PROXIMATE AND PHYTOCHEMICAL COMPOSITION OF AFRICAN YAM BEAN (SPHENOSTYLIS STENOCARPA) AND ITS EFFECT ON THE LIPID PROFILE OF HYPERCHOLESTEROLEMIC RATS

ABSTRACT

The  study  examined  the  proximate  and  phytochemical  (saponins,  tannins,  phytate  and flavonoid) composition of roasted cream coloured African yam bean (AYB) flour  and the lipid profile of hypercholesterolemic  rats fed diets supplemented  with African  yam bean. Different diets were formulated using the AYB flour. Group 1 consisted of the normal control rats (untreated rats), group 2 consisted of the hypercholesterolemic  group of rats that were untreated. Groups 3-6 consisted of rats fed rat chow with 5%, 10%, 15% and 20% AYB flour supplementation,   respectively.   Proximate   analysis   was   done   using   AOAC   methods. Phytochemical  and biochemical analyses were  done in duplicates using standard methods. The proximate  analysis showed that AYB  flour contain 4.94% moisture, 27.66% protein,

4.29%  fat,  3.66%  ash,  9.57%  crude  fibre  and  49.88%  carbohydrate.  The  phytochemical analysis showed  0.77mg/100g  saponins,  42.07mg/100g  tannins,  9.08mg/100g  phytate  and

1.01mg/100g  flavonoid.  Total  cholesterol  level  for  the  different  supplementation  groups showed  significant  decrease  (p<0.05)  with  20%  supplementation  showing  the   highest decrease (38.70%). Triglyceride levels decreased significantly (p<0.05) across all the groups. The   5%   AYB   supplementation   showed   the   highest   decrease   (35.63%)   and   20% supplementation the lowest decrease (28.01%). Low density lipoprotein (LDL) levels of the rats  significantly  (p<0.05)  decreased  across  the  groups.  The  control  group  also  showed

50.34%  decrease  in  LDL  but  10%  AYB  supplementation  showed  the  highest  decrease (61.29%).  Serum  high  density  lipoprotein  (HDL)  concentration  increased  significantly (p<0.05)  after  supplementation  with  AYB.  The  20%  AYB  supplementation  showed  the highest percentage  increase  (22.85%)  relative  to the  other groups. There were significant decreases  in serum  total  cholesterol,  LDL  cholesterol,  triglyceride  and  increase  in  HDL cholesterol for the groups with AYB supplementation.

CHAPTER ONE INTRODUCTION

1.1     Background to the Study

Hypercholesterolemia is the presence of high levels of cholesterol in the blood, and is a form of  “hyperlipidemia”  (elevated  levels  of  lipids  in  the  blood)  and  “hyperlipoproteinemia” (elevated levels of lipoproteins in the blood) (Durrington, 2003).This is a major risk factor for cardiovascular  disease  especially coronary heart  disease  (Mudabmbi  & Rajagopal,  2007). Cholesterol is the main sterol found in body tissues. Since cholesterol is insoluble in water, it is transported in the blood plasma bound to protein particles (lipoproteins). Lipoproteins are classified  by  their  density;  very  low  density  lipoprotein  (VLDL),  intermediate  density lipoprotein  (IDL),  low  density  lipoprotein  (LDL)  and  high  density  lipoprotein  (HDL) (Biggerstaff & Wooten, 2004). All the lipoproteins carry cholesterol, but elevated levels of the lipoproteins other than HDL (termed non-HDL cholesterol), particularly LDL-cholesterol is associated with an increased risk of atherosclerosis and coronary heart disease (Carmena, Duriez & Fruchart, 2004). Dietary intervention trials have shown that the reduction of serum total  and  LDL  cholesterol  concentration   is  beneficial  for  the   reduction  of  coronary atherosclerosis in people with or without coronary heart disease (Gould, 1992; Ornish, 1998). Cardiovascular disease (CVD) is a class of diseases that  involve the heart or blood vessels (arteries and veins) (Maton, 1993). It refers to any  disease that affects the cardiovascular system, principally cardiac disease, vascular diseases of the brain and kidney, and peripheral arterial disease (Kelly & Fuster, 2010). According to the World Health Organization, chronic diseases are responsible for 63% of all deaths in the world, with cardiovascular disease as the leading cause of death (WHO, 2011). An estimated 17.3 million people died from CVD’s in

