Investigating the potential for toxicity from long-term use of the herbal products, goldenseal and milk thistle

Novel Strategies Enhancing Bioavailability and Therapeutical Potential of Silibinin for Treatment of Liver Disorders

Silibinin, a bioactive component found in milk thistle extract (Silybum marianum), is known to have significant therapeutic potential in the treatment of various liver diseases. It is considered a key element of silymarin, which is traditionally used to support liver function. The main mechanisms of action of silibinin are attributed to its antioxidant properties protecting liver cells from damage caused by free radicals. Experimental studies conducted in vitro and in vivo have confirmed its ability to inhibit inflammatory and fibrotic processes, as well as promote the regeneration of damaged liver tissue. Therefore, silibinin represents a promising tool for the treatment of liver diseases. Since the silibinin molecule is insoluble in water and has poor bioavailability in vivo, new perspectives on solving this problem are being sought. The two most promising approaches are the water-soluble derivative silibinin-C-2',3-dihydrogen succinate, disodium salt, and the silibinin-phosphatidylcholine complex. Both drugs are currently under evaluation in liver disease clinical trials. Nevertheless, the mechanism underlying silibinin biological activity is still elusive and its more detailed understanding would undoubtedly increase its potential in the development of effective therapeutic strategies against liver diseases. This review is focused on the therapeutic potential of silibinin and its derivates, approaches to increase the bioavailability and the benefits in the treatment of liver diseases that have been achieved so far. The review discusses the relevant in vitro and in vivo studies that investigated the protective effects of silibinin in various forms of liver damage.

Antifibrotic effect of silymarin on arecoline-induced fibrosis in primary human buccal fibroblasts: an in silico and in vitro analysis

BACKGROUND

This study aimed to assess silymarin's anticancer and antifibrotic potential through in silico analysis and investigate its impact on in vitro arecoline-induced fibrosis in primary human buccal fibroblasts (HBF).

METHODS & RESULTS

The study utilized iGEMDOCK for molecular docking, evaluating nine bioflavonoids, and identified silymarin and baicalein as the top two compounds with the highest target affinity, followed by subsequent validation through a 100ns Molecular Dynamic Simulation demonstrating silymarin's stable behavior with Transforming Growth Factor Beta. HBF cell lines were developed from tissue samples obtained from patients undergoing third molar extraction. Arecoline, a known etiological factor in oral submucous fibrosis (OSMF), was employed to induce fibrogenesis in these HBFs. The inhibitory concentration (IC50) of arecoline was determined using the MTT assay, revealing dose-dependent cytotoxicity of HBFs to arecoline, with notable cytotoxicity observed at concentrations exceeding 50µM. Subsequently, the cytotoxicity of silymarin was assessed at 24 and 72 h, spanning concentrations from 5µM to 200µM, and an IC50 value of 143µM was determined. Real-time polymerase chain reaction (qPCR) was used to analyze the significant downregulation of key markers including collagen, epithelial-mesenchymal transition (EMT), stem cell, hypoxia, angiogenesis and stress markers in silymarin-treated arecoline-induced primary buccal fibroblast cells.

CONCLUSION

Silymarin effectively inhibited fibroblast proliferation and downregulated genes associated with cancer progression and EMT pathway, both of which are implicated in malignant transformation. To our knowledge, this study represents the first exploration of silymarin's potential as a novel therapeutic agent in an in vitro model of OSMF.

Albumin-Based Silibinin Nanocrystals Targeting Activated Hepatic Stellate Cells for Liver Fibrosis Therapy

Activated hepatic stellate cells (aHSCs) are critical during the development and progression of liver fibrosis. Once liver fibrosis occurs, aHSCs highly express secreted protein, acidic and rich in cysteine (SPARC), a typical albumin-binding protein. We designed a nano platform, silibinin albumin nanocrystals (SLB-HSA NCs), to target aHSCs for liver fibrosis therapy. The prepared SLB-HSA NCs showed uniform particle size distribution of approximately 60 nm with PDI < 0.15 and high loading efficiency up to 49.4%. Albumin coated on the surface of nanocrystals was demonstrated to increase cellular uptake by aHSCs through SPARC-mediated endocytosis. In addition, SLB-HSA NCs significantly improved the bioavailability compared with free SLB in pharmacokinetic study. Following tail-vein injection, SLB-HSA NCs were massively accumulated in the fibrotic liver and exhibited enhanced antifibrotic effects in hepatic fibrosis mice. Overall, our findings prove the great potential of SLB-HSA NCs in the targeted treatment of liver fibrosis.

