Process for extracting triterpene glycosides from botanical sources

The process includes obtaining a liquid extract from a fresh plant source material and mixing the extract with a solution saturated with at least one element having an oxidation number of one or two or combinations thereof. The resulting mixture provides for a solid precipitate material and a liquid portion containing the triterpene glycosides of which is then passed through a macroporous resin. The resin is then washed with an alcohol to obtain a solution thereof containing the triterpene glycosides. The solution is condensed to provide a purified liquid triterpene glycoside solution and then a drying step is performed to obtain a dry composition containing the triterpene glycosides.

BACKGROUND OF THE INVENTION 
The invention relates to a process for extracting triterpene glycosides 
from plant or botanical sources. 
Triterpene glycosides are non-caloric and are intensely sweet. For this 
reason, triterpene glycosides are very attractive for use as a sweetening 
agent in dietary and food industries. 
Plant or botanical sources exist for obtaining triterpene glycosides such 
as mogroside V. One particularly good sources of triterpene glycoside is 
cucurbitaceae fruit, fructus mormordicae or momordica grosvenori, which is 
also widely known as Lo Han Kuo. This plant itself is widely and popularly 
consumed as a food for a wide variety of health purposes such as stomach 
distress, sore throat, cough, diarrhea, constipation, etc. However, this 
fruit also contains bitter tasting compounds, which to date are not 
specifically identified to the knowledge of the present inventors, which 
interfere with use of the fruit or simple extract of the fruit as a 
sweetening agent. 
One laboratory extraction process was developed and published by Tsunematsu 
Takemoto et al. The Takemoto et al. process, however, is only applicable 
to roasted dry material from the fruit. In addition, the Takemoto et al. 
process is rather complicated, provides low yield, and is not practical or 
economical on an industrial scale. 
Another disclosed process is set forth in CN 1019935. In this process, 
fruit juice is obtained directly from momordica grosvenori, with no 
provision for removal of bitter-tasting materials. Thus, the process 
disclosed in CN 1019935 can only produce crude triterpene 
glycoside-containing material which also contains bitter components and 
which is not suitable for industrial scale manufacture or use as a 
sweetener. 
It is therefore the primary object of the present invention to provide a 
process whereby triterpene glycosides can be extracted from plant or 
botanical sources such as momordica grosvenori with a very high yield, and 
without including bitter-tasting components in the final product. 
It is a further object of the present invention to provide such process 
which is simple, efficient, consistent and economic. 
It is a still further object of the present invention to provide such a 
process which can be carried out using fresh fruit, thereby completely 
avoiding the need for fruit drying processes. 
It is another object of the present invention to provide such a process 
which does not involve the use of excessive amounts of organic or 
inorganic chemicals and the like. 
Other objects and advantages of the present invention will appear 
hereinbelow. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, the foregoing objects and 
advantages have been readily attained. 
According to the invention, a process is provided for obtaining triterpene 
glycosides from a plant source, which process comprises the steps of 
providing a plant source material containing triterpene glycosides, 
obtaining a liquid extract from said source material, said liquid extract 
containing said triterpene glycosides; mixing said liquid extract with a 
solution saturated with at least one element selected from the group 
consisting of elements having an oxidation number of two, elements having 
an oxidation number of one, and combinations thereof so as to provide a 
mixture; allowing said mixture to rest so as to provide a solid 
precipitate material and a liquid portion containing soluble portions of 
said liquid extract including said triterpene glycosides; passing said 
liquid portion through a column containing a neutral absorptive 
macroporous resin so as to absorb portions of said liquid portion 
including said triterpene glycosides onto said neutral absorptive 
macroporous resin; rinsing said column with an alcohol so as to obtain an 
alcohol solution containing said triterpene glycosides; condensing said 
alcohol solution so as to provide purified liquid triterpene glycoside 
solution; and drying said purified liquid triterpene glycoside solution so 
as to provide a dry composition containing said triterpene glycosides. 
The process is particularly advantageous when used with momordica 
grosvenori. The process provides an end product which is substantially 
free of bitter-tasting components and which contains a very high yield of 
the desired triterpene glycosides. The process is ideal for industrial 
scale use, and the end product is substantially free of insoluble 
components.

