ETHNOPHARMACOLOGICAL AND PHYTOCHEMICAL REVIEW OF ALLIUM (SWEET ) AND SPECIES (WILD GARLIC) FROM SOUTHERN AFRICA

SL Lyantagaye Department of Molecular Biology and Biotechnology, College of Natural and Applied Sciences, University of Dar es Salaam, P.O. Box 35179, Dar es Salaam, Tanzania. E-mail: [email protected], [email protected], Phone: +255-787537030

ABSTRACT Tulbaghia (wild Garlic) is a most closely related to the genus Allium both in the family Alliaceae and is entirely indigenous to Southern Africa. Indigenous people use several species of the genus as food and medicine, and few species are commonly grown as ornamentals. Biological and pharmacological research on Tulbaghia species and their relationship with Allium sativum (sweet Garlic) are presented and critically evaluated. Informations from studies on the treatment of microbes-caused diseases as well as of cancer have been presented in ethnobotanical reports. Moreover, recent scientific studies have been performed on crude extracts for certain Tulbaghia species as reviewed in this article. This article gives a critical assessment of the literature to date and aims to show that the pharmaceutical potential of the members of the genus Tulbaghia is comparable to that of its close relative A. sativum but has been underestimated and deserves closer attention.

Keywords: Allium sativum, Ethnobotany, Ethnopharmacology, Medicinal, Phytochemical, Southern Africa, Tulbaghia

INTRODUCTION species of Tulbaghia have been reported in Tulbaghia (wild Garlic) is a plant genus scientific literature as ethnobotanically used belonging to the family Alliaceae and is a or phytochemically investigated. However, small plant genus of about 30 species all significant information on chemical profile indigenous to the Southern Africa region is available only for one species, Tulbaghia (Williamson 1955, Vosa 1975, Tredgold violaceae, and has been found to be rich in 1986, van Wyk and Gericke 2000, Figure 1) –containing compounds; the and is very interesting from both biological compounds in most cases account for the and chemical perspective. Some member characteristic odours and the medicinal species have been able to adopt foreign properties of both the Tulbaghia and Allium environmental conditions as they are being species. This review will focus mainly on grown in as far as Europe and America the genus Tulbaghia and its (Benham 1993). Most of its member species ethnopharmacological relationship with are closely related to Allium sativum (sweet Allium. Garlic) and hence commonly known as wild garlic. There are many chemical constituents The Alliaceae family that have been identified in the Alliaceae Alliaceae is a family of herbaceous perennial family. The strong onion or garlic smells are flowering , which are monocots in the found in the Tulbaghia and Allium genera, order . The family has been while steroidal saponins are found in most widely but not universally recognized, in the of the species (Dahlgren et al. 1985). The past, the plants involved were often treated medicinal uses of the Allium plants have as belonging to the family Liliaceae. The been widely studied and recorded (Ross Angiosperm Phylogeny Group II system 2003). Only 3 of the 30 distinguished (APG II system) of 2003 recognizes the Tanz. J. Sci. Vol. 37 2011

family and places it in the order Asparagales in the clade monocots.

Figure 1: A map showing countries (Southern Africa) where Tulbaghia plants are indigenous.

The Alliaceae family has about 600 species Genetical relationship between the genera in 30 genera and is a widely distributed Tulbaghia and Allium family (APG 2003). The major places of The physical ends of eukaryotic distribution for the whole family are chromosomes are protected from being Mediterranean Europe, Asia, North and recognised and processed as DNA breaks by South America and Sub-Saharan Africa telomeres. Tandemly repeated short (APG 1998, APG 2003). The Sub-Saharan minisatellite motif of DNA is usually found Africa genera are Allium, Tulbaghia and in the telomeres and is called telomeric (Dahlgren et al. 1985). DNA repeats. Telomere repeats are Probably the most popular genus is Allium, remarkably conserved among eukaryotes, which includes several important food and sequence variation among most of the plants, including garlic (A. sativum and A. major taxonomic groups does not exceed scordoprasum), onions (Allium cepa), one or two nucleotides (Li et al. 2000). In chives (A. schoenoprasum), and leeks (A. plants this particular motif (5’-TTTAGGG- porrum). A strong "oniony" odour is 3’) was first characterised in Arabidopsis characteristic of the whole genus Allium, but thaliana (Richards and Ausubel, 1988) and not all members are equally flavorful has since been found in the majority of plant (Kourounakis and Rekka 1991). A. sativum species (Cox et al. 1993) and is now refered and Allium cepa are worldwide known for to as the Arabidopsis cap. their medicinal use (Ross 2003). However, not all plants share the typical plant telomere sequence and recently the

