Worldwide plants have been used for curative purposes from
time immemorial. It is estimated by WHO that 80% of the population
majority of this in developing countries, still rely on plant-based
medicine for primary healthcare Evans [1]; Farnsworth [2]. WHO
further estimated that over 80% of the population residing in
developing countries depends directly on plants for their primary
medical requirements Czygan [3]; WHO [4]. This is attributed to
the fact that plant-derived medicines can be easily accessed and are
also cheap Amin et al. [5]; Ramawat et al. [6]; WHO [5]. The use of
some crude extracts whose specific evaluations have not been done
could lead to serious complications, overdose and intake of toxic
substances [7-10]. Ineffective herbs could also be used as a matter of
belief or tradition Baker et al. [11]. In most countries, use of herbal
medicine continues to coexist with modern Pharmacology Ernest
[12]. The worldwide upsurge in the use of herbal preparations and
active ingredients isolated from medicinal plants in healthcare
Jassim et al. [13] is due to increased side effects, lack of curative
treatment for several chronic diseases, high cost of new drugs,
microbial resistance and emerging diseases Humber [14].
This is indicated by the growing popularity of Traditional
Chinese Medicine (TCM) and Ayuverdic medicine of India Jiang et
al. [15]; Dubey et al. [16]. In Africa, the use of traditional medicine
is very high as indicated by the fact that between 70 and 80% of the
population depend on herbal preparations for primary healthcare
with little or no scientific information on efficacy and side effects
Kokwaro [17-25]. Furthermore, even the people of the developed
world are also dependent directly or indirectly on plants for
their health care. In the United States, 25% of the prescriptions
given from community pharmacies consisted of plant extracts
or active ingredients of plant origin Cragg et al. [26]. In Dares Salaam, Tanzania, 21% of patients who visited public Hospitals
had consulted a traditional healer before they came to hospital De
Boer et al. [27]. Plant-derived medicines are offered/taken in the
form of tinctures, teas, poultices and powders, depending on the
knowledge of the use and application method of a particular plant
for a given ailment Fennell et al. [28]; Balunas et al. [29].
It has also been demonstrated in food that Plant extracts like
Polyphenols can successfully be used in food conservation thus
extend self-life of such products that could otherwise go to waste
due to spoilage Papuc et al. [30]. In Kenya, debate on incorporation
of traditional medicine into primary health care has been going
on for a while now [31-40]. There is an attempt to make a law to
regulate the practice of traditional medicine by way of legislation.
The Traditional Health Practitioners Bill, 2014 was published on the
February 2014 and was tabled before the National Assembly by the
then Chairperson of the Health Committee Rachael Nyamai. The Bill
went through the first reading on 3rd June 2014 and the Committee
further tabled its report on the deliberations regarding the said bill
on 25th April 2015 but since then there has been no progress. If the
Bill is passed into law it seeks to provide for the training, regulation
and licensing of traditional practitioners so as to regulate their
practice. Further, it seeks to set up traditional health practitioners’
council which is a body mandated with regulation. It also seeks to
set up a Disciplinary Committee that will discipline practitioners as
well as setting offenses and penalties under the said law [41-47].
Traditional societies in Africa had devised methods of providing
every individual in the community with essential healthcare
through acceptable and accessible means by the application
of indigenous resources such as plants, animals and minerals
Chhabra et al. [47]. Besides, herbal medicine takes into account every country’s socio-cultural background. the western societies
have capitalized on this fact to the ignorance of other societies and
either using the plant products . Of late, despite emphasis being put
in research of synthetic drugs, a certain interest in medicinal plants
has been reborn [48,49]. This is partly due to the fact that many
synthetic drugs are potentially toxic and not free of side effects
on the host and that the effectiveness of many herbal medicines is
now an accepted fact Thomson [50]; Geddes [51]. Further, herbal
preparations constitute valuable natural resource from which
chemicals of great potential interest for medicine, agriculture,
industry and other areas can be identified and isolated [52-65].
Such valuable drugs such as atropine (1), reserpine (2), quinine
(3) and morphine (4) were discovered from traditional herbal
remedies (Figure 1) Sneader [66], Ji et al. [67].
Figure 1: Traditional Herbal Remedies.
It is estimated that about 25% of the drugs prescribed
worldwide are derived from plants and 121 such active compounds
are in use Sahooetal [68]. Between 2005 and 2007, 13 drugs
derived from natural products were approved in the United States.
More than 100 natural product-based drugs are in clinical studies
Li et al. [69], and out of the total 252 drugs in the World Health
Organization’s (WHO) essential medicine list, 11% are exclusively of
plant origin Sahooetal [68]. Microbiologists all over the world have
been prompted to search for formulations of new antimicrobial
agents and evaluation of the efficacy of natural plant products as
a substitute for chemical antimicrobial agents Pandian et al. [70]
Such moves have been prompted by insurmountable resistances to
antibiotics that have been experienced in the past [71-85]. Many
microorganisms and plants produce compounds that are not
related to the basic metabolism of the producing organism called
secondary metabolites as their defense mechanism. Many of these
products play important roles as therapeutics and stimulants feed
additives among others, Hans [86].
