Possible mechanism by which allyl sulfides suppress neoplastic cell proliferation

Impact of Diet on Colorectal Cancer Progression and Prevention: From Nutrients to Neoplasms

Colorectal cancer (CRC), one of the most common cancers worldwide, continues to increase in incidence and mortality rates. This trend is closely linked to changes in dietary habits, which are major risk factors for colorectal cancer. The increase in the incidence of CRC in countries previously considered low-risk and with low socioeconomic status is most likely due to lifestyle and dietary changes. Understanding the influence of dietary factors on the onset of colorectal cancer is essential for prevention and treatment. This review explores the complex interplay between dietary factors and colorectal cancer, focusing on the key nutrients and dietary habits that influence disease onset and progression. The impact of diet on colorectal microbiota and the influence of diet on early-onset colorectal cancer are also reviewed, reviewing recent research on how dietary interventions affect the treatment and recurrence of colorectal cancer. Finally, the future research directions for developing and applying effective dietary intervention strategies are discussed.

From Natural Sources to Synthetic Derivatives: The Allyl Motif as a Powerful Tool for Fragment-Based Design in Cancer Treatment

Since the beginning of history, natural products have been an abundant source of bioactive molecules for the treatment of different diseases, including cancer. Many allyl derivatives, which have shown anticancer activity both in vitro and in vivo in a large number of cancers, are bioactive molecules found in garlic, cinnamon, nutmeg, or mustard. In addition, synthetic products containing allyl fragments have been developed showing potent anticancer properties. Of particular note is the allyl derivative 17-AAG, which has been evaluated in Phase I and Phase II/III clinical trials for the treatment of multiple myeloma, metastatic melanoma, renal cancer, and breast cancer. In this Perspective, we compile extensive literature evidence with descriptions and discussions of the most recent advances in different natural and synthetic allyl derivatives that could generate cancer drug candidates in the near future.

Lipid-Based Nanoparticle Formulation of Diallyl Trisulfide Chemosensitizes the Growth Inhibitory Activity of Doxorubicin in Colorectal Cancer Model: A Novel In Vitro, In Vivo and In Silico Analysis

Garlic’s main bioactive organosulfur component, diallyl trisulfide (DATS), has been widely investigated in cancer models. However, DATS is not suitable for clinical use due to its low solubility. The current study seeks to improve DATS bioavailability and assess its chemopreventive and chemosensitizing properties in an AOM-induced colorectal cancer model. The polyethylene glycol coated Distearoylphosphatidylcholine/Cholesterol (DSPC/Chol) comprising DATS-loaded DATSL and doxorubicin (DOXO)-encapsulated DOXL liposomes was prepared and characterized. The changes in the sensitivity of DATS and DOXO by DATSL and DOXL were evaluated in RKO and HT-29 colon cancer cells. The synergistic effect of DATSL and DOXL was studied by cell proliferation assay in the combinations of IC₁₀, IC₂₅, and IC₃₅ of DATSL with the IC₁₀ of DOXL. AOM, DATSL, and DOXL were administered to different groups of mice for a period of 21 weeks. The data exhibited ~93% and ~46% entrapment efficiency of DATSL and DOXL, respectively. The size of sham liposomes was 110.5 nm, whereas DATSL and DOXL were 135.5 nm and 169 nm, respectively. DATSL and DOXL exhibited significant sensitivity in the cell proliferation experiment, lowering their IC₅₀ doses by more than 8- and 14-fold, respectively. However, the DATSL IC₁₀, IC₂₅, and IC₃₅ showed escalating chemosensitivity, and treated the cells in combination with DOXL IC₁₀. Analysis of histopathological, cancer marker enzymes, and antioxidant enzymes revealed that the high dose of DATSL pretreatment and DOXL chemotherapy is highly effective in inhibiting AOM-induced colon cancer promotion. The combination of DATSL and DOXL indicated promise as a colorectal cancer treatment in this study. Intermolecular interactions of DATS and DOXO against numerous cancer targets by molecular docking indicated MMP-9 as the most favourable target for DATS exhibiting binding energy of −4.6 kcal/mol. So far, this is the first research to demonstrate the chemopreventive as well as chemosensitizing potential of DATSL in an animal model of colorectal cancer.

Pharmacological Effects of Cisplatin Combination with Natural Products in Cancer Chemotherapy

Cisplatin and other platinum-based drugs, such as carboplatin, ormaplatin, and oxaliplatin, have been widely used to treat a multitude of human cancers. However, a considerable proportion of patients often relapse due to drug resistance and/or toxicity to multiple organs including the liver, kidneys, gastrointestinal tract, and the cardiovascular, hematologic, and nervous systems. In this study, we sought to provide a comprehensive review of the current state of the science highlighting the use of cisplatin in cancer therapy, with a special emphasis on its molecular mechanisms of action, and treatment modalities including the combination therapy with natural products. Hence, we searched the literature using various scientific databases., such as MEDLINE, PubMed, Google Scholar, and relevant sources, to collect and review relevant publications on cisplatin, natural products, combination therapy, uses in cancer treatment, modes of action, and therapeutic strategies. Our search results revealed that new strategic approaches for cancer treatment, including the combination therapy of cisplatin and natural products, have been evaluated with some degree of success. Scientific evidence from both in vitro and in vivo studies demonstrates that many medicinal plants contain bioactive compounds that are promising candidates for the treatment of human diseases, and therefore represent an excellent source for drug discovery. In preclinical studies, it has been demonstrated that natural products not only enhance the therapeutic activity of cisplatin but also attenuate its chemotherapy-induced toxicity. Many experimental studies have also reported that natural products exert their therapeutic action by triggering apoptosis through modulation of mitogen-activated protein kinase (MAPK) and p53 signal transduction pathways and enhancement of cisplatin chemosensitivity. Furthermore, natural products protect against cisplatin-induced organ toxicity by modulating several gene transcription factors and inducing cell death through apoptosis and/or necrosis. In addition, formulations of cisplatin with polymeric, lipid, inorganic, and carbon-based nano-drug delivery systems have been found to delay drug release, prolong half-life, and reduce systemic toxicity while other formulations, such as nanocapsules, nanogels, and hydrogels, have been reported to enhance cell penetration, target cancer cells, and inhibit tumor progression.

