This is not the document you are looking for? Use the search form below to find more!

Report home > Health & Fitness

Potential Toxicity of Some Traditional Leafy Vegetables Consumed in Nyang'oma Division, Western Kenya

4.00 (1 votes)
Document Description
Traditional leafy vegetables have higher nutritional value compared to the introduced vegetable varieties, are important for food security, and they are vital for income generation. Furthermore the vegetables are important for their medicinal, ecological, agronomic and cultural values. Despite this, several studies have established that some vegetable species are potentially toxic to humans and animals since they contain a wide range of phytochemicals that are toxic. Hence there is need for extensive phytochemical studies of the vegetables commonly consumed in order to educate the communities on the possible side effects for those vegetables that may contain toxins. Qualitative phytochemical screening from traditional leafy vegetables commonly consumed amongst the Luo, an agro-pastoral community living along the shores of Lake Victoria, Western Kenya revealed that all the vegetables contain polyphenols, while other classes of phytochemicals varied from species to species. Sesamum calycimum Welw. var. angustifolium (Oliv.) Ihlenf. and Siedenst (Pedaliaceae; LC50 84.8 ?g/ml), exhibited marked levels of toxicity. C. ochroleuca (Sunnhemp) contained all classes of phytochemicals, but proved less toxic (LC50 4511.3 ?g/ml), though A. hybridus (African spinach, or Amaranth) was found to be the least toxic (LC50 6233.6 ?g/ml). The methanol: chloroform (1:1) crude extract of the leaves of S. calycimum var. angustifolium was subjected to chromatographic separation, to obtain 3,4', 5,7- tetrahydroxyflavone (Kaempferol) and ß-(3', 4-dihydroxyphenyl-O-?-L-rhamnopyranosyl (1- 3)-ß-D- (4-O-caffeoyl) glucopyranoside (Verbascoside).
File Details
  • Added: September, 13th 2009
  • Reads: 1576
  • Downloads: 57
  • File size: 214.30kb
  • Pages: 10
  • Tags: traditional vegetables, toxicity, verbascocide, kaempferol
  • content preview
Submitter
  • Username: shinta
  • Name: shinta
  • Documents: 4332
Embed Code:

Add New Comment




Related Documents

EFFECTS OF PROCESSING TREATMENTS ON THE NUTRITIVE COMPOSITION AND CONSUMER ACCEPTANCE OF SOME NIGERIAN EDIBLE LEAFY VEGETABLES

by: shinta, 18 pages

Leafy vegetables are highly perishable food items and require special processing treatments to prevent post harvest losses. Leafy vegetables to be preserved by canning, freezing or ...

Effect of Some Post-Harvest Treatments on the Nutritional Properties of Cnidoscolus acontifolus Leaf

by: shinta, 5 pages

Cnidoscolus acontifolus (Americana leaf) leaves are used as soup condiment in Nigeria either in the processed or unprocessed forms. This study aims at assessing the effect of some ...

The Effect of Charter Schools on Traditional Public School Students in Texas : Are Children Who Stay Behind Left Behind ?

by: shinta, 37 pages

Texas has been an important player in the emergence of the charter school industry. We test for a competitive effect of charters by looking for changes in student achievement in traditional ...

Learning, Types of Learning, Traditional Learning Styles and the Impact of E-Learning on the Performance of Secondary School Students : The Perception of Teachers

by: shinta, 16 pages

This paper deals with the concept of learning from the traditional modes of learning through the learning styles to e-learning among adolescent students reading at secondary school level. ...

The effects of different methods of cooking on proximate, mineral and heavy metal composition of fish and shrimps consumed in the Arabian Gulf

by: shinta, 7 pages

This study analyzed eight cooked species of fish and one species of shrimps (grilled, curried, fried and cooked in rice) commonly consumed in Bahrain for their proximate, mineral and

Comparative Study of Proteolytic Activities of Some Commercial Milk Clotting Enzymes on Bovine Skim Milk

by: shinta, 8 pages

Proteolytic activities of some commercial milk clotting enzymes(rennet, trypsin, pepsin, papain W-40, neutrase 1.5 and protease S) in bovine skim milk containing 0.02% CaCh were determined ...

Effects of various traditional processing methods on the all-trans-b-carotene content of orange-fleshed sweet potato

by: shinta, 10 pages

The effects of traditional preparation methods and drying procedures on the provitamin A carotenoid content of orange-fleshed sweet potato (OFSP) roots was determined by a high-performance ...

Effects of some processing methods on the toxic components of African breadfruit (Treculia africana)

by: shinta, 5 pages

A variety of breadfruit (Var africana) was evaluated for the presence of some anti-nutrients. It was found to contain some hydrogen cyanide (26.45 mg/kg), tannin (184.10 mg/g), starchyose (1 ...

Potential Role of Ginseng in the Treatment of Colorectal Cancer

by: mersada, 10 pages

Colorectal cancer remains one of the most prevalent cancer and a leading cause of cancer related death in the US. Many currently used chemotherapeutic agents are derived from botanicals. Identifying ...

