An Umbrella Insight into the Phytochemistry Features and Biological Activities of Corn Silk: A Narrative Review

Corn silk (Zea mays L.) is the stigma of an annual gramineous plant named corn, which is distributed in many regions worldwide and has a long history of medicinal use. In recent years, with the sustainable development of traditional Chinese medicine, studies of corn silk based on modern technologies, such as GC-MS, LC-MS, and other analytical means, have offered more comprehensive analyses. Phytochemistry studies have shown that the main bioactive components in corn silk include flavonoids, polyphenols, phenolic acids, fatty acids, and terpenoids. Pharmacological studies have shown that corn silk extract has various pharmacological effects, such as reducing blood lipids, lowering blood pressure, regulating blood sugar levels, anti-inflammatory effects, and anti-oxidation effects. In this paper, the related research on corn silk from the past few years is summarized to provide a theoretical reference for the further development and utilization of corn silk.

Studies on the key constituents and the related mechanisms of Clerodendranthus spicatus in the treatment of diabetes based on network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Clerodendranthus spicatus is a traditional Chinese medicine and has been used to treat diabetes and some kidney diseases for a long history.

AIM OF THE STUDY

The research aimed to study the active constituents, the potential targets and the related mechanisms of C. spicatus in the treatment of diabetes through network pharmacology method and verify the antidiabetic activity by molecular biology experiments.

MATERIALS AND METHODS

A comprehensive network pharmacology strategy was used to predict the key active constituents, the key targets and the related mechanisms and pathways of C. spicatus in the treatment of diabetes. The strategy mainly included screening and predicting potential active constituents and targets by network construction, GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis. Based on the predicted results, C. spicatus was extracted by ultrasonic method with 50% ethanol and enriched by using macroporous resin. The compounds with potential antidiabetic effects were separated through silica-gel column chromatography and HPLC (high performance liquid chromatography), and then identified by MS (mass spectrum) and NMR (nuclear magnetic resonance). The C. spicatus extract and isolated compounds were tested by in-vitro and cell experiments to verify their antidiabetic activities, including antioxidant activities, inhibition activities on α-glucosidase and α-amylase, the influence on glucose uptake in cell experiments and the Western blot of PI3K and Akt expression levels.

RESULTS

A total of 18 active constituents and 16 key targets of C. spicatus in the treatment of diabetes were screened out through network pharmacology method. Phenolic acids might be the main target compounds for the next research. After extraction, enrichment and separation, the phenolic acids-enriched fraction of C. spicatus and four phenolic acid compounds (helisterculin C, salvianolic acid B, orthosiphoic acid E and ethyl caffeate) were obtained. Among them, salvianolic acid B was isolated from C. spicatus for the first time and orthosiphoic acid E was isolated from natural products for the first time. In experiment verification, the crude extract of C. spicatus, the phenolic acids-enriched fraction and the four compounds all showed antidiabetic potentials. The phenolic acids in C. spicatus had antioxidant activities, inhibitory activities on α-amylase and α-glucosidase and promoted glucose uptake in L6 cells through PI3K/Akt signaling pathway.

CONCLUSIONS

This study showed that C. spicatus had antidiabetic activities with the mechanism of the mode of multi-compounds acting on multi-targets and multi-pathways. The main active phenolic acid compounds were also identified. It provided theoretical basis for further development and utilization of C. spicatus.

Maize Silk Biogenic Nanoceria (CeO2NPs) Enhanced Sequential Injection-Chemiluminescence Detection of Ferulic, Sinapic and p-Coumaric in Yellow Maize Kernels

The current study demonstrated the capability of using maize silk as a green, simple, clean, safe, and cost-effective platform for the biosynthesis of cerium oxide (CeO₂NPs). Several spectroscopic and microscopic analyses were employed to characterize the resulted biogenic nanoceria. When the concentration of the CeO₂NPs was elevated from 25 to 100 ug mL⁻¹, the CeO₂NPs exhibited strong scavenging potential ranging from 60.21 to 75.11% and 56 to 77% for 1,1-diphenyl-2- picrylhydrazyl (DPPH•) and 2-2′-azino-bis(3-ethyl benzothiazoline-6-sulphonic acid) (ABTS) tests, respectively. The quantitative determination of ferulic, sinapic, and p-coumaric acids was carried out using an eco-friendly, cost-effective, and optimized ultrasensitive nanoceria enhanced sequential injection-chemiluminescence (SIA-CL) system. The highest amount was presented by the ferulic acid (1636 ± 2.61 ug/g_dw), followed by p-coumaric acid (206 ± 1.12 ug/g_dw) and sinapic acid (123 ± 2.15 ug/g_dw). The intrinsic capabilities of the biogenic CeO₂NPs in enhancing the developed system reveal its potential role in detecting phenolic compounds with great sensitivity.

