A new estimation of the total flavonoids in silkworm cocoon sericin layer through aglycone determination by hydrolysis-assisted extraction and HPLC-DAD analysis

Potential therapeutic agents of Bombyx mori silk cocoon extracts from agricultural product for inhibition of skin pathogenic bacteria and free radicals

Background

Pathogenic bacteria are the cause of most skin diseases, but issues such as resistance and environmental degradation drive the need to research alternative treatments. It is reported that silk cocoon extract possesses antioxidant properties. During silk processing, the degumming of silk cocoons creates a byproduct that contains natural active substances. These substances were found to have inhibitory effects on bacterial growth, DNA synthesis, the pathogenesis of hemolysis, and biofilm formation. Thus, silk cocoon extracts can be used in therapeutic applications for the prevention and treatment of skin pathogenic bacterial infections.

Methods

The extract of silk cocoons with pupae (SCP) and silk cocoons without pupae (SCWP) were obtained by boiling with distilled water for 9 h and 12 h, and were compared to silkworm pupae (SP) extract that was boiled for 1 h. The active compounds in the extracts, including gallic acid and quercetin, were determined using high-performance liquid chromatography (HPLC). Furthermore, the total phenolic and flavonoid content in the extracts were investigated using the Folin-Ciocalteu method and the aluminum chloride colorimetric method, respectively. To assess antioxidant activity, the extracts were evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Additionally, the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of silk extracts and phytochemical compounds were determined against skin pathogenic bacteria. This study assessed the effects of the extracts and phytochemical compounds on growth inhibition, biofilm formation, hemolysis protection, and DNA synthesis of bacteria.

Results

The HPLC characterization of the silk extracts showed gallic acid levels to be the highest, especially in SCP (8.638-31.605 mg/g extract) and SP (64.530 mg/g extract); whereas quercetin compound was only detected in SCWP (0.021-0.031 mg/g extract). The total phenolics and flavonoids in silk extracts exhibited antioxidant and antimicrobial activity. Additionally, SCP at 9 h and 12 h revealed the highest anti-bacterial activity, with the lowest MIC and MBC of 50-100 mg/mL against skin pathogenic bacteria including Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Cutibacterium acnes and Pseudomonas aeruginosa. Hence, SCP extract and non-sericin compounds containing gallic acid and quercetin exhibited the strongest inhibition of both growth and DNA synthesis on skin pathogenic bacteria. The suppression of bacterial pathogenesis, including preformed and matured biofilms, and hemolysis activity, were also revealed in SCP extract and non-sericin compounds. The results show that the byproduct of silk processing can serve as an alternative source of natural phenolic and flavonoid antioxidants that can be used in therapeutic applications for the prevention and treatment of pathogenic bacterial skin infections.

Development of a novel, sustainable, cellulose-based food packaging material and its application for pears

This study aimed to develop a cellulose-based active food packaging material using paper, a biodegradable, sustainable, recyclable, renewable, and relatively low-cost material. For electrospray coating, fulvic acid (FA), which has antioxidant and antimicrobial properties, and sericin (S) were used as an active agent and a carrier medium, respectively. Solutions prepared at various concentrations and ratios of FA and S were analyzed, the properties of the active packaging material were examined, and the effect on the quality of pears was studied. The optimum conditions of electrospraying for minimum droplet size and maximum antibacterial effect were 0.8 g/mL concentration of solutions, 1:1 FA:S ratio, 20 kV voltage, 0.75 mL/h flow rate, and 23 cm collector-needle tip distance. FA had static, lethal, and inhibitory effects on Pseudomonas syringae and P. digitatum, the common pathogenic microorganisms on pears. The antioxidant activity of FA was higher than that of S (872.96 mM vs. 239.36 mM). At the end of the 90-day storage period, pears stored in the active packaging material at 7 °C and 90% RH showed better preserved color and texture, matured later, had a lower antimicrobial load, and were more appreciated in sensory evaluation than other samples.

Bombyx mori cocoon as a promising pharmacological agent: A review of ethnopharmacology, chemistry, and biological activities

Silk cocoon, naturally produced by silkworms scientifically named Bombyx mori L. (Lepidoptera, Bombycidae), is one of the well-known medicinal agents with several therapeutic activities. The present study aims to review the various aspects of the silk cocoon, including chemical composition, traditional uses, biological and biotechnological activities, and toxicological issues, to provide a scientific source for scholars. For this purpose, Electronic databases including PubMed, Scopus, Google Scholar, Web of Science, and traditional literature, were searched up to December 2021. According to the historical data, silk farming is acknowledged as one of the most ancient agricultural findings. The silk is generally composed of 75–83% fibroin, 17–25% sericin, and 1–5% non-sericin components, including secondary metabolites, wax, pigments, carbohydrates, and other impurities. Flavonoids, especially quercetin and kaempferol, alkaloids, coumarin derivatives, and phenolic acids, are among the secondary metabolites isolated from the silk cocoon. In recent years the biological properties of the silk cocoon, especially its major proteins, namely fibroin and sericin, have drawn special attention. Scientific literature has investigated several pharmacological effects of the silk cocoon and its ingredients, including cardioprotective, antioxidant, anticancer, antidiabetic, antihyperlipidemia, gastroprotective, as well as ameliorated skin health activities. In addition, it has been extensively taken into consideration in drug delivery and tissue engineering study fields. Furthermore, its toxicity is in acceptable range.

