Post on 10-May-2020
1.1. Assam and present scope of study:
1.2. Antioxidant
1.3. Antimicrobial
1.4 Phytochemistry
References
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1. Introduction
1.1. Assam and present scope of study:
The North-Eastern India is constituted by eight states (Assam, Arunachal Pradesh,
Manipur, Meghalaya, Mizoram, Nagaland, Tripura and Sikkim) and seven states excluding
seven sisters
sq km, which is 25% of the tota
geographical area supporting 50% of the flora (8000 species), of which 31.58% (2526
species) is endemic (Yumnam 2008) and forms a significant portion of both the Himalaya
and Indo-Burma biodiversity hotspots. North-East India has a relatively complex geography
(e.g. altitude ranging from 100 to > 7000 m above sea level) and habitat diversity from
tropical to alpine (Pawar et al., 2007). The region is also the abode of approximately 225
tribes, out of 450 in India (Chatterjee et al., 2011).
Assam consists of Karbi Anglong & north cachar as hilly terrain of varying altitude and
Brahmaputra & Barak Valley plains. In Assam, there are as many as 23 tribal communities,
which constitute 12.82 per cent of the total population of the state (Ali et al., 2003). About
80% population of Assam reside in remote areas, and is totally dependent on plants for their
day-to-day life (Singh et al., 2011). These tribes have their unique knowledge of medicinal
plants to combat various diseases. Availability of diverse medicinal plants and their
knowledge of use make Assam an important study area.
Human learnt the use of herbs as medicines and for other purposes since time
immemorial. But, the depth was unknown till science tried to explore the underlying
phenomena. Early human was acquainted with the value of the herbs, but the modern science
unfurled the complex envelop and showed the humanity, the actual agent.
The discovery of novel drugs from nature is also important because many isolated
molecules are quite complex and would not be obtained by a simple synthetic approach. In
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some cases, the isolated lead compounds may not be potent enough to be drugs in their own
right, but they can serve as pharmacophores for chemical modification and drug design.
Ethno botany provides the tentative feasible path to move forward the avenue of modern drug
discovery. Moreover, since the isolation of active compound is guided by ethnobotany i.e. the
plant source has been in use by human for long time, there is less probability for the
compound to be toxic. Assam has diverse ethnic group and hence a diversity of knowledge,
particularly the use of different plants. From the information provided by ethnobotany,
phytochemistry can make a sure shot and can lead a pathway within its possibility to utilise
the natural resources to its best for the mankind. Therefore, there is a growing interest mostly
in plant derived compounds particularly from the ethnomedicinal plants and their potential
use in food and pharmaceutical industries.
Search of antioxidant and antimicrobial is highly demaded in the present day situation.
Antioxidant phytochemical has gained enough thrust due to free radical imbalance in the
metabolic system due to different endogenous and exogenous factors appeared, leading to the
generation of disease and disease complexity. For example, physical stress results in the
generation of free radicals in the body, therefore, Indian soldiers to whom physical stress is a
routine matter and reaches its peak during operations are more likely to undergo oxidative
stress. This hinders the competence of the Indian defence forces. While, antimicrobial
phytochemicals are need of the hour, due to the emergence of drug resistance and to find a
less toxic and effective antimicrobial substitute. In both the case phytochemical study is
necessary not only to uncover a novel compound but also to standardise and monitor herbal
formulation in use, to maintain quality control. Therefore, the present study was undertaken.
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1.2: Antioxidant
concentrations compared to that of an oxidisable substrate, significantly delays or inhibits the
et al., 1995).
Pokorny J. (2007) described types of antioxidants as follows:
1. Inhibitors of free-radical oxidation reactions called preventive antioxidants,
which inhibit the formation of free lipid radicals (Fig. 1A); the most important
substances of the type are compounds inhibiting the decomposition of lipid
hydroperoxides into free radicals (Fig. 1B), as this is the most frequent source
of free radicals in the period of initiation.
