Non-saccharide natural intense sweeteners An overview of current status

Article Natural Product Radiance, Vol. 5(4), 2006, pp.270-278 Non-saccharide natural intense sweeteners An overview of current status S J Surana, S ...
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Natural Product Radiance, Vol. 5(4), 2006, pp.270-278

Non-saccharide natural intense sweeteners An overview of current status S J Surana, S B Gokhale, R A Rajmane and R B Jadhav* Department of Pharmacognosy, R.C.Patel College of Pharmacy Shirpur, Dist. Dhule- 425 405, Maharashtra, India *Correspondent author, address, R B Jadhav c/o Dr S G Chaudhari, Plot No. 60, Pitreshwar Colony, Shirpur, Dist. Dhule 425 405 Phone: 9822948642; E-mail: [email protected] Received 29 July 2005; Accepted 1March 2006

Abstract The global consumption of herbs as medicine, nutraceuticals, food additives, cosmaceuticals, etc. is increasing rapidly. One of such area of high commercial potential is nonsaccharide sweeteners. Numerous compounds of plant origin are reported to have different degree of sweetness. In the light of limitations of currently marketed synthetic sweeteners as well as drastic reduction of high-calorific sugar consumption especially in developed countries, an area of lowcalorific, non-saccharide natural sweeteners is gaining tremendous commercial significance. However, in recent past non-saccharide natural sweeteners gone through several ups and downs, therefore, before commercialization of non-saccharide natural sweeteners for both pharmaceutical as well as food industry, it needs to undergo rigorous evaluations. The present paper is a compilation of information on non-saccharide intense natural sweeteners derived from plant metabolites. Keywords: Plant metabolites, Non-nutritive sweeteners, Natural sweeteners, Intense sweeteners. IPC code; Int. cl.7 — A61 K 35/78, A23L 2/60

Introduction Although the history of human efforts in improving food palatability way backs to time unknown, our understanding of mechanism of taste perception remains preliminary. For several years, high calorific sugars remain main source of sweetening agent. However, changing life-style and sugarrelated health problems such as obesity and dental caries and unsuitability of sugars for diabetic patients, replacement of these high calorific sugars by low calorific intense sweeteners has become necessary. Several synthetic sweeteners of low calorific value have recently been appeared in pharmaceutical and food industries, but their health hazards due 270

to harmful side-effects restrict their utility1,2. Thus, search for non-nutritive intense sweeteners remains potential area of research. This compilation is the account of the non-nutritive intense sweeteners derived from plant metabolites along with various approaches used in discovering new sources. This paper also focuses on the methodology practiced in screening and toxicity testing. Sweeteners are the compounds that interact with taste buds that evoke a characteristic response. Sweeteners, therefore, have ability to impart sweet taste by masking the taste of material in which it is added3. Sweeteners can be broadly divided into two categories, natural and synthetic (or artificial) sweeteners. Natural sweeteners can be further divided

into saccharide and non-saccharide sweeteners. Synthetic sweeteners are further divided into two groups, organic salts and inorganic substituted salts. Although each class has its own merits and demerits, present discussion is confined to the natural non-saccharide intense sweeteners and taste modifying plant metabolites. Ideally, sweeteners should be of low-calorific value, able to mask the taste at lower concentration and it should be free from harmful side effects and suitable for long-term use. It should remain stable at wide range of temperature and pH conditions. It should have quick onset of action and no lingering after taste. Sweetener should be water soluble with high dissolution rate. In addition, it should be non-hygroscopic and should give synergetic effect with other sweeteners. Therefore, in addition to other factors, commercialization of sweetener needs to qualify most of these parameters.

Plant metabolites as sweeteners The chemical structures of molecules that confer a sweet taste are diverse and there are about 80 sweet compounds (other than monosaccharides, Natural Product Radiance

Article disaccharides and polyols) obtained from natural source and most of them are derived from vascular plants 4. Nonsaccharide natural sweeteners are widely distributed in diverse plant families such as Asteraceae, Marantaceae, Rutaceae, Menispermaceae, Polypodaceae, etc. Similarly, widely diverse phytoconstituent classes ranging from small molecular secondary metabolites such as flavonoids, terpenoids, steroidal saponins, coumarins, etc. to macromolecular proteins, reported to have intense sweetening property. In addition, there are certain non-sweet plant metabolites known to modify taste effects which lead to either insensitivity towards bitter or sweet taste or modifying the sour or bitter taste to sweet taste3, 5. In Tables 1 and 2 some of these sweeteners and taste modifying plant metabolites have been summarized.

