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Humic substances and associated small molecules from peats in balneology
The Science of the Total Environment, 117/118 (1992) 561-567 Elsevier Science Publishers B.V., Amsterdam
561
Humic substances and associated small molecules from peats in balneology W. Flaig Otto-Hahn-Strasse 132, D-8708 Gerbrunn, Germany
ABSTRACT The therapeutic effect of peat has been known for a long time. The application of peat to medicine is mainly in the recouperation to working capability of a patient after illness or an operation, in rheumatism and in special cases for gynaecology. Furthermore bactericidic, fungistatic, anti-viral and perhaps also cacinostatic effects have been observed. Knowledge of these effects are, at present, mostly empirical. To elucidate the mechanism of action, several natural scientists and medical research workers co-ordinated their efforts. The differences in conditions for the formation of low-bog and raised-bog peat cause differences in the composition of their constituents. The separation of the different fractions of peat using conventional methods is described. The bitumen and humic acids fractions are the most therapeutically interesting. Substances in the bitumen fraction, such as sterins and hormones, and precursors of humic acids such as lignin degradation products, are of physiological interest for their variety of biochemical reactions. The high molecular weight, spherical, colloidal humic acids are important for the transport of heat from a peat-slurry bath, into the nucleus of the body of the patient.
Key words: peat; balneology; humic substances; physiological and physical effects
INTRODUCTION
Peat has been used for a long time in medicine and for the last 200 years interest in such uses has increased. However in recent decades investigations of the therapeutic effects of peat constituents have been studied even more intensively. In the last few years different disciplines of natural sciences and medical research have combined to form a special working group to investigate the mechanisms of the effects of peat in balneology (Flaig et al., 1988). Otherwise the use of peat in medicine is under the medical care of the State. The so-called 'bath' industry is an important economic factor in some regions such as the middle and east of Europe. The substances from peat which are effective in biological processes have low molecular values. Most are known to be physiologically active compounds, as well as precursors for
562
w. FLAIG Minerals
IIIlllLlll!Ull Cellulosl
~ater
natural humidity
Fig. 1.
water free
Main constituents of bath peat.
the synthesis of humic substances. Those peat components of high molecular weight, mostly humic acids, are important in physical processes.
Compositions of peat for balneology The major constituents of peats that are relevant to balneology are shown in Fig. 1. Pectins and tannins are among the water soluble substances; TABLE 1 Differences (% contents) of some fractions of raised-bog and low-bog peats (from lower Saxony, in the northern part of Germany) used in balneology
Ash content N-content Water soluble organic substances Bitumen 'Steroid-fraction' Humic substances aAverage of 14 samples. bAverage of 25 samples.
Raised-bog peat a
Low-bog peat b
4.8 1.3 1.4 9.5 3.4 30.5
35.7 3.3 0.6 4.2 1.4 36.5
PEAT HUMIC SUBSTANCES IN BALNEOLOGY
563
bitumens, the benzene-alcohol soluble substances. The cellulose and hemicelluloses are hydrolysable to simple sugars (glucose in the case of cellulose). The humic acids and humins are the classical fractions of humic substances. Lignins are present in non-humified plant materials in peats. Raised-bog and low-moor peats can be used in balneology. The differences in the compositions of peats can be related to the origins of the peats, as indicated in Table 1. In raised bogs the contents of water-soluble substances lignins OH
~
OH
~1- cour7,,c r i¢
CH CH CH otld H il II CH CH CH I I I COOH COOH COOH Shortening o! the sldechain and ox{dat~on OH
COOH
OH
vonill;e
OH
+
- syr;r,g:c COOH
COOH
/
p - h,,,droxv-benz
~Cc
oc;d
Demelhylot,on
OH
OH
keoln~Cacd ;s~oC fe lCvlog-eh te ~ C H . r~n~
H y d r o ~ y l o t ~on
---HO'~OH
COOH
COOH goltic acid
prctocalechu~c
Oxidative decafboxylol;on o
o
Pol)'merisa~ion 0 rr,ethoxy-
0 hydroxy-
OH O
H O HO" v
OH
p- benz oqu,none
~
COOH
purpurogc11Fn - 9
¢otboxylic cold
F i g . 2.