Bioactive Flavonoids: A Comprehensive Review on Pharmacokinetics and Analytical Aspects

Flavonoids are a diversified group of natural substances which were discovered to provide a variety of health benefits in human beings. Vegetables, fruits, wine and tea are the primary flavonoid dietary sources for humans and as the flavonoids are so closely connected to human dietary items and health, it is vital to explore the structural-activity connection. The arrangement, replacement of functional groups, and total number of hydroxyl groups around flavonoid's nucleus structure affect their biological activity, metabolism, and bioavailability. Various flavonoids have been proven to have hepatoprotective properties, that help in the prevention of coronary heart disease. Similarly, these flavonoids also possess anticancer, and anti-inflammatory activities. Flavonoids have been found to have a functional and structural link with their enzyme inhibitory action, that appears to have antiviral effect through acting as antioxidants, damaging cell membranes, blocking enzymes, activating mechanisms of host self-defense, and limiting virus penetration and attaching to cells. Identification, characterization, isolation, and biological role of flavonoids, as well as their uses on health advantages, are all major topics in research and development currently. This review represents a summary of various sources of flavonoids, class, subclass, their chemical structures, biological activities, the pharmacokinetics of flavonoids and various analytical, bioanalytical and electrochemical methods for determination of flavonoids from different matrices.

Investigation of the Repairing Effect and Mechanism of Oral Degraded Sericin on Liver Injury in Type II Diabetic Rats

In the sericulture and silk production industry, sericin is discharged in the degumming wastewater, resulting in a large amount of wasted natural protein and environmental pollution. This study investigated the effect of degraded sericin recovered by the Ca(OH)₂–ultrasound degumming method (a green process) on liver injury in T2D rats. After 4 weeks of dietary sericin supplementation, the liver masses and organ coefficients of the T2D rats improved compared with those of the model rats that were not fed sericin. Oral sericin activated the damaged PI3K/AKT/AMPK pathway to enhance glycogen synthesis, accelerate glycolysis, and inhibit gluconeogenesis. The protein expression levels of the inflammatory factors NF-κB, IL-6, and TNF-α in the T2D model group were up to two times higher than in the normal group. However, all three T2D groups that received oral sericin showed significant decreases in these factors to the level found in the normal group, indicating that inflammation in the body was significantly reduced. These results show that the sericin protein might improve glycogen synthesis, accelerate glycolysis, and inhibit gluconeogenesis by enhancing the anti-oxidation capability and reducing inflammatory reactions. Therefore, sericin recovered by Ca(OH)₂ degradation has potential use in the development of functional health foods that can lower blood sugar.

Cryoprotective effect of sericin supplementation in freezing and thawing media on the outcome of cryopreservation in human sperm

The destructive effects of sperm cryopreservation result in decreased sperm parameters and their fertilizing ability. Antioxidants supplementation can potentially improve cryopreservation outcomes. In this study, we tried to investigate the effects of sericin supplementation in freezing and thawing media on frozen-thawed human sperm motility, morphology, viability, and DNA fragmentation. In experiment 1, semen samples were collected from 30 healthy fertile men and were cryopreserved in the presence of freezing medium supplemented with different concentrations of sericin (0, 0.5, 1, 2.5, and 5%). The results showed that the addition of 2.5 and 5% sericin in freezing medium significantly increased sperm viability and total motility (A + B) and decreased DNA fragmentation (P < 0.05). In experiment 2, semen samples were collected from 21 fertile men and were cryopreserved in freezing medium without any supplementation for 48 h. Then, the samples were thawed in medium supplemented with different concentrations of sericin (0, 0.5, 1, 2.5, and 5%). The addition of 5% sericin to thawing medium increased the total motility, viability, and decreased DNA fragmentation compared with those in thaws without sericin. In nutshell, the results clearly indicate the feasibility of sericin as an cryoprotective supplement for freezing media in human spermatozoa.

