Separation and purification of amygdalin from thinned bayberry kernels by macroporous adsorption resins

Encapsulation of Benzaldehyde Produced by the Eco-Friendly Degradation of Amygdalin in the Apricot Kernel Debitterizing Wastewater

In order to fully utilize the by-products of apricot kernel-debitterizing and address the chemical instability of benzaldehyde in the food industry, benzaldehyde was first prepared by adding the apricot kernel powder to degrade the amygdalin present in the apricot kernel-debitterizing water. Subsequently, β-cyclodextrin was employed to encapsulate the benzaldehyde, and its encapsulation efficacy was evaluated through various techniques including Fourier transform infrared spectroscopy, thermogravimetric analysis, release kinetics fitting inhibitory effect and the effect on Botrytis cinerea. Finally, the encapsulation was explored via molecular docking and molecular dynamics simulations. The results indicate that the optimal preparation conditions for the benzaldehyde were 1.8 h, 53 °C and pH 5.8, and the encapsulation of benzaldehyde with β-cyclodextrin (wall-core ratio of 5:1, mL/g) has been verified by the deceleration in the release rate, the enhanced thermal stability and the prolonged inhibition effect against Botrytis cinerea. The encapsulation proceeded spontaneously without steric hindrance in the simulation, which led to a reduction in the hydrophobic cavity of β-cyclodextrin. In conclusion, the amygdalin in the debitterizing wastewater can be degraded in an eco-friendly way to produce benzaldehyde by adding apricot kernel powder, which contains β-glucosidase; the encapsulation of benzaldehyde is stable, thus enhancing the utilization of amygdalin in the debitterizing wastewater of apricot kernels.

Adsorption Characteristics and Enrichment of Emodin from Marine-Derived Aspergillus flavipes HN4-13 Extract by Macroporous Resin XAD-16

Emodin, a hydroxyanthraquinone derivative, has been used as medicine for more than 2000 years due to its extensive pharmacological activities. Large-scale production of emodin has been achieved by optimizing the fermentation conditions of marine-derived Aspergillus flavus HN4-13 in a previous study. However, the fermentation broth contained complex unknown components, which adversely affected the study of emodin. Herein, the conditions for the enrichment of emodin from A. flavipes HN4-13 extract using XAD-16 resin were optimized, and a separation method with high efficiency, simple operation, a low cost, and a large preparative scale was established. The adsorption process of emodin on the XAD-16 resin conformed to pseudo-second-order kinetics and Langmuir models. The optimal conditions for the adsorption process were as follows: An emodin concentration, flow rate, and loading volume of 0.112 mg/mL, 2 BV/h, and 10 BV, respectively. For desorption, 50% ethanol was used to elute impurities and 80% ethanol was used to desorb emodin. After enrichment with XAD-16 resin, the emodin content increased from 1.16% to 11.48%, and the recovery rate was 75.53% after one-step treatment. These results demonstrate the efficiency of the simple adsorption–desorption strategy, using the XAD-16 resin for emodin enrichment.

Amygdalin: Toxicity, Anticancer Activity and Analytical Procedures for Its Determination in Plant Seeds

Amygdalin (d-Mandelonitrile 6-O-β-d-glucosido-β-d-glucoside) is a natural cyanogenic glycoside occurring in the seeds of some edible plants, such as bitter almonds and peaches. It is a medically interesting but controversial compound as it has anticancer activity on one hand and can be toxic via enzymatic degradation and production of hydrogen cyanide on the other hand. Despite numerous contributions on cancer cell lines, the clinical evidence for the anticancer activity of amygdalin is not fully confirmed. Moreover, high dose exposures to amygdalin can produce cyanide toxicity. The aim of this review is to present the current state of knowledge on the sources, toxicity and anticancer properties of amygdalin, and analytical methods for its determination in plant seeds.

Isolation and identification of putative precursors of the volatile sulfur compounds and their inhibition methods in heat-sterilized melon juices

Volatile sulfur compounds, such as dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide, cause the off-flavor in heat-sterilized juices and limit the commercial production of juices. In this study, we investigated the precursors for these volatile sulfur compounds and analyzed the potential inhibition methods. Upon separation of melon juice components using resin column, the dimethyl sulfide precursor was present in the acidic fraction whereas the dimethyl trisulfide precursor was present in neutral and acidic fractions. Exogenous addition experiments indicated S-methyl methionine was the precursor of dimethyl sulfide, and methionine was the precursor of dimethyl disulfide and dimethyl trisulfide. The release of volatile sulfur compounds was reduced by decreasing the pH to 2.0, or by adding epicatechin. We concluded S-methyl methionine and methionine were degraded into volatile sulfur compounds through nucleophilic substitution and Strecker degradation. This study can help establishing protocols for controlling the release of volatile sulfur compounds in heat-sterilized juices.