Transformations of lignin degradation products.
564
W.FLAIG
and of bitumens (with steroid and hormone contents) are greater than for the low-moor peats. Should the content of high molecular weight humic substances be the only factor responsible for the effects of therapeutic baths, then both high-moor and low-moor peats should have the same effects. However this is not always the case, especially in gynaecological applications.
Lignin degradation products as low molecular weight constituents of peats There is interest in the therapeutic effects of low molecular weight precursors of humic substances, such as those obtained from lignin degradation products, which can be isolated from peats. Some of these compounds are listed in Fig. 2. Products such as the different phenol-acrylic acids, ferulic acid for example, are transformed by oxidation of the side chains to give methoxy and hydroxy substituted benzene carboxylic acids. Demethylation of the methoxy groups and further substitution of the aromatic nucleus with hydroxy groups gives rise to polyhydroxy benzene carboxylic acids. Oxidative decarboxylation gives hydroquinone derivatives and these give rise to quinones, which can dimerize and polymerize. In the presence of amino acids and N-containing degradation products of proteins humic macromolecules can be formed. Using different synthetic models of humic substances of the types described, products were obtained which had antibiotic, anti-viral and perhaps even
Function of Lignin Degradation Products such as Vanillic or Gallic Acid in Arachidonic Acid Cycle Avoidance of Inflammations Phospholipids ________~__~__~COOH
Arachidonic Acid
/
\
Inhibition by Vanillic
Leucotriensynth/esis Fig. 3.
or Gallic
Acid
Prostag'~andinsynthesis
Inhibition of arachidonic acid cycle by vanillic and gallic acid.
565
PEAT HUMIC SUBSTANCES IN BALNEOLOGY
L,ight-colored OH dehydrogenation ~ O C H 3 polymers q
OH
COOH ~ %
0
0
oo .3co.~-"-..___~-.~oc.
COOH CO0.
Demethylationl
o
o
o
OH
""n/
0
o
C)ark-colored products
I,
OH
.~co~/-~__~j~oc.3
COOH
O
o
H O ~ O H o
o
Fig. 4. Transformations of vanillic acid under biologicallyactive conditions.
carcinostatic effects. Furthermore, vanillic and gallic acid were found to have physiological effects. For example, these compounds were shown to suppress different inflammations by inhibiting leucotrien and prostaglandin synthesis (Fig. 3) in the arachidonic acid cycle (Quecke et al., 1989) It is clear that many of the transformation products of the added compounds (e.g. vanillic acid), which can be formed in biological systems, are also physiologically active. The transformations of vanillic acid under biologically active conditions are outlined in Fig. 4. Thus it appears that only low molecular weight substances are active. Uptake occurs through the skin and transport by the blood stream. Transport into the blood stream is enhanced by the same conditions which apply in a peat-slurry bath, and especially by the heat which it supplies.
I
I
I
I
I
I
I
I
I
I
I
I
/
added amount of water 7okg
I,o I
i
l l l l l l
amount of water of fresh peat 126kg illlllllt
]J lJlqt if It lli
ipeat drywelgbt ~4 kg,II~
IH r-1
Fig. 5. Composition of a peat-slurry bath.
