Production of diosgenin from yellow ginger (Dioscorea zingiberensis C. H. Wright) saponins by commercial cellulase

An overview on pharmacological significance, phytochemical potential, traditional importance and conservation strategies of Dioscorea deltoidea: A high valued endangered medicinal plant

Dioscorea deltoidea Wall. ex Griseb. is an endangered species of the Dioscoreaceae family. It is the most commonly consumed wild species as a vegetable due to its high protein, vital amino acid, vitamin, and mineral content. There are approximately 613 species in the genus Dioscorea Plum. ex L., which is found in temperate and tropical climates. Dioscorea deltoidea, a plant species widespread across tropical and sub-tropical regions, called by different names in different languages. In English, it is commonly referred to as "Wild yam" or "Elephant foot". The Sanskrit name for this plant is "Varahikand," while in Hindi, it is known as "Gun" or "Singly-mingly." The Urdu language refers to it as "Qanis," and in Nepali, it is called "Tarul," "Bhyakur," or "Ghunar." Dioscorea deltoidea has been used to cure a wide range of human ailments for centuries. This plant has nutritional and therapeutic uses and also contains high amounts of steroidal saponins, allantoin, polyphenols, and most notably, polysaccharides and diosgenin. These bioactive chemicals have shown potential in providing protection against a wide spectrum of inflammatory conditions, including enteritis (inflammation of the intestines), arthritis (joint inflammation), dermatitis (skin inflammation), acute pancreatitis (inflammation of the pancreas), and neuro inflammation (inflammation in the nervous system). Furthermore, the valuable bioactive chemicals found in D. deltoidea have been associated with a range of beneficial biological activities, such as antibacterial, antioxidant, anti-inflammatory, immunomodulatory, hepatoprotective, and cytotoxic properties. Sapogenin steroidal chemicals are highly valued in the fields of medicine, manufacturing, and commerce. It has both expectorant and sedative properties. It is employed in the treatment of cardiovascular diseases, encompassing various ailments related to the heart and blood vessels, skin disease, cancer, immune deficiencies, and autoimmune diseases. Additionally, it finds application in managing disorders of the central nervous system and dysfunctional changes in the female reproductive system. Furthermore, it is valued for its role in treating bone and joint diseases. Metabolic disorders are also among the ailments for which D. deltoidea is employed. It has traditionally been used as a vermifuge, fish poison, and to kill lice. Diosgenin, a steroidal compound found in D. deltoidea, plays a crucial role as a precursor in the chemical synthesis of various hormones. Due to the presence of valuable bioactive molecule, like corticosterone and sigmasterol, D. deltoidea is cultivated specifically for the extraction of these beneficial phytochemicals. The current study aims to assess D. deltoidea's medicinal properties, ethnobotanical usage, phytochemicals, pharmacological properties, threats, and conservation techniques.

The Isolation, Identification and Immobilization Method of Three Novel Enzymes with Diosgenin-Producing Activity Derived from an Aspergillus flavus

Diosgenin is an important raw material used in the synthesis of steroid drugs, and it is widely used in the pharmaceutical industry. The traditional method of producing diosgenin is through using raw materials provided via the plant Dioscorea zingiberensis C. H. Wright (DZW), which is subsequently industrially hydrolyzed using a high quantity of hydrochloric and sulfuric acids at temperatures ranging from 70 °C to 175 °C. This process results in a significant amount of unmanageable wastewater, creates issues of severe environmental pollution and consumes high quantities of energy. As an alternative, the enzymolysis of DZW to produce diosgenin is an environmentally and friendly method with wide-ranging prospects for its application. However, there are still only a few enzymes that are suitable for production on an industrial scale. In this study, three new key enzymes, E1, E2, and E3, with a high conversion stability of diosgenin, were isolated and identified using an enzyme-linked-substrate autography strategy. HPLC-MS/MS identification showed that E1, a 134.45 kDa protein with 1019 amino acids (AAs), is a zinc-dependent protein similar to the M16 family. E2, a 97.89 kDa protein with 910 AAs, is a type of endo-β-1,3-glucanase. E3, a 51.6 kDa protein with 476 AAs, is a type of Xaa-Pro aminopeptidase. In addition, the method to immobilize these proteins was optimized, and stability was achieved. The results show that the optimal immobilization parameters are 3.5% sodium alginate, 3.45% calcium chloride concentration, 1.4 h fixed time, and pH 8.8; and the recovery rate of enzyme activity can reach 43.98%. A level of 70.3% relative enzyme activity can be obtained after employing six cycles of the optimized technology. Compared with free enzymes, immobilized enzymes have improved stability, acid and alkaline resistance and reusability, which are conducive to large-scale industrial production.

