[89]

The compound MF-2 was obtained from the ethanolic extract was

suspended in water and then consecutively partitioned with

trichloromethane, ethyl acetate and butanol.

The extract was purified by column chromatography. The compound

was isolated as yellow amorphous powder, mp 199-2000C, analysed for

C34H34O20.

The molecular formula of compound was established as C34H34O20 by

mass spectrometry. The UV spectrum exhibited absorption maxima at 267

and 355nm that are characteristic absorption bands of a flavone skeleton.36

In the IR spectrum, along with the signal for an ester carbonyl (1710cm-1

)

signals for hydroxyl group (3414cm-1

), a conjugated carbonyl (1638cm-1

),

and phenyl group (1618,1498cm-1

) were apparent.

The compound gave positive Molisch‟s test1 but did not reduce

fehling solution nor gave positive test with AHP2, indicating its glycosidic

nature, on acid hydrolysis it gave an aglycone, mp. 288-289 and sugars were

identified as D-galactose and D-xylose by tlc.

In order to study the molecular size of the aglycone, glycoside was

thus subjected to systematic analysis.

[90]

AGLYCONE

The aglycone mp. 288-2890C was analysed for C16H12O7, [M

+316]. It

gave all the characteristic colour reaction of flavonoid.

1. The alc. solution of the compound gave white ppt. with zirconium

oxychloride10-11

in presence of citric acid confirmed free hydroxyl

group at position – 3.

2. The aglycone was treated with a solution of boric acid in the presence

of citric acid12-13

in acetone gave colour indicated its free hydroxyl

group at position-5.

3. The aglycone did not give any colour with vanilline hydrochloric

acid15-16

reagent indicating the 7- hydroxyl group was either substitute

or absence.

4. The compound performed purple colour with nitric acid showing the

methoxy (-OCH3) group at position-7.37

5. The compound also gave yellow colour with zirconium oxychloride14

indicating free hydroxyl group at position -5.

6. The alc. solution of the compound gave red brown ppt. with

ammonium molybdate and acetic acid confirming presence of ortho

diphenolic hydroxy group.38

[91]

These reactions are characteristic of 3-dydroxy flavones (flavonols).

So the compound must have got a flavonol nucleus (I).

(I)

The flavonoid nature of the compound was further confirmed by the

UV absorption bands18-19

at 256 (band II) and 371 (band I).

When acetylated, it yielded a tetra acetate and there by indicating the

presence of four hydroxyl groups, in the compound. This was further

supported by broad peak at 3420 cm-1

in the IR- spectrum. The peak at 2850

and 1110 cm-1

showed the presence of methoxy group and analysis of

compound by Zeisel‟s method,54

which was supported by the signal at

3.91 ppm in proton magnetic spectrum.

[92]

On the basis of above fundamental observation the skeleton structure

of the aglycone could be presented as II

The relative positions of these groups have been ascertained on the

basis of colour reactions, chemical degradation and spectral data.

Spectral studies:

The presence of hydroxyl group at the C-4` is evident by the

bathchromic shift of 62nm and increase in intensity of band I in the

NaOMe20

spectrum related to band I of the NaOMe spectrum. Absence of

bath chromic shift in short wavelength after addition of NaOMe in the

methanolic solution of the compound suggested that the C-7 hydroxy group

was either substituted or absence.

OH

OH

OH

OCH3

[93]

Table – I

Ultraviolet absorption maxima of the aglycone

Medium of Spectra Band Position

Band II (nm) Band I (nm)

max

Shift max

Shift

MeOH 257 - 372 -

+NaOMe 245 - 432 62

+AlCl3 273 16 452 80

+AlCl3/HCl 268 - 424 53

+Na OAc 256 - 380 -

+ NaOAc/H3BO3 261 - 390 18

It exhibited a bathochromic shift of 18 nm on addition of sodium acetate

(NaOAc/H3BO3) boric acid to the ethanolic solution thus showing the

presence of vicinal hydroxyl groups of position 3`,4`. It was further

confirmed by the appearance of blue colour on addition of sodium carbonate

to the Shinoda reaction mixture of the aglycone5.

