Abstract
This study evaluated the phytochemical, antioxidant and antimicrobial activities of Mucuna pruriens seeds. Extractions were carried out with ethanol, methanol, and petroleum ether, water Acetone. The preliminary phytochemical study of the extracts of seed of Mucuna pruriens revealed the presence of alkaloids, Hydrogen cyanide, saponin, flavonoids, phenols, and tannins. The highest level of phytochemical screening was observed in the hydrogen cyanide which was signified with +++ (highly present) while the antioxidant screening revealed the high presence of nitric oxide radical scavenging and protein signified with +++ (Highly present). The extracts were tested against Staphylococcus aureus, Bacillus subtilis and Escherichia coli using agar well diffusion method. The petroleum ether, methanol, ethanol, water and acetone extracts of Mucuna pruriens seed possess various degrees of significant inhibitory effect against the tested organism. The highest antibacterial effect was observed in the ethanol extract against Staphylococcus aureus, (13mm inhibition zone) while the lowest inhibition zone of antibacterial effect was observed in the water extract against Staphylococcus aureus (7mm inhibition zone). Also the highest antifungal effect was observed in methanol extract against Aspergillus niger (13mm inhibition zone), Ethanol against Saccharomyces cerevisiae and Mucor (12mm inhibition zone) while the lowest antifungal effect was observed in the water extract against Aspergillus niger and Aspergillus flavus (1mm inhibition zone). Broth dilution method was used to estimate Minimum inhibition concentration (MIC) against the selected pathogens. The results shows that the methanol extract of Mucuna pruriens seed has antifungal effect while the ethanol extract has antibacterial effect and may be used in treatment of some diseases. The results of the study suggest that adequate fermentation process should be carried out in the preparation of Mucuna pruriens seeds because of the high level of hydrogen cyanide.
TABLE OF CONTENTS
S/N
Title Pages
Title page i
Dedication ii
Certification iii
Acknowledgements iv
Table of contents v
List of table’s vii
List of Figures viii
Abstract ix
CHAPTER ONE
1.0
Introduction 1
1.1 Aim and Objective of the
Study 4
CHAPTER TWO
2.1 Literature
Review 5
2.2 Origins
and Early Uses 6
2.3 Taxonomy
and Characteristics of Mucuna pruriens 13
2.3.1 Classification 13
2.3.2 Species
Description 15
2.4 Current
Uses of Mucuna pruriens 16
2.4.1 Antimicrobial
Activity 16
2.4.2
Nutraceutical Versatility 16
2.4.3 Antioxidant
property 18
2.4.4 Antivenin
property 18
2.4.5 Fertility-enhancing property 19
2.4.6 Growth-promoting property 20
2.3.7 Hypoglycemic property 20
2.4.8 Anthelmintic property 20
2.4.9 Mucuna pruriens
as a Food and Feed Source 21
2.5 Nutritional Value 23
2.5.1 Protein Concentration 23
2.5.2 Other Nutrients 25
2.8 Comparison
to Other Legumes 25
2.9 Antinutritional and Toxic
Properties 27
2.9.1 Tannins 28
2.9.2 Proanthocyanidins 29
2.9.3 Hydrolyzable tannins 30
2.9.4 L-Dopa
31
CHAPTER
THREE
3.0 Materials and Methods
33
3.1 Materials 33
3.1.2 Sample
collection
33
3.2 Methods 33
3.2.1 Sample Preparation 33
3.2.2 Solvent
extraction of the sample 33
3.3 Phytochemical
Analysis of Mucuna Pruriens Powder 34
3.3.1 Determination of Hydrogen
cyanide 34
3.3.2 Determination of Phenol 34
3.3.3 Determination of Tannin 34
3.3.4 Determination of Alkaloid 35
3.3.5 Determination of Saponin 36
3.3.6 Determination of Flavonoid 37
3.4 Detertmination of Antioxidant
Properties of Mucuna pruriens 37
3.4.1
Protein Determination 37
3.4.2 Nitric oxide radical scavenging
activity 38
3.4.3 Iron chelating activity 39
3.5 Antimicrobial Determination
of Mucuna pruriens 39