The 6 Potential Laws of Strength Training

by: Jake, 1 pages

Here you have The 6 Potential Laws of Strength Training, which every powerlifting, bodybuilder, and strength trainer should consider.

Content Preview

11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

Potential Toxicity of Some Traditional Leafy Vegetables Consumed in
Nyang’oma Division, Western Kenya

Orech, F. O. 2, T. Akenga1*, J. Ochora2, H. Friis3, J. Aagaard-Hansen4

1 Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000, Nairobi,
Kenya.
2Department of Botany, Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000, Nairobi, Kenya.
3Department of Human Nutrition, Rolighedsveg.30, 1958 Frederiksberg, Denmark.
4Danish Bilharziasis Laboratory, Jaegersborg Allé 1D, DK-2920 Charlottenlund, Denmark.
*author for correspondence [e-mail: tezakenga@yahoo.co.uk]

Abstract
Traditional leafy vegetables have higher nutritional value compared to the introduced
vegetable varieties, are important for food security, and they are vital for income generation.
Furthermore the vegetables are important for their medicinal, ecological, agronomic and
cultural values. Despite this, several studies have established that some vegetable species are
potentially toxic to humans and animals since they contain a wide range of phytochemicals
that are toxic. Hence there is need for extensive phytochemical studies of the vegetables
commonly consumed in order to educate the communities on the possible side effects for
those vegetables that may contain toxins.

Qualitative phytochemical screening from traditional leafy vegetables commonly consumed
amongst the Luo, an agro-pastoral community living along the shores of Lake Victoria,
Western Kenya revealed that all the vegetables contain polyphenols, while other classes of
phytochemicals varied from species to species. Sesamum calycimum Welw. var.
angustifolium
(Oliv.) Ihlenf. and Siedenst (Pedaliaceae; LC50 84.8 µg/ml), exhibited marked
levels of toxicity. C. ochroleuca (Sunnhemp) contained all classes of phytochemicals, but
proved less toxic (LC50 4511.3 µg/ml), though A. hybridus (African spinach, or Amaranth)
was found to be the least toxic (LC50 6233.6 µg/ml).

The methanol: chloroform (1:1) crude extract of the leaves of S. calycimum var.
angustifolium
was subjected to chromatographic separation, to obtain 3,4', 5,7-
tetrahydroxyflavone (Kaempferol) and ?-(3', 4-dihydroxyphenyl-O-?-L-rhamnopyranosyl (1-
3)-?-D- (4-O-caffeoyl) glucopyranoside (Verbascoside).

Key words
: Traditional vegetables, toxicity, verbascocide, kaempferol

1. INTRODUCTION
Traditional vegetables from the wild or home gardens are mutually important for humans
both in rural and urban set ups in Kenya [1,2,3]. Traditional leafy vegetables (TLVs) are
those plants whose leaves or aerial parts have been integrated in a community’s culture for
use as food over a large span of time [4]. Since TLVs are highly recommended because
they have a relatively high nutritional value compared to the introduced varieties, their
consumption gives diversity to daily food intake, adding flavour and zest to the diet [5].
These vegetables are rich in vitamins, minerals, trace elements, dietary fibre and proteins
[6,7,8,9]. Effectively, the vegetables are important in food security, during times of drought
or poor harvest and are also vital for income generation. Withstanding their value as food,
the vegetables also serve as a source of medicines, and are important in their ecological,
agronomic and cultural values [10,11, 12].
Akenga et al

78


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

Despite their advantages, several studies have established that some vegetable species are
potentially toxic to humans and animals. Plant chemical compounds, toxic to humans and
livestock, are produced as part of the plant’s defence against being eaten by pests and
herbivores or to gain an advantage over competing plants [13]. Plant poisons are highly
active substances that may cause acute effects when ingested in high concentrations and
chronic effects when accumulated [14,15]. Under stress conditions, brought on by food
shortage, consumption of large amounts of vegetable toxins by animals can have negative
consequences [16]. In many cases of poisoning resulting from consumption of endogenous
toxicants such as those in toxic vegetables, death or prolonged and serious disabilities are
reported. Most traditional vegetables are relatively unpalatable and their digestibility may
be limited hence toxic. Usually unpalatibility comes from allelochemicals in plants and
these chemicals may be toxic. In addition, traditional medicines prepared from medicinal
plants and sometimes from food plants are not always safe.

Poisoning or toxic principles as relates to vegetables generally fall into various
phytochemical groups, which include alkaloids, glycosides, oxalates, phytotoxins
(toxalbumins), resins, essential oils, amino acids, furanocoumarins, polyacetylenes, protein,
peptides, coumarins, flavonoids and glycosides [15,17,18,19, 20,21]. Others are minerals
and photosensitizing compounds. For instance, Lycopersicon esculentum leaves and stems
contain the toxic solanidan alkaloids; µ-solanine and demissine, and their aglycones [22].
The toxic pyrrolizidine alkaloids are a large group of related compounds that occur in
plants, mainly in species of Crotalaria, Senecio, Heliotropium, Trichodesma, Symphytum
and Echium and are poisonous.