Total amount of water 196 kg
566
w FLAIG
Influences of high molecular weight substances in a peat bath A normal peat-slurry bath is prepared using 140 kg of fresh peat, to which about 70 kg water is added (Fig. 5). The consistency of the medium is tested by writing a letter with a finger on the surface. The letter must be visible for about 1 min. The temperature is on average between 42 and 44°C. The patient remains in the bath between 15 and 30 min. The essential difference between a water bath and a peat-slurry bath is that, in case of a water bath, the heat is transported very quickly to the body of the patient by convection. Thus, the sensation is very unpleasant. In a peat-slurry bath the heat is transported from particle to particle to the body of the patient, and therefore transport is much slower. In this way the amount of heat transferred to the body of the patient is 7-times more than in a water bath. Humic acids play an important role in heat transport. Figure 6 presents an electromicrograph of isolated humic acids in a weakly acidic medium. In acidic media the acidic groups are in hydrogen-exchanged form. Inter-and intramolecular hydrogen bonding gives rise to structures, which are roughly spherical in outline, and water is included in the matrix. Furthermore they can also be regarded as high molecular weight redox systems and this may influence many reactions on the skin. Because patients are sometimes reluctant to participate in experiments, there have been a number of investigations carried out with pigs (Kaemmeter, unpublished). Infrared photography of pigs after immersion in peat slurry-baths have shown that the heat is not evenly distributed. The heat can persist for prolonged periods in some regions. Changes in the rates of metabolism can take place in the hotter regions.
Fig. 6.
Purified humic acids in weak-acidic medium (electromicrograph).
PEAT HUMIC SUBSTANCES IN BALNEOLOGY
567
CONCLUSIONS The highly significant advances made in the studies of humic substances recently, as indicated by the publications o f the International Humic Substances Society, should provide the stimulus for in-depth investigations of the biochemical effects o f humic constituents. Although the results of biological applications using peat and humic substances are obvious, the evidence for cures and for improved health benefits is largely empirical up to now and will therefore need to be verified by more rigorous experimentation. Humic science has now reached the stage where meaningful results can be obtained about the benefits to balneology of humic substances from peats. REFERENCES Flaig, W., C. Goecke, and W. Kauffels, 1988. Moortherapie- Grundlagen und Anwendungen, Ueberreiter Wissenschaft, Wien, Berlin, pp. 1-308. Quecke, K., G. Loschen and C. Goecke, 1989. Zur Penetration von Huminstoffen durch die Scheidenhaut. In: H. Hornig (Ed.), Arbeitstagung des Arbeitskreises Gyn/ikologische Balneotherapie 1989, Vol. 33, Bad Waldsee, 7967 Bad Waldsee, pp. 162-165.
561
Humic substances and associated small molecules from peats in balneology W. Flaig Otto-Hahn-Strasse 132, D-8708 Gerbrunn, Germany
ABSTRACT The therapeutic effect of peat has been known for a long time. The application of peat to medicine is mainly in the recouperation to working capability of a patient after illness or an operation, in rheumatism and in special cases for gynaecology. Furthermore bactericidic, fungistatic, anti-viral and perhaps also cacinostatic effects have been observed. Knowledge of these effects are, at present, mostly empirical. To elucidate the mechanism of action, several natural scientists and medical research workers co-ordinated their efforts. The differences in conditions for the formation of low-bog and raised-bog peat cause differences in the composition of their constituents. The separation of the different fractions of peat using conventional methods is described. The bitumen and humic acids fractions are the most therapeutically interesting. Substances in the bitumen fraction, such as sterins and hormones, and precursors of humic acids such as lignin degradation products, are of physiological interest for their variety of biochemical reactions. The high molecular weight, spherical, colloidal humic acids are important for the transport of heat from a peat-slurry bath, into the nucleus of the body of the patient.
Key words: peat; balneology; humic substances; physiological and physical effects
INTRODUCTION
Peat has been used for a long time in medicine and for the last 200 years interest in such uses has increased. However in recent decades investigations of the therapeutic effects of peat constituents have been studied even more intensively. In the last few years different disciplines of natural sciences and medical research have combined to form a special working group to investigate the mechanisms of the effects of peat in balneology (Flaig et al., 1988). Otherwise the use of peat in medicine is under the medical care of the State. The so-called 'bath' industry is an important economic factor in some regions such as the middle and east of Europe. The substances from peat which are effective in biological processes have low molecular values. Most are known to be physiologically active compounds, as well as precursors for
562
w. FLAIG Minerals
IIIlllLlll!Ull Cellulosl
~ater
natural humidity
Fig. 1.
water free
Main constituents of bath peat.
the synthesis of humic substances. Those peat components of high molecular weight, mostly humic acids, are important in physical processes.