2008. Over 80% of CVD deaths take place in low- and middle-income countries. By 2030, almost 23.6 million people will die from CVDs (WHO, 2011). There are many  causes of cardiovascular  disease but the most common are atherosclerosis  and/or hypertension.  The different   types   of   cardiovascular    disease   include   coronary   heart   disease    (CHD), cardiomyopathy,    hypertensive   heart   disease,   heart   failure,   cor   pulmonare,    cardiac dysrhythmias,  inflammatory  heart  disease  (endocarditis,  inflammatory  cardiomegaly,  and myocarditis),  valvular  heart disease, stroke or  cerebrovascular  accident, peripheral  arterial disease. CVD typically involves the coronary arteries and thus is frequently termed coronary heart disease (CHD) or  coronary artery disease (CAD). The risk factors of cardiovascular disease  are  in  addition  to  high  fat  diet;  age,  gender,  high  blood  pressure,  high  blood cholesterol levels, tobacco, smoking, excessive alcohol consumption, family history, obesity, lack of physical activity, psychosocial factors and diabetes mellitus (Kelly & Fuster, 2010). Evidence shows that the Mediterranean diet improves cardiovascular  outcomes (Walker  & Reamy,  2009).  The  Mediterranean  diet  is  made  up of high  olive  oil consumption,  high consumption of legumes, unrefined cereals, fruits, and vegetables, moderate consumption of dairy products, and moderate to high consumption of fish, low consumption of meat and meat products  and  moderate  wine  consumption.  A 10-year  study published  in the  Journal  of American Medical Association (JAMA) found that  adherence to a Mediterranean diet and healthful  lifestyle  was  associated  with  more  than  a  50%  lowering  of  early  death  rates (Knoops et al., 2004).

Legumes have benefits in terms of reduced risk of CHD. Legumes or dry beans have been shown to improve  serum lipid profiles  in patients with CHD (Anderson &  Major, 2002; Bazzano,  Thompson,  Tees,  Nguyen  & Winham,  2009)  and  a growing  body of evidence supports the positive effects dietary legume consumption confers on  health, particularly in relation  to risk of CHD.  Epidemiological  studies  support the  cardio protective  effects  of legumes as part of a healthy diet. In particular, one study examined the relationship between beans consumption and occurrence of CVD and reported that 1 serving per day of beans was associated  with  a  38%  lower  risk  of  myocardial  infarction  (Kabagambe,  Baylin,  Ruiz- Narvarez, Siles & Campos, 2005). A second study by Bazzano, He & Ogden (2001) reported that individuals consuming legumes at least four times per week had a  22% lower risk of heart  disease  than  individuals  consuming  legumes  less than  once  per week.  Majority of legume studies have examined the relationship  between soybeans and heart disease. Some studies using navy beans and chickpeas have been conducted. In an early report, Anderson and Major  (2002) demonstrated  that  consumption  of navy beans  in tomato  sauce (baked beans)  for  21  days  decreased  serum  total  cholesterol  (TC)  and  low-density  lipoprotein cholesterol  (LDL-C)  concentrations  in  hypercholesterolemic  men  (Anderson,  Gustafson, Spencer, Tetyen & Bryant, 1990). A research by Finley, Burrel, and Reeves (2007) reported that pinto beans consumption is also favourable. Cowpea commonly consumed in Nigeria has been  linked  to  present  significant  reductions  in  plasma  total  cholesterol  and  non-HDL cholesterol (Frota, Mendonca, Saldiva, Cruz, & Areas, 2008).  As Liu (2006) reported, diets with low glycemic index are associated with a reduced risk for the development of diabetes mellitus, obesity and cardiovascular disease.

All legumes contain phytochemicals which play metabolic roles in humans who  frequently consume these foods. Phytochemicals, also referred to as phytonutrients, are found in fruits, vegetables, whole grains, legumes, beans, herbs, spices, nuts, and seeds  and are classified according to their chemical structures and functional  properties.  Phytochemicals  are non- nutritive  plant chemicals  that  have protective  or disease  preventive  properties.  There  are many phytochemicals  and each works differently.  Presence of phytochemical  components such      as      phytohemagglutinins,       tannins,       phytic      acid,      saponins,      protease inhibitors, oligosaccharides and phytoestrogens in food legumes has both health benefits and adverse effects. These are some possible action; antioxidant, hormonal action, stimulation of enzymes, interference with DNA replication, anti-bacterial effect and physical actions. These