The Effect of Liposomal Diallyl Disulfide and Oxaliplatin on Proliferation of Colorectal Cancer Cells: In Vitro and In Silico Analysis

Diallyl disulfide (DADS) is one of the main bioactive organosulfur compounds of garlic, and its potential against various cancer models has been demonstrated. The poor solubility of DADS in aqueous solutions limits its uses in clinical application. The present study aimed to develop a novel formulation of DADS to increase its bioavailability and therapeutic potential and evaluate its role in combination with oxaliplatin (OXA) in the colorectal cancer system. We prepared and characterized PEGylated, DADS (DCPDD), and OXA (DCPDO) liposomes. The anticancer potential of these formulations was then evaluated in HCT116 and RKO colon cancer cells by different cellular assays. Further, a molecular docking-based computational analysis was conducted to determine the probable binding interactions of DADS and OXA. The results revealed the size of the DCPDD and DCPDO to be 114.46 nm (95% EE) and 149.45 nm (54% EE), respectively. They increased the sensitivity of the cells and reduced the IC₅₀ several folds, while the combinations of them showed a synergistic effect and induced apoptosis by 55% in the cells. The molecular docking data projected several possible targets of DADS and OXA that could be evaluated more precisely by these novel formulations in detail. This study will direct the usage of DCPDD to augment the therapeutic potential of DCPDO against colon cancer in clinical settings.

Immunomodulatory effects of Allium Sativum L. and its constituents against viral infections and metabolic diseases

BACKGROUND

Allium sativum L., or garlic, is one of the most studied plants worldwide within the field of traditional medicine. Current interests lie in the potential use of garlic as a preventive measure and adjuvant treatment for viral infections, e.g., SARS-CoV-2. Even though it cannot be presented as a single treatment, its beneficial effects are beyond doubt. The World Health Organization has deemed it an essential part of any balanced diet with immunomodulatory properties.

OBJECTIVE

The aim of the study was to review the literature on the effects of garlic compounds and preparations on immunomodulation and viral infection management, with emphasis on SARS-CoV-2.

METHOD

Exhaustive literature search has been carried out on electronic databases.

CONCLUSION

Garlic is a fundamental part of a well-balanced diet which helps maintain general good health. The reported information regarding garlic's ability to beneficially modulate inflammation and the immune system is encouraging. Nonetheless, more efforts must be made to understand the actual medicinal properties and mechanisms of action of the compounds found in this plant to inhibit or diminish viral infections, particularly SARS-CoV-2. Based on our findings, we propose a series of innovative strategies to achieve such a challenge in the near future.

Medicinal Herbs Used in Traditional Management of Breast Cancer: Mechanisms of Action

Background: Breast cancer is one of the principal causes of death among women and there is a pressing need to develop novel and effective anti-cancer agents. Natural plant products have shown promising results as anti-cancer agents. Their effectiveness is reported as decreased toxicity in usage, along with safety and less recurrent resistances compared with hormonal targeting anti-cancer agents. Methods: A literature search was conducted for all English-language literature published prior to June 2020. The search was conducted using electronic databases, including PubMed, Embase, Web of Science, and Cochrane Library. The search strategy included keywords such as breast cancer, herbs, anti-cancer biologically active components, clinical research, chemotherapy drugs amongst others. Results: The literature provides documented evidence of the chemo-preventative and chemotherapeutic properties of Ginseng, garlic (Allium sativum), Black cohosh (Actaea racemose), Tumeric (Curcuma longa), Camellia sinenis (green tea), Echinacea, Arctium (burdock), Flaxseed (Linum usitatissimum) and Black Cumin (Nigella sativa). Conclusions: The nine herbs displayed anti-cancer properties and their outcomes and mechanisms of action include inhibition of cell proliferation, angiogenesis and apoptosis as well as modulation of key intracellular pathways. However, more clinical trials and cohort human studies should be conducted to provide key evidence of their medical benefits.

Antioxidant and Antiproliferative Activity of Allium ursinum and Their Associated Microbiota During Simulated in vitro Digestion in the Presence of Food Matrix

In this study, for the first time, the comprehensive analysis of antiproliferative and antioxidant activities of ramson, followed by the analysis of its associated microbiota and health-promoting effects of lactic acid bacteria (LAB), was performed. Ramson (Allium ursinum) is recognized as a medicinal plant with a long history of use in traditional medicine due to its antimicrobial and antioxidant activity. In this study the influence of in vitro gastrointestinal digestion on the cytotoxic activity of A. ursinum extracts against human malignant cell lines was demonstrated. Seven sulfur compounds, the degradation products of thiosulfinates, including diallyl disulfide were shown to inhibit proliferation of malignant cells by inducing accumulation within G2/M phase as well as to induce apoptosis through activation of caspase-3 and mitochondrial signaling pathway. Further, the A. ursinum microbiota, particularly LAB with potential probiotic effects, was analyzed by culture-dependent method and culture-independent method [denaturing gradient gel electrophoresis (DGGE)]. The obtained results revealed that the most abundant genera were Streptococcus, Lactobacillus, and Bacillus. The Lactobacillus genus was mainly represented by L. fermentum. The pulsed-field gel electrophoresis (PFGE) analysis revealed the presence of two PFGE pulsotypes. The probiotic potential of the strain L. fermentum BGSR163 belonging to PFGE pulsotype 1 and the strain L. fermentum BGSR227 belonging to the PFGE pulsotype 2 was characterized. The results revealed that both strains are safe for human use, successfully survive the simulated gastrointestinal conditions, have potential to transiently colonize the gastrointestinal tract (GIT) and have a protective immunomodulatory effect, inducing the production of proinflammatory cytokine IL17 and regulatory cytokine IL10, while decreasing the production of proinflammatory cytokine IFN-γ. In conclusion, the results of this study suggest that consumption of A. ursinum might have health-promoting properties, including anticancer effects, while L. fermentum strains isolated from A. ursinum leaves could be used as probiotics for human consumption.

E-Cadherin/β-Catenin Complex: A Target for Anticancer and Antimetastasis Plants/Plant-derived Compounds

Plants reputed to have cancer-inhibiting potential and putative active components derived from those plants have emerged as an exciting new field in cancer study. Some of these compounds have cancer-inhibiting potential in different clinical staging levels, especially metastasis. A few of them which stabilize cell-cell adhesions are controversial topics. This review article introduces some effective herbal compounds that target E-cadherin/β-catenin protein complex. In this article, at first, we briefly review the structure and function of E-cadherin and β-catenin proteins, Wnt signaling pathway, and its target genes. Then, effective compounds of the Teucrium persicum, Teucrium polium, Allium sativum (garlic), Glycine max (soy), and Brassica oleracea (broccoli) plants, which influence stability and cellular localization of E-cadherin/β-catenin complex, were studied. Based on literature review, there are some compounds in these plants, including genistein of soy, sulforaphane of broccoli, organosulfur compounds of garlic, and the total extract of Teucrium genus that change the expression of variety of Wnt target genes such as MMPs, E-cadherin, p21, p53, c-myc, and cyclin D1. So they may induce cell-cycle arrest, apoptosis and/or inhibition of Epithelial-Mesenchymal Transition (EMT) and metastasis.