Research progress of diosgenin extraction from Dioscorea zingiberensis C. H. Wright: Inspiration of novel method with environmental protection and efficient characteristics

Diosgenin was the starting materials to synthesize various hormone drugs and mainly generated from Dioscorea zingiberensis C. H. Wright by acidolysis, enzymolysis, microbiological fermentation, and integrated manner. Only acidic hydrolysis with strong acid such as hydrochloric acid or sulfuric acid was used in practice in diosgenin enterprises due to their feasibility and simplicity, nevertheless finally resulting in a great deal of unmanageable wastewater and severely polluted the surrounding environment. Aiming to provide a comprehensive and up-to date information of researches on diosgenin production from this plant, 151 cases were collected from scientific databases including Web of Science, Pubmed, Science Direct, Wiley, Springer, and China Knowledge Resource Integrated (CNKI). Their advantages and disadvantages with different production methods were analyzed based on these available data in this review paper. Considering the fact that nearly all of diosgenin enterprises were closed for the environmental protection and the life health of the people, this review paper was beneficial for providing useful guidelines to develop novel technologies with environmentally-friendly and cleaner features for diosgenin production or facilitate the transformation of other methods like enzymolysis, microbiological fermentation, or integrated methods from laboratory scale to industry scale.

Quest for a Cure: Potential Small-Molecule Treatments for COVID-19, Part 2

During the first year of the outbreak of the COVID-19 pandemic, many drugs and drug candidates have been evaluated as treatment options. None yet has proved to be an effective cure, but progress in controlling the disease has been made. In June 2020 we published an article that described the mechanistic rationale behind the repurposing of seven licensed drugs in clinical trials for the treatment of COVID-19 and reviewed synthetic routes to these drugs. Several developments have occurred since then. Remdesivir (trade name Veklury) has been approved for use in the U.S. and Europe. Dexamethasone, a steroid drug first approved in 1959, has shown mortality reduction in severe COVID patients. Molnupiravir, a new and promising oral antiviral drug, is being studied in late-stage clinical trials. In this review, we update synthetic work that has been recently published on remdesivir, provide an overview of several routes to molnupiravir, and review classical routes to dexamethasone as well as some of those more recently developed.

Screening and Selection of a New Medium for Diosgenin Production via Microbial Biocatalysis of Fusarium sp

Steroidal saponins are widely used as starting precursors and medical intermediates for the semi-/total-synthesis of hundreds of steroidal drugs. One such steroidal saponin is diosgenin, which has attracted significant attention due to the huge market demand in the pharmaceutical industry. Due to water waste and severe environmental pollution, the traditional diosgenin production process based on direct acid hydrolysis is no longer used. In this study, to develop a submerged fermentation (SmF) medium for clean diosgenin production via efficient microbial biocatalysis, the Box-Behnken design (BBD) in combination with the Plackett-Burman design (PBD) was used to determine the medium compositions for Fusarium strains. Three components (wheat bran, phosphate, and Tween-80) were determined as significant factors by the PBD. Using the BBD, the three significant factors were further optimized, and the optimum values were determined for maximal diosgenin production. With 21.16 g/L of wheat bran, 9.60 g/L of phosphate, and 1.97 g/L of Tween-80, the diosgenin yield was 2.28%, i.e., 3.17 mg/L/h. The experimental values agreed with the predicted values, representing a significant increase in diosgenin production compared to its production using the basic SmF medium. For the first time, we reported the development of a new medium for Fusarium strains to produce diosgenin via microbial biocatalysis of the root of Dioscorea zingiberensis C. H. Wright (DZW). A simple-composition, low-cost, and high-efficiency medium was developed for the first time for the SmF of Fusarium strains. The medium is considered useful for large-scale SmF and may be applicable to other fungi. This study lays a solid foundation for diosgenin production in an acid-free and wastewater-free way. It may also provide fundamental support for producing other value-added products via microbial biocatalysis of low-value materials by endophytic fungi.