2. Inhibitors interrupting the propagation of the autoxidation chain reaction (the
proper antioxidants) are called chain-breaking antioxidants (Fig. 1C).
3. Singlet oxygen quenchers (e.g. carotenes, especially lycopene).
4. Synergists of proper antioxidants, i.e. substances not efficient as antioxidants
when applied alone, but increasing the activity of chain-breaking antioxidants
in a mixture; citric acid is the best-known example.
5. Reducing agents, such as thiols or sulfides (thioethers), which convert
hydroperoxides into stable components in a non-radical way.
6. Metal chelators, which convert metal pro-oxidants, especially iron or copper
derivatives, into stable products. If not chelated, heavy metals promote the
decomposition of lipid hydroperoxides into free radicals (Fig. 1B). Quercetin,
tannins, and phytates are good examples of efficient metal chelators.
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7. Inhibition of pro-oxidative enzymes (especially lipoxygenases).
R-H R + H [1A]
ROOH RO + OH [1B]
R + O2 RO2
RO2 + RH RO2H + H [1C]
R , RO , RO2 stable products
Figure 1.1: Mechanism of lipid oxidation
In recent years, a substantial body of evidence has developed supporting a key role for
free radicals in many fundamental cellular reactions and suggesting that oxidative stress
might be important in the pathophysiology of common diseases including atherosclerosis,
chronic renal failure, and diabetes mellitus. Reactive oxygen species (ROS) includes
superoxide radicals, hydroxyl radicals, and hydrogen peroxide, are often generated as
byproducts of biological reactions. They are known to cause oxidative damage to living
systems, they may also cause great damage to cell membranes and DNA, inducing oxidation
that causes membrane lipid peroxidation, decreased membrane fluidity, and DNA mutations
leading to cancer, atherosclerosis, hypertension and arthritis, cirrhosis, diabetes, heart disease,
inflammatory conditions and other diseases. (Cerutti 1991; Frenkel 1992; Harman 2006;
Dreher et al., 1996; Diaz et al., 1997; Hecht 1999; Finkel et al., 2000), and neuronal
Christen 2000) Lang et al.,
1998) as well as being involved in the process of aging (Ames et al., 1993; Ashok et al.,
1999). In a review, Young (2001) described mechanisms of free radical formation in the
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body, the consequences of free radical induced tissue damage, and the function of antioxidant
defence systems in health and disease.
Halliwell B winner of Lifetime Achievement Award, 2008 from the Society for Free
Radical Biology and Medicine (SFRBM)) mentioned in a review (2009) that, antioxidants
seem, in general, better at decreasing oxidative damage in rodent models of disease, and
simultaneously beneficially affecting the disease progression. He exemplified two research
work where it has been shown that antioxidants are beneficial in murine models of
amyotrophic lateral sclerosis, but do not seem to help human patients. He concluded with that
antioxidants could be beneficial, if we could find ones that actually work in humans, getting
to the correct sites of action and diminishing oxidative damage at those sites.
Plant-derived antioxidants are capable to delay or prevent the onset of degenerative
diseases because of their redox properties (Govindarajan et al., 2005.). Considerable attention
towards them as potentially protective factors against cancer and heart diseases is due to their
antioxidant potency and availability in a wide range of commonly consumed foods of plant
origin (Kamei et al., 1995; Rice-Evans 2001; Muselik et al., 2007).
Polyphenolic compounds exhibit profound antioxidant properties. This type of compounds is
commonly found in both edible and inedible plants, and they have been reported to have
multiple biological effects, including antioxidant activity. Wojdylo (2007) described that
crude extracts of herbs and spices, and other plant materials rich in phenolics are of
increasing interest in the food industry because they retard oxidative degradation of lipids and
thereby improve the quality and nutritional value of food.
Flavonoids are another important class of antioxidant compounds. The basic flavonoids
structure is the flavan nucleus, which consists of 15 carbon atoms arranged in three rings. The
differences in the structure and substitution influence the phenoxyl radical stability and
thereby the antioxidant properties of the flavonoids.
