Medicinal Plants Classification Biosynthesis and ... - Index of

Biomolecules with Anti-Mycobacterial Activity
of highly drug-resistant TB threaten to make TB into an untreatable and highly fatal disease,
particularly in resource-poor countries with a high prevalence of AIDS [Chan et al, 2008].
No new classes of specific drugs for TB have been developed in the past 30 years and the
global number of TB cases is still increasing. Therefore there is an urgent need to develop
faster acting and effective new anti-tubercular agents in order to control this infection. In this
chapter we will describe some compounds found in plants that have been analyzed in
different bioassays and showed anti-mycobacterial activity.
Anti-TB Compounds Derived from Plants
Traditional medicine, particularly the use of plants or their extracts, has been the most
important source for the screening and isolation of natural products with anti-mycobacterial
activity. Use of traditional medicine for treatment of respiratory diseases, including
tuberculosis, has been a source for many potential opportunities to find new anti-TB drugs.
Several groups around the world have analyzed plants used by people as herbal medicines,
looking for biological activities against infections and other illness. To date, only a few
compounds with significant anti-mycobacterial activity have been isolated, and most of these
compounds are in the phase of in vitro laboratory or animal models testing.
Kolodziej et al [2003] reported the antibacterial activity of Pelargonium sidoides, plant
species used in folk medicine by the Southern African native population. P sidoides extracts
contained oxygenated coumarins and simple phenol gallic acids [Kayser et al, 1997]. Another
medicinal plant from southern Africa used to treat chronic infections is Carpobrotus sp that
by bio-autography, together with thin layer chromatography (TLC) analyses showed antibacterial
activity [Springfield et al, 2003]. Bamuamba et al [2008] analyzed five African
plant species for anti-mycobacterial activity. They found that extracts of Buddleja saligna
and Leysera gnaphalodes exhibited significant anti-mycobacterial activity, primarily
associated with the presence of non-cytotoxic triterpenoids oleanolic acid in B. saligna and
both oleanolic and ursolic acids in L. gnaphaloides. In fact, there are many plants used
against TB in African traditional medicine. McGaw et al [2008] summarize the available
knowledge on South African plants used to treat TB symptoms, and anti-mycobacterial
efficacy of plant-derived extracts and compounds.
The activity of cryptolepine hydrochloride, a salt of the main indoloquinoline alkaloid
from the West African medicinal plant Cryptolepis sanguinolenta, was assessed against the
fast growing mycobacterial species M. fortuitum, M. phlei, M. aurum, M. smegmatis, M.
bovis BCG and M. abcessus and the MICs ranged over 2-32 µg/mL [Gibbons et al, 2003].
Ethiopian medicinal plants used to treat various infectious diseases were assessed for
their possible activity against TB in vitro. The authors studied fifteen crude extracts prepared
from seven plants. Only the acetone fraction obtained from the stem bark of Combretum
molle showed inhibitory activity at 100 µg/ml. Phytochemical analysis of the bioactive
fraction led to the isolation of two major tannins identified as ellagitannin and punicalagin.
The last compund was found to inhibit totally the growth of M. tuberculosis (ATCC 27294)
and a clinical isolate fully sensitive to the standard antituberculosis drugs [Asres et al, 2001].
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