DETAILED DESCRIPTION 
The invention relates to a process for extracting triterpene glycosides 
from plant or botanical sources. The process advantageously provides for 
extraction of triterpene glycosides and separation of bitter-tasting 
components normally present in the plant source material. In addition, the 
process is simple, efficient and economical and is therefore ideally 
suited for use in manufacture on an industrial scale of triterpene 
glycosides which are extremely useful in the manufacture of non-caloric or 
low calorie sweeteners and a wide variety of food products. 
The invention is particularly well suited for use in extracting triterpene 
glycosides from plant members of the cucurbitaceae family (fructus 
mormordicae or momordica grosvenori) which is also widely known in Chinese 
as Lo Han Kuo. The following description of preferred embodiments of the 
invention will be presented in terms of momordica grosvenori. It should of 
course be noted, however, that other plant or botanical sources of 
triterpene glycosides could be used within the broad scope of the 
invention. 
Referring to the attached FIGURE, a schematic illustration of one 
embodiment of the process of the present invention is provided. 
The starting plant source material can advantageously be fresh plant 
matter, for example cut pieces of freshly harvested momordica grosvenori. 
The present invention provides excellent yield of triterpene glycoside, 
and 100 g of starting plant material can yield 1 g of highly pure 
triterpene glycoside. 
The fresh plant pieces are extracted by soaking in a bath of heated water, 
alcohol (preferably ethanol) or both. The initial extraction process is 
preferably carried out in hot, preferably boiling water. The FIGURE shows 
plant source material 10 being added to extraction bath 12, and a liquid 
extract exiting bath 12 which contains extracted triterpene glycosides as 
desired, and which also typically will include bitter-tasting components 
from plant source material 10. 
Extraction in bath 12 is preferably carried out several times for the 
initial starting material, each time saving the resulting liquid. For 
example, plant source material 10 can be boiled in a 1000 milliliter 
volume of extraction liquid, typically for a period of 1-3 hours. The 
resulting extract liquid is then preferably filtered through a suitable 
filter such as a 40 mesh stainless steel screen. The thus-obtained solid 
material can then be extracted again, for example this time using 800 
milliliters of boiling water, followed by filtering and two additional 
extractions each using 600 milliliters of boiling water. By collecting the 
liquid from filtering after each extraction, a total volume of about 3000 
milliliters of liquid extract containing the desired triterpene glycosides 
is provided. Of course, it may be preferable for a particular process to 
carry out more or less extraction steps, and different volumes of liquid 
could of course be used for each boiling or extraction step. 
Returning to the FIGURE, liquid extract 14 is then preferably mixed with 
saturated solution 16 which preferably contains one or more element having 
an oxidation number of one or two. The saturated solution is preferably a 
saturated solution of calcium (Ca++), sodium (Na+) potassium (K+) and 
mixtures thereof. Better results are provided if the saturated solution 
includes at least calcium, and it is most preferred that the saturated 
solution contain both calcium and sodium. 
For the preferred saturated solution including both calcium and sodium, it 
is further preferred that the saturated solution be provided having a 
ratio by volume of calcium saturated solution to sodium saturated solution 
of between about 1:1 and about 25:1, preferably between about 1:1 and 
about 5:1, and ideally about 3:1. 
Liquid extract 14 and saturated solution 16 are mixed thoroughly and 
introduced to a settling tank 18 where the mixture is allowed to 
precipitate, preferably for a period of at least about one-half hour, and 
more preferably for a period of at least about three hours. Solid 
precipitate material 20 resulting from this step is removed from tank 18 
and disposed of as desired, while the clarified liquid portion 22 is 
removed from tank 18 and contains triterpene glycoside for further 
processing in accordance with the present invention. 
Liquid portion 22 exiting settling tank 18 may have a basic or alkaline pH, 
which is not desirable in connection with the further processing steps of 
the present invention. Thus, it may be necessary to mix liquid portion 22 
with a non-toxic acid or acidic source 24, preferably in proportions 
suitable for providing the resulting mixture 26 with a pH of between about 
5.5 and about 7. 