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Few examples from various types of flavonoids are presented below:
1. Chemical structure of flavonols (quercetin, kaempferol, myricetin, isorhamnetin)
O
OH
HO
OH
R1
OH
R2
O
2. Chemical structure of flavones (luteolin, apigenin)
O
OH
HO
OH
R1
O
3. Chemical structure of flavanones (eriodictyol, hesperetin, naringenin)
O
OH
HO
R2
O
R1
4. Structure of flavan-3-ols (catechins, epicatechins, theaflavins, and thearubigins)
O
OH
HO
OH
OH
OH
R
Flavonol R1 R2
Quercetin OH H
Kaempferol H H
Myricetin OH OH
Isorhamnetin OMe H
Flavone R1
Apigenin H
Luteolin OH
Flavonone R1 R2
Eriodictyol OH OH
Hesperetin OH OMe
Naringenin H OH
Catechins R
(+)-Catechin H
(+)-Gallocatechin OH
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O
OH
HO
OH
OH
OR2
R1
OH
OH
OH
O
Gallate
Epicatechins R1 R2
(-)-Epicatechin (EC) H H
(-)-Epigallocatechin (EGC) OH H
(-)-Epicatechin-3-gallate (ECG) H Gallate
(-)-Epigallocatechin-3-gallate (EGCG) OH Gallate
5. Chemical structure of anthocyanidins (cyanidin, delphinidin, malvidin, pelargonidin,
peonidin, and petunidin)
O
OH
HO
OH
R1
OH
R2
Moyer et al., (2002) analyzed fruits from 107 genotypes of Vaccinium L., Rubus L., and
Ribes L., for total anthocyanins, total phenolics and antioxidant capacities as determined by
ORAC and FRAP. They demonstrated the wide diversity of phytochemical levels and
antioxidant capacities within and across these three genera of small fruit.
Anthocyanidin R1 R2
Cyanidin OH H
Delphinidin OH OH
Malvidin OMe OMe
Pelargonidin H H
Petunidin OMe OH
Peonidin OMe H
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Ou et al., (2002) studied a total of 927 freeze-dried vegetable samples, including 111
white cabbages, 59 carrots, 51 snap beans, 57 cauliflower, 33 white onions, 48 purple onions,
130 broccoli, 169 tomatoes, 25 beets, 88 peas, 88 spinach, 18 red peppers, and 50 green
peppers, were analyzed using the ORAC and FRAP methods. The data show that the ORAC
and FRAP values of vegetable are not only dependent on species, but also highly dependent
on geographical origin and harvest time.
The above points clearly indicate the importance of research on antioxidant
phytochemicals to cope with the imbalance between free radical generation and self-defence
system of the body.
1.3 Antimicrobial:
Microbial diseases are ubiquitous throughout the tropical and subtropical regions of the
world. They are of serious health concern, not only because they are life-threatening but also
due to the extreme discomfort, stress, pain and ugliness they cause. The incidence of such
infections rises alarmingly as reported from various parts of India as well as other countries
(Jain et al., 2008; Kannan et al., 2006; Nweze, 2010; Prasad et al., 2005; Straten et al., 2003).
The hot and humid climate of Assam is highly conducive for the growth of many pathogenic
microorganisms. Investigations on the occurrence of microbial diseases in some parts of
Northeast India revealed the prevalence of different types of pathogenic microbes, like
dermatophytes, yeasts and bacteria (Das, 2003; Devi and Zamzachin, 2006; Jaiswal, 2002;
Sharma and Borthakur, 2007). It is a serious health problem of the common people,
particularly those residing in rural area. The Indian soldiers working in hostile environment in
remote border areas, particularly during operations are more prone to such ailments,
hampering the efficiency of the defence forces.
