Abstract
The chemopreventative benefit of a whole foods diet is often attributed to phytochemicals, such as terpenoids and polyphenols, found in fruits, vegetables, and grains. Spices, which tend to have high concentrations of these classes of potentially therapeutic agents, have not garnered the same amount of attention until relatively recently. Many spices, including cardamom, cinnamon, black pepper, clove and ginger, have shown promise as chemopreventative and therapeutic agents in cancer. In vitro and in vivo, each of these compounds has demonstrated potent anti-inflammatory and antitumorigenic properties. Thus, chai tea, which contains a combination of all the aforementioned spices, represents an enjoyable means of chemoprevention.
Introduction
The word “chai” in English is an adjective designating a type of tea, but the term “chai” literally means “tea” in Hindi. What is commonly called “chai tea” in the United States is more precisely spiced tea or “masala chai” in India. To simplify, the term chai will mean “masala chai” herewith. Traditionally, chai is made of a base of water and milk to which black tea and spices such as cardamom, cinnamon, clove, ginger, and black pepper are
added. The chai is then decocted for a minimum of 20 minutes.
This spiced tea is ubiquitous throughout India with some variations by region. All of the spices in chai have been independently shown to inhibit or suppress inflammation as well as tumorigenesis. Since chai is easily procured in Western countries, and the spices in it have all been shown to have antioxidant, antiinflammatory, and anticancer effects, chai consumption may be an effective, enjoyable means of chemoprevention.
At a molecular level, the crux of many chronic degenerative diseases, including tumorigenesis, is the inflammatory process.1 While acute inflammation is a necessary immunological process for tissue recovery from damage or infection, chronic inflammation can cause cellular changes that can eventually affect cellular structure and function. Pro-inflammatory molecules such as nuclear factor kappa B (NF-kB), tumor necrosis factor alpha (TNF-α), interleukins 1β and 6 (IL-1β, IL-6), and the chemokine interleukin-8 (IL-8) are examples of molecules that are involved in the process of tumorigenesis as well as malignant proliferation, invasion, angiogenesis, and metastasis. In addition to these pro-inflammatory mediators, enzymes that upregulate inflammation, such as cyclooxygenase-2(Cox-2), inducible nitric oxide synthase (iNOS), 5-lipogenase (5-LOX), and phospholipase A2, lead to increased production of pro-inflammatory prostaglandins and leukotrienes. Lastly, reactive oxygen species (ROS) contribute to intracellular stress and may trigger the release of further inflammatory mediators in addition to causing direct DNA damage. The net effect of the cellular changes of chronic inflammation is a destabilizing of chromosomal DNA.
Destabilization of DNA allows for the myriad mutations, translocations, and silencing of various genes that are necessary components of tumorigenesis and malignant growth. Therefore, the inflammatory process is a rational therapeutic target to mitigate these cancerous processes; indeed much of the research on chemoprevention through diet has postulated this effect.2
Cancerous growth and metastasis is marked by the ability of cancerous cells to evade apoptosis, invade surrounding tissue, grow new blood vessels, and gain motility—all while evading immune recognition. Many of the genes involved in these processes have been characterized. Bcl-2 and Bax are anti-apoptotic and pro-apoptotic genes, respectively. The ratio of expression of these 2 genes influences whether a cell will ultimately undergo apoptosis through caspase activation. Well-characterized tumor suppressor genes, such as p53 and p27, are often
silenced in malignant cells, conferring a survival advantage. Cell adhesion molecules (CAMs) are involved in cell-to-cell communication and the stability of gap junctions, and loss of properly functioning CAMs is an integral part of tumor growth and metastasis. Angiogenic factors such as vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) participate in a signaling cascade between immune cells, malignant cells, and the vascular endothelium that ultimately leads to new blood vessel growth. Within the extracellular matrix (ECM), degradation enzymes such as matrix metalloproteinases (MMPs), aid in the metastatic process by creating a more hospitable environment for cancer cells to travel through. These are just a few of the hundreds of molecules involved in conferring survival, proliferation, invasion, and angiogenic and metastatic potential to tumors. All these malignant processes are stimulated, either directly or indirectly, by inflammatory mediators.
Anti-inflammatory/Anticancer Effects in Vitro and in Vivo
Many of the bioactive compounds in spices are found in the essential oils of the plants and are dominated by highly volatile phenolic compounds, including many terpenoids. The characteristic aroma and flavor profile of each spice is often dominated by a specific constituent: cinnamaldyhyde (cinnamon), piperine (black pepper), or gingerol (ginger). Highly complex aromas, such as that of clove and cardamom, lack dominant compounds but comprised distinctive combinations of many of them. Many constituents of interest are found across numerous spices (eg, limonene, thymol, cinnamaldehyde, menthol, pinenes), creating an endless array of overlapping and possibly synergistic therapeutic combinations.
