Berry-derived Bioactive Compounds as Chemopreventive Agents in Colorectal Cancer: Molecular Mechanisms and Gut Microbiota Interactions

Abstract

Berry-derived bioactive compounds are increasingly recognized as promising chemopreventive agents for colorectal cancer (CRC). CRC develops through a multistep process involving genetic, epigenetic, inflammatory, and microbiota-related alterations. Polyphenol-rich berries are abundant in anthocyanins, ellagitannins, ellagic acid, quercetin, and related phytochemicals. These compounds target multiple hallmarks of colorectal carcinogenesis. Experimental studies have shown that berry-derived compounds exert anti-proliferative effects by inducing cell-cycle arrest at the G0/G1, S, or G2/M phase. These effects are associated with modulation of cyclin-dependent kinases (CDK), and CDK inhibitors such as p21 and p27. In addition, they inhibit key oncogenic signaling pathways, including Wnt/β-catenin, NF-κB, PI3K/Akt, and ERK/MAPK. Berry phytochemicals also promote programmed cell death. Thus, they activate both intrinsic and extrinsic apoptotic pathways, alter the balance of Bcl-2 family proteins, disrupt mitochondrial integrity, and induce caspase activation. Moreover, berry compounds attenuate chronic inflammation by downregulating expression/production of COX-2, inducible nitric oxide synthase, and pro-inflammatory cytokines through suppression of NF-κB– and STAT3–dependent signaling. Further, they also enhance Nrf2-mediated antioxidant responses. Although parent polyphenols have limited bioavailability, they are extensively metabolized by gut microbiota into bioactive compounds such as protocatechuic acid and urolithins. These metabolites often exhibit comparable or greater anticancer activity and reach physiologically relevant concentrations in the colorectum. Berry polyphenols further modulate gut microbiota composition, promoting beneficial microbes and reinforcing anti-carcinogenic signaling. Altogether, these mechanisms highlight berry-derived compounds as strong candidates for CRC chemoprevention, which merits further clinical investigation.

INTRODUCTION

Gastrointestinal cancers constitute a major global health challenge and are associated with substantial mortality worldwide [1]. Cancer development is a highly complex, multistep process. It is driven by interactions between inherited susceptibility and diverse environmental exposures [2]. Epidemiological analyses indicate that approximately one fifth of all malignancies are attributable to infectious agents. Prominent examples include Helicobacter pylori, hepatitis B virus, hepatitis C virus, and human papillomavirus [2,3]. In addition to these well-established oncogenic pathogens, converging evidence demonstrates pronounced alterations in gut microbial composition in patients with colorectal cancer (CRC). These changes, when compared with healthy individuals, implicate the intestinal microbiota as an important contributor to colorectal carcinogenesis [4,5].

Emerging evidence indicates that specific microbial species and their metabolites can exert dual and context-dependent effects on tumorigenesis. In some settings, they promote malignant transformation, whereas in others they inhibit it, acting through diverse molecular and immunological mechanisms. Notably, the gut microbiome has been implicated in the modulation of host gene expression. This includes the dysregulation of non-coding RNAs (ncRNAs), which function as key regulators of both oncogenic and tumor-suppressive pathways [6,7]. In parallel, bioactive compounds derived from medicinal plants, fruits, vegetables, and berries have shown substantial anticancer activity. These phytochemicals contribute to cancer chemoprevention and support broader health-promoting effects [8,9].

Among gastrointestinal malignancies, CRC is the third most commonly diagnosed cancer worldwide. It is also the second leading cause of cancer-related mortality [10-12]. This substantial epidemiological burden has brought chemoprevention to the forefront of CRC management strategies. Chemoprevention involves the use of safe or relatively non-toxic natural or synthetic agents to inhibit, delay, or reverse the process of carcinogenesis, particularly at premalignant stages. By targeting early molecular and cellular alterations, this approach has the potential to reduce both CRC incidence and associated mortality [13]. A broad spectrum of naturally occurring dietary constituents shows protective effects against colorectal carcinogenesis. These include fiber, vitamins, and minerals. They also include phytochemicals such as alkaloids, carotenoids, and polyphenols [14,15].

Population-based epidemiological studies indicate that the incidence of CRC is substantially lower in Asian populations than in Western populations. The disparity stems largely from different dietary patterns. High consumption of red and processed meats links consistently to elevated CRC risk. In contrast, diets rich in whole grains, dietary fiber, and phytochemical-dense foods show protective associations [16]. Notably, anthocyanin-rich dietary patterns significantly attenuate CRC risk. They counteract pro-inflammatory and pro-tumorigenic processes which characterize Western dietary exposures [17]. The consumption of nitrite-containing processed meats worsens the risk. High-temperature cooking promotes production of heterocyclic amines in these meats. These compounds have well-established carcinogenic activity in the colorectum [18-20]. Nevertheless, CRC etiology involves more than environmental and dietary factors. Heritable genetic susceptibility is an independent and significant risk factor.

Gut microbiome dysbiosis is increasingly recognized as a key contributor to gastrointestinal carcinogenesis. It disrupts epithelial barrier integrity and promotes a pro-inflammatory environment that enhances malignant transformation. Dysbiotic communities generate genotoxic and pro-tumorigenic metabolites while altering the immune responses. Specific microbes, such as H. pylori in gastric cancer and Fusobacterium nucleatum in CRC, exemplify how individual microorganisms can drive oncogenic signaling and shape the tumor microenvironment. Microbial metabolites, including short-chain fatty acids, further modulate host cell proliferation, apoptosis, and epigenetic regulation. In parallel, microbiome-linked non-coding RNAs are emerging as important molecular mediators that connect microbial signals to host gene expression programs relevant to tumor initiation and progression [6].