Strategies for discovering new sweeteners from plants Approaches similar to the drug discovery program have been practiced in discovering new sweeteners from plants 3,5,6. However, some specific clues and simplicity of taste perception are an added advantage in this case. Ethnobotanical information derived from literature and from field investigation can be a rational way in searching new sweeteners. This can be attempted by survey of local population and survey of ethnobotanical information. In former approach, interview with local communities, herbalist and traditional healers gives an idea about sweet plants. However, the information from above sources is not sole mean and many plants Vol 5(4) July-August 2006

with bitter taste may remain unnoticed to local population. In addition, some plants having poor sweetness may also be missed altogether. Also sweet smelling plants are not that usually give sweet taste. Thus, it is necessary to consider these aspects while exploring the ethnobotanical information to avoid subsequent failure in screening program. Third approach is chemotaxonomic tracing, but several times in given genus taste may ranges from sweet-bitter-astringent and probability of success is low. Fourth approach is random screening by organoleptic tasting especially used for undocumented sweet plants. This approach is costly and difficult and needs to investigate each plant from about 2, 40,000 angiosperm species.

Screening assay for sweetness Currently, the chemical properties of molecules that induce sweet tastes are not well understood; this eventually leads to unavailability of reliable in vitro method for screening of sweeteners. However, recent psychophysical, electrophysiological and biochemical studies suggest that sweet taste perception for these structurally diverse compounds may involve multiple receptor types and transduction mechanisms. Several mechanisms have been proposed, including competitive inhibition of sweetener receptors, interference with channels and second messenger systems in the taste cell membrane, and nonspecific interactions with taste cell membranes 4 . This information is quite useful in development of in vitro models. However, currently two in vivo methods, electrophysiological

and behaviour model are used in screening program. In former model, plant extract or enriched fraction is applied on the tongue of anaesthetized gerbil and electrophysiological response recorded from chorda typhani nerve. In this assay, about 25 samples can be investigated in individual animal. This study is further supplemented by conditioned-taste dislike assay using gerbils that are trained to avoid sucrose. Although combination of these two models is not ideal for evaluation of human sweet taste, about 60-70 % of pure compound tested in gerbil respond correctly.

Preliminary safety screening and sweetness evaluation Promising plant found from any of above approach is subsequently extracted and safety screening of crude extract or fractions is undertaken. Acute toxicity is investigated in mice and mutagenicity in bacteria such as Salmonella typhimurium. After the safety assessment, comparative sweetness can be judged from threshold sensory method using panel of healthy human volunteers relative to 2% w/v sucrose. Although taste perception is subjective phenomenon and several factors such as age, hunger, mood, social environment and individual characteristic affect on it, a rough idea of sweetness intensity can be judged from this protocol. Human study is some what problematic, since the large amount of extract, fraction or pure compound is required for investigation. Therefore, in addition to human study, combination of electrophysiological and behaviour model of gerbils can be considered especially when amount of material under investigation is less. 271

Article Table 1 : Natural intense sweeteners of plant origin Botanical/English and Family names

Plant part used

Sweet principle(s)

Sweetness in comparison to sucrose

Applications

Other known pharmacological activity

Comments

Fruits

Protein, Mabinlin

100 times sweeter than sucrose





Fruit

Heterodimeric proteins, Curculin and Neoculin Monellin



Free radical scavenging activity —

Exhibits both sweet-tasting and taste-modifying activities Sweetener —

1. Proteins3, 7-9, 14, 17, 18, 20 Capparis masaikai Levl. Capparidaceae Curculigo latifolia Drynand. Amaryllidaceae Dioscoriophyllum cumminsii Diels., Serendipity berry Menispermaceae

Fruits pulp

Pentadiplandra brazzeana Baill. Capparidaceae Thaumatococcus danielli Benth., Katemfe Marantaceae

