Plant Extracts Used to Manage Bacterial, Fungal, and Parasitic
Infections in Southern Africa
Jacobus Nicolas Eloff and Lyndy Joy McGaw
Summary
Infectious diseases are prevalent in many areas of the world, particularly in devel-
oping countries. With the high incidence of acquired immune deficiency syn-
drome (AIDS) in many sub-Saharan African countries, opportunistic pathogens
such as Candida albicans and Cryptococcus neoformans, as well as other fungal, bac-
terial, and parasitic infections, are becoming major health problems. Added to this
problem is the deficiency of health care clinics adequately equipped to cope with
these challenges. Southern Africa has a long history of medicinal plant use by tra-
ditional healers and other community members to combat infections in humans
and animals. As a consequence of the widespread use of a diverse array of plants to
treat infectious diseases, coupled with the renowned plant diversity in South Afri-
ca, we have spectacular potential to discover anti-infective activity in extracts of
these plants.
Many methods may be used to select plants for bioactivity testing, including eth-
nobotanical and ethnoveterinary leads, random selection and chemotaxonomic ap-
proaches. In the Phytomedicine Programme we have concentrated on investigating
species belonging to the family Combretaceae, yielding much useful information
about biological activity relationships in the family. Traditional uses of plants and
random screening have also proved their value as methods of plant selection for
phytomedicinal investigations. Our aim is two-pronged: first to bring to light high-
ly active plant extracts, and second to concentrate on using bioassay-guided fraction-
ation to isolate and identify the chemical constituents responsible for activity.
The bioassays forming the focus of our investigations comprise antibacterial,
antifungal, and antiparasitic activity tests, among others. The antibacterial and
antifungal test organisms include Gram-negative and Gram-positive bacteria rec-
ommended by the United States National Committee for Clinical Laboratory Stan-
dards (NCCLS), various fungal species (plant, animal, and human pathogens), as
well as Mycobacterium species and methicillin-resistant Staphylococcus aureus.
Plant extracts are tested for antiparasitic activity against the animal helminth para-
sites Haemonchus contortus and Trichostrongylus colubriformis, as well as against the
97
free-living nematode Caenorhabditis elegans. To ensure that biological activity is not
due to a general toxic effect, we also carry out cell line cytotoxicity studies and the
brine shrimp larval mortality assay. Toxicity screening in laboratory systems is a
necessary aspect of the preliminary safety evaluation of plant-derived extracts and
compounds prior to further development and commercialization.
Bioassay-guided fractionation on crude plant extracts with excellent activity in our
laboratories has successfully yielded isolated active compounds with some potential
for commercialization. Extracts from plants which have been developed and potent-
ized without isolation of constituents have many applications, particularly where it
appears that a number of compounds in the extract may have synergistic effects.
Herbal extracts and isolated compounds with biological activity discovered in
our group are being applied to the development of treatments for human and ani-
mal diseases. Tests in vivo performed thus far have identified extracts and com-
pounds with exceptional antibacterial and antifungal activity. In addition, we are
investigating antifungal compounds in plant extracts that assist in protecting culti-
vated plants from fungal attack. These successes emphasize the potential value of
newly developed plant products, particularly from a region as rich in plant biodi-
versity as South Africa.
We conclude that there is a much better opportunity to develop commercially
useful products by focusing on plant extracts rather than the isolated compounds.
5.1
Introduction
Southern Africa is fortunate to possess a remarkable diversity of indigenous
plants, coupled with rich cultural traditions on the use of plants for medicine. The
lack of easy access to Western primary health care and veterinary services in many
rural parts of the country has supported the use of traditional medicine to treat
both humans and animals. Even where clinics and orthodox medicines are readily
available, a large proportion of the population uses traditional medicines together
with, or in preference to, Western medicine. Exploration of the uses of plants af-
fords scientists a rich source of research opportunities in disease control, particu-
larly infectious diseases which are so prevalent in the developing world. Research
targeted at investigating the biological activity and potential toxicity of medicinal
plants is a priority, not only in South Africa but worldwide.
As an example of South African research on the use of plants for treating infec-
tions in animals and humans we focus on the Phytomedicine Programme (Depart-
ment of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretor-
ia, website http://www.up.ac.za/academic/veterinary/depts_paracl_phyto.htm).
Reference will be made where possible to related research projects occurring in
other groups in the country. There are several recent reviews available on the stat-
us of South African ethnobotanical, phytochemical, and pharmacological investi-
gations. These reviews provide detailed information about research projects in oth-
er groups working on various aspects of medicinal plant use [1–4].
98 5 Plant Extracts Used to Manage Bacterial, Fungal, and Parasitic Infections in Southern Africa
In this chapter a number of general aspects will be discussed followed by proce-
dures that we have used to deliver products that are patented and licensed to be
used in industry. We will share our experience and shortcuts that we have devel-
oped.