CRC develops through a multistep process characterized by the progressive accumulation of genetic and epigenetic alterations. These changes include the inactivation of tumor suppressor genes, defects in DNA mismatch repair mechanisms, and activation of oncogenes. Mutations in the tumor suppressor gene p53 are commonly observed in advanced stages of CRC, whereas mutations in K-ras tend to occur earlier during tumor initiation [21,22]. Approximately 85% of CRC cases arise from benign adenomatous polyps, highlighting the importance of early detection and timely preventive interventions [23]. In addition, hereditary syndromes such as familial adenomatous polyposis (FAP) demonstrate the genetic heterogeneity underlying CRC pathogenesis. FAP is primarily caused by germline mutations in the adenomatous polyposis coli (APC) gene, which lead to dysregulated cellular proliferation. Aberrant signaling pathways, including those involving the epidermal growth factor receptor (EGFR), may further contribute to disease progression [24].

Chemotherapy remains a cornerstone of cancer treatment. However, its clinical efficacy is frequently compromised by the development of acquired drug resistance, as well as dose-limiting toxicities that restrict its long-term use. These challenges significantly reduce therapeutic outcomes and patient tolerability. Cetuximab, a monoclonal antibody targeting the EGFR, has demonstrated measurable clinical benefit in CRC. Nevertheless, its use is commonly associated with adverse effects, particularly dermatological and ocular toxicities [25-27]. These limitations have prompted increasing research interest in alternative strategies, particularly the investigation of naturally derived compounds that exhibit chemopreventive potential alongside more favorable safety profiles.

CHEMOPREVENTIVE AND ANTICARCINOGENIC PHYTOCHEMICALS

An increasing body of evidence supports the anticancer potential of plant-derived bioactive compounds. Cruciferous vegetables are particularly rich in glucosinolates and organosulfur compounds. These constituents exert anticancer effects through multiple mechanisms, including enhancement of carcinogen detoxification, protection against oxidative DNA damage, induction of cancer cell, and inhibition of angiogenesis and metastatic progression [28].

Garlic-derived organosulfur compounds, especially diallyl disulfide, have demonstrated broad-spectrum anticancer activity. These compounds modulate key processes involved in tumor progression, including epithelial–mesenchymal transition, cellular invasion, and migration [29]. Theanine, a non-proteinogenic amino acid found in tea, also exhibits notable anticancer properties. It regulates several oncogenic signaling pathways, including EGFR, vascular endothelial growth factor receptor (VEGFR), Janus kinase/STAT3, and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR). In addition, theanine selectively induces apoptosis in cancer cells while exerting minimal cytotoxic effects on normal cells [30]. Furthermore, isoflavones such as biochanin A contribute to cancer chemoprevention through their anti-inflammatory and anti-proliferative activities [31].

Among naturally derived chemopreventive components, berry-derived bioactive compounds have attracted considerable scientific interest in CRC research. Polyphenolic constituents contained in various species of berry, including anthocyanins, ellagitannins, ellagic acid, and quercetin, have been extensively studied for their biological activities. These compounds exert multiple anticancer effects, such as inhibiting tumor cell proliferation, inducing apoptosis, and modulating inflammatory signaling pathways. Evidence supporting these effects has been consistently reported across in vitro, in vivo, and early-phase clinical studies [32-34]. In addition to their direct cellular actions, these berry-derived bioactive compounds can alter the composition and function of the gut microbiota. This modulation enhances their chemopreventive potential through complex microbial–host interactions, further contributing to CRC prevention [35].

Flavonoids constitute a structurally diverse class of plant secondary metabolites that have been extensively investigated for their antioxidant, anti-inflammatory, antimicrobial, and anti-tumor properties. Specific flavonoids, including apigenin, luteolin, and naringenin, have demonstrated notable biological activities. These compounds can suppress tumor growth and may alleviate chemotherapy-induced adverse effects, highlighting their potential as adjunctive agents in cancer therapy [36,37].

Anthocyanins represent a particularly bioactive subclass of flavonoids. They are responsible for the characteristic red, purple, and blue pigmentation of many berries. Experimental studies have shown that anthocyanins can induce apoptosis, arrest cell cycle progression, and inhibit tumor invasion and metastasis [38-40]. Berry species such as raspberry, chokeberry, and bilberry are especially rich sources of these compounds.

Ellagitannins are a class of polyphenolic compounds found in fruits, berries, nuts, and other plant-based foods. They have attracted attention because of potential anticancer and health-promoting activities, including antioxidant, anti-inflammatory, and chemopreventive effects. In addition, their gut microbiota-derived metabolites, especially urolithins, may contribute to some of these biological activities and help explain their broader relevance to human health [41]. Ellagitannins undergo hydrolysis slowly in the gastrointestinal tract to form ellagic acid.