Ameliorated membranous nephropathy activities of two ethanol extracts from corn silk and identification of flavonoid active compounds by LC-MS2

The current study looks to evaluate the effect of corn silk flavonoids on membranous nephropathy (MN). Polyamide resin (PR) can be used to enrich corn silk ethanol extract (CSEE) to obtain flavonoid-rich extract (PR-CSEE), the total flavonoid content (TFC) of which we found to be 57.4%. The results of scanning electron microscope, Fourier-transform infrared, and high-performance liquid chromatography analyses determined that PR-CSEE and CSEE have different structural characteristics, but that PR-CSEE has higher TFC. MN mice models were induced by cationic bovine serum albumin, and we found that PR-CSEE administration reduced urine protein levels markedly, while renal function, glomerular atrophy, inflammatory infiltration, and in-serum immunoglobulin G and complement 3 content were improved. Through LC-MS² spectrometry analysis, we pinpointed the 12 major flavonoid active compounds in PR-CSEE. These findings suggest that PR-CSEE can act as a potential functional food material by which to improve MN.

Hypouricemia effects of corn silk flavonoids in a mouse model of potassium oxonated-induced hyperuricemia

The hypouricemic effect of corn silk flavonoids (CSFs) in vivo that were extracted by ethanol and fractionated by continuous elution with 40% (CSF-A) and 60% (CSF-B) ethanol solutions on polyamide column were investigated in this study. CSFs reduced serum uric acid (UA) level in a mouse model of potassium oxonate-induced hyperuricemia. CSF-B had the best hypouricemic effect, as it decreased the serum UA level by 26.69% and xanthine oxidase (XO) activity in the serum by 11.29%. The mechanism of action of CSF-B was related to the inhibition of XO activity and the promotion of UA excretion. CSF-B was found to contain 12 kinds of major flavonoids, five of which were speculated to influence its activity in the hyperuricemia mice. The five flavonoids were apigenin-6-C-glucoside-7-O-glucoside, kaempferol-3-O-rutinoside, luteolin-7-glucoside, luteolin-3',7-di-O-glucoside, and naringenin, respectively. Structure analysis revealed that C-4', C5 hydroxyl groups, and C2=C3 double bonds in CSF-B gave the latter its hypouricemic effect. PRACTICAL APPLICATIONS: The prevalence of hyperuricemia has increased in recent times. Current hypouricemic drugs have side effects and can easily lead to various complications. Therefore, it is of great practical significance to find safer and more effective hypouricemic drugs. This study demonstrated that corn silk flavonoids may be used as a dietary supplement to manage hyperuricemia.

Characterization, antioxidant activities, and inhibition on α-glucosidase activity of corn silk polysaccharides obtained by different extraction methods

The polysaccharides (CSPw, CSPc, CSPa, and CSPu) were prepared by hot water extraction, acid-assisted extraction, alkaline-assisted extraction, and ultrasound-assisted extraction from corn silk, respectively. High performance gel permeation chromatography (HPGPC), fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) results indicated that the extraction methods had an obvious impact on the molecular weight, structure, and morphology of the CSPs. Among the four polysaccharides, CSPu showed the highest inhibitory α-glucosidase activity, which might be related to its smaller molecular weight. Furthermore, kinetics analyses revealed that CSPu had significant inhibition of α-glucosidase in a non-reversible and competitive manner. Fluorescence quenching analysis illustrated that the interaction mechanism of CSPu and α-glucosidase was claimed as a static quenching mechanism. Isothermal titration calorimetry (ITC) analysis showed that the main driving forces for the interaction of CSPu with α-glucosidase was hydrogen bonding and the binding interactions of them occurred spontaneously.

Postprandial Glycemic and Insulinemic Effects of the Addition of Aqueous Extracts of Dried Corn Silk, Cumin Seed Powder or Tamarind Pulp, in Two Forms, Consumed with High Glycemic Index Rice

Several plant-based traditional ingredients in Asia are anecdotally used for preventing and/or treating type 2 diabetes. We investigated three such widely consumed ingredients, namely corn silk (CS), cumin (CU), and tamarind (TA). The aim of the study was to determine the effects of aqueous extracts of these ingredients consumed either as a drink (D) with high-glycemic-index rice or added to the same amount of rice during cooking (R) on postprandial glycemia (PPG), insulinemia (PPI), and blood pressure (BP), over a 3 h measurement period. Eighteen healthy Chinese men (aged 37.5 ± 12.5 years, BMI 21.8 ± 1.67 kg/m²) took part in a randomized crossover trial, each completing up to nine sessions. Compared to the control meal (plain rice + plain water), the addition of test extracts in either form did not modulate PPG, PPI, or BP. However, the extracts when added within rice while cooking gave rise to significantly lower PPI than when consumed as a drink (p < 0.01). Therefore, the form of consumption of phytochemical-rich ingredients can differentially modulate glucose homeostasis. This study also highlights the need for undertaking randomized controlled clinical trials with traditional foods/components before claims are made on their specific health effects.