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Many of the synthetic drugs presently used in treatment of microbial diseases have
undesirable side effect, are ineffective against new or re-emerging microbes, or lead to the
rapid development of resistance. Increase incidence of microbial diseases and resistance to
microbial agents has important implications for morbidity, mortality and health care costs all
over the world. These adverse effects together with the emergence of multidrug-resistant
strains of various pathogenic microbes call attention to the need of development of new
generation of antimicrobial agents. Substantial attention has been focussed on developing
novel and effective antimicrobial options for the treatment of infections and to prevent the
emergence and spread of newly emerged microorganisms.
In this context, ethnopharmacolgy hold a paramount importance, to cope with various
ailments using natural resources from the traditional knowledge. Medicinal plants constitute
an excellent source of new drugs, mainly considering that the molecular diversity of plant
resources is much higher than that derived from chemical syntheses. Traditionally used
medicinal plants produce a variety of compounds of known therapeutic properties. This fact
has stimulated investigation of the antimicrobial activity of different plant extracts, fraction
and compounds in order to promote the development of new pharmaceuticals that can control
many diseases including microbial diseases. As a consequence, many research groups have
concentrated efforts on the assessment of the antimicrobial properties of plant based products,
aiming to detect new antimicrobial compounds. In recent years, antimicrobial properties of
medicinal plants are increasingly reported different parts of the country as well as overseas.
It is a well-known fact that one of the most famous natural product discoveries is that of
penicillin derived from a fungus (microorganism) Penicillium notatum discovered by A.
Fleming in 1929. A counter current extractive separation technique that produced penicillin
in high yields was required for the in vivo experimentation that ultimately saved countless
lives and won Chain and Florey (together with Fleming) the 1945 Nobel Prize in Physiology
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and Medicine. This discovery led to the re-isolation and clinical studies by Chain, Florey and
co-workers in the early 1940s and commercialization of synthetic penicillin, which ultimately
revolutionized drug discovery research.
After publication of the first clinical data on penicillin G in between 1942 1944 there
was a worldwide endeavour to discover new antibiotics from microorganisms and bioactive
natural products. During the 1970s, advancedment in screening methods, the production of
bacterial strains supersensitive to -lactams, tests for the inhibition of -lactamases and
specificity for sulphur containing metabolites resulted in the discovery of novel antibiotic
structural classes (norcardicins, carbapenems and monobactams) including the isolation of
the antibiotics, norcardicin, imipenem and aztreonam, respectively (Dias et al., 2012).
NO N
S
O OH
H
O
OH2N
CO2HN
H
NO
O
NOH
H
OH
CO2H
H
Penicillin Norcardicin
N
OHH
COOH
SNH
NH
O
H
N
CH3
O SO3H
NH
O
NO
NS
H2N
O
HO
Imipenem Aztreonam
The use of plants as medicines involves isolation of active compounds. This began with
the isolation of morphine from opium in the early 19th century (Huxtable and Schwarz,
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2001). Of the several hundred thousand plant species around the globe, only a small
proportion has so far been investigated from phytochemical and pharmacological point of
view. The ultimate success of an investigation leading to discovery of bioactive compounds
depends on selection of appropriate plant material, suitable biological assays and chemical
screening methods. Biological and chemical screenings are complementary approaches for
the rapid detection and isolation of interesting new bioactive plant compounds. Bioassay-
guided fractionation has been used successfully for the discovery of many bioactive
compounds like antifungal, antibacterial etc (Hostettmann, 1999). Various chromatographic,
spectroscopic and chemical methods were employed for monitoring the fractionation,
isolation and identification of bioactive components.
The majority of natural products derived from medicinal plants are secondary
metabolites viz., terpenoids, steroids, cardenolides, quinine lignans, flavonoids or alkaloids.
The active molecules isolated from traditional medicinal plants might provide valuable drugs.
Many active compounds from traditional medicine sources could serve as good scaffolds for
rational drug design. Challenges in bioassay screening and identification of active
components remain an important issue in the future of drug discovery from medicinal plants.
The emergence of resistant strains due to unjustified use of drug is another serious problem.
Hence, there is an urgent need for the development of new antimicrobial drugs, which can
take care of disease, efficacy and cost.
