Commercial Herbal Tea Research Articles

Antioxidant Activity of Herbal Tea Processed from Pineapple by-Product

The aim of this research is to examine the production of herbal tea from pineapple by-products by comparing the quality of non-edible pineapple by-products such as white cork, the core, and the leaves that are stuck to the cork. The samples were dried at various temperatures (60 and 70 °C) and measured for their antioxidant activity. The result indicated that drying temperature at 60 °C for 6 hours was determined to be the optimum condition. Due to the total flavonoids content, total phenolic content, and antioxidation activity being considerably greater than at 70 °C for 5 hours (p£0.05), when comparing the quality of the pineapple by-products after the drying, it was found that 100% of cork (white) is the most suitable option for herbal tea production with the flavonoid content, the phenolic content, and antioxidation activity being higher than the leaves that are stuck to the cork and the core with statistical significance (p£0.05). However, the herbal tea from pineapple by-product turned out to be low quality in comparison with commercial herbal tea products (p£0.05).

Identification of a new species and three new records of Chaetomiaceae associated with commercial herbal teas in northern Thailand

This study aimed to identify fungi associated with commercial herbal teas from local markets in Chiang Rai and Chiang Mai, Thailand. A new species, Arcopilus albae was isolated from mulberry leaf tea and identified based on evidence from molecular phylogenetic analysis. Phylogenetic analysis of a combined ITS, LSU, TUB2, and RPB2 dataset indicated that the new species is a distinct taxon with high statistical support. Furthermore, two isolates of Canariomyces arenarium and three isolates of Chaetomium globosum are described as new host records from five different commercial herbal teas (black and red goji berries, chrysanthemum flower, mulberry leaf, and stevia leaf). One isolate of Ch. rectangulare is described as a new host record from black goji berry and a new geographical record from northern Thailand. This study provides additional collections of fungi associated with dried commercial herbal tea products from local markets in the North of Thailand.

Effects of herbal tea (Platostoma palustre) on the Hyperlipidemia in vivo

Effects of herbal tea (Platostoma palustre) on the Hyperlipidemia in vivo

Analysis of the components of commercially traditional herbal tea (Platostoma palustre) in Taiwan

Platostoma palustre jelly is a traditional food. It has been used as folk medicine and is effective against heat-shock, hypertension and diabetes. Therefore, the aim of this study was want to analyze the components of commercially traditional herbal tea (P. palustre) in Taiwan. The commercial herbal tea (P. palustre) was kindly provided by Yueta Agricultural Biotechnology Inc. The detection methods of the components of commercially traditional herbal tea (P. palustre) were followed the analysis protocols in Taiwan Herbal Pharmacopeia (IV). The levels of chlorogenic acid, rosmarinic acid, caffeic acid, and rutin were detected via using high-performance liquid chromatography / photodiode array detector (HPLC-PDA). The level of astragaloside was detected by using high-performance liquid chromatography / evaporative light scattering detectors (HPLC-ELSD). In this analysis, the levels of chlorogenic acid, astragaloside, and rutin were not detected. The levels of rosmarinic acid and caffeic acid were 46.96 μg/mL and 29.29 μg/mL, respectively. Taken all results together, the components of commercially traditional herbal tea (P. palustre) were detected via HPLC-PDA and HPLC-ELSD. The major components of commercially traditional herbal tea (P. palustre) were rosmarinic acid and caffeic acid. Based on the results of this assay, it is speculated that the herbal tea has the functional properties that are considerable potential for physiological function regulations.