Ellagic acid is a naturally occurring polyphenolic compound widely distributed in fruits, nuts, and several medicinal plants, particularly in pomegranates, berries, walnuts, and raspberries. Extensive studies have demonstrated that ellagic acid exerts multifaceted anti-tumor effects through a range of molecular mechanisms. These effects include the induction of apoptosis, inhibition of cell proliferation and angiogenesis, and suppression of cancer cell migration and invasion. In addition, ellagic acid modulates key signaling pathways involved in tumor progression, including PI3K/Akt, VEGFR-2, Notch, and TGF-β/Smad3 pathways. Ellagic acid is poorly absorbed in its native form and undergoes extensive biotransformation by gut microbiota to urolithins, which constitute its major circulating metabolites [41]. Urolithins show markedly higher bioavailability than ellagic acid and exhibit potent anti-inflammatory, antioxidant, and antiproliferative activities. Such microbial metabolites are therefore considered critical mediators of the tumor-suppressive and broader health-promoting effects attributed to ellagic acid [42,43].

Quercetin is a dietary flavonol abundant in fruits and vegetables that has attracted considerable interest for its pleiotropic anti-tumor and health-promoting properties. Experimental studies show that quercetin can inhibit cancer cell proliferation, induce apoptosis, modulate cell cycle regulation, and interfere with key oncogenic signaling pathways. These result in suppression of tumor growth and progression. Quercetin undergoes extensive biotransformation by the gut microbiota, which convert the parent flavonol into distinct low-molecular-weight phenolic acids. These include phenylpropanoic, phenylacetic, and benzoic acid derivatives that constitute the predominant circulating microbial metabolites. These metabolites generally exhibit improved bioavailability compared with quercetin itself and retain relevant biological activities. At physiologically attainable concentrations, they contribute to anti-inflammatory and redox-modulating effects, thereby supporting the chemopreventive and broader health-promoting actions attributed to the parent molecule, quercetin [44,45].

Resveratrol is a pleiotropic polyphenolic compound that has attracted considerable attention as a promising anticancer agent. It exerts anti-tumor activity by modulating multiple events associated with cancer growth and progression. These include cancer cell proliferation, apoptosis, angiogenesis, invasion, and metastatic dissemination. Resveratrol is also metabolized by gut bacteria to major microbial metabolites such as dihydroresveratrol and lunularin, which can achieve higher chemopreventive activities than the parent compound after oral intake. These metabolites preserve or enhance key anti-inflammatory and metabolic effects, thereby contributing to the overall anti-tumor and health-promoting actions attributed to resveratrol [46].

This review aims to provide a comprehensive and critical appraisal of the chemopreventive potential of berry-derived bioactive compounds in CRC. It places particular emphasis on their mechanistic roles in regulating cell proliferation, apoptosis, and inflammatory signaling, as well as their metabolic fate and bioavailability in the human gastrointestinal tract.

ANTI-PROLIFERATIVE EFFECTS OF BERRY-DERIVED COMPOUNDS IN CRC CELLS

Uncontrolled cell proliferation represents a key hallmark of early colorectal carcinogenesis, particularly within the colonic crypt compartment. In this microenvironment, an abnormal increase in epithelial cell turnover is widely recognized as a biomarker of tumor initiation [47]. In this context, plant-derived phenolic compounds have gained substantial scientific interest. These compounds are naturally occurring secondary metabolites characterized by the presence of one or more hydroxylated aromatic rings. They exhibit a wide range of biological activities, among which anticancer effects are especially prominent [48].

Berries are among the richest dietary sources of phenolic compounds. These include anthocyanins, flavonoids, and tannins, which are widely distributed across various berry species. Such compounds have been extensively investigated for their capacity to modulate multiple stages of carcinogenesis. They can influence tumor initiation, promotion, and progression, underscoring their broad chemopreventive potential. The biological activity of these phenolic compounds is closely associated with their chemical structure [49,50]. In particular, structural features such as the degree of hydroxylation and the pattern of glycosylation play critical roles in determining their bioactivity [51].

The anti-proliferative effects of berry extracts rich in phenolic compounds (e.g., bilberry, black currant, cloudberry, lingonberry, raspberry, and strawberry) have been investigated in human HT-29 colon cancer cells [52]. These extracts inhibited cell proliferation to a different extent, with bilberry being the most potent and strawberry the least. The antiproliferative activity was associated with marked upregulation of the cyclin-dependent kinase (CDK) inhibitor 1A (p21WAF1 or p21) and a modest increase in the pro-apoptotic protein Bcl-2-associated X protein (Bax). In contrast, cells treated with berry phenolic extracts showed loss or strong reduction of B-cell lymphoma 2 (Bcl-2) expression. These findings suggest that berry phenolics exert chemopreventive effects in colon cancer cells primarily through p21-mediated cell cycle arrest, and also stimulation of pro-apoptotic signaling [52]. Phenolic-rich extracts derived from miracle berry have also demonstrated concentration-dependent inhibition of CRC cell proliferation and viability [53].

A substantial body of in vitro evidence has demonstrated the anti-proliferative activity of berry-derived compounds in diverse CRC cell models. Anthocyanin-rich fractions isolated from blueberry exhibit significantly stronger anti-proliferative effects in the human colorectal adenocarcinoma cell line HT-29 compared with other phenolic subclasses, including phenolic acids, flavonols, and tannins [54].

Comparative analyses across multiple berry species, including chokeberry, bilberry, elderberry, blackberry, raspberry, blueberry, cranberry, and strawberry, have consistently shown growth-inhibitory activity. However, the magnitude of this effect varies depending on the species. Anti-proliferative efficacy is commonly quantified using growth inhibition 50% (GI50) values, where lower values indicate greater inhibitory potency. Among the species evaluated, chokeberry, bilberry, and elderberry consistently demonstrate the strongest anti-proliferative effects. This observation highlights the importance of anthocyanin composition and structural diversity as key determinants of bioactivity [55-57].