1.4 Phytochemistry
Since the dawn of medicine, compounds derived from animals, plants, and microbes
have been used as therapeutic agents. Carlson E. E. (2010) Indicated that, although about
200,000 natural compounds are currently known but prior to the 1800s, the active
constituents of most medicines, which were generally plant-based, were unknown. Isolation
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of the well-known drug, morphine, from the opium poppy occurred in 1817. Although the
therapeutic value of natural products is clear, use of these compounds presents a number of
nd it
has become clear that renewed interest in natural products will be essential to the future of
both biological studies and drug development.
The biosynthesis and breakdown of proteins, fats, nucleic acids and carbohydrates,
which are essential to all living organisms, is known as primary metabolism with the
. Secondary
metabolites are generally not essential for the growth, development or reproduction of an
organism and are produced either as a result of the organism adapting to its surrounding
environment or are produced to act as a possible defence mechanism against predators to
assist in the survival of the organism. (Dias et al., 2012 and Croteau et al., 2000).
Traditional medicinal practices have formed the basis of most of the early medicines
followed by subsequent clinical, pharmacological and chemical studies. Few early examples
noted by Dias et al., (2012) are synthesis of the anti-inflammatory agent, acetylsalicyclic acid
(aspirin) derived from the natural product, salicin isolated from the bark of the willow tree
Salix alba L. Investigation of Papaver somniferum L. (opium poppy) resulted in the isolation
of several alkaloids including morphine, a commercially important drug, first reported in
1803. Digitalis purpurea L. (foxglove) had been traced back to Europe in the 10th century
but it was not until the 1700s that the active constituent digitoxin, was found to enhance
cardiac conduction. The anti-malarial drug quinine was isolated from the bark of Cinchona
succirubra Pav. Ex Klotsch, used for centuries for the treatment of malaria, fever,
indigestion, mouth and throat diseases and cancer.
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O
HOO
OCH3
O
OHHO
HO
O
OH
HO HO
O
HO
NCH3
H
1 2 3
O O
O O
O O
O
O
OH
HO
H
OH
H H
H
OH
H
OH
H
N
HONH
H3CO
4 5
Acetylsalicyclic acid (1), Salicin (2), Morphine (3), Digitoxin (4), Quinine (5)
The most widely used breast cancer drug is paclitaxel (Taxol), isolated from the bark of
Taxus brevifolia (Pacific Yew). In 1962 the United States Department of Agriculture (USDA)
first collected the bark as part of their exploratory plant screening program at the National
Cancer Institute NCI). The bark from about three mature 100 year old trees is required to
provide 1 gram of Taxol, given that a course of treatment may need 2 grams of the drug.
Current demand for Taxol is in the region of 100 200 kg per annum (i.e., 50,000 treatments
per year) and is now produced synthetically. Taxol is present in limited quantities from
natural sources, its synthesis (though challenging and expensive) has been achieved. Baccatin
III present in much higher quantities and readily available from the needles of T. brevifolia
and associated derivatives is an example of a structural analogue that can be efficiently
transformed into Taxol.
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OH
OOH
O
OO O
H
O
O
O
OH
NHO
O
O
OH
OOH
O
HOO O
H
O
O
O
O
Taxol Baccatin
A plant based antimalarial drug isolated from the Chinese plant Artemisia annua
(Asteracae) was used. (Klayman 1985) However, the use of Artemisinin, an endoperoxide
sesquiterpene lactone is somewhat limited because of its relatively high cost , limited
production to GMP standards and reports of toxicity. Derivatives of Artemisinin such as
artemether, arteether, artesunate, and dihydroartemisinin are prepared semi-synthetically
from purified extract of Artemisia annua. (Haynes, 2001).
