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COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY
African nightshades (Solanum nigrum complex): The
potential contribution to human nutrition and livelihoods
in sub-Saharan Africa
Frank Sangija Haikael Martin Athanasia Matemu
Department of Food Biotechnology and
Nutritional Sciences (FBNS), Nelson
Mandela African Institution of Science
and Technology (NM-AIST), Arusha,
Tanzania
Correspondence
Frank Sangija, Department of Food
Biotechnology and Nutritional Sciences
(FBNS), Nelson Mandela African Insti-
tution of Science and Technology(NM-
AIST), PO Box , Arusha, Tanzania.
Email: sangijaf@nm-aist.ac.tz/
frank.sangija@yahoo.com
Funding information
German Federal Ministry of Foodand
Agriculture (BMEL), Grant/AwardNum-
ber: PROC; German FederalMin-
istryofFoodandAgriculture(BMEL),
Grant/AwardNumber: PROC
Abstract
Achieving zero hunger in sub-Saharan Africa (SSA) without minimizing posthar-
vest losses of agricultural products is impossible. Therefore, a holistic approach
is vital to end hunger, simultaneously improving food security, diversity, and
livelihoods. This review focuses on the African nightshades (ANS) Solanum spp.
contribution to improving food and nutrition security in SSA. Different parts
of ANS are utilized as food and medicine; however, pests and diseases hinder
ANS utilization. African nightshade is rich in micronutrients such as β-carotene,
vitamins C and E, minerals (iron, calcium, and zinc), and dietary fiber. The
leaves contain a high amount of nutrients than the berries. Proper utilization
of ANS can contribute to ending hidden hunger, mainly in children and preg-
nant women. Literature shows that ANS contains antinutritional factors such
as oxalate, phytate, nitrate, and alkaloids; however, their quantities are low to
cause potential health effects. Several improved varieties with high yields, rich
in nutrients, and low alkaloids have been developed in SSA. Various processing
and preservation techniques such as cooking, drying, and fermentation are fea-
sible techniques for value addition on ANS in SSA; moreover, most societies are
yet to adopt them effectively. Furthermore, promoting value addition and com-
mercialization of ANS is of importance and can create more jobs. Therefore, this
review provides an overview of ANS production and challenges that hinder their
utilization, possible solutions, and future research suggestions. This review con-
cludes that ANS is an essential nutritious leafy vegetable for improving nutrition
and livelihoods in SSA.
KEYWORDS
African nightshade, diversity, nutritional, postharvest losses, preservation, utilization
Abbreviations: AIV, African indigenous vegetable; ANS, African nightshade; BNS, Black nightshade; BW, body weight; CF, Controlled
fermentation; DW, Dry weight basis; EFSA, European Food Safety Authority; FAO, Food and Agriculture Organization of the United Nations; FW,
Fresh weight basis; HCN, hydrogen cyanide; KSH, Kenyan Shilling; LAB, Lactic acid bacteria; PaP, Processing and preservation; PHH, Postharvest
handling; PHL, Postharvest losses; RDA, Recommended daily allowance; SF, Spontaneous fermentation; SGA, Steroidal glycoalkaloid; SSA,
sub-Saharan Africa; TGA, Total glycoalkaloids; TM, Traditional medicine; TZS, Tanzanian shilling; UA, Urban agriculture; WHO, World Health
Organization; WVC, World Vegetable Center.
Compr Rev Food Sci Food Saf. ;–. © Institute of Food Technologists R
1wileyonlinelibrary.com/journal/crf
2 .. .
1 INTRODUCTION
African nightshades (ANSs) are among many under-
utilized and neglected African indigenous vegetables
(AIVs) species; if adequately exploited, they could improve
food, nutrition, and income among the rural population
(Abukutsa, ; Abukutsa-Onyango, ; Dinssa et al.,
). However, Weinberger and Msuya () argued that
AIVs are not underutilized as usually thought but some-
what are undervalued. ANS belongs to many species in
the genus Solanum in the family Solanaceae found in tem-
perate and tropical regions of the world, and it consists
of about genera and to species (Edmonds
&Chweya,;Yang&Ojiewo,). Within this fam-
ily, Solanum forms the largest and most complex genus
composed of more than species (Edmonds & Chweya,
).
ANS is among the known AIVs rich in nutrients to pro-
mote food and nutrition security in sub-Saharan Africa
(SSA) (Yang & Ojiewo, ). The AIVs are considered
a new cash crop in most SSA regions because they con-
tribute to income generation to individuals and house-
holds (Shackleton et al., ). AIVs have been part of
SSA’s food systems for generations, and their leaves, young
shoots, and flowers are consumed for various purposes
(Abukutsa-Onyango, ; Ambrose-Oji, ;Yang&
Ojiewo, ). ANSs are among high-priority AIVs with
the potential for health, nutrition, and economic benefits
(Edmonds & Chweya, ;Yang&Ojiewo,). They
are rich in macro- and micronutrients, including thiamine,
ascorbic acid, iron, calcium, zinc, protein, and dietary fiber
(Kirigia et al., ;Ontitaetal.,; Ronoh et al., ;
Yuan et al., ). Furthermore, they are rich in bioac-
tive compounds, particularly lutein, zeaxanthin, polyphe-
nol, flavonoids, and chlorophylls, which possess antioxi-
dant activity, anti-genotoxicants, and anticancer proper-
ties (Odongo et al., ). In SSA, ANS is exploited for
food, medicines, animal feed, and spiritual uses, but less
exploited for socioeconomic benefits (Abukutsa-Onyango,
;Ontitaetal.,). However, AIVs are wasted (Global
Panel, ; Stevens et al., ) despite the favorable
climatic conditions and high production; they account
for % of postharvest losses (PHL) of all food pro-
duced in SSA (Global Panel, ; Weinberger & Msuya,
).
This review focuses on harnessing the ANS potential
in SSA. It explores the ANS diversity, cultivation, nutri-
tional and functional benefits, antinutritional factors, and
safety. Further, it summarizes and discusses the impact
of PHL, postharvest handling (PHH) and processing, and
traditional recipes for ANS. Importantly, the ANS roles in
health promotion, trends in utilization and possible con-
straints, and possible solutions are summarized.
2 DIVERSITY OF ANS
The commonly available ANS species in SSA include
S. americanum,S. scabrum,S. nigrum,andS. villosum
(Table ) (Edmonds & Chweya, ; Keller, ;Yang
&Ojiewo,; Yuan et al., ). Eight species belong
to the S. nigrum complex or the black nightshades
(BNSs) complex, namely, S. nigrum L., S. americanum,S.
scabrum Mill., S. sarrachoides Sendtn., S. villosum Mill.,
S. grossedentatum A. Rich., S. florulentum Bitter, and S.
tarderemotum Bitter, which are distinguished based on
characteristic morphological traits (Dehmer & Hammer,
; Edmonds & Chweya, ; Ojiewo, Mwai et al.,
; Ronoh et al., ). Solanum scabrum and S. villosum
are most prevalent in East Africa (Table ) (Ambrose-Oji,
) but are produced in other regions of Africa (Table
and Figure ). Nonetheless, they are still considered a wild
weedy crop in most SSA (Dinssa et al., ; Edmonds &
Chweya, ). They can be grown in various places such as
roadsides, hedgerows, around building and houses, under
trees, as garden weeds, riverbanks and in gullies, on forest
and grassland margins, quaysides and rubbish tips, on
shingle beaches, on railway cuttings, and the edges of cul-
tivated fields and plantations (Edmonds & Chweya, ).