IR Spectrum showed hydroxyl absorption at 3700-3300 cm-1

band at

2920cm-1

due to methylene groups and peak at 1600 and 1660 cm-1

due to

the presence of an , unsaturated formation (C-4 of flovonoid), other

peak at 1500-1600 cm-1

due to an aromatic ring. A broad carbonyl striating

[94]

band in region 1100-1600 cm-1

and other absorption frequency include 1360,

1060, 910 cm-1

.

ALKALYNE DEGRADATION OF THE AGLYCONE :

The aglycone on treatment with 50% ethanolic KOH forms

mono methyl ether of phloroglucinol and protocatechuic acid.

Aglycone 50%

KOH

when the methyl ether of the compound was oxidised with neutral KMnO4

veratric acid was obtained as one of the oxidation products.

[O]

methyl ether of aglycone KmnO4

Phlonroglucinol

mono methyl ether

Protocatechuic acid

+

Veratric acid

[95]

The formation of veratric acid on oxidation of methyl ether and

protocatechuic acid on alkaline fusion place the two hydroxyl groups at

position 3` and 4` of ring. Further the formation of mono methyl ether of

phloroglucinol again confirms the presence of methoxyl group at C-7 of

ring.

1H NMR analysis of the compound showed the presence of five

aromatic protons. Two protons were meta coupled and appeared as doublets

at 6.20 (1H,d, J=2.5 Hz0 and 6.45 (1H,d, J= 2.6 Hz) ppm assignable to

H-6 and H-8 respectively. One meta coupled doublet at 6.8 ppm

(1H,d,J=8.0Hz) corresponds to the H-5` and a doublet integrating for two

protons at 7.60 ppm (J=2.7 Hz) and 7.65 ppm (J= 8.0 Hz 3.0 Hz) were

assigned at to the H-2` and H-6` protons A sharp singlet was obtained at

3.91 ppm corresponding to the three protons indicating the presence of

aromatic methoxyl group and their position at C-7 was ascertained by the

strong fragment at m/z 167 39

.

[96]

Table – II

1HNMR- chemical shifts of the aglycone ppm from TMS

(CDCl3 300MHz)

Assignment Chemical Shifts ( ppm) J- Value (Hz)

H-6 6.20 (1H,d) 2.5

H-8` 6.45 (1H,d) 2.6

H-5` 6.80 (1H,d) 8.0

H-2`` 7.60 (1H,d) 2.7

H-6` 7.65 (1H,dd) 8.0, 3.0

-O CH3 3.91 (3H,s) -

13C NMR spectrum dissolved 16 signals of which could be attributed

to the aglycone unit. The 13

C NMR signals at 115.5 and 120.3 were

assigned to an oxygen free aromatic carbon C-2` and C-6`. C13

NMR of

aglycone C-2, C-3, C-4, C-5 and C-7 (methoxy group) signal appeared at

147.5, 136.2, 175,6, 160.5 and 164.7 respectively, further confirming of the

5,3`,4`, trihydroxy-7 methoxy flavonol (Rhamnetin).

[97]

[98]

[99]

Table – III

13C NMR chemical shift of the aglycone ppm from TMS

(CDCl3-300MHz)

Assignments Chemical shift (ppm)

C-2 147.5

C-3 136.2

C-4 175.6

C-5 160.5

C-6 97.6

C-7 164.7

C-8 91.6

C-9 156.0

C-10 103.8

C-1` 121.8

C-2` 115.5

C-3` 147.4

C-4` 147.4

C-5` 115.8

C-6` 120.3

O CH3 54.5

The Mass fragmentation pattern of the compound was in good

agreement with the above structure. The fragmentation pattern is represented

as follows as scheme-I.

Mass : m/z 316 [M+ ], 315, 301, 287, 167, 137, 109.

[100]

[101]

[102]

-CO

pathway II m/z-287

m/z-315

- CH3

m/z-301

- H - CHO

RDA

cleavage

pathway I

m/z-316 [M]+

m/z-167

m/z-109

m/z-137

Scheme - I

[103]

[104]

Upon the basis of the facts discussed above, the aglycone could

therefore, be represented as III.

This aglycone has already been investigated under the name

rhamnetin. The identity of the aglycone as rhamnetin has been family

confirmed by mp. and their spectral analysis.