3.5.1 Antibacterial activity of Mucuna pruriens 39
3.5.2 Antifungal activity of Mucuna pruriens 40
3.5.3
Minimum inhibitory
concentration 40
3.6 Statistical analysis 40
CHAPTER FOUR
4.1
Results 41
CHAPTER FIVE
5.1
Discussion 48
5.2
Conclusion 50
5.3 Recommendation 50
5.4 Suggestion
for future study. 51
References Appendix
List of Tables
Tables Title
Pages
1 Scientific
and common names of Mucuna pruriens 14
2 Ethnobotany:
worldwide uses or functions of Mucuna pruriens 17
3 Mineral concentration of
different cultivars of Mucuna (mg/100g
DM) 26
4 Phytochemical
Properties of Mucuna Pruriens 42
5
Antioxidant Properties of Mucuna Pruriens 43
6 Showing the minimum
inhibitory concentration (MIC) of Bacterial Isolates. 46
7 Showing the minimum
inhibitory concentration (MIC) of fungal isolates. 47
List of figures
Figures Title pages
1 Antibacterial
activity of various extract of Mucuna
pruriens seeds on selected organisms. 44
2 Antifungal activity of various
extract of Mucuna
pruriens seeds on selected
organisms.
45
CHAPTER ONE
1.0 INTRODUCTION
Mucuna pruriens is an annual climbing
legume indigenous to tropical regions with numerous uses as a food, feed, and
nutraceutical. Like many other legumes, however, it has molecular components
that can adversely affect its nutritional value, but the ability of these molecules
to inhibit enzymes, to selectively bind and enter the circulatory system may be
useful in pharmacology. Therefore, nutritionists and medical researchers have
contrasting views about the toxicity of the genus.
According
to Szabo and Tebbett (2002) the major drawback of Mucuna, which has
compromised its usefulness as a food source for either humans or livestock, is
associated with its chemical concentration. Mucuna contains novel
alkaloids, saponins, and sterols (Manyam et
al., 2004) and a high concentration of L-Dopa. In addition, serotonin and a
number of indolic alkaloids structurally related to serotonin have been
reported in various parts of the Mucuna plant, several of which have
hallucinogenic properties of considerable strength (Szabo and Tebbett, 2002).
It would, however, be unlikely for these low-level alkaloids to have any effect
on human and animal consumers because their absorption across the
gastrointestinal tract is negligible (Szabo, 2003).
According
to Taylor (2004) beans of Mucuna are not only high in protein, but also
in non-structural carbohydrates, lipids, and minerals. In South and Mid
America, Mucuna beans have been roasted and ground to make a coffee
substitute and the bean is also cooked and eaten as a vegetable. Mucuna is
also one of the most remarkable green manures as it can add up to 30 ton/ha of
organic matter to soils (Pretty et al.,
1998).
The
crop has a long history of use in Indian medicine and traditional medical
practice in several countries where it is used to treat a wide variety of
ailments including 12 Parkinson’s
disease (Manyam and Sanchez-Ramos, 1999; Nagashayana et al., 2001). However, many of such uses are based on anecdotal
healing properties that require verification and scientific validation.
The
genus Mucuna,
belonging to the Fabaceae family, sub family Papilionaceae, includes
approximately 150 species of annual and perennial legumes. Among the various
under-utilized wild legumes, the velvet bean Mucuna pruriens is
widespread in tropical and sub-tropical regions of the world. It is considered
a viable source of dietary proteins (Janardhanan et al., 2003; Pugalenthi et
al., 2005) due to its high protein concentration (23–35%) in addition its
digestibility, which is comparable to that of other pulses such as soybean,
rice bean, and lima bean (Gurumoorthi et
al., 2003). It is therefore regarded a good source of food.