About % of farmers in Mbale, Uganda, collect ANSs
from the wild for selling in the urban markets (Ambrose-
Oji, ; Kasambula et al., ). Approximately %
of vegetable supplies in big cities in SSA, including the
Central Africa Republic, Guinea-Bissau, Madagascar, and
Tanzania, are predicted to come from urban and peri-
urban agriculture (UA) (Ambrose-Oji, ). Most of these
vegetables are exotic and highly consumed in urban and
peri-urban regions (Ambrose-Oji, ). However, many
fresh AIVs leaves available in urban markets come from
rural areas due to seasonal production (Gido et al., ).
Solanum nigrum, commonly known to be native to
Eurasia, was introduced in the Americas, South Africa,
and Australasia (Kuete et al., ). Whereby, S. amer-
icanum (American BNS) is native to the Americas
(Dehmer & Hammer, ) and is the most unrelated
species within the S. nigrum complex with only about
% of genetic similarity (Gilbert, ). Within the S.
nigrum complex, S. scabrum and S. nigrum are near related
species (about %), with the S. villosum being close to
them by % (Dehmer & Hammer, ; Gilbert, ).
American BNSs are native to the Americas, particularly
Cuba and South America (Dehmer & Hammer, ;
.. . 3
TABLE 1 Edible ANS species diversity and distribution in SSA
African nightshades Description Distribution References
Solanum scabrum Mil Broad leaves
Ripe berries ( to berries);
seeds weight of . to . g
Black or purple leaves of greater than
mm in size
Differ in growth habits, bitterness, and leaf
color
Taller up to . m in height
Low rainfall and temperature ( to ◦C)
Good sources of carotenoid, vitamin C, E
and A, C, calcium, iron, zinc, and protein
Used as food and medicine
East Africa, West Africa,
Central Africa
Abukutsa-Onyango,
; Edmonds and
Chweya, ;
Maundu et al., ;
Wafula, ;Yang
and Ojiewo,
Solanum nigrum Miller Black nightshades, leafy green vegetables
(S. eldorettii,S.tarderemotum,andS.
florilegium)
Berries about to ; seeds
weight of .-. g
Good sources of carotenoid, vitamin C, E
and A, C, calcium, iron, zinc, and protein
Used as food and medicine
North Africa, Kenyan
Highlands, Northern
Tanza nia
Edmonds and Chweya,
; Jacoby et al.,
; Maundu et al.,
; Shackleton et al.,
; Wafula, ;
Yang and Ojiewo,
Solanum americanum
Miller
Black nightshades; Mnavu,Msogo,and
Mhaki (Tanzania) and
Wsuggaenzirugavu (Uganda)
Berries are shiny dark purple, and the
barriers are small than mm
Small berries about ; seeds weigh
. to . g
Moderately thin branches than other
species
Good sources of carotenoid, vitamin C, E
and A, C, calcium, iron, zinc, and protein
Used as food and medicine
East Africa, West Africa,
Central Africa,
Southern Africa
Edmonds and Chweya,
; Maundu et al.,
; Shackleton et al.,
; Wafula, ;
Yang and Ojiewo,
Solanum villosum Miller Black nightshades or garden huckleberry;
Mnavu (Tanzania and Kenya)
Berries about to (orange to
yellow); seeds weight of . to . g
Wild and cultivatedUsed as food and
medicine
East Africa, West Africa,
Central Africa,
Southern Africa,
Egypt
Edmonds and Chweya,
; Maundu et al.,
; Shackleton et al.,
; Wafula, ;
Yang and Ojiewo,
Gilbert, ). In the Americas, this species is found in
California, Mexico, Central America, and South America.
The nomenclature and taxonomy are associated with
toxic BNS (Atropa belladonna) of temperate Eurasian
origin; this species has many phenotypic similarities
with many nightshades (Gilbert, ). ANS has been
consumed for centuries by native peoples in Central
America, Mexico, and Africa and is essential in these
regions (Lotter et al., ). In SSA, Bennin, Cameroon,
Burkina Fasso, Tanzania, and Kenya highly consume ANS
(Keller, ; Weinberger & Msuya, ; World Vegetable
Center [WVC], ), and it is also well promoted in the
Southern African Development Community (SADC)
region (Ojiewo, Mbwambo, et al., ). Table shows the
diversity and distribution of ANS in SSA. In Tanzania, the
northern (Arusha and Kilimanjaro), central (Dodoma),
eastern (Morogoro and Tanga), and southern (Iringa and
Mbeya) zones are well-known for ANS production (Keller,
; Weinberger & Msuya, ). Both traditional and
exotic vegetables cover % of all cultivated land (Wein-
berger & Msuya, ; Dinssa et al., ). In East Africa,
some improved cultivars of S. scabrum and S. villosum
were released based on their superior yield and acceptabil-
ity. Thirteen cultivars of S. scabrum (ACC.B, ACC.A,
ACC.B, ACC., ACC., ACC., ACC., ACC.,
ACC., ACC., and ACC.B) and S. villosum (ACC. and
ACC.) were released in Kenya (Ronoh et al., ). In
Tanzania, cultivars of S. scabrum (BG-Nduruma and
4 .. .
FIGURE 1 Leaves, flowers, and berries of S. nigrum,S.
villosum,andS. scabrum: a, e, and i, respectively. Unripe berries,
ripe berries, and flower of S. nigrum: b, c, and d, respectively. Unripe
berries, ripe berries, and flowers of S. villosum:f,g,andh,
respectively. Unripe berries, ripe berries, and flower of S. scabrum:j,
k, and l, respectively
Source: Authors.
SS-Olevolosi), and RC-ES--Ambureni (S. villosum)
and RC-ES--Malala (S. scabrum) were released
in and , respectively (https://www.tosci.go.
tz/publications/; Ojiewo, Mbwambo, et al., ;
Mbwambo et al., ). Also, about five advanced lines of
S. scabrum (SS, SS, SS, ABUK, and ABUK) and
one of S. villosum (ABUK) are available in Kenya and
Tanzania (Ronoh et al., ).
3 CULTIVATION OF ANS
ANS are a popular and cash-generating vegetable in Africa
(Yang et al., ). The production of ANS requires a small
portion of land, and it does not require extensive exter-
nal inputs and production experts. Therefore, it encour-
ages the majority of farmers to engage in its produc-
tion (Abukutsa-Onyango, ). Demands for AIVs have
surged in Africa due to rising market requirements for
AIVs varieties (Yang et al., ). Small-scale production
of ANS is common in Kenya; about % of farmers use
less than . acres on production (Abukutsa-Onyango,
; Ambrose-Oji, ), characterized by low leaf yields
of . to tons/ha specifically for S. scabrum,S. villosum,
and S. americanum (Ojiewo, Mbwambo, et al., ). A
low level of production of ANS hinders the availability and
consequently results in low consumption. Onyango et al.
() indicated that about % to % of ANS growers in
Kenya are women cultivating small plots of less than .
acres. About % of all farmers produce less than kg
of ANS per season (Abukutsa-Onyango, ;Ambrose-
Oji, ; Gebru, ). AIVs are grown mainly in home
gardens within the homestead (Abukutsa-Onyango, ),
as a source of food and small income generation for their
family; it also helps them become financially independent
(Onyango et al., ).
