Thermal Control Using Far-Infrared Irradiation for Producing Deglycosylated Bioactive Compounds from Korean Ginseng Leaves.

Although ginseng leaf is a good source of health-beneficial phytochemicals, such as polyphenols and ginsenosides, few studies have focused on the variation in compounds and bioactivities during leaf thermal processing. The efficiency of far-infrared irradiation (FIR) between 160 °C and 200 °C on the deglycosylation of bioactive compounds in ginseng leaves was analyzed. FIR treatment significantly increased the total polyphenol content (TPC) and kaempferol production from panasenoside conversion. The highest content or conversion ratio was observed at 180 °C (FIR-180). Major ginsenoside contents gradually decreased as the FIR temperature increased, while minor ginsenoside contents significantly increased. FIR exhibited high efficiency to produce dehydrated minor ginsenosides, of which F4, Rg6, Rh4, Rk3, Rk1, and Rg5 increased to their highest levels at FIR-190, by 278-, 149-, 176-, 275-, 64-, and 81-fold, respectively. Moreover, significantly increased antioxidant activities were also observed in FIR-treated leaves, particularly FIR-180, mainly due to the breakage of phenolic polymers to release antioxidants. These results suggest that FIR treatment is a rapid and efficient processing method for producing various health-beneficial bioactive compounds from ginseng leaves. After 30 min of treatment without leaf burning, FIR-190 was the optimum temperature for producing minor ginsenosides, whereas FIR-180 was the optimum temperature for producing polyphenols and kaempferol. In addition, the results suggested that the antioxidant benefits of ginseng leaves are mainly due to polyphenols rather than ginsenosides.

[Effects of shading on key enzyme genesexpression and accumulation of saponins in Panax japonicus var. major].

To explore the effects of shading and the expression of key enzyme genes on the synthesis and accumulation of Panax japonicus var. major saponins, different shading treatments (0%, 30%,50%) of potted P. japonicus var. major were used as test materials, the expression of three key enzyme genes(CAS,DS,ß-AS) of leaves and rhizomes in different growth periods of P. japonicus var. major was determined by real-time quantitative PCR, the content of total saponins was determined by ultraviolet spectrophotometry. The results indicated that, in flowering stage, CAS,DS,ß-AS were highly expressed in the aerial parts of P. japonicus var. major, 30% shading treatment significantly inhibited the expression of CAS in leaves and promoted the expression of DS and ß-AS in stems, leaves and flowers, it was speculated that the main part of saponin synthesis was leaf in this stage. Both the expression levels of DS and ß-AS and changes in the content of total saponins in leaves showed a tendency of low-high-low throughout the growth cycle, correlation coefficient analysis showed that there was a positive correlation between them. Compared with control, the expression levels of DS and ß-AS and the content of total saponins were greatly enhanced under shading treatment, 30% shading treatment significantly promoted the accumulation of total saponins. Therefore, it is suggested that 30% shading treatment should be applied to the artificial cultivation of P. japonicus var. major, which is beneficial to the accumulation and quality improvement of saponins.

Chlorophyll fluorescence imaging as a tool to monitor the progress of a root pathogen in a perennial plant.

MAIN CONCLUSION: The chlorophyll fluorescence parameter ΦNO is an excellent metric for the non-destructive monitoring of disease progression, measured over a broad range of light intensities. The suitability of the slow induction chlorophyll fluorescence parameters ΦPSII, ΦNPQ, and ΦNO to monitor in vivo disease progression in a host-root pathogen pathosystem was evaluated and compared to the established method of monitoring disease by measuring Fv/Fm. Using the infection of ginseng plants (Panax quinquefolius L.) with Pythium irregulare Buisman as a model, light response curves were used to establish the optimal irradiance for the resolution of differences between fluorescence parameters ΦPSII, ΦNPQ and ΦNO. As infection progressed only changes in ΦNO remained consistent with increased irradiance, and increased as infection progressed. Furthermore, ΦNO showed a high sensitivity for distinguishing increased disease load. In contrast, the magnitude in change of ΦPSII and ΦNPQ were sensitive to irradiance levels. The magnitude of increase in ΦNO per unit disease score was equivalent to the corresponding decline in Fv/Fm values. Thus ΦNO is as sensitive as Fv/Fm in monitoring biotic stress. The ability to measure ΦNO under a wide range of light intensities, including natural light, potentially without the need for dark adaptation, means that it can be used in the development of a general protocol for non-invasive, in vivo monitoring of plant health, from the laboratory to the field scale.