Development of a New Bioprocess for Clean Diosgenin Production through Submerged Fermentation of an Endophytic Fungus

Diosgenin is used widely to synthesize steroidal hormone drugs in the pharmaceutical industry. The conventional diosgenin production process, direct acid hydrolysis of the root of Dioscorea zingiberensis C. H. Wright (DZW), causes large amounts of wastewater and severe environmental pollution. To develop a clean and effective method, the endophytic fungus Fusarium sp. CPCC 400226 was screened for the first time for the microbial biotransformation of DZW in submerged fermentation (SmF). Statistical design and response surface methodology (RSM) were implemented to develop the diosgenin production process using the Fusarium strains. The environmental variables that significantly affected diosgenin yield were determined by the two-level Plackett-Burman design (PBD) with nine factors. PBD indicates that the fermentation period, culture temperature, and antifoam reagent addition are the most influential variables. These three variables were further optimized using the response surface design (RSD). A quadratic model was then built by the central composite design (CCD) to study the impact of interaction and quadratic effect on diosgenin yield. The values of the coefficient of determination for the PBD and CCD models were all over 0.95. P-values for both models were 0.0024 and <0.001, with F-values of ∼414 and ∼2215, respectively. The predicted results showed that a maximum diosgenin yield of 2.22% could be obtained with a fermentation period of 11.89 days, a culture temperature of 30.17 °C, and an antifoam reagent addition of 0.20%. The experimental value was 2.24%, which was in great agreement with predicted value. As a result, over 80% of the steroidal saponins in DZW were converted into diosgenin, presenting a ∼3-fold increase in diosgenin yield. For the first time, we report the SmF of a Fusarium strain used to produce diosgenin through the microbial biotransformation of DZW. A practical diosgenin production process was established for the first time for Fusarium strains. This bioprocess is acid-free and wastewater-free, providing a promising environmentally friendly alternative to diosgenin production in industrial applications. The information provided in the current study may be applicable to produce diosgenin in SmF by other endophytic fungi and lays a solid foundation for endophytic fungi to produce natural products.

Microwave-assisted extraction and a new determination method for total steroid saponins from Dioscorea zingiberensis C.H. Wright

An efficient microwave-assisted extraction (MAE) technique was applied to isolate total steroid saponins from Dioscorea zingiberensis C.H. Wright (DZW). The optimal extracting conditions were established as 75% ethanol as solvent, ratio of solid/liquid 1:20 (g/ml), temperature 75 °C, irradiation power 600 W and three extraction cycles of 6 min each. Scanning electron microscopy (SEM) images of DZW processed by four different extractions provided visual evidence of the disruption effect on DZW. Diosgenin was quantified by HPLC and examined further by LC-ESI/MS after acid hydrolysis. Total steroid saponins were calculated using diosgenin from total steroid saponins. The MAE procedure was optimized, validated and compared with other conventional extraction processes. This report provides a convenient technology for the extraction and quantification of total saponins of DZW combining MAE with HPLC and LC-ESI/MS for the first time.

Distribution and effect of steroidal saponin derivative WRC3 in B16 melanoma cells

Steroidal saponins have recently attracted attention due to their structural diversity and significant biological activities, including anti‑hyperlipidemic, antibacterial, anti‑inflammatory, immunomodulatory and anti‑HIV activities. In the present study, it was demonstrated that WRC3, a novel saponin derivative, can inhibit B16 cancer cells by inducing apoptotic cell death with an IC50 value of 12.09 µM. The inhibitory effect of WRC3 on B16 cells appears to occur in a time‑ and concentration‑dependent manner. The fluorescence distribution observed by confocal microscopy revealed that WRC3 entered cells and acted in the cytoplasm without causing genetic toxicity. Following administration of WRC3 (2.5, 5.0 and 7.5 g/kg body weight) once a day for 7 days, no obvious abnormalities were observed in the organs of the mice as demonstrated by hematoxylin and eosin staining. Compared with the normal control group, aspartate transaminase (AST), alanine transaminase (ALT), creatine and urea levels in the serum of mice treated with WRC3 (2.5‑7.5 µM) remained unchanged. In conclusion, it was demonstrated that WRC3 can induce cancer cell death without causing genetic toxicity, hepatotoxicity or nephrotoxicity.

Conversion of furostanol saponins into spirostanol saponins improves the yield of diosgenin from Dioscorea zingiberensis by acid hydrolysis

Conversion of furostanol saponins into spirostanol saponins avoiding the side product increases the diosgenin yield in acid hydrolysis of Dioscorea zingiberensis.

Biotransformation of steroidal saponins in sisal (Agave sisalana Perrine) to tigogenin by a newly isolated strain from a karst area of Guilin, China

A rod-shaped bacterium was isolated from the soil in a karst area of Guilin, China and its biotransformation of steroidal saponins in sisal (Agave sisalana Perrine) to tigogenin was presented for the first time. A total of 22 strains for the degradation of steroidal saponins in sisal were isolated from 48 soil samples, and the isolated rod-shaped, bacterial strain ZG-21 was used for the production of tigogenin due to its highest degradation efficiency of steroidal saponins in sisal. The parameters affecting biotransformation by strain ZG-21 were optimized. Under the optimized conditions of temperature (30 °C), pH (6), time (5 days) and substrate concentration (5 mg/mL), a maximum tigogenin yield of 26.7 mg/g was achieved. Compared with the conventional method of acid hydrolysis, the biotransformation method provided a clean and eco-friendly alternative for the production of tigogenin.