Toxicity is a relative concept that must be considered in relation to the context in which these
plants are used either as food or medicine. Since about 60 TLVs are commonly consumed in
Nyangoma division and Kenya at large, a phytochemical screening of the vegetables for
alkaloids, saponins, cardenolides, flavonoids and polyphenols need to be carried out and
especially to determine the toxicity tests. The toxicity results should be used to create
awareness as to which vegetables are safe for consumption as food and medicines. In the
present study, a qualitative phytochemical screening was conducted on nine vegetables
mostly consumed and sold in the local market during drought by the Luo of Nyango’ma
division. The vegetables together with their common names are: Amaranthus hybridus L.
(subsp.hybridus; Amaranth, or African spinach), Asystasia mysorensis T. Anderson, Coccinia
grandis
(L) Voigt, Crotalaria ochroleuca (Kotschy) Polhill, (Sunnhemp) Cucurbita maxima
Duchesne ex Lam, (Pumpkin) Portulaca quadrifida L. (Purselane), Sesamum calycimum
Welw. var. angustifolium (Oliv.) Ihlenf. (Onyulo) and Siedenst., Senna occidentalis L.
(Cassia) and Sida acuta Burm.(Sida). The screening was followed by brine shrimps toxicity
bioassay and isolation, purification and characterization of compounds, from the traditional
leafy vegetable that exhibited highest toxicity against brine shrimps.


2. RESULTS AND DISCUSSION
The traditional leafy vegetables collected in Nyang’oma area exhibited diverse habitats and
most species were collected mainly from the wild.

2.1 Results of Qualitative screening
The screening of nine traditional leafy vegetables that serve as buffer during periods of relish
shortage was conducted using standard screening methods of Chhabra et al., 1984, and
Harborne, 1973 [23,24]. The vegetables screened were: A. hybridus, A. mysorensis , C.
Akenga et al

79


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

grandis, C. ochroleuca, C. maxima, P. quadrifida, S. occidentalis, S. calycimun
var.angustifolium, and S. acuta. These vegetables belong to eight different families that
occur in diverse ecological locations and soil types. However, these vegetables are wide
spread in the UIC soil type, which is stony, sandy, shallow and dry. Table 1 gives a summary
of the results of phytochemical screening.

Table 1: Results of phytochemical screening
TLV Alkaloids
Saponins
Cardenolides Flavonoids Polyphenols
A. hybridus
+ + +
+ +
A. mysorensis
+ - -
+ +
C. grandis
- + +
+ +
C. ochroleuca
+ + +
+ +
C. maxima
- + +
+ +
P. quadrifida
+ + +
+ +
S. occidentalis
+ + +
+ +
S. calycimun - + +
+ +
var.angustifoliu
m

S. acuta
+ + +
+ +
+present; -absent

From Table 1, the nine vegetables contain different phytochemicals. These observations
reveal that TLVs constitute a rich, but still largely untapped pool of natural products. All
TLVs tested positive for polyphenols. C. ochroleuca tested positive for all classes of
phytochemicals. The vegetables: A. hybridus, A. mysorensis, C. ochroleuca, P. quadrifida,
S. occidentalis
and S. acuta gave a positive results for alkaloids while A. mysorensis tested
negative for saponins and cardenoloids. However, C. grandis, C. ochroleuca, C. maxima, P.
quadrifida, S. occidentalis, S. calycimum
var. angustifolium and S. acuta gave positive
results for saponins and cardenolides.

2.2 Results of Brine shrimp toxicity bioassay
Five vegetables exhibited toxicity levels of between 20 µg/ml and 1000 µg/ml, and were
classified as the most toxic. These were A. mysorensis, C. grandis, S. occidentalis, S.
angustifolium
and S. acuta. Table 2 is a summary of LC50 values and associated statistics
for brine shrimp toxicity tests on these five TLVs’ extracts showing higher toxicity at 95%
confidence intervals.

Table 2:
Summary of LC50 values and associated statistics for brine shrimps toxicity tests
on five TLVs extracts showing higher toxicity
Vegetable LC50
Slope Lower Upper
Intercep
?2/df
(µg/ml)
limit
limit
t
A. mysorensis
207.7 4.3 171.1 266.7 -9.94 144.1/1
C. grandis
100.6 277.9
-
-
556.55 0.0/1
S. occidentalis
99.5 287.5
- - -574.4
0.0/1
S. calycimum 84.8 30.9
82.5 87.3 -59.7 69.78/1
var.
angustifolium
S. acuta

99.4 285.0
- - -569.3
0.0/1
- no fiducial limit
Akenga et al

80


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

S. calycimum var. angustifolium is the most toxic vegetable, with LC50 value of 84.4 µg/ml,
yet this vegetable is commonly consumed in many households and is also readily sold in the
local markets. The other four species of vegetables showed activity between 1500 µg/ml
and 12,500 µg/ml and were classified as the least toxic vegetables. Table 3 gives a
summary of LC50 values and the associated statistics for brine shrimp toxicity tests of the
four TLVs’ extracts showing lower toxicity at 95% confidence intervals.