Effects of herbal tea (Platostoma palustre) on blood glucose regulation in vivo

Platostoma palustre jelly is a traditional food. Platostoma palustre has been used as folk medicine and is effective against heat-shock, hypertension and diabetes. Therefore, the aim of in vivo study was to determine the effects of herbal tea (Platostoma palustre) on blood glucose regulation. The commercial herbal tea (Platostoma palustre) was kindly provided by Yueta Agricultural Biotechnology Inc. Adult male 18 Institute of Cancer Research (ICR) mice [8 weeks old; body weight (BW) between 31-33 g] with specific pathogen-free conditions were used for this study. All ICR mice were divided respectively the normal control group (n = 6), the negative control group (n = 6), and the herbal tea group (n = 6). The ICR mice (the negative control group and the herbal tea group) were intraperitoneally injected with streptozotocin (65 mg/kg BW) and nicotinamide (230 mg/kg BW) for inducing the symptoms of hyperglycemia. In the herbal tea group, the herbal tea (10 mL/kg BW) was administrated to ICR mice by gavage. To monitor the blood glucose levels in ICR mice, blood was obtained from the tail of ICR mice, and blood glucose levels were determined using the external glucometer. Blood glucose measurements were conducted once in ICR mice before the experiment and were detected once per month after the experiment. Additionally, the change of ICR mice’ BW, the blood glucose of ICR mice, and the observation of ICR mice’ behavior were monitored and detected during the experiment. The results of this experiment showed · Weight change: the weight gain of the negative control group and the herbal tea group were significantly lower than those of the normal control group and there was no significant difference between the negative control group and the herbal tea group. · Fasting blood glucose and postprandial blood glucose: the fasting blood glucose of the negative control group was significantly higher than that of the normal control group, while the herbal tea group had a tendency to lower the fasting blood glucose, but there was no significant difference compared with the negative control group. The postprandial blood glucose level results showed that the negative control group was significantly higher than the normal control group. The postprandial blood glucose level of the herbal tea group was between the normal control group and the negative control group at the 4th week administration with the herbal tea. At the 8th week administration with the herbal tea, there was a significant difference compared with the negative control group. · Oral glucose tolerance test (OGTT): 4 to 12 weeks after hyperglycemia was induced, the blood glucose levels of the negative control group at each OGTT test point were significantly higher than those of the normal control group. The blood glucose level at the test point tended to decrease, but there was no significant difference from the negative control group. By calculating the area under the OGTT curve, it was found that the area under the curve of the negative control group was significantly higher than that of the normal control group, while the results of the herbal tea group at the 8th and 12th weeks were significantly lower than those of the negative control group. Taken all results together, the hyperglycemia was successfully induced in the experimental ICR mice. After administrating with the herbal tea, the fasting blood glucose level of the ICR mice tended to improve. In addition, a significant improvement was seen in the results of postprandial blood sugar and oral glucose tolerance test effectiveness. Therefore, based on the results of this experiment, it is speculated that drinking the herbal tea for 3 months has considerable potential for blood glucose regulation, which can be used as the basis for the development of related products of the herbal tea in the future.

PHYTOCHEMICAL AND ORGANOLEPTIC CHARACTERISTIC OF Sterculia quadrifida R.Br. TREE BARK HERBAL TEA

Sterculia quadrifida R.Br. Bark decoction is used to treat hepatitis and consumed as a tonic by Timorese in the East Nusa Tenggara Province, Indonesia. Raw herbal materials are susceptible to fungi contamination, have limitations in transportation, and have low economic value. Processing the bark into powder packed in tea bags is expected to overcome these obstacles. Stevia, ginger, and mint leaves are herbs often added to herbal drink formulas. This study aimed to evaluate the antioxidant capacity, total flavonoid content (TFC), total phenol content (TPC), physicochemical properties, and sensory properties of six formulas, namely: (F1) pure S. quadrifida bark; (F2) bark of S. quadrifida and leaves of stevia; (F3) stem bark of S. quadrifida and ginger; (F4) bark of S. quadrifida, stevia, and ginger; (F5) bark of S. quadrifida and mint leaves; (F6) bark of S. quadrifida, stevia, and mint. Total phenolic content was measured using the Folin-Ciocalteu method, and total flavonoids were determined using the AICI3 method. Antioxidant activity was measured using the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) method. The TPC of S. quadrifida tea ranged from 14.09±0.7 to 68.20±0.95% Gallic Acid Equivalent (GAE), and the TFC ranged from 0.03±0.005 to 0.09±0.004% QE. The Ascorbic acid Equivalent Antioxidant Capacity (AEAC) of F1, F2, F5, and F6 were insignificantly different. F1 contained the highest levels of antioxidants (1,044.3±28.48 ppm Ascorbic Acid Equivalent (AAE)). Formulas with the addition of stevia, mint, and ginger showed weaker antioxidant activity than pure S. quadrifida. F1 and F2 have the potential to be developed as commercial herbal teas

Polycyclic Aromatic Hydrocarbons (PAHS) Levels and Toxicity in Herbal Teas Marketed in Malaysia using Quechers and GC-FID