(3,5,3`,4` tetrahydroxy 7- methoxy flavone)

[105]

GLYCOSIDE

The glycoside C34H34O20 on hydrolysis gave the aglycone C16H12O7

and xylose and D- galactose as a sugar moieties and gallic acid.

C34H34O20 7%H2SO4 C16H12O7 + C5H10O5

glycoside Aglycone xylose

C6H12O6 + C7H6O5

galactose + gallic acid

Quantitative sugar estimation29-30

confirmed the presence of one moles

of sugar per mole of glycoside and gallic acid.

Position of sugar linkage:

New let us consider the following facts regarding the structural feature

of the glycoside.

3. It gave yellow colour with boric acid in presence of citric acid12-13

and

with zirconium oxychloride14

also, showing the presence of free

hydroxyl group of position – 5.

4. Appearance of red colour with sodium hydroxide and a bathochromic

shift upon the addition, sodium acetate boric acid32-33

reagent suggest

free 3` position.

[106]

As the position – 7, is already blocked by methyl group hence the

position -3 and 4` ultimately is vacant for the site of glycolysation.

Formation of 5, 7, 3`, trimethoxy quercetin by the hydrolysis

permethylated glycoside confirmed the position -3 and 4` to be involved in

glycolysation.

This was further confirmed by the comparison of the glycoside and

glycone by subjecting them to test for flavonols. In this test the glycoside

failed to respond the test for flavonols (3-Hydroxyl group ) where as the

aglycone does well.

As there is only one possible site available for glycolysation. Hence it

might be expedient to conclude have that sugar and gallic acid are present as

bioside type and linked to be the aglycone at position 3` and 4`.

Nature of the sugar linkage:

The 1H NMR spectral shift of the glycoside displayed two aromatic

proton signals at 5.55 (1H,d, J=8 Hz) and 5.70. (1H,d, J=7.3) ppm, these

were attributed to H-1`` glucosyl and H-1``` xylosyl protons respectively. A

broad signal at 3.60-3.87 integrating for ten protons corresponds to the rest

of the sugar protons.

[107]

The conclusion was further confirmed by the permethylation of the

glycoside by Hakomori‟s Method40

followed by hydrolysis. The partly

methylated sugar thus obtained were identified as 3,4, tri-O-methyl D-

glucose and 2,3,4, tri-o- methyl L- xylosyl by confirming their RG value with

2,3,4,6 tetra –O - methyl D- glucose as reference sugar (n BuOH: EtOH:

H2O, 5:1:4 RG = 0. 65 and 1.02 respectively spray AHP).

As the reducing groups of both the sugar were involved in glycosidic

linkage, the glycoside was non reducing in nature.

Easy hydrolysis eliminated the possibility of any C-C-type glycosidic

linkage and suggested the C-O-C type of linkage.

The IR spectrum of MF-2 showed strong absorption band at 3420

(OH), 2970 (C-H), 1650 (C=C, aromatic) 1620 (C=O), 1730-1715 (ester

C=O streaching); 2832 ( - O CH3 group) 1260 (C-O-C , vibration), 1050,

780 cm-1

Its reaction (florescent yellow in UV with AlCl3) and UV spectral date

with diagnostic shift reagents suggested the likely presence of a 3,7, 4`-

trisubstituted flavonol glycoside with hydroxyl group at 5 and 3` position.

The 1H-NMR spectrum of compound spectroscopic, showed

characteristics signals assignable to an anomeric proton at 5.55

[108]

(1H,d, J=8.0 Hz) and 5.70 (1H,d, J= 7.3 Hz) ppm these uses attributed to H-

1`` galactosyl and H-1```` xylosyl proton and methylene proton adjacent to

am ester group at 4.24, (2H,dd, J=6.0, 11.20 Hz) and 4,43 (2H,dd, J= 7.1,

11.20 Hz). Attachment of galloyl group through an ester linkage at C-2`` in

galactose was suggested by the down field shift of 2`` (5.44) in 1H NMR

spectrum.

Three oxygenated methane protons at 3.84 (dd, J= 7.0 Hz) and 3.93

(J=3.5 Hz) together with anomeric proton at 6.93 (2H, ) group, suggested

the presence of a 2``` galloyl galactoside and 4`-xyloside in compound.

