CHAPTER ONE

1.0       INTRODUCTION

Intake of tomato and tomato based-products contributes to the absorption of a wide range of carotenoids in human serum and tissues. The prominent carotenoid in tomatoes is lycopene, a pigment principally responsible for the deep-red colour of tomato fruits and tomato products. Fruits and vegetables contain in excess of 40 carotenoids that are routinely absorbed and metabolized by humans (Khachik, 1992).

Tomatoes and tomato products are now being investigated for their potential role in prostate cancer prevention and therapy. This review summarizes the in vitro and invivo evidence as well as the molecular data that show the anticarcinogenic potential of tomatoes.   Raw and processed tomatoes are among the most commonly consumed vegetables. They are rich in the phytochemicals, carotenoids and polyphenols. Lycopene and quercetin are the most abundant carotenoids and flavonols respectively. Canned tomato sauce is the primary source of lycopene whereas the tomato skin is enriched with flavonols. Most epidemiological studies suggest that the consumption of tomatoes and the products in associated with a reduced prostate cancer risk. The health professionals follows-up study found that men who consumed 2 to 4 servings of raw tomatoes per week had a more than 20% reduction in prostate cancer risk compared to men who did not consume tomatoes. High lycopene plasma concentrations were associated with a low incidence of prostate cancer and aggressive prostate cancer in rested case-control study with the physician’s health study. Invitro data show that the compounds found in tomatoes are potent anticarcinogens. Cancer cell growth is inhibited by the polyphenols quercetin, kaempferol and naringerin in a dose dependent manner. These compounds do not have cytotoxic effect. In a rat model of prostate cancer, tomato powder into but not lycopene intake by itself reduced prostate cancer related mortality. This suggests that the compounds in tomatoes have an additive influence on prostate cancer. Lycopenes exist as either the cis or trans isomer. The half-life of lycopene is approximately 10 to 14 days, so it remains in the body during washout period. The trans isomer dominates in tomatoes, between the cis isomer dominates in serum and tissues and during a washout period. Thus, recent intake of lycopenes is reflected in blood concentrations whereas long-term exposure is determined in the tissues. 

Lycopene is a bioactive carotenoid found in many red fruits and vegetables, such as tomatoes, watermelon, pink grapefruits etc. Different fruits, vegetable and their products contain different concentrations of lycopene. This natural red pigment is synthesized exclusive by plants and microorganisms (fungi, bacteria and algae). It facilitates the absorption of light during photosynthesis and also provides protection against photosensitization (Adam et al., 1996) Animals including human being, cannot synthesize lycopene therefore, they obtain lycopene exclusively from diet (Tapiero et al. 2004; Omoni and Aluko, 2005).

Although, tomato contain a lower concentration of nutrients compared to other commercially grow fruits species, they are a major source of lycopene. Lycopene comprises 83% of the total pigment present in tomatoes (Shi et al., 1990). Therefore, the amount of lycopene present in tomatoes other fruits and vegetables vary with variety, degree of ripeness and other dimatic conditions and agricultural practices.

The fraction of vitamin C in the diet that is absorbed and the rate at which the excess is eliminated from the body vary strongly with the dose. Large, randomized clinical trials on the effects of high doses on the general population have not been conducted. Venturi suggested that the antioxidant action of ascorbic acid developed first in the plant kingdom when, about 500 million years ago (mya), plants began to adapt to antioxidant mineral deficient fresh waters of estuaries. Ascorbic acid or vitamin C is a common enzymatic cofactor in mammals used in the synthesis of collagen. Ascorbate is a powerful reducing agent capable of rapidly scavenging a number of reactive oxygen species (ROS). Freshwater fishes also require dietary vitamin C in their diet or they will get scurvy. The most widely recognized symptoms of vitamin C deficiency in fishes are scoliosis, lordosis and dark skin coloration.

The name “carotene” was first coined in the early 19th century by the scientist Wachenroder after he crystallized this compound from carrot roots. Beta-carotene is a member of the carotenoids, which are highly pigmented (red, orange, yellow), fat-soluble compounds naturally present in many fruits, grains, oils and vegetables (green plants, carrots, sweet potatoes, squash, spinach, apricots, and green peppers). Alpha, beta and gamma carotene are considered provitamins because they can be converted to active vitamin A. The carotenes possess antioxidant properties. Vitamin A serves several biological functions including involvement in the synthesis of certain glycoproteins. Commercially available beta-carotene produced synthetically or from palm oil, algae, or fungi. Beta-carotene is converted to retinol, which is essential for vision and is subsequently converted to retinoic acid, which is used for processes involving growth and cell differentiation.

1.1   Objectives of the study

The main objective of this project is to do a comparative analysis (quantitative analysis) on phytochemicals present in tomatoes and some selected tomato products (canned tomato) sold in any common market in Nigeria.

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