O
O O
H
H
O
O
O
O O
H
H
O
OCH2CH3
Artemisinin Arteether
Grandisines A and B are two indole alkaloids which were isolated from the leaves of
the Australian rainforest tree, Elaeocarpus grandis (Figure/////). Grandisine A contains a
unique tetracyclic skeleton, while Grandisine B possesses an unusual combination of
isoquinuclidinone and indolizidine ring systems. Both Grandisines A and B are potential
leads for analgesic agents. Galantamine hydrobromide is an Amaryllidaceae alkaloid
obtained from the plant Galanthus nivalis and has been used traditionally in Turkey and
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Apomorphine is a derivative of morphine isolated from the poppy (P. somniferum) and is
. Tubocaurarine isolated from the climbing plant,
Chondrodendron tomentosum (Menispermaceae) is one of the active constituents used as a
muscle relaxant in surgical operations, reducing the need for deep anesthesia. The limited
availability of tubocurarine has led to the development of a series of synthetic analogues
which are now preferred over the natural product.
O
O
NH
H
H
O
N
N
O
1 2
N
HO
HO H
3
NO
HCH3
H
H3CO
OH
O
Me2NOH
OCH3
H
4
Grandisine A (1), Grandisine B (2), apomorphine (3) and tubocaurarine (4).
Written records of the use of plants as medicinal agents date back thousands of years. Ancient
system of medicine like Sidhdha and Unani are based on the use of plants. The oldest records
come from Mesopotamia and date from about 2600 BC. However, it was not until the early
that among the first active principles to be isolated were strychnine, morphine, atropine, and
colchicine. In 1826, this resulted in E. Merck producing the first commercially pure natural
product, morphine.
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O
O
CH2OH
MeN
O
OMe
OMe
MeO
MeO
H
NH
O
Atropine Colchicine
N
N
O
H
H
HH
O
H
O
HO
NMeH H
HO
Strychnine Morphine
Phillipson (2001) mentioned that 6 out of the top 20 pharmaceutical prescription drugs
dispensed in 1996 were natural products and that over 50% of the top 20 drugs could be
linked to natural product research. In recent years, the development of sensitive biological
testing systems, mainly by industry, has led to the procedure of high throughput screening.
Such screens are carried out robotically and it is possible for a pharmaceutical or
biotechnological company to run 50,000 biological tests per day. The isolation and use of
natural products such as digitoxin, morphine and quinine has resulted in replacing the plant
extracts used with single chemical entities. There is a basic supposition that any plant
possessing clinical effectiveness must contain an active principle that can completely replace
the plant extract, however Phillipson (2001) pointed out that this may not necessarily be true.
The use of plants as medicines has involved the isolation of active compounds, beginning
with the isolation of morphine from opium in the early 19th century (Kinghorn A. D. 2001)
and subsequently led to the isolation of early drugs such as cocaine, codeine, digitoxin and
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quinine, of which some are still in use (Butler M. S. 2004, Newman et al., 2000). Isolation
and characterization of pharmacologically active compounds from medicinal plants continue
today. More recently, drug discovery techniques have been applied to the standardization of
herbal medicines, to elucidate analytical marker compounds.
According to the opinion of Newman et al., (2003), 61% of the 877 small-molecule
(New Chemical Entities) introduced as drugs worldwide during 1981 2002 was inspired by
natural products. These include, natural products (6%), natural products derivatives (27%),
synthetic compounds with natural products-derived pharmacophore (5%) and synthetic
compounds designed from natural products (natural products mimic, 23%).
Keeping a view of the above facts, the present study makes an effort towards search of
antioxidant and antimicrobial compound, with the following objectives:
1. Evaluation of antioxidant and antimicrobial activity of certain medicinal plants of
Assam.
2. Bioassay guided fractionation to find active components.
3. Isolation and identification of the active compound(s).
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References:
Ali A.N.M. I., Das I. (2003). Tribal situation in North East India. Stud. Tribes Tribals. 1(2):
141-8.
Ames B. N., Shigenaga M. K., Hagen T. M. (1993). Oxidants, antioxidants, and the
degenerative diseases of aging. Proc. Natl. Acad. Sci. U.S.A. 90: 7915-22.
Ashok B. T., Ali R. (1999). The aging paradox: free radical theory of aging. Exp. Gerontol.