[Effect of salicylic acid on photosynthesis, physio-biochemistry and quality of Panax ginseng under full sun shine in spring].

In order to search for a new pathway to improve the yield of ginseng through growing at the full sun shine accompanied by salicylic acid (SA), the net photosynthetic rate (P(n)), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), malondialdehyde (MDA) in Panax ginseng leaves, and the content of ginsenosides in roots were compared under various concentrations of SA and full sun shine with the traditional shade shed. Under the full sun shine, 0.05, 0.2 mmol x L(-1) SA increased net photosynthetic rate to a great extent. Under the cloudy day, the average net photosynthetic rate increased by 127.8% and 155.0% over the traditional shade shed, 13.9% and 27.5% over the treatment without SA respectively; under the clear day, 23.5% and 30.4% over the traditional shade shed, 8.6% and 14.6% over the treatment without SA, particularly obvious in the morning and late afternoon. With such concentration, SA increased activities of SOD, CAT, POD, and decreased the contents of the MDA. This difference resulted from different light intensity, rise of light saturation point, and fall of compensation point. Full sun shine decreased ginsenosides contents, but with SA, the ginsenosides regained, the content of Rg1 and Re, Rb1, total six types of ginsenosides in SA 0.2 mmol x L(-1) group were higher than those in the control group (P < 0.05) and other groups. The application of 0.2 mmol x L(-1) SA under full sun shine during a short time has little threat to the P. ginseng in spring, and could enhance the resistance to the adversity, which would improve the yield of ginseng heavily.

Application of gamma irradiation in ginseng for both photodegradation of pesticide pentachloronitrobenzene and microbial decontamination.

This study investigates the feasibility of using gamma irradiation for photodegradation of a common residual fungicide, pentachloronitrobenzene (PCNB), in ginseng, and for microbial decontamination. American ginseng, Panax quinquefolius, was subjected to gamma irradiation. PCNB residues were analyzed by gas chromatography with electron capture detection and mass spectrometry. Eighty percent of PCNB (100 ppm) in a methanol aqueous solution was degraded by 5 kGy irradiation, and the primary degradation product was pentachloroaniline. Furthermore, contaminated PCNB (3.7 ppm) in ginseng were reduced to 0.2 ppm after 20 kGy irradiation. The IC(50) for treatment of Sclerotium rolfsii with 20 kGy irradiated PCNB was about 2.7 times higher than that for treatment with unirradiated PCNB. The survival rate of mouse fibroblast L929 cells treated with 20 kGy irradiated PCNB was about 12.9% higher than that of L929 cells treated with unirradiated PCNB. Additionally, after 20 kGy irradiation, less than 5% reduction of contents of ginsenoside Rb1 and Re were observed, and amounts of ginsenosides Rc, Rd, and Rg1 were not reduced significantly. The minimal gamma dose for microbial decontamination was 10 kGy. Therefore, gamma irradiation can be used for both PCNB photodegradation and microbial decontamination of ginseng without obvious loses of ginsenoside contents.

Porosity changes and retention of ginsenosides in North American ginseng root using different dehydration processes.

Air drying (AD), freeze-drying (FD), and vacuum-microwave drying (VMD) were applied to fresh North American ginseng roots to evaluate the effect of different drying techniques on pore characteristics and the subsequent recovery of ginsenoside content. FD ginseng root produced the lowest reductions in both total moisture content and water activity (P < 0.05), with no differences noted between Ontario or British Columbia ginseng. Ginseng roots from Ontario and British Columbia sources were therefore pooled to conduct the root porosity and ginsenoside measurements. Among samples, FD ginseng obtained the highest total porosity followed by VMD and AD, respectively (P < 0.05). All dehydrated samples had a porous structure with sizes that ranged from 0.002 µm to 172 µm, dominated by macropores (>1.5 µm). Pore characteristics of dried ginseng root were shown to affect recovery of ginsenosides, with the general trend being an increase in total porosity resulting in an increase in total ginsenoside recovered. High performance liquid chromatography results obtained on specific ginsenosides showed that AD of ginseng root resulted in the lowest recovery of total ginsenosides, most notably, Rg1 and Rb1, followed by VMD and FD, respectively. There was no specific difference in total ginsenoside recovery from roots dried at increasing power of VMD.

Electron beam irradiation improves shelf lives of Korean ginseng (Panax ginseng C.A. Meyer) and red ginseng.

