University of Food Technologies, Department of Organic Chemistry and Microbiology, 26 Maritza Blvd., Plovdiv, Bulgaria

E-mail address: petkovanadejda@abv.bg, denev57@abv.bg

Abstract Тhe continuous ethanol and water extractions of medicinal plants Cichorium

intybus, Inula helenium, Taraxacum officinalis and Helianthus tuberosus

accumulating inulin-type fructans in their underground parts – roots and tubers

were carried out. The extraction efficiency of inulin and oligofructoses was

followed by TLC. The amount of extracted fructans was determinated by the

spectrophotometric method based on the Seliwanoff reaction with resorcinol as

the absorbance of resulting compound was measured at 480 nm. It was obtained

that the average fructan content was as follows: Cichorium intybus е 33 %, в

Inula helenium - 42-44 %, Helianthus tuberosus – 69 % и Taraxacum officinalis –

34 %, which make them rich sources of soluble dietary fiber, when they were

used in dietary food products.

Introduction Inulin is a polydisperse linear polysaccharide, member of fructan family and serves

as a reserve carbohydrate in underground part of plants from the Compositae

(Astraceae) family such as Cichorium intybus (chicory), Inula helenium (elecampane),

Taraxacum officinalis (dandelion) and Helianthus tuberosus (Jerusalem artichoke).

Inulin consists mainly of β-(2→1) fructosyl fructose units (Fm), and usually but not

always the chain terminate with α-glucopyranose unit (1→2) (GFn) at the reducing end

(Figure 1). A small percentage of inulin molecules have a terminal fructoside unit

found primarily in the pyranose form in aqueous solution. The degree of

polymerization (DP) of inulin varies from 2 to 70 and depends on plant species,

harvesting time and post-harvest conditions. Molecules with DP<10 are called

oligofructoses or fructooligosaccharides (FOSs) and are a subgroup of inulin. The

maximum amount of low- and high-molecular fructans (75-85%) is found in

topinambur as the greater part of topinambur is a low-molecular fraction. Inulin and

FOSs are classified as soluble dietary fiber. They act as prebiotic as stimulate growth

of Bifidobacteria, low glucose blood level, improve mineral absorbtion and possess

immunomodulation effects. Inulin has been increasingly used in various foods due to

its beneficial nutritional attributes . Along with positive healthy effect inulin acts as

texture modifier, decreases caloric value and improves nutritional properties of food.

Material and methods: Moisture content of the dried ground tubers and roots were determinated according AOAC 945.32 method as the drying

process was carried out at 105 °C for 3 hours..

The extraction process was carried as follows: 0,45 g dry sample (roots or tubers) was extracted three times with 95 %

ethanol (40, 40, 20 ml) to obtain low-molecular fraction composed of fructose and FOSs. High-molecular fraction (inulin)

was then extracted by three following water extraction (40, 40, 20 ml). The extraction level of oligofructoses in the ethanol

extracts and of inulin in water extracts were monitored by TLC to observe the extraction rate of fructans and to observe

inulin fractions. Thin-layer chromatography (TLC) was performed on silica gel 60 F254 plates (Merck) with: 1) n-

BuOH:EtOH:H2O (5:3:2) (v/v) as an eluent and the plates were dipped into a detecting reagent diphenylamine-aniline-

acetone-H3PO4; 2) BuOH:i-PrOH:H2O:CH3COOH (7:5:4:2) (v/v) – mobile phase and detecting reagent – diphenylamine-

aniline-H3PO4 acetone (1:1:5:50).

The fructan content in ethanol and water extracts were analyzed spectrophotometrically at 480 nm by resorcinol-

thiourea reagent.

Conclusion

Inulin and oligofructoses content in some medicinal plants has been defined by TLC

and spectrophotometric methods of analysis. From the obtained results we can

conclude that Helianthus tuberosus is the richest source of fructan (50-70 g/100 g),

but the FOSs fractions dominate in the both extracts. Water fractions obtained from

Taraxacum ollicinale consists of short chain-oligofructoses and very small amount of

inulin. The greatest content of high-molecular inulin (40-42 g/100 g) is characteristic

of elecampane. The fructan content in all of the investigated plants increases during

the autumn. The rich content of FOSs and inulin in these plants made them a source of

prebiotics which improve the digestion function and enriches colon with

Bifidobacteria.

Figure 1. Chemical structure of Inulin

(GFm) (Fn)

Number Name of the plant Moisture

content ±SD, %

CV, %

1. Inula helenium L. (elecampane) 8,50 ±0,23 0,15

2 Cichorium intybus L (common chicory) 7,76±0,38 0,24

3 Taraxacum ollicinale Web. (dandelion) 8,46±0,26 0,12

4 Helianthus tuberosus L. (Jerusalem artichoke) 9,66 ±0,3 0,19

Table 1. Moisture content in the roots and tubers of the medicinal plants

0,000

0,050

0,100

0,150

0,200

0,250

0,300

0,350

0,400

320 360 400 440 480 520 560 600 640 680

THEHTWCIECIWTOETOWIHEIHWIHW10IHE10

Abs

Wavelength, nm

No Species Date of

taking

samples

Underground

part

Low molecular

fraction (fructose

and FOSs), g/100 g

High-molecular

fraction (inulin)

g/100 g

Fructan,

g/100 g

1 Inula helenium L 11.11 rootstock 10,9 ±2,2 32,0±2,0

42,9±2,1

2 Inula helenium L 04.10.10 roots 8,3±1,5 32,7± 0,5 41,0±1,8

3 Cichorium intybus L. 04.11

11.11

roots

-

12,1±2,5

16,1 ± 0,06

21,2 ±1,5

33,3 ±2,0

4 Taraxacum officinale Web. 06.11.11 roots 10,7±0,7 23,9±4,2 34,6±2,4

5 Helianthus tuberosus L. 06.09.11 tubers 6,4 ±0,4

43,5±2,5 49,9± 1,4

6 Helianthus tuberosus L. 2010 tubers flour 45,4 ±2,2

23,9±1,0

69,3±2,5

Table 2. Fructan content (g/100 g dw) in underground organs of Composite Family (Astraceae) plants

Figure 3. Absorption spectrum of the complex compounds formed by

interaction of fructans with concentration 1 mg/ml with resorcinol

SD – standard error; CV – coefficient of variation

Figure 2. Thin layer chromatography of inulin and FOSs extraction

Helianthus tuberosus L. Inula helenium L.

Taraxacum officinale Web.

Fructose

Sucrose

FOSs Inulin

Ethnol extracts Water extracts