Corn silk (Stigma maydis) in healthcare: a phytochemical and pharmacological review

The ethyl acetate fraction of corn silk exhibits dual antioxidant and anti-glycation activities and protects insulin-secreting cells from glucotoxicity

Background

In this study, we aimed to develop a Stigmata Maydis (corn silk) fraction with dual bio-activities against oxidative stress and protein glycation to protect β-cells from diabetes-induced failure.

Methods

Corn silk fractions were prepared by partition and chemically characterised by thin-layer chromatography. Free radical scavenging assay, glycation assay, and cell-based viability test (neutral red) were employed to decide the best fraction. Cell death analysis was executed by annexin V/ Propidium iodide staining. Cell proliferation was measured by WST-1. Finally, β-cell function was evaluated by β-cell marker gene expression (RT-PCR) and acute insulin secretion test.

Results

Four corn silk fractions were prepared from an ethanolic crude extract of corn silk. In vitro assays indicate ethyl acetate fraction (YMS-EA) was the most potent fraction. YMS-EA also attenuated the hydrogen peroxide- or methylglyoxal-induced induction of reactive oxygen species, reduction of cell viability, and inhibition of cell proliferation. However, YMS-EA was unable to prevent hydrogen peroxide-induced apoptosis or advanced glycation end-products-induced toxicity. Under hyperglycemic conditions, YMS-EA effectively reduced ROS levels, improved mRNA expression of insulin, glucokinase, and PDX-1, and enhanced glucose-stimulated insulin secretion. The similarity of bioactivities among apigenin, luteolin, and YMS-EA indicated that dual activities of YMS-EA might be derived from those compounds.

Conclusions

We concluded that YMS-EA fraction could be developed as a preventive food agent against the glucotoxicity to β-cells in Type 2 diabetes.

High maysin corn silk extract reduces body weight and fat deposition in C57BL/6J mice fed high-fat diets

BACKGROUNG/OBJECTIVES

The study was performed to investigate the effects and mechanisms of action of high maysin corn silk extract on body weight and fat deposition in experimental animals.

MATERIALS/METHODS

A total of 30 male C57BL/6J mice, 4-weeks-old, were purchased and divided into three groups by weight using a randomized block design. The normal-fat (NF) group received 7% fat (diet weight basis), the high-fat (HF) group received 25% fat and 0.5% cholesterol, and the high-fat corn silk (HFCS) group received high-fat diet and high maysin corn silk extract at 100 mg/kg body weight through daily oral administration. Body weight and body fat were measured, and mRNA expression levels of proteins involved in adipocyte differentiation, fat accumulation, fat synthesis, lipolysis, and fat oxidation in adipose tissue and the liver were measured.

RESULTS

After experimental diet intake for 8 weeks, body weight was significantly lower in the HFCS group compared to the HF group (P < 0.05), and kidney fat and epididymal fat pad weights were significantly lower in the HFCS group compared to the HF group (P < 0.05). In the HFCS group, CCAAT/enhancer binding protein-β, peroxisome proliferator-activated receptor-γ1 (PPAR-γ1), and PPAR-γ2 mRNA expression levels were significantly reduced (P < 0.05) in the epididymal fat pad, whereas cluster of differentiation 36, lipoprotein lipase, acetyl-CoA carboxylase-1, sterol regulatory element binding protein-1c, pyruvate dehydrogenase kinase, isozyme-4, glucose-6-phosphate dehydrogenase, and stearoyl-CoA desaturase-1 mRNA expression levels were significantly decreased in liver and adipose tissues (P < 0.05). In the HFCS group, mRNA expression levels of AMP-activated protein kinase, hormone-sensitive lipase, and carnitine palmitoyltransferase-1 were elevated (P < 0.05).

CONCLUSIONS

It can be concluded that high maysin corn silk extract inhibits expression of genes involved in adipocyte differentiation, fat accumulation, and fat synthesis as well as promotes expression of genes involved in lipolysis and fat oxidation, further inhibiting body fat accumulation and body weight elevation in experimental animals.

