Introduction
The ginseng saponin (ginsenoside) is one of the most important secondary metabolites in ginseng and hasvarious pharmacological activities. To date about 38 kinds of ginsenosides have been isolated and identified from Panax ginseng C. A. Meyer. Among these ginsenosides, Rg3 is a precursor for ginsenoside Rh2, which has a very strong antitumor effect. and has many pharmaceutical activities. However, Rg3 is extremely low in normal ginseng. Thus production of ginsenoside Rg3 would be very important and many studies have aimed to convert major ginsenosides to the more active minor ginsenoside Rg3. The enzymatic conversion through sugar hydrolysis at a specific position is desirable for the production of active minor ginsenoside Rg3.
Material and Method
The isolation of β-glucosidase-producing microorganisms was performed according to a previously published method. Each microbialsuspension cultured in nutrient broth was added to the same volume of 1 mM ginsenoside Rb1 solution and then incubated on a rotary shaker at 30°C for 48 h. The reaction mixture was extracted with butanol saturated with H2O and then analyzed by thin layer chromatography (TLC). 8 μl of the ginseng extract solution was spotted on a TLC plate and developed to 5.5 cm distance in a chamber with chloroform/methanol/water as the mobile phase. Bands on the TLC plates were detected by spraying 10% H2SO4, followed by heating.
Result and Discussion
Ginseng(the root of Panax ginseng C. A. Meyer, Araliaceae) is frequently used as a crude substance taken orally in Korea, China and Japan, as well as other Asian countries, as a traditional medicine. Ginsenosides are the principal components having pharmacological and biological activities. More than 38 different ginsenosides so far have been isolated and identified from ginseng saponins. Among them, deglycosylated ginsenosides are known to be more effective in vivo physiological action and to act as active compounds. A lactic acid bacteria, which have β-glucosidase activity, were isolated from soil and kimchi using a MRS-Esculin agar. These strains were identified on the basis of phylogenetic inference based on 16S rDNA sequences. TLC and HPLC were used to analysis transformed ginsenosides. Ginsenosides are main pharmacoactive component in ginseng. When ginseng was orally administered, the absorption of ginsenosides from the gastrointestinal tract are extremely low. In order to improve oral bioavailability, transforming major ginsenosides into more active minor ginsenoside is very important. Caulobacter leidyia GP45 and Micro- bacterium esteraromaticum GS514 were isolated from ginseng field for converting major ginsenosides into minor ginsenosides. In the co-culture of strain GP45 and GS514 with ginsenoside Rb1, produced compound K and ginsenoside Rg3 individually. The transformation pathway of ginsenoside Rb1 were confirmed Rb1⟶Rd⟶F2⟶compound K and Rb1⟶Rd⟶Rg3.
고기능성 홍삼사포닌성분의 함량을 증대시키기 위한 목적으로 홍삼엑스에 열처리, 산(acid)처리하여 그 가능성을 조사하였다. 산도를 조정하지 않은 무처리구(control, pH 4.4)에 120℃ 열처리한 경우 ginsenoside-Rg3의 함량이 약 2배 정도 증가였다. 구연산으로 pH 2.0으로 조정하고 온도처리한 처리구에서는 2.8배나 많은 ginsenoside-Rg3 성분이 증가하였으나 다른 유효한 사포닌의 파괴가 두드러져 처음 홍삼엑스에 함유되어 있던 총사포닌의 65% 정도가 소실되었다. 80℃에서 12시간 처리를 한 경우에는 pH를 2.5와 2.0로 조정한 처리구에서는 11.20 mg과 12.50 mg으로 홍삼엑스의 3.3 mg보다 3.3배 이상 ginsenoside-Rg3 성분이 변환되었다. Ginsenoside-Rb1, Rb2, Rc, Re, Rg1의 함량이 산도가 높아짐에 따라서 급격히 소실되었고 홍삼 특이성분(ginsenoside-Rg3, RH2, Rh1)의 함량은 현저히 증가되었다. 매실엑스로 pH를 2.5로 조정한 처리구에서는 13.34 mg으로 홍삼엑스의 3.3 mg보다 4배 이상 변환된 것으로 분석되었다. 비록 31%정도의 total saponin의 감소가 있었으나 120℃의 고온처리에서 처럼 다른 유효한 사포닌의 큰 손실 없이 60℃에 12시간 처리하는 것만으로도 다량의 ginsenoside-Rg3를 생산하는 것을 확인하였다.