Preparation and Characterization of Silymarin Gel: A Novel Topical Mucoadhesive Formulation for Potential Applicability in Oral Pathologies

Silybum marianum has been used for centuries by herbalists and physicians to treat different forms of liver diseases. It contains flavonoid, which has antioxidant, anti-inflammatory, antifibrotic and anticancer properties. The objective of this research was to develop a silymarin-based mucoadhesive gel for prolonged release in oral mucosa and to evaluate the same by using in vitro drug release kinetic models and ex vivo methods for drug permeation using chicken buccal mucosa. The mucoadhesive gel was formulated in different trials by varying the concentration of silymarin and polymer. Out of 10 formulation trials, the F10 optimized trial was characterized for in vitro physicochemical parameters such as pH, homogeneity, viscosity, stability, drug content, in vitro drug release, in vitro antioxidant assay and ex vivo permeation study. Trial 10 was chosen as the best trial formulation among the other trials and was marked as an optimal trial. The physicochemical properties observed were pH to be 6.4 ± 0.01, the gel free of lumps, spreadability of 23.75 ± 0.03 and drug content of 32.77 ± 0.20 mg/g. It had no physiological changes such as color shift or fluid exudate segregation after 6 months of storage at room temperature. In vitro drug release established the presence of a non-fickian mechanism and demonstrated dose-dependent antioxidant activity. Ex vivo findings indicated 21.97 ± 0.18% release, proving that the gel can permeate through the oral mucosal membrane. Our future research will concentrate on expanding the therapeutic scope by developing the formulation trial F10 to a nanoformulation and conducting clinical trials for its potential use in various oral diseases.

Silybin phytosome attenuates cerebral ischemia-reperfusion injury in rats by suppressing oxidative stress and reducing inflammatory response: In vivo and in silico approaches

The present study was aimed to develop silybin phytosome (SIBP) and evaluate its effectiveness against cerebral ischemia-reperfusion (CIR) injury in rats. Initially, SIBP was prepared and characterized with Fourier transform-infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Drug loading and entrapment efficiency of SIBP were also calculated. High-performance liquid chromatography was used to carry out bioavailability studies of SIBP. Adult Wistar rats were divided randomly into five groups. The CIR injury was induced after 14 days of pretreatment by occlusion of bilateral common carotid arteries for 30 min followed by 4 h of reperfusion. Biochemical estimation, histopathological studies, and in silico studies were carried out. Bioavailability studies revealed that SIB concentration was increased to twofolds in SIBP-treated rats. SIBP treatment significantly increases superoxide dismutase and glutathione levels while it decreases monoaldehyde, tumor necrosis factor-α (TNF-α), and interleukin 6 (IL-6) levels in both the hippocampus and cortex of the SIBP-treated CIR-injured rats. Histopathological studies reveal SIBP treatment alleviates cortex cell death and arrangement of CA1 neurons in CIR-injured rats. In silico studies against proteins (TNF-α and IL-6) involved in cerebral ischemia revealed that silybin (SIB) exhibits strong binding interaction with the target proteins when compared to thalidomide which was used as the positive control. Phytosome increase SIB bioavailability and SIBP treatment showed promising results when compared to treatment with SIB only. Based on our study, we conclude that phytosome is a suitable drug delivery agent to the brain for SIB as SIBP treatment was able to provide neuroprotective action against CIR injury.

The toxicologic pathology aspects of selected natural herbal products and related compounds

Herbal products have been in use for many years, but they are becoming more and more popular in recent years, and they are currently in widespread use throughout the world. In this review article we describe the histopathologic findings found after exposure to 12 dietary herbals in studies conducted in rodent model systems. Clear or some evidence for carcinogenic activity was seen with 6 herbals, with the liver being the most common organ affected. The intestine was affected by two herbals (aloe vera nondecolorized extract and senna), three had no clear evidence for carcinogenic activity and one was cardiotoxic (Ephedrine and Ephedra in combination with caffeine). Information from these studies can help to better understand potential target organs for further evaluation from exposure to various herbal products.

Metabolic Activation and Covalent Protein Binding of Berberrubine: Insight into the Underlying Mechanism Related to Its Hepatotoxicity

Introduction

Berberrubine (BRB), an isoquinoline alkaloid, is a major constituent of medicinal plants Coptis chinensis Franch or Phellodendron chinense Schneid. BRB exhibits various pharmacological activities, whereas exposure to BRB may cause toxicity in experimental animals.