Table 3
: Summary of LC50 values and the associated statistics for brine shrimp toxicity tests
on four TLVs extracts showing lower toxicity
Vegetable LC50

Slope Lower Upper
Intercept
?2/df
(µg/ml)
limit
limit
A. hybridus
6233.6 50.6
6154.1
6313.1
-191.99
146.9
/1
C.ochroleuc
4511.3 39.33
44.34.3
4588.8
-143.8
128.4
a
/1
C. maxima
4311.0 20.3
4195.0
4432.0
-73.7 156.5
/1
P.
3103.0 6.2
2848.0
3480.0
-21.9 59.7/
quadrifida
1

A. hybridus
is the least toxic vegetable (LC50 6233.6 µg/ml), this species of vegetable grows
mainly in the UIC and Ulrl soil types around Nyango’ma. There is little variation between the
LC50 of S. occidentalis, S. acuta and C. grandis, probably because the extracts from these
species tested positive for almost the same phytochemicals. S. calycimum var. angustifolium
tested positive, only, for saponins, cardenolides, flavonoids and polyphenols, Table 1. Its
high toxicity could be due to the quantities and nature of the compounds present in the extract
of the vegetable. The variation in phytochemical composition in plants may be influenced by
plant factors (species and stage of growth) or environmental factors (season, weather and
soil). There is a major variation in the LC50 of A. mysorensis compared to the other
vegetables. This may be explained by the fact that A. mysorensis only screened positive for
alkaloids, polyphenols and flavonoids. However, the variation on the slope for the five
vegetables may be due to their phytochemicals’ composition rather than variations in brine
shrimp responses to the different treatments, since the shrimps had the same conditions in
terms of age and nutrient consumption. The slope of A. mysorensis is typically low while for
the other four (S. acuta, S. occidentalis, C. grandis and S. calycimum var. angustifolium), are
generally higher. The values of the ?2, which test for the homogeneity or linearity, of brine
shrimp response to the various treatment of the vegetable extracts, are not significantly
different for S. occidentalis, S. acuta and C. grandis but are significantly different for A.
mysorensis
and S. calycimum var. angustifolium.

From the results, five vegetables contain possible agents that can cause acute or chronic
toxicities when consumed in large quantities or over a long period of time.

Therefore, preparation of these vegetables for consumption should be done with caution.
Luo women know that vegetable species, such as C. grandis, and S. occidentalis, have
contra-indications and are therefore prepared using traditional cooking methods to make
consumption of the vegetables safe. From Table 1, C. ochroleuca and A. hybridus tested
positive for all the classes of compounds, but when subjected to the brine shrimp lethality
bioassay (Table 3), proved less toxic. This implied that the type of compounds present in
Akenga et al

81


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

these vegetables, by nature, have no toxic effects to the brine shrimps. C. ochroleuca is
highly utilized in Nyang’oma, and seventy per cent of the respondents consume this species.
The vegetable has a mild taste and is morphologically broad-leafed.

2.3 Structure elucidation of compounds extracted from S. calycimum
var. angustifolium
Two compounds were isolated, using chromatographic techniques, from the traditional leafy
vegetable that exhibited highest toxicity against the brine shrimps. The structures of the
compounds were determined by spectroscopic analysis and comparison with literature data.

2.3.1
?-(3', 4'-dihyroxyphenyl-O-?-L-rhamnopyranosyl (1-3)-?-D- (4-O-caffeoyl)
glucopyranoside (Verbascoside, 1)

The 'H nmr spectral data for 1 is summarised in Table 4
9
H
O
H
HO
2'''
4
OH
7
8
O
5
H
H
3
O
O
2
2'
H
O
OH
6'
O
1
HO
CH3
5'''
4'
OH
3'
H
HO
6
HO
H
H
H
H
OH
OH
5''
H
1

Table 4: 1Hnmr data of 1 in CD3OD.








Glucosyl
Rhamnosyl
Phenylethlyl
E-Caffeoyl
Position (?)ppm
Position (?)ppm Position
(?)ppm Position
(?)ppm
1
4.45 (d, 1'
5.30 (br.s) 2"
6.78 (d, 2'''
7.20 (d, 2.1)
7.7)
1.9)
2
3.55 (m)
2'
3.68 m)
5"
6,79 (d, 5'''
6.88 (d, 8.1)
7.9
3
3.90 (m)
3'
3.98
6"
6.58 (dd, 6'''
7.04 (dd, 1.9,
2.1, 8.1)
8.3)
4
4.98 (t, 9.4) 4'
3.40
? 1
3.70 (dt)
?
6.32 (d, 16.0
5
4.00 (m)
5'
3.65
? 2
4.02 (dt)
?
7.61 (d, 15.8)
6
3.5, 3.60
6'
1.12 (d, ?
2.77 (t,

6.0)
7.5)