Many of the bioactive compounds in spices are found in the essential oils of the plants and are dominated by highly volatile phenolic compounds, including many terpenoids.
Clove
(Syzygium aromaticum, synonyms: Eugenia aromaticum or Eugenia caryophyllata)
The main constituents in clove are polypropenoids and include thymol, carvacol, cinnamaldyhyde, and eugenol.3 Eugenol, which accounts for the majority of the essential oil of the plant, has been well proven to possess antioxidant effects, which lower the generation of ROS within cells and presumably lowers the mutagenic potential of ROS.4,5 In contrast, eugenol has also been shown to generate ROS in HL-60 promyelocytic leukemic cell line, which led to increased mitochondrial permeability and ultimately increased apoptosis through cytochrome c release.6
In a model of inflammation using LPS-stimulated macrophages, eugenol inhibited cox-2 expression and cell growth of HT-29 colon cancer cells in vitro.7 Inhibition of cox-2 expression as well as inhibition of superoxide dismutase (SOD) was also proposed as the mechanism for the cytotoxic effects of eugenol on HL-60 leukemic cells in vitro.8 In this latter study, the cytotoxic effects were potentiated by the addition of glutathione (GSH) or N-acetylcysteine (NAC).
Eugenol’s effect on melanoma cells is inconsistent with growth inhibition in vitro and in vivo in one publication,9 later refuted by a study that was unable to show any effects of eugenol on melanoma cells.10
In a mouse model of chemically induced lung cancer, an aqueous extract of clove significantly lowered the incidence of dysplasia, metaplasia, and carcinoma in situ. Favorable changes in the clove group included the increased expression of p53 and Bax, as well as downregulation of Bcl-2, which led to increased apoptosis. Cox-2 expression was also downregulated in the mice receiving clove extract.11
Hydroethanolic extracts of clove lowered the expression in vitro and in vivo of pro-inflammatory cytokines IL-1βand IL-6.12 The anti-inflammatory effects of eugenol were corroborated by in vitro data showing inhibition of 5-lipogenase production in polymorphonuclear cells.13
Ginger
(Zingiber officinale)
Ginger is a commonly used anti-inflammatory in herbal medicine. Of the many active constituents in ginger, the gingerols (6,8,10-), zingerone, and shagoal are well-established anti-inflammatory compounds.
In the last two decades, mechanisms of ginger’s anti-inflammatory effects have been elucidated and include the reduction of prostaglandins, Cox-1 and Cox-2 expression, and leukotriene synthesis through 5-LOX blockage.14 Ginger may also inhibit the production of TNF-α, IL-1β, and IL-12, as demonstrated in murine peritoneal macrophages exposed to 6-gingerol in the presence of LPS stimulation.15
In gerbils given standardized ginger extract before and after infection with H. pylori, a significant reduction in mucosal and submucosal inflammation was found in addition to growth inhibition of the H. pylori. This study also demonstrated a reduction in IL-1β, IL-6, and TNF in polymorphonuclear (PMN) cells as well as a 50% reduction in cox-2 expression in vitro.16 H. pylori is implicated as a causative agent for several cancers, including
cancer of the stomach.