Compositions of peat for balneology The major constituents of peats that are relevant to balneology are shown in Fig. 1. Pectins and tannins are among the water soluble substances; TABLE 1 Differences (% contents) of some fractions of raised-bog and low-bog peats (from lower Saxony, in the northern part of Germany) used in balneology
Ash content N-content Water soluble organic substances Bitumen 'Steroid-fraction' Humic substances aAverage of 14 samples. bAverage of 25 samples.
Raised-bog peat a
Low-bog peat b
4.8 1.3 1.4 9.5 3.4 30.5
35.7 3.3 0.6 4.2 1.4 36.5
PEAT HUMIC SUBSTANCES IN BALNEOLOGY
563
bitumens, the benzene-alcohol soluble substances. The cellulose and hemicelluloses are hydrolysable to simple sugars (glucose in the case of cellulose). The humic acids and humins are the classical fractions of humic substances. Lignins are present in non-humified plant materials in peats. Raised-bog and low-moor peats can be used in balneology. The differences in the compositions of peats can be related to the origins of the peats, as indicated in Table 1. In raised bogs the contents of water-soluble substances lignins OH
~
OH
~1- cour7,,c r i¢
CH CH CH otld H il II CH CH CH I I I COOH COOH COOH Shortening o! the sldechain and ox{dat~on OH
COOH
OH
vonill;e
OH
+
- syr;r,g:c COOH
COOH
/
p - h,,,droxv-benz
~Cc
oc;d
Demelhylot,on
OH
OH
keoln~Cacd ;s~oC fe lCvlog-eh te ~ C H . r~n~
H y d r o ~ y l o t ~on
---HO'~OH
COOH
COOH goltic acid
prctocalechu~c
Oxidative decafboxylol;on o
o
Pol)'merisa~ion 0 rr,ethoxy-
0 hydroxy-
OH O
H O HO" v
OH
p- benz oqu,none
~
COOH
purpurogc11Fn - 9
¢otboxylic cold
F i g . 2.
Transformations of lignin degradation products.
564
W.FLAIG
and of bitumens (with steroid and hormone contents) are greater than for the low-moor peats. Should the content of high molecular weight humic substances be the only factor responsible for the effects of therapeutic baths, then both high-moor and low-moor peats should have the same effects. However this is not always the case, especially in gynaecological applications.
Lignin degradation products as low molecular weight constituents of peats There is interest in the therapeutic effects of low molecular weight precursors of humic substances, such as those obtained from lignin degradation products, which can be isolated from peats. Some of these compounds are listed in Fig. 2. Products such as the different phenol-acrylic acids, ferulic acid for example, are transformed by oxidation of the side chains to give methoxy and hydroxy substituted benzene carboxylic acids. Demethylation of the methoxy groups and further substitution of the aromatic nucleus with hydroxy groups gives rise to polyhydroxy benzene carboxylic acids. Oxidative decarboxylation gives hydroquinone derivatives and these give rise to quinones, which can dimerize and polymerize. In the presence of amino acids and N-containing degradation products of proteins humic macromolecules can be formed. Using different synthetic models of humic substances of the types described, products were obtained which had antibiotic, anti-viral and perhaps even
Function of Lignin Degradation Products such as Vanillic or Gallic Acid in Arachidonic Acid Cycle Avoidance of Inflammations Phospholipids ________~__~__~COOH
Arachidonic Acid
/
\
Inhibition by Vanillic
Leucotriensynth/esis Fig. 3.
or Gallic
Acid
Prostag'~andinsynthesis
Inhibition of arachidonic acid cycle by vanillic and gallic acid.
565
PEAT HUMIC SUBSTANCES IN BALNEOLOGY
L,ight-colored OH dehydrogenation ~ O C H 3 polymers q
OH
COOH ~ %
0
0
oo .3co.~-"-..___~-.~oc.
COOH CO0.