Application of quality-by-design approach to optimize diallyl disulfide-loaded solid lipid nanoparticles

The current work was carried out by the principles of quality-by-design approach to develop an optimized solid lipid nanoparticles (SLNs) formulation of diallyl disulfide (DADS) through systematic statistical study. And its antitumor activity of DADS was also evaluated on breast cancer cell lines. To understand the effect of formulation variables (critical parameters) on the responses (critical quality attributes) of SLN, a 3-factor, 3-level Box-Behnken design, was explored to predict the responses such as particle size (Y1) and % entrapment efficiency (EE) (Y2) when concentration of surfactant (X1), amount of lipid (X2), and volume of solvent (X3) were selected as independent variables. Particle size analysis revealed that all the batches were within the nanometer range. DADS was released from the SLN much more rapidly at pH 4.5 than at pH 7.4, which is a desirable characteristic for tumor-targeted drug delivery. The cytotoxicity, reactive oxygen species (ROS), determination revealed that the antitumor activity of DADS is enhanced with SLN compared to DADS-free drug, and apoptosis is the mechanism underlying the cytotoxicity. The present study indicated the remarkable potential of DADS-SLN in enhancing the anticancer effect of DADS in breast cancer cells in vitro.

Allicin Induces Calcium and Mitochondrial Dysregulation Causing Necrotic Death in Leishmania

Background

Allicin has shown antileishmanial activity in vitro and in vivo. However the mechanism of action underlying its antiproliferative effect against Leishmania has been virtually unexplored. In this paper, we present the results obtained in L.infantum and a mechanistic basis is proposed.

Methodology/Principal Finding

Exposure of the parasites to allicin led to high Ca²⁺ levels and mitochondrial reactive oxygen species (ROS), collapse of the mitochondrial membrane potential, reduced production of ATP and elevation of cytosolic ROS. The incubation of the promastigotes with SYTOX Green revealed that decrease of ATP was not associated with plasma membrane permeabilization. Annexin V and propidium iodide (PI) staining indicated that allicin did not induce phospholipids exposure on the plasma membrane. Moreover, DNA agarose gel electrophoresis and TUNEL analysis demonstrated that allicin did not provoke DNA fragmentation. Analysis of the cell cycle with PI staining showed that allicin induced cell cycle arrest in the G₂/M phase.

Conclusions/Significance

We conclude that allicin induces dysregulation of calcium homeostasis and oxidative stress, uncontrolled by the antioxidant defense of the cell, which leads to mitochondrial dysfunction and a bioenergetic catastrophe leading to cell necrosis and cell cycle arrest in the premitotic phase.

Leishmaniasis is a vectorial parasitic disease caused by flagellate organisms from the genus Leishmania. Infection is present in over 80 countries and visceral forms are the second most fatal human parasitic disease. Control relies on chemotherapy but available drugs have important shortcomings such as toxicity, side effects, unaffordable price of the safest presentations and increasing reports of parasite resistance and clinical failures. Thus, new drugs are needed. Allicin, a molecule obtained from garlic, has shown antiproliferative effect against different cancer cells, bacteria, fungi and Protista including Leishmania. Insofar its mechanism of action is poorly known. Our results with L.infantum point towards allicin inducing high levels of intracellular calcium, redox inbalance, and mitochondrial dysfunction with reduction of ATP. These events lead to cell necrosis without evidence of apoptotic-like markers. The proposed model suggests the potential use of allicin against leishmaniasis, alone or in combination with other drugs with different mechanisms of action.

Diallyl Sulfide and Its Role in Chronic Diseases Prevention

Diallyl sulfide (C₆H₁₀S, DAS) is one of the novel natural organosulfur compounds, which is mostly obtained from the genus Allium plants. Numerous studies have revealed several unique properties of DAS in terms of its health-promoting effects. DAS has proved to be anticancer, antimicrobial, anti-angiogenic, and immunomodulatory like unique functions as demonstrated by the multiple investigations. Diallyl sulfide can also impede oxidative stress and chronic inflammation as suggested by the literature. Studies also explored that DAS could thwart the development of chronic diseases like cancer, neuronal, cardiovascular disease through modulating mechanistic pathways involved in pathogenesis. In this book chapter, we have attempted to give the comprehensive view on DAS about the physiochemical and biological properties, and its preventive role in chronic diseases with a mechanistic overview.

Prevention of colorectal cancer and dietary management

OBJECTIVES

This systematic review focuses on dietary and lifestyle risk factors for colorectal cancer (CRC) prevention and chemoprevention among high-risk populations.

METHODS AND MATERIALS

We searched PubMed for English-language articles about dietary components, lifestyle risk factors, and chemoprevention agents in relation to colorectal cancer and their references published from 1980 through 2013. We reviewed articles jointly for the most clinically important information, emphasizing randomized trials and meta-analyses where available.

RESULTS

There is convincing evidence that intake of garlic, vitamin B6 and magnesium, active living, maintaining a healthy weight and waist, avoiding or reducing red meat, alcohol, and smoking, as well as hormone replacement therapy among women may significantly protect against developing colorectal cancer. There is less consistent evidence for fruit and vegetable intake (fiber and folate), fish and Omega-3 fatty acids, selenium, dairy, calcium and vitamin D. For high-risk populations, aspirin have been shown to protect against the development of colonic adenomas and CRC, while a minimal effective dose remains unclear.

CONCLUSIONS

Colorectal cancer can be prevented in general population through dietary and lifestyle interventions, and aspirin may be a good choice of chemoprevention agent among high risk individuals.

Garlic and onions: their cancer prevention properties

The Allium genus includes garlic, onions, shallots, leeks, and chives. These vegetables are popular in cuisines worldwide and are valued for their potential medicinal properties. Epidemiologic studies, while limited in their abilities to assess Allium consumption, indicate some associations of Allium vegetable consumption with decreased risk of cancer, particularly cancers of the gastrointestinal tract. Limited intervention studies have been conducted to support these associations. The majority of supportive evidence on Allium vegetables cancer-preventive effects comes from mechanistic studies. These studies highlight potential mechanisms of individual sulfur-containing compounds and of various preparations and extracts of these vegetables, including decreased bioactivation of carcinogens, antimicrobial activities, and redox modification. Allium vegetables and their components have effects at each stage of carcinogenesis and affect many biologic processes that modify cancer risk. This review discusses the cancer-preventive effects of Allium vegetables, particularly garlic and onions, and their bioactive sulfur compounds and highlights research gaps.