The structure–activity relationships that govern anthocyanin bioactivity are of central mechanistic importance. Variations in aglycone configuration and glycosylation patterns play a critical role in determining biological activity. For example, chokeberry is characterized by a predominance of cyanidin-3-glucoside derivatives, whereas bilberry contains a structurally diverse anthocyanidin profile. These compositional differences significantly influence anti-proliferative potency. Anthocyanins suppress CRC cell proliferation primarily through inhibition of the Wingless-type/beta-catenin (Wnt-β-catenin) oncogenic signaling pathway [58,59].

In addition to anthocyanins, ellagitannins represent another important subclass of polyphenols with comparable inhibitory properties. Ellagitannin rich extracts from strawberry have been shown to suppress colon cancer cell growth. Similarly, ellagitannins derived from raspberry exhibit direct cytotoxic effects in CRC cell lines [60,61]. Synergistic interactions between polyphenols and co-occurring micronutrients, such as vitamin C and carotenoids, may further enhance anti-proliferative effects [62]. Moreover, activation of Smad4 expression in colonic epithelium and natural killer cells has been proposed as an additional mechanism by which berry-derived compounds may inhibit CRC progression [63].

At the molecular level, berry polyphenols modulate cellular proliferation through coordinated regulation of cell cycle progression and transcriptional reprogramming. These compounds predominantly induce cell cycle arrest at the G0/G1 or S phase by interfering with critical regulatory proteins. These include downregulation of cyclin D1 and CDK4 and upregulation of the p21 and p27 [32,64-66]. In addition, berry polyphenols downregulate several oncogenic signaling pathways involved in tumor growth including NF-κB, PI3K/Akt, extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK), and Wnt/β-catenin pathways. Through regulation of these oncogenic networks, berry-derived compounds suppress proliferative signaling and enhance apoptotic processes in CRC cells [32,66,67].

Experimental studies have further clarified the phase-specific effects of berry-derived compounds on cell cycle regulation. Repeated exposure of Caco-2 cells to chokeberry juice induces G2/M phase arrest. This effect is accompanied by upregulation of the tumor suppressor carcinoembryonic antigen related cell adhesion molecule 1 (CEACAM1), which is frequently silenced during early stage CRC [68]. Similarly, anthocyanin-rich extracts induce cell cycle arrest at the G0/ G1 phase in HT-29 cells. This response was associated with increased expression of the cyclin dependent kinase inhibitors p21WAF1 and p27KIP1. It is also accompanied by a concurrent reduction in the expression of cyclins A and B [69]. Crucially, these inhibitory effects appear to be largely selective for malignant cells. In contrast, normal colonic epithelial cells exhibit less than 10% growth inhibition under equivalent experimental conditions. Such differential response indicates a potentially favorable therapeutic profile. Berry-derived compounds preferentially target cancer cells while exerting minimal effects on non-transformed tissues [69].

Among non-anthocyanin flavonoids, quercetin is one of the most extensively characterized compounds for its anti-proliferative effects in CRC. It has been shown to inhibit the growth of several CRC cell lines, including HT-29, HCT-116, and Caco-2, in a concentration-dependent manner. Notably, some studies have reported biphasic dose–response patterns. In these cases, the biological effects of quercetin vary across different concentration ranges, indicating context-dependent cellular responses [70,71]. Mechanistically, quercetin induces cancer cell cycle arrest, in part, by upregulating the CDK inhibitor p27. In addition, quercetin suppresses several key signaling pathways implicated in colorectal carcinogenesis, including Wnt, PI3K/Akt, and STAT3. Some evidence further suggests that these actions are mediated, at least in part, through activation of the cannabinoid receptor [72].

Ellagic acid, another major berry-derived phenolic compound, exhibits broad-spectrum anticancer activity, in diverse cancer cell lines, including those derived from CRC. Its biological activity is further enhanced by metabolites, particularly urolithins produced through gut microbial biotransformation. These microbiota-derived compounds contribute significantly to bioactivity of ellagic acid. Urolithins have been shown to induce cell cycle arrest at the S and G2/M phases. This effect is mediated, at least in part, by the downregulation of cyclin B1, leading to disruption of normal mitotic progression [73,74].

Additional berry-derived phytochemicals with documented anti-proliferative activity in CRC include apigenin. This flavonoid inhibits tumor cell growth primarily through suppression of the Wnt signaling pathway. It also downregulates key oncogenic regulators, including cyclin D1 and the proto-oncogene c-Myc [75]. Evodiamine, a quinazoline-carboline alkaloid isolated from Evodia rutaecarpa, has also demonstrated significant anti-tumor activity in colon cancer cells. It induces cell cycle arrest at the G2/M phase, thereby limiting cellular proliferation. In addition, evodiamine disrupts mitochondrial function and inhibits NF-κB signaling. These combined effects contribute to both its anti-proliferative and pro-apoptotic properties [33].

Altogether, these findings demonstrate that berry-derived bioactive compounds exert potent and mechanistically diverse anti-proliferative effects in CRC cells. These effects are mediated through coordinated modulation of cell cycle regulatory pathways, inhibition of oncogenic signaling networks, and activation of tumor-suppressive gene expression programs. The magnitude and efficacy of aforementioned biological effects are influenced by multiple factors. These include the chemical structure of the compounds, their bioavailability, the concentration administered, and the duration of exposure. In addition, potential synergistic interactions among co-existing phytochemical constituents may further enhance their biological activity.