In line with the growing health trend in Malaysia, more consumers drink herbal tea for medicinal benefits. However, herbal tea products could be contaminated with polycyclic aromatic hydrocarbons (PAHs) from various production sources. There is a little study focused on the detection of PAHs in herbal tea species distributed in Malaysia. This study was performed to investigate PAHs content and toxicity in selected commercial herbal teas in Malaysia. A total of seven different Malaysian herbal tea samples were extracted using QuEChERS extraction method and the contamination level of PAHs were evaluated using gas chromatography (GC) with a flame ionization detector (FID). The total content of 10 PAHs (∑10PAHs) in the herbal tea samples ranged from 2.53 to 9.39 µg/kg. Acenaphthene, fluorene, phenanthrene and anthracene were the most abundant compounds with 53% contribution of all PAHs content. All tested herbal teas species showed low toxic equivalency (TEQ) values ranging from 0.0027 to 0.1148. The least contaminated samples were Strobilanthes crispus, Senna alata, Orthosiphon aristatus, Clinacanthus nutans, and Stevia rebaudiana.

The road to commercialisation of an unutilised Cyclopia species for herbal tea production – the case of Cyclopia pubescens

• C. pubescens was shown to be suitable for production of honeybush herbal tea. • Its sensory profile is similar to that of commercially-cultivated C. subternata . • Other quality parameters were similar to that of C. subternata and C. genistoides . • High-temperature oxidation reduces the xanthone content more than 70%. Cyclopia pubescens is an unutilised species that could potentially be used for production of honeybush tea, if general quality criteria for the herbal tea product could be met. This species is at risk of extinction in the wild, but if suitable for production of honeybush herbal tea, its cultivation could be stimulated. Cyclopia pubescens shoots were used to produce conventional (oxidised) honeybush tea and its quality parameters for the infusion were compared with those of the commercially-cultivated Cyclopia species, C. subternata and C. genistoides . Oxidised C. pubescens had a similar sensory profile to that of C. subternata, displaying ‘woody’, ‘fynbos-floral’ ‘fynbos-sweet’ and ‘sweet spice’ aromas and a slightly sweet taste. The soluble solids concentration, colour and turbidity of the infusions, prepared from the herbal teas of the three species, were similar. The high-temperature oxidation process, essential for the development of the sought-after sensory profile of honeybush tea, reduced the phenolic concentration of the C. pubescens infusions, in particular, the concentration of mangiferin and isomangiferin decreased > 70%. Despite this reduction, C. pubescens infusions would contribute ≥ 8 mg/L to the dietary intake of each of these xanthones. Cyclopia pubescens , thus, passed the first hurdle for commercial herbal tea production, but cultivation would be required as wild-harvesting of this species is not an option.

Effects of Platostoma palustre ethanolic extracts and commercial herbal tea on the cell viability of colorectal cancer cells

Platostoma palustre jelly is a traditional food. Platostoma palustre has been used as folk medicine and is effective against heat-shock, hypertension and diabetes. Therefore, the aim of this study was to determine the effects of ethanolic extracts and commercial herbal tea of Platostoma palustre in inhibiting colorectal cancer cell viability. The ethanolic extracts of Platostoma palustre by using 90% ethanol for extraction. In this study, 2-fold serial dilution of 100 mg/mL Platostoma palustre extracts were applied. On other hand, the same dilution fold was also performed for 100% commercial herbal tea with Platostoma palustre. Additionally, CT-26 and HT-29 colorectal cancer cell lines were also used in this study. After co-culturing for 24 hours, the cell viability of CT-26 and HT-29 colorectal cancer cell lines were performed by using 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. According to these data, the 1.56-100 mg/mL Platostoma palustre extracts possessed the significant inhibition effects of CT-26 colorectal cancer cell viability. The 3.13-100% commercial herbal tea with Platostoma palustre possessed the significant inhibition effects of CT-26 colorectal cancer cell viability. The 6.25-100 mg/mL Platostoma palustre extracts possessed the significant inhibition effects of HT-29 colorectal cancer cell viability. The 25-100% commercial herbal tea with Platostoma palustre possessed the significant inhibition effects of HT-29 colorectal cancer cell viability. However, the 0.39-3.13 mg/mL Platostoma palustre extracts possessed the significant promoting effects of HT-29 colorectal cancer cell viability. The 0.39-12.5% commercial herbal tea with Platostoma palustre also possessed the significant promoting effects of HT-29 colorectal cancer cell viability. Comparison of CT-26 and HT-29 cell lines was on the cell viability after Platostoma palustre ethanolic extracts and commercial herbal tea treatments, CT-26 cell line was better sensitive than HT-29 cell line on the inhibition of cell viability after treatment of Platostoma palustre ethanolic extracts and the commercial herbal tea. Taken these results together, Platostoma palustre ethanolic extracts and commercial herbal tea may have a potential for inhibiting the growth of colorectal cancer cells.