3.1 Cropping system of ANS
Mono-cropping, intercropping, and crop rotation are crop-
ping systems used in the growing of ANS. However, most
farmers practice mono-cropping, followed by intercrop-
ping, and few farmers practice crop rotations. There are
several benefits of intercropping that include a diversity
of crops in a given season and optimal utilization of
resources such as nutrients, water, and light (Gebru, ;
Onyango et al., ). ANS can be intercropped with maize,
millet, sweet potatoes, kale, beans, avocado, cassava,
groundnuts, and bananas (Abukutsa-Onyango, ). The
current global trend is encouraging organic farming by
avoiding using harmful chemicals to the environment and
consumers (Abukutsa-Onyango, ). The planting of
ANS is carried out twice in Kenya during the long rains
(March to July) and the short rains (September to Decem-
ber) (Abukutsa-Onyango, ). About % of Kenya’s
farmers depend on rainfall, and only % to % are prac-
ticing irrigation using watering cans (Abukutsa-Onyango,
; Gebru, ).
3.2 Yields of ANS
ANS edible leaves give the highest yield between and
tons/ha per season (Abukutsa-Onyango, ; Edmonds
&Chweya,; Ojiewo, Mbwambo, et al., ). How-
ever, Ojiewo, Mbwambo, et al. () and Molina et al.
() reported an annual yield of .–. and . tons/ha,
respectively. The average share of cultivated ANS varies
across locations, and the most substantial proportion is
the Arumeru district in Arusha, Tanzania, which cov-
ers % of all cultivated land (Dinssa et al., ;Wein-
berger & Msuya, ). Arumeru district produces about
.% of all cultivated ANS in Tanzania (Weinberger &
.. . 5
Msuya, ). The presence of national and international
research centers, including the World Vegetable Center,
Eastern and Southern Africa (WVC-ESA), International
Institute of Tropical Agriculture (IITA), and Nelson Man-
dela African Institution of Science and Technology (NM-
AIST), positively promotes cultivation and consumption of
AIVs, including ANS around these regions (Dinssa et al.,
).
ANS is tolerant to abiotic stress under low soil moisture
and heat. Luoh et al. () reported that ANS S. scabrum
retains vitamins and minerals and undergoes less weight
loss at water deficit. Thus, ANS suffers less in water defi-
ciency and becomes a choice of crops under drought condi-
tions in SSA. ANS can take to weeks for the first harvest;
therefore, it is an essential crop to feed the world’s large
population (Dinssa et al., ; Lobell & Gourdji, ).
Rapid urbanization has increased the demand for ANS
in SSA (Ambrose-Oji, ; Shackleton et al., ). There
is considerable scope to increase ANS yield; therefore, vari-
ation between yield obtained in farms and research has
been reported (Dinssa et al., ). This variation further
suggests the importance of technological application for
the intense production of ANS in the farms.
3.3 Factors affecting cultivation of ANS
.. Pests and diseases
Pests and diseases are the main challenges during ANS
production in SSA, resulting in low yields. Fungi, bacte-
ria, and viruses are the main causative agents for ANS dis-
eases. The major fungi diseases include damping-off (Rhi-
zoctonia spp.), early blight (Alternaria solani), late blight
(Pychrithium infestans), fusarium wilt (Fusarium oxyspo-
rum and Fusarium solani), and verticillium wilt (Verti-
cillium dahliae). The bacteria diseases are bacterial wilt
(Ralstonia solanacearum), leaf mold (Cladosporium oxys-
porum), eyespot, and southern blight (Abukutsa-Onyango,
; Ambrose-Oji, ; Dinssa et al., ; Edmonds &
Chweya, ;MoALF/SHEPPLUS,; Nono-Womdim
et al., ; Onyango et al., ; Shackleton et al., ;
Yan g & O jiewo, ).
Pests and diseases damage the leafy structure and reduce
the quality of vegetables, leading to customers’ rejec-
tion (Abukutsa-Onyango, ). Enterobacter mori iso-
lated from ANS pickle (Wafula, ) cause plant bacte-
rial wilt (Zhu et al., ); perhaps they also cause wilt in
ANS. The pest and diseases of ANS are the same as of other
Solanaceae families. Pests and diseases are a significant
problem in Tanzania; however, it becomes more intense
when vegetables are grown for multiple harvests over a
long time or used for seed production (Keller, ).
On the other hand, viruses control insects (aphids,
whiteflies) and inadvertently bruising young leaves by
touching them (Nono-Womdim et al., ;Ojiewo,
Mbwambo, et al. ). The viral diseases include leaf curl
viruses, leaf mosaic viruses, yellow viruses, and tomato
mosaic viruses (Nono-Womdim et al., ; Wafula et al.,
). Tomato mosaic virus (ToMV) is a common virus
found in ANS in SSA (Nono-Womdim et al., ). The
control measures for pathogenic microorganisms include
use of fungicides, disease free seeds, minimizing injury,
avoiding dense planting, using furrow or drip irriga-
tion, and crop rotation. Further, removing infected plants
and destroying them immediately after harvest, avoiding
overfertilization, adequate sanitation, and using healthy
seedlings can control pests and diseases (Nono-Womdim
et al., ).
The most common pests of ANS include aphids (Aphis
sp.), spider mite (Tetranychus evansi Baker), red and
black ants, cutworms, caterpillars (larvae), grasshoppers
(Zonocerus variegatus), whiteflies (Bemisia tabaci), beetles
(Epilachna hirta,Lagria spp., and Podagrica spp.), and
Nematodes (Melodigyne spp.) (MoALF/SHEP PLUS, ;
Nono-Womdim et al., ).
The short shelf life of ANS reduces the market sup-
ply and bargaining power of small-scale farmers and local
open market sellers (Dinssa et al., ; Muhanji et al.,
). Therefore, a multidisciplinary approach is needed
between breeders and postharvest specialists to improve
vegetables’ shelf life and storage conditions. Interventions
through affordable preservation techniques can increase
small-scale farmers’ income and the vegetables’ marketing
(Dinssa et al., ; Muhanji et al., ).
.. Lack of improved cultivars
Lack of improved cultivars limits the high production of
ANS in SSA, resulting in low-yielding cultivars (Dinssa
et al., ). Seed manufacturing companies do not con-
sider the production and marketing of ANS seeds as a
profit-generating business because most AIVs are open-
pollinated, forcing most farmers to produce their seeds
(Dinssa et al., ). Nevertheless, the seeds of improved
ANS cultivars are not available in seed stores of many
regions in SSA, particularly in remote areas (Dinssa et al.,
; Muhanji et al., ). As of recently, some improved
cultivars of S. scabrum and S. villosum are available
to farmers in Tanzania and Kenya for commercial use
(Ronoh et al., ;https://www.tosci.go.tz/publications/
). Besides, several advanced lines of S. villosum and S.
scabrum are available to advance the breeding research of
the crop for improved characteristics such as yield, pests,
and disease resistance (Ronoh et al., ).
6 .. .