The 'H nmr spectrum of 1 exhibited characteristic signals belonging to an E-caffeoyl unit, showing
three aromatic protons as an ABX system [?6.88, (d, J=8.1Hz. H-5'''), ?7.04 (dd, J=1.9.8.3 Hz, H-
6''')]. There were two trans olefinic protons at 6.32 (d, J=16.0Hz, H-?) and 7.61 (d, 15.8 Hz, H-?).
Signals belonging to the 3,4 dihydroxyphenylethanol moiety (the aglycone) included a set of
aromatic protons displaying an ABX system [6.58 (dd, J= 2.1,8.1Hz, H-6), 6.74 (d, J=7.9Hz, H-5)
and 6.78 (d, J=1.9Hz, H-2)] and two multiplets of coupled methylenes (? and ?). The chiral centre
at C-1 is responsible for the observed non-equivalency of the ?-methylene protons of the aglycone,
which was found resonating at ?3.70 (d, t) and ?4.02 (d, t). The benzylic or ?-methylene protons
resonated at ?2.77 (t J=7.5Hz). The ?-glucopyranosyl unit showed the anomeric proton at ?4.45 (t,
Akenga et al

82


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

J=7.7Hz). The configuration of the anomeric centres of both glucosyl and rhamnopyranosyl
moieties were confirmed by coupling constant and chemical shifts. Linkage of the rhamnosyl unit
to the central glucosyl unit is defined by the downfield value observed for H-3 (?3.90). The E-
caffeoyl unit was located at C-4 of glucose as concluded from the more downfield shift of H-4 at ?
4.98 as a triplet (9.42 Hz). The 13C nmr of 1 is summarized in Table 5.

Table 5: Summary of 13C nmr data for 1 in CD3OD.







Glucosyl
Rhamnosyl
Phenylethyl
t-Caffeoyl

Position (?)ppm
Position
(?)ppm
Position (?)ppm
Position (?)ppm
1.
103.2
1'
101.6
?
71.1
C=O
166.9
2.
75.9
2'
71.7
?
35.7
?
144.52
3.
79.8
3'
71.5
1'
130.7
?
146.6
4.
69.2
4'
73.1
2'
116.5
1'
127.0
5.
75.3
5'
69.2
3'
143.8
2'
144.8
6.
61.8
6'
17.8
4'
145.2
3'
145.8




5'
116.0
4'
148.6




6'
120.2
5'
116.0

The 13C-nmr data showed a total of 29 carbons, which included 23 oxygenated and six sp2
quaternary carbons. The hydrogen bearing aromatic carbon signals were observed at ?116.5, 116.0,
120.2 and showed HMQC correlative with H-2'', H-5'' and H-6'' respectively on the aromatic ring of
the aglycone. The oxygenated aromatic signal at ?143.8 and 145.2 were on the basis of key HMBC
correlation assigned at C-3'' and C-4'', respectively. The methylene carbons were revealed by
DEPT. These resonated at ? 35.7 for ?-C and, more downfield, at ? 71.1 for the oxygenated ?-
carbon of the aglycone, and 61.9 for C-6 glucose. A similar procedure led to the assignment of
signals at ?114.8 (C-2'''), 116.0 (C-5'''), 122.5 (C-6'''), 45.8 (C-3''') and ? 148.6 (C-4''') and the
subsequent correlation of these signals to the caffeoyl unit. The other carbons linked to the E-
caffeoyl unit include the ?, ?-unsaturated carbonyl resonating at ? 166.9 and the two olefinic
carbons at ?114.5 (?-C) and ? 146.6 (?-C). The anomeric carbon and methyl carbon of the
rhamnosyl unit were found to resonate at ?101.6 (C-1') and ?17.8 (C-6'). The anomeric carbon of
glucose moiety was at ?103.2 (C-1') while C-3' the point of linkage for the rhamnosyl unit was
slightly deshielded at ?79.8.

Verbascoside, 1, has been isolated from over 60 plant species pertaining to 14 families [25]. The
family Pedaliaceae does not contain cyanogens, saponins and proanthocyanidins but iridoids have
been detected and, 1, has been isolated from three of the 13 genera in Pedaliacaeae namely,
Harpagophytum, Rogeria and Sesamum [25]. However, this is the first time, 1 has been isolated
from the species S. calycimum var. angustifolium. Verbascoside has hepatoprotective, sedative,
cytotoxic, immunosuppresive and analgesic properties [26], and exhibits antihepatotoxic,
hypertensive, and antiinflammatory activities [22].
Similarly, 3,4', 5,7-tetrahydroxyflavone (Kaempferol, 2) was isolated and characterized.
OH
O
OH
OH
O
2
Akenga et al

83


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

Kaempferol is reported to be a potent antioxidant [27] with direct cytotoxicity [28] and has also
been isolated from the leaves of other plant species such as pumpkin, lettuce, tobacco, faba bean,
cacao, peach, pepper and onions [29]. However, this is the first time that the flavone, 2, has been
isolated from S. calycimum var. angustifolium.

3.

