Plant Medicines in Cancer Treatment

ready Medicines in Cancer TreatmentReview of Lite fundamenturePlants as healing(p) agentsPlant medicines argon the nearly widely expenditu rosy medicines in the world today. The use of herbs and dos as the first medicine is a universal phenomenon. E truly floriculture on earth, through written or oral tradition, has relied on the extensive anatomy of natural chemistry set in healing nominates for their healing(p) properties (Serrentino 1991). Plants with therapeutic potential may be defined as whatever show that burn down be put to culinary or medicative use. young anticipa golf tees engraft that viands and their constituents coif in a expressive style similar to modern medicates without the dreaded side make (Serrentino 1991). Sometimes plant medicine is viewed as complementary medicine, working closely with allopathic drugs. or so 5.1 billion people worldwide employ natural plant- base remedies as their primeval medicines for both acute and degenerative wellness problems, from treating cat valium cold to coercive blood pressure and cholesterol (Stockwell, 1988).Most of the drugs were substances with a cut officular therapeutic bodily process infusioned from plants. Some medicines, such as the cancer drug Taxol from genus Taxus brevifolia and the anti-malarial quinine from Cinchona pubescens atomic number 18 manufactu inflamed from the plants. early(a) medicinal agents such as pseudoephedrine originally derived from ephedra species and methylsalicylate, derived from gaultheria procumbens atomic number 18 now synthesized. Plant medicines stay put indispensable to modern pharmacology and clinical practice. Much of the current drug discovery and development process ar plant-based, and new medicines derived from plants be inevitable. efficacious foodsA food can be regarded as a practicable food if it is demonstrated to affect one(a) or more designate functions in the body beyond adequate nutrition and improves health/ w elf be or reduces the risk of diseases (Tsao and Akhtar, 2005). On this basis, a functional food can be a natural food, a food to which a official fraction has been added, or from which a deleterious component has been removed or a food where the nature of one or more components has been modify (Tsao and Akhtar, 2005). While searching for new sources of functional food, attention has been paid to vegetables from the family Brassicaceae family, which more often used in the merciful diets. The cruciferous vegetables may thus become a potential source of a alimental food or food ingredients. Recent enquiry showed that cruciferous vegetables end an appropriate amount of bioactive compounds such as GLs, ITCs, tocopherols, L-ascorbic battery-acid, vitamin B, reduced glutathione, inositol phosphates and poly phenolic compounds Nakamura et al, 2001 Zielinski and Kozlowska, 2003 Zielinski et al, 2005 Takaya et al, 2003.Cruciferous plantsThe family mustard family (Brassicaceae) is an e conomically chief(prenominal)(prenominal) family with about 350 genera and 3000 species that includes some(prenominal)(prenominal)(prenominal) edible plants. Despite the neat diversity among the crucifers, members of only a few genera ar eaten. The close ordinarily eaten cruciferous vegetables belong to the genus Brassica that includes broccoli, cabbage, caulif subvert, kale and Brussels sprouts. Other cruciferous vegetables used in the human diet such as radish, water supply cress, wasabi, horseradish, garden cress, Italian cress, Swiss chard and crambe belong to another(prenominal) genera of the family such as Raphanus, Nasturtium, Wasabia, Armoracia, Lepidium, Eruca, Beta and Crambe respectively.Cruciferous vegetables ar weighty dietary constituents in many parts of the world and appear to t hematin for about 10 15% of total vegetable inspiration, reaching closely 25% in countries with a high consumption (Bosetti et al, 2002 Chiu et al, 2003). However, regional pro totype of crucifer consumption varies substantially in different parts of the world. The highest intake of cruciferous vegetable was inform to that of people in China, who consumed more than one hundred g per day, representing about one-fourth of their total vegetable intake (Chiu et al, 2003). Other Asians and some Middle Eastern populations in Japan, Singapore, Thailand and Kuwait as well abide a relatively high intake of cruciferous vegetables, ranging from 40 80 g per day (Bosetti et al, 2002 Seow et al, 2002 Shannon et al, 