Methods

In this study, we thoroughly investigated the liver injury induced by BRB in mice and rats. To explore the underlying mechanism, a study of the metabolic activation of BRB was conducted. Furthermore, covalent modifications of cysteine residues of proteins were observed in liver homogenate samples of animals after exposure to BRB, by application of an exhaustive proteolytic digestion method.

Results

It was demonstrated that BRB-induced hepatotoxicities in a time- and dose-dependent manner, based on the biochemical parameters ALT and AST. H&E stained histopathological examination showed the occurrence of obvious edema in liver of mice after intraperitoneal (i.p.) administration of BRB at a single dose of 100 mg/kg. Slight hepatotoxicity was also observed in rats given the same doses of BRB after six weeks of gavage. As a result, four GSH adducts derived from reactive metabolites of BRB were detected in microsomal incubations with BRB fortified with GSH as a trapping agent. Moreover, four cys-based adducts derived from reaction of electrophilic metabolites of BBR with proteins were found in livers.

Conclusion

These results suggested that the formation of protein adducts originating from metabolic activation of BRB could be a crucial factor of the mechanism of BRB-induced toxicities.

Goldenseal (Hydrastis canadensis L.) and its active constituents: A critical review of their efficacy and toxicological issues

Goldenseal (Hydrastis canadensis L.) is a medicinal plant widely used in various traditional systems of medicine and as a food supplement. It has been traditionally used by Native Americans as a coloring agent and as medicinal remedy for common diseases and conditions like wounds, digestive disorders, ulcers, skin and eye ailments, and cancer. Over the years, goldenseal has become a popular food supplement in the USA and other regions. The rhizome of this plant has been used for the treatment of a variety of diseases including, gastrointestinal disorders, ulcers, muscular debility, nervous prostration, constipation, skin and eye infections, cancer, among others. Berberine is one of the most bioactive alkaloid that has been identified in different parts of goldenseal. The goldenseal extract containing berberine showed numerous therapeutic effects such as antimicrobial, anti-inflammatory, hypolipidemic, hypoglycemic, antioxidant, neuroprotective (anti-Alzheimer's disease), cardioprotective, and gastrointestinal protective. Various research finding suggest the health promoting effects of goldenseal components and their extracts. However, few studies have also suggested the possible neurotoxic, hepatotoxic and phototoxic activities of goldenseal extract and its alkaloids. Thus, large randomized, double-blind clinical studies need to be conducted on goldenseal supplements and their main alkaloids to provide more evidence on the mechanisms responsible for the pharmaceutical activity, clinical efficacy and safety of these products. Thus, it is very important to review the scientific information about goldenseal to understand about the current scenario.

Antiviral Natural Products for Arbovirus Infections

Over the course of the last 50 years, the emergence of several arboviruses have resulted in countless outbreaks globally. With a high proportion of infections occurring in tropical and subtropical regions where arthropods tend to be abundant, Asia in particular is a region that is heavily affected by arboviral diseases caused by dengue, Japanese encephalitis, West Nile, Zika, and chikungunya viruses. Major gaps in protection against the most significant emerging arboviruses remains as there are currently no antivirals available, and vaccines are only available for some. A potential source of antiviral compounds could be discovered in natural products—such as vegetables, fruits, flowers, herbal plants, marine organisms and microorganisms—from which various compounds have been documented to exhibit antiviral activities and are expected to have good tolerability and minimal side effects. Polyphenols and plant extracts have been extensively studied for their antiviral properties against arboviruses and have demonstrated promising results. With an abundance of natural products to screen for new antiviral compounds, it is highly optimistic that natural products will continue to play an important role in contributing to antiviral drug development and in reducing the global infection burden of arboviruses.