EXPERIMENTAL
3.1.
Plant materials
Plant samples of TLVs were sampled in the field and collected from different habitats of
Nyang’oma division, Western Kenya, between 29? and 35?E (Latitude and Longitude) of
prime meridian. Information about the use of the vegetables and cooking methods were
obtained by interviewing knowledgeable persons on the traditional vegetable species. The
respondents were asked questions about the vernacular names, ecology, distribution,
management, season, status and use of the TLVs. Finally, identification of the TLVs
followed the taxonomy of Flora of Tropical East Africa (FTEA) [30]. Voucher specimens
were deposited at the JKUAT Botany Herbarium
The leaves and shoots of the TLVs were macerated using scissors, and dried under shade.
The dried samples were separately ground into fine powder using a motor laboratory grinding
mill (Christy and Norris Ltd. Chemsford-England).

3.2. General

experimental
procedure
The 1H nmr spectra was recorded on Bruker AMX-400 spectrometers using the UNIX data
systems at 400 MHz while the Carbon 13 Nuclear Magnetic Resonance (13C-NMR), Proton
Correlation Spectroscopy (1H-COSY), 1H-13C Proton Homonuclear Quantum Correlation
(HMQC) and Heteronuclear Multiple Bond Correlation (HMBC) spectra were recorded on
Bruker AMX-400 at 400 MHz respectively and the coupling constant (J) measured in Hz.
The spectra were recorded in deuteriated methanol (CD3OD) solvent system and the chemical
shifts (?) reported in parts per million (µg/ml). The multiplicities were recorded as d doublets,
dd double of doublets, s singlet, brs broad singlet, t triplet, and q quartet. The MS was
performed on Finnigan MAT SSQ 7000 Single stage quadrupole analyzer at 70 ev in CD3OD
and the Ultra Violet spectroscopy performed on UV Shimadzu UV-210PC Spectrometer. The
Infrared spectroscopy was performed on IR Perkin-Elmer 2000-FT-IR Spectrometer.

3.3.

Extraction and isolation
Ground leaf powder (200.0 g) of each vegetable was soaked in a mixture of methanol and
chloroform (1:1, 24 hrs) and subsequently in methanol (100%, 24 hrs). The crude extracts
were concentrated in vacuo and each concentrated extract was separately soaked in
activated charcoal (15 minutes), in order to remove chlorophyll, stirred thoroughly and
sieved using filter paper (595 Rundfilter, 270 mm). The filtrates were further concentrated
in vacuo and stored in labelled sample bottles. Each extract (2.0 g) was used in the
screening tests.

Ground leaf material (1000 g) of S. calycimum var. angustifolium was soaked in MeOH:
CHCl3 (1:1, for 24 h) and subsequently in MeOH (100%, 5 L) for another 24 hours
respectively then filtered using filter paper (595 Rundfilter, ? 270 mm) and concentrated in
vacuo
(40? C). Analytical silica gel G (Merck, 0.25 cm) pre-coated plates were used for
Thin-Layer chromatography (TLC) and the spots on TLC plates visualised under ultra violet
(UV) light (?=366 nm and ?=254 nm) and by spraying with vanillin spray. Column
chromatography (CC) was carried out using Sephadex-L20 and silica gel 60 HF254+366 while
preparative chromatography (PC) was carried out using silica gel (Merck, 60 (0.040:0.063
mm). All the solvents used for chromatography were of analytical grade.
Akenga et al

84


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

3.4.
Screening for phytochemicals
Screening was done according to Chhabra, 1984 and Harbone, 1973, [23, 24].

3.4.1 Alkaloids
Each extract was boiled (15 minutes) in HCl (25.0 ml, 1%). Equal volumes of the resulting
suspension were filtered into two test tubes (A and B). To A, 5 drops of freshly prepared
Dragendorrf’s reagent were added. Formation of a precipitate indicated the presence of
alkaloids. To confirm the results, B was treated with saturated sodium carbonate solution
until a drop of the solution turned the Universal Indicator paper blue, (pH 8-9). The
resulting solution was dissolved in CHCl3 (4 ml) and allowed to stand. The aqueous layer
was collected and acetic acid added to it dropwise, until the solution turned Universal
Indicator paper yellow-brown (pH 5).

3.4.2 Cardenolides
The vegetable extracts were thoroughly mixed with distilled water (20.0 ml) and kept at
room temperature (2 hrs). The suspension was filtered into two separate test tubes (A and
B). To A, 4 drops of Kedde’s reagent was added. The appearance of a blue violet colour
indicated the presence of cardenolides. Test tube B was used to monitor and compare colour
change.

3.4.3 Saponins
Each vegetable extract was added to water (15.0 ml) and warmed on a water bath (15
minutes). The resulting solution was filtered and left to cool to room temperature and was
transferred (10.0 ml) in a test tube. This was shaken thoroughly for ten seconds and the
height of the persistent (5-10 minutes) honeycomb froth measured. Honeycomb froth
higher than 1 cm confirmed the presence of saponins.

3.4.4 Polyphenols
Ethanol (10.0 ml) was added to each extracts and the resulting solution (3.0 ml) was
transferred in test tubes and warmed in a water bath (15 minutes). Three drops of freshly
prepared ferric cyanide solution were added to the extract solution. Formation of a blue
green colour indicated the presence of polyphenols.

