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Plants are primary sources of medicines, fibre, food, shelter and other items of everyday use by humans. The roots, stems, leaves, flowers, fruit and seeds provide food for animals and human beings (Hemingway, 2004). Plants serve as indispensable constituents of human diet supplying the body with minerals salts, vitamins and certain hormone precursors in addition to protein and energy (Oyenuga and Fetuga, 1975). Seeds have nutritive value and calorific value which make them necessary in diets (Odoemelam, 2005). Among these plant seeds/leaves, some are referred to and consumed as spices.

Spices are a group of esoteric food adjuncts that have been in use for thousands of years to enhance the sensory quality of foods. They can also be referred to as edible plant substances that possess antioxidative, antiseptic and bacteriostatic substances (Onyeagba et al., 2004) and they can be added to food to delay the onset of deterioration such as rancidity (Lafont et al., 1984).

These spice ingredients impart characteristic flavour, aroma and color to foods (Srinivasan, 2005) while some, like fenugreek, can modify the texture of food. Not only are spices used as flavourings and seasonings, but many are also be used in perfumery, cosmetics and toiletries. In addition, several spices have long been recognized to possess medicinal properties such as tonic, carminative, stomachic antispasmodic and antihelminthic.

2.4.1 Nutrient composition of Spices

Spices are not only used individually, but also in the form of spice mixtures, to suit different tastes and dishes. The protein content in spices varies from 4.5% in rosemary leaves to 31.5% in mustard, and the fat level varies from 0.6% in garlic to 42.6% in mustard. The ash content also varies from 2.3% in marjoram to 16.7% in basil leaves, reflecting high mineral levels in them.

Some spices contain significant levels of vitamins and minerals, which cannot be ignored. A few spices are also rich sources of dietary fiber. Amongst common spices consumed, the dietary fiber is highest (43.3%) in red pepper. Nonetheless, black pepper (27.8%), coriander (36.2%), cumin

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(23.0%), fennel (28.7%), and fenugreek (33.5%) also are rich sources of both soluble as well as insoluble dietary fiber.

The components of spices responsible for the quality attributes have been designated as ‘active ingredients’ and in many instances they are also responsible for the beneficial physiological effects of spices. For instance, Tajkarimi et al. (2010) reported that the presence of eugenol and cinamic aldehyde which have preserving action specific to some spices and essential oils, increases the shelf life of meat products. They act as food preservative and prevent or control growth of micro-organisms, including pathogenic micro-organisms. Thirteen different spices were also evaluated by Kim et al. (2011) and the authors observed that several spices were found to have high levels of antioxidant capacity and total phenolic compounds. Moreover, the antioxidant capacity, total phenolic content and flavonoid contents of the 13 selected spices were different from each other. Among the selected spices, the clove, thyme and rosemary extracts exhibited higher DPPH radical scavenging activities. From their report, clove and turmeric were observed to have the highest total phenolic content and flavonoid content respectively. These results suggest that several spices extracts have potential as possible functional ingredients in meat products.

2.4.2 Health and Safety Aspect of Spices

Extensive animal studies carried out to evaluate the safety aspect of spices have indicated that even at much higher dietary levels (up to 100 times the normal intake), red pepper, black pepper and turmeric have no adverse effects on growth, organ weights, feed efficiency ratio, nitrogen balance, and blood constituents. The salient features of a variety of health beneficial physiological effects of common spices or their active principles are enumerated below.

A. Hypolipidemic/Hypocholesterolemic Effect

Some of the commonly consumed spices were naturally evaluated for a possible hypocholesterolemic action in a variety of experimental situations in both animals and humans by Srinivasan et al. (2004). They reported that spices like fenugreek, red pepper, turmeric, garlic, onion and ginger are effective as hypocholesterolemic agents under various conditions of experimentally induced hypercholesterolemia/hyperlipemia.

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Curcumin and capsaicin, the active ingredients in turmeric and red pepper respectively, are also efficacious at doses comparable to calculated human daily intake. Turmeric and curcumin showed excellent hypocholesteremic effect in experimental animals (Srinivasan, 2005).

According to Lin (1994), the anti-platelet aggregation, the antiplatelet adhesion and the antiproliferation properties of aged garlic extracts appear to contribute more to cardiovascular protection than do the hypolipidemic properties. Apart from the hypocholesterolemic effect of capsaicin, its beneficial effect on overall lipid metabolism under different conditions of lipemia was also reported (Sambaiah and Satyanarayana, 1982; Srinivasan and Satyanarayana, 1988).

B. Antilithogenic Effect

The antilithogenicity of curcumin and capsaicin is considered to be due to lowering of cholesterol concentration and enhancing the bile acid concentration, both of which contribute to lowering of the cholesterol saturation index and, hence, reduce crystallization. In addition to their ability to lower the cholesterol saturation index, the antilithogenecity of these spice principles was also be due to their influence on biliary proteins (Hussain and Chandrasekhara,1994).