59 Lyantagaye – Ethnopharmacological and phytochemical review of Allium and Tulbaghia …

presence of this or its variation has been sulfides, propionthiol and vinyl disulfide in used to show genetic similarity. Allium, their essential oils (Dahlgren et al. 1985). Tulbaghia and Nothoscordum (family Alliaceae) are devoid of the Arabidopsis- A. sativum and its extracts have been widely type telomeres (Fay and Chase 1996). Aloe recognized worldwide as agents for (Asphodelaceae) and Hyacinthella prevention and treatment of cardiovascular (Hyacinthaceae), both belonging to and other metabolic diseases, Asparagales, possess human/vertebrate-type atherosclerosis, hyperlipidemia, thrombosis, sequences (5’-TTAGGG-3’) at their hypertension, microbial infections, asthma, chromosome termini (Puizina et al. 2003, and diabetes (Reuter 1995, Reuter et al. Weiss and Scherthan 2002). As all these 1996). The therapeutic properties of A. genera are petaloid monocots in the sativum have been through review in the Asparagales, it suggests that an absence of book called Medicinal Plants of the World Arabidopsis-type telomeres may be (Humana) by Ross (2003). characteristic of this related group of plants (Adams et al. 2000, Weiss-Schneeweiss et The chemistry of Allium species al. 2004). The only other plant genera so far The active components of A. sativum reported without such telomeres are Cestrum include antioxidants such as organosulfur and closely related genera Vestia and Sessea compounds, free radicals scavenger (Solanaceae) (Sykorova et al. 2003). A. cepa flavonoids such as allixin, trace elements (Alliaceae) lacks both Arabidopsis-type and such as germanium (normalizer and human-type telomeres; it possesses an immunostimulant), selenium (for optimal unknown type of telomere. (Sykorova et al. function of the antioxidant enzyme 2006). However, there exist significant glutathione peroxidase), volatile oil differences between members of Allium and containing sulfur compounds, amino acids that of Tulbaghia. For example, A. sativum and other bio-active compounds (Ross has 2n = 3x = 24 and T. violacea has a non- 2003). Garlic chemistry is complex, and a bimodal karyotype (2n = 12) (Fay and number of other compounds are also Chase 1996), which is not suprising for produced in the plant by the aging process. different species. As simply stated, organosulfur compounds are organic molecules that contain the Therapeutics of Allium species element sulfur. Depending on structure, the The genus Allium has about 1250 species, presence of sulfur in an organic molecule is making it one of the largest plant genera in often indicated by a distinctive and the world (Dahlgren et al. 1985). The plants oftentimes unpleasant and ‘loud’ odour. can vary in height between 5 cm and 150 However, organosulfur compounds can also cm. The flowers form an at the top of confer pleasant odour characteristics, as is a leafless stalk. A. sativum is indigenous to observed in garlic and onions. The aroma Asia and probably the most widely used and flavor molecules in garlic and onions are herb in the world (Hyams 1971), but it has derived from precursor compounds that are been grown in most of tropical and derivatives of the amino acid . subtropical region. A. sativum has linear sheathing leaves, globose of white A. sativum and A. cepa (onion) both contain or reddish flowers. The are composed 1-5% dry weight of cysteine derivatives in of “cloves”, which are wrapped in a shared which the proton at sulfur in cysteine is whitish papery coat. The odour is weak replaced with an alkyl or alkenyl when the plant is intact, when damaged the substituent, and the sulfur atom is itself smell grows strong. They are perennial oxidized to the sulfoxide. The cysteine bulbous plants containing mostly sulfoxide derivatives found in onions and organosulfur compounds, such as allyl garlic are indicated in (Figure 2, Scheme 1).

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Onions contain propiin, isoalliin and Hornícková et al. 2010). Alliin exhibits methiin, whereas garlic contains isoalliin, considerable biological activity methiin and alliin (Ichikawam et al. 2006, (Kourounakis and Rekka 1991).