The flavonoid-rich ethanolic extract from the green cocoon shell of silkworm has excellent antioxidation, glucosidase inhibition, and cell protective effects in vitro

The green cocoon shell of a novel variety of silkworm, Bombyx mori, is rich in two types of quercetin and kaempferol flavonoids. The aim of this study was to identify these flavonoids in the ethanolic extract (EE) from green cocoons and develop EE applications in healthy foods. The experimental results indicated that the amount of total amino acids in EE was 27.06%. The flavonoids in EE are presented in quercetin and kaempferol glycosides. The total amount of the two aglycones was 33.42 ± 0.08 mg/g. The IC50 values of 2,2-diphenyl-1-picrylhydrazyl (DPPH), 1,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonicacid) (ABTS), and hydroxyl radical scavenging abilities were 296.95 ± 13.24 μg/mL, 94.31 ± 9.13 μg/mL, and 9.21 ± 0.15 mg/mL, respectively. The IC50 values of the inhibitory activities of α-amylase and α-glucosidase were 37.57 ± 6.45 μg/mL and 212.69 ± 22.94 μg/mL, respectively. EE also reduced the level of reactive oxygen species (ROS) and oxidative stress in L02 cells induced by high glucose levels. It also effectively decreased the content of 8-hydroxyl deoxyguanosine (8-OHdG), nuclear factor κB (NF-κB), and tumour necrosis factor alpha (TNF-α) in cells with a good dose effect. These results clearly indicated that the flavonoid-rich EE with excellent antioxidant and glucosidase inhibition abilities significantly reduced the damage to cells caused by oxidative stress and inflammatory reactions. It is suggested that EE might serve as useful functional foods for the treatment of related diseases induced by oxidative stress such as diabetes mellitus.

Extraction and antioxidant activity of sericin, a protein from silk

Abstract Sericin is a globular protein that represents 20% to 30% of the silk fiber from Bombyx mori silkworm cocoon. This protein is usually removed from the raw fiber and discarded by silk producers, a process known as degumming. However, sericin possesses significant biological properties that allows its application in various fields. The antioxidant activity is one of its most relevant benefits. Several authors have reported its anti-tyrosinase activity, lipid peroxidation inhibition and free radical neutralization. The antioxidant potential of sericin protein varies according to the extraction method used. Even though a wide variety of extraction techniques have been studied, simple technics including water at high temperature have exhibited efficient results. Furthermore, this method does not interfere with the safety of sericin for subsequent applications in food.

Therapeutic effects of ethanolic extract from the green cocoon shell of silkworm Bombyx mori on type 2 diabetic mice and its hypoglycaemic mechanism

Diabetes mellitus is a clinically complex disease characterized by hyperglycaemia with disturbances in carbohydrate, fat and protein metabolism. The aim of this study was to determine the therapeutic effect of ethanolic extract (EE) from the green cocoon sericin layer of silkworm Bombyx mori on mice with type 2 diabetes mellitus (T2DM) and its hypoglycaemic mechanisms. The results showed that oral EE for 7 weeks had significant ameliorative effects on all the biochemical parameters studied in vivo. The levels of oral glucose tolerance and insulin tolerance were significantly improved. The hypoglycaemic rate in the 350 mg kg^-1 high dosage group was 39.38%. The levels of nuclear factor kappa B (NFκB), interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α) in the high dosage EE-treated group were significantly reduced, while activities of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were obviously increased. The islet area and the number of insulin-positive beta cells increased significantly in the high dose group. Furthermore, expression levels of insulin receptor (IR), insulin receptor substrate (IRS), phosphatidylinositide 3-kinase (PI3K), p-Akt and phospho-glycogen synthase kinase-3β (p-GSK3β) involved in insulin signalling were increased. Adenosine 5'-monophosphate-activated protein kinase (AMPK) and glucose transporter 4 (GLUT4) also were activated to regulate glucose metabolism in EE-treated groups. The levels of glucose 6-phosphatase (G6pase) and phosphoenolpyruvate carboxykinase (PEPCK) decreased, while the glucokinase (GK) level increased to promote glycolysis. The results clearly indicated that oral EE, especially at a high dose, could improve the glucose metabolism of T2DM by reducing inflammatory reactions, enhancing the antioxidant capacity and insulin sensitivity, and regulating the balance between glycolysis and gluconeogenesis, which means that EE has potential ameliorative effects on T2DM mice.

Identification and quantification and antioxidant activity of flavonoids in different strains of silk cocoon, Bombyx mori

Silk cocoon is produced from silkworm (Bombyx mori) to protect itself from outer environment. Various strains of cocoon contain different forms and amounts of flavonoids, which may affect on their antioxidant activity. Moreover, the extraction method would influence the amount of flavonoids extracted. Therefore, the objectives of this study were to identify and quantify the flavonoids in 3 strains of bivoltine Bombyx mori silk cocoon (Chul 1/1; white cocoon, Chul 3/2; greenish cocoon, and Chul 4/2; yellow cocoon) extracted by 6 different solvents including acetone, ethyl acetate, dimethyl sulfoxide (DMSO), ethanol, methanol, and purified water. The flavonoids extracted were identified and quantified by liquid chromatography-mass spectrometry (LC-MS). The antioxidant activity of flavonoids extracted was also investigated by visible spectroscopy at 517 nm. The results showed that Chul 3/2 silk cocoon contained the highest amount of flavonoids. Purified water seemed to be the best solvent that preserved most antioxidant activity of the flavonoids extracted. Flavonoids in Chul 1/1 and Chul 4/2 silk cocoon were rarely found, however they contained some antioxidant activities. The data from this study can provide basic information for flavonoid extraction from silk cocoon which can also apply for other flavonoid-containing natural biomaterials.