Separation of Glycyrrhizic Acid and Its Derivants from Hydrolyzation in Subcritical Water by Macroporous Resin

Glycyrrhizic acid (GL) and its derivants, glycyrrhetinic acid 3-O-mono-β-d-glucuronide (GAMG) and glycyrrhetinic acid (GA) hydrolyzed in subcritical water, are bioactive substances and edulcorators. In this work, a separation strategy for these three substances was established. The effects of adsorbent and eluent were investigated by static/dynamic adsorption and multi-stage desorption with the mechanism analysis. The adsorption of them onto EXA50 resin was well fitted by the pseudo second-order kinetic model. The optimal dynamic adsorption flow rate was 6 bed volume (BV)/h, and water of pH = 12 was used to elute GL at 4 BV/h, then n-buthanol was used subsequently to elute GA at 1 BV/h, and finally 90% ethanol was applied to elute GAMG at 2 BV/h. As a result, purities of these compounds increased, which demonstrated that this adsorption-desorption technology was simple and efficient, and indicated the potential for large-scale purification and preparation of GL and its derivants in the future.

Separation and determination of amygdalin and unnatural neoamygdalin in natural food supplements by HPLC-DAD

This work is focused on separation and determination of amygdalin and its unnatural form neoamygdalin in natural food supplements. Reversed-phase high-performance liquid chromatography with a high-stability silica-based column with C₁₈ functional group has been used for solving this problem. The effect of the mobile phase composition as well as the column temperature on the separation of the amygdalin epimers has been investigated. Isocratic elution using a mobile phase composed of 0.05% aqueous formic acid and acetonitrile achieved the required separation within 17 min. Under optimum chromatographic conditions, the developed method was validated and was applied for the determination of amygdalin epimers in natural food supplements containing apricot or peach kernels. A simple extraction method using methanol as an extractant supported by an ultrasonic bath was used with recovery in the range of 94.8% to 104.3%. The limit of detection and limit of quantification values for R-amygdalin were 0.13 mg/L and 0.40 mg/L, respectively. The developed method proved to be precise with the intra-day and inter-day relative standard deviation values less than 2.23%.

Recovery of lotus (Nelumbo nucifera Gaertn.) seedpod flavonoids using polar macroporous resins: The updated understanding on adsorption/desorption mechanisms and the involved intermolecular attractions and bonding

Macroporous resins have been employed in the effective recovery of flavonoids from plants. In this study, S8 polar resins were used to recover flavonoids and procyanidins from lotus seedpods. Adsorption kinetics, isotherms, and thermodynamics studies revealed that the adsorption process involved physico-chemical interactions, including flavonoid-resin and flavonoid-flavonoid electrostatic interactions, π-π aromatic stacking, moderate and strong hydrogen bonding, and repulsive forces. These forces worked complementarily in adsorption, except for the repulsive force, which opposed the adsorption. Further, adsorption temperature determined the adsorption behavior, with multilayer adsorption enhancing adsorption capacity. In dynamic desorption tests, an acetone/water/acetic acid mixture (58.77: 39.34: 1.89) designed by the D-optimal design method was able to desorb 95.57% and 89.85% of total flavonoids and procyanidins, respectively, using less than two bed volumes of solvent. Ultra-performance liquid chromatography triple-time of flight/mass spectrometry (UPLC-TOF/MS) analysis showed that 26 flavonoids, including 5 procyanidins, were detected after the recovery.

Purification of Amygdalin from the Concentrated Debitterizing-Water of Apricot Kernelsusing XDA-1 Resin

In this study, six macroporous resins were screened on their adsorption and de-adsorption characteristics for the amygdalin in the debitterizing wastewater concentrate (DWC). The results indicate that the XDA-1 resin exerts good adsorption and de-adsorption capacities on the amygdalin. In order to further confirm its feasibility, the factors affecting the capacity of adsorption and de-adsorption, and its adsorption mechanisms were also investigated. The results suggest that the optimum purification conditions were as follows: loading concentration of samples with 78.05 mg/mL, flow rate of 2 mL/min, and de-adsorption with 80% ethanol solution. The recovery rate was 88.75% and the relative content achieved 61.58% after purification by XDA-1 resin. The Freundlich model can be used to describe the entirety of the exothermic and physical adsorption processes. In summary, the conclusion which can be made from this research is that the wastewater generated from the debitterizing of apricot kernels can be well treated by resin to recycle the amygdalin and reduce its pollution to environment.