2002 Memon et al, 2002). However, the only study carried out in India (Rajkumar et al, 2003) showed a lower daily intake of cruciferous plants, of about 17 g per day. In North America, the daily estimated consumption was in the range of 16 40 g per day (Lin et al, 1998) and in South America, it was about 3 15 g per day (Atalah et al, 2001). The daily intake of cruciferous vegetables was account to be about 5 30 g per day in Europe (Bosetti et al, 200 2), 50 g per day in Australia (Nagle et al, 2003) and 15 g per day in South Africa (Steyn et al, 2003) respectively.Raphanus sativusR. sativus is believed to stimulate originated in southern Asia and was cultivated in Egypt. The first cultivated R. sativus was baleful variety and later on whitened and red R. sativus were developed. It was highly esteemed in antediluvian Greece, and the Greek physician Androcydes ordered his patients to eat R. sativus as a preservative against in deadlyation. The Nipponese white R. sativus, withal named daikon, is the vegetable for which the literature reports the highest per capita consumption, quoted at 55 g per day in Japan (Talalay and Fahey, 2001). In addition to this, Japanese alike consumes R. sativus sprouts under the name of Kaiware radish.Varieties of R. sativusThere are six main varieties of R. sativus such as Daikons, Red Globe, White Globe, Black, White Icicles and California mammoth WhiteDaikons (R. sativus L)This variety is primal to Asia. They are large and carrot-shaped, boast a white flesh that is juicy and a bit hotter than a red radish, but milder than dark-skinned.Red Globe (R. sativus var. red)This variety is the most popular in the United States. It is small, round or oval shaped, referred to as button red radishes and agree a solid crisp flesh.White Globe (R. sativus var.white)This variety is small and oval shaped, referred to as hailstone or white button. They have white flesh and milder than the red variety.Black (R. sativus var. niger)This variety is thought to be native to Egypt and Asia. They are turnip- measurementized in size and shape. They are quite pungent and siccative than other varieties of radishes.White Icicles (R. sativus L var. thin)This variety is long and tapered. They have a white flesh that is milder than the red variety.California Mammoth White (R. sativus L var. large)A larger variety than the white icicle, these varieties have oblong- shaped grow and their flesh i s slightly pungent.Nutritive value of R. sativusR. sativus paper and its leafy part are ideal vegetables as they provide an excellent source of vitamin C. fan-leaved part nabs almost six times the vitamin C cloy of its square up and alike a good source of calcium and iron. R. sativus is also a good source of potassium and folic acid. It is very low in fats. Approximately, carbon g of raw vegetable provides roughly 20 Kcal, coming by and large from carbohydrates (Table 2.1). Thus R. sativus is a dietary food that is relatively filling for its thermal value. Some sources list R. sativus as being flush in dietary fiber, whereas other sources differ in respect of its roughage content (USDA intellectual nourishment Database, 1999 Duke and Ayensu, 1985).Health benefits of R. sativus (Traditional usage of R. sativus)According to Hakeem Hashmi, an eminent Unani physician from India, R. sativus is unparallel in curing any kind of ailments. All the parts of R. sativus including its seed, stem, root and leaves are used in food and medicine. R. sativus is a unique vegetable having a hot and cold effect on the body simultaneously. R. sativus, like other members of the cruciferous family (cabbage, kale, broccoli, Brussels sprouts) contains cancer-protective properties.Liver and gall bladder disordersthroughout the history, R. sativus root and seeds have been trenchant when used as medicinal food for liver disorders. They contain sulfur-based compounds such as GLs and ITCs that increase the flow of bitterness and help to maintain healthy gallbladder and liver (Chevallier, 1996). They are useable in treating jaundice and also an excellent remedy for gall bladder stone.Kidney disordersR. sativus root, seeds and leaves are water pill in nature and increase the urine output. Their diuretic properties help to flush out the toxins accumulated in the kidneys and protect them from infections and instigative conditions. It is an old belief that R. sativus can aid in the treatment as well as prevention of kidney stones (Chopra et al, 1986).Respiratory