Ram Snehi Dwivedi's scientific contributions

Saccharides, the simplest forms of carbohydrates, consist of single sugar units with five or six carbon atoms in a ring form. They are commonly called “sugars”or “sweeteners” because they taste sweet. Monosaccharides consist of one saccharide unit; disaccharides, two units; trisaccharides, three units; and polysaccharides, many units. Oligosaccharides are saccharides with more than three but less than eight units. Lot of literature are available on carbohydrates and saccharide sweet (SS) principles [1, 2], hence pertinent and salient features are presented here.

It is imperative to mention here that SS and NSSS plants neither differ in the basic biochemical routes leading to carbohydrate, protein and fat metabolism nor in the first product of photosynthesis e.g. PGA (C3)/malate (C4)/aspartate (C4)/oxaloacetate (C4) with other plants. The SS and NSSS principles do differ in their chemical structure, intensity of sweetness etc. and their donor plants differ in morphophysiological, biochemical and genetic attributes. Hence the most important distinguishing ecophysiological, ethnobotanical/phylogenic and health friendly attributes of these plant species and functional and synthetic path of NSSS principles are presented here.

For the first time the attempts made in 1963 accompanied with that of 1969 by Horowitz and Gentili [1, 2] succeeded in isolating sweet dihydrochalcones such as naringin, neohesperidin and hesperidin from bitter citrus flovanones (Table 10.1). There after several variants were synthesized but only five compounds were found superior in sweetness. Three original compounds, derived from citrus flavanones e.g. naringin dihydrochalcone (I), neohesperidin dihydrochalcone (II), and hesperetin dihydrochalcone 4-β-d-glucoside (III) and remaining two viz. glycyphyllin and trilobatin obtained from Smilax glycyphylla and Symplocos paniculata respectively are mentioned below in Fig. 10.1

Initially, the super sweet characteristics of the rhizome of a widely distributed fern (Polypodium vulgare L.) was reported to be due to presence of glycyrrhizin in 1885 by Guignet [1]. However, after lapse of more than 8 decades, Herout and co-workers isolated the actual sweet principles present in P. vulgare as osladin, a steroidal saponin, in 1967 [2] and characterized that in 1971 [3]. The structural formula of osladin is presented in Fig. 12.1.

Only during last century, the use of zero/very low calorie natural non saccharide super sweet (NSSS) principles cropped up in the mind of human being after visualizing serious health disorders cause by most popular calorie rich sucrose and lethal effects of zero/very low calorie synthetic sweeteners like asulfame K, sucralose, saccharin etc.

Perillartine is a monoterpene volatile oil obtained from leaves, seeds and flowering tops of plant Perilla frutescens (L.) Britton Perillartine, the a-syn-oxime of perillaldehyde, has been known to be highly sweet since 1920 and reported to be up to 2000 time sweeter than sucrose. In contrast, perillaldehyde itself, the major constituent of the volatile oil of perilla frutescens (L.) Britton (Labiatae), is only slightly sweet [1]. On the other hand, an analogue was synthesized from perillartine called 4-(Methoxymethyl)-1,4-cyclo-hexadien-1-carboxaldehyde syn-oxime was found to be 450 times sweeter, than sucrose [2]. Subsequently another analogue SRI oxime V which was also 450 times sweeter than sucrose was developed [3]. The structural formula of these are mentioned below (Fig. 6.1).

Intensive search on sweetness of natural amino acids started after attaining success in synthesising artificial health friendly super sweet aspartame [1]. Consequently, the sweet natural amino acids identified so for [2, 3] are being re-examined with a hope of searching super sweet nutritive amino acids as the building block of body like that of carbohydrates.

Diterpenoids are 20 carbon terpenes (four C5 units) belong to secondary metabolites, associated with defense activities in plants. Some of the diterpenoids are super sweet in taste with negligible or zero calorie energy and ingrained with antioxidant, antifungal and antibacterial attributes. The following diterpenoids – super sweet principles have been identified so far.

Phyllodulcin is a dihydroiso coumarin NSSS Sweetener, firstly, isolated in 1916 by Asahina and Ueno [1] from Hydrangea macrophylla seringe var. thumbaerg. It is also found in Hydrangea serrata [2] and its sweetness has been reported to be 400–800 times higher than sucrose [3].

Triterpenoids are potential antibiotic substances present in plants Kingdome. Some of them have very sweet taste ranging between 30 and 400 times sweeter than sucrose. Four such natural important non saccharide super sweet (NSSS) principles are mentioned below.