Garlic consumption and colorectal cancer risk in the CPS-II Nutrition Cohort

PURPOSE

The World Cancer Research Fund/American Institute for Cancer Research identified a probable role for garlic in colorectal cancer prevention based on preclinical evidence and epidemiologic studies, but prospective data are limited. The purpose of this paper was to contribute additional evidence on this topic for men and women in a large prospective cohort study.

METHODS

In 1999, 42,824 men and 56,876 women in the Cancer Prevention Study II Nutrition Cohort completed a questionnaire with information on dietary garlic consumption. Garlic supplement use was assessed in 2001. Cox proportional hazards regression was used to estimate multivariable-adjusted hazard rate ratios (HRs) and 95 % confidence intervals (CIs).

RESULTS

During 7 years of follow-up, 579 men and 551 women were diagnosed with colorectal cancer. Among men, daily garlic consumption was associated with a non-significant higher colorectal cancer risk (HR = 1.04, 95 % CI 0.99-1.08 for each additional clove or "4 shakes" of garlic per week), whereas the association was borderline inverse in women (HR = 0.95, 95 % CI 0.91-1.00, p heterogeneity by sex = 0.03). Garlic supplement use was not related to a lower risk of colorectal cancer, and in men, former use was associated with a higher risk of colorectal cancer (HR = 1.85, 95 % CI 1.13-3.03).

CONCLUSIONS

These results provide weak support for a role of dietary garlic consumption in colorectal cancer prevention in women, but a possible increased risk in men. Further research is needed to confirm different associations by sex.

Diallyl disulfide induces Ca2+ mobilization in human colon cancer cell line SW480

Diallyl disulfide (DADS), one of the major organosulfur compounds of garlic, is recognized as a group of potential chemopreventive compounds. In this study, we examines the early signaling effects of DADS on human colorectal cancer cells SW480 loaded with Ca(2+)-sensitive dye fura-2. It was found that DADS caused an immediate and sustained rise of [Ca(2+)](i) in a concentration-dependent manner (EC(50) = 232 μM). DADS also induced a [Ca(2+)](i) elevation when extracellular Ca(2+) was removed, but the magnitude was reduced by 45%. Depletion of intracellular Ca(2+) stores with 2 μM carbonylcyanide m-chlorophenylhydrazone, a mitochondrial uncoupler, didn't affect DADS's effect. In Ca(2+)-free medium, the DADS-induced [Ca(2+)](i) rise was abolished by depleting stored Ca(2+) with 1 μM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor). DADS-caused [Ca(2+)](i) rise in Ca(2+)-containing medium was not affected by modulation of protein kinase C activity. The DADS-induced Ca(2+) influx was blocked by nicardipine (10 μM). U73122, an inhibitor of phospholipase C, abolished ATP (but not DADS)-induced [Ca(2+)](i) rise. These findings suggest that DADS induced a significant rise in [Ca(2+)](i) in SW480 colon cancer cells by stimulating both extracellular Ca(2+) influx and thapsigargin-sensitive intracellular Ca(2+) release via as yet unidentified mechanisms.

Allicin purified from fresh garlic cloves induces apoptosis in colon cancer cells via Nrf2

Allicin (diallyl thiosulfinate) is the best-known biologically active component in freshly crushed garlic extract. We developed a novel, simple method to isolate active allicin, which yielded a stable compound in aqueous solution amenable for use in in vitro and in vivo studies. We focused on the in vitro effects of allicin on cell proliferation of colon cancer cell lines HCT-116, LS174T, HT-29, and Caco-2 and assessed the underlying mechanisms. This allicin preparation exerted a time- and dose-dependent cytostatic effect on these cells at concentrations ranging from 6.2 to 310 μM. Treatment with allicin resulted in HCT-116 apoptotic cell death as demonstrated by enhanced hypodiploid DNA content, decreased levels of B-cell non-Hodgkin lymphoma-2 (Bcl-2), increased levels of bax and increased capability of releasing cytochrome c from mitochondria to the cytosol. Allicin also induced translocation of NF-E2-related factor-2 (Nrf2) to the nuclei of HCT-116 cells. Luciferase reporter gene assay showed that allicin induces Nrf2-mediated luciferase transactivation activity. SiRNA knock down of Nrf2 significantly affected the capacity of allicin to inhibit HCT-116 proliferation. These results suggest that Nrf2 mediates the allicin-induced apoptotic death of colon cancer cells.

Consumption of S-allylcysteine inhibits the growth of human non-small-cell lung carcinoma in a mouse xenograft model

Lung cancer is one of the leading causes of cancer death in the world. Human non-small-cell lung carcinoma (NSCLC) accounts for almost 80% of lung cancer cases. Aberrant phosphoinositide 3-kinase (PI3K)/Akt/mTOR signaling pathways play important roles and have been widely observed in the development of NSCLC. Previous studies indicated that garlic extracts such as diallyl disulfide (DADS) and diallyl trisulfide (DATS) could inhibit the proliferation of several types of cancer in vitro. However, the inhibitory effects of S-allylcysteine (SAC) on the growth of NSCLC have not been demonstrated yet. Therefore, this study investigated whether consumption of SAC could prevent the growth of NSCLC in both in vitro and in vivo models. It was found that SAC significantly inhibited the proliferation of human NSCLC A-549 cells in vitro. Treatment of the NF-κB inhibitor, Bay-11-7082, could significantly inhibit the proliferation of NSCLC A-549 cells. The results demonstrated that SAC significantly suppressed the activation of mTOR, NF-κB, and cyclin D1 molecules in vitro. Furthermore, the results demonstrated that consumption of SAC significantly inhibited the growth of highly metastatic human NSCLC cells in tumor-bearing mice. Bioluminescence imaging and pathological and immunohistochemical (IHC) staining results also indicated that SAC could effectively suppress the growth and malignant progression of human NSCLC in vivo. The chemopreventive effects of SAC were associated with suppression of mTOR and NF-κB molecules in vivo. These results suggested that SAC could act as an effective agent against the malignant progression of human NSCLC in both in vitro and in vivo models.