34; 293 303.
Butler M. S. (2004). The role of natural product chemistry in drug discovery. J. Nat. Prod.,
67: 2141 53.
Carlson E. E. (2010). Natural Products as Chemical Probes, ACS Chem Biol. 5(7): 639-53.
Cerutti A. (1991) Oxidant stress and carcinogenesis. Eur. J. Clin. Inves. 21: 1-11.
Chatterjee S., Dhar S., Sengupta B., Sengupta S., Mazumder L., Chakarabarti S. (2011).
Coexistence of Haemoglobinopathies and Iron Deficiency in the Development of
Anemias in the Tribal Population Eastern India. Stud Tribes Tribals. 9(2): 111-21.
-
9S.
Croteau R., Kutchan T. M., Lewis N. G. (2000). Natural Products (Secondary Metabolites) in
Biochemistry & Molecular Biology of Plants, B. Buchanan, W. Gruissem, R. Jones, Eds.
American Society of Plant Physiologists. Ch 24: 1250-318.
Das K. K. (2003). Pattern of dermatological diseases in Gauhati Medical College and Hospital
Guwahati. Indian J. of Dermatology, Venereology, Leprology. 69 (1): 16-8.
Devi T. B., Zamzachin G. (2006). Pattern of skin diseases in Imphal. Indian J. of
Dermatology. 51: 149-50.
Dias D. A., Urban S. and Roessner U. (2012). A Historical Overview of Natural Products in
Drug Discovery. Metabolites. 2: 303-36
19
Diaz M. N., Frei B., Keaney Jr. J. F. (1997). Antioxidants and atherosclerotic heart disease,
New Engl. J. Med. 337: 408-16.
Dreher D., Junod A. F. (1996). Role of oxygen free radicals in cancer development. European
J. Cancer. 32A: 30 8.
Finkel T., Holbrook N. J. (2000). Oxidative stress and biology of ageing. Nature. 408: 239-
47.
Frenkel K. (1992). Carcinogen-mediated oxidant formation and DNA damage. Pharmacol.
Ther. 53: 127 66.
Govindarajan R., Vijayakumar M., Pushpangadan P. (2005) Antioxidant approach to disease
Journal of
Ethnopharmacology. 99: 165 78.
Halliwell B. (2009). The wanderings of a free radical. Free Radic. Biol. Med. 46: 531 42.
Halliwell B., Gutteridge J. C. (1995). The definition and measurement of antioxidants in
biological systems. Free Radic. Biol. Med. 18:125 6.
Harman D. (2006). Free radical theory of aging: An Update; Increasing the Functional Life
Span. Annals of the New York Academy of Sciences. 1067: 10-21.
Haynes R. K. (2001). Artemisinin and its derivatives: the future for malaria treatment. Curr.
Opin. Infect. Dis. 14: 719-726.
Hecht S. S. (1999). Tobacco smoke carcinogens and lung cancer. J. Natl. Cancer. Inst. 91:
1194 210.
Jain N., Sharma M. (2003). Broad spectrum antimycotic drug for the treatment of ringworm
infection in human beings. Current Science. 85 (1): 30-4.
Jain N., Sharma M., Saxena V. N. (2008).Clinico-mycological profile of dermatophytosis in
Jaipur, Rajasthan. Indian J.l of Dermatology, Venereology, Leprology. 74 (3): 274-5.
20
Jaiswal A.K. (2002). Ecologic perspective of dermatologic problems in North Eastern India,
Indian Journal of Dermatology, Venereology, Leprology. 68: 206-7.
Kamei H., Kojima T., Hasegawa M., Koide T., Umeda T., Yukawa T., Terabe K. 1995.
Flavonoid mediated tumor growth suppression demonstrated by in vivo study. Cancer
Invest. 13: 590-4.
Kannan P., Janaki C., Selvi G.S. (2006). Prevalence of dermatophytes and other fungal agents
isolated from clinical samples. Indian J. of Medical Microbiology. 24 (3): 212-5.