In mouse models of skin cancer, 6-gingerol inhibited tumorigenesis and decreased chemically induced inflammation when applied topically.17 In a separate study confirming the chemopreventative effects of 6-gingerol on skin cancer, apoptosis was upregulated in tumors that were treated with 6-gingerol versus those that were untreated. There was also upregulation of the expression of p53 and the pro-apoptotic Bax molecule,
with down regulation of anti-apoptotic molecules survivin and Bcl-2. As expected, the net effect was a measurable increase in the levels of apoptotic caspases confirming the induction of apoptosis with 6-gingerol.18
In a rat model of colon adenocarcinoma, whole ginger extract as well as 6-gingerol demonstrated reduction in proliferation as well as endothelial budding of angiogenesis. Interestingly, the lower doses of 6-gingerol (4uM) worked more effectively than the high doses (100uM).19
An in vitro study of breast cancer cells (MDA-MB-231 cells) showed inhibition of adhesion, invasion, and motility
and a reduction in matrix metalloproteinases 2 and 9 (MMP-2, MMP-9) with gingerol.20 6-gingerol also demonstrated antiangiogenic and antimetastatic potential in vitro and in vivo, respectively. In vitro, 6-gingerol reduced endothelial budding in the presence of VEGF. When given to mice injected with a melanoma cell line, 6-gingerol reduced the number of metastatic lung lesions without any apparent toxic effects.21
The vast majority of the research into the mechanisms of ginger’s effects has been on 6-gingerol. However, some studies suggest that other components of the root may be more potent inhibitors of inflammation.22 While ginger phenols, including the gingerols and 6-shagoal, showed inhibition of proliferation and angiogenesis in epithelial ovarian cancer cell lines, shagoal demonstrated greater reductions in NF-κB activation and TNF-α and IL-8 expression.23
Zingerone, a product formed when 6-gingerol is exposed to heat, has been shown to reduce ROS in normal cells, thus suppressing NF-κB activation and subsequent expression of proinflammatory mediators Cox-2 and iNOS.24
In one in vitro experiment, 6-shagoal was able to induce apoptotic cell death via an oxidative stress medicated caspase dependent mechanism. In this experiment, Mahluvu cells, which are poorly differentiated, and mutant p53 hepatoma cells, which are highly resistant to chemotherapeutics and radiotherapy, were used. Of note, the apoptotic effects of 6-shagoal were completely mitigated by the addition of NAC or reduced glutathione to the medium.25
Black Pepper
(Piper nigrum)
Black pepper is the most ubiquitous spice worldwide and its use in cooking in India dates back to at least 2000 BC. Black pepper contains many bioactive constituents including piperine, limonene, pinene, and terpinolene.26 It also contains safrole, a known carcinogenic substance whose presence is likely mitigated by the other constituents in black pepper such as limonene.27 The alkaloid piperine is responsible for imparting black pepper’s characteristically pungent taste. Piperine has been shown to possess antioxidant activity.28
The antimetastatic potential of piperine was demonstrated in a mouse model of lung metastasis from melanoma. In mice given piperine, there was a significant reduction in the size and number of lung metastasis. As expected, there was also an increase in the longevity of the treated mice.29
In cultured human colon cancer cells, piperine reduced the proliferation of cells at doses that are roughly equivalent to those obtained from frequent consumption in the diet.30
Piperine is well known to affect the bioavailablity and pharmacodynamics of many drugs and botanicals.31,32 Given its known effect of enhancing bioavailability of substances while reducing their metabolism, it is possible though not proven that piperine acts to potentiate the effectiveness of the other spice constituents in found in chai.
Cardamom
(Elettaria cardamomum)
Cardamom is a highly aromatic and distinctive spice possessing 8% essential oils. Constituents in cardamom include 1,8 cineole, alpha-terpinyl acetate, limonene, and myrcene along with many other volatile terpenoids.26
In a mouse model of colon carcinogenesis, a chemical (azoxymethane) is used to induce colonic aberrant crypt foci. The addition of aqueous extract of cardamom to the mice’s chow significantly reduced carcinogenic changes in this model. There were also a decrease in proliferation, an increase in apoptosis and reductions in the formation of proinflammatory mediators, Cox-2 and iNOS.33 Further, the mice given cardamom had increased antioxidative capacity through upregulation of GST.34
In a study supporting the possible role of cardamom in reducing gastrointestinal inflammation, the constituent 1,8
cineole demonstrated a reduction in chemically induced colitis in rats.35 1,8 cineole (eucalyptol) is a terpenoid compound that has been shown to possess anti-inflammatory capacity in the rat paw edema model of inflammation.36 In vitro, 1,8 cineole demonstrated reduction of TNF-alpha and IL-1βsecretion from monocytes and lymphocytes.37
Cinnamon
(Cinnamomum spp.)
Crude aqueous extract of whole cinnamon bark inhibited growth of lymphoma and leukemia cell lines in a dose-dependent manner.38 A hot water extract of crude Cinnamomum cassia (“Chinese cinnamon”) bark demonstrated decreased expression of pro-angiogenic factors (EGF, VEGF, TGF-β and HIF-1) in vitro. The same
group demonstrated that 10 mg of orally or intraperitoneally delivered cinnamon extract was able to inhibit the growth of melanoma in a mouse model.39
Cinnamaldehyde induced apoptosis of HL-60 (proleukemic) cells through the production of ROS and resultant increase in mitochondrial cytochrome c release. This effect was abrogated by the addition of NAC.40
In an in vitro study, cinnamaldehyde reduced melanoma cell proliferation, angiogenesis, and tumor growth through NF-κB inhibition, caspase-8 induction, and IL-8 inhibition.41 Reduction of the activation of NF-κB was corroborated in an in vitro study directly assessing inactivation by trans-cinnamaldehyde and its naturally occurring derivative 2-methoxycinnamaldehyde.42
In a rat model of tumorigenesis, cinnamaldehyde reduced the incidence of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)–induced lung tumors when given at 5000 ppm orally.43 Apoptotic pathways involving Bcl-2, caspase-8 and mitogen activated protein kinase (MAPK) have been shown to contribute to the apoptotic capacity of cinnamaldehyde.44
Discussion
Extensive epidemiological data has established that fruits and vegetables in the diet reduce the risk of cancer. Phytochemicals from fruits and vegetables have shown inhibition or suppression of many of the tumorigenic pathways mentioned above.45 Spice consumption, however, has not been looked at as a separate influence on chronic degenerative diseases epidemiologically. While mechanistically there is reason to postulate that spices
have a significant contribution in preventing disease, population studies have proven difficult as the use of spices often correlates with many other diet and lifestyle variables.