Medicinal plants are well-known natural sources for the
treatment of various diseases since antiquity [87-90]. About
20,000 plant species used for medicinal purposes are reported by
the World Health Organization (WHO) Gullece et al [91]; Maregesi
[92]. Furthermore, natural products, either crude compounds, or
as standardized plant extracts, provide unlimited opportunities
for new drug leads because of the unmatched availability of
chemical diversity Cos et al. [93]. In the past, the wide range of
antimicrobial agents from lower organisms and synthetic drugs
sufficed in the treatment or control of infectious diseases, but
currently there is a problem of microbial drug resistance and there
is an increase of opportunistic infections especially with acquired
immune deficiency syndrome (AIDS) patients and individuals on
immunosuppressive chemotherapy. Many antifungal and antiviral
drugs are of limited use due to toxicity, while other viral diseases
have not yet found a cure [94-100]. These problems pose a need of
searching for more new drug substances. Most of the plants used traditionally for treatment of various ailments locally have not been
studied scientifically for their efficacies and side effects Kokwaro.
Ethno-botanical information is slowly dying out due to lack
of vertical transmission to young generation as people holding
the information on these plants are fast dying out. There is also
imminent loss of some of these plant species due to population
pressure and over exploitation without proper conservation
policies. Preparations, handling and storage of crude extracts
from these plants could lead to decomposition or transformation
into ineffective and/or harmful products Baker et al. [19], Dutra et
al. [101]. In Africa, data available, indicate that medicinal plants
can also be used to earn foreign exchange by exporting them to
the western world Busia. It has been documented that the huge
pharmaceutical significance of many tropical medicinal plants could
be utilized to generate foreign exchange as well as to create jobs for
many African countries [102-105]. This shows that the vast field
of medicinal plants on the African continent, if harnessed, could
rescue the struggling healthcare systems of most such countries
Mahomoodally [106]. Some lifesaving medicines like antibiotics
have their roots in plants.
Antibiotics
With the discovery of microorganisms as the causative agents
of infectious diseases, many substances including those of plant
origin became recognized as “antiseptics”. These are substances
having the ability to inhibit the growth of microorganisms. Later on,
this term was changed to “antibiotics” from the term “antibiosis”,
which describes antagonism between different species and even
between members of the same species in nature [107-110]. An
antibiotic is a biochemical drug, derived from one or more kinds
of microorganisms. It may have the ability to inhibit the growth of
(bacterial static agent) or to kill (bactericidal agent) a number of
other microorganisms. This makes antibiotics be of immense value
in the treatment of a number of diseases that result from microbial
infection Amit et al. [113]. Antibiotics, also known as antimicrobial drugs are therefore drugs that fight infections caused by bacteria,
either by inhibiting the growth of or by destroying these microbes.
Their therapeutic success relies on their pharmacokinetic behavior
and the contribution that the host’s own defenses are able to make
towards clearance of the offending microorganism Amit et al. [113].
Bacteriostatic Agents
After the discovery of Penicillin in 1929, it was a wonder
drug and an immediate solution to bacterial infections. Since the
several derivatives have discovered or synthetically evolved in
laboratories that also led to their categorisation into Bacteriostatic
and Bactericidal agents. Bacteriostatic agents are substances
that inhibit the growth of other microorganisms by interfering
with bacterial protein production, bacterial DNA production and
bacterial cellular metabolism (Figure 2). Bacteriostatic antibiotics
inhibit growth and reproduction of bacteria without killing them
and killing is done by the bactericidal agents. Examples of synthetic
bacteriostatic agents include; sulphonamides like furosemide
(5), trimethoprim (6), tetracycline (7), chloramophenicol (8) and
erythromycin (9) and their derivatives among others Sritharan et
al. [114].
Figure 2: Bacteriostatic agents.
Bactericidal Agents
Bactericides act as disinfectants, antiseptics or antibiotics
(Figure 3). They include; benzylpenicillin (10), cephalosporins
like cefalexin (11) and amino-glycosides like gentamicin (12)
(Sritharan and Sritharan, 2004). Effective chemotherapy in the use
of antibiotics depends upon selective toxicity, which is their ability
to inhibit microorganisms at concentrations tolerated by the host
Amit et al. [113].
Figure 3: Bactericidal agents.
Active Compounds in Plant Extracts
Plants produce biologically active secondary metabolites
often with highly complex chemical structures. These compounds
are concerned with survival of the plants and are known to have
antimicrobial activity Waterman [115]. The compounds vary from
plant to plant and are found to be in different concentrations in
different parts of the same plant Lawrence [116]. The combined
effects of the health-related challenges due to the rapidly growing
population, emergence of antimicrobial resistant pathogenic
strains to frequently used commercial drugs such as penicillin,
increased side effects, the failure of modern medicine to provide
effective treatment, high cost of new drugs and emerging diseases,
research into natural products with anti-microbial activity is being
pursued in earnest. It is of importance to establish a scientific basis
for the use and validation of medicinal plants through biological
screening. Populations living in developing countries depend
directly on herbal drugs and traditional medicines for primary
healthcare WHO [4].
Many of the drugs which are in use today were discovered
through their ethno-botanical route Kareru et al. [117]. Moreover,
pathogen resistance to existing drugs coupled with increased side
effects, lack of curative treatment for several chronic diseases, high
cost of drugs and emerging diseases is very common in today’s world
Humber [14]. This makes it necessary to research on medicinal
plants in order to obtain more and potent pharmacological agents
owing to the fact that natural products and their related moieties
have historically been incredible as a source of therapeutic agents
Koehn et al. [118].
ISSN: 2574 -1241
Abstract
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