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.

Corn silk extract improves cholesterol metabolism in C57BL/6J mouse fed high-fat diets

BACKGROUND/OBJECTIVES

Corn silk (CS) extract contains large amounts of maysin, which is a major flavonoid in CS. However, studies regarding the effect of CS extract on cholesterol metabolism is limited. Therefore, the purpose of this study was to determine the effect of CS extract on cholesterol metabolism in C57BL/6J mouse fed high-fat diets.

MATERIALS/METHODS

Normal-fat group fed 7% fat diet, high-fat (HF) group fed 25% fat diet, and high-fat with corn silk (HFCS) group were orally administered CS extract (100 mg/kg body weight) daily. Serum and hepatic levels of total lipids, triglycerides, and total cholesterol as well as serum free fatty acid, glucose, and insulin levels were determined. The mRNA expression levels of acyl-CoA: cholesterol acyltransferase (ACAT), cholesterol 7-alpha hydroxylase (CYP7A1), farnesoid X receptor (FXR), lecithin cholesterol acyltransferase (LCAT), low-density lipoprotein receptor, 3-hyroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), adiponectin, leptin, and tumor necrosis factor α were determined.

RESULTS

Oral administration of CS extract with HF improved serum glucose and insulin levels as well as attenuated HF-induced fatty liver. CS extracts significantly elevated mRNA expression levels of adipocytokines and reduced mRNA expression levels of HMG-CoA reductase, ACAT, and FXR. The mRNA expression levels of CYP7A1 and LCAT between the HF group and HFCS group were not statistically different.

CONCLUSIONS

CS extract supplementation with a high-fat diet improves levels of adipocytokine secretion and glucose homeostasis. CS extract is also effective in decreasing the regulatory pool of hepatic cholesterol, in line with decreased blood and hepatic levels of cholesterol though modulation of mRNA expression levels of HMG-CoA reductase, ACAT, and FXR.

Ultrasound-Assisted Extraction of Total Flavonoids from Corn Silk and Their Antioxidant Activity

Object. Ultrasound-assisted extraction of total flavonoids from corn silk and their antioxidant activities were studied.Methods. Response surface methodology was adopted to optimize the extraction conditions and antioxidant activities of the extracted total flavonoids were detected through ferric reducing antioxidant power (FRAP) assay.Results. Through a three-level, three-variable Box-Behnken design of response surface methodology (RSM) adopting yield as response, the optimal conditions were determined as follows: ultrasonic power 500 W, extraction time 20 min, material solvent ratio 1 : 20, and ethanol concentration 30%. Under the optimum conditions, the extraction yield of total flavonoids was 1.13%. FRAP value of total flavonoids extracted from corn silk was 467.59 μmol/L.Conclusion. The total flavonoids of corn silk could be developed as food natural antioxidant reagents.

Safety Evaluation, in Vitro and in Vivo Antioxidant Activity of the Flavonoid-Rich Extract from Maydis stigma

This study aimed to assess the acute toxicity and safety of flavonoid-rich extract from Maydis stigma (FMS) in mice. The in vitro antioxidant activity of FMS was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethyl-benzthiazoline-6-sulphonate) (ABTS) scavenging assays. Furthermore, the in vivo antioxidant of FMS against ethanol-induced oxidative damage in mice was determined by analysis of the serum total superoxide dismutase (T-SOD) activity, malondialdehyde (MDA) content, liver tissue glutathione (GSH) content, and protein carbonyl (PC) content in liver tissue. The oral administration of FMS at doses of 30 g/kg did not cause death in mice, and there were no significant biologically adverse effects in mice. These results indicated that the median lethal dose (LD₅₀) is higher than this dose. The IC₅₀ values of FMS for the DPPH and ABTS scavenging activity were 50.73 and 0.23 mg/mL, respectively. Meanwhile, FMS could significantly enhance T-SOD activity, reduce MDA content in the serum, increase GSH content, and decrease PC content in the liver tissue at the tested doses (25, 50, 100, 200 mg/kg·day). These results indicate that FMS can be generally regarded as safe and used potentially as a bioactive source of natural antioxidants.