disordersR. sativus is an anti-congestive and relieves congestion of the respiratory form. It has free-base to be beneficial in problems associated with bronchitis (Bown, 1995) and asthma (Duke and Ayensu, 1985).Skin disordersR. sativus helps to cure scrape disorders such as leucoderma, rashes, cracks, etc and also refreshes the skin by maintaining the moisture content of the skin (Duke and Ayensu, 1985).Digestive disordersR. sativus root, seeds and leaves are wealthy in roughage (indigestible carbohydrates) which facilitates digestion, go on water and relieve constipation (Chopra et al, 1986). They also soothe the digestive system and stimulate appetite (Chevallier, 1996)Nervous and vascular disordersR. sativus decreases nervous tensions and is also useful in enhancing blood circulation. It is a remedy for insomnia, hypochondria and irritative conditions of the key nervous system (Panda, 1999).O ther benefitsR. sativus is germicidal and suppresses phlegm. It is a good appetizer, speak fresher, laxative, regulates metabolic process, remedy for headache, acidity, piles, nausea, obesity, sore throat, whooping cough, dyspepsia, etc (Nadkarni, 1976 Kapoor, 1990).Chemical constituents of R. sativusGLs are an important and unique several(prenominal)ize of secondary plant metabolites undercoat in the seeds, roots and leaves of R. sativus (Daxenbichler et al, 1991 Blazevic and Mastelic, 2009). GLSs include several naturally occurring thioglucosides with a common social organisation (Figure 2.2) characterized by side chain (R) with varying aliphatic, aromatic and heteroaromatic carbon skeletons, all presumably derived from amino acids by a chain-lengthening process and hydroxyl group groupation or oxidation (Larsen, 1981).In the intact cell, GLs are separated from thioglucosidase (EC 3.2.3.11), an enzyme for the most part known as myrosinase. When the plant cell structure is damaged, myrosinase catalyzes the hydrolysis of GLs to yield D-glucose, sulfate and a series of compounds including isothiocyanates, thiocyanates and nitriles, depending on both the substratum and the reaction conditions, especially the pH (Figure 2.2). GLs are also hydrolyzed by thioglucosidase bodily function of the intestinal microflora (Jeffery and Jarrell, 2001).4-(methylthio)-3-butenyl glucosinolate (glucoraphasatin), 4-(methylsulfinyl) butyl glucosinolate (glucoraphanin) and 4- (methylsulfinyl)-3-butenyl glucosinolate (glucoraphenin) are the most predominant GLs in the root and seeds of R. sativus (Daxenbichler et al, 1991 Carlson et al, 1985). These GLs on hydrolysis by myrosinase yield MTBITC, sulforaphane and sulforaphene respectively. GLs are not uniformly distributed and are highest in the distal end of the root, decreasing in upper root sections with the net level in vegetative tops (Esaki and Onozaki, 1980).Apart from GLs and their breakdown products, R. sativus also contains polyphenolics such as phenolic acid, flavonoids and anthocyanins. Several polyphenolic compounds including sinapic acid esters and kaempferol were detached from R. sativus sprouts (Takaya et al, 2003). 12 acylated anthocyanins (pelargonidin) were isolated from R. sativus red variety (Otsuki et al, 2002). Phytochemical screening showed the presence of other phytochemicals such as triterpenes, alkaloids, saponins and coumarins in R. sativus seeds (Mohamed et al, 2008).The myrosinase catalyzed hydrolysis of glucosinolates. (Adapted from Rusk et al, 2000)Novel classes of plant defensins (small basic cysteine rich peptides) such as Raphanus sativus antifungal peptide 1 and 2 (RsAFP1 and RsAFP2) were isolated from the seeds of R. sativus (Terras et al, 1992a). RsAFP1 and RsAFP2 are highly basic oligomeric proteins composed of small (5 KDa) polypeptides that are rich in cysteine. Both RsAFP1 and RsAFP2 have a broad spectrum antifungal application and show a high degree of spe cificity to filamentous fungi (Terras et al, 1992b). They are active against both phyto infectious fungi such as Fusarium culmorum and Botrytis cinerea (Terras et al, 1992b), human pathogenic fungi such as Candida albicans (Aerts et al, 2007) and occasionally possess antibacterial exercise. However, they are non- venomous to humans and plant cells. R. sativus 2S storage albumins were identified as second new(a) class of antifungal protein (Terras et al, 1992a). They also inhibit the emersion of different plant pathogenic fungi and certain bacteria (Terras et al, 1992a).At least eighter from Decatur