Potential Photoprotective Effect of Dietary Corn Silk Extract on Ultraviolet B-Induced Skin Damage

Ultraviolet B (UVB) irradiation causes adverse effects on the skin. Corn silk contains flavonoids and other bioactive compounds and antioxidants, which may prevent skin photoaging through antioxidant and anti-inflammatory effects. We aimed to investigate the potential photoprotective effects of dietary corn silk on UVB-induced skin damage in mice and the mechanisms behind these effects on human skin cells. Oral administration of corn silk water extract (CS) (2 or 4 g/kg/day) for 19 weeks decreased epidermal thickness, wrinkle formation, and positive staining for PCNA, Ki67, and 8-OHdG, and increased collagen staining in UVB-irradiated SKH-1 hairless mice compared with controls. The pro-inflammatory NF-κB target genes (IL-1β, iNOS, and COX-2) and MMP-9 expressions were lower in the CS groups, and TGF-β/Smad signaling increased. Low skin lipid peroxidation and blood DNA oxidation levels and high blood glutathione were detected. Antioxidant transcription factor Nrf2-related catalase and SOD1 proteins and glutaredoxin mRNA levels increased. The results of CS extract treatment and UVB irradiation in HaCaT cells showed the same results in Nrf2 and NF-κB target genes. An LC-MS/MS analysis showed that the CS extract contained potential antioxidants, which might have contributed to its anti-photoaging effects in tissues and cells. CS extract may reduce UVB-induced skin damage through antioxidant and anti-inflammatory mechanisms.

Rapid discovery and global characterization of multiple components in corn silk using a multivariate data processing approach based on UHPLC coupled with electrospray ionization/quadrupole time-of-flight mass spectrometry

Corn silk is an important traditional Chinese medicine which has been widely used as diuretic, antilithiasic, uricosuric, antiseptic, etc. for thousands of years. However, it is a pity that the chemical ingredients in corn silk, especially the constituents absorbed into blood, are unclear up to now. The aim of our study was to investigate the multiple components of corn silk in vitro and in vivo. In this present study, a sensitive and rapid method using ultra high performance liquid chromatography coupled with electrospray ionization/quadrupole time-of-flight tandem mass spectrometry and a multivariate data processing approach was established to detect the constituents of corn silk in vitro and in vivo. Consequently, total 41 ingredients in vitro and 19 of them absorbed into blood including luteolin, various C-glycosyl flavones, jasmonic acid, abscisic acid, gibberellin A, etc. were tentatively characterized in sequence. Furthermore, of particular importance, a kind of stable compound named C-glycosyl flavones is a great discovery in vivo, which can point the further pharmacological study target in future. In a word, this is the first serum pharmacochemistry study of corn silk, which played a critical role in exploring the pharmacological and effective data for further research.

Studies on the binding characteristics of three polysaccharides with different molecular weight and flavonoids from corn silk (Maydis stigma)

Polysaccharides and flavonoids co-existed in corn silk (Maydis stigma) could interact inevitably during processing and digestion. In this study, the binding interaction between three polysaccharides with different molecular weight and flavonoids from corn silk was characterized using molecular dynamic and thermodynamic simulation. And the corn silk polysaccharides-flavonoids complex (CSP - CSF complex) was characterized using fourier transform infrared (FT-IR) spectra, circular dichroism (CD), scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The three polysaccharides from corn silk showed the molecular weight distributions of 43.3 kDa, 61.3 kDa and 106.6 kDa, respectively, and they had the same monosaccharide types with different ratios. The adsorption of flavonoids to polysaccharides might be mostly driven by van der Waals forces and hydrogen bonding, and it could be described through various isothermal models and thermodynamic equations such as Langmuir, Freundlich equations and Clausius-Clapeyron equation. This type of interactions could improve the biological activities of polysaccharides such as α-amylase and α-glucosidase inhibition.

C-Glycosylflavones Alleviate Tau Phosphorylation and Amyloid Neurotoxicity through GSK3β Inhibition

Alzheimer's disease (AD) is the most common brain disorder worldwide. Aberrant tau hyperphosphorylation and accumulation play critical roles in the formation of neurofibrillary tangles highly associated with neuronal dysfunction and cognitive impairment in AD pathogenesis. Glycogen synthase kinase-3β (GSK3β) is a key kinase responsible for tau hyperphosphorylation. Selective inhibition of GSK3β is a promising strategy in AD therapy. Corn silks (CS, Zea mays L.) have been traditionally used as a medicinal herb and recently noted for their potentially cognitive benefits. However, the neuroprotective components of CS and their molecular mechanism have received little attention to date. As part of our effort screening phytochemicals against a broad panel of kinases targeting AD tauopathy, we found inhibition of GSK3β by CS extracts. Subsequent bioassay-guided fractionation led to the isolation and identification of two 6-C-glycosylflavones, isoorientin (1) and 3'-methoxymaysin (2), with selective inhibition against GSK3β in vitro. Enzyme kinetics and molecular docking studies demonstrated that 1 specifically inhibited GSK3β via an ATP noncompetitive mechanism, acting as a substrate competitive inhibitor of GSK3β. Further in vitro cellular studies demonstrated that 1 effectively attenuated tau phosphorylation mediated by GSK3β and was neuroprotective against β-amyloid-induced tau hyperphosphorylation and neurotoxicity in SH-SY5Y cells. The C-glycosylflavones represent new lead candidates with a novel mechanism of action for the development of AD phytopharmaceuticals.