PRO-APOPTOTIC EFFECTS OF BERRY-DERIVED COMPOUNDS IN CRC

Apoptosis, or programmed cell death, is a tightly regulated physiological process that is essential for maintaining tissue homeostasis. It functions to eliminate damaged or genetically compromised cells without triggering inflammatory responses [76,77]. DNA fragmentation is widely recognized as a key biochemical hallmark of apoptosis and is frequently used as a reliable indicator of apoptotic cell death [38,52]. Disruption of apoptotic signaling pathways contributes significantly to tumor progression and the development of resistance to cytotoxic chemotherapy. Consequently, the restoration of apoptotic competence in malignant cells represents a critical therapeutic strategy [78].

A pivotal determinant of apoptotic susceptibility in cancer cells is the balance between pro-apoptotic and anti-apoptotic members of the Bcl-2 protein family. In CRC, anti-apoptotic proteins, particularly Bcl-2, are often overexpressed, whereas pro-apoptotic proteins such as Bax are downregulated. This imbalance promotes cancer cell survival and facilitates tumor progression [79]. Emerging evidence indicates that bioactive compounds derived from berries can modulate this regulatory network in a way to restore apoptotic signaling in CRC cells.

Berry extracts induce apoptosis in a manner that is both cell type- and compound-dependent. For example, bilberry extract significantly induces DNA fragmentation in HT-29 cells in a concentration-dependent manner. In contrast, cloudberry exhibits comparatively weaker activity, while black currant, lingonberry, raspberry, and strawberry show minimal apoptotic effects under similar experimental conditions [38-40,47,48,52]. Such differential responses are mechanistically associated with increased expression of Bax and concomitant suppression of Bcl-2, consistent with activation of the mitochondrial apoptotic pathway.

Anthocyanins, the polyphenolic constituents of berries, modulate apoptosis through both intrinsic and extrinsic pathways. In the intrinsic (mitochondrial) pathway, anthocyanins disrupt mitochondrial membrane integrity, leading to the release of cytochrome c into the cytosol. This event triggers activation of initiator caspase-9, followed by downstream activation of executioner caspase-3. These processes are accompanied by transcriptional upregulation of pro-apoptotic proteins, including Bax and Bcl-2 homologous antagonist/killer (Bak), along with downregulation of the anti-apoptotic protein Bcl-2. In parallel, anthocyanins also activate the extrinsic (death receptor-mediated) pathway by enhancing the expression of Fas cell surface death receptor (Fas or CD95) and its ligand FasL. This interaction promotes receptor-mediated caspase activation, thereby contributing to apoptotic cell death [40].

Complementary in vitro studies further support the pro-apoptotic effects of berry-derived compounds across multiple CRC cell models. Extracts from strawberry, blueberry, blackberry, and raspberry significantly increased apoptosis in HT-29 cells, with approximately 1.7-1.8-fold elevation compared with untreated controls. In contrast, cranberry extract exhibited minimal apoptotic activity [56]. Fractionation analyses demonstrated that anthocyanin-enriched fractions possess greater apoptotic potency than other phenolic subclasses. These fractions induced marked DNA fragmentation in both HT-29 and Caco-2 cell lines [54]. Moreover, individual anthocyanidins, such as delphinidin and cyanidin, exerted direct cytotoxic effects in metastatic CRC cells by promoting apoptotic cell death [80].

Besides anthocyanins, additional berry-derived polyphenols also contribute to apoptosis induction through distinct molecular mechanisms. Resveratrol, found in blueberry and cranberry, induced apoptosis in HCT-116 cells via disruption of mitochondrial membrane potential and subsequent activation of caspase-3 and caspase-9 [81]. Ellagic acid, abundant in strawberry and raspberry, similarly triggered apoptotic signaling through the release of cytochrome c, activation of caspases, and downregulation of the anti-apoptotic protein B-cell lymphoma-extra large (Bcl-xL) [82]. Furthermore, its gut microbiota-derived metabolites, particularly urolithins, may enhance these apoptotic effects by sustaining activation of downstream signaling pathways.

Among flavonoid subclasses, quercetin exhibits pronounced pro-apoptotic activity in CRC. It induces apoptosis in HT-29 and SW480 human colon adenocarcinoma cell lines through multiple coordinated mechanisms, including downregulation of Bcl-2, activation of the tumor suppressor p53, and inhibition of NF-κB signaling. Altogether, these effects target both oncogenic survival pathways and pro-inflammatory signaling cascades [83,84]. Of substantial translational relevance, aronia (chokeberry) extract has been shown to restore apoptotic signaling in 5-fluorouracil-resistant CRC cells. This effect was mediated through the concurrent activation of mitochondrial and death receptor pathways, along with suppression of the pro-survival Akt and NF-κB signaling axes [85]. Similarly, phenolic-rich extracts from miracle berry upregulate the expression of key apoptotic effectors, including caspase-3 and caspase-9, at the transcriptional level, thereby confirming activation of the intrinsic apoptotic pathway [53].

Interestingly, berry-derived compounds may also enhance the cytotoxic efficacy of conventional chemotherapeutic agents. For example, miracle berry phenolics sensitize drug-resistant CRC cell lines, such as DLD-1 and SW620, to oxaliplatin by amplifying apoptotic signaling. This combinatorial effect leads to a significant reduction in the viability of resistant tumor cells [53]. Collectively, these findings highlight the potential adjuvant role of berry-derived compounds in overcoming chemoresistance in CRC treatment.