Kinghorn A. D. (2001). Pharmacognosy in the 21st century. J. Pharm. Pharmacol. 53: 135 48.
Klayman,D.L. (1985). Quinghaosu (artemisinin): An antimalarial drug from china. Science.
228: 1049-55.
Lang A. E., Lozano A. M. (1998).
339: 111-4.
Moyer R. A., Hummer K. E., Finn C. E., Frei B., and Wrolstad R. E. (2002). Anthocyanins,
Phenolics, and Antioxidant Capacity in Diverse Small Fruits: Vaccinium, Rubus, and
Ribes. J. Agric. Food Chem. 50: 519-25.
Muselik J., Garcia-Alonso M., Martin-Lopez M.P., Zelmicka M., Rivas-Gonzalo J. C. (2007).
Measurement of Antioxidant Activity of Wine Catechins, Procyanidins, Antocyanins and
Piranoantocyanins. Int. J. Mol. Sci. 8: 797-809.
Newman D. J., Cragg G. M. and Snader K. M. (2000). The influence of natural products upon
drug discovery. Nat. Prod. Rep. 17: 215 34.
Newman D. J., Cragg G. M. and Snader K. M. (2003). Natural products as sources of new
drugs over the period 1981 2002. J. Nat. Prod. 66: 1022 37.
Nweze E. I. (2010). Dermatophytosis in Western Africa: A review. Pakistan J. of Biological
Sciences. 13 (13): 649-56.
21
Ou B, Huang D, Hampsch-Woodill M, Flanagan J. A., Deemer E. K. (2002). Analysis of
Antioxidant Activities of Common Vegetables Employing Oxygen Radical Absorbance
Capacity (ORAC) and Ferric Reducing Antioxidant Power (FRAP) Assays: A
Comparative Study. J. Agric. Food Chem. 50, 3122-8.
Pawar S., Koo M. S., Kelley C., Ahmed M. F., Chaudhuri S., Sarkar S. (2007). Conservation
assessment and prioritization of areas in Northeast India: Priorities for amphibians and
reptiles. Biological conservation. 136: 346-61.
Phillipson J. D. (2001). Phytochemistry and medicinal plants. Phytochemistry. 56: 237-43.
Pokorny J. (2007). Are natural antioxidants better and safer than synthetic antioxidants? Eur.
J. Lipid Sci. Technol. 109: 629 42.
Prasad P.V.S., Priya K., Kaviarasan P.K., Aanandhi C., Lakshmi S. (2005). A study of
chronic dermatophyte infection in a rural hospital. Indian J. of Dermatology,
Venereology and Leprology. 71 (2): 129-30.
Rice-Evans C. (2001). Flavonoids antioxidants. Curr. Med. Chem. 8: 797-807.
Sharma S., Borthakur A. K. (2007). A clinico-epidemiological study of dermatophytoses in
Northeast India. Indian J. of Dermatology, Venereology, Leprology. 73 (6): 427-8.
Singh V. K., Chanu L. I., Chiru community, Baruah M. K. (2011). An ethnobotanical study of
Chirus A less known tribe of Assam. Indian journal of traditional knowledge. 10(3):
572-4.
Straten M. R. V., Hossain M. A., Ghannoum M. A. (2003). Cutaneous infections
dermatophytosis, onychomycosis and tinea versicolor. Infectious Disease Clinics of
North America. 17: 87 112.
Weitzman I., Summerbell R. C. (1995). The Dermatophytes. Clinical Microbiology Reviews.
8 (2): 240 59.
22
Wojdylo A., Oszmianski J., Czemerys R. (2007). Antioxidant activity and phenolic
compounds in 32 selected herbs. Food Chemistry. 105: 940-9
Young I. S. (2001). Antioxidants in health and disease. J. Clin. Pathol. 54: 176-86.
Yumnam J.Y. (2008). Rich biodiversity of Northeast India needs conservation, Current
Science, 95 (3): 297.