Synthesis, identification and anti-cancer activity of 1-(4-methylpent-2-enyl)-2-(4-phenylbut-2-enyl)disulfane

In this study, we synthesized 1-(4-methylpent-2-enyl)-2-(4-phenylbut-2- enyl)disulfane using sodium sulfide, 1-bromine-4-methyl-2-amylene and 1-(4-bromine-2- butylene)benzene as raw materials. The yield rate of target product was 84%. The structure of the target product was confirmed by GC-MS, ¹H-NMR and elemental analysis. The results of anti-cancer activity experiments showed that 1-(4-methylpent-2-enyl)-2-(4- phenylbut-2-enyl)disulfane could significantly inhibit the proliferation, induce the apoptosis of CNE2 cells in a dose dependent manner, and could significantly enhance the activity of XIAP.

Biological properties of garlic and garlic-derived organosulfur compounds

Medicinal properties of garlic (Allium sativum) have been widely known and used since ancient times till the present. Garlic enhances immune functions and has antibacterial, antifungal and antivirus activities. It is known to prevent platelet aggregation, and to have hypotensive and cholesterol- and triglyceride-lowering properties, although the latter features have been questioned. This review is focused on anticancer efficacy of Allium sativum, and attempts to explain the mechanisms of this action. Medicinal properties of garlic rely upon organosulfur compounds mostly derived from alliin. Organosulfur compounds originating from garlic inhibit carcinogen activation, boost phase 2 detoxifying processes, cause cell cycle arrest mostly in G2/M phase, stimulate the mitochondrial apoptotic pathway, increase acetylation of histones. Garlic-derived sulfur compounds influence also gap-junctional intercellular communication and participate in the development of multidrug resistance. This review presents also other little known aspects of molecular action of garlic-derived compounds, like modulation of cellular redox state, involvement in signal transduction and post-translational modification of proteins by sulfane sulfur or by formation of mixed disulfides (S-thiolation reactions).

Apoptosis induced by diallyl disulfide in human breast cancer cell line MCF-7

AIM

To investigate the effect of diallyl disulfide (DADS), a component of garlic, on apoptosis in human mammary cancer cell line (MCF-7) and its mechanisms.

METHODS

Cytotoxicity was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide assays. Morphology of apoptotic cells was detected by acridine orange and ethidium bromide staining. Apoptotic cells stained with propidium iodide were examined using flow cytometry. Protein levels were detected by Western blot analysis.

RESULTS

DADS inhibited the proliferation of MCF-7 cells and induced the apoptotic ratio to increase rapidly. Cleavage of the caspase-3 and caspase-3 substrate poly(ADP-ribose) polymerase was observed in MCF-7 cells after 24 h of treatment with DADS. When the MCF-7 cells were treated with 200 micromol x L DADS, the stress-activated protein kinase extracellular signal-regulated kinase (ERK), a mitogen-activated protein kinase, was inhibited after 6 h; c-Jun N-terminal kinase (JNK), that is stress-activated protein kinase (SAPK), and p38 mitogen-activated protein kinase were activated after 6 h.

CONCLUSION

These results suggest that DADS both inhibits the proliferation of MCF-7 cells and induces apoptosis of MCF-7 cells. The mechanisms may include the inhibition of ERK and the activation of the SAPK/JNK and p38 pathways.

Rhodanese-thioredoxin system and allyl sulfur compounds

Sodium 2-propenyl thiosulfate, a water-soluble organo-sulfane sulfur compound isolated from garlic, induces apoptosis in a number of cancer cells. The molecular mechanism of action of sodium 2-propenyl thiosulfate has not been completely clarified. In this work we investigated, by in vivo and in vitro experiments, the effects of this compound on the expression and activity of rhodanese. Rhodanese is a protein belonging to a family of enzymes widely present in all phyla and reputed to play a number of distinct biological roles, such as cyanide detoxification, regeneration of iron-sulfur clusters and metabolism of sulfur sulfane compounds. The cytotoxic effects of sodium 2-propenyl thiosulfate on HuT 78 cells were evaluated by flow cytometry and DNA fragmentation and by monitoring the progressive formation of mobile lipids by NMR spectroscopy. Sodium 2-propenyl thiosulfate was also found to induce inhibition of the sulfurtransferase activity in tumor cells. Interestingly, in vitro experiments using fluorescence spectroscopy, kinetic studies and MS analysis showed that sodium 2-propenyl thiosulfate was able to bind the sulfur-free form of the rhodanese, inhibiting its thiosulfate:cyanide-sulfurtransferase activity by thiolation of the catalytic cysteine. The activity of the enzyme was restored by thioredoxin in a concentration-dependent and time-dependent manner. Our results suggest an important involvement of the essential thioredoxin-thioredoxin reductase system in cancer cell cytotoxicity by organo-sulfane sulfur compounds and highlight the correlation between apoptosis induced by these compounds and the damage to the mitochondrial enzymes involved in the repair of the Fe-S cluster and in the detoxification system.

Allicin inhibits cell growth and induces apoptosis through the mitochondrial pathway in HL60 and U937 cells

In this article, the effects of allicin, a biological active compound of garlic, on HL60 and U937 cell lines were examined. Allicin induced growth inhibition and elicited apoptotic events such as blebbing, mitochondrial membrane depolarization, cytochrome c release into the cytosol, activation of caspase 9 and caspase 3 and DNA fragmentation. Pretreatment of HL60 cells with cyclosporine A, an inhibitor of the mitochondrial permeability transition pore (mPTP), inhibited allicin-treated cell death. HL60 cell survival after 1 h pretreatment with cyclosporine A, followed by 16 h in presence of allicin (5 microM) was approximately 80% compared to allicin treatment alone (approximately 50%). Also N-acetyl cysteine, a reduced glutathione (GSH) precursor, prevented cell death. The effects of cyclosporine A and N-acetyl cysteine suggest the involvement of mPTP and intracellular GSH level in the cytotoxicity. Indeed, allicin depleted GSH in the cytosol and mitochondria, and buthionine sulfoximine, a specific inhibitor of GSH synthesis, significantly augmented allicin-induced apoptosis. In HL60 cells treated with allicin (5 microM, 30 min) the redox state for 2GSH/oxidized glutathione shifted from EGSH -240 to -170 mV. The same shift was observed in U937 cells treated with allicin at a higher concentration for a longer period of incubation (20 microM, 2 h). The apoptotic events induced by various concentrations of allicin correlate to intracellular GSH levels in the two cell types tested (HL60: 3.7 nmol/10(6) cells; U937: 7.7 nmol/10(6) cells). The emerging mechanistic basis for the antiproliferative function of allicin, therefore, involves the activation of the mitochondrial apoptotic pathway by GSH depletion and by changes in the intracellular redox status.