Fruits

Pentadin and Brazzein

Fruit aril

Thaumatin I and II

Abrus precatorius Linn., Crab’s eye, Indian liquorice Fabaceae

Leaves and roots

Abrousosides A-E (triterpene glycosides) and Glycyrrhizin

Baccharis gaudichaudiana DC. Asteraceae Glycyrrhiza glabra Linn., Liquorice Fabaceae

Aerial parts

2,000 times sweeter than sugar

500 times sweeter than sucrose 10,000 times sweeter than sucrose



It can be used for diabetic patients and it does not produce dental caries. Unstable at extreme pH, and thermolabile (unstable at 50oC at pH 3.2). Toxicological data is not available. —



Chewing gum, Antifungal breath fresheners, activity flavour enhancer for coffee and peppermint

Stable at pH 2.7-3.0 and can be detected in concentration of 10-8M. Sweetness property not affected by heat. It is marketed as Talin in USA, UK and Japan.

Similar to liquorice in food, beverages and pharmaceuticals







Sweetening and flavouring to confectionary, beverages, cough mixture, lozenges and tobacco

Anti-ulcer, anti-inflammatory, anti-viral, anti-mutagenic activity

Non-toxic terpenoids. Glycyrrhizin is present in roots. Abrousoside E is weak sweetener but its monomethyl ester is potent. It is water soluble pleasantly tasting compound. Devoid of mutagenic or carcinogenic activity. But its inhibitory effect on enzymes involved in steroid degradation leads to hypertension, alteration in cardiac rhythm, edema in abusive consumers.

2. Terpenoids3, 6, 9-12, 20

272

Rootstock and stolons

Abrousosides A-D are 30,100, 50 and 75 times sweeter than 2% w/v sucrose respectively Labdane diterpene 55 times sweeter glycoside, than 2% w/v Gaudichaudioside-A sucrose solution Glycyrrhizin, a Ammonium pentacyclic glycyrrhizinate triterpene and saponin glycoside. glycyrrhizin are Ammonium 100 and 50 times glycyrrhizinate sweeter than commercially sucrose, available respectively

Natural Product Radiance

Article Botanical/English and Family names

Plant part used

Sweet principle(s)

Sweetness in comparison to sucrose

Applications

Other known pharmacological activity

Comments

Illicium verum Hook.f. Star anise Illiciaceae

Dried fruits

Trans-Anethole and estragole (90:1%)

These phenylpropanoids are about 13-15 times sweeter than sugar

Flavouring and sweetening liquors and medicines

Myrrhis odorata (Linn.) Scop. Sweet cicely, Apiaceae

Fresh whole plant

Trans-Anethole and estragole (85:2%)

Estragole reported to causes liver cancer, therefore, higher content of estragole containing plants are not considered for sweetening purpose.

Piper marginatum Wall. Piperaceae

Dried leaves

Trans-Anethole and estragole (80:1%)

Osmorhiza longistylis (Torr.) DC. Apiaceae Lippia dulcis Mich. Honey herb Verbenaceae

Fresh roots

Trans-Anethole (95%)

Trans-Anethole presents no significant risk to human on prolonged use. However, very high doses were hepatotoxic, inducing a small number of hepatocarcinomas in female rats, but not in male rats or mice of either gender.

Aerial parts

Sesquiterpene, 1000 times Hernandulcin, sweeter (+)-4 beta-hydro- than sugar xyhernandulcin



Non-toxic to mice and do not induce mutation in bacteria

Periandra dulcis Mart. Fabaceae

Rhizomes

Triterpene glycosides, Periandrin I-V





It is thermolabile and has unpleasant after taste and inherent bitterness. —

Perilla frutescens (Linn.) Britton Perilla mint Wild coleus Lamiaceae Pinus spp. Pine Pinaceae Stevia rebaudiana Bertoni Stevia Asteraceae

Whole plant

Monoterpenoid, Perillartine (Perillaldehyde)

Perillaldehyde have potential allergen property

Low water solubility and liquorice offflavour restrict use.

Resin

Diterpene acid

Modified compound used for sweetening carbonated beverages —

Antioxidant

Toxicity data not available.