.. Other factors
Other factors that hinder the production and con-
sumption of ANS include inadequate rainfall, lack of
knowledge, lack of appropriate storage facilities, low-
quality seeds, drought, fragmented marketing channels,
poor transport infrastructure, agronomic challenges, and
lack of appropriate packaging (Abukutsa-Onyango, ;
Ambrose-Oji, ). For better-improving ANS produc-
tion, researchers should involve farmers as they are key
producers. Improved cultivars are essential because they
require fewer inputs, tolerate pests and diseases, and toler-
ate different climate conditions (Muhanji et al., ).
4NUTRITIONAL AND FUNCTIONAL
BENEFITS OF ANS
4.1 Macro and micronutrients
ANS’ leaves and berries contain a high amount of pro-
tein, carbohydrates, minerals, and vitamins (A, C, E, and B
complex) and could contribute to a healthy diet (Tables
and ; Ambrose-Oji, ; Stoll et al., ; Wafula, et al.,
). The high content of micronutrients is sufficient to
contribute to the recommended daily allowance (RDA)
(Table ). According to Food and Agriculture Organi-
zation of the United Nations (FAO) and World Health
Organization (WHO) (FAO & WHO, ) and Agudo
& Joint FAO/WHO (), the RDA of vegetables and
fruits is g, indicating that ANS consumption alone
can meet the RDA of vitamins C, E, and A, iron, and
manganese. ANSs contain β-carotene (. to . mg/ g
fresh weight basis [FW]) higher than the average level of
various vegetables reported by the USDA National Nutri-
ent Database (Table ; Yuan et al., ). For instance,
g of leaves of ANS can provide over % of the vita-
min A needs of pregnant women (Schreinemachers et al.,
;WVC,). ANS contains a significant amount of B
vitamins including thiamine (. to . mg/ g FW),
riboflavin (. to . mg/ g FW), and folate ( to
μg/ g FW) (Table ). The B vitamins function as
co-enzymes and help in energy production from carbohy-
drates, synthesis of neurotransmitters, fatty acids, and hor-
mones (Blake, ). Also, ANS contains a high content
of vitamin C ( mg/ g FW) and vitamin E (. to
. mg/ g FW), which are natural antioxidants (FAO,
(FAO & WHO, ;Blake,). Young leaves of
ANS have low vitamin C content than matured leaves
(Cheptoo et al., ). Vitamin C prevents scurvy, reduces
gastric cancer, and stabilizes folate in food and plasma.
The dietary intake of mg of vitamin C improves iron
absorption and prevents anemia (FAO & WHO, ).
The ANS leaves are rich in iron (. to . mg/ g
FW), zinc (. to . mg/ g FW), and calcium ( to
mg/ g FW) (Table ). Solanum retroflexum leaves
contain . mg/ g of iron (Sivakumar et al., ). Cal-
cium content at a concentration of - mg inhibited
% iron absorption (FAO & WHO, ). Increasing iron
intake and avoiding foods rich in calcium and iron at the
same time can improve iron absorption (FAO & WHO,
). Calcium contributes to bone development; the defi-
ciency led to the development of osteoporosis. Zinc con-
tributes to the improvement of the immune system and
repairing of cell and organ integrity. Deficiency of zinc in
humans results in growth retardation, bone maturation,
delayed sexual maturity, diarrhea, skin lesions, reduced
appetite, and increased vulnerability to infections (FAO &
WHO, ).
Solanum nigrum leaves contain a high amount of pro-
tein, fiber, and total ash than the same species’ berries.
However, the berries contain more fat and carbohydrates
(Tables and ). In comparison, S. nigrum leaves contain a
high amount of calcium, iron, magnesium, phosphorous,
potassium, sodium, and zinc than the berries (Tables
and ). Also, the leaves of S. nigrum contain a high amount
of vitamins A, C, and B than the berries; besides, the
berries contain a high amount of vitamin B. The high
contents of the macro- and micronutrients present in ANS
leaves suggest that leaves are more nutritious than the
berries despite some nutrients being high in the berries.
Therefore, researches are needed to assess the nutrients
contents of berries in other species of ANS. Notably,
the ANSs’ dense and diverse nutrients can improve
essential nutrients for better health if sufficiently eaten
(Table ).
4.2 Phytochemicals
Phytochemicals are secondary metabolites present in
abundance in various parts of ANS. Total phenols,
carotenoids, glycoalkaloids, and chlorophylls are phyto-
chemicals in ANS (Table )(Neugartetal.,;Nyaga
et al., ;Nyaga,; Yuan et al., ). Solanum
nigrum var. sarrachoides leaves contain flavonoids, alka-
loids, tannins, saponin phenols, phytosterols, coumarins,
and glycosides. In contrast, S. villosum leaves showed all
the phytochemicals, except phytosterols and coumarins
(Nyaga et al., ;Nyaga,). These phytochemicals
are also bioactive compounds in ANS with potential health
benefits. Solanum scabrum contains many carotenoids
such as β-carotenoid, zeaxanthin, and lutein (Odongo
et al., ). Carotenoid content in foods contributes to
.. . 7
TABLE 2 Nutrient content of the raw and processed ANS species
Rawa,e,f,g,j,m Solar dryingg,j BlanchedjFermented Rawe,h,i,k,l,m DriedhBlanchedhFermentednRawe,m Blanched Dried Fermented
Nutrients S. nigrum Mill. S. scabrum Mill. S. villosum Mill.
Moisture (%) . . to . . – . – . – – – – –
Protein (g) . DW/. FW . to . DW . DW –toFW – – to D M . FW – – –
Energy (KJ) – – – – – – – – – –
Fat (g) . DW . DW . DW –. FW – – – . FW – – –
Fiber (g) . FW/. DW – – – . DW . DW . DW – . FW – – –
Dry matter (g) FW – – – . to DW – – . to . DW . – – –
Carbohydrate (g) . DW/. FW to . DW . DW – . DW – – – – – – –
Tot al a sh ( %) . to . DW/. to . FW . to . DW . DW – – – – . DW – – – –
Ca(mg) toFW – – – toDW – – – FW – – –
Fe (mg) . to . FW – . FW – to DW – – – . FW – – –
Mg (mg) to FW – FW – to DW – – – NA – – –
P(mg) to FW – FW – to DW – – – – – – –
K(mg) toFW – FW – FW – – – – – – –
Na (mg) toFW –FW –. FW – – – – – – –
Zn (mg) . to . FW – . FW – . to . DW – – – . FW – – –
Cu (mg) . FW –. FW –. to . DW – – – – – – –
Mn (μg) . FW – . FW – . to . DW – – – – – – –
β-Carotene(mg) . to . FW/DW . to . DW . DW –.toFW/.DW . DW . DW –. FW – – –
Vitamin A (μg) FW – – . FW – – – – – – –
Vitamin C (mg) FW/. to . DW – – – to FW/ to . DW .to.DW .. DW . DW . FW – – –
Vitamin B (mg) . FW/. DW – . FW – – – – . to . DW – – – –
Vitamin B (mg) . to . FW/. DW –. FW – – – – . to . DW – – – –
Vitamin B (μg) to FW – . FW – – – – – – – – –
Vitamin E (mg) . to . DW/. to . FW – – – . to . DW – – . to DM . DW – – –
Note: The nutrients are expressed per g.
Abbreviations: DW, dry weight basis; FW,fresh weight basis.
Sources: eGogo et al. (); aRonoh et al. (); eYuan et al. (); fVan Jaarsveld et al. (); gNyambaka et al. (); hCheptoo et al. (); iMibei et al. ();jTraoré et al. (); kHabwe et al. (); lKirigia et al. (); mYan g and Oj iewo ( ); nWafula ().