Effect of electron beam irradiation on microbial growth and qualities of vacuum-packaged Korean ginseng and red ginseng during storage was investigated. Korean ginseng and red ginseng were treated at irradiation doses of 0, 2, 8, and 16 kGy. After treatment, samples were individually vacuum-packaged and stored at 20 degrees C. Microbial growth results of the irradiated samples presented that populations of total bacteria, yeast and mold, and total coliforms were decreased by 2 to 3 log CFU/g. The pH values of the samples were not significantly different among treatments. Thiobarbituric acid-reactive substance values of the samples increased during storage. Electron beam treatment caused negligible changes in Hunter's color L, a, and b values among the samples. Sensory evaluations like color and odor of the samples exhibited that there were no significant changes among the samples. During storage, content of saponin, a leading compound in ginseng, was not affected by irradiation. These results suggest that electron beam treatment should be useful in extending shelf lives of Korean ginseng and red ginseng.

An electron spin resonance study of gamma-ray irradiated ginseng.

Using electron spin resonance (ESR) spectroscopy, we revealed the presence of four radical species in gamma-ray irradiated ginseng (Agaliaceae). Before irradiation, the representative ESR spectrum of ginseng is composed of a sextet centered at g = 2.0, a sharp singlet at the same g-value, and a singlet at about g = 4.0. The first one is attributable to a hyperfine (hf) signal of Mn2+ ion (hf constant: 7.4 mT). The second one is due to an organic free radical. The third one is originated from Fe3+. Upon gamma-ray irradiation, a new ESR (the fourth) signal was detectable in the vicinity of g = 2.0 region. The progressive saturation behaviors of the ESR signals at various microwave power levels were indicative of different relaxation time for those radicals. The anisotropic ESR spectra were detected by the angular rotation of the sample tube. This is due to the existence of anisotropic microcrystalline in the ginseng powder sample.

Decreased Hill reaction rates and slow turnover of transitory starch in the obligate shade plant Panax quinquefolius L. (American ginseng).

To identify physiological processes that might limit photosynthesis in Panax quinquefolius L. (American ginseng) a comparison has been made with Panax ginseng C.A. Meyer (Korean ginseng), Pisum sativum L. (pea) and Spinacia oleracea L. (spinach). The quantum yield of oxygen evolution in intact leaves and isolated thylakoid membranes was found to be smaller in ginseng than in pea or spinach. However, the number of photosystem II (PSII) centers on a chlorophyll basis was found to be similar in all species. This suggests that ginseng thylakoid membranes possess relatively more inactive PSII centers than thylakoids of pea and spinach when grown under similar conditions. Unexpectedly, whole-chain electron transport from water to methyl viologen, and partial photosystem I reactions, demonstrated that electron transport rates to methyl viologen were anomalously low in P. quinquefolius and P. ginseng. Additionally, at elevated light intensities, intact leaves of P. quinquefolius were more susceptible to lipid peroxidation than pea leaves. In plants grown at a light intensity of 80 micro mol photons m(-2) s(-1) the levels of fructose and starch were higher in both ginseng species than in pea or spinach. Significantly, the level of starch in P. quinquefolius was relatively constant throughout the entire 12 h/12 h light/dark cycle and remained high after an extended dark time of 48 h. In addition, P. quinquefolius had lower activities of alpha-amylase and beta-amylase than P. ginseng, pea and Arabidopsis thaliana (L.) Heynh. The significance of the elevated levels of leaf starch in P. quinquefolius remains to be determined. However, the susceptibility of P. quinquefolius to photoinhibition may arise as a consequence of a reduced fraction of active PSII centers. This may result in the normal dissipative mechanisms in these plants becoming saturated at elevated, but moderate, light intensities.

Degradation of ginsenosides in American ginseng (Panax quinquefolium) extracts during microwave and conventional heating.

The degradation of ginsenosides in American ginseng (Panax quinquefolium) extracts during microwave and water (oil) bath heating (conventional heating) was investigated. Both the 50% ethanol-water extracts and the aqueous extracts were boiled in a modified laboratory microwave oven and in a water (or oil) bath, respectively. The neutral ginsenosides (Rb(1), Rc, Rd, and Re) and malonyl ginsenosides (m-Rb(1), m-Rc, and m-Rd) were determined by reverse-phase high-performance liquid chromatography. The results showed that the degradation of ginsenosides in 50% ethanol-water extracts was a first-order reaction. The malonyl ginsenosides were much less stable than the corresponding neutral ginsenosides, with the rate constant value of the malonyl ginsenosides being 3-60 times that of the neutral ginsenosides. At the same temperature, the effect of microwave heating on the degradation of ginsenosides was the same as that of conventional heating.