biologically active compounds in food legumes also have immense potential in biomedical application.     On     the     other     hand,     phytochemicals     have     adverse     effects     as they limit the digestibility  of proteins  and carbohydrates  or reduce the  bioavailability  of certain  nutrients,  interfere  with  normal  growth,  reproduction  and  flatulence  production. Moreover,  phytoestrogens  have been  linked  with  infertility  problems.  The  synergistic  or antagonistic effects of mixtures of these phytochemicals from food legumes, their interaction with  other  components  of  the  diet  and  the  mechanism  of their  action  have  remained  a challenge with regard to understanding  the role of phytochemicals  in health and diseases. These have been associated with numerous health benefits, including reduced cardiovascular and renal disease risks,  health care treatments  including anti-aging,  enhancement  of brain function, and lower glycemic index for persons with diabetes, increased satiation and cancer prevention. Dietary intake of phytochemicals may provide health benefits, protecting against numerous diseases or disorders, such as coronary heart disease, diabetes, high blood pressure and inflammation (Bouchenak & Lamri-Senhadj, 2013).

Phytic acid (phytate), a type of phytochemical classified as anti-nutrient is found in  many types of plant foods, such as grains, legumes (including peanuts and soybeans),  nuts, and seeds.  In  legumes  and  seeds,  phytic  acid  resides  almost  entirely  in  the   endosperm (Schlemmer, Frolich, Prieto & Grases, 2009). Phytic acid has shown some capacity to reduce cholesterol and triglycerides, and positively impact the glycemic  response of certain foods (Lee, Park and Chun, 2007). In some cases, phytic acid seems to have an ability to slow down a potential  blood  sugar spike  following  the  ingestion  of  certain  high-carbohydrate  foods. Again, this may explain why high-fiber  foods  have  been associated  with improved  blood sugar control. The potential benefits of phytic acid occur in instances with high dietary phytic acid intake. However, a high intake has also been associated with reduced mineral absorption. So, in order for us to get the  best of both worlds, it’s important to discover some ways in

which we can minimize the negative effects while maximizing the beneficial effects.  One way we can do this (specifically  in regards to iron) is by incorporating  more  vitamin C (ascorbic acid) into our diet. These two work well together, with vitamin C placing iron in a chemical  state  that  is  more  readily  absorbed  by  the  body  (Hummers  and  Offeman,

1958).Preparation methods such as soaking, germinating, or fermenting can be very effective in reducing the amount phytic acid present in foods.

Tannin is an astringent,  bitter plant polyphenolic  compound  that binds to and  precipitates proteins and various other organic compounds including amino acids and alkaloids. Tannins have traditionally been considered anti-nutritional but it is now known that their beneficial or anti-nutritional properties depend upon their chemical structure  and dosage. Recent studies have demonstrated that products containing chestnut tannins included at low dosages (0.15–

0.2%) in the diet of chickens may be beneficial (Schiavone, Guo and Tassone, 2008). Most legumes contain tannins. Red-coloured beans contain the most tannins, and  white-coloured beans have the least (Reed, 1995). There is a growing consensus for the hypothesis that the specific intake of food and drink containing relatively high  concentrations  of polyphenols may play a meaningful role in reducing the risk of cardiovascular disease (Ashutosh, 2003).

Saponins are a class of chemical compounds found in abundance in various plant  species. Saponins  are  attracting  considerable  interest  as  a result  of  their  diverse  properties,  both deleterious  and  beneficial.  Clinical  studies  have  suggested  that  these  health-promoting components, saponins, affect the immune system in ways that help to protect the human body against  cancers,  and also  lower  cholesterol  levels.  Saponins  decrease  blood  lipids,  lower cancer risks, and lower blood glucose response.  The detergent qualities of saponins allow them to bind to bile and prevent its reabsorption. Once bound to saponins, cholesterol leaves the body in waste. A lower cholesterol level means less risk of heart attack or stroke.

Flavonoids (or bioflavonoids)  (from the Latin word flavus meaning yellow, their color  in nature) are a class of plant secondary metabolites. Flavonoids were referred to as Vitamin P (Benthsath, Rusznyak and Szent-Gyorgyi, 1937) probably because of the effect they had on the permeability of vascular capillaries. Flavonoids have been shown to have a wide range of biological and pharmacological activities in in vitro studies. Examples include anti-allergic, anti-inflammatory, antioxidant, anti-microbial  (antibacterial,  antifungal, and antiviral), anti- cancer, and anti-diarrheal activities (Yamamoto and Gaynor, 2001; Cushnie and Lamb, 2011; Friedman, 2007; Manner et al., 2013). Inflammation has been implicated as a possible origin of numerous local and systemic diseases, such as cancer, cardiovascular disorders, diabetes mellitus, and celiac disease (Manach, Mazur and Scalbert, 2005; Babu, Liu and Gilbert, 2013; Ravishankar, Rajora, Greco and Osborn, 2013).