Update on Medicinal Plants with Potency on Mycobacterium ulcerans

Mycobacterium ulcerans disease has been a serious threat for people living in rural remote areas. Due to poverty or availability of traditional medicine these populations rely on herbal remedies. Currently, data on the anti-Mycobacterium ulcerans activity of plants, so far considered community-based knowledge, have been scientifically confirmed, concomitantly with some medicinal plants used to treat infectious diseases in general. Products derived from plants usually responsible for the biological properties may potentially control Mycobacterium ulcerans disease; numerous studies have aimed to describe the chemical composition of these plant antimicrobials. Thus, the present work provides the first compilation of medicinal plants that demonstrated inhibitory potential on Mycobacterium ulcerans. This work shows that the natural products represent potential alternatives to standard therapies for use as curative medicine for Mycobacterium ulcerans disease.

A survey of medicinal plants for diabetes treating from Chana and Nathawee district, Songkhla province, Thailand

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus is a chronic disease which cannot be cured and must be suffered for whole life. Nowadays, many patients wanting to treat themselves by herbal medicine are increasing. Therefore, surveying of medicinal plants for treating diabetes and disseminating the knowledge, might give people more choice to consume herbs. The purposes of this qualitative study were to compile the medicinal plants and their folk use to treat diabetes by local healers in Chana and Nathawee district, Songkhla province.

MATERIALS AND METHODS

Semi-structured interviews were used to gather about the local names, parts of plants used, preparation and use method, and local properties. Descriptive statistics, use value and interpretation were used to analyze the data.

RESULTS

A total of 38 species belonging to 37 genera in 28 families were used as herbs for treating diabetes. The family mostly used as herbal medicine was Rubiaceae (4 species; 10.53%). The part of herbal medicine mostly used was the root (8 speciess; 21.05%). Decoction and drinking were the most favorite preparation form and use method. Interestingly, the most used herbal plant is Lagerstraemia speciose Pers (0.83 of Use Value).

CONCLUSION

It was found that the local healers possess the different knowledge based on their experience received secretly from the family and adapted by themselves. Thus, this study is important due to assistance for collecting the variety of knowledge before disappearing.

Ethnopharmacological reports on anti-Buruli ulcer medicinal plants in three West African countries

ETHNOPHARMACOLOGICAL RELEVANCE

Buruli ulcer (BU) is the third most common mycobacterial infection in the world, after tuberculosis and leprosy and has recently been recognized as an important emerging disease. This disease is common in West Africa where more than 99% of the burden is felt and where most affected people live in remote areas with traditional medicine as primary or only option. Reports indicate that the ethnopharmacological control approach of the disease in such settings has shown promise. However, no or very few compilations of traditional knowledge in using medicinal plants to treat BU have been attempted so far. This review aimed to record medicinal plants used traditionally against BU in three countries in West Africa: Ivory Coast, Ghana and Benin and for which ethnopharmacological knowledge supported by pharmacological investigations has been reported. The information recorded in this review will support further pharmacological research to develop appropriate drugs for a better BU control.

MATERIAL AND METHODS

A systematic review of the literature on ethnobotanical use and anti-BU activity of plants reported for BU treatment was performed. The approach consisted to search several resources, including Technical Reports, Books, Theses, Conference proceedings, web-based scientific databases such as publications on PubMed, Science direct, Springer, ACS, Scielo, PROTA, Google and Google scholar reporting ethnobotanical surveys and screening of natural products against Mycobacterium ulcerans. This study was limited to papers and documents published either in English or French reporting ethnopharmacological knowledge in BU treatment or pharmacological potency in vitro. This review covered the available literature up to December 2014.