Effects of Platostoma palustre ethanolic extracts and commercial herbal tea on the cell viability of colorectal cancer cells

Effects of Platostoma palustre ethanolic extracts and commercial herbal tea on the cell viability of colorectal cancer cells

Health risk assessment of toxic metals and toxigenic fungi in commercial herbal tea samples from Belgrade, Serbia

This study aimed to: (i) determine the content of toxic metals and toxigenic fungi in 14 commercial herbal tea samples from the market of Belgrade, Serbia; and (ii) assess their risk to human health. After the microwave digestion (HNO3/H2O2, 7:1,v/v), toxic metal content was determined by graphite furnace atomic absorption spectroscopy (GF-AAS). The health risk as a result of Cd, Pb, As, Mn, Ni, and Cr exposure via herbal tea intake was assessed through estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI). Fungi isolated from the tested herbal tea samples were identified on the basis of colony morphology and microscopic characteristics of reproductive structures. Toxic metals concentration in herbal tea samples for Cd, Pb, As, Mn, Ni and Cr ranged 0.04-0.93, 0.09-2.54, 0.03-0.77, 1.82-651.04, 0.97-9.01, 0.49-3.47 mg/kg of dried plant material, respectively. Values of THQ for investigated toxic metals and HI were below 1, indicating the absence of human health risk. All 14 samples of the tested herbal teas were contaminated with fungi, while total count of cultivable fungi in each sample did not exceed national standards (105 CFU/g). Presence of 23 morphologically different isolates suggested moderate fungal diversity of the samples, while the highest isolation frequency (IF) of 100% was documented for Penicillium spp. and Aspergillus spp. The obtained risk assessment results suggest that all the tested samples are safe for human health regarding the toxic metal and fungal content and provide an important basis for understanding the potential risks of toxic metals and toxigenic fungi intake via commercially available herbal teas.

An Ethnobotanical Study on Qīng-Căo-Chá Tea in Taiwan.

Herbal tea, a beverage prepared from a variety of plant materials excluding the leaves of the tea plant Camellia sinensis (L.) Kuntze of the family Theaceae, for a long time, has been consumed by most Chinese people for preventive and/or therapeutic health care. Usually, it is brewed or prepared as a decoction of local plants in water. The qīng-căo-chá tea, a commercial herbal tea, is the most common among many differently formulated herbal teas in Taiwan. For hundreds of years, qīng-căo-chá tea has played an important role in the prevention and treatment of diseases associated with the environmental conditions in Taiwan. However, research studies in this field have been insufficient. The raw material formulas of qīng-căo-chá tea have always been passed down from “masters” to “apprentices.” Hence, there is no systematic collation or record, and, therefore, there is a need to assess and confirm the composition, safety, and effectiveness of the raw materials. This study aimed to document the uses of Taiwan's qīng-căo-chá tea through a semi-structured interview survey and investigate the background of traditional practitioners, tea compositions, and plant origins and uses. This will improve our understanding of the knowledge inherited by the practitioners and the theoretical basis of the medicinal uses of these teas. In our field investigation, we visited 86 shops and assessed 71 raw ingredients of qīng-căo-chá tea. A semi-structured questionnaire was used to conduct the interviews. During the interviews, in addition to written records, audio and video recordings were made, and photographs were taken with the permission of the interviewees. The qīng-căo-chá raw materials have long been used as herbal teas, although more research should clarify their efficacy and safety. Traditional sellers of qīng-căo-chá tea were mainly males, and most shops have been in operation for more than 71 years. Some of the raw materials were derived from multiple sources, including different plants, and were often mixed without any safety concerns. To our knowledge, this is the first systematic ethnobotanical study on qīng-căo-chá tea that assesses and confirms its herbal ingredients. Our study represents a reference for herbal teas in Taiwan that can be used by the public and regulatory agencies.