O O

S OH S OH

O NH2 O NH2 Methiin Alliin

O O

S OH S OH

O NH2 O NH2 Isoalliin Propiin

Figure 2: Cysteine sulfoxide (organosulfur) derivatives found in onions and garlic.

O O O O OH O OH O OH S OH S OH S OH O HN O HN O HN NH2 NH2 NH2 O O O !-L-Glutamyl-S-(2-propenyl)-L-cysteine (GSAC) !-L-Glutamyl-S-(trans-1-propenyl)-L-cysteine (GSPC) !-L-Glutamyl-S-methyl-L-cysteine (GSMC)

!-Glutamyl transpeptidase !-Glutamyl transpeptidase !-Glutamyl transpeptidase

Oxidase Oxidase Oxidase

O O O

S OH S OH S OH

O NH2 O NH2 O NH2 (+)-S-(2-propenyl)-L-cysteine sulfoxide (Alliin) (+)-S-(trans-1-propenyl)-L-cysteine sulfoxide (Isoalliin) (+)"S-Methyl-L-cysteine sulfoxide (Methiin)

Scheme 1: Biosynthetic pathway of organosulfer compounds in garlic (Ichikawam et al. 2006).

The distinct flavors of garlic and onion sulfoxide derivatives are contained in the reflect varying amounts of cysteine cytoplasm of the plant cells. In the vacuoles sulfoxides in each plant, most particularly of these cells is contained a class of enzymes isoalliin (higher amount in onion) and alliin known as C-S lyases. If the plant tissue is (higher amount in garlic) (Fritsch and disrupted by cutting/slicing, chopping, Keusgen 2006). Isoalliin is the precursor of chewing etc, the C-S lyase is released, and it thiopropanal S-oxide, the volatile sulfine in subsequently acts upon the cysteine onion that causes tearing. The cysteine sulfoxide derivatives, cleaving the C-S bond

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between the b-carbon and sulfur (Scheme 2). antiviral and anticancer properties, among This cleavage results in two fragments; a others (Ross 2003). Thiosulfinates also putative intermediate, and a- serve as the primary flavor and odour aminoacrylic acid (Block 1992, Shimon et producing molecules in freshly prepared al. 2007). The latter compound garlic and onion macerates. The spontaneously decomposes to ammonia and thiosulfinates participate in a variety of pyruvic acid while the former condenses subsequent reactions which afford a with a second sulfenic acid molecule to form considerable number of organosulfur a class of compounds known as volatiles, such as sulfides, di- and trisulfides thiosulfinates (Block 1992, Shimon et al., and dithiins (Figure 3). These compounds 2007). The importance of the thiosulfinates impart additional flavor, odour and derivatives is from the fact that they have biological activity characteristics to longer been shown to exhibit a variety of biological standing and/or heat-treated macerates. activities, including antibacterial, antifungal,

Scheme 2.: Proposed general mechanism for the catalysis of C-S bond cleavage in Cys sulfoxide derivatives by alliinase (Block 1992, Shimon et al. 2007). Alliin, S- Allyl-L-Cys sulfoxide; 2-hydroxyethiin, S-2-hydroxyethyl-L-Cys sulfoxide; isoalliin, (E)-S-(1-propenyl)-L-Cys sulfoxide; methiin, S-methyl-L-Cys sulfoxide; petiveriin, S-benzyl-L-Cys sulfoxide; propiin, S-propyl-L-Cys sulfoxide.

Because earlier studies established that the the Allium genus whose organo-leptic aforementioned chemistry occurred in garlic properties imply the presence of and onions, and since both are members of organosulfur compounds (Block 2010). the allium family, this chemistry is often Indeed, in the next sections it is shown that referred to as ‘allium chemistry’. However, similar chemistry occurs in T. violacea. there are numerous other plants unrelated to

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Figure 3: A, therapeutically active sulfur compounds from garlic; a representative for each of the three substance classes (allyl sulfides, dithiines, and ajoenes) is shown. B, the enzymatic reaction catalyzed by alliinase (Kuettner et al. 2002).