Non-toxic acid 24 may suitably be any non-toxic acid which can be used to 
adjust the pH as desired. Examples of suitable acid include acetic acid, 
citric acid, HCl, H.sub.2 SO.sub.4 and the like. Acetic acid is 
particularly preferred because it is readily available and commonly 
acceptable for use in food products. This step is advantageous and 
desirable since the precipitating step using saturated solution of Ca++, 
Na+ and/or K+ results in a solution having a pH greater than 7 which is 
undesirable and would interfere with proper operation of the process of 
the present invention. 
In further accordance with the present invention, neutralized mixture 26 is 
then preferably passed to an absorptive affinity chromatography column 28 
preferably containing a neutral macroporous resin. During treatment in 
column 28, the desired triterpene glycosides are absorbed onto the resin 
in column 28, and a resulting liquid product 30 exiting column 28 is 
disposed of as desired. After liquid 30 is removed from column 28, column 
28 is then preferably rinsed using an alcohol solution 32 so as to remove 
absorbed triterpene glycosides from the resin in column 28 and provide a 
triterpene glycoside-containing alcohol solution 34 exiting column 28. 
Triterpene glycoside-containing alcohol solution 34 is then further 
treated in accordance with the process of the present invention as 
described below. 
Rinsing with alcohol solution 32 is preferably carried out using ethanol as 
the alcohol rinse. Further, it has been found in accordance with the 
present invention that a higher yield of rinsed triterpene glycosides is 
obtained if the alcohol rinsing is carried out in a plurality of steps or 
stages, and it is further preferred that the initial alcohol rinsing step 
or stage be carried out using an alcohol solution having a relatively low 
alcohol concentration, and that a gradually increasing alcohol 
concentration be used for each stage until the final stage having a 
relatively high alcohol concentration. For example, alcohol solutions may 
be used having an initial alcohol concentration of about 10 percent by 
volume, and are preferably gradually increased to a final alcohol 
concentration of about 95 percent by volume. Depending upon the number of 
rinsing steps to be used, it is preferable that the initial rinsing step 
be carried out using an alcohol solution having an alcohol concentration 
of less than or equal to about 70 percent by volume, and further that the 
final rinsing stage be carried out using an alcohol solution having a 
final alcohol concentration of at least about 95 percent by volume. 
In connection with the resin contained in column 28, any suitable neutral 
macroporous resin can be used. It is preferred that the resin have a 
surface area of between about 100 m.sup.2 /g and about 1000 m.sup.2 /g. 
Such resin is commercially available. 
Referring back to the FIGURE, triterpene glycoside-containing alcohol 
solution 34 is then preferably passed to a vacuum condenser 36 for 
condensing the initial volume of solution 34 to a reduced or condensed or 
concentrate volume 38 exiting condenser 36 which contains the desired 
triterpene glycosides. Condensed solution 38 is then preferably mixed with 
an additional volume 40 of alcohol to provide a concentrate-alcohol 
mixture which is preferably allowed to set so as to form a precipitate 
which is removed, and the remaining mixture is passed to drier 42 for a 
spray-drying step, preferably at a temperature of between about 50.degree. 
C. and about 150.degree. C., so as to provide a dry powder product which 
advantageously contains at least about 40% (wt) of triterpene glycosides, 
preferably at least about 60% triterpene glycosides, and most preferably 
at least about 80% triterpene glycosides. Further advantageously, the 
balance of the powder product is other carbohydrates and remaining plant 
matter, and is substantially free of the bitter-tasting components present 
in the earlier extract portions of the original plant source material. 
Thus, product 44 is ideally suited for use as an ingredient in various 
food products or in the manufacture of non-caloric sweeteners. 
Product 44 is also substantially free of water insoluble materials to allow 
for full dissolution of product 44 in liquid products as desired. 
Referring back to the FIGURE, it may be desirable to recycle the mixture 41 
of alcohol 40 and condensed liquid 38 for one or more additional 
condensing steps. This can assist in elevating the content of triterpene 
glycosides in the final product. 