Demethylationl
o
o
o
OH
""n/
0
o
C)ark-colored products
I,
OH
.~co~/-~__~j~oc.3
COOH
O
o
H O ~ O H o
o
Fig. 4. Transformations of vanillic acid under biologicallyactive conditions.
carcinostatic effects. Furthermore, vanillic and gallic acid were found to have physiological effects. For example, these compounds were shown to suppress different inflammations by inhibiting leucotrien and prostaglandin synthesis (Fig. 3) in the arachidonic acid cycle (Quecke et al., 1989) It is clear that many of the transformation products of the added compounds (e.g. vanillic acid), which can be formed in biological systems, are also physiologically active. The transformations of vanillic acid under biologically active conditions are outlined in Fig. 4. Thus it appears that only low molecular weight substances are active. Uptake occurs through the skin and transport by the blood stream. Transport into the blood stream is enhanced by the same conditions which apply in a peat-slurry bath, and especially by the heat which it supplies.
I
I
I
I
I
I
I
I
I
I
I
I
/
added amount of water 7okg
I,o I
i
l l l l l l
amount of water of fresh peat 126kg illlllllt
]J lJlqt if It lli
ipeat drywelgbt ~4 kg,II~
IH r-1
Fig. 5. Composition of a peat-slurry bath.
Total amount of water 196 kg
566
w FLAIG
Influences of high molecular weight substances in a peat bath A normal peat-slurry bath is prepared using 140 kg of fresh peat, to which about 70 kg water is added (Fig. 5). The consistency of the medium is tested by writing a letter with a finger on the surface. The letter must be visible for about 1 min. The temperature is on average between 42 and 44°C. The patient remains in the bath between 15 and 30 min. The essential difference between a water bath and a peat-slurry bath is that, in case of a water bath, the heat is transported very quickly to the body of the patient by convection. Thus, the sensation is very unpleasant. In a peat-slurry bath the heat is transported from particle to particle to the body of the patient, and therefore transport is much slower. In this way the amount of heat transferred to the body of the patient is 7-times more than in a water bath. Humic acids play an important role in heat transport. Figure 6 presents an electromicrograph of isolated humic acids in a weakly acidic medium. In acidic media the acidic groups are in hydrogen-exchanged form. Inter-and intramolecular hydrogen bonding gives rise to structures, which are roughly spherical in outline, and water is included in the matrix. Furthermore they can also be regarded as high molecular weight redox systems and this may influence many reactions on the skin. Because patients are sometimes reluctant to participate in experiments, there have been a number of investigations carried out with pigs (Kaemmeter, unpublished). Infrared photography of pigs after immersion in peat slurry-baths have shown that the heat is not evenly distributed. The heat can persist for prolonged periods in some regions. Changes in the rates of metabolism can take place in the hotter regions.
Fig. 6.
Purified humic acids in weak-acidic medium (electromicrograph).
PEAT HUMIC SUBSTANCES IN BALNEOLOGY
567
CONCLUSIONS The highly significant advances made in the studies of humic substances recently, as indicated by the publications o f the International Humic Substances Society, should provide the stimulus for in-depth investigations of the biochemical effects o f humic constituents. Although the results of biological applications using peat and humic substances are obvious, the evidence for cures and for improved health benefits is largely empirical up to now and will therefore need to be verified by more rigorous experimentation. Humic science has now reached the stage where meaningful results can be obtained about the benefits to balneology of humic substances from peats. REFERENCES Flaig, W., C. Goecke, and W. Kauffels, 1988. Moortherapie- Grundlagen und Anwendungen, Ueberreiter Wissenschaft, Wien, Berlin, pp. 1-308. Quecke, K., G. Loschen and C. Goecke, 1989. Zur Penetration von Huminstoffen durch die Scheidenhaut. In: H. Hornig (Ed.), Arbeitstagung des Arbeitskreises Gyn/ikologische Balneotherapie 1989, Vol. 33, Bad Waldsee, 7967 Bad Waldsee, pp. 162-165.