Translational relevance also extends to dietary intervention models. For example, consumption of black raspberry powder has been associated with epigenetic reprogramming in colorectal tissue. These changes include alterations in promoter methylation at tumor suppressor gene loci. Such epigenetic modifications are linked to enhanced apoptotic activity and reduced proliferative signaling [86]. In addition, gut microbiota-mediated biotransformation of berry polyphenols introduces another biologically significant dimension to their chemopreventive effects. This process contributes, in part, to the regulation of downstream apoptotic pathways [35]. Consistent with this mechanism, non-extractable polyphenolic fractions from strawberry have been shown to induce apoptosis in colon cancer cells. These fractions also promote G2/M phase cell cycle arrest, thereby exerting dual inhibitory effects on tumor cell proliferation [34].

Taken together, these findings demonstrate that berry-derived bioactive compounds exert potent and mechanistically diverse pro-apoptotic effects in CRC. These effects involve multiple interconnected processes. Key mechanisms include disruption of mitochondrial membrane integrity, activation of caspase-dependent apoptotic cascades, modulation of Bcl-2 family protein expression, and suppression of oncogenic survival signaling pathways. The magnitude and efficacy of these effects are influenced by several factors, including phytochemical composition, bioavailability, exposure concentration, and cellular context. These observations support the importance of both individual bioactive constituents and their potential synergistic interactions in mediating anticancer activity.

ANTI-INFLAMMATORY EFFECTS OF BERRY-DERIVED COMPOUNDS IN CRC

Chronic inflammation is a well-established and mechanistically central driver of colorectal carcinogenesis. It contributes to tumor initiation, promotion, and progression. This occurs via the sustained activation of pro-inflammatory signaling pathways within the tumor microenvironment. Emerging evidence indicates that berry consumption can attenuate inflammatory processes. This effect is mediated through regulation of cytokine production and modulation of immune signaling pathways associated with reduced tumor cell proliferation and angiogenesis [87]. Alterations in circulating cytokines, including granulocyte–macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-8, have been shown to correlate with tissue-level biomarkers of apoptosis and proliferation. Such observations suggest that berry-derived compounds exert immunomodulatory effects which may contribute to their chemopreventive and anticarcinogenic potential [32,33,88].

Microbially driven inflammation represents an additional and clinically relevant component of CRC pathogenesis. Certain bacterial species, such as H. pylori, have been implicated in inflammation-associated carcinogenic processes [89]. Extracts derived from various berry species, including raspberry, strawberry, bilberry, cranberry, elderberry, and blueberry, exhibit notable antimicrobial activity, such as inhibition of the growth of H. pylori [90,91]. These findings suggest that berry-derived compounds may contribute to CRC prevention through complementary mechanisms. They suppress pro-inflammatory signaling pathways and modulate pathogenic microbiota associated with tumorigenesis.

At the molecular level, inflammatory mediators derived from arachidonic acid metabolism play a central role in colorectal carcinogenesis. They are strongly implicated in the pathogenesis of both inflammatory bowel disease (IBD) and CRC. Among them, prostanoids are key effectors in the inflammatory cascade [92,93]. Gut microbiota–derived phenolic metabolites can modulate prostanoid biosynthesis, particularly in response to pro-inflammatory stimuli such as IL-1β. Among these metabolites, p-coumaric acid has been shown to significantly inhibit prostanoid production. In contrast, metabolites derived from ferulic acid exhibit variable and context-dependent inhibitory effects [94]. The anti-inflammatory activity of these compounds appears to depend on their phenolic origin. Metabolites derived from bound phenolic compounds generally suppress inflammatory responses, whereas those originating from free phenolic acids may, in some contexts, exert pro-inflammatory effects. These observations highlight the critical role of interindividual variability in gut microbiota composition in shaping biological responses to dietary polyphenols [95].

COX-2 is a rate-limiting enzyme in prostaglandin biosynthesis and a key molecular target in inflammation-associated colorectal carcinogenesis. American elderberry extract has been shown to markedly reduce COX-2 enzymatic activity in vitro. In parallel, anthocyanin-rich chokeberry extract suppresses COX-2 gene expression in vivo. This suppression is accompanied by a significant reduction in aberrant crypt foci formation in chemically induced models of colon carcinogenesis [96,97].

Among flavonoids, apigenin inhibits the activation of NF-κB and STAT3. This inhibition leads to decreased expression of pro-inflammatory cytokines and chemokines in experimental models of IBD and colitis-associated cancer [98,99]. Similarly, anthocyanin-rich bilberry extracts attenuate tumor-associated inflammation. These effects are attributable to the downregulation of proto-oncogenic signaling pathways, including those mediated by the proto-oncogene Src and EGFR, as well as modulation of immune checkpoint-related proteins such as programmed cell death protein 1 (PD-1) [23].

Additional berry-derived constituents further contribute to the suppression of inflammatory signaling through diverse molecular mechanisms. Non-extractable polyphenolic fractions from strawberry have been shown to reduce the expression of pro-inflammatory mediators, including inducible iNOS and c-Fos. Concurrently, these fractions enhance cytoprotective antioxidant defenses, particularly through upregulation of heme oxygenase-1 (HO-1) [34].

Bioactive alkaloids such as evodiamine also exhibit potent anti-inflammatory effects. These compounds suppress a broad range of pro-inflammatory cytokines, including IL-1β, IL-6, IL-17, and TNF-α. This activity is mediated, at least in part, through inhibition of upstream regulatory components of the NF-κB signaling pathway [33].