species are reported in the UK, such as T. Tulbaghia species violacea, T. cominsii, T. acutiloba, T. Of all the members of the family Alliaceae, natalensis, and T. montana, and also in the Tulbaghia is the genus most closely related USA cultivated as decorative plants to Allium and is entirely indigenous to although most are rather tender and are best Southern Africa (Figure 1). The natural grown as warm greenhouse plants (Burbidge distribution extends from Southern Tanzania 1978, Watson and Dallwitz 1992). to Malawi, Botswana, Zimbabwe, Typically, the Tulbaghia species are Mozambique, South Africa, Swaziland and modest, unassuming plants with small Lesotho (Williamson 1955, Vosa 1975, flowers, grassy foliage, sometimes with a Tredgold 1986, van Wyk and Gericke 2000, pungent skunky or alliaceous scent to the Vosa and Condy 2001). Indigenous people rhizomatous rootstalks. A new species of use several species as food and medicine, Tulbaghia (T. pretoriensis), sympatric to and few species are commonly grown as Tulbaghia acutiloba and found in and ornamentals (Vosa 1975, Vosa and Condy around Pretoria was the latest to be 2001). T. violacea is the most well known described in 2006. The two species differ species as medicinal plant species in the from one another in their karyotype, flower genus, especially in the Eastern Cape and morphology and scent, as well in their KwaZulu-Natal regions (Burton 1990, van overall size (Vosa and Gillian 2006, Vosa Wyk et al. 2000). The presence of this 2007). Table 1 shows members on record of species elsewhere is due to cultivation in the small genus Tulbaghia, about 30 plants gardens and in the commercial medicinal species. plant farms (van Wyk et al. 2000). A few

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Table 1: Plant species in the genus Tulbaghia (Burbidge 1978, Vosa 1980, Vosa 2000, Vosa and Condy 2006) Species Common name [local names] Tulbaghia pretoriensis Vosa & Condy. Wild Garlic Tulbaghia acutiloba Harv. Wild Garlic, Wildeknoffel [Afrikaans], sefothafotha [South Sotho], lisela [Swazi], ishaladi lezinyoka [Zulu]. Tulbaghia aequinoctialis Welw. ex Baker Wild Garlic Tulbaghia affinis Link Wild Garlic Tulbaghia alliacea L.f. Wild Garlic Tulbaghia bragae Engl. Wild Garlic Tulbaghia calcarea Engl. & K.Krause Wild Garlic Tulbaghia cameronii Baker Wild Garlic Tulbaghia capensis L. Wild Garlic, Wildeknoffel [Afrikaans], Tulbaghia coddii Vosa & Burb. Wild Garlic Tulbaghia cominsii Vosa Wild Garlic Tulbaghia dregeana Kunth Wildelook, Ajuin [Afrikaans] Tulbaghia friesii Suess. Wild Garlic Tulbaghia galpinii Schltr. Wild Garlic Tulbaghia hypoxidea Sm. Wild Garlic Baker Wild Garlic, sefothafotha [South Sotho] Tulbaghia ludwigiana Harv. Scented Wild Garlic, ingotjwa, sikwa [Swazi], umwelela-kweliphesheya [Zulu] Tulbaghia luebbertiana Engl. & K.Krause Wild Garlic Tulbaghia macrocarpa Vosa Wild Garlic Tulbaghia montana Vosa Wild Garlic Baker Sweet Wild Garlic, iswele lezinyoka [Zulu] Tulbaghia nutans Vosa Wild Garlic Tulbaghia pauciflora Baker Wild Garlic Tulbaghia rhodesica R.E.Fr. Wild Garlic P.Beauv. Wild Garlic Tulbaghia tenuior K.Krause & Dinter Wild Garlic Tulbaghia transvaalensis Vosa Wild Garlic Tulbaghia verdoornia Vosa & Burb. Wild Garlic T. violacea Harv. Wild Garlic, Wildeknoffel [Afrikaans], isihaqa [Zulu] Tulbaghia x aliceae Vosa Wild Garlic