In confectionery, in drinks tea, coffee. Used in liquid and solid foods in Japan

Mutagenic activity of certain metabolites, nephrotoxicity and inhibition of glucose absorption

Thladiantha grosvenori (Swingle) C. Jeffrey Cucurbitaceae

Aerial parts of Cucurbitane climber triterpenoid glycoside, Mogroside-V



Anticancer activity of Mogroside-V has been reported

Treating diabetes. Marketed in Japan, Brazil but in USA it is not approved as ‘Generally Recognized As Safe’ but approved as dietary supplement. —

Leaves

Vol 5(4) July-August 2006

90-200 times sweeter than 2% w/v sucrose solution 2000 times sweeter than sugar

2000 times sweeter than sugar Diterpene tricyclic Stevioside and glycosides, Rebaudiosides Stevioside, are 200 Rebaudiosides A-E, and 100-400 Dulcosides A-B times as sweet as sucrose, respectively 150 times sweeter than sugar

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Article

Glycyrrhiza glabra

Illicium verum

Polypodium glycyrrhiza

Hydrangea macrophylla

Stevia rebaudiana

Piper marginatum

Lippia dulcis

Cynara scolymus

274

Gymnema sylvestre

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Article Botanical/English and Family names

Plant part used

Sweet principle(s)

Sweetness in comparison to sucrose

Applications

Other known pharmacological activity

Comments

Citrus aurantium Christm. Khatta Rutaceae

Fruit peel

Flavonoid, Neohesperidin dihydrochalcone

It is about 1000 times sweeter than sucrose

Neohesperidin is — bitter compound, but when treated with alkali it is converted into sweet compound neohesperidin dihydrochalcone

It is acid-stable compound with menthol-like after taste. The taste is longlasting but develops slowly.

Citrus paradisi Macfad. Grape fruits

Fruit peel

Flavonoid, It is about Naringin 1000 times (bitter compound) sweeter than sucrose

Naringin on — alkaline treatment gives sweet compound, naringin dihydrochalcone

Naringin is also used to prepare neohes-peridin

Citrus sinensis Fruit peel (Linn.) Osbeck. Mosambi Citrus limon (Linn.) Burm.f., Lemon

Hesperidin dihydrochalcone glucoside

On treatment — with dilute alkali, hesperetin is converted into hesperidin dihydrochalcone, which on partial hydrolysis gives hesperidin dihydrochalcone glucoside



Polypodium feii Linn. Polypodiaceae

Rhizomes

Trimeric It is 35 proanthocyanidin, times sweeter Selligueain A than 2% w/v sucrose solution

Pleasantly sweet taste, with only trace of bitterness and astringency

It is elastase inhibitor in human neutrophils and shown analgesic and antiinflammatory activity in experimental animals

No appreciable off-taste, no mutagenicity.

Smilax glycyphylla Mill., Barichob-chini Liliaceae

All parts of plant

Dihydrochalcone glycoside, Glycyphyllin

It is 100-200 times sweeter than sucrose

Chewing gums and various beverages





Symplocos paniculata Miq., Ludh Symplocaceae

Leaves

Dihydrochalcone glycoside, Trilobatin

It is 400-1000 times sweeter than sucrose

Leaves are used as fodder





Tessaria dodoneifolia (Hook. & Arn. ) Cabrera Asteraceae

Young shoots

Dihydroflavonol, (+)- Dihydr oquercetin-3acetate

It is 80 times sweeter than 2% w/v sucrose solution



Non-carcinogenic in experimental animals



3. Flavonoids 3, 4, 15, 16, 20

Vol 5(4) July-August 2006

It is 300 times sweeter than sucrose

275

Article Botanical/English and Family names

Plant part used

Sweet principle(s)

Sweetness in comparison to sucrose

Applications

Other known pharmacological activity

Comments

It is 300-400 times sweeter than sucrose





Delayed onset of sweetness, lingering after taste and low water solubility.

4. Coumarin derivatives 1-3 Hydrangea macrophylla (Thunb.) Ser. Amacha Saxifragaceae 5. Steroidal saponins

Fermented or Dihydrocrushed leaves isocoumarin, Phyllodulcin

3, 20-22

Polypodium glycyrrhiza D. Eaton var. occidentale Liquorice fern Polypodiaceae

Rhizomes

Steroidal saponin glycoside, Polypodoside-A

600 times sweeter than 6% w/v sucrose solution

It is used in both food and medicine



It is used as liquorice substitute. Rhizomes eaten by North American Indians

Polypodium vulgare Linn. Wall fern Polypodiaceae

Rhizomes

Steroidal saponin glycoside, Osladin

Sweetness relative to sucrose is in the range of 300-3000 times

Used to flavour tobacco giving liquorice taste



Osladin yield is very low. Toxicity data not available

Pterocarya paliurus Linn. Juglandaceae

Leaves and stems

Dammarane glycosides, Pterocaryoside A and B

Pterocaryoside A and B are 50 and 100 times sweeter than 2% sucrose respectively



Hypolipidemic and exhibit insulin-like activity in adipocytes, in vitro and in vivo