C. Antidiabetic potential

Diet has been recognized as a corner stone in the management of diabetes mellitus. As part of the dietary treatment of diabetes, spices, have also been examined in this direction and their efficacy reviewed. A considerable number of human experiments have also been carried out on this aspect in addition to experimentally induced animal diabetic models. Fenugreek, turmeric, or its active principle curcumin, onion or its active principle allyl propyl disulfide, garlic, and cumin were observed to improve glycemic status in diabetic animals noninsulin dependent diabetes mellitus (NIDDM) patients (Srinivasan, 2005). Garlic and onion are two other spices that have been widely used for their antidiabetic potential. Both these spices were reported to be hypoglycemic in different diabetic animal models and in limited human trials. The hypoglycemic potency of garlic and onion has been attributed to the sulfur compounds, namely di (2-propenyl) disulfide and 2-propenylpropyl disulfide, respectively (Kumudkumari et al., 1995; Augusti and Sheela, 1996).

D. Digestive Stimulant Action

Spices are well recognized to stimulate gastric function. They are generally believed to intensify salivary flow and gastric juice secretion and, hence, aid digestion. Spice, like turmeric, was

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reported to reduce the pungency of the food and irritation to stomach. Turmeric has the property of increasing the mucin content of the gastric juice. Spices such as ginger, mint, ajowan, cumin, fennel, coriander, and garlic are used as ingredients of commercial digestive stimulants as well as of home remedies for digestive disorders, like, flatulence, indigestion, and intestinal disorders (Platel and Srinivasan, 2004).

Animal studies have also revealed that a good number of spices, when consumed through diet, bring about an enhanced secretion of bile with a higher bile acid content, which plays a vital role in fat digestion and absorption (Sambaiah and Srinivasan, 1991; Platel and Srinivasan, 2000).

Such spices include curcumin (turmeric), capsaicin (red pepper), ginger, cumin, coriander, ajowan, fenugreek, mustard, onion, and tamarind. Spices such as curcumin, capsaicin, piperine, ginger and mint have also been reported to stimulate pancreatic digestive enzymes like lipase, amylase, trypsin, and chymotrypsin, which play a crucial role in food digestion (Platel and Srinivasan, 2001). Thus, many of the common spices act as digestive stimulants by enhancing biliary secretion of bile acids, which are vital for fat digestion and absorption and by stimulating the activities of pancreatic and intestinal enzymes involved in digestion.

E. Antioxidant property

Antioxidants can delay or inhibit the oxidation propagation of oxidizing chain reactions in the oxidation process (Zheng and Wang, 2001).The antioxidant properties of spice principles of capsaicin, curcumin, and eugenol, have been documented in animal studies by Reddy and Lokesh (1994). These compounds inhibited lipid peroxidation by quenching oxygen free radicals and by enhancing the activity of endogenous antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidase, and glutathione transferase.

F. Antimutagenic and Anticarcinogenic Property

Food mutagens are formed under certain cooking and processing conditions. These harmful products can be modified by the presence of antimutagens in the foods. Spices that have anti-oxidant property can function as antimutagens. Since mutation is one of the mechanisms by which cancer is caused, an antimutagenic substance is likely to prevent carcinogenesis. Studies on smokers revealed that administration of curcumin (1.5 g/day) for 30 days resulted in a significant reduction in the urinary excretion of mutagens (Polasa et al., 1991). Shalini and Srinivas (1990) also reported that turmeric protected DNA against lipid peroxide-induced

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damage and against fuel smoke condensate-induced damage. Similar to curcumin, the active principle in turmeric, eugenol, found in cloves and sesamolinol isolated from sesame seeds are reported to produce antimutagenic effect by protecting the cell from damage to its DNA.

Chemically, most of these compounds have a common phenolic structure, which helps in the detoxification of xenobiotics. Research on mustard has also shown to have antimutagenic properties (NIN Annual Report, 1993–1994).

Epidemiological studies have shown that higher intake of allium products (e.g garlic) is associated with reduced risk of several types of cancers, especially stomach and colorectal (Fleischauer and Arab, 2001). Pungent vanilloids, especially [6]-gingerol, present in ginger (Zingiber officinale) have been found to possess potential chemopreventive activities. [6]-gingerol, a pungent phenolic compound present in ginger is also reported to be a potent inhibitor of nitrous oxide (NO) synthesis and also an effective protector against peroxynitrite-mediated damage in macrophages (Ippoushi et al., 2003). These bioactive compounds of spices exert their anticarcinogenic effect by deactivating the carcinogens or by enhancing the tissue levels of protective enzymes in the body.

G. Anti-Microbial Activity

Garlic and onions have been reported to possess anti-microbial property. The sulfur-containing compounds from these plants act against both gram positive and gram negative bacteria (Carson, 1987). The extracts of garlic and onion are known to inhibit growth of many pathogenic fungi belonging to genera Aspergillus, Candida and other species (Carson, 1987). Other spices like nutmeg, saffron, cumin, and thyme also have anti-microbial potential.

In view of the beneficial physiological effects that spices exhibit, these food adjuncts deserve to be considered as natural and necessary components of our daily nutrition beyond their role in imparting taste and flavour to our food.

2.5 Some common spices