RESULTS

The majority of reports originated from the three most affected West African countries (Cote d'Ivoire, Ghana and Benin). Though, 98 plant species belonging to 48 families have been identified as having anti-BU use, many have received no or little attention. Most of the pharmacological studies were performed only on 54 species. To a lesser extent, ethnopharmacological knowledge was validated in vitro for only 13 species. Of those, seven species including Ricinus comminus, Cyperus cyperoides (cited as Mariscus alternifolius), Nicotiana tabacum, Mangifera indica, Solanum rugosum, Carica papaya, and Moringa oleifera demonstrated efficacy in hospitalised BU patients. Four isolated and characterized compounds were reported to have moderate bioactivity in vitro against M. ulcerans.

CONCLUSIONS

This review compiles for the first time ethnopharmacologically useful plants against BU. The phamacological potential of 13 of them has been demonstrated in vitro and support BU evidence-based traditional medicines. In addition, 7 species showed activity in BU patients and have emerged as a promising source of the traditional medicine for treatment of BU. Yet, further safety and efficacy study should be initiated prior any approval as alternative therapy. Overall, a huge gap in knowledge appeared, suggesting further well-planned and detailed investigations of the in vitro, in vivo, and safety properties of the claimed anti-BU plants. Therefore, plants with medicinal potential should be scrutinized for biologically active compounds, using bioassay-guided fractionation approach to provide new insights to find novel therapeutics for BU control.

Internet claims on dietary and herbal supplements in advanced nephropathy: truth or myth

BACKGROUND

The use of complementary/alternative medicine has garnered rising interest in recent years. Natural products including herbs, vitamins, and minerals are the most popularly consumed. The Internet is a ubiquitous source of information/market for these supplements.

AIM

To systematically evaluate the dietary and herbal supplement recommended for patients with CKD and ESRD on the Internet, and try to distinguish between the claim of the manufacturer and proven scientific data.

METHODS

A questionnaire assessing each website was formulated. Each product ingredient was recorded in the questionnaire by two independent reviewers and statistically analyzed.

RESULTS

Of the 184 websites, 28% claimed to decrease CKD progression, 60% did not advise to consult a doctor before taking the supplement, and >90% did not mention any potential drug interaction, disease interaction, or caution in use during pregnancy or in children. The ten common plant ingredients claiming to be beneficial in kidney diseases were uva ursi, dandelion, parsley, corn silk, juniper, celery, buchu, horsetail, marshmallow, and stinging nettle. In contrast to their claims, these substances were not adequately studied in humans. The available animal studies showed detrimental effects and potential drug interactions with commonly used medications in the CKD/ESRD population.

CONCLUSIONS

Nephrologists need to be cognizant of the lack of substantiated proven benefits of these substances and of the potential adverse effects in the animal models that can translate to the patients. Most importantly, the policy needs to change regarding the regulation of these products to prevent patient harm and misinformation.

Corn silk maysin induces apoptotic cell death in PC-3 prostate cancer cells via mitochondria-dependent pathway

AIMS

Despite recent advances in prostate cancer diagnostics and therapeutics, the overall survival rate still remains low. This study was aimed to assess potential anti-cancer activity of maysin, a major flavonoid of corn silk (CS, Zea mays L.), in androgen-independent human prostate cancer cells (PC-3).

MAIN METHODS

Maysin was isolated from CS of Kwangpyeongok, a Korean hybrid corn, via methanol extraction and preparative C18 reverse phase column chromatography. Maysin cytotoxicity was determined by either monitoring cell viability in various cancer cell lines by MTT assay or morphological changes. Apoptotic cell death was assessed by annexin V-FITC/PI double staining, depolarization of mitochondrial membrane potential (MMP), expression levels of Bcl-2 and pro-caspase-3 and by terminal transferase mediated dUTP-fluorescein nick end labeling (TUNEL) staining. Underlying mechanism in maysin-induced apoptosis of PC-3 cells was explored by evaluating its effects on Akt and ERK pathway.