The
dozen or so cultivated Mucuna
spp. found in the tropics probably result
from fragmentation deriving from the Asian cultigen, and there are numerous
crosses and hybrids (Bailey and Bailey, 1976). The main differences among
cultivated species are in the characteristics of the pubescence on the pod, the
seed color, and the number of days to harvest of the pod. “Cowitch” and
“cowhage” are the common English names of Mucuna types with abundant, long
stinging hairs on the pod. Human contact results in an intensely itchy
dermatitis, caused by mucunain (Infante et
al., 1990). The nonstinging types, known as “velvet bean” have appressed,
silky hairs. The plant Mucuna
pruriens, widely known as “velvet bean,” is a
vigorous annual climbing legume originally from southern China and eastern
India, where it was at one time widely cultivated as a green vegetable crop
(Duke, 1991). It is one of the most popular green crops currently known in the
tropics; velvet beans have great potential as both food and feed as suggested
by experiences worldwide. The velvet bean has been traditionally used as a food
source by certain ethnic groups in a number of countries. It is cultivated in
Asia, America, Africa, and the Pacific Islands, where its pods are used as a
vegetable for human consumption, and its young leaves are used as animal
fodder.
The
plant has long, slender branches; alternate, lanceolate leaves; and white
flowers with a bluish-purple, butterfly shaped corolla. The pods or legumes are
hairy, thick, and leathery; averaging 4 inches long; are shaped like violin
sound holes; and contain four to six seeds. They are of a rich dark brown
color, and thickly covered with stiff hairs. In India, the mature seeds of Mucuna bean are traditionally
consumed by a South Indian hill tribe, the Kanikkars, after repeated
boiling to remove anti-nutritional factors. Most Mucuna spp. exhibit reasonable
tolerance to a number of abiotic stresses, including drought, low soil
fertility, and high soil acidity, although they are sensitive to frost and grow
poorly in cold, wet soils (Duke, 1991). The genus thrives best under warm,
moist conditions, below 1500 m above sea level, and in areas with plentiful
rainfall. Like most legumes, the velvet bean has the potential to fix
atmospheric nitrogen via a symbiotic relationship with soil microorganisms.
Mucuna spp. have been reported
to contain the toxic compounds L-dopa and hallucinogenic tryptamines, and
anti-nutritional factors such as phenols and tannins (Awang et al., 1997). Due to the high
concentrations of L-dopa (4–7%), velvet bean is a commercial source of this
substance, used in the treatment of Parkinson's disease. The toxicity of
unprocessed velvet bean may explain why the plant exhibits low susceptibility
to insect pests (Duke, 1991). Velvet bean is well known for its nematicidic
effects; it also reportedly possesses notable allelopathic activity, which may
function to suppress competing plants (Gliessman et al., 1991). Despite its toxic properties, various species of Mucuna are grown as a minor food
crop. Raw velvet bean seeds contain approximately 27% protein and are rich in
minerals (Duke, 1991). During the 18 and 19 centuries, Mucuna was grown widely as a
green vegetable in the foothills and lower hills of the eastern Himalayas and
in Mauritius. Both the green pods and the mature beans were boiled and eaten.
In Guatemala and Mexico, M. pruriens
has for at least several decades been
roasted and ground to make a coffee substitute; the seeds are widely known in
the region as “Nescafé,” in recognition of this use.
1.1 AIMS AND OBJECTIVES OF THE STUDY
This
review focuses on the following aspects of Mucuna
pruriens: taxonomy and physical characteristics,
nutritional value, antinutritional and toxic properties, methods for
detoxifying the bean and their impact on its nutritional value.
Specific
Objectives include;
1. to
identify the phytochemical compounds of Mucuna
pruriens
2. to identify the antioxidant components of Mucuna pruriens
3. to
determine the antimicrobial activity of Mucuna pruriens extract on some
bacteria and fungi
4. to determine the minimum inhibitory concentration
(MIC) of the Mucuna pruriens seed extracts.
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