These are non-toxic and safe sweeteners. Both compounds have a persistent, mildly bitter off taste, but onset of sweet taste is almost instant

Table 2 : Taste modifiers of plant origin 3, 13, 17, 18, 20 Botanical/English and Family names

Parts used

Taste modifying compound

Applications

Other pharmacological activity

Comments

Cynara scolymus Linn., Hathichoke Asteraceae

Leaves and flowers

Caffeolocunic acid, chlorogenic acid and protein, Cynarin

It is reported to be used in diabetic patients

Hepatoprotective and anti-hepatotoxic, antioxidant activity

These compounds sweeten substances of different taste and sweet taste persists for 4-5 hours.

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Article Botanical/English and Family names

Parts used

Taste modifying compound

Applications

Other pharmacological activity

Comments

Gymnema sylvestre (Retz.) Schult., Gudmar, Asclepiadaceae

Leaves

Triterpenoid, Gymnemic acid

It is used as antidiabetic drug

Antidiabetic activity



Larix decidua Mill. European larch Pinaceae

Leaves exudates

Pynone-maltol (Melezitore)

Used as sweet modifier in medicine and bakery products





Syncephalum dulcificum Dan. Miraculous berry Asteraceae

Fruit

Glycoprotein, Miraculin. It is tasteless and transforms acidic taste into sweet taste

Taste modifier for sour foods and modify the perception of various flavours



It induces a risk of confusion due to persistence taste modifying effect. Heat liable, difficult to extract and become inactive at lower pH.

Ziziphus jujuba Lam. Rhamnaceae

Leaves

Terpenoid, Ziziphin

Sweetness reduced by ziziphins; weak by 10 sec 3.5% w/v and strong after 90 sec 0.88% w/v ziziphins whole mouth treatment

Anti-inflammatory activity

No difference was seen in sourness, bitterness or saltiness after ziziphin treatment.

Future prospectus An area of non-saccharide natural sweeteners is evolving, however, lack of in vitro model for screening and long term toxicity testing are important hurdles. This is basically because of inadequate understanding of taste perception mechanisms. However, current knowledge of non-saccharide natural sweeteners can be exploited in various directions. Compounds with proven efficacy and safety can directly be used as sweetener. By chemical modification of natural material, semisynthetic derivatives with improved potency, stability and Vol 5(4) July-August 2006

reduced side effects can also be prepared. A sweetness synergy is another approach in which potency and palatability can be improved at lower amount of sweeteners used in combination. Further, by using natural scaffolds of sweeteners, new sweeteners and their analogs can be discovered. Non-saccharide natural sweeteners and taste modifying plant metabolites can also assist in better understanding of taste-perception mechanisms. In addition to sweetness property some molecules also demonstrated other pharmacological actions; therefore, it can also be exploredto understand the analogy of

sweet taste and other physiological actions of sweetener.

Conclusion The demand of low calorific intense sweeteners is growing not only because of sugar related health problems but also due to rising number of diabetic patients especially in Indian subcontinent. Thus, the extensive efforts are necessary for the search of new sweeteners from various biodiversity regions of India. Although in past, ethnobotanical approach played significant role in discovering sweeteners, an integrated multidisciplinary 277

Article approach is much more anticipated which can involve phytochemist, ethnobotanist, pharmacologist, pharmacognosist, plant biochemist, etc. to ensure fruitful results. The commercialization of plant sweeteners is currently attempted by large scale cultivation and or biotechnological means. The latter approach is found promising for protein as well as some small molecule sweeteners. It was also realized that several phytoconstituents besides being sweet in taste exhibit various pharmacological activities. It will be, therefore, highly appropriate to categorize these sweeteners according to the disease groups (e.g. sweeteners for diabetic patients) to get benefit of their dual properties.

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