Intestinal Permeability Study of Clinically Relevant Formulations of Silibinin in Caco-2 Cell Monolayers

An ever-growing number of preclinical studies have investigated the tumoricidal activity of the milk thistle flavonolignan silibinin. The clinical value of silibinin as a bona fide anti-cancer therapy, however, remains uncertain with respect to its bioavailability and blood⁻brain barrier (BBB) permeability. To shed some light on the absorption and bioavailability of silibinin, we utilized the Caco-2 cell monolayer model of human intestinal absorption to evaluate the permeation properties of three different formulations of silibinin: silibinin-meglumine, a water-soluble form of silibinin complexed with the amino-sugar meglumine; silibinin-phosphatidylcholine, the phytolipid delivery system Siliphos; and Eurosil85/Euromed, a milk thistle extract that is the active component of the nutraceutical Legasil with enhanced bioavailability. Our approach predicted differential mechanisms of transport and blood⁻brain barrier permeabilities between the silibinin formulations tested. Our assessment might provide valuable information about an idoneous silibinin formulation capable of reaching target cancer tissues and accounting for the observed clinical effects of silibinin, including a recently reported meaningful central nervous system activity against brain metastases.

Superior silybin bioavailability of silybin-phosphatidylcholine complex in oily-medium soft-gel capsules versus conventional silymarin tablets in healthy volunteers

BACKGROUND

Fibrosis is a response to chronic liver disease that results in excessive accumulation of extracellular matrix proteins and formation of scar tissue. Fibrosis represents a clinical challenge of worldwide significance. Several studies have demonstrated that many natural products and herbal medicines have activity against liver fibrosis, and extracts of milk thistle such as silymarin and silybin are the natural compounds most commonly prescribed for liver diseases. Therefore, we sought to assess and compare the pharmacokinetic properties and bioavailability of silybin-phosphatidylcholine complex in oily-medium soft-gel capsules and conventional silymarin tablets in healthy Mexican volunteers.

METHODS

We enrolled 23 healthy volunteers to participate in a prospective, balanced, blind, single-dose, two-way crossover study with a one-week washout period. Fasting participants received either 45 mg silybin-phosphatidylcholine complex or 70 mg silymarin to assess which formulation provided better bioavailability of silybin. Plasma was obtained and analysed for silybin concentration using a validated ultra-performance liquid chromatography-tandem mass spectroscopy method. Pharmacokinetic parameters were obtained by non-compartmental analysis and values were compared by analysis of variance for a crossover design. Ratios of maximum plasma drug concentration and area under the curve (AUC) were obtained and 90% confidence intervals were calculated.

RESULTS

The 23 healthy subjects (11 women, 12 men) who participated in the study were aged 22-31 years old (average: 28), average weight 64.8 kg, height 1.65 m and body mass index 23.5 kg/m². Plasma levels of silybin were higher after the administration of silybin-phosphatidylcholine complex capsules compared with that after conventional silymarin tablets (P <  0.0001).

CONCLUSIONS

The silybin-phosphatidylcholine complex in oily-medium soft-gel capsules seems to provide superior bioavailability. However, clinical studies must be performed to demonstrate its clinical relevance in the treatment of liver diseases.

TRIAL REGISTRATION

NCT03440164 ; registered on November 11, 2016.

Finding the bad actor: Challenges in identifying toxic constituents in botanical dietary supplements

Botanical-derived dietary supplements have widespread use in the general population. The complex and variable nature of botanical ingredients and reports of adverse responses have led to concern for negative human health impacts following consumption of these products. Toxicity testing of the vast number of available products, formulations, and combinations is not feasible due to the time and resource intensive nature of comprehensive testing. Methods are needed to assess the safety of a large number of products via more efficient frameworks. Identification of toxicologically-active constituents is one approach being used, with many advantages toward product regulation. Bioassay-guided fractionation (BGF) is the leading approach used to identify biologically-active constituents. Most BGF studies with botanicals focus on identifying pharmacologically-active constituents for drug discovery or botanical efficacy research. Here, we explore BGF in a toxicological context, drawing from both efficacy and poisonous plant research. Limitations of BGF, including loss of mixture activity and bias toward abundant constituents, and recent advancements in the field (e.g., biochemometrics) are discussed from a toxicological perspective. Identification of active constituents will allow better monitoring of market products for known toxicologically-active constituents, as well as surveying human exposure, two important steps to ensuring the safety of botanical dietary supplements.

Herbal supplements: Research findings and safety

Herbal supplements are used extensively worldwide without much awareness regarding their safety and efficacy. Extensive research to determine the safety, utility, and level of research support for commonly used herbs has culminated in an easily accessible summary chart for NP providers.