Infections in Southern Africa
Jacobus Nicolas Eloff and Lyndy Joy McGaw
Summary
Infectious diseases are prevalent in many areas of the world, particularly in devel-
oping countries. With the high incidence of acquired immune deficiency syn-
drome (AIDS) in many sub-Saharan African countries, opportunistic pathogens
such as Candida albicans and Cryptococcus neoformans, as well as other fungal, bac-
terial, and parasitic infections, are becoming major health problems. Added to this
problem is the deficiency of health care clinics adequately equipped to cope with
these challenges. Southern Africa has a long history of medicinal plant use by tra-
ditional healers and other community members to combat infections in humans
and animals. As a consequence of the widespread use of a diverse array of plants to
treat infectious diseases, coupled with the renowned plant diversity in South Afri-
ca, we have spectacular potential to discover anti-infective activity in extracts of
these plants.
Many methods may be used to select plants for bioactivity testing, including eth-
nobotanical and ethnoveterinary leads, random selection and chemotaxonomic ap-
proaches. In the Phytomedicine Programme we have concentrated on investigating
species belonging to the family Combretaceae, yielding much useful information
about biological activity relationships in the family. Traditional uses of plants and
random screening have also proved their value as methods of plant selection for
phytomedicinal investigations. Our aim is two-pronged: first to bring to light high-
ly active plant extracts, and second to concentrate on using bioassay-guided fraction-
ation to isolate and identify the chemical constituents responsible for activity.
The bioassays forming the focus of our investigations comprise antibacterial,
antifungal, and antiparasitic activity tests, among others. The antibacterial and
antifungal test organisms include Gram-negative and Gram-positive bacteria rec-
ommended by the United States National Committee for Clinical Laboratory Stan-
dards (NCCLS), various fungal species (plant, animal, and human pathogens), as
well as Mycobacterium species and methicillin-resistant Staphylococcus aureus.
Plant extracts are tested for antiparasitic activity against the animal helminth para-
sites Haemonchus contortus and Trichostrongylus colubriformis, as well as against the
97
free-living nematode Caenorhabditis elegans. To ensure that biological activity is not
due to a general toxic effect, we also carry out cell line cytotoxicity studies and the
brine shrimp larval mortality assay. Toxicity screening in laboratory systems is a
necessary aspect of the preliminary safety evaluation of plant-derived extracts and
compounds prior to further development and commercialization.
Bioassay-guided fractionation on crude plant extracts with excellent activity in our
laboratories has successfully yielded isolated active compounds with some potential
for commercialization. Extracts from plants which have been developed and potent-
ized without isolation of constituents have many applications, particularly where it
appears that a number of compounds in the extract may have synergistic effects.
Herbal extracts and isolated compounds with biological activity discovered in
our group are being applied to the development of treatments for human and ani-
mal diseases. Tests in vivo performed thus far have identified extracts and com-
pounds with exceptional antibacterial and antifungal activity. In addition, we are
investigating antifungal compounds in plant extracts that assist in protecting culti-
vated plants from fungal attack. These successes emphasize the potential value of
newly developed plant products, particularly from a region as rich in plant biodi-
versity as South Africa.
We conclude that there is a much better opportunity to develop commercially
useful products by focusing on plant extracts rather than the isolated compounds.
5.1
Introduction
Southern Africa is fortunate to possess a remarkable diversity of indigenous
plants, coupled with rich cultural traditions on the use of plants for medicine. The
lack of easy access to Western primary health care and veterinary services in many
rural parts of the country has supported the use of traditional medicine to treat
both humans and animals. Even where clinics and orthodox medicines are readily
available, a large proportion of the population uses traditional medicines together
with, or in preference to, Western medicine. Exploration of the uses of plants af-
fords scientists a rich source of research opportunities in disease control, particu-
larly infectious diseases which are so prevalent in the developing world. Research
targeted at investigating the biological activity and potential toxicity of medicinal
plants is a priority, not only in South Africa but worldwide.
As an example of South African research on the use of plants for treating infec-
tions in animals and humans we focus on the Phytomedicine Programme (Depart-
ment of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretor-
ia, website http://www.up.ac.za/academic/veterinary/depts_paracl_phyto.htm).
Reference will be made where possible to related research projects occurring in
other groups in the country. There are several recent reviews available on the stat-
us of South African ethnobotanical, phytochemical, and pharmacological investi-
gations. These reviews provide detailed information about research projects in oth-
er groups working on various aspects of medicinal plant use [1–4].
98 5 Plant Extracts Used to Manage Bacterial, Fungal, and Parasitic Infections in Southern Africa
In this chapter a number of general aspects will be discussed followed by proce-
dures that we have used to deliver products that are patented and licensed to be
used in industry. We will share our experience and shortcuts that we have devel-
oped.
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