Anthocyanins play a central role in mediating anti-inflammatory effects relevant to CRC. These compounds suppress key inflammatory signaling cascades by inhibiting NF-κB activation. As a result, they reduce the expression of pro-inflammatory cytokines, such as TNF-α and IL-6, as well as inflammatory enzymes including COX-2 and inducible nitric oxide synthase (iNOS). In addition, anthocyanins enhance cellular antioxidant capacity through activation of Nrf2. This activation alleviates oxidative stress, which is a key driver of chronic inflammation and tumorigenic transformation [40,85].

Evidence from in vivo and dietary intervention studies further supports these mechanisms. Berry-enriched diets and polyphenol supplementation have been shown to attenuate chronic mucosal inflammation in experimental models. The effects are associated with reduced tumor initiation and progression [32,33]. Moreover, diets rich in anthocyanins are linked to suppression of NF-κB signaling, decreased COX-2 expression, and a reduction in oxidative stress burden in CRC models [17].

Taken together, these findings demonstrate that berry-derived bioactive compounds exert potent and mechanistically diverse anti-inflammatory effects in the context of CRC. The effects involve multiple complementary actions: inhibition of pro-inflammatory enzymes and cytokine production, as well as suppression of oncogenic signaling pathways such as NF-κB and STAT3.

METABOLISM AND BIOAVAILABILITY OF BERRY-DERIVED COMPOUNDS

The biological efficacy of dietary bioactive compounds is fundamentally determined by their bioavailability. This concept encompasses absorption, distribution, metabolism, and the ability to reach biologically relevant concentrations at target tissues. Although berry-derived polyphenols exhibit well-documented anticancer properties, their bioavailability is relatively limited. This limitation raises important questions regarding the extent to which intact parent compounds directly contribute to chemopreventive effects [62,100]. Accumulating evidence suggests that gut microbiota–derived metabolites may represent the principal bioactive species responsible for these effects, rather than the native compounds themselves. This paradigm appears to be particularly relevant within the colonic microenvironment [36].

Following ingestion, anthocyanins and other polyphenols undergo extensive biotransformation throughout the gastrointestinal tract. For instance, cyanidin-3-rutinoside is converted to cyanidin-3-glucoside and subsequently degraded to protocatechuic acid. These transformations are mediated by colonic microbial enzymes, including β-glucosidases, β-glucuronidases, and α-rhamnosidases [101]. Similar metabolic pathways have been demonstrated in animal models, confirming that anthocyanins are extensively catabolized during gastrointestinal transit. Importantly, the resulting metabolites, particularly protocatechuic acid, retain and in some cases exceed, the antioxidant and chemopreventive activities of their parent compounds. These findings indicate that metabolic transformation may enhance, rather than diminish, the biological potency of berry-derived polyphenols [102,103].

Ellagitannins undergo extensive microbial catabolism in the colon, leading to the production of bioactive metabolites collectively known as urolithins. Among these, urolithin A has been identified as a particularly prominent metabolite with well-documented anti-inflammatory and anticancer activities [104]. Human pharmacokinetic studies provide important insights into their biotransformation. Urolithins are consistently detected in urine following consumption of ellagitannin-rich berries, indicating their absorption from the intestine into the body after microbial conversion. In contrast, their absence in ileostomy effluent confirms that urolithin biosynthesis occurs exclusively within the colonic microbiota [105,106]. Together, these findings highlight the essential role of the gut microbiome in mediating the downstream biological effects of ellagitannin-rich foods.

The intestinal absorption and transepithelial transport of anthocyanins are strongly influenced by their chemical structure. Glucoside conjugates are generally absorbed more efficiently than their galactoside or arabinoside counterparts. Additionally, decreased hydroxylation and increased methoxylation of the aglycone moiety enhance membrane permeability [107,108]. Among individual anthocyanidins, peonidin exhibits relatively higher transport efficiency across intestinal epithelial monolayers. Despite the limited bioavailability of intact anthocyanins, their local accumulation within the gastrointestinal tract appears to be more relevant to CRC prevention. Experimental studies have demonstrated that substantial concentrations of phenolic acid metabolites, including protocatechuic, ferulic, and caffeic acids, are present throughout the intestinal lumen and in fecal samples [103,109]. These locally generated metabolites may exert direct cytoprotective effects on colonic epithelial cells through antioxidant, anti-inflammatory, and anti-proliferative mechanisms.

Berry-derived polyphenols exert bidirectional interactions with the gut microbiota, leading to compositional and functional alterations that enhance their chemopreventive potential. Dietary intake of anthocyanin-rich foods has been consistently associated with the selective enrichment of beneficial bacterial genera, including Bifidobacterium, Lactobacillus, and Akkermansia, alongside a reduction in potentially pathogenic microbes such as Bilophila [9]. These microbial shifts are accompanied by significant changes in metabolic activity, particularly in the production of short-chain fatty acids and the regulation of microbial energy metabolism pathways. In parallel, polyphenols can modulate host cellular metabolism by influencing key bioenergetic processes, including glycolysis and the tricarboxylic acid or Krebs cycle. Such metabolic reprogramming contributes to the suppression of tumor cell bioenergetics and may inhibit cancer progression [110,111].