3.4.5 Flavonoids
The vegetable extracts were added to water (10.0 ml) and methanol (5.0 ml). A few
magnesium turnings were added to this mixture (3.0 ml) and followed by drop wise addition
of conc. HCl (cyaniding). Development of either, orange, red and pink colours indicated
presence of flavonoids.

3.5 Brine shrimp toxicity bioassay
The brine shrimp (Artemia salina) toxicity bioassay test was conducted according to
McLaughlin et al, 1991 [32]. The obtained data was subjected to Probit Analysis, using
Statistical Analysis Systems (SAS) computer program, and the lethal concentration values
that killed fifty percent of the shrimps (LC50) were determined for each vegetable.

Acknowledgements
The authors are grateful to Prof. R. Majindar for offering us an opportunity to carry out
phytochemical screening experiments in his Natural products laboratory, at the University of
Botswana. Mr. Charles Wafula, Mr. Tom Odera (Chemistry Department, JKUAT), Mr.
Akenga et al

85


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

Josphat Muthanga (Botany Department, JKUAT) for their technical assistance. This work
was supported by funds from the Danish Bilharziasis Laboratory (DBL).

References
1. FAO. United Nations Food and Agricultural Organization: The State of the world's Plant
Genetic Resources for Food and Agriculture. FAO, Rome, 1998.
2.
FAO. United Nations Food and Agricultural Organization: Report on the state of the world's
plant genetic resources for food and agriculture prepared for the International Technical
Conference on Plant Genetic Resources, Leipzig, Germany, Food and Agricultural
Organization (FAO), Rome, 1996.
3.
FAO. United Nations Food and Agricultural Organization: Traditional food plants. Food
and Agricultural Organization (FAO) Food Nutrition.
Paper 42. FAO, Rome, 1988: 593.
4.
Ogoye-Ndegwa, C.; Aagaard-Hansen, J. Traditional gathering of wild vegetables among the
Luo of western Kenya-a nutritional anthropology project. J. Ecol. Food and Nutri., 2003;
69-89.
5.
Asfaw, Z. Conservation and Use of Traditional Vegetables in Ethiopia. In: L Guarino (Ed).
Traditional African Vegetables: Proceedings of the IPGRI International Workshop on
Genetic Resources of Traditional Vegetables in Africa. Conservation and Use. ICRAF-HQ,
Nairobi. Institute of Plant Genetic and Crop Plant Research, Rome, 1997: 57-65.
6.
Humphrey, C. M, Clegg, M. S.; Keen, C. L.; Grivetti, L. E. Food diversity and drought
survival: The Hausa example. Int. J. Food Sc. and Nutrit., 1993; 44: 1-16.
7. Mathenge,
L. Nutrition value and utilization of indigenous vegetables in Kenya. In:
Guarino L (Ed). Traditional African Vegetables: Proceedings of the IPGRI International
workshop on Genetic Resources of Traditional Vegetables in Africa. Conservation and Use.
ICRAF-HQ, Nairobi. Institute of Plant Genetic and Crop Plant Research, Rome, 1997: 76-
77.
8.
Maundu, P. M. The status of traditional vegetable utilisation in Kenya. In: Guarino L (Ed).
Traditional African Vegetables. Proceedings of the IPGRI International workshop on
Genetic Resources of Traditional Vegetables in Africa. Conservation and Use. ICRAF-HQ,
Nairobi. Institute of Plant Genetic and Crop Plant Research, Rome, 1997: 66-71.
9.
Nordeide, M. B.; Hatløy, A.; Følling, M.; Lied, E; Oshaug; A. Nutrient composition and
nutritional importance of green leaves and wild foods in an agricultural district, Koutiala, in
Southern Mali. Int. J. Food Sc. and Nutrit.. 1996; 47: 455-468.
10.
Geissler, P. W.; Harris, S. A.; Prince, R. J.; Olsen, A.; Odhiambo, R. A.; Oketch-Rabah, H.;
Madiega, P. A.; Anderson, A. Mølgaard, P. Medicinal plants used by Luo mothers and
children in Bondo District, Kenya. J. Ethnopharma. 2002; 83: 39-54.
11. Abbiw,
D.
K. Diversity and traditional uses of African vegetables. In: Guarino L (Ed).
Traditional African Vegetables: Proceedings of the IPGRI International Workshop on
Genetic Resources of Traditional Vegetables in Africa. Conservation and Use. ICRAF-HQ,
Nairobi. Rome: Institute of Plant Genetic and Crop Plant Research, 1997: 29-30.
12.
Okafor, J. C. Conservation and use of traditional vegetables from woody forest species in
southeastern Nigeria. In: Guarino L (Ed). Traditional African Vegetables: Proceedings of
the IPGRI International Workshop on Genetic Resources of Traditional Vegetables in
Africa. Conservation and Use. ICRAF-HQ, Nairobi. Institute of Plant Genetic and Crop
Plant Research, Rome, 1997: 31-38.
13. Dowling, R. M.; McKenzie, R. A. Poisonous Plants: A Field Guide. Queensland
Department of Primary Industries, Brisbane. 1993.
14. Kofi-Tsekpo,
W.
M. Pharmaceutical Applications of Ethnobotany: Conservation and
utilization of indigenous medicinal plants and wild relatives of food crops. United Nations
Educational, Scientific and Cultural Organisation (UNESCO), Nairobi, 1997: 57-63.
Akenga et al