Evaluation of different pretreatments on microbial transformation of saponins in Dioscorea zingiberensis for diosgenin production

In order to evaluate the effects of different pretreatments on microbial transformation of saponins in Dioscorea zingiberensis (DZW), various methods have been systematically studied on a large scale. Five pretreatments, including physical separation, catalytic solvent extraction, ultrasonic fermentation, complex enzymatic hydrolyzation and enzymatic saccharification, were performed on DZW. Compared with other methods, complex enzymatic hydrolyzation significantly improved the efficiency of microbial transformation. Due to the pretreatment, a diosgenin yield of 92.6%, and diosgenin accumulation of 27.3 mg/g DZW were achieved. The high efficiency of this method was attributed to the separation of 84.3% starch and 76.5% fibre from DZW in the form of a sugar. Analysis of saponins in this microbial transformation process showed that the residual rates of the intermediate products were much lower than those obtained from other pretreatments. The results demonstrate that complex enzymatic hydrolyzation is a practical and effective pretreatment method for production of diosgenin from DZW in a microbial transformation way.

Extraction optimization of water-extracted mycelial polysaccharide from endophytic fungus Fusarium oxysporum Dzf17 by response surface methodology

Water-extracted mycelial polysaccharide (WPS) from the endophytic fungus Fusarium oxysporum Dzf17 isolated from Dioscorea zingiberensis was found to be an efficient elicitor to enhance diosgenin accumulation in D. zingigerensis cultures, and also demonstrated antioxidant activity. In this study, response surface methodology (RSM) was employed to optimize the extraction process of WPS from F. oxysporum Dzf17 using Box-Behnken design (BBD). The ranges of the factors investigated were 1–3 h for extraction time (X₁), 80–100 °C for extraction temperature (X₂), and 20–40 (v/w) for ratio of water volume (mL) to raw material weight (g) (X₃). The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis. Statistical analysis showed that the polynomial regression model was in good agreement with the experimental results with the determination coefficient (R²) of 0.9978. By solving the regression equation and analyzing the response surface contour plots, the extraction parameters were optimized as 1.7 h for extraction time, 95 °C for extraction temperature, 39 (v/w) for ratio of water volume (mL) to raw material weight (g), and with 2 extractions. The maximum value (10.862%) of WPS yield was obtained when the WPS extraction process was conducted under the optimal conditions.

A novel β-glucosidase from Aspergillus fumigates releases diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW)

A β-glucosidase effectively releasing diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW), named AfG, was purified from a strain of Aspergillus fumigates. The molecular weight of AfG was 113 kDa. Analysis of protein fragments by ESI-Q-TOF indicated that AfG was a β-glucosidase. The circular dichroism spectrum suggested that the main secondary structure of AfG in Milli-Q water was α-helixes. Atomic force microscopy revealed that it was a globular protein. AfG maintained high activity from pH 3.6 to 5.0 and from 50 to 90°C. With the strong heat stability, AfG retained 55% of its original activity at 65°C for 120 h. AfG utilized muti-3-O-glycosides of various steroidal saponins from DZW as substrate, such as trillin, diosgenin diglucoside, dioscin, deltonin and gracillin, to yield diosgenin, suggesting the possibility of producing diosgenin from total saponins of DZW using a single enzyme.

Effects of polysaccharide elicitors from endophytic Fusarium oxysporium Dzf17 on growth and diosgenin production in cell suspension culture of Dioscorea zingiberensis

Three polysaccharides, namely exopolysaccharide (EPS), water-extracted mycelial polysaccharide (WPS) and sodium hydroxide-extracted mycelial polysaccharide (SPS), were prepared from the endophytic fungus Fusarium oxysporium Dzf17 isolated from the rhizomes of Dioscorea zingiberensis. The effects of the time of addition and polysaccharide concentration on the growth and diosgenin accumulation in cell suspension culture of D. zingiberensis were studied. Among them, WPS was found to be the most effective polysaccharide. When WPS was added to the medium at 20 mg/L on the 25th day of culture, the cell dry weight was increased 1.34-fold, diosgenin content 2.85-fold, and diosgenin yield 3.83-fold in comparison to those of control. EPS and SPS showed moderate and relatively weak enhancement effects on cell growth and diosgenin accumulation, respectively. The dynamics of cell growth and diosgenin accumulation when WPS was added to the medium at 20 mg/L on the 25th day of culture were investigated, and results showed that dry weight of cells reached a maximum value on day 30 but the maximum diosgenin content was achieved on day 31.