Table – IV

1H NMR chemical shift of the glycoside

(DMSO d6 – 300 MHz)

Assignments Chemical Shift ( :ppm) J-Value (Hz)

C-6 6.30 (1H,d, H-6) 2.10

C-8 6.60 (1H,d, H-8) 2.1

C-2` 8.10 (1H,d, H-2`) 9.0

C-5` 7.10 (1H,d, H-5`) 9.6

C-6` 8.10 (1H,d,H-6`) 9.0

gall-C-1`` 5.55 (1H,d, H-1``) 8.0

gall-C-2`` 3.44 (1H,d, H-2``) ---

C-3`` 3.28 (1H,d, H-3``) ---

C-4`` 3.12 (1H,d, H-4``) ---

[109]

C-5`` 3.39 (1H,d, H-5``) ---

C-6`` 3.48, 3.54 (2H,dd, H-6``) 7.1,11.2

galloyl C-2``` 6.92 (1H,s H-2```) ---

galloyl C-6``` 6.90 (1H,s, H-6```) ---

xylose C-1```` 4.78 (1H,s,H-1```) 6.8

C-2```` 3.85 (1H,m, H-2````) -

C-3```` 3.87 (1H, m, H-3````) -

C-4```` 3.90 (1H,m H-4````) -

C-5```` 4.20, 4.23 (2H,H-5````) -

OCH3 3.80 (3H,s) -

The 13

C NMR spectrum of the glycoside the C-3 carbon shifted

upfield by 2.7 ppm and C-2 signal was shifted field by 9.2 ppm the C-4

resonance was also shifted to a down field direction by 1.5 ppm when

compound to rhamnetin the magnitude of these glycosylation. Moreover a

down field shift of C-4 in C13

NMR at 148.8 confirmed this result. The C13

NMR spectrum of compound indicted that carbon signal 9168.2) C -7```of

the galloyl carbonyl unit showed C13

long range. Shift are characterised of

the general pattern of the glycosilation shifts when glycosilation there was

a were able effect on the C-2 and C-3` thus confirming glycosilation at

position 3 and 4`.

[110]

Table – V

13C NMR (DMSO - d6 – 300 MHz)

Assignments Chemical shift ( :ppm)

C-2 156.8

C-3 133.5

C-4 177.6

C-5 160.6

C-6 97.8

C-7 165.0

C-8 91.8

C-9 156.5

C-10 104.9

C-1` 121.0

C-2` 115.5

C-3` 144.6

C-4` 148.4

C-5` 116.3

C-6` 121.9

OCH3 55.7

[111]

gal. C-1`` 101.3

C-2`` 73.6

C-3`` 76.5

C-4`` 69.8

C-5`` 76.5

C-6`` 68.4

gallosyl-C-1``` 103.2

C-2``` 73.6

C-3``` 76.5

C-4``` 75.9

C-5``` 76.6

C-6``` 60.8

gallosyl-C-7```

carbonyl (C=O) 168.2

xylose C-1```` 105.4

C-2```` 74.9

C-3```` 78.2

C-4```` 71.0

C-5```` 66.7

[112]

On the basis of the fore going observation compound was assigned as

rhamnetin 3-O- (2``-galloyl) - –D- galactopyranosyl – 4`- -D-

xylopyranoside.

[113]

EXPERIMENTAL

Chromatography :

TLC (Cellulose silica gel plate) :

1 Butanol – Benzene-Pyridine - H2O

(5:1:3:3, v/v) upper layer % Rf = 0.18

2 n BuOH - AcOH – H2O

(6:1:3, v/v) Rf = 0.47 (Ammonia vapours)

3 EtOAc – MeOH (9:1, v/v) Rf = 0.40

Test :

The alc. solution of the compound 4-5 drops of naphthol solution

was added, on addition of conc. H2SO4 a violet ring1 was formed, on boiling

with fehling solution no reduction was observed and no violet color, when

spot the compound on paper was sprayed with AHP reagent2

and heated at

1000C.

Acid hydrolysis :

50 mg of compound dissolved in minimum amount of ethanol was

refluxed with 70% H2SO4 (50ml) for 3-hrs. The reaction mixture was poured

[114]

in excess of ice cold water and taken in ether. The compound was

crystallised from ethyl acetate, mp- 288-289o.