T. violacea is a small perennial bulbous 1992). The plant gives out a strong odour of herb with corm-like rhizomes and narrowly onion or garlic when bruised (Watt and linear, evergreen aromatic leaves. The Breyer-Brandwijk 1962), hence its common flowers are tubular mauve or pale purple, names wild garlic (van Wyk et al. 2000) or occurring in groups of about ten at the tip of society garlic (Watson and Dallwitz 1992). the slender stalk (Figure 4). The plant Inspite of its garlic-like flavor, the prefers partial shade or partial sun to full consumption of T. violacea is not sun; and dry to moist soils. Mature height accompanied by the development of bad ranges from 30 cm to 120 cm depending on breath as is in the case with the the environmental conditions. The plant can consumption of A. sativum and hence be grown successfully in a tub and another common name “sweet garlic” (Kubec transferred to a greenhouse or a frost-free et al. 2002). This suggests that T. violacea place for the winter (Watson and Dallwitz and A. sativum may not contain exactly the

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same volatile chemical compositions. Allium volatile compounds. Thus, However, it was previously reported that T. suggesting that the garlic-like smell of the violacea contain a carbon-sulfur lyase wild garlic is most likely due to the same or enzyme whose action is similar to that of similar sulfur compounds (Burton 1990). It lyases in the various Allium species is, therefore, most likely that T. violacea (Jacobsen et al. 1968). The same study may also contain the medicinal potential suggested the presence of sulfur compounds that is similar to its close relative A. that corresponded with those found in sativum .

a b

Figure 4: ; a) whole plants, and b) flower,

Ethnobotany of Tulbaghia species Some of the Rastafarians eat copious The traditional uses of Tulbaghia species are amounts of it and chili during winter referred to in many folkloric and allegedly “to keep the blood warm” and stop ethnobotanical studies performed in certain aches and pains. Bulbs and leaves soaked in areas of South Africa, where like many other water for a day can be used for rheumatism, the poor Sub-Saharan Africa communities, arthritis and to bring down fever. The bulbs plants are still the primary source of are also used for coughs, colds and flu. Zulu medicine. people also use the plant to repel snakes away from their houses. It is also used for According to van Wyk et al. (2000), T. the treatment of infant and mother in the violacea [common names: Wild garlic case of depressed fontanelle. In the Eastern (English), Wildeknoffel (Afrikaans), Isihaqa Cape T. violacea is used for colic, wind, (Zulu) and Moelela (Sotho)] is used in restlessness, headache and fever, largely for traditional medicine in the Eastern Cape and young children. Like any drug, extensive KwaZulu Natal for problems like fever, use can give adverse symptoms such as colds, asthma, tuberculosis, stomach-ache, abdominal pain, gastroenteritis, acute and cancer of the oesophagus. The bulbs of inflammation and sloughing of the intestinal T. violacea are used as a remedy for mucosa, cessation of gastro-intestina pulmonary tuberculosis and to destroy peristalsis, contraction of the pupils and intestinal worms. The Zulu people use the subdued reactions to stimuli. Tulbaghia to make an aphrodisiac medicine. simmeleri is often used as alternative for T.