Preliminary  studies indicate that flavonoids may affect anti-inflammatory  mechanisms  via their ability to inhibit reactive oxygen or nitrogen compounds (Izzi et al., 2012). Flavonoids have also been proposed to inhibit the pro-inflammatory activity of enzymes involved in free radical production, such as cyclooxygenase, lipoxygenase or inducible nitric oxide synthase, and  to  modify  intracellular   signaling  pathways  in  immune   cells  (Izzi  et  al.,  2012). Procyanidins, a class of flavonoids, have been shown in preliminary research to have anti- inflammatory mechanisms including modulation of the arachidonic acid pathway, inhibition of gene transcription, protein expression and  activity of inflammatory enzymes, as well as secretion of anti-inflammatory mediators  (Martinez-Micalo  et al., 2012). Among the most intensively  studied  of  general  human  disorders  possibly  affected  by dietary  flavonoids, preliminary  cardiovascular  disease  research has revealed the following mechanisms  under investigation in patients or normal subjects (van Dam, Naidoo and Landberg, 2013; Tangney and Rasmussen, 2013):

     inhibit coagulation, thrombus formation or platelet aggregation

     reduce risk of atherosclerosis

     reduce arterial blood pressure and risk of hypertension

     reduce oxidative stress and related signaling pathways in blood vessel cells

     modify vascular inflammatory mechanisms

     improve endothelial and capillary function

     modify blood lipid levels

     regulate carbohydrate and glucose metabolism

     modify mechanisms of aging

Other components of the legume such as the protein, carbohydrate, fat, and dietary fibre have also been shown to improve CVD risk factors. The low content of saturated fatty acids and high content of fiber make pulses a good choice for a healthy diet. Dry beans are essentially fat-free and act to displace fat from the diet. Many of them have moderate amounts of oil that is predominantly unsaturated. Their complex carbohydrates together with dietary fiber result in low glycemic indexes of legumes and legume products, and play an important role in the prevention of diabetes.  Dry beans contain a mixture of  soluble  fiber, which significantly lowers  cholesterol  and  blood  sugar  concentrations,  and  insoluble  fiber,  which  aids  in gastrointestinal  function.  Dietary fiber has major  protective  effects  against  atherosclerotic cardiovascular disease (Anderson, Deakins,  Floore, Smith & Whitis, 1990). Epidemiologic data suggest that intake of complex carbohydrates and dietary fiber is inversely related to coronary artery disease (Anderson et al., 1990). Dietary fiber intake also slows development of  atherosclerosis   in  animal  models.   Whereas   soluble   fiber  clearly  decreases   serum cholesterol and LDL-cholesterol concentrations (Anderson et al., 1990), the inverse relation between dietary fiber intake and coronary artery disease appears to be independent of serum cholesterol   concentration.   Findings   from   epidemiologic   studies   show   a   significant

relationship  between increased protein intake and lower risk of hypertension and  coronary heart disease. In experimental animal models feeding a variety of different plant proteins is associated  with  lower  serum  cholesterol  concentrations  than  with  feeding  a  variety  of different   animal  proteins   (Carroll,   1982).   Legume   proteins   appear   to  have   specific hypocholesterolemic  effects. Less is known about the effects of other commonly consumed varieties, especially African yam beans (AYB) on heart diseases (Anderson & Major, 2002; Anderson, Smith, & Washnock, 1999).

African  Yam  bean  (AYB)  (Sphenostylis  stenocarpa)  is  an  herbaceous  leguminous  plant occurring throughout tropical Africa (Porter, 1992) and grows during the wet season (Allen & Allen,  1981).  It is often cited  among the lesser-known  and underexploited  species  (Ene- Obong & Okoye, 1992; Bennett-Lartey, Ayensu, Monma, & Ito, 1993). It is cultivated both for  the  seeds  and  tubers  because  of its  valuable  and  prominent  source  as plant  protein (Nwodo  & Nwinyi,  2012). Okeke,  Ene-Obong,  Uzoegbuna,  Ozioko  and Kuhnlein (2008) reported that AYB has medicinal value. According to Ngwu, Ndiokwelu, Ibaro and Nwachi (2012),  AYB  showed  a significant  reduction  in  the  fasting  blood  sugar,  blood  pressure, appetite, urination, foot numbness and itching of diabetics in a rural community. Uguru and Madukaife (2001) who did a nutritional evaluation of forty-four genotypes of AYB reported that the crop is well balanced in essential amino acids and has higher amino acid content than pigeon pea, cowpea and bambara groundnut. The nutritional values of its whole and dehulled seeds have been reported (Masdac & Jerums, 2004). Nutritionally, AYB compares favourably with the  cowpea  bean  which  has been  found  to reduce  blood  cholesterol.  Cowpea  bean contains 53.3% carbohydrates, 25.9% proteins, and 2% fat (Frota et al., 2008) while AYB has