Sugar:

The remaining aqueous solution was neutralised with barium

carbonate and the filtrate was concentrated on a rotary evaporator. The

concentrate gave positive Molisch‟s test reduced fehling solution and on

cellulose tlc plate gave two spot.

Rf 0.35 and 0.43 (B.A.W., 4:1.5 v/v, spray –AHP) identical with

authentic sample of galactose and xylose respectively.

Aglycone :

Elemental Analysis:-

Found : C = 60.8%, H = 3.8%

Calculated for C16H12O7 : C = 60.81% H = 3.78%

Acetylation :

The aglycone (50mg) was dissolved in pyridine (1.0ml) and heated

with acetic anhydride (3.0 ml) on water both for 7-hours. The reaction

mixture was poured over crushed ice. The residue upon crystallisation with

[115]

methanol-benzene yielded pure rhamnetin tetra acetate C24H20O11, mp.

1930C.

Found : C = 59.52% H = 4.14%

Calculated for : C = 59.50% H = 4.13%

C16H12O7 (COCH3)4

percentage of acetylation :

Found – 35.54 %

Calculated - 35.53%

Methylation :

A solution of aglycone (50mg) in acetone 150 ml was treated with

dimethyl sulphate (Me2SO4) and anhydrous potassium carbonate (15mg) for

four hrs. under reflux. The carbonate was filtered off and washed with

acetone. Acetone filtered and washing were mixed and concentrated under

reduced pressure to a small volume and poured in to ice cold water. The

methylated aglycone was crystallised from methanol as yellow crystalline

mass, mp.1450-147

0 and analysed for methoxyl groups (Zeisels method)

54.

Found : C = 64.50% H = 5.38%

Calculated for : C = 64.51% H= 5.37%

C16H8O3 (OCH3)4

[116]

Percentage of methylation :

Found : 33.35%

Calculated : 33.33%

KMnO4 oxidation of methyl ether of aglycone:

Methyl ether of aglycone (30mg) in acetone solution was refluxed

with KMnO4 (50mg) on a water bath for five hours. The reaction mixture

was cooled, diluted with water and the solvent was removed by distillation.

A solution of sodium bisulphate was added to remove the excess of

manganese dioxide formed. The solution was extracted with ether and the

etherial extract was shaken with aqueous saturated solution of sodium

bicarbonate. This solution was acidified with HCl and repeatedly extract

with ether. The ether extract on concentration gave veratric acid, mp.182. It

was further identified by mmp and co-chromatography (n-butanol saturated

with ammonia spray-bromophenol blue, Rf = 0.42) with an authentic sample

of veratric acid.

Cleavage of the aglycone with KOH:

The aglycone (25mg) was dissolved in minimum amount of ethanol

and refluxed for 6 hours with KOH solution (25%, 3ml). It was acidified

[117]

with dil. HCl and extracted with ether. The ether layer was washed several

times with water until it was free from mineral acid.

This was fractionated in to

1. 5% sodium bi carbonate solution fraction

2. 10% sodium bi carbonate solution fraction

3. 1% sodium hydroxide solution fraction

1. 5% sodium bi carbonate solution fraction:

The fraction was acidified with HCl and extracted with ether. The

ether layer was washed with distilled water to remove mineral acid. In the

solution protocatechuic acid (3,4-dihydroxy benzoic acid) was identified by

co-chromatography with an authentic sample (B:A:W, 4:1:5, v/v) Rf = 0.48,

spray- FeCl3) and mmp which was observed to be 1970.

2. 10% sodium bicarbonate soluble fraction :

This fraction was neutralised with dil. HCl and extracted with ether.

The solution was evaporated. Nothing could be obtained from it.

3. 1% sodium hydroxide soluble fraction :

This fraction was neutralised with dil. HCl and aqueous solution was

shaken with ether. The etherial layer was washed with sodium bi carbonate

[118]

solution and then with water to remove traces of HCl. In the solution

phloroglucinol mono methyl ether was obtained and identified by its mp 720,

mmp and co-chromatography with an authentic sample (B:A:W, 4:1:5, Rf =

0.46,v/v, spray, 1% aq. FeCl3).