KEY FINDINGS

Maysin dose-dependently reduced the PC-3 cell viability, with an 87% reduction at 200 μg/ml. Maysin treatment significantly induced apoptotic cell death, DNA fragmentation, depolarization of MMP, and reduction in Bcl-2 and pro-caspase-3 expression levels. Maysin also significantly attenuated phosphorylation of Akt and ERK. A combined treatment with maysin and other known anti-cancer agents, including 5-FU, etoposide, cisplatin, or camptothecin, synergistically enhanced PC-3 cell death.

SIGNIFICANCE

These results suggested for the first time that maysin inhibits the PC-3 cancer cell growth via stimulation of mitochondria-dependent apoptotic cell death and may have a strong therapeutic potential for the treatment of either chemo-resistant or androgen-independent human prostate cancer.

Influence of variety and harvest maturity on phytochemical content in corn silk

Corn silk has been used as a traditional herb in Asia. The objective of this study was to evaluate variability in phytochemicals in corn varieties at three maturity stages of corn silk. Ten vegetable corn varieties were evaluated in a completely randomized design with three replications. Data were recorded for total phenolic (TPC), total flavonoids (TFC), total anthocyanin (TAC) and antioxidant activity (AA) by DPPH free-radical-scavenging assays. Differences among corn varieties were observed for all parameters at all maturity stages, and the interactions between maturity stage and corn variety were significant. TPC and TAC were highest at the milky stage, whereas TFC and AA were highest at the silking stage. TPC, TFC and AA were highest in super sweet corn and white corn at the silking stage. PWC5 variety of purple waxy corn at the milky stage had the highest values for all parameters, and it is useful for further development of functional food products.

Evaluation of a crataegus-based multiherb formula for dyslipidemia: a randomized, double-blind, placebo-controlled clinical trial

Background. We for the first time examined the effects of a multiherb formula containing Crataegus pinnatifida (1 g daily), Alisma orientalis, Stigma maydis, Ganoderma lucidum, Polygonum multiflorum, and Morus alba on plasma lipid and glucose levels in Chinese patients with dyslipidemia. Methods. In this randomized, double-blind, placebo-controlled study, 42 patients were randomized at a ratio of 1 : 1 to receive the herbal formula or placebo for 12 weeks and 40 patients completed the study. Lipid profiles, glucose, glycated haemoglobin (HbA1c), and laboratory safety parameters were performed before and after treatment. Results. The difference in the changes in low-density lipoprotein cholesterol (LDL-C) levels between placebo and active treatment (-9%) was significantly (P < 0.05) better with active treatment. HbA1c levels significantly decreased by -3.9% in the active treatment group, but the change was not significantly different from that with placebo (-1.1%) (P = 0.098). There were no apparent adverse effects or changes in laboratory safety parameters with either treatment. Conclusions. The multiherb formula had mild beneficial effects on plasma LDL-C after 12-weeks treatment in subjects with dyslipidemia without any noticeable adverse effects.

Inhibitory effect of corn silk on skin pigmentation

In this study, the inhibitory effect of corn silk on melanin production was evaluated. This study was performed to investigate the inhibitory effect of corn silk on melanin production in Melan-A cells by measuring melanin production and protein expression. The corn silk extract applied on Melan-A cells at a concentration of 100 ppm decreased melanin production by 37.2% without cytotoxicity. This was a better result than arbutin, a positive whitening agent, which exhibited a 26.8% melanin production inhibitory effect at the same concentration. The corn silk extract did not suppress tyrosinase activity but greatly reduced the expression of tyrosinase in Melan-A cells. In addition, corn silk extract was applied to the human face with hyperpigmentation, and skin color was measured to examine the degree of skin pigment reduction. The application of corn silk extract on faces with hyperpigmentation significantly reduced skin pigmentation without abnormal reactions. Based on the results above, corn silk has good prospects for use as a material for suppressing skin pigmentation.