Agriculture Reference
In-Depth Information
herbal Products for treatment of hIV/aIDS
Inhibitors of HIV Reverse Transcriptase (RT)
Medicinal plants have been used for the treatment of AIDS without any scientific evidence in
traditional systems of medicine. Modern isolation and bioassay techniques have made it possible to
demonstrate the activities of such herbal remedies in the laboratory against various sexually trans-
mitted pathogens, and in some cases elucidate their mechanism of action. Many natural products
have been shown to possess significant activity, at least
in vitro
studies, at concentrations that are
comparable to the synthetic RTs.
9,10
The compounds vary enormously in their chemical structures,
they include alkaloids, flavonoids, lignans, coumarines, naphthoquinones, antraquinones, polysac-
charides and terpenes. The most important examples include the novel naphthoquinones michel-
lamines A-C isolated from the rare tropical plant
Ancistrocladus korupensis
found Cameroon,
calanolide A, isolated from
Calophyllum lanigerum
, betulinic acid from
Syzigium claviflorum,
, the
dibenzylbutadiene lignans from
Anogeissus acuminata
, the sulfated polysaccharides found in many
sea weeds and putranjivain A from the Egyptian plant
Embelica officinalis
(
Phyllanthus embelica
).
Since these medicinal plants are locally available, they offer a ready alternatives to the expensive
and often inaccessible pharmaceutical RT drugs. Also, the plants are often less prone to the emer-
gence of drug resistance.
11
Other Antiviral and Immuno-Modulatory Agents
The use of highly active anti-retroviral therapy (HAART) has made a remarkable impact in the
management of HIV infections as evidenced by resolution of opportunistic infections and malig-
nancies, as well as declining hospitalization and mortality rates. This suggests that potent and sus-
tained suppression of viral replication, at least to some extent, is associated with reconstitution of
the immune system even in adult patients treated at advanced stages of the disease. The combination
of HAART with immune system enhancers, holds a lot of promise in the treatment of AIDS. The
exact mode of action of several plant-derived antiviral agents has not yet been determined but some
of them have been shown to exhibit significant activity against HIV, a virus associated with AIDS.
The plants in this category contain compounds that either interfere directly in various stages in
the replication cycle of HIV or strengthen the patients' immune system against the devastating effect
of the infection. The list includes substances that exhibit the following inhibitory activities against
HIV: protease inhibition, virus adsorption, glycosylation, virus-cell fusion, assembly/ release, trans-
lation, integration, etc. Some of the active compounds from these plants are well known and have
been studied under clinical setting, include castonospermine, glycyrrhizin, papaverine, trichosan-
thin, aceramannan, and N-butyl-1-deoxynojirimicin.
Most of the plants used in the traditional treatment of AIDS are used in poly-herbal formula-
tions. A typical example is the combination of a mixture of
Astragalus membraceous, Tinospora
cordifolia, Glycyrrhiza glabra, Aloe barbadensis, Andrographis paniculata, Garcinia kola,
and
Moringa oleifera
leaf extract. The mixture, like most plant extracts, may be capable of non-specific
stimulation of the immunological defense mechanisms. Although there is no large clinical outcome
studies or any report of double-blind placebo controlled evaluation of the this poly-herbal prod-
uct, the wide use of this mixture suggests that it must possess some beneficial effect. It has been
observed that such non-specific stimulants do not affect immunological memory cells and since
their pharmacological efficacy fades comparatively quickly, they have to be administered either at
intervals or continuously.
12
The product, like similar dietary supplements, may be used as an adju-
vant with existing antiviral medication, with the approval of the attending physician. A similar for-
mulation known as IM-133, which consists of a mixture of
Tinospora cordifolia
(stems, 40%, w/w),