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violacea, where the latter is not available literature about the rest of the plant species, (Burton 1990, van Wyk et al. 2000). most probably they are used interchangeably with T. violacea, T. simmleri, and T. Tulbaghia alliacea, has been reported as an alliacea. early Cape remedy for fever, fits, rheumatism, and paralysis (Burton 1990). T. Chemical constituents of Tulbaghia alliacea has the same common name as T. species violacea, i.e., Wild garlic (English), Like in Allium, volatile sulfur-containing Wildeknoffel (Afrikaans), Isihaqa (Zulu) and flavor compounds are responsible for the Moelela (Sotho). T. alliacea is an characteristic smell and taste of Tulbaghia indigenous species in South Africa, growing species. Unlike Allium species, the closely particularly in the Eastern Cape and southern related plant whose chemistry has been KwaZulu-Natal. It is a bulbous plant with extensively studied, only few scientific long, narrow, hairless leaves arising from articles about the chemical constituents of T. several white bases. Brownish green flowers violacea have been published so far. occur in-groups of about 10 or more at the Jacobsen et al. (1968) reported the presence tip of a slender stalk (Robert 2001). Both of a C–S lyase and three unidentified S- the bulbs and leaves of T. alliacea are used substituted cysteine sulfoxide derivatives. medicinally. In Zimbabwe and South Africa Bate-Smith (1968) reported the presence in the leaves of Tulbaghia alliacea are cooked T. violacea of kaempferol (Figure 5). Burton as a relish, alone or with leaves of other and Kaye (1992) isolated 2,4,5,7- plants, such as Adenia species. The rhizome tetrathiaoctane-2,2-dioxide and 2,4,5,7- is scraped clean and boiled with meat in tetrathiaoctane from the leaves of T. stews or roasted as a vegetable. Young violacea. Kubec et al. (2002) isolated leaves are chopped and used to flavour 2,4,5,7-tetrathiaoctane-4-oxide and identified soups, stews, pickles and omelettes as a the three unknown cysteine derivatives that substitute for shallot. In South Africa the had been suggested by Jacobsen et al. (1968) bruised rhizome is used in baths for the as (RSRC)-S-(methylthiomethyl)cysteine-4- relief of fever, rheumatism or paralysis. oxide (marasmin). (SSRC)-S-methyl- and Small doses are used as a laxative (SSRC)-S-ethylcysteine sulfoxides (methiin, (Williamson 1955, Vosa 1975, Tredgold MCSO and ethiin, ECSO, respectively). 1986, van Wyk and Gericke 2000). The Gmelin et al. (1976) were the first to plant is used for fever and colds, asthma, propose that the enzymatic cleavage of pulmonary tuberculosis and stomach marasmin is analogous to that of alliin (S- problems. In the Cape Dutch tradition, T. allylcysteine sulfoxide) in A. sativum and alliacea is used as a purgative and for fits, other alliaceous species. They suggested the rheumatism and paralysis. Also tea can be formation of S-(methylthiomethyl) made from chopped bulbs and roots and (methylthio) methanethiosulfinate (2,4,5,7- used as a purgative. Extracts of T. alliacea tetrathiaoctane-4-oxide, marasmicin, 2 in exhibit anti-infective activity against Sheme 3) from marasmin as the primary Candida species in vitro (Thamburan et al. breakdown product. 2006). The Khoikhoi and Basotho use the plant to make a brew from the chopped The presence of a C–S lyase in T. violacea bulbs and roots (Robert 2001). (Jacobsen et al. 1968), suggests the close genetic relationship with Allium species, The bulbs of Tulbaghia cepacea are also due to marasmicin being in close recommended for tuberculosis and as an analogy to the alliin/ system, make it anthelmintic (Watt and Breyer-Brandwijk reasonable to assume that a similar 1962). Nothing has been reported in mechanism is also operating in T. violacea.

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6 CH2OH 5 O H H H 4 1 OH H OH OCH3 7 3 2 OH Figure 5: Kaempferol H Figure 6. Methyl-%-D-glucopyranoside (MDG).

O O H NH2 1 S S C-S lyase S SOH - /2 H2O S S COOH S S

(RSRC)-S-(methylthiomethyl)cysteine-4-oxide, 1 marasmicin, 2

Scheme 3: Formation of marasmicin, 2, from (RSRC)-S-(methylthiomethyl)cysteine-4-oxide, 1, in T. violacea.

Marasmicin is unstable and further S-alk(en)yl cysteine sulfoxides, decomposes giving various sulphur- thiosulfinates, polysulfides, fructose and containing degradation products, e.g. glucose compounds have been found from 2,4,5,7-tetrathiaoctane, 2,4,5,7- the aqueous extract T. alliacea. Also, a tetrathiaoctane-2,2-dioxide, 2,4,5,7- furanoid compound [5-(hydroxymethyl)-2- tetrathiaoctane-4,4-dioxide, or 2,4,5,7- furfuraldehyde] was identified as an artefact tetrathiaoctane-2,2,7,7-tetraoxide (Kubec et compound generated by the acid hydrolysis al. 2002). Other classes of compounds step. This compound occurs as a product reported in T. violacea are flavonols e.g. from the acid-catalyzed dehydration of kaempferol (Figure 5), and fructose (Maoela 2005). saponins/sapogenins, which are generally present in Allium and Tulbaghia (Watson Krest et al. (2000) reported the presence of and Dallwitz 1992). Burton (1990) S- methyl-L-cysteine sulfoxide (MCSO, identified free sugars including glucose, methiin), S-propyl cysteine sulfoxide fructose, sucrose, maltose, arabinose, (PCSO, propiin), S-allyl-L-cysteine rhamnose, xylose and galactose, and sulfoxide (ACSO, alliin) and S- (trans-1- glycosides from an aqueous extract of T. propenyl)-L-cysteine sulfoxide (PeCSO, violacea. Lyantagaye and Rees (2003) and isoalliin) in considerable amounts in T. Lyantagaye et al. (2005) have reported the acutiloba. These compounds have been well presence of glucopyranoside “Methyl-%-D- known to occur in most Allium species. glucopyranoside (MDG)” (Figure 6) from T. Also, the presence of lectin-like proteins violacea aqueous extracts. have been reported more than once