8 .. .
TABLE 3 Nutrient content of ANS berry
Nutrients S. nigrum Mill.
Moisture (%) .
Protein (%) . DW/. FW
Fat (%) . DW/. FW
Energy KJ . DW/ . FW
Fiber (%) . DW/ . FW
Carbohydrate (%) . DW/ . FW
Total ash (%) . DW/. FW
Ca (mg) . DW/. FW
Fe (mg) . DW/. FW
Mg (mg) . DW/. FW
P(mg) .DW/.FW
K(mg) . DW/. FW
Na (mg) . DW/. FW
Zn (mg) . DW/. FW
Sulfur (mg) . DW/. FW
Vitamin A (mg) . DW/. FW
Vitamin C (mg) . DW/. FW
Vitamin B (mg) . DW/. FW
Vitamin B (μg) . DW/. FW
Vitamin E (mg) . DW/. FW
Note: The nutrients are expressed per g.
Abbreviations: DW, dry weight basis; FW, fresh weight basis.
Source: Akubugwo et al. ().
health maintenance and risk reduction of various diseases
(Neugart et al., ; Oluoch et al., ). The high con-
tent of β-carotene in ANS contributes to vitamin A produc-
tion, with health benefits in reproduction, vision, immune
function, tissue differentiation, and embryonic develop-
ment (Blake, ; Zempleni et al., ). Younger leaves
of ANS have low β-carotene than matured leaves; how-
ever, matured leaves are rich in carotenoids (Cheptoo et al.,
). Carotenoids help to reduce reactive oxygen species
and prevent some types of cancers. However, they display
a pro-oxidative effect under high concentration, high oxy-
gen tension (lung of smokers), low levels of endogenous
enzymes, and higher levels of metal ions (Fe+and Cu+)
(Park et al., ;Shinetal.,). Usually, β-carotene acts
as a pro-oxidant at higher oxygen partial pressure in cells
and thermally oxidized bulk oil systems (Ha et al., ;
Park et al., ;Shinetal.,). Lutein and zeaxanthin
are carotenoids pigments imparting yellow or orange color
to various foods such as carrots, peppers, fish, and eggs
(Abdel et al., ). Carotenoids protect age-related eye dis-
ease and filter specific wavelengths of light, thus providing
the visual performance and offering photoreceptors pro-
tection from light damage (Abdel et al., ; Eggersdorfer
TABLE 4 The estimated quantity of fresh ANS to meet the
RDA
Micro-
nutrients RDA (mg/day)
EQ of ANS
per day (g)
Quantity of
ANS per
100 g
Thiamine to . to . mg
Riboflavin to. to . mg
Folate μgDFE/day μgDFE
Vitamin C to to mg
Vitamin E . mg
Vitamin A to
μRAE/day
to μRAE
Calcium mg
Iron . mg
Magnesium mg
Phosphorous mg
Potassium mg
Sodium mg
Zinc . mg
Copper . mg
Manganese . mg
Note: EQ represents estimated amount of ANS in grams of fresh weight
required to be eaten to meet the recommended daily allowance. RDA repre-
sents recommended daily allowance. μgDFE represents micro gram of dietary
folate equivalent. μRAE retinal activity equivalency. The vitamins and miner-
als are recommended for a person above and years, respectively. However,
this quantity can vary depending on health status, sex, age, pregnant, and lac-
tating women.
Source: http://www.fda.gov/nutritioneducation;FAO&WHO(); Zem-
pleni et al. (); Van Jaarsveld et al. (); Ronoh et al. ().
& Wyss, ; Raman et al., ). Similarly, they reduced
the risk of cataracts and early age-related macular degen-
eration (Eggersdorfer & Wyss, ; Raman et al., ).
Lutein and zeaxanthin can inactivate free radicals and
oxygen triplicates caused by light-induced cellular activity
(Raman et al., ). Lutein-rich diets improved learning
performance in mice and memory in old men and women
(Eggersdorfer & Wyss, ) and also helped in develop-
ing the infant brain (Perrone et al., ). Still, there are no
established dietary guidelines for lutein required to reach
optimal macular pigment density in healthy people’s eyes
(Eggersdorfer & Wyss, ; Raman et al., ; Ranard
et al., ).
Phenolic compounds concentration in ANS is about
,- , μg/g dry weight basis (DW) whereas
flavonoids, phenolic acids, saponins, and tannins are
widely occurring phenolic compounds in ANS. They act as
antioxidative compounds by scavenging free radicals that
delay or inhibit the initiation step (Amalraj & Pius, ;
Degrain et al., ; Shahidi & Ambigaipalan, ;Yang
.. . 9
TABLE 5 Phytochemicals and antinutritional factors of the leaves of ANS species
Compounds S. nigrum S. scabrum S. villosum References
TPP per g of GAE FW to mg to mg mg Yang and Ojiewo, ;Yuan
et al.,
Quercetin glycosides
(quercetin--rutinoside)
NI to μg/g
DW
NI Neugart et al.,
Carotenoids . to . mg/ g
FW
, mg/ g
DW
μg/g DW Adebooye et al., ;
Odongo et al.,
Flavonoids . mg/ g FW . mg/ g FW . mg/ g FW Yang and Ojiewo,
Glycoalkaloids mg/ g DW NI mg/ g DW Mohy-Ud-Din et al.,
Chlorophyll . to . mg/ g
FW
, to
, mg/ g
DW
, mg/ g DW Adebooye et al., ;
Odongo et al.,
Tannins . mg/ g DW NI NI Amalraj and Pius,
Phytate . mg/ g
DW/. mg/ g
FW
NI . to . mg/ g
DW/. mg/ g
FW
Amalraj and Pius, ;
Mwanri et al.,
Oxalate . mg/ g DW mg/ g DW . to mg/ g DW Amalraj and Pius, ;
Mwanri et al., ;Yang
and Ojiewo,
Cyanogenic glycosidase mg/gFW NI NI Essack et al.,
Nitrates NI NI . to . mg/ g DW Mwanri et al.,
Note: The total glycoalkaloids content was calculated by the sum of (Solasonine, α-Solamargine, β-Solamargine, and α-Solanine).
Abbreviations: DW, dry weight basis; FW, fresh weight basis; NI, not indicated; TPP, total polyphenol; GAE, gallic acid equivalent
&Ojiewo,; Yuan et al., ). Phenolic compounds
possess a wide range of physiological properties, mainly
antiallergenic, antiatherogenic, anti-inflammatory,
antimicrobial, antioxidant, antithrombotic, cardioprotec-
tive, and vasodilatory (Boudet, ; Manach et al., ;
Shahidi & Ambigaipalan, ). The average daily intake
of dietary polyphenols is approximately g per person
(Shahidi & Ambigaipalan, ). The total polyphenol
content of ANS ranges from to mg/ g FW
(Table ). This amount is sufficient to meet the RDA for
the consumption of g of FW ANS. However, high
consumption of polyphenols causes low iron absorption
(Zijp et al., ). Blanching of ANS at ◦Corsteaming
using water or lemon juice solution significantly increases
the total phenolic content (Yuan, Dinssa, et al., ).