Topic: chemical compositions and mineral content of four selected South African herbal teas and the synergistic response of combined teas

PurposeThe present study was carried out to determine (1) essential minerals, total polyphenols, total flavonoids, moisture and ash of four selected South African herbal teas and (2) the effect of blending bush tea with other known commercial herbal teas.Design/methodology/approachThe method used to determine moisture and ash contents followed that of the Association of Official Analytical Chemists (AOAC). Nine minerals were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). The total phenolic and flavonoid contents were determined by Folin–Ciocalteu assay and aluminum chloride colorimetric assay, respectively.FindingsThe results of the study demonstrated that bush tea had a high ash content of 8.01% and special tea (9.23%), while honeybush (1.96%) and rooibos tea (2.17%) exhibited a low ash percentage. The mineral content was higher in bush tea and special tea than in rooibos tea and honeybush tea except for sodium, which was higher in rooibos tea. The blending of bush tea with special tea improved its potassium content from 22,937.00 mg/kg to 23,379.20 mg/kg. Blending bush tea with rooibos tea at a ratio of 25:75 increased the flavonoid content to 12.21 µg/mL.Research limitations/implicationsThe results of the nutrients composition cannot be generalized as it is influenced by other factors such as soil type and seasons.Social implicationsIncreasing the commercialization of indigenous teas.Originality/valueThe results of the study suggest that bush tea and special tea are nutritionally comparable with South African commercial herbal teas. Thus, the consideration for commercialization of these teas is crucial.

Anti-diabetic and anti-proliferative activities of herbal teas, Athrixia phylicoides DC and Monsonia burkeana Planch. ex Harv, indigenous to South Africa

PurposeThe purpose of this paper is to investigate the health and medicinal importance of bush tea (Athrixia phylicoides DC) and special tea (Monsonia burkeana Planch. ex Harv), two of Southern African indigenous herbal teas.Design/methodology/approachThe two herbal teas, A. phylicoides and M. burkeana were extracted individually and in combined ratios for analysis. The phenolic content was determined and the different phenolic compounds were identified using thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The anti-diabetic activity of the teas was determined by evaluating the inhibition of both α-amylase and α-glucosidase in vitro. The anti-proliferative activity was measured on human cervical cancer (HeLa) cell line using the MTT (3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium) assay.FindingsGallic acid, chlorogenic acid and quercetin were identified to be present in significant quantities by TLC. The HPLC quantified the presence of catechin (1.567 mg/g) and chlorogenic acid (1.862 mg/g) in special tea while chlorogenic acid (1.288 mg/g) was present in bush tea. Bush tea and special tea expressed significant levels of phenolic content and high antioxidant activities. Special tea (S100) expressed high inhibition of α-amylase, α-glucosidase and HeLa cell line proliferation when compared to bush tea (B100).Originality/valueBoth bush tea and special tea could provide an alternative for treatment and management of both diabetes and cervical cancer. However, future studies are needed to investigate their synergistic effect with a wide range of other commercial herbal teas.

DNA Barcoding for the Identification of Phyllanthus Taxa Used Medicinally in Brazil.

Plants of the genus Phyllanthus, principally Phyllanthus amarus, Phyllanthus urinaria, Phyllanthus niruri, and Phyllanthus tenellus, are used in Brazilian folk medicine to treat kidney stones as well as other ailments, where the latter two species are listed in the Brazilian Pharmacopeia as quebra-pedra (stone-breaker). However, only P. niruri has been shown to be effective in a clinical setting. Nuclear ribosomal internal transcribed spacer (ITS1 - 5.8S rRNA-ITS2), internal transcribed spacer 2, and chloroplasts rbcL, matK, psbA-trnH, trnL, and trnL-trnF were screened for their potential as DNA barcodes for the identification of 48 Phyllanthus taxa in Brazilian medicinal plant germplasm banks and in "living pharmacies". The markers were also tested for their ability to validate four commercial herbal teas labelled as quebra-pedra. Using the criterion of high clade posterior probability in Bayesian phylogenetic analysis, the internal transcribed spacer, internal transcribed spacer 2, and chloroplast matK, psbA-trnH, trnL, and trnL-trnF markers all reliably differentiated the four Phyllanthus species, with the internal transcribed spacer and matK possessing the additional advantage that the genus is well represented for these markers in the Genbank database. However, in the case of rbcL, posterior probability for some clades was low and while P. amarus and P. tenellus formed monophyletic groups, P. niruri and P. urinaria accessions could not be reliably distinguished with this marker. Packaged dried quebra-pedra herb from three Brazilian commercial suppliers comprised P. tenellus, but one sample was also found to be mixed with alfalfa (Medicago sativa). An herb marketed as quebra-pedra from a fourth supplier was found to be composed of a mixture of Desmodium barbatum and P. niruri.

Antioxidant Potential of Herbal Tea from Rhododendron anthopogon D. Don and Hippophae salicifolia D. Don

Herbal tea prepared from leaves and flowers of Rhododendron anthopogon D. Don. and from leaves and pulp of dried fruits Hippophae salicifolia D. Don was tested for its antioxidant potential. Both tested plant species were proven good candidates for commercial Herbal Teas in terms of antioxidant potentials.

