Screening of Indigofera lupatana Baker F. root extracts for antibacterial activities

Abstract

Herbal remedies as cheap alternatives to conventional
medicine have contributed significantly to rural
livelihoods. Apart from the traditional healers
practicing herbal medicine, many people are involved in
collecting and trading medicinal plants. The World
Health Organization (WHO) estimates that 80% of the
world’s population depends on medicinal plants for
their primary health care (Mothana et al, 2008; Ngoci et
al, 2011). The use of traditional medicine has been
explored globally and is widely used in developing
countries as an alternative or to complement
conventional medicine (Rates, 2001; Gupta et al, 2010).
Natural products, either as pure compounds or as
standardized plant extracts, provide exceptional
opportunities for new drug leads because of the
unmatched chemical diversity of naturally derived
compounds (Cowan, 1999; Parekh and Chanda, 2007;
Mariita et al, 2010; Ngoci et al, 2011). Scientific interest
in medicinal plants has burgeoned due to the
recognized efficacy of plant derived drugs and everpresent
concerns about the side effects of modern
medicinal substances. This has fuelled the intensive

investigation of new molecular structures from the
plant kingdom as potential medicinal compounds
(Mariita et al, 2010). As a result, drugs derived from
unmodified natural products or semi-synthetic drugs
obtained from natural sources accounted for 78% of the
new drugs approved by the United States Food and
Drug Administration (FDA) between 1983 and 1994
(Suffredini et al, 2006; Ngoci et al, 2011). This
underscores the importance of screening natural
products.
Infectious diseases are a leading cause of human and
animal mortality. This is further aggravated by the rapid
development of multi-drug resistance to available antimicrobial
agents (Doughart and Okafor, 2007; Ngoci et
al, 2011), their limited anti-microbial spectrum, their
side effects (Huie, 2002), and emergence and reemergence
of opportunistic infections. Therefore,
studies aimed at identifying and characterizing of the
substances that exhibit activity against infectious microorganisms,
yet showing no cross resistance with
existing antibiotics, are required (Olila et al, 2001). In
recent years, pharmaceutical companies have focused
on developing drugs from natural products that
promises to counter the limitations of conventional
antibiotics (Doughart and Okafor, 2007).
The bio-activity of natural products is due to
phytochemicals, a group of secondary metabolites often
elaborated for the plant defense against pests and
herbivores or to gain an advantage over competing
agents. These phytochemicals inadvertently also protect
humans against pathogens (Ngoci et al, 2011). Some
phytochemicals are known to have antimicrobial
properties, immune-modulative properties, provide
nutrition for normal cell health and repairs, inhibit
carcinogens and act as antioxidants.
Indigofera lupatana Baker F., locally called ‘mugiti’ by
the Mbeere community in Kenya, is a woody shrub
found in Acacia-Combretum ecological zones of Mbeere.
It is widely used for its perceived medicinal value in
treating coughs and diarrhea (Riley and Brokensha,
1988; Ngoci et al, 2011), gonorrhea and pleurisy
(Kokwaro, 1993; Ngoci et al, 2011).
There is apparently no documented scientific report on
anti-microbial properties of this plant. This lack of
scientific corroboration has often constituted a major
constraint to the consideration of the use of herbal
remedies in conjunction with or as an affordable
alternative to conventional medical treatment (Okeke et
al, 2001). Knowledge of the chemical constituents of
plants is desirable not only for the discovery of
therapeutic agents, but also because such information
may be important in identifying new sources of
substances of economic value such as tannins, oils,
gums, and precursors for the synthesis of complex
chemical substances. In addition, the knowledge of the
chemical constituents of plants would further be
valuable in discovering the actual value of folkloric
remedies (Mojab et al, 2003).
This study was therefore undertaken to determine the
antibacterial properties of hexane, ethyl acetate and
dichloromethane root extracts of I. lupatana Baker F.