While direct epidemiological data on the protective effect of spice consumption is lacking, Aggarwal et al postulated that the high spice usage in India may contribute to the vastly lowered rate of colon cancer in that population. He reports the incidence of colon cancer in the United States in 2000 was 356 people per million, causing 139 deaths/million. In contrast, the incidence of colon cancer in India in 2000 was 40 cases per million, and 26 deaths/million. Meanwhile, spice production and consumption is tenfold higher in India versus the United States.46 While there are confounding cultural differences that may contribute to this dramatic difference, the ingestion of spices with a particularly high consumption of turmeric and the herbs in chai may account for some of the protective effect. At least one in vitro study assessing the protective effects of cinnamon and black pepper extracts on colon cancer development corroborates this hypothesis.30
In India, milk is usually included during the decoction process, which presumably extracts fat-soluble phytochemicals in addition to the water-soluble components. From an ethnobotanical perspective, it is possible that the compounds in this lipophilic medium may confer greater benefit compared to pure water extraction, although this has not been proven. In keeping with this traditional usage and respecting the complexity of the myriad of active constituents in chai, future studies should be done using a lipophilic medium in addition to the commonly
used water extract.
Although the traditional consumption of chai includes black tea, epidemiological data on black tea itself has conflicting data of its protective or promotive effects in cancer.47,48,49,50 Unlike the spices that are added to the tea, which have overwhelming in vitro and in vivo data suggesting protection from the consumption of these plants, the inconclusive data on black tea gives pause to its inclusion in a chemopreventative beverage. In contrast, green tea, which is derived from the same plant (Camilla senensis) but does not undergo the oxidative processing of black tea, is an extremely well-established chemopreventative.51 One solution is to omit the black tea altogether from the
chai; another more plausible solution is to include green tea in its place, perhaps increasing the beneficial potential of the drink.
It should be noted that this review is limited in scope to the direct and indirect cellular effects of the spices in chai and its constituents. Many other biological effects, including influence on endocrine function, immune function and liver biotransformation pathways are beyond the scope of this review. It is quite likely that the favorable biological effects involving blood sugar regulation and systemic immune modulation contribute to the chemopreventative effects of many of the spices in chai.52,53,54 In addition, influences on biotransformation within the liver, such as cytochrome P450 enzymes, glucaronidation, sulfation, or methylation may contribute to biological benefits derived from spices.55,56,57
Spices may impart some of their chemoprotective effects through their antimicrobial actions as well. Many of the spices used in chai were traditionally used to prevent food from spoiling, and to the extent that some cancers are caused by infectious agents, prevention of such cancers would be expected.58 The antimicrobial effects may have protective action through limiting the growth of exogenous carcinogenic organisms such as aspergillus,59,60,61 which can infect food supplies, or by affecting endogenous organisms implicated in cancer causation such as H. pylori.62
As a final testament to the potential of the constituents in spices for potent chemoprevention, pharmaceutical research is delving into creating patentable analogs of many of the active constituents.63 Since spices constitute a nontoxic means of accessing these compounds in our diet, there may be little incentive to use such patentable alternatives in chemoprevention.
Conclusion
Inflammation, as defined by inflammatory mediators at the site of a tumor, stimulate cancerous processes from tumorigenesis through progressive stages of proliferation, angiogenesis, and metastasis. Therefore, any agents that can mitigate inflammation have therapeutic potential throughout this cancer continuum. Spices have a long history of safe usage in both diet and beverages. Spices also contain many constituents with potent, demonstrated anti-inflammatory and antitumorigenic properties. Chai, a simple combination of cinnamon, cardamom, clove, ginger, and black pepper represents an easily integrated means of including many spices that have evidence
of anti-inflammatory, antioxidant, and antitumor effects. The pleasant taste and easy access to these spices add to the practical application of this simple tea.