Variability in Potency Among Commercial Preparations of Berberine

Berberine is an isoquinoline alkaloid plant extract that is widely available as a dietary supplement in the United States and has demonstrated efficacy in the treatment of type 2 diabetes mellitus and dyslipidemia. Because of its increased use and purported pharmacological properties, potential variations in product quality could pose a barrier to berberine's safety and effectiveness in clinical practice. Thus, this study evaluated the potency of dietary supplements containing berberine available in the U.S. commercial market. Fifteen unique dietary supplements containing berberine were purchased through U.S. dietary supplement vendors. For each product, berberine was extracted from 3 unique capsules and analyzed by ultra-high-performance liquid chromatography tandem mass spectrometry. Percentage content based on the product label claim was determined for each product. The average berberine content across the products was found to be 75% ± 25% of the product label claim, with product potency ranging from 33% to 100%. Nine of the 15 tested products (60%) failed to meet the potency standards of 90% to 110% of labeled content claim, as commonly required of pharmaceutical preparations by the U.S. Pharmacopeial Convention. Evaluation of the relationship between product cost and the measured potency failed to demonstrate an association between quality and cost. Variability in product quality may significantly contribute to inconsistencies in the safety and effectiveness of berberine. In addition, the quality of the berberine product cannot be inferred from its cost.

Effects of gamma rays on rat testis tissue according to the morphological parameters and immunohistochemistry: radioprotective role of silymarin

OBJECTIVE

To determine the radioprotective effects of Silymarin in adult male Sprague-Dawley rats irradiated with γ-rays.

METHODS

The present experimental study was performed in Tehran University of Medical Sciences, Tehran, Iran from December 2009 to March 2010. The study was performed on 40 rats, which were randomly and equally divided into four groups: 1) control group: neither received Silymarin nor irradiated with γ-rays; 2) γ-irradiation group: testis region exposed to 2Gy of γ-rays; 3) Silymarin & γ-irradiation: rats received 100 mg/kg of Silymarin 24hrs before exposure to 2Gy of γ-rays; 4) Silymarin & γ-irradiation: rats received 200 mg/kg of Silymarin 24hrs before exposure to 2Gy of γ-rays. After animal experiments and preparing the tissue sections, different histological and histomorphological parameters of seminiferous tubules and the biological characteristics of Leydig cells were evaluated applying quantitative assessment, Johnson scoring, and Leydig cell apoptosis assay by TUNEL method. The data were analyzed applying ANOVA and Tukey's post hoc test, using SPSS software (V.19).

RESULTS

Irradiation of 2 Gy γ-rays to the testis of the rats significantly affected the frequency of spermatogonia, primary spermatocyte, round spermatid, spermatozoa, seminiferous tube and lumen diameters, thickness of the epithelium, Leydig cell nuclear diameter and volume, epithelium height, and apoptotic cells (p<0.05). However, administration of Silymarin improved the mentioned parameters specifically in 200 mg/kg of dosage.

CONCLUSION

Silymarin could act as a potent radioprotector and it can be used in modulation as well as improvement to radiation therapy to prevent male reproductive function, specifically seminiferous tubules in an animal model; however, its molecular mechanism is still not clear and needs more molecular researches.

Silymarin/Silybin and Chronic Liver Disease: A Marriage of Many Years

Silymarin is the extract of Silybum marianum, or milk thistle, and its major active compound is silybin, which has a remarkable biological effect. It is used in different liver disorders, particularly chronic liver diseases, cirrhosis and hepatocellular carcinoma, because of its antioxidant, anti-inflammatory and antifibrotic power. Indeed, the anti-oxidant and anti-inflammatory effect of silymarin is oriented towards the reduction of virus-related liver damages through inflammatory cascade softening and immune system modulation. It also has a direct antiviral effect associated with its intravenous administration in hepatitis C virus infection. With respect to alcohol abuse, silymarin is able to increase cellular vitality and to reduce both lipid peroxidation and cellular necrosis. Furthermore, silymarin/silybin use has important biological effects in non-alcoholic fatty liver disease. These substances antagonize the progression of non-alcoholic fatty liver disease, by intervening in various therapeutic targets: oxidative stress, insulin resistance, liver fat accumulation and mitochondrial dysfunction. Silymarin is also used in liver cirrhosis and hepatocellular carcinoma that represent common end stages of different hepatopathies by modulating different molecular patterns. Therefore, the aim of this review is to examine scientific studies concerning the effects derived from silymarin/silybin use in chronic liver diseases, cirrhosis and hepatocellular carcinoma.

