Berhow M. A., Hasegawa S., and Manners G. D. (2000), Citrus Limonoids Ð Functional Chemicals in Agriculture and Food. Berhow and Hasegawa, American Chemical Society, Washington DC
Blench, 2008, A history of fruits on the Southeast Asian mainland Research Institute for Humanity and Nature, Kyoto, Japan
Bruno, G. Detoxification: The Role of the Liver & Nutraceutical Support, http://www.hchs.edu/sites/default/files/files/Detoxifiction.pdf
Champagne D. E., Koul O., Isman M. B., Scudder G. E., and Towers G. H. N. (1992), Biological activity of limonoids from Rutales. Phytochemistry 31
Gross J (1987) Carotenoids: Pigments in Fruits. Academic Press, London
Igwe, OU, 2014, Quantitative Estimation of Ascorbic Acid Levels in Citrus Fruits at Variable Temperatures and Physicochemical Properties International Journal of Chemical and Biochemical Sciences, 5.
Jayaprakasha G. K., Singh R. P., Pereira J., and Sakariah K. K. (1997), Limonoids from Citrus reticulata and their moult inhibiting activity in mosquito Culex quinquefasciatus larvae. Phytochemistry 44, 843 - 846.
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Ledesma, N, Nutrition & Breast Cancer, http://cancer.ucsf.edu//_docs/crc/nutrition_breast.pdf
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Olson JA (1989) Provitamin-A function of carotenoids: the conversion of β -carotene into vitamin-A. J Nutr 119: 105–108
Puttongsiri T and Haruenkit R., 2010, Changes in Ascorbic Acid, Total Polyphenol, Phenolic Acids and Antioxidant Activity in Juice Extracted from Coated Kiew Wan Tangerine During Storage at 4, 12 and 20°C Kasetsart J. (Nat. Sci.) 44 : 280 - 289
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functional compounds - recent developments. Trends in Food Science and Technology, 12: 401-413.
Tanaka T., Kohno H., Tsukio Y., Honjo S., Tanino M., Miyake M., and Wada K. (2000), Citrus limonoids obacunone and limonin inhibit azomethane-induced colon carcinogenesis in rats. Biofactors 13, 213-218
Timmer L.W., Garnsey S.M. and Broadbent P. (2003) Diseases of citrus. In: Diseases of Tropical Fruit Crops (ed. R.C. Ploetz), pp. 197–226. CAB International, London.