Erk is involved in the differentiation induced by diallyl disulfide in the human gastric cancer cell line MGC803

Diallyl disulfide (DADS) is a major constituent of garlic. Previously, we found that DADS both inhibited proliferation in human gastric cancer cells in vitro and in vivo, and induced G2/M arrest. In this study, we investigated whether this differentiation effect was induced by DADS in human gastric cancer MGC803 cells, and whether it was related to an alteration in ERK activity. The results showed that the growth of MGC803 cells was inhibited by DADS. Cells treated with DADS displayed a lower nucleocytoplasmic ratio and tended to form gland and intercellular conjunction structures. The ConA-mediated cell agglutination ratio and cells' ALP specific activity decreased. In MGC803 cells, dye transfer was limited to a few cells neighbouring the dye-injected cell and to a depth of 1-2 layers beneath the scrape site. However, after treatment with DADS, the LY (Lucifer Yellow) was transferred to several cells immediately neighbouring the microinjected cell and to a depth of 2-4 cell layers from the scrape site. This indicated that DADS induced differentiation in MGC803 cells. Western blot analysis revealed that although DADS did not influence the quantity of ERK1/2 protein expressed, it did decrease its phosphorylation in a concentration-dependent manner, compared with the controls. At 30 mg x L(-1), DADS inhibited the activation of ERK1/2 in 15-30 min. These results suggested that the DADS-induced differentiation of MGC803 cells involved an alteration of the ERK1/2 signaling pathway.

Diallyl disulfide suppresses growth of HL-60 cell through increasing histone acetylation and p21WAF1 expression in vivo and in vitro

AIM

To examine the differentiation induction and growth inhibition of HL-60 cells by diallyl disulfide (DADS), and its relationship with the alterations of histone acetylation and p21(WAF1) expression in vitro and in vivo.

METHODS

Differentiation was studied by nitroblue tetrazolium (NBT) reduction of HL-60 cell in vitro. HL-60 cells 5x10(6) were injected into the right side of the peritoneal cavity of severe combined immunodeficiency (SCID) mice. When the peritoneal neoplasms were detected, the SCID mice were randomly divided into 3 groups and received an ip injection of vehicle alone (NS), DADS or sodium butyrate (SB). The growth inhibition of peritoneal neoplasms induced by DADS was observed by a growth curve. The cycle distribution of HL-60 cells in SCID mice was monitored by flow cytometry. The expression of acetylated histone H3, H4 and p21(WAF1) were measured by Western blot.

RESULTS

After treatment with DADS for 0-72 h, the NBT reduction ability of HL-60 cells increased in a time-dependent manner, compared with no treatment of HL-60 cells. In the HL-60 cells treated with DADS for 24 h, the expression of acetylated histone H3, H4, and p21(WAF1) increased obviously. After treatment with DADS, tumor growth was markedly suppressed. HL-60 cells from mice treated with DADS were blocked in the G1 phase, from 25.4% to 63.4%. The tumors from the mice treated with DADS showed an increase of acetylated histone H3, H4, and p21(WAF1).

CONCLUSION

DADS could induce differentiation and inhibit the growth of HL-60 cells through increasing the expression of acetylated histone H3, H4, and p21(WAF1) in vitro and in vivo.

Effects of water garlic extracts on cell cycle and viability of HepG2 hepatoma cells

Garlic extracts, either aqueous or oily, are commonly employed to prepare garlic derivative supplements used as nutraceuticals for the treatment of different pathologies. In this study, we investigated the effects of water garlic extracts from two different areas of Italy well known for garlic production, Latina (GEL) and Sulmona (GES), on cell cycle and death of HepG2 hepatoma cells. The effects of the treatments with GEL and GES were also compared with the oil-soluble sulfur compound of garlic, diallyl disulfide (DADS). GEL and GES induced a p53/p21-dependent cell cycle arrest in G2/M phase and apoptosis, although to a different extent, whereas DADS, under the experimental conditions used, was not detrimental to HepG2 cells. GEL and GES committed HepG2 cells to apoptosis by the activation of c-Jun-NH(2) terminal kinase (JNK)/c-Jun phosphorylative cascade without a detectable increase in the flux of reactive oxygen species. Moreover, differentiation of HepG2 cells induced by retinoic acid determined resistance to GEL and GES treatments without the activation of JNK signaling pathway. Overall, the results obtained indicate that water-soluble garlic extracts are more inhibitory of the growth of transformed hepatoma cells than the oil-soluble isolated compound DADS, and that their antiproliferative properties are different depending on the area of origin of the starting material.

Dietary agents as histone deacetylase inhibitors

In cancer cells, an imbalance often exists between histone acetyltransferase (HAT) and histone deacetylase (HDAC) activities, and various drug companies are actively seeking competitive HDAC inhibitors for chemotherapeutic intervention. Cancer cells appear to be more sensitive than nontransformed cells to HDAC inhibitors, which disrupt the cell cycle and induce apoptosis via derepression of genes such as P21 and BAX. However, in the search for potent HDAC inhibitors with cancer therapeutic potential, a tendency exists to overlook or dismiss weak ligands that could prove effective in cancer prevention. Butyrate, diallyl disulfide (DADS), and sulforaphane (SFN) are three dietary agents that exhibit HDAC inhibitory activity in vitro and/or in vivo, and other such dietary agents probably will be discovered that affect HDAC activity. We make the distinction between 'pharmacologic' agents that potently derepress gene expression, during therapeutic intervention, and dietary HDAC inhibitors that, as weak ligands, might subtly regulate the expression of genes involved in cell growth and apoptosis. An important issue for future study is to determine the extent to which dietary HDAC inhibitors, by modulating genes such as p21 and Bax, enable normal, nontransformed cells to respond most effectively to external stimuli and toxic insults.

Preclinical perspectives on garlic and cancer

Evidence continues to point to the anticancer properties of fresh garlic extracts, aged garlic, garlic oil, and a number of specific organosulfur compounds generated by processing garlic. These anticarcinogenic and antitumorigenic characteristics appear to arise through both dose- and temporal-related changes in a number of cellular events involved with the cancer process, including those involving drug metabolism, immunocompetence, cell cycle regulation, apoptosis, and angiogenesis. The ability of garlic and related allyl sulfur compounds to block tumors in the colon, lung, breast, and liver suggests general mechanisms that are not tissue specific. Whereas relatively few studies have compared the relative efficacy of water- and lipid-soluble allyl sulfur compounds, those that have when using chemically induced carcinogen models suggest little difference in response, whereas tumor proliferation/apoptosis is highly dependent on the species provided. A shift in sulfhydryl groups, alterations in glutathione:oxidized glutathione ratios, and resultant changes in cellular redox status may be involved in some of the phenotypic changes caused by allyl sulfur compounds. Such changes in thiols by allyl sulfurs may also account for the observed hyperphosphorylation of specific cell cycle proteins and the histone hyperacetylation that has been correlated with suppressed tumor cell proliferation. Whereas the anticarcinogenic and antitumorigenic data to date are impressive, additional studies are needed with more modest exposure to allyl sulfur compounds over prolonged periods. Likewise, additional studies are needed that incorporate transgenic and knockout models to assist in the identification of molecular targets for garlic and its associated allyl sulfur components.