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(Gaidamashvili and van Staden 2002a, Kaempferol consumption in tea and broccoli 2002b, 2006). has been associated with reduced risk of heart disease (Park et al. 2006). Bioactivity of Tulbaghia species extracts The compounds 2,4,5,7-tetrathiaoctane-2,2- More studies have also shown that extracts dioxide and 2,4,5,7-tetrathiaoctane from the from Tulbaghia species control plant fungal leaves of T. violacea, reported by Burton pathogens by inhibiting their growth and Kaye (1992), were found to have (Lindsey and van Staden 2004, Vries et al. antibacterial activity (Burton 1990). Crude 2005, Nteso and Pretorius 2006). aqueous extracts from T. violacea have been Gaidamashvili and van Staden (2002a, shown to exhibit apoptosis inducing ability, 2002b, 2006) reported the isolation of and so the extacts contain potentially lectin-like proteins and their prostaglandin anticancer agents (Lyantagaye and Rees, inhibitory activity and Staphylococcus 2003). Two years later, Lyantagaye et al. aureus and Bacillus subtilis growth (2005) remarked on the promising anticancer inhibition. There have also been roports on activities of T. violacea - derived the potential anti-infective remedy for fungal compounds containing a methyl-%-D- infections (Motsei 2003, Bull et al. 2005, glucopyranoside (MDG) moiety in their Thamburan et al. 2006). ACE inhibitor structure (Figure 6). The MDG structure has activity and lowering of blood pressure and been postulated to interfere with the bio- down regulating of AT1a gene expression in activities of hexokinase, as well to induce a hypertensive rat model have been reported reactive oxygen species, which cause cellular (Mackraj and Ramesar 2007, Mackraj et al. damage and hence apoptotic cell death 2007). More recently, Ebrahim and Pool (Cohen et al. 2002, Pastorino et al. 2002, (2010) reported that T. violacea has Lyantagaye 2005). This was the first time T. androgenic properties; treatment of cells violacea – derived MDG was reported to kill with T. violacea increased LH-induced cancer cells by inducing apoptosis in the testosterone production. cells. Current research efforts focus on understanding the exact mode of action of CONCLUSION MDG and other related plants from the the Plants are known to be important sources of plant extracts. therapeutic agents. This implies that compounds or mixture of compounds that An in vitro study by Kowalski et al. (2005) have activity in mammalian cells are showed that the flavonoid kaempferol potential therapeutic agents and can be used inhibits monocyte chemoattractant protein as leads towards the development of new (MCP-1). MCP-1 plays a role in the initial drugs. Only reports for biological activity of steps of atherosclerotic plaque formation. 4 of the 29 species of Tulbaghia exist, and The kaempferol and quercetin seems to act significant phytochemical investigations synergistically in reducing cell proliferation have been conducted on only 1 of them. of cancer cells, meaning that the combined Sulfur-type compounds seem to be typical treatments with quercetin and kaempferol are for the genus as they were found from more effective than the additive effects of several species. Among these compounds, each flavonoid (Ackland et al. 2005). An 8- kaempferol and other sulfur compounds are year study found that three flavonols most remarkable and have received much (kaempferol, quercetin, and myricetin) scientific attention because of their anti- reduced the risk of pancreatic cancer by 23 cancer potential. Clearly, members of the percent (Nöthlings et al. 2008). Many genus Tulbaghia possess significant glycosides of kaempferol, such as pharmacological potential and promising kaemferitrin and astragalin, have been activities of extracts in the context of isolated as natural products from plants. ethnomedicinal knowledge, and therefore

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