Chlorophylls are natural pigments present in ANS. They
act as a natural antioxidant with the ability to scavenge
free radical and prevent several oxidative stress-related dis-
eases such as cancer, neurological disorders, inflammatory
diseases, dermatitis, tissue damage, sepsis, cardiovascular
disorders, decreased immune function, and aging (Lanfer-
Marquez et al., ;Mishraetal.,;Sangija&Wu,
; Wang & Wink, ). Chlorophyll can inhibit cal-
cium oxalate dihydrate formation, which are the primary
sources of kidney stones (İnanç, ). Besides, it stimu-
lates the immune system, helps in detoxification, combats
foul odors, and helps combat anemia and eliminate molds
and toxins in the body (İnanç, ). Despite health ben-
efits, chlorophyll can act as a pro-oxidant for oil oxida-
tion when subjected to light (İnanç, ; Wang & Wink,
). Steaming and water blanching of ANS significantly
increase chlorophyll content of . to . and . to
. mg/ g FW, respectively (Managa et al., ).
Glycoalkaloids are plant-derived bioactive compounds
capable of interacting with living tissue components with
a wide range of likely effects (Huang et al., ). ANS
berries are a rich source of alkaloids. Solamargine and
solasonine are glycoalkaloids in S. scabrum and solaso-
dine glycosides in S. americanum.Solanum scabrum and
S. villosum methanol leaves extracts lack glycoalkaloids
but are present in S. villosum Grif and S. nigrum
PI accessions in a very low concentration of
μg/g DW or mg/ g FW (Yuan et al., ). Alkaloids
have therapeutic effects such as cytotoxic against human
carcinoma cells and anti-inflammatory against psoriasis
(Al-Ashaal, ; Kumar et al., ). It prevented cervi-
cal carcinoma and showed schistosomicidal effect against
S. mansoni, and fasciolicidal effect against Fasciola hepat-
ica. Additionally, it has an inhibitory effect against HSV-
(Al-Ashaal, ). Steroidal alkaloid solanine A from S.
10 .. .
scabrum demonstrated anti-inflammatory activity on Insti-
tute of Cancer Research mice (ICR) or albino mice and
suppressed the production of nitric oxide in lipopolysac-
charide/interferon γ-activated RAW. cells (Zhao et al.,
).
For a long time, phytate is considered an antinutri-
ent, but recent studies have proven its antioxidant prop-
erties (Bhowmik et al., ; Mora-Boza et al., ;
Silva & Bracarense, ; Wang & Guo, ). Phytate
exhibits therapeutic properties on various diseases such
as Alzheimer’s (Abe & Taniguichi, ), Parkinson (Xu
et al., ), and management of blood glucose for type
diabetes(Leeetal.,). Similarly, phytate exhibits
anticancer properties against the prostate (Raina et al.,
), hepatocarcinoma (Al-Fatlawi et al., ), colorectal
(Navarro et al., ), rhabdomyosarcoma (Vucenik, ),
skin (Wawszczyk, ), and breast (Hussein et al., )
cancers. Besides, it acts as an antibacterial against Entero-
coccus faecalis (Nassar & Nassar, ), anti-HIV (Tateishi
et al., ), and hypolipidemic (Dilworth et al., ).
Also, it inhibits lipid peroxidation due to its high affin-
ity to multivalent cations (Mora-Boza et al., ). Phy-
tate is used in food industries as a molecular binder and
functional ingredient, that is, it aggregates proteins and
increases precipitation or turbid (Wang & Guo, ). The
daily intake of – and – g of phytate possess a pre-
vention effect on cancer and antitumor therapies (Vucenik
& Shamsuddin, ). Further studies should explore the
benefits of phytate, such as health and functional benefits,
instead of addressing the general concept of phytate as an
anti-nutrient.
Tannins are a group of phytochemicals (polyphenols)
with an astringent taste and are present in various con-
centrations in vegetables and herbs (Amalraj & Pius, ;
Khanbabaee & van Ree, ). Tannins are water-soluble
polyphenols present in many plant foods. Tannins have
various health benefits such as antioxidants, cardiopro-
tective, anti-inflammatory, antiviral, antibacterial, anticar-
cinogenic, antimutagenic, and antidiabetic (Chung, ;
Delimont et al., ; Khanbabaee & van Ree, ; Sharma
et al., ). They also help heal wounds, cures dysentery,
and help in hardening arteries (Sharma et al., ); nev-
ertheless, it is an antinutrient.
5ANTINUTRITIONAL FACTORS OF
ANS
ANS contains antinutritional factors such as oxalates, tan-
nins, cyanogenic glycosidase, phytate, glycoalkaloids, and
nitrates (Table ) (Amalraj & Pius, ; Essack et al.,
;Mwanrietal.,; Wakhanu et al., ). Some of
them, for example, tannin, phytate, and glycoalkaloids,
exhibit functional properties, for example, anticancer,
antibacterial, antivirus, and anti-inflammatory properties
(Delimont et al., ; Silva & Bracarense, ), also elabo-
rated in Section .. The oxalate and phytate contents vary
with the maturity stage in S. villosum (Silva & Bracarense,
). Solanum villosum (Nduruma BG and Olevolosi
SS ) had the highest oxalate and phytates content, with
a nonsignificant decrease in nitrate content at days
(Mwanri et al., ). Most of the Solanaceae family species
are poisonous to humans and livestock (Jain et al., ).
For instance, the deadly nightshade (Atropa belladonna L.)
contains tropane alkaloids. Solanine glycoalkaloids in S.
nigrum,S. villosum,S. americanum,andS. scabrum sig-
nificantly cause toxicity (Jain et al., ). Notably, var-
ious ANS processing methods such as boiling, drying,
and fermentation effectively remove antinutritional fac-
tors (Essack et al., ).
5.1 Phytate in leaves
Phytate is an antinutrient when present in higher concen-
trations (Bhowmik et al., ). Phytate can chelate with
divalent/trivalent metal ions such as zinc, copper, calcium,
and iron and reduce bioavailability (Silva & Bracarense,
). Solanum nigrum contains the highest phytate con-
tent with the lowest in S. villosum (Table ). The calcu-
lated molar ratio of phytate:iron was . in S. nigrum.An
increase in ANS leaves’ phytate content from . mg/ g
DW in days grown to . mg/ g DW in days was
reported (Mwanri et al., ). Therefore, harvesting at
the right maturity is crucial for ANS nutritional quality.
The molar ratio above . has a significant effect on iron
bioavailability (Dahdouh et al., ;FAO/IZiNCG,).
Therefore, the molar ratio was meager to cause the chelat-
ing effect of iron in ANS. The phytate intakes reported in
the United Kingdom were to mg/day in men and
to mg/day for women. The daily phytate require-
ment for vegetarians is to mg/day (European
Food Safety Authority [EFSA], ). Fermentation, germi-
nation, soaking, malting, boiling, solar, and pressure cook-
ing are simple, inexpensive, and convenient techniques for
the removal of phytates in ANS (Abdulwaliyu et al., ;
Essack et al., ; Owade et al., ; Pasrija & Punia, ;
Rasane et al., ; Wang & Guo, ). Water blanching at
◦C and steam blanching of ANS for min reduce phytate
concentration by % to % (Managa et al., ). Besides,
enzyme degradation using phytase is the most effective
and applicable way to remove phytate (Wang & Guo, ).
Phytate in unprocessed foods does not reflect the actual
quantity consumed; therefore, more emphasis should be
.. . 11
placed on assessing phytate in ready-to-eat foods rather
than its content in raw forms (Abdulwaliyu et al., ).