Cancer chemoprevention by garlic and garlic-containing sulfur and selenium compounds

As early as 1550 B.C., Egyptians realized the benefits of garlic as a remedy for a variety of diseases. Many epidemiological studies support the protective role of garlic and related allium foods against the development of certain human cancers. Natural garlic and garlic cultivated with selenium fertilization have been shown in laboratory animals to have protective roles in cancer prevention. Certain organoselenium compounds and their sulfur analogs have been identified in plants. Organoselenium compounds synthesized in our laboratory were compared with their sulfur analogs for chemopreventive efficacy. Diallyl selenide was at least 300-fold more effective than diallyl sulfide in protecting against 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary adenocarcinomas in rats. In addition, benzyl selenocyanate inhibited the development of DMBA-induced mammary adenocarcinomas and azoxymethane-induced colon cancer in rats and benzo[a]pyrene-induced forestomach tumors in mice. The sulfur analog, benzyl thiocyanate, had no effect under the same experimental conditions. Furthermore, we showed that 1,4-phenylenebis(methylene)selenocyanate, but not its sulfur analog, significantly inhibited DMBA-DNA adduct formation and suppressed DMBA-induced mammary carcinogenesis. Collectively, these results indicate that structurally distinctive organoselenium compounds are superior to their corresponding sulfur analogs in cancer chemoprevention. Additionally, synthetic aromatic selenocyanates are more effective cancer chemopreventive agents than the naturally occurring selenoamino acids. Because plants are capable of utilizing selenium in a manner similar to that in sulfur assimilation pathways, future studies should aim at determining whether, under appropriate conditions, these potent cancer chemopreventive synthetic selenium compounds can be synthesized by garlic and related allium foods.

Preclinical Perspectives on Garlic and Cancer

Evidence continues to point to the anticancer properties of fresh garlic extracts, aged garlic, garlic oil, and a number of specific organosulfur compounds generated by processing garlic. These anticarcinogenic and antitumorigenic characteristics appear to arise through both dose- and temporal-related changes in a number of cellular events involved with the cancer process, including those involving drug metabolism, immunocompetence, cell cycle regulation, apoptosis, and angiogenesis. The ability of garlic and related allyl sulfur compounds to block tumors in the colon, lung, breast, and liver suggests general mechanisms that are not tissue specific. Whereas relatively few studies have compared the relative efficacy of water- and lipid-soluble allyl sulfur compounds, those that have when using chemically induced carcinogen models suggest little difference in response, whereas tumor proliferation/apoptosis is highly dependent on the species provided. A shift in sulfhydryl groups, alterations in glutathione:oxidized glutathione ratios, and resultant changes in cellular redox status may be involved in some of the phenotypic changes caused by allyl sulfur compounds. Such changes in thiols by allyl sulfurs may also account for the observed hyperphosphorylation of specific cell cycle proteins and the histone hyperacetylation that has been correlated with suppressed tumor cell proliferation. Whereas the anticarcinogenic and antitumorigenic data to date are impressive, additional studies are needed with more modest exposure to allyl sulfur compounds over prolonged periods. Likewise, additional studies are needed that incorporate transgenic and knockout models to assist in the identification of molecular targets for garlic and its associated allyl sulfur components.

Aged garlic extract induces proliferation and ameliorates gentamicin-induced toxicity in LLC-PK1 cells

Gentamicin (GM)-induced nephrotoxicity limits the use of this antibiotic. It has been shown that aged garlic extract (AGE) and S-allylcysteine (SAC), the most abundant organosulfur compound in AGE, ameliorate GM-induced nephrotoxicity in rats. The present communication evaluated the effect of AGE and SAC on proliferation and on GM-induced toxicity and genotoxicity of porcine kidney epithelial cell line (LLC-PK1 cells). The cells were preincubated with different concentrations of AGE or SAC for 12 h before incubation with 8 mm GM for an additional 72 h. At the end of this time, cell viability, genotoxicity and proliferation were evaluated. AGE stimulated cell proliferation and protected LLC-PK1 cells from GM-mediated toxicity and genotoxicity. SAC partially prevented only GM-induced genotoxicity. These results suggest that the stimulation of cell proliferation could possibly be one of the mechanisms involved in the in vitro protective effect of AGE in GM-induced toxicity of LLC-PK1 cells.

Dietary HDAC inhibitors: time to rethink weak ligands in cancer chemoprevention?

There is growing interest in the various mechanisms that regulate chromatin remodeling, including modulation of histone deacetylase (HDAC) activities. Competitive HDAC inhibitors disrupt the cell cycle and/or induce apoptosis via de-repression of genes such as P21 and BAX, and cancer cells appear to be more sensitive than non-transformed cells to trichostatin A and related HDAC inhibitory compounds. This apparent selectivity of action in cancer cells makes HDAC inhibitors an attractive avenue for drug development. However, in the search for potent HDAC inhibitors with cancer therapeutic potential there has been a tendency to overlook or dismiss weak ligands that could prove effective in cancer prevention, including agents present in the human diet. Recent reports have described butyrate, diallyl disulfide and sulforaphane as HDAC inhibitors, and many other dietary agents will be probably discovered to attenuate HDAC activity. Here we discuss 'pharmacologic' agents that potently de-repress gene expression (e.g. during therapeutic intervention) versus dietary HDAC inhibitors that, as weak ligands, might subtly regulate the expression of genes involved in cell growth and apoptosis. An important question is the extent to which dietary HDAC inhibitors, and other dietary agents that affect gene expression via chromatin remodeling, modulate the expression of genes such as P21 and BAX so that cells can respond most effectively to external stimuli and toxic insults.