Highly selective separation and purification of chicoric acid from Echinacea purpurea by quality control methods in macroporous adsorption resin column chromatography

Chicoric acid is the main phenolic active ingredient in Echinacea purpurea (Asteraceae), best known for its immune-enhancing ability, as well as used as a herbal medicine. To achieve further utilization of medicinal ingredients from E. purpurea, an efficient preparative separation of chicoric acid was developed based on macroporous adsorption resin chromatography. The separation characteristics of several different typical macroporous adsorption resins were evaluated by adsorption/desorption column experiments, and HPD100 was revealed as the optimal one, which exhibited that the adsorbents fitted well to the pseudo-second-order kinetics model and Langmuir isotherm model, and the optimal process parameters were obtained. The breakthrough curves could be predicted and end-point could be determined early. Besides, the optimal elution conditions of chicoric acid can be achieved using the quality control methods. As a result, the purity of chicoric acid was increased 15.8-fold (from 4 to 63%) after the treatment with HPD100. The process of the enrichment and separation of chicoric acid is considerate, because of its high efficiency and simple operation. The established separation and purification method of chicoric acid is expected to be valuable for further utilization of E. purpurea according to product application in pharmaceutical fields in the future.

Fractionation using adsorptive macroporous resin HPD-600 enhances antioxidant activity of Gnetum gnemon L. seed hard shell extract

In this study, antioxidant activities and identification of the bioactive substances in Gnetum gnemon L. (Gg) seed hard shell were evaluated. The seed of Gnetum gnemon L., an Indonesian native plant, is commonly consumed as a vegetable or further processed as cracker. Isolated substances from Gnetum gnemon seed are mainly stilbenoid derivatives which show potent antioxidant, tyrosinase inhibitor, and antimicrobial activities. Nevertheless, the antioxidant activity of its crude extract is still considered weak. In this study, an effort was made to improve antioxidant potency by fractionation using macroporous adsorptive resin (MAR). This fractionation successfully enhanced antioxidant activity of red Gg seed hard shell extract with efficient adsorption contact time within 30 min. Antioxidant activity of fractions 25-75% v/v ethanol increased three- to sevenfold as compared to crude extract and more importantly resulted in dry product which was easier for further processes. Identification of bioactive compounds in Gg seed hard shell extract with different degrees of ripeness was also performed by HPLC and confirmed the presence of Gnetin C, resveratrol, and other stilbenoid derivatives. These other stilbenoid derivatives could be the main substances contributing in antioxidant action with lower IC₅₀ as compared to both Gnetin C and resveratrol. In summary, fractionation process using MAR HPD-600 reduced unnecessary sugar molecules from red Gg seed hard shell extract hence resulting to fraction with strong antioxidant activity.

Zeolitic imidazolate framework 8 (ZIF-8) reinforced macroporous resin D101 for selective solid-phase extraction of 1-naphthol and 2-naphthol from phenol compounds

Macroporous resin has been attracting intensive attention due to its critical role in separation and purification of natural products. Herein, a zeolitic imidazolate framework 8 reinforced macroporous resin D101 was prepared via a room temperature growth method and used for dispersive SPE of 1-naphthol and 2-naphthol. The parameters affecting the adsorption and desorption efficiency such as the sample pH, adsorbent amount, extraction time, desorption solvent, and desorption time were investigated. The as-prepared adsorbent showed selectivity for 1-naphthol and 2-naphthol compared to other phenols. Under the optimum dispersive SPE conditions, the detection of 1-naphthol and 2-naphthol coupled with a CZE method was conducted and the LODs for 1-naphthol and 2-naphthol were 1.37 and 1.43 ng/mL, respectively. Moreover, the results of urine sample analysis showed the spiked recoveries to be in the range of 96.2-106.9%. This study indicated that D101@ZIF-8 (where ZIF is zeolitic imidazolate framework) is a promising selective adsorbent for the analysis of 1-naphthol and 2-naphthol in urine samples.

Problems and Pitfalls in the Analysis of Amygdalin and Its Epimer

α-[(6-O-β-d-Glucopyranosyl-β-d-glucopyranosyl)oxy]-(αR)-benzeneacetonitrile, or R-amygdalin, is the most common cyanogenic glycoside found in seeds and kernels of the Rosaceae family and other plant genera such as Passiflora. Many commercially important seeds are analyzed for amygdalin content. In "alternative medicine", amygdalin has been sold as a treatment for cancer for several decades without any rigorous scientific support for its efficacy. We have found that there are some inconsistencies and possible problems in the published analytical chemistry of amygdalin. It is shown that some analytical approaches do not account for the presence of the S-isomer; therefore, a fast reliable method was developed using a chiral stationary phase and HPLC. This approach allows "real-time" monitoring and complete and highly efficient separations. It is found that the S-amygdalin continuously forms in aqueous solutions. A striking result is that the conversion of amygdalin is glassware dependent. "Clean" vials from various vendors can show drastically different reaction rates of the conversion to the isomer (S-amygdalin, also called neo-amygdalin). The epimerization kinetics are dependent on the solvent, temperature, pH, and the nature of the container. For example, epimerization in water was complete in <15 min in a new glass vial taken from the box, whereas it can take >1 h in specially cleaned glassware. Conversely, epimerization can be significantly delayed at high temperature if high-density polyethylene is used as the container. Hence, inert plastic containers are recommended for storage of aqueous amygdalin solutions. Commercial preparations of R-amygdalin actually contain greater quantities of S-amygdalin and ∼ 5% of other degradation products.