Doxorubicin (DOX), a member of the anthracycline family, is a common antineoplastic drug used to treat a variety of cancers. DOX affects cancer cells by a variety of methods, including DNA intercalation, disruption of DNA repair, production of free radicals, and their damaging effects on cellular membranes, DNA, and proteins (Vatsyayan et al., 2009). On the other hand, this effect can harm normal cells in the same manner as it damages cancer cells. The production of reactive oxygen species (ROS) is the main mechanism by which DOX induces cardiotoxicity. These ROS cause oxidative stress, inflammation, and cell death in the heart (Bruynzeel et al., 2007; Saeed et al., 2015; El-Agamy et al., 2016; Abdel-Daim et al., 2017; Shahidullah et al., 2017; Abu Gazia and El-Magd, 2018). DOX metabolism in the mitochondria results in the release of cytochrome-C, which starts apoptosis along with a disruption in the transport of mitochondrial calcium, which can induce the death of cardiomyocytes (Catanzaro et al., 2019). Thus, this drug’s clinical use was constrained by cumulative dose-dependent cardiotoxicity (Othman et al., 2021). Despite its efficacy in cancer therapy, the severe cardiac side effects limit the clinical use of DOX and necessitate the development of strategies to mitigate its toxic effects on the heart (Qiu et al., 2023).

According to recent research, there may be some benefits to using natural antioxidants in addition to chemotherapy and other chemical therapeutic agents to decrease oxidative stress damage induced by these synthetic drugs (Elmetwalli et al., 2023; Abass et al., 2024; Awad et al., 2024; Tawfic et al., 2024). Natural antioxidants have gained attention for their potential to protect against DOX-induced cardiotoxicity. Cardiovascular function can be improved with a change in lifestyle and regular consumption of healthy foods, including fruits, vegetables, and plants high in antioxidants (Topliss et al., 2002). Flavonoids like hesperidin, naringin and alkaloids like synephrine are the primary biologically active components of citrus herbs and have positive medical effects on human health (Anbazhagan et al., 2007). Citrus species exhibit antioxidant, anti-inflammatory, anti-cancer, anti-lipidemic, and antibacterial properties due to the presence of flavonoid molecules (Ekinci Akdemir et al., 2016). Researchers discovered that citrus fruit could have protective benefits for the upper respiratory tract and gastrointestinal cancer (Cirmi et al., 2018). Lemon and orange peels, rich in flavonoids and polyphenols, have shown promising effects in reducing oxidative stress and inflammation in various experimental models (González-Molina et al., 2010; Guimarães et al., 2010). Numerous useful components, particularly limonin in orange peel and pomelo peel, have been increasingly isolated and separated with the development of comprehensive citrus use (Deng et al., 2021). In addition, lemon peels contain many flavonoids that have potential health benefits (Zhang et al., 2019). Lemons are also excellent at reducing the negative effects of cancer due to their ingredients, which have strong antioxidant, antiviral, and immunostimulant properties (Tag et al., 2014).

The olive tree has been widely regarded as one species with the highest antioxidant activity through its oil, fruits, and leaves. Antioxidant compounds found in the olive tree include oleuropein, oleuropein aglycone, tyrosol, and hydroxytyrosol (Jemai et al., 2008). Olive oil, with its high content of oleic acid