Differential effects of allyl sulfides from garlic essential oil on cell cycle regulation in human liver tumor cells

In this study, diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS), which are major organosulfur compounds (OSCs) of garlic, were used as experimental materials to investigate their modulation effects on cell viability and cell cycle in human liver tumor cells (J5). According to the results of cell viability assay, 50 or 100 microM DATS significantly decreased the cell viability as compared with the control (P < 0.05) in dose and time dependent relations. Phenomena of cell number loss, shape deformation and lysis were observed after treatment with 100 microM DATS for 24 h. Cell cycle studies showed that J5 cells were significantly arrested in G2/M phase as the cells were treated with 100 microM DADS, 10, 50 or 100 microM DATS for 24 h (P < 0.05). DATS was more effective in arresting cells in G2/M phase than DADS, and the phenomena of arresting J5 cells in G2/M phase increased obviously in dose and time dependent relations. According to the Western blot analysis, DATS decreased cyclin-dependent kinase (Cdks)-Cdk7 (i.e. Cdc2 activate kinase) protein levels in J5 cells but increased cyclin B1 protein level. The modulation potency to cyclin B1 and Cdk7 expressions was in the order of DATS > DADS > DAS. The modulation potency to cyclin B1 and Cdk7 protein levels increased with increasing in DATS concentration and culture time. In conclusion, DATS might affect cell viability and cell morphological changes in J5 cells and lead cells to be arrested in G2/M phase via controlling the expression of cyclin B1 and Cdk7 in J5 cells, and the controlling action might relate to the sulfuric atom numbers in the structures of all these allyl sulfides.

Functional foods, herbs and nutraceuticals: towards biochemical mechanisms of healthy aging

Aging is associated with mitochondrial dysfunctions, which trigger membrane leakage, release of reactive species from oxygen and nitrogen and subsequent induction of peroxidative reactions that result in biomolecules' damaging and releasing of metals with amplification of free radicals discharge. Free radicals induce neuronal cell death increasing tissue loss, which could be associated with memory detriment. These pathological events are involved in cardiovascular, neurodegenerative and carcinogenic processes. Dietary bioactive compounds from different functional foods, herbs and nutraceuticals (ginseng, ginkgo, nuts, grains, tomato, soy phytoestrogens, curcumin, melatonin, polyphenols, antioxidant vitamins, carnitine, carnosine, ubiquinone, etc.) can ameliorate or even prevent diseases. Protection from chronic diseases of aging involves antioxidant activities, mitochondrial stabilizing functions, metal chelating activities, inhibition of apoptosis of vital cells, and induction of cancer cell apoptosis. Functional foods and nutraceuticals constitute a great promise to improve health and prevent aging-related chronic diseases.

Diallyl trisulfide-induced apoptosis in human prostate cancer cells involves c-Jun N-terminal kinase and extracellular-signal regulated kinase-mediated phosphorylation of Bcl-2

Garlic-derived organosulfides (OSCs) including diallyl trisulfide (DATS) are highly effective in affording protection against chemically induced cancer in animals. Evidence is also mounting to indicate that some naturally occurring OSCs can suppress proliferation of cancer cells by causing apoptosis, but the sequence of events leading to proapoptotic effect of OSCs is poorly defined. Using PC-3 and DU145 human prostate cancer cells as a model, we now demonstrate that DATS is a significantly more potent apoptosis inducer than diallyl sulfide (DAS) or diallyl disulfide (DADS). DATS-induced apoptosis in PC-3 cells was associated with phosphorylation of Bcl-2, reduced Bcl-2 : Bax interaction, and cleavage of procaspase-9 and -3. Bcl-2 overexpressing PC-3 cells were significantly more resistant to apoptosis induction by DATS compared with vector-transfected control cells. DATS treatment resulted in activation of extracellular-signal regulated kinase 1/2 (ERK1/2) and c-jun N-terminal kinase 1 (JNK1) and/or JNK2, but not p38 mitogen-activated protein kinase. Phosphorylation of Bcl-2 in DATS-treated PC-3 cells was fully blocked in the presence of JNK-specific inhibitor SP600125. Moreover, JNK inhibitor afforded significant protection against DATS-induced apoptosis in both cells. DATS-induced Bcl-2 phosphorylation and apoptosis were partially attenuated by pharmacological inhibition of ERK1/2 using PD98059 or U0126. Overexpression of catalase inhibited DATS-mediated activation of JNK1/2, but not ERK1/2, and apoptosis induction in DU145 cells suggesting involvement of hydrogen peroxide as a second messenger in DATS-induced apoptosis. In conclusion, our data point towards important roles for Bcl-2, JNK and ERK in DATS-induced apoptosis in human prostate cancer cells.

The effects of allyl sulfides on the induction of phase II detoxification enzymes and liver injury by carbon tetrachloride

Allyl sulfides, e.g., diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), are principal constituents of garlic oil. In the present study, we investigated the in vivo effect of these sulfides on the phase I and phase II drug-metabolizing enzymes, and elucidated their structure-function relationship. A highly purified form of each sulfide (more than 99% purity) was administered i.p. as a bolus to rats at a concentration of 10 or 100 micromol/kg body weight for 14 consecutive days. As to the phase I enzymes, DAS (100 micromol/kg) slightly but significantly increased cytochrome P-450 (CYP) 2E1 activity (1.6-fold vs. control), whereas DADS and DATS did not affect it or the hepatic total CYP level or CYP1A1/2 activity. With respect to the phase II enzymes, DATS (10 micromol/kg) and DADS at a 10-fold higher dose (100 micromol/kg) significantly increased the activities of glutathione S-transferase, quinone reductase, and antioxidative enzyme glutathione peroxidase; whereas DAS did not. In the carbon tetrachloride (CCl4)-induced acute liver injury model of rats, either DATS (10 micromol/kg) or DADS (100 micromol/kg) significantly reduced the injury caused by the induction of phase II enzymes with CCl4. In conclusion, the sulfides affected both phase I and phase II enzymes, the former being stimulated by the monosulfide only and the latter, strongly by the trisulfide and weakly by the disulfide. Therefore, the polysulfide DATS may be one of the important factors in garlic oil that protects our body against the injury caused by radical molecules encountered in daily life.

The use of nutraceuticals in cancer therapy

The high prevalence of nutraceutical use among human patients with cancer suggests that the use of nutraceuticals in pet animals with cancer is probably common. Dogs with a wide variety of malignant diseases have significant alterations in carbohydrate, protein, and fat metabolism. These metabolic alterations may be ameliorated by using functional foods relatively low in soluble carbohydrate, moderate amounts of protein that includes sources of arginine, and moderate amounts of fat supplemented with omega-3 long-chain polyunsaturated fatty acids. Well-controlled clinical studies in a variety of species with cancer, including rodents, people, and dogs, have documented that increased dietary and serum levels of omega-3 fatty acids are associated with a number of health benefits, including improved disease-free interval, survival time, and quality of life. Other nutraceuticals of interest in patients with cancer include antioxidant vitamins, trace minerals, glutamine, protease inhibitors, garlic, tea polyphenols, vitamin A, and shark cartilage.