distinguishable isoperoxidases were isolated and purified to apparent homogeneity from Korean R sativus roots. Among them are two cationic isoperoxidases such as C1 and C3 and four anionic isoperoxidases such as A1, A2, A3n and A3 (Lee and Kim, 1994). Plant peroxidases play an important design in several physiological functions such as removal of peroxide, oxidation of indole-3-acetic acid and toxic reductants, wound healing and cell wall biosynthesis (Hammerschmidt et al, 1982). Further, peroxidase represents an important component of an early response in plants to pathogen attack and plays a key role in the biosynthesis of lignin, which limits the extent of pathogen spread (Bruce and West, 1989). The products of this enzyme in the presence of a hydrogen donor and hydrogen peroxide have healthful operation and even antiviral activity (Van Loon and Callow, 1983). Recently, a novel heme peroxidase intrinsically resistant to H2O2 was isolated from R. sativus (Japanese daikon), which showed relatively stronger oxidative st energy than that of origin horse radish peroxidase (HRPA2) (Rodrguez et al, 2008).Biological activities of R. sativusEvidence from numerous investigations reveals that the biological and pharmacologic functions of R. sativus are mainly due to its GLs and its breakdown products ITCs (Esaki and Onozaki, 1982 Nakamura et al 2001 Barillari et al , 2006 Papi et al, 2008). These compounds provide to R. sativus its lineament odor and flavor as well as most of their biological properties. GLs and/or ITCs have long been known for their fungicidal, bacteriocidal, nematocidal and allelopathic properties (Brown et al, 1991) and have at packeted intense research interest be trend of their cancer chemoprotective attributes (Fahey et al, 2001 Verhoeven et al, 1997). Polyphenolics, alkaloids, saponins, isoperoxidases and antifungal peptides are also accountable for pregnant part of the health benefits of R. sativus. These constituents are inform to exhibit several biological effects, including radical scavenging activity (Takaya et al, 2003), gut stimulatory, uterotonic and spasmogenic effects (Gilani and Ghayur, 2004 Ghayur and Gilani, 2005), anti-hyper lipoidemic activity (Wang et al, 2002) and anti-atherogenic effects (Suh et al, 2006) and would perhaps work synergistically with GLSs and ITCs of R. sativus.Antioxidant activityDa mage to proteins, lipids and DNA by unstable atomic number 8 species (ROS) and reactive nitrogen species (RNS) can lead to a variety of chronic diseases such as cancer, cardiovascular, inflammatory and age- link up neurodegenerative diseases (Borek, 1997 Richardson, 1993). ROS/RNS can damage cell membranes, break off enzymes, reduce immunity (Ahsan et al, 2003) and induce mutations (Loft and Poulsen, 1996). ROS/RNS are by-products of normal aerobic metabolism and could occur during mitochondrial/microsomal electron transport chain, phagocytic activity or generated from oxidase enzymes and transition metal ions (Nohl et al, 2003 Aruoma et al, 1989). Other sources of ROS/RNS are environmental factors such as pollution, sun damage, cigarette smoke or even some kinds of the foods (Schroder and Krutmann, 2004). These reactive species and the resulting oxidative damages are usually counteracted by the antioxidant defense mechanisms (Bagchi and Puri, 1998). Recent studies evidence that plant-based diets, particularly those rich in vegetables and fruits, provide a goodish amount of antioxidant phytochemicals such as vitamins C and E, glutathione, polyphenolics, sulfur containing compounds and pigments, which offer guard against cellular damage (Dimitrios, 2006).VitaminsAscorbic acid is raise to be the most effective antioxidant in inhibiting lipid peroxidation initiated by a peroxyl radical initiator among several types of antioxidants including a-tocopherol (Fei et al, 1989). Ascorbic acid is also capable of scavenging hydrogen peroxide, privatet oxygen, superoxide and hydroxyl radicals cost-effectively (Fei et al, 1989). It is also voluminous in the regeneration and recycling of tocopherols and -carotene (Niki et al, 1995). legion(predicate) studies have shown that ascorbic acid is effective in lowering the risk of develop cancers (Block, 1991) and cardiovascular diseases (Trout, 1991). In spite of the overwhelming evidence on the health benefits, howeve r, there are reports that demonstrated the pro-oxidant activity of ascorbic acid (Podmore, 1998). Tocopherols are indwelling vitamins with their