RESUMO
Direct acid hydrolysis of Dioscorea zingiberensis rhizomes for preparation of diosgenin is wildly used in the traditional industry， which uses a large amount of inorganic acid catalysts， with high wastewater discharge and serious environmental pollution. Therefore， exploring clean and efficient preparation methods and processes has become an inevitable choice to realize the sustainable development of industrial production of diosgenin. Herein， the author reviewed and analyzed the research progress and problems of enzymatic hydrolysis， microbial transformation and modified acid hydrolysis in the preparation of diosgenin from D. zingiberensis rhizomes during the last ten years， and their application prospects are analyzed. Enzymatic hydrolysis has mild reaction conditions， but the yield of diosgenin is low， the economic cost is high， and the purification process of active enzyme is complicated. Microorganism shows specific activity to the substrate and high efficiency for diosgenin production， and microbial transformation is clean and environmentally friendly， but microbial transformation is time-consuming and the metabolic intermediates are complicated. For the modified acid hydrolysis， two-phase acid hydrolysis can reduce the amount of acid catalyst， and sulfonic acid-functionalized ionic liquid displays good recyclable performance by replacing the traditional inorganic acid， however， the wastewater discharge should still be considered. Solid acid catalysts are non-corrosive and easy to be recycled， but the need to use ethanol as the reaction solvent has certain safety hazards， and the catalyst preparation process is cumbersome. In conclusion， exploring clean and efficient conversion methods is an important research trend for preparation of diosgenin from D. zingiberensis rhizomes. For the enzymatic hydrolysis， the key glycoside hydrolases in the bioconversion process should be explored in depth， the conversion pathway of enzymatic saponins and enzyme specificity should be fully elucidated， and efforts should be made to improve the efficiency of enzymatic hydrolysis. For the microbial transformation， we should accelerate its industrial application process based on selecting and breeding efficient transformation strains， and optimizing stable transformation systems and processes， and in-depth investigation of the mechanism of microbial transformation， fully elucidating the specific key hydrolases and its catalytic properties， and striving to improve the efficiency of microbial transformation. For the modified acid hydrolysis， novel acid catalytic system with simple structure， stable performance and good biodegradability should be explored and applied， which can effectively solve the problems of environmental pollution and production safety.
RESUMO
Currently, the second-generation intact parathyroid hormone (iPTH) assay is commonly used for measuring PTH levels. The iPTH assay detects both full-length (1-84)PTH and (7-84)PTH fragments, which have antagonistic effects on (1-84)PTH in bones and kidneys. The third-generation PTH assay is specific for (1-84)PTH. This study examined the features of different PTH fragments in stage 5 chronic kidney disease (CKD) and the effects of parathyroidectomy (PTX) on the above markers in severe secondary hyperparathyroidism (SHPT) patients. The cross-sectional study included 262 stage 5 CKD patients and 90 controls. A prospective follow-up study was then conducted in 34 PTX patients. Second- and third-generation assays were used to measure plasma iPTH and (1-84)PTH levels, respectively. Circulating (7-84)PTH levels were calculated by subtracting the (1-84)PTH value from the iPTH value. Different plasma PTH fragments were higher, and (1-84)PTH/iPTH was lower in CKD patients than in controls. Plasma (1-84)PTH and (7-84)PTH concentrations increased as iPTH levels increased, and (7-84)PTH increased more evidently. Plasma iPTH, (1-84)PTH and (7-84)PTH levels were 1530.5 (885.0-2111.5) pg/ml, 683.1 (431.4-1018.0) pg/ml, and 739.3 (452.6-1261.0) pg/ml, respectively, in PTX patients. Plasma iPTH, (1-84)PTH and (7-84)PTH concentrations decreased considerably, and the (1-84)PTH/iPTH ratio increased after PTX (median follow-up interval: 10.9 months). Stage 5 CKD patients had higher plasma levels of different PTH fragments, and lower (1-84)PTH/iPTH ratio. PTX could significantly reverse these abnormalities in severe SHPT patients. The iPTH assay overestimated the function of the parathyroid glands; thus, the third-generation PTH assay is likely better for the management of CKD patients.