Determination of metalloid, metallic and mineral elements in herbal teas. Risk assessment for the consumers

In spite of herbal teas having potential health benefits, the presence of metal contamination in these products has raised public health concerns. An analytical method for the determination of metallic elements (Hg, Pb, Cr and Cd), metalloids (As) and mineral compounds (Fe, Mn, Cu, and Zn) in herbal teas has been validated. Levels of these elements were determined in 220 samples of herbal teas purchased from supermarkets (which marketed own and leading brands), street herbal markets and herbal stores. In a further step, potential human health risks for the consumers were assessed. Cd in thyme and chamomile from some selling points exceeded the maximum permissible limit set by the WHO and the European Pharmacopoeia for herbal medicines or herbal drugs (also referred to as herbal teas). Regarding mineral elements, the highest Mn levels were found in red and green tea among all plant studied, in line with other studies. However, the estimated daily intake of metal/metalloid and mineral elements from the commercial herbal teas studied, considering the percentage of solubilization in infusions and the bioavailability of each compound, do not pose human health risks.

Quality Control of Herbal Products in the Egyptian Market Used for Some Gastro-Intestinal Tract Disorders

Objectives: This study aimed to evaluate the quality of three commercial herbal tea products present in the Egyptian market; commercial herbal Calm (1), commercial herbal Intestinal (2) and commercial herbal Anti diarrhea (3) in comparison with three prepared standard mixtures. Methods: Quality control of the three commercial herbal products and prepared standard mixtures was conducted through microscopical identification of their diagnostic elements, determination of pharmacopeial constants, and detection of contaminations. Analysis of essential oil content and estimation of the main active constituents were performed using GC/MS and HPLC respectively. Antimicrobial activity, toxicological study, anti-diabetic, anti-inflammatory and antioxidant activities were carried out on 80% methanolic extract of the three commercial herbal teas in comparison with corresponding standard mixtures. Results: Quality control of the three commercial herbal products revealed that some of the herbs are exhausted; some of the products are adulterated with other species rather than those of the formula; however, the three commercial herbal products are safe, free from aflatoxin, pesticides and heavy metals. They are active as antimicrobial, anti-diabetic, anti-inflammatory and antioxidant. Conclusion: The assessed commercial herbal products that are used in the Egyptian market for some gastro-intestinal tract disorders have proven their effectiveness as antimicrobial, anti-diabetic, anti-inflammatory and antioxidant drugs, which can be subjected for further clinical trials.

Novel reduced graphene oxide-glycol chitosan nanohybrid for the assembly of an amperometric enzyme biosensor for phenols.

A novel water-soluble graphene derivative was prepared from graphene oxide via a two-step modification approach. Graphene oxide was first functionalised with reactive epoxy groups by covalent modification with (3-glycidyloxypropyl)trimethoxysilane and further cross-linked with glycol chitosan. This graphene derivative was characterized using different microscopy and physicochemical methods and employed as a coating material for a glassy carbon electrode. The nanostructured surface was used as a support for the covalent immobilization of the enzyme laccase through cross-linking with glutaraldehyde. The enzyme electrode was tested for the amperometric detection of different phenolic compounds, which displayed excellent analytical behaviour toward catechol with a linear range of response from 200 nM to 15 μM, sensitivity of 93 mA M(-1) cm(-2), and low detection limit of 76 nM. The enzyme biosensor showed high stability when stored at 4 °C under dry conditions and was successfully employed to quantify the total phenolic compounds in commercial herbal tea samples.

Determination of Estragole in Fennel Herbal Teas by HS-SPME and GC–MS

Estragole, a volatile phenylpropanoid contained in a variety of edible herbs, has been demonstrated to be genotoxic and carcinogenic, and its addition as a flavoring substance to foodstuffs has been banned by the regulatory bodies of the European Union. Fast and accurate analytical methods for its determination in herbs are thus necessary to assess the dietary exposure of this substance in humans and, in particular, to sensitive groups. In the present study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS) was applied for determination of estragole in infusions from different widely used commercial herbal teas based on Foeniculum vulgare (fennel) seeds. The optimized HS-SPME extraction conditions involved the use of a polydimethylsiloxane fiber exposed to the herbal infusion for 20 min at 50°C followed by GC–MS analysis. The method was fully validated for linearity, sensitivity, accuracy, and precision and applied to real samples; the level of estragole in infusions of commercial fennel seed teas was found to be within 50–250 µ`−1.