study(ip) role as antioxidants in protecting polyunsaturated roly-poly pudding acids (PUFAs) and other components of cell membranes and low-density lipoprotein (LDL) from oxidation, thereby preventing the onset of heart diseases (Rimm et al, 1993).PolyphenolicsPolyphenolics is an super comprehensive phrase that covers many different subgroups of phenols and phenolic acids. These compounds are most commonly present in fruits and vegetables. They are essential to the physiology of plants, being involved in diverse functions such as lignification, pigmentation, pollination, allelopathy, pathogen/predator resistance and growth (Haslam, 1996). Polyphenolics include single-ring structure such as hydroxybenzoic acids and hydroxycinnamic acids and multi-ring structure such as flavonoids, which can be further classified into anthocyanins, flavan -3-ols, flavones, flavanones and flavonols. Some of the flavonoids such as flavan-3-ols can be found in their dimeric, trimeric and polymeric forms. Most of the polyphenolics are often associated or conjugated with lolly moieties that further complicate the polyphenolic visibleness of vegetables. Polyphenolics are especially important as antioxidants, because they have high oxidation-reduction potentials, which permit them to act as reducing agents, hydrogen donors, singlet oxygen quenchers and metal chelator (Kahkonen et al, 1999) and alleviate free radical mediated cellular lesion (Shahidi and Wanasundara, 1992).The antioxidant ability of individual polyphenolics may differ, but, as a group, they are one of the strongest groups of antioxidants. The antioxidant activity of a polyphenolic compound is chiefly determined by its structure, in particular the electron delocalization over an aromatic marrow (Tsao and Akhtar, 2005). When these compounds react with a free radical, deloc alization of the gained electron over the phenolic antioxidant and the stabilization of the aromatic nucleus by the resonance effect take place that prevent the lengthening of the free radical-mediated chain reaction (Tsao and Akhtar, 2005).Sulfur-containing compoundsGLs are a group of sulfur-containing compounds found in the cruciferous plants such as R. sativus, broccoli, cabbage, mustard, wasabi etc. These compounds are found to be strong antioxidants, which are indeed through activation of detoxification enzyme mechanisms for the efficient removal of xenobiotics, rather than through direct radical scavenging capability (Zhang and Talalay, 1998). This situation of GLs and its hydrolysis products ITCs is considered as one of the major contributors to its anti-cancer activity (Zhang and Talalay, 1998).Antioxidant activity of R. sativusR. sativus is one of the major sources of dietary phenolic acids and flavonoids, which are mostly present as sugar conjugates (Takaya et al, 2003) . The major phenolic acids found in R. sativus sprout are sinapic acid and ferulic acid, which are present in conjugated form as 1-sinapoyl-1--D-glucopyranoside, -D-(3-sinapoyl) frucofuranosyl -a-D-(6-sinapoyl) glucopyranoside and 1-feruloyl--D-glucopyranoside (Takaya et al, 2003). The major flavonoids present in R. sativus sprouts is kaempferol that occurs in a conjugated form as kaempferol-3,7-O- a-L-dirhamnopyranoside and kaempferol-3-O- a-L-rhamnopyranosyl-(1-4)- -D-glucopyranoside (Takaya et al, 2003).Lugasi et al (1998) demonstrated the strong antioxidant property of squeezed juice call forthed from a black R. sativus root through its ability to donate electrons, chelate metal ions and clean free radicals in a H2O2/OH-luminol system. Since HPLC analysis revealed the presence of a enormous amount of GLs abasement products and polyphenols in the squeezed juice of black R. sativus, antioxidant activity of black R. sativus root could be attributed to these compounds.Takaya et a l (2003) tested methanolic extracts from 11 different plants including Daikon R. sativus sprouts for their ability to scavenge free radicals. Daikon R. sativus sprouts proved to be the most potent, almost 1.8 times more effective than Vitamin C.Souri et al (2004) studied the antioxidant activity of 26 commonly used vegetables in Iranian diet and found that methanolic extract of R. sativus leaf significantly inhibited the peroxidation of linoleic acid as compared to standard antioxidant such as a-tocopherol and quercetin.Katsuzaki et al (2004) found that hot water extract of Daikon R. sativus extract showed more significant antioxidant activity than the extract