Spectral Studies :

UV :

max nm

MeOH : 257, 286 sh, 372

+NaOMe : 245, 432

+AlCl3 : 273, 302sh, 452

+AlCl3/HCl : 268, 424

+NaOAc : 256, 380

+NaOAc/H3Bo3 : 261, 390

IR :

KBr

max : 3700-3300, 3050, 2920, 2832, 1600, 1660,

1500-1600, 1100-1600, 1360, 1060, 910, cm-1

[119]

1H NMR :

(CDCl3, 300MHz)

ppm:

Assignment Chemical Shifts ( ppm) J- Value (Hz)

H-6 6.20 (1H,d) 2.5

H-8 6.45 (1H,d) 2.6

H-5` 6.80 (1H,d) 8.0

H-2` 7.60 (1H,d) 2.7

H-6` 7.65 (1H,dd) 8.0, 3.0

-O CH3 3.91 (3H,s) -

13C NMR :

(CDCl3-300MHz)

ppm:

Assignments Chemical shift (ppm)

C-2 147.5

C-3 136.2

C-4 175.6

C-5 160.5

C-6 97.6

C-7 164.7

[120]

C-8 91.6

C-9 156.0

C-10 103.8

C-1` 121.8

C-2` 115.5

C-3` 147.4

C-4` 147.4

C-5` 115.8

C-6` 120.3

O CH3 54.5

Mass : m/z 316 [M+], 315, 301, 287, 273,167, 137, 109.

Glycoside :

Elemental Analysis :

Found : C = 53.58%, H = 4.67 %

Calculated for C34H34O20 : C=53.54% H=4.46%

[121]

Spectral Studies (glycoside) :

IR KBr

max : 3420, 2970, 2832, 1715-1730, 1650

1620, 1570, 1260, 1050, 845,780 cm-1

1H NMR :

(DMSO -d6 – 300 MHz)

ppm:

Assignments Chemical Shift ( :ppm) J-Value (Hz)

C-6 6.30 (1H,d, H-6) 2.10 Hz

C-8 6.60 (1H,d, H-8) 2.1 Hz

C-2` 8.10 (1H,d, H-2`) J=9.0, Hz

C-5` 7.10 (1H,d, H-5`) J=9.6, Hz

C-6` 8.10 (1H,d,H-6`) J=9.0, Hz

gall-C-1`` 5.55 (1H,d, H-2``) J=8.0, Hz

gall-C-2`` 3.44 (1H,d, H-2``) ---

C-3`` 3.28 (1H,d, H-3``) ---

C-4`` 3.12 (1H,d, H-4``) ---

C-5`` 3.39 (1H,d, H-5``) ---

C-6`` 3.48, 3.54 (2H,dd, H-6``) 7.1,11.2

gall C-2``` 6.92 (1H,s, dd, H-6```) ---

[122]

gall C-6``` 6.90 (1H,s, H-6```) ---

xyl C-1```` 4.78 (1H,s,H-6```) 6.8 Hz

C-2```` 3.85 (1H,m, H-2````)

C-3```` 3.87 (1H, m, H-3````)

C-4```` 3.90 (1H,m H-4````)

C-5```` 4.20, 4.23 (2H,m 5````)

OCH3 3.80 (3H,)

13C NMR :

(DMSO -d6 – 300 Hz)

ppm:

Assignments Chemical Shift ( :ppm)

C-2 156.8

C-3 133.5

C-4 177.6

C-5 160.6

C-6 97.8

C-7 165.0

C-8 91.8

C-9 156.5

C-10 104.9

C-1` 121.0

C-2` 115.5

C-3` 144.6

[123]

C-4` 148.4

C-5` 116.3

C-6` 121.9

OCH3 55.7

gal C-1`` 101.3

C-2`` 73.6

C-3`` 76.5

C-4`` 69.8

C-5`` 76.5

C-6`` 68.4

gallosyl-C-1``` 103.2

C-2``` 73.6

C-3``` 76.5

C-4``` 75.9

C-5``` 76.6

C-6``` 60.8

gallosyl-C-7```

carbonyl (C=O)

168.2

xylose C-1```` 105.4

C-2```` 74.9

C-3```` 78.2

C-4```` 71.0

C-5```` 66.7

Mass : 762 [M+], 617,437, 284, 273, 1`67, 137, 109

(GCMS m/z)