Figure 13.1: Chemistry, Structure of Capsaicinoids in the Capsicum Genus

The capsaicin biosynthesis occurs via the phenylpropanoid pathway; capsaicin is synthesized starting from the vanillylamine condensation with long chain fatty acids, which are synthesized from valine and vanillylamine originating from the mentioned pathway (Wagner, 2003; Titze et al., 2002). Prasad et al. (2006b), studying the biosynthesis of capsaicin in the C. frutescens, relate that valine pathway is more crucial than phenylpropanoid pathway.

Besides fruits, CAPS are found in different plant organs like stem and leaves. The presence of CAPS in a plant is shown to be correlated with the flowering period and above all with the presence of fruits (Zewdie and Bosland, 2001) from which they would have their origin, being produced in glands located in their placenta. According to a recent report, capsaicinoids are not present in plants without fruits (Estrada et al., 2002; Zewdie and Bosland, 2001)_. Environmental factors such as climate and soil, and other variables like cultural practices, crop and stockpiling and also genetic factors, influence incontestably on the qualitative and quantitative chemical composition in Capsicum genus.

Approaching qualitatively the proportion of capsaicinoids differs inside the Capsicum species and among them. There are studies in which capsaicin (1) is the major component (Garcés-Claver et al., 2006; Poyrazoglu et al., 2005) while in others it is dihydrocapsaicin (2) (Estrada et al., 2002). Together, they account for 90 per cent of the pungent substances of Capsicum fruits (Garcés-Claver et al., 2006). The nordihydrocapsaicin (3) is also reported (Schweiggert et al., 2006; Poyrazoglu et al., 2005; Sato et al., 1999; Constant et al., 1995) among the commonly observed pungent substances. Gibbs et al. (2004), studying C. annuum, C. frutescens and 28 other accessions of C. chinense, report that nordihydrocapsaicin was less abundant than capsaicin and homocapsaicin in all studied cultivars. Among minoritarian CAPS which have been found, several substances can be cited: norcapsaicin (4), nornorcapsaicin (13), homocapsaicin I (5), homocapsaicin II (6), nornordihydrocapsaicin (12), homodihydrocapsaicin I (7), homodihydrocapsaicin II (8), N-vanillyl-octanamide (10), N-vanillyl-decanamide (11) and N-vanillyl-nonanamide (9). This last one was previously known in synthetic form only, but was discovered occurring naturally and denominated nonivamide (9). There are also several isomers that occur as minoritarian constituents too (Constant and Cordell, 1996; Constant et al., 1995; Schweiggert et al., 2006; Luning et al., 1995; Kopp and Jurenitsch, 1981; Paul Jr. et al., 1975; Jurenitsch et al., 1979). Studies demonstrate that quantitative variations of the chemical components can be found according to species and cultivars, geographical origin and part of the plant. Poyrazoglu et al. (2005) studied varieties of C. annuum and C. frutescens collected in different areas and observed for Mara variety the content of capsaicin (1), dihydrocapsaicin (2) and nordihydrocapsaicin (3) in the ranges: 0.81-1.42, 0.38-0.70 and 0.01-0.04 mg g^–1, respectively; to Süs, Cin and Isot the total content of capsaicinoids was 2.11, 4.70 and 0.55 mg g^–1 respectively, and for their seeds 0.63, 1.70 and 1.60 mg g^–1. In another study, Choi et al. (2006) analyzing different varieties of peppers (Capsicum) found CAPS levels varying from 0.001 mg g^–1 (PR Gang ja) to 0.12 mg g^–1 (Chung yang). Homodihydrocapsaicin, as a general matter, was not found in the ripe fruits of 28 accessions of C. chinense nor in C. annuum and C. frutescens.

Capsaicin derivatives (Figure 13.2) have been object of several chemical and biological studies like 6’’,7’’-dihydro-5’,5’’’-dicapsaicin (14), isolated from C. annuum and (-)-capsaicinol (15) isolated from C. frutescens, both with similar antioxidant activity to capsaicin, without however having a pungent taste (Ochi et al., 2003).

Other substances, isolated from non-pungent cultivars, like capsiate (16), dihydrocapsiate (17) have also been described to their antioxidant activities (Rosa et al., 2002).

Figure 13.2: Chemistry Structure Derivatives of Capsaicin

Figure 13.3: Substances Antioxidants Non-pungents Found in Capsicum Genus

In C. annuum cv. “High Heat”, C. frutescens, and C. chinense fruits the glucosides identified were: capsaicin-β-D-glucopyranoside and dihydrocapsaicin-β-D-glucopyranoside; Observing the correlation among the quantity of the capsaicinoids capsaicin and dihydrocapsaicin and the derived glucosides, it is noted that the glucosides are not detected in nonpunget cultivars of C. annuum L. (Higashiguchi et al., 2006).

In polar fractions of fruits, leaves and branches of some Capsicum annuum varieties, it is possible to find acyclic diterpene glycosides of two classes: monomerics (capsianosides I-XI, XIII-XVII) and dimeric esters of those first ones (capsianosides A-G) (Yahara et al., 1991; Izumitami et al., 1990; Iorizzi et al., 2002; Lee et al., 2006; Song et al., 2001; Lee et al., 2008).