obtained at an ambient temperature. L-tryptophan was isolated and identified as the compound trustworthy for the antioxidant activity. They also found that L-tryptophan changed to 5-hydroxy tryptophan (5-HTP), a precursor to serotonin in the rat liver microsome model system. A plant-based 5-HTP supplement is popular for its anti-depressant, appetite appetite suppressant and sleep aiding properties.Lugasi et al (2005) further demonstrated that squeezed juice from black R. sativus significantly alleviated the free radical reaction in rats with hyperlipidaemia by decreasing the lipid peroxidation reactions and by improving the antioxidant status.Recent study also showed that R. sativus extract reduced the extent of lipid peroxidation in a demigod dependent manner in rat liver homogenate treated with cumene hydroperoxide by increasing the levels of reduced glutathione and thereby protecting the liver from the toxin induced oxidative damages (Chaturvedi, 2008).Salah-Abbes et al (2008a) showed the protective effect of Tunisian R. sativus root extract against toxicity induced by zearalenone in mice by virtue of its ability to alleviate oxidative stress through stimulation and improvement of the antioxidant status.Polyphenolics in R. sativus may act in a synergistic or analog manner with GLs and/or ITCs and exert their antioxidant activity through inhibition of lipid peroxidation, enhancing the cellular antioxidant enzymes and increasing the glutathione in the cells. Apart from these phytochemicals, R. sativus also contain several classes of peroxidases that could play a significant role in the elimination of toxic peroxides and thus reduce the impact of free radical mediated cellular injury (Wang et al, 2002). disinfectant activityInfectious diseases are the worlds leading cause of untimely death, killing approximately 50,000 people every year. Bacteria have a remarkable ability to develop resistance to most pharmaceutic antibiotics. An increase in such antibiotic-resistant bacteria are menacing the human population with a recurrence of infectious diseases that were once thought to be under check out, at least in developed countries (Pinner et al, 1996). These antibiotic-resistant bacteria have also caused unique problems in treating infections in patients with cancer and AIDS (Denne sen et al, 1998). Since sour and virulent bacteria develop immunity to solitary antibiotics at an horrify speed, there is an imperative need for a holistic targeted approach to search for novel healthfuls from natural sources, especially from plant kingdom.Long before adult male ascertained the existence of microbes, the fact that certain plants had therapeutic potential was very well accepted.Since ancient times, man has used plants as the widespread therapeutic tool to treat common infectious diseases. Some of these traditional medicines are still included as part of the habitual treatment of various(a) maladies. Bearberry (Arctostaphylos uva-ursi) and cranberry juice (Vaccinium macrocarpon) are employed to treat urinary tract infections, while species such as lemon balm (Melissa officinalis), garlic (Allium sativum) and tee tree (Melaleuca alternifolia) are described as broad-spectrum antimicrobial agents (Heinrich et al, 2004).Plant based antimicrobials represent a vast un exploited source for medicines, which need to be explored further. They have an immense therapeutic potential as they are powerful in the treatment of infectious diseases while concomitantly alleviating many of the side effects that are frequently connected with synthetic antimicrobials (Cowan, 1999). Plant based anti-infective agents generally have manifold effects on the body and often act beyond the symptomatic treatment of the infectious diseases. Plants have a about unlimited capacity to produce secondary metabolites, especially for their defense against ravage by microorganisms, insects and herbivores. Many of these secondary metabolites give plants their characteristic odors and also responsible for plant pigments. Antimicrobial phytochemicals are divided into several categories based on their structural similarity as followsPhenolic acidsThese are the simplest bioactive phytochemicals consisting of a single substituted phenolic ring. Cinnamic acid and caffeic acids are the common representatives of this group. Phenolic acids are reported to be effective against viruses (Wild, 1994), bacteria (Brantner et al, 1996) and fungi (Duke, 1985). The number and site of