Quercetin serves as a representative example of the dynamic interplay between polyphenol metabolism and microbiome modulation. In addition to its well-documented direct anticancer effects, quercetin alters gut microbial composition by promoting the expansion of beneficial bacterial populations while suppressing inflammation-associated pathogens, particularly members of the Proteobacteria phylum. These microbiota-mediated changes are associated with improved intestinal barrier function and reduced colonic inflammation, both of which are critical factors in CRC risk and progression [112,113].

Evidence from human pharmacokinetic and ileostomy studies provides valuable insights into the in vivo metabolism of berry polyphenols. Anthocyanidin aglycones, including delphinidin, cyanidin, petunidin, and malvidin, have been detected in ileal fluid, indicating partial absorption in the small intestine. In contrast, urolithins are consistently identified in urine following berry consumption. This provides strong evidence of colonic microbial biotransformation and subsequent absorption into the body [94,106].

Taken together, these studies suggest that the chemopreventive effects of berry-derived polyphenols are largely mediated by their bioactive metabolites rather than the intact parent compounds. The gut microbiota plays a central and bidirectional role in this process. It biotransforms dietary polyphenols into structurally diverse metabolites with enhanced biological activity. Notably, polyphenol exposure modulates the composition and function of the microbial community. Moreover, this reciprocal interaction exerts a functionally prebiotic effect, promoting a gut microbial environment that supports anti-inflammatory, anti-proliferative, and pro-apoptotic signaling within the colorectal mucosa. The interplay among polyphenol chemical structure, gut microbial ecology, and host physiological responses therefore represents a key determinant of overall biological efficacy.

These observations highlight the importance of considering both parent compounds and their metabolites in future studies. This is particularly relevant for preclinical models, pharmacokinetic analyses, and clinical investigations aimed at elucidating the mechanisms underlying polyphenol-mediated chemoprevention.

CONCLUSION

Berry-derived bioactive compounds emerge as promising multi-target chemopreventive agents in CRC, acting on epithelial, immune, and microbial compartments of the colorectum. They inhibit dysregulated proliferation, restore apoptotic competence, attenuate chronic inflammation, and interact with the gut microbiota to strengthen the anti-tumor defenses.

Anthocyanins, ellagitannins, ellagic acid, quercetin, resveratrol, and related polyphenols exert anti-proliferative effects by modulating cell cycle progression and oncogenic signaling molecules such as Wnt/β-catenin, PI3K/Akt, NF-κB, ERK/MAPK, and STAT3. They induce G0/G1, S, or G2/M arrest through downregulation of cyclins and CDKs and upregulation of p21 and p27, often with selectivity for malignant cells. In parallel, these compounds activate intrinsic and extrinsic apoptotic cascades via mitochondrial disruption, cytochrome c release, caspase-3/9 activation, and rebalancing of Bcl-2 family proteins, frequently coupled to p53 activation and suppression of Akt and NF-κB as shown in Figure 1.

Figure 1. Mechanistic pathways underlying the chemopreventive effects of berry-derived bioactive compounds in colorectal cancer.

Four principal pathways are illustrated: (1) antiproliferative effects mediated through cell cycle arrest at G0/G1 and S phases via upregulation of p21, p27, down regulation of cyclin D1, CDK4, and oncogenic signaling axes including Wnt/β-catenin, PI3K/Akt, and MAPK; (2) pro-apoptotic effects through convergent activation of intrinsic (Bax/Bak↑, Bcl-2↓, cytochrome c release, and caspase-9/3 activation) and extrinsic (Fas/FasL↑) pathways; (3) anti-inflammatory effects through suppression of NF-κB, STAT3, COX-2, iNOS, and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) alongside Nrf2 antioxidant activation; and (4) gut microbiota modulation through colonic biotransformation of polyphenols into bioactive metabolites (urolithins, and protocatechuic acid) and selective enrichment of cytoprotective microbes (Bifidobacterium, Lactobacillus, and Akkermansia) with concurrent suppression of oncogenic pathobionts. Convergent activation of these pathways collectively suppresses colorectal carcinogenesis and supports the adjunctive therapeutic potential of berry-derived compounds in colorectal cancer prevention and management. CDK4, cyclin-dependent kinase 4; PI3K/Akt, phosphoinositide 3-kinase/protein kinase B; MAPK, mitogen-activated protein kinase; Bax, Bcl-2-associated X protein; Bcl-2, B-cell lymphoma 2; iNOS, inducible nitric oxide synthase; IL-6, interleukin-6; IL-1β, interleukin-1 beta; IL-17, interleukin-17; Nrf2, nuclear factor erythroid 2-related factor 2; HO-1, heme oxygenase-1; ↑, upregulation or activation; ↓, downregulation or inhibition.

Berry polyphenols additionally downregulate COX-2, iNOS, and key cytokines, including TNF-α while inhibiting activation of NF-κB/STAT3 while activating Nrf2-driven antioxidant responses. They are extensively metabolized by the gut microbiota into potent metabolites such as protocatechuic acid and urolithins. Taken together, these characteristics provide a strong mechanistic rationale for the continued investigation and therapeutic development of berry-derived compounds as chemopreventive agents against CRC. However, much of the current evidence derives from preclinical models using supraphysiological doses, and human trials remain limited and heterogeneous as shown in Figure 1.

Future research should prioritize the use of well-characterized and standardized berry preparations. These interventions should be evaluated using integrated pharmacokinetic, microbiome, and molecular endpoints to link exposure with mechanistic and clinical outcomes. In parallel, precision nutrition approaches are needed that explicitly consider interindividual differences in microbiota-dependent metabotypes, in order to translate these mechanistic insights into effective CRC chemopreventive strategies.