In C. annuum seeds and roots saponins, steroidal glycosides, deduced as glycosides furostanols, which are denominated capsicosides (A-D) are found (Yahara et. al., 1994). Other substances found were proto-degalactotigonin and some oligoglycosides. In seeds of C. annuum L. var. acuminatum the capsicosides A, D, F, G and E (Figure 13.4), also 22-O-methylcapsicoside A (19) and 22-O-methylcapsicoside G (20) were described (Iorizzi et al., 2002). Glycosides found in fruits of C. anuum L. var acuminatum are the capsoside A, capsoside B and the lignan glycoside icariside (Figure 13.4, 21) (Iorizzi et al., 2001).

Besides fruits, the sesquiterpenes observed in the stems and roots of C. annuum (Figure 13.5) are canusesnols A-J(22-31) and nine more compounds reported are reported substances: capsidiol (32), N-cis-feruloyltyramine, N-trans-feruloyltyramine, N-p-cis-coumaroyltyramine, N-p-trans-coumaroyltyramine, lariciresinol, 13-hydroxycapsidiol, lubiminol, and drummondol (Kawaguchi et al., 2004).

Figure 13.4:Chemistry Structure of Glycosides and Icariside

Figure 13.5:Chemistry Structure of Sesquiterpenes of the Capsicum Genus

Among the main flavonoids found in Capsicum are the flavonoids aglycones, luteolin, apigenin (flavones) and quercetin. In their non-hydrolysed forms, flavonoids quercetin and luteolin are found in Capsicum as: quercetin 3-O-α-L-rhamnopyranoside-7-O-β-D-glucopyranoside, luteolin 6-C-β-D-glucopyranoside-8-C-α-L-arabinopyranoside, apigenin 6-C-β-D-glucopyranoside-8-C-α-L-arabinopyranoside known as schaftoside, lutoeolin 7-O-[2-(2-(β-D-apiofuranosyl)-β-D-glucopyranoside], quercetin 3-O-α-L-rhamnopyranoside and luteolin 7-O-[2-(β-D-apiofuranosyl)-4-(β-D-glucopyranosyl)-6-malonyl]-β-D-glucopyranoside (Materska et al., 2003).

Quantification of flavonoids in Capsicum species have been performed for quercetin and luteolin in some cultivars, the concentrations reported are: Banana Supreme (186.0 mg kg^–1), PI 357509 (86.0 mg kg^–1) and Rio Grande Gold (26.0 mg kg^–1) for quercetin and Fidel (37.0 mg kg^–1) and Banana Supreme (21.5 mg kg^–1) for luteolin. Miean and Mohamed (2001) observed in C. frutescens a concentration of 1.035,0 mg kg^–1 for luteolin and 272.0 mg kg^–1 for apigenin. Values found in C. annuum are: quercetin, 34.0 mg kg^–1 and luteolin: 11.0 mg kg^–1 (Sun et al., 2007).

The colour determines the commercial value of the paprika oil-resin being usually associated to the sample quality: a great coloration capacity means a high quality (Mínguez-Mosquera and Pérez-Gálvez, 1998), which relates to the amount of carotenoids (Figure 13.6).

An important feature of Capsicum due to carotenoids is the vitamin concentration. Silva and Souza (2006) emphasize that Vitamin A concentration of green and red chilli peppers are considered one of the best sources of this vitamin about 10,500 and 11,000 IU respectively, close to the concentration of 13,000 IU found in carrot. The carotenoids contained in pepper species of Capsicum genus have antioxidant activity and the capacity to contribute significantly for the prevention of degenerative diseases like cancer (Etoh et al., 2000). Some of these oxygenated carotenoids like capsanthin (33), capsorubin (34) and capsanthin 5,6-epoxi (35) are exclusive of Capsicum genus (Deepa et al., 2007; Hornero-Méndez et al., 2000).

The most common carotenoids in Capsicum species are: capsanthin (33), capsorubin (34), zeaxanthin (36), cucurbitaxanthin A (37), and β-carotene (38) (Deli and Tóth, 1997; Reifschneider, 2000; Mínguez-Mosquera and Hornero-Méndez, 1993; Deli et al., 2001a; Hornero-Méndez et al., 2000). Several other carotenoids are found as minor constituents in Capsicum fruits (Deli et al., 1998; Maoka et al., 2004; Hornero-Méndez et al., 2000; Deli and Tóth, 1997; Reifschneider, 2000; Mínguez-Mosquera and Hornero-Méndez, 1993; Nagy et al., 2007; Deli et al., 2001b; Maoka et al., 2001a).