62.6% carbohydrate, 19.5% protein and 2.5% fat (Okigbo, 1973). The aim of this study is to investigate  the  proximate  and  phytochemical   constituents  of  AYB  and  its   effect  on hypercholesterolemia.

1.2     Statement of the Problem

This study is hinged on the problem of hypercholesterolemia  and its adverse effects. Little effort has been made on the management of hypercholesterolemia through diet diversification programs especially using indigenous crops. A diet-based systemic approach to abolish these health  disparities  is  desirable  because  it  will  assure  the  long-term  solutions  against  the existing menace (Butt, Shahzadi, Sharif & Nasir, 2007). Recent studies suggest plant-based diets  may  be  more  effective  for  weight   loss,  blood  sugar  control,  and  reduction  of cardiovascular risk factors, particularly blood cholesterol. Legumes have benefits in terms of reduced risk of coronary heart disease due to their many components such as phytochemicals. There are many phytochemicals and each work differently. The synergistic or antagonistic effects of mixtures of these phytochemicals from food legumes, their interaction with other components of the diet and the mechanism of their action have remained a challenge  with regard to understanding the role of phytochemicals in health and diseases. Dietary intake of phytochemicals   may  provide  health  benefits,  protecting  against  numerous  diseases  or disorders,  such as coronary heart disease, diabetes, high blood pressure  and  inflammation (Bouchenak & Lamri-Senhadj, 2013).

High levels of lipids in the form of cholesterol  (LDL)  cause  heart disease,  stroke,  poor circulation and kidney disease. High levels of lipids in the blood are due to the consumption of foods high in fat, or due to an inherited  disorder.  It could also  be  caused by medical conditions  such  as  diabetes,  obesity,  hyperthyroidism,  alcoholism,  kidney  disease,  liver disease and stress. The best way to reduce lipid levels in the blood is to eat less fat, exercise regularly and loose weight if necessary (American Academy of Family Physicians, 1998). AYB is highly nutritious with low fat, high protein, mineral and dietary fiber (Ene-Obong & Carnovale, 1992). The potential role of AYB consumption on the prevention and treatment of chronic diet-related non communicable diseases such as obesity, diabetes, hypertension and cardiovascular diseases has been suggested (Oshodi, Ipinmoroti & Adeyeye, 1997; Onyechi & Nwachi, 2008; Alozie, Udofia, Lawal & Ani, 2009).

This study seeks to determine the proximate and phytochemical composition of AYB and its effect on hypercholesterolemic rats.

1.3      Objective of the study

1.3.1    General Objective: The broad objective of the study is to determine the proximate and phytochemical composition of African Yam Bean and its effect on the lipid profile of hypercholesterolemic rats.

1.3.2    Specific Objectives: The specific objectives of the study were to:

1.    assess the proximate composition of the flour;

2.   assess some phytochemical constituents of the flour (saponins, phytate, tannins and flavonoid);

3.   determine the serum total cholesterol, triglyceride, low density lipoprotein, and high density lipoprotein of adult Wister rats and

4.   determine the effect of roasted AYB flour on the lipid profile of the adult Wister rats.

1.4     Significance of the study

The result of this study will generate scientific evidence that will be used by dietitians and other health care professionals in dietary counseling and for prevention and management of non communicable diseases (NCDs). This will be a means of diversification and upgrading AYB. It will provide basic data and information for sustainable commercial exploitation and increased use of the legume. The findings would increase the food use of AYB which will consequently increase the production of AYB by farmers and strengthen the food security of the people. It will create more  areas  of research based on AYB. It will also revitalize the place of AYB in the food system.

₦8,000.00 – DOWNLOAD FULL PROJECT DOWNLOAD FULL PROJECT Added to cart

---

---

---

---

Related Project Topics :