It is also preferred that condensation be carried out in vacuum-condenser 
36 so as to reduce the volume of triterpene glycoside-containing solution, 
preferably to a reduced volume of about 1/20 of the original incoming 
liquid volume. Further, alcohol 40 is preferably added in the form of a 
95% ethanol alcohol solution. Alcohol 40 is preferably mixed with the 1/20 
condensed solution or reduced volume in a total volume having a ratio by 
volume of alcohol solution to condensed solution of between about 1:1 and 
about 25:1, preferably between about 1:1 and about 10:1 and ideally about 
5:1. It is also preferred that the additional alcohol solution 40 be added 
in separate discrete doses or dilutions, for example in separate doses 
each having substantially the same volume as the original 1/20 condensed 
solution. Thus, if the total alcohol solution to condensed solution ratio 
is 5:1, five equal doses of alcohol solution would preferably be used. 
It should be noted that one advantage in accordance with the present 
invention is that a large portion of the sticky, insoluble materials which 
normally accompany momordica grosvenori is eliminated before feed to the 
resin in column 28. This advantageously results in less difficulty due to 
gumming or fouling of the resin, and further leads to high yield and high 
purity of the product. As set forth above, the process of the present 
invention advantageously provides for a very high percentage of total 
triterpene glycoside in the final product, as well as a large percentage 
advantageously in the form of mogroside V, which is an excellent indicator 
of the total content of triterpene glycosides in the final product. For 
example, a 35% (wt) mogroside V content is indicative of a minimum 80% 
(wt) triterpene glycoside content, and the mogroside V content is easily 
measured to provide for quality control and the like in an industrial 
scale process. 
The dry composition of the process of the present invention is 
advantageously at least about 40 times sweeter per unit weight than 
refined sugar. 
Although the exact bitter-tasting components contained in the original 
plant source material 10 are not known to the inventors at this time, the 
process of the present invention does advantageously remove such 
bitter-tasting components and therefore advantageously provides the 
desired high yield and high quality triterpene glycoside in a process 
which is simple and efficient and therefore well suited to industrial 
scale use. 
EXAMPLE 
In this example, 100 grams of fresh Cucurbitaceae fruit was cut into pieces 
and boiled in 1000 ml of boiling water for 3 hours. The extract was 
filtered through a 40 mesh stainless steel screen to remove solids, and 
the liquid set aside. The separated solid was then extracted again using 
800 ml of water and then twice using 600 ml each to provide a total liquid 
extract of 3000 ml. To the 3000 ml was added 150 ml of Ca++ saturated 
solution and 50 ml of Na+ saturated solution, and the resulting mixture 
was mixed thoroughly and then set to precipitate. After about 0.5 hours, a 
solid had precipitated, and the clarified liquid carrying triterpene 
glycosides was separated from the settling tank. The liquid was mixed with 
acetic acid until it had a basic pH between 5.5 and 7, and the neutralized 
solution was then passed through an absorptive affinity chromatography 
column filled with 500 grams of neutral macroporous resin having a surface 
area of about 100-1000 m.sup.2 /g. The resin was then washed using 1500 ml 
of E--OH (ethanol) gradually increasing from a 10% vol concentration in 
the initial rinse to a 95% vol concentration in the final rinse. The 
collected liquid from the rinsing was then condensed to 1/20 of original 
volume using a vacuum condenser, and the condensed solution was then mixed 
with 5 separate volumes of 95% E--OH each equal to the volume of the 
original 1/20 condensed solution, and the mixture was set to precipitate 
E--OH insoluble materials. The clarified liquids were then filtered and 
vacuum-spray dried at 120.degree. C. to form approximately 1 gram of light 
yellow powder which was approximately 80% triterpene glycoside, and which 
was entirely free of bitter tasting components. 
This invention may be embodied in other forms or carried out in other ways 
without departing from the spirit or essential characteristics thereof. 
The present embodiment is therefore to be considered as in all respects 
illustrative and not restrictive, the scope of the invention being 
indicated by the appended claims, and all changes which come within the 
meaning and range of equivalency are intended to be embraced therein.