the hydroxyl group on the phenol structure are considered to be related to their relative toxicity to microorganisms. Phenolic acids which are in the higher oxidise state are often more inhibitory towards microorganisms than the one with the lower oxidation state (Scalbert, 1991). Thus the mechanisms thought to be responsible for the antimicrobial activity of phenolic acid could include enzyme inhibition by the oxidized compound through interaction with SH groups or through nonspecific interaction with the microbial proteins (Mason and Wasserman, 1987).QuinonesThey are aromatic compounds with two ketone substitutions in the phenolic ring. They are ubiquitous in nature and show general antimicrobial properties (Duke, 1997). They are extremely active as they can switch between hydro benzoquin one and quinone through oxidation/reduction reactions. Quinones bind with proteins irreversibly, leading to inactivation of proteins and release of function (Stern et al, 1996). They may also make substrates unavailable to the microbes.FlavonoidsThey are phenolic structures containing hydroxyl groups. They are ubiquitous and are commonly found in fruits, vegetables, nuts, tea, wine, honey, etc. They are known to be effective antimicrobial compounds against a wide variety of microorganisms (Cushnie and Lamb, 2005). Catechins are the most extensively researched flavonoids for their possible antimicrobial activity due to their occurrence in green tea (Toda et al, 1989). Flavonoids have the ability to complex with extracellular proteins as well as with bacterial cell walls, rendering them inactive (Cushnie and Lamb, 2005). More oleophilic flavonoids may also have the ability to disrupt microbial membrane (Tsuchiya et al, 1996).Terpenoids and essential oils inherent oils are secondary metabolites that are highly supplemented in compounds based on an isoprene structure (Cowan, 1999). They are called as terpenes and usually occur as di, tri, tetra, hemi and sesquiterpenes. When the compounds contain extra elements such as oxygen, they are called as terpenoids. Camphor, farnesol, artemisin and capsaicin are the common examples of terpenoids. Terpenes and terpenoids are active against an array of bacteria (Habtemariam et al, 1993) and fungi (Rana et al, 1997). Previous research showed that terpenoids present in the essential oils of plants could be useful in the control of Listeria monocytogenes (Aureli et al, 1992). The mechanism action of terpenes is not yet established precisely, but is speculated to be due to the disruption of bacterial cell membrane by the lipophilic terpenoids (Mendoza et al, 1997).AlkaloidsAlkaloids constitute large groups of compounds containing a nitrogen atom in a heterocyclic ring, with a broad range of biological activities. The first med ically functional alkaloid was morphine isolated from Papaver somniferum (Fessenden and Fessenden, 1982). Alkaloids are generally found to have potent antimicrobial activity (Ghoshal et al, 1996). Solamargine, a glycoalkaloid from the berries of Solanum khasianum reported to be useful against HIV infection and intestinal infections associated with AIDS (McMahon et al, 1995). Berberine is an important and frequently studied member of the alkaloid group. It is potentially efficient against trypanosomes (Freiburghaus et al, 1996) and plasmodial infections (Wright et al, 1992). The mode of action responsible for the antimicrobial activity of alkaloids may be attributed to their ability to add with DNA and arresting the metabolic activity of the bacterial cells (Phillipson and ONeill, 1987).Sulfur-containing compoundsSulfur-containing compounds encompass a wide array of compounds and usually found in the plants as glucosides (glucosinolates, alliin, etc). These glucosides, during the ru pturing of the plant cell wall, are hydrolyzed into volatile sulfur compounds such as ITCs, allicin, allyl radical sulfide, diallyl disulfate, etc. Biological activity of sulfur-containing compounds is considered to be chiefly due to glucoside degradation products, as intact glucosides usually display much fewer biological activities than their subsequent hydrolysis products (Donkin et al, 1995).The mechanism of action responsible for the antimicrobial activity of sulfur-containing compounds varies. Antimicrobial activity of ITCs, degradation products of GLs, is thought to be related to its NCS group, in which the profound carbon atom is highly electrophilic, which could interact irreversibly with