86


11th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar
Pages 78-87

15.
Pfänder, F. A Colour Atlas of Poisonous Plants: A handbook for Pharmacists, Doctors,
Toxicologists and Biologists. Wolfe Publishing Limited, London. 1984: 10-222.
16.
Johns, T.; Kokwaro, J. O. Food Plants of the Luo of Siaya District, Kenya. Economic
Botany
. 1991; 45: 103-113.
17. Concon,
J.
M. Food Toxicology, Part A: Principles and Concepts. Marcel Dekker, New
York, 1988; 8.
18.
Ezekwe, M. O.; Thomas, R. A.; Membrahtu, T. Nutritive characterization of purslane
accessions as influenced by planting date. Plant Foods for Human Nutrition 1999; 54: 183-
191.
19.
Palaniswamy, U. R.; McAvoy, R.; Bible, B. Omega-3-fatty acid concentration in Portulaca
oleraceae
L. is altered by the source of nitrogen in hydroponics solution. J. Hort. sci. 1997;
32: 462-463.
20.
Uiso, F. C.; Johns, T. Risk assessment of the consumption of a pyrrolizidine alkaloid
containing indigenous vegetable Crotalaria brevidens (Mitoo). J. Ecol. Food and Nutr.
1995; 35: 111-119.
21.
United States Food and Drug Administration Pyrrolizidine Alkaloids: Food-borne
Pathogenic Microorganisms and Natural Toxins Handbook. Centre for Food Safety and
Applied Nutrition, 1992.
23.
Chhabra, S. C.; Uiso, F.C.; Mshiu, E. N. Phytochemical screening of Tanzanian Medicinal
Plants. Journal of Ethnopharmacology, 1984, 11: 157-179.
24. Harborne, J. B. Phytochemical Methods: A Guide to Modern Technique of Plant Analysis.
Chapman and Hall, London, 1973.
25. Watson, L.; Dallwitz, M. J. The Families of Flowering Plants: Description, Identification,
and Information Retrieval. Version: 14th December 2000. http://biodiversity.uno.edu/delta/
26.
Calis, I.; Kirmizibekmez, H.; Rüegger, H.; Sticher, O. Phenylethanoid
Glycosides from Globularia trichosantha. Journal of Natural Products. American
Chemical Society and American Society of Pharmacognosy, 1999, 62: 1165-1168.
27.
Yang, B.; Arai, K.; Kusu, F. Electrochemical Behaviors of Quercetin and Kaempferol in
Neutral Buffer Solution. Analytical Sciences. The Japan Society for Analytical Chemistry,
2001, 17: 987-989.
28.
Habtemariam, S. Flavonoids as Inhibitors or Enhancers of the Toxicity of Tumour
Necrosis Factor-? in L-929 Tumour cells. Journal of Natural Products. American
Chemical Society and American Society of Pharmacognosy, 1997, 60: 775-778.
29.
Duke, A. J. Phytochemical and Ethnobotanical Databases: Plant parts with Cytotoxic
Activity from the chemical Kaempferol. United States Agricultural Research Service,
1996, 1-3.
30.
Agnew, A. D. Q.; Agnew, A. Upland Kenya Wild Flowers. East Africa Natural History
Society, Nairobi, 1994.
31. Harborne, J. B.; Baxter, H. Phytochemical Dictionary: A Handbook of Bioactive
Compounds from Plants. Taylor and Francis Ltd, London. 1993; 127-540.
32.
McLaughlin, J. L; Chang, C. J.; Smith, D. L. "Bench-top" Bioassays for the discovery of
Natural Products: An update in Studies in Natural Products Chemistry. 9th Edition.
Attaur-rahman, 1991; 383.

Akenga et al

87

Download
Potential Toxicity of Some Traditional Leafy Vegetables Consumed in Nyang'oma Division, Western Kenya

 

 

Your download will begin in a moment.
If it doesn't, click here to try again.

Share Potential Toxicity of Some Traditional Leafy Vegetables Consumed in Nyang'oma Division, Western Kenya to:

Insert your wordpress URL:

example:

http://myblog.wordpress.com/
or
http://myblog.com/

Share Potential Toxicity of Some Traditional Leafy Vegetables Consumed in Nyang'oma Division, Western Kenya as:

From:

To:

Share Potential Toxicity of Some Traditional Leafy Vegetables Consumed in Nyang'oma Division, Western Kenya.

Enter two words as shown below. If you cannot read the words, click the refresh icon.

loading

Share Potential Toxicity of Some Traditional Leafy Vegetables Consumed in Nyang'oma Division, Western Kenya as:

Copy html code above and paste to your web page.

loading