5.2 Oxalate in leaves
As an antinutrient, oxalate chelates minerals such as potas-
sium, sodium, and calcium, forming insoluble complexes,
thus hindering their absorption. Insoluble calcium oxalate
can cause joint pains, kidney stones, and kidney failure
(Holmes & Kennedy, ; Judprasong et al., ; Soto-
Blanco et al., ). The oxalate content of ANS can go
up to . mg/ g DM (Table ); however, the fatal
doses range from to g per person (Dassanayake &
Gnanathasan, ;EMEA,). The oxalate content in
ANS ranges from . to . mg/ g DW or . to
. mg/ g FW. Solanum nigrum contains the high-
est oxalate content and S. scabrum the lowest (Table ).
This amount is lower than the fatal dose, but it is still
a concern regarding the risk of toxicity; therefore, mon-
itoring ANS leaves’ oxalate levels is necessary. Nonethe-
less, the amount of oxalate in ANS leaves is significantly
lower than in some exotic vegetables (Akhtar et al., ;
Faudon & Savage, ). Fermentation and boiling reduce
oxalate content in ANS and other AIVs (Essack et al., ;
Muchoki et al., ; Owade et al., ; Wakhanu et al.,
). Likewise, blanching at ◦C and steam blanching
for min reduce oxalate in ANS by % to % (Managa
et al., ). Moreover, the early harvesting stages ( days)
show lower oxalate content (. mg/ g DW) than the
late stages of days (. mg/ g DW) (Mwanri et al.,
). Therefore, proper harvesting times and selection of
ANS varieties should be the criteria for obtaining leaves
with low oxalate content.
5.3 Tannins in leaves
Tannin, either nonhydrolyzable (condensed) or hydrolyz-
able (Sharma et al., ), forms a complex with proteins,
digestive enzymes, starches, and minerals, thus reducing
food’s nutritional value (Chung, ; Polycarp et al., ).
Tannin is responsible for decreasing feed intake, feed effi-
ciency, protein digestibility, and net metabolic energy. It
also increases the excretion of protein and essential amino
acids, damages the mucosa lining of the gastrointestinal
tract, and alters cations’ excretion (Chung, ). Tannins
are toxic when precipitating with heavy metals and alka-
loids (Khanbabaee & van Ree, ;Sangija&Wu,).
Tannin causes a browning reaction (darkening of food)
due to polyphenol oxidase (Chung, ). Tannin at a con-
centration of . to g/kg body weight (BW) decreases
erythrocyte counts in pigs’ hemoglobin and hematocrit
(Lee et al., ). Tannin content above g/ g caused
mortality in test chicks (Chung, ). Tannin also causes
liver, skin, oesophageal, stomach, lung, kidney, and nasal
cancers in humans (Chung, ). The RDA of proan-
thocyanidin (tannin) is . to mg/person/day and
mg/person/day for hydrolyzable tannins in the Span-
ish population. Nevertheless, the total tannin content of S.
nigrum of . mg/ g DW or . mg/ g FW is rel-
atively low to harm the consumers. Therefore, consump-
tion of ANS is safe with potential health effects. In case
of sufficient tannin content to cause potential health prob-
lems, cooking is an effective removal method because it
is heat-labile and facilitates its degradation (Essack et al.,
; Kakati et al., ; Owade et al., ; Serrano et al.,
). Further, lactic acid fermentation, drying, canning,
boiling, soaking in water, and freezing can also remove
tannins (Essack et al., ; Serrano et al., ). Managa
et al. () reported a decrease in tannin content by % to
% through blanching at ◦C and steam blanching for
min.
5.4 Nitrates/nitrites in leaves
Fruits and vegetables are the significant nitrate/nitrite
sources and contribute % to % of overall dietary
intake (EFSA, ; Nuñez et al., ). Several fruits and
vegetables contain to mg of nitrate per kilo-
gram (WHO, ). Nitrates/nitrites are easily absorbed
in the body; about % to % are excreted in the urine,
whereas % appear in the urine as urea and ammonia
(Karwowska & Kononiuk, ). In the stomach, blood,
and tissue, nitrates are converted into bioactive reactive
nitrogen oxide species (NO). The reactive NO contributes
to the formation of carcinogenic nitrosamines of toxico-
logical importance (Ding et al., ). Nitrates can con-
tribute to carcinogenic, such as breast cancer, gastric can-
cer, renal cell carcinoma, adult glioma, colorectal can-
cer, esophageal cancer, and thyroid cancer (Karwowska
& Kononiuk, ; Keszei et al., ;Yangetal.,).
Besides, it contributes to genotoxicity, cytotoxicity, inhi-
bition of enzymatic reactions and proteolysis, and altered
immunogenicity (D’Ischia et al., ). Antioxidants, such
as vitamins C and E, inhibit nitrosamines’ generation
(Ding et al., ; Karwowska & Kononiuk, ). Mwanri
et al. () reported the nitrate content of to mg/kg
DW in S. villosum; however, there is limited information on
leaves of other ANS species. Some exotic vegetables such
as spinach, rucola, celery, rhubarb, lettuce, beets, chard,
and beetroot contain significantly higher nitrates than
ANS (Karwowska & Kononiuk, ). Seasonality and the
cultivation systems contribute to nitrites variation in
ANS. Late harvested Nduruma BG and Olevolosi SS
12 .. .
showed lower nitrate content than early harvested
ones (Mwanri et al., ). Similarly, the nitrate con-
tent was higher in -day harvested leaves ( mg/kg
DW/. mg/kg FW and significantly lower at day
( mg/kg DW/ mg/kg FW) (Mwanri et al., ).
Therefore, farmers should consider late harvest for lower
nitrate content in ANS. Human generally consumes
between . and . mg of nitrite daily (WHO, ). The
RDA of nitrite and nitrates is . to . mg/kg BW/day
and mg/kg BW/day, respectively (Karwowska & Konon-
iuk, ).
Therefore, the nitrate content in ANS leaves is low com-
paring to the RDA (Table ). Besides, the consumption of
more than to g of ANS per day is beyond the RDA
of nitrate and can cause health effects. The application of
heat treatments, high-temperature storage conditions, and
fermentation reduced nitrate content in vegetables (Ding
et al., ; Prasad & Chetty, ), similarly to ANS leaves.
5.5 Glycoalkaloids in leaves
The solasonine, solanine, solamargine, and chaconine are
major glycoalkaloids in the ANS, with steroidal glycoal-
kaloids (SGAs) as minor (Ronoh et al., ). Glycoalka-
loids are toxic to humans and animals with symptoms
such as constipation, dark-colored diarrhea, nausea, vom-
iting, and abdominal pain. These toxins affect the nervous
system to cause drowsiness, apathy, weakness or paraly-
sis, salivation, circulatory and respiratory depression, and
unconsciousness. Toxic effects are primarily irritation of
the digestive tract and sometimes neurological problems.
(Abbas et al., ; Defelice, ; Mensinga et al., ).
Young leaves and unripe berries of ANS have a higher
SGA concentration than matured ones (Ronoh et al., ).