Figure 13.6:Chemistry Structure of Carotenoids in the Capsicum Genus

Due to carotenoids type or concentration, only some varieties or cultivars possess potential for paprika or oil-resin production. In an assay that studied different cultivars focusing paprika production, it was observed that total carotenoid contents varied from 12,700mg kg^–1 to 4,800mg kg^–1 in dry weight (Hornero-Méndez et al., 2002). Deli et al. (2001a) found in ripe fruits of lycopersiciforme rubrum variety 13.0g kg^–1 in dry weight of carotenoids: capsanthin (37 per cent), zeaxanthin (8 per cent), cucurbitaxanthin A (7 per cent), capsorubin (3,2 per cent) and β-carotene (9 per cent). In another assay, the quantitative and qualitative carotenoid distribution was studied in the Longum nigrum variety, obtaining from ripe fruits a total carotenoid content of 32g kg^–1 in dry weight (Deli et al., 1992). In the two varieties, most used for paprika production, Agridulce and Bola, carotenoids can be found at 1,360mg kg^–1 and 960mg kg^–1 of the fresh weight (Mínguez-Mosquera and Hornero-Méndez, 1993).

Marin et al. (2004) in an assay with C. annuum cv. vegasa, observed that the total of carotenoid pigments increased 4 times for the ripe red fruits when compared to the immature fruits. It was also observed that immature green peppers contained an extremely high polyphenol content, while ripe red fruits had an extremely high pro-vitamin A content [β-carotene (38) and β-Cryptoxanthin (39)]. Great variation in carotenoid content, according to the maturation stage, can be observed through total carotenoids values found in the most used C. annuum cultivars in paprika production, Agridulce and Bola. Lutein (40) and neoxanthin (41) disappeared with maturation, while β-carotene and the violaxanthin (42) increased and other carotenoids appeared: zeaxanthin, capsanthin, capsorubin, β-cryptoxanthin, and cucurbitaxanthin A (capsolutein) appeared (Mínguez-Mosquera and Hornero-Méndez, 1994b). Some values for the total carotenoid content in relation to the fresh weight for these cultivars are respectively: green fruits 39.22 and 33.41 mg kg^–1 and ripe fruits 1,359.98 and 961.80 mg kg^–1.

Breithaupt and Bamedi (2001) mention that carotenoids are found in alimentary plants in free form or as fatty acids esters. It was observed that during maturation there is a tendency to increment esterified forms and to reduce carotenoid free forms (Mínguez-Mosquera and Hornero-Méndez, 1994a).

Biological Activities

Capsaicinoids, the chemical substances present in the peppers and responsible for their pungency, CAPS, have a wide use in the pharmacology and neurology (Perucka and Oleszek, 2000).

Several human physiological processes are initiated by CAPS through mediation of chemical receivers; one of these processes is the endorfin liberation (Wagner, 2003). The CAPS, even when used in small levels in the diet, have been shown to be substances capable to increase the basal metabolism rate in humans. It is attributed to increment of the energy expense with fat burning, especially in those people with a high Body Mass Index and obese people, with consequent weight reduction, suppression of the corporal fat accumulation and decrease in the serum myocardial and aortic cholesterol levels, therefore being able to contribute in a diet therapy for obesity. In addition, the crude extract of C. annuum has been shown to have antidiabetic and antihypertension potential (Kwon et al., 2007).

This activity is speacially observed at non-pungent capsaicinoids, as capsiate (16). Another compound, (-)-capsaicinol (15) also non-pungent, is reported to have the same thermogenesis and acceleration of the lipid metabolism properties (Inoue et al., 2007; Kawabata et al., 2006; Ohnuki et al., 2001a; Ohnuki et al., 2001b; Masuda and Nakatani, 1991; Westerterp-Plantenga et al., 2006; Topuz and Ozdemir, 2007; Govindarajan and Sathyanarayana, 1991).

Capsaicin (1) decreases blood glucose levels, and is hypothesized that it can aid in lowering LDL even when consumed for a short period (Ching and Mohamed, 2001; Lee et al., 2003). Topically used capsaicin is shown to be effective in the treatment of cutaneous allergy, and other uses in cutaneous disorders that involve pain and inflammation, urticary, psoriasis vulgaris. Other biological activities of capsaicin already reported are: anodyne effect, post-herpetic neuralgia, vasomotor rhinitis, hyperactive rhinopathy, cluster headaches, post-mastectomy pain, temporomandibular joint pain, osteoarthritis, rheumatoid arthritis, apocrine choromohydrosis; also provides relief in arthritis and respiratory ailments and neurological conditions like neurogenic pain, diabetic neuropathy, nostalgia paraesthetica, meralgia paraesthetica, antiinflammatory and pain in Guillain-Barré syndrome (Cordell and Araujo, 1993; Constant et al., 1995; Davis et al., 2007; Surh, 2002; Prasad et al., 2006a; Iorizzi et al., 2001; Dasgupta and Fowler, Surh, 2004 1997; Higashiguchi et al., 2006). Use of capsaicin in the medical branch of neuro-urology is viewed as a breakthrough, given its use in the treatment of urinary incontinence (Dasgupta and Fowler, 1997); There is indication that the capsaicin is cardioprotective due to effects in platelet aggregation (Wang et al.,

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