Hydrastine pharmacokinetics and metabolism after a single oral dose of goldenseal (Hydrastis canadensis) to humans

The disposition and metabolism of hydrastine was investigated in 11 healthy subjects following an oral dose of 2.7 g of goldenseal supplement containing 78 mg of hydrastine. Serial blood samples were collected for 48 hours, and urine was collected for 24 hours. Hydrastine serum and urine concentrations were determined by Liquid Chromatography-tandem mass spectrometry (LC-MS/MS). Pharmacokinetic parameters for hydrastine were calculated using noncompartmental methods. The maximal serum concentration (Cmax) was 225 ± 100 ng/ml, Tmax was 1.5 ± 0.3 hours, and area under the curve was 6.4 ± 4.1 ng ⋅ h/ml ⋅ kg. The elimination half-life was 4.8 ± 1.4 hours. Metabolites of hydrastine were identified in serum and urine by using liquid chromatography coupled to high-resolution mass spectrometry. Hydrastine metabolites were identified by various mass spectrometric techniques, such as accurate mass measurement, neutral loss scanning, and product ion scanning using Quadrupole-Time of Flight (Q-ToF) and triple quadrupole instruments. The identity of phase II metabolites was further confirmed by hydrolysis of glucuronide and sulfate conjugates using bovine β-glucuronidase and a Helix pomatia sulfatase/glucuronidase enzyme preparation. Hydrastine was found to undergo rapid and extensive phase I and phase II metabolism. Reduction, O-demethylation, N-demethylation, hydroxylation, aromatization, lactone hydrolysis, and dehydrogenation of the alcohol group formed by lactone hydrolysis to the ketone group were observed during phase I biotransformation of hydrastine. Phase II metabolites were primarily glucuronide and sulfate conjugates. Hydrastine undergoes extensive biotransformation, and some metabolites may have pharmacological activity. Further study is needed in this area.

Mechanism study of goldenseal-associated DNA damage

Goldenseal has been used for the treatment of a wide variety of ailments including gastrointestinal disturbances, urinary tract disorders, and inflammation. The five major alkaloid constituents in goldenseal are berberine, palmatine, hydrastine, hydrastinine, and canadine. When goldenseal was evaluated by the National Toxicology Program (NTP) in the standard 2-year bioassay, goldenseal induced an increase in liver tumors in rats and mice; however, the mechanism of goldenseal-associated liver carcinogenicity remains unknown. In this study, the toxicity of the five goldenseal alkaloid constituents was characterized, and their toxic potencies were compared. As measured by the Comet assay and the expression of γ-H2A.X, berberine, followed by palmatine, appeared to be the most potent DNA damage inducer in human hepatoma HepG2 cells. Berberine and palmatine suppressed the activities of both topoisomerase (Topo) I and II. In berberine-treated cells, DNA damage was shown to be directly associated with the inhibitory effect of Topo II, but not Topo I by silencing gene of Topo I or Topo II. In addition, DNA damage was also observed when cells were treated with commercially available goldenseal extracts and the extent of DNA damage was positively correlated to the berberine content. Our findings suggest that the Topo II inhibitory effect may contribute to berberine- and goldenseal-induced genotoxicity and tumorigenicity.

Milk thistle and its derivative compounds: a review of opportunities for treatment of liver disease

Milk thistle extracts have been used as a "liver tonic" for centuries. In recent years, silibinin, the active ingredient in milk thistle extracts, has been studied both in vitro and in vivo to evaluate the beneficial effects in hepatic disease. Silibinin increases antioxidant concentrations and improves outcomes in hepatic diseases resulting from oxidant injury. Silibinin treatment has been associated with protection against hepatic toxins, and also has resulted in decreased hepatic inflammation and fibrosis. Limited information currently is available regarding silibinin use in veterinary medicine. Future study is justified to evaluate dose, kinetics, and treatment effects in domestic animals.

Phototoxicity of herbal plants and herbal products

Plants are used by humans in daily life in many different ways, including as food, herbal medicines, and cosmetics. Unfortunately, many natural plants and their chemical constituents are photocytotoxic and photogenotoxic, and these phototoxic phytochemicals are widely present in many different plant families. To date, information concerning the phototoxicity and photogenotoxicity of many plants and their chemical constituents is limited. In this review, we discuss phototoxic plants and their major phototoxic constituents; routes of human exposure; phototoxicity of these plants and their constituents; general mechanisms of phototoxicity of plants and phototoxic components; and several representative phototoxic plants and their photoactive chemical constituents.