The SGA is associated with bitterness in ANS and causes
toxic effects to animals when consumed above mg/kg
BW (Ronoh et al., ). The recommended upper limit of
total glycoalkaloids (TGA) in plant foods is mg/kg FW
( g/kg DW) (Nono-Womdim et al., ). Alkaloid content
in S. nigrum and S. villosum is and mg/ g DW,
respectively (Table ).The quantity of solanine in S. nigrum
and S. villosum is and mg/ g DW, respectively
(Mohy-Ud-Din et al., ). This content is significantly
low to cause a potential toxic health effect on humans.
Also, Yuan et al. () reported a solasodine content of
less than mg/ g DW and mg/ g FW in S. nigrum
and S. scabrum, respectively. This amount is low compared
to other vegetables such as eggplant (. to . mg/ g
FW) (Yuan et al., ). The SGA solasodine is absent in
S. scabrum (Yuan et al., ; Yuan, Dinssa, et al., ).
According to Yuan, Lyu, et al. (), the levels of total
alkaloids in S. nigrum,S. villosum,andS. scabrum are safe
for human consumption. Alkaloids content in ANS leaves
can be removed by boiling (Defelice, ; Edmonds &
Chweya, ; Essack et al., ). The TGA content in S.
scabrum,S. villosum,andS. tarderemotum leaves is .,
., and . mg/kg FW, respectively, with no maxi-
mum toxic levels of SGAs (Mwai, ). It is noteworthy
that several factors such as the amount of TGA eaten, BW,
and metabolism rate of SGA facilitate its toxicosis (Nono-
Womdim et al., ).
Breeding and genetic improvement would also remove
the toxicity commonly associated with ANS, that is, mainly
attributed to SGA presence (Nono-Womdim et al., ).
Although SGAs are harmless and enhance the flavor at
low levels, they cause toxicity and even death in ani-
mals and humans at a high dose. TGA content above
mg/kg FW is associated with unpleasant flavor and
bitter taste (Nono-Womdim et al., ). In Tanzania and
Kenya, several improved cultivars of S. scabrum and S. vil-
losum are available (https://www.tosci.go.tz/; Dinssa et al.,
; Ojiewo, Mbwambo, et al., ; Ronoh et al., ).
Solanum scabrum has a less bitter taste with large suc-
culent and broad leaves (Figure ), high seed yield, rapid
new leaf sprouting after harvest, late flowering, and
days’ maturity, and picking can continue for to weeks.
Besides, it is resistant to Fusarium wilt (Nono-Womdim
et al., ; Ojiewo, Mbwambo, et al., ;https://www.
tosci.go.tz/). Solanum villosum is bitter, with a narrow and
low yield than S. scabrum;also,ithasbroadleavesandhigh
yield than the original variety (Figure ). People in rural
areas, old peoples, and men prefer bitter variety; there-
fore, all varieties fetch the same demand in the market.
Nduruma and Olevolosi leaves contain no glycoalkaloid
aglycone; therefore, they are safe for consumption. More-
over, these varieties have high total phenols and high vita-
min E and β-carotene (Yuan et al., ).
5.6 Glycoalkaloids in berries
ANS berries are commonly considered toxic and not con-
sumed in SSA (Lyu et al., ). The young berries of S.
nigrum contain the highest level of SGA compared with
the whole plant or leafy and stem parts (Abbas et al.,
; Defelice, ; Edmonds & Chweya, ; Mohy-Ud-
Din et al., ; Ronoh et al., ;Yang&Ojiewo,).
The toxic level of matured berries is too low to harm but
can harm children (Defelice, ; Edmonds & Chweya,
). Solanum nigrum accession (USDA PI ) con-
tains trace levels of glycoalkaloids (Lyu et al., ). How-
ever, the glycoalkaloids (solasodine, solanine, and sola-
margine) are high in berries compared to shoots and leaves
of S. nigrum, with solasonine being high in the shoots of S.
nigrum (Al-Ashaal, ). Glycoalkaloids in unripe berries
.. . 13
of S. nigrum are equivalent to mg/ g DW. Envi-
ronment conditions such as frost contribute to a signifi-
cant increase in glycoalkaloids by five to times higher
than mature berries. Yuan, Lyu, et al. ()reporteda
solasodine content of to mg total aglycone/ g
DW in unripe berries but was not detected in ANS leaves.
This variation could be attributed to genetic diversity,
environmental conditions, and cultural practices (Ojiewo,
Mwai, et al., ). Glycoalkaloid concentration is low in
matured berries. Solanum scabrum mature berries contain
up to mg of glycoalkaloids (Yuan et al., ). Such
a high concentration of glycoalkaloids in berries could be
essential for medicinal purposes (Al-Ashaal, ). Mature
berries of some accessions contain low amounts of glycoal-
kaloids and could be potential for consumption in SSA.
For such, the promotion of berry products for consump-
tion is essential. Therefore, intensive research in breed-
ing for selecting desirable lines and subsequent cultivars
for release ensuring the quality of the final product and
safety to consumers is mandatory (Yuan, Dinssa, et al.,
; Yuan, Lyu, et al., ).
5.7 Cyanogenic glycosidase in leaves
When hydrolyzed, cyanogenic glycosidase produces the
toxic hydrogen cyanide (HCN) (Selmar, ). Only S.
nigrum contains cyanogenic glycosidase (Table ), which is
of safety concern. HCN inhibits cytochrome oxidase in the
mitochondria. Also, it interacts with copper and iron ions
to inhibit respiration and the inability to produce adeno-
sine triphosphate (Sangija & Wu, ). Cyanide intoxica-
tion can cause mental confusion, diarrhea, vomiting, stom-
ach pains, dizziness, diaphoresis, cardiac arrest, and rapid
respiration (Gracia & Shepherd, ;Venketesh,).
A chronic low dose of cyanide may cause an elevation in
the blood and induces a variety of symptoms such as kid-
ney or mild liver damage (Manzano et, al., ), mis-
carriage (Soto-Blanco et al., ), hypothyroidism (Soto-
Blanco et al., ), paralysis, nervous lesions, and weak-
ness (Soto-Blanco et al., ,). The fatal dose of
HCN can be as low as . to . mg/kg/BW (EFSA, ;
Essack et al., ). In contrast, the cyanide content of S.
nigrum is mg/ g FW (Essack et al., ); more-
over, no information is available for other ANS species.
HCN content in ANS is significantly low compared to
that in raw cassava leaves ( mg/kg) (Umuhozariho
et al., ). FAO () suggested an acceptable limit of
mg/kg HCN, whereas the EFSA () considers the
maximum of mg/kg HCN to be safe for human con-
sumption. Fresh ANS contains low HCN content to cause
potential health effects as per (FAO, ). Cassava leaves’
cooking reduces HCN similar to ANS (Umuhozariho
et al., ).
6 SAFETY REGULATIONS FOR ANS
ANS safety is still a challenge, with a risk of toxicity to con-
sumers if consumed at a high dose. Some ANS leaves acces-
sions contain glycoalkaloids, potentially causing health
concerns (Sivakumar et al., ). To date, there are no
policy issues, regulations, or bay laws guiding the safety of
consuming ANS in SSA or other parts of the world (Nono-
Womdim et al., ). Therefore, the SSA countries need
to develop and implement policies and strategies to pro-
mote sustainable production and ANS safety (Abukutsa-
Onyango, ). There is a need for policy-makers at the
national, regional, and international levels to address the
significant safety issues on ANS to attain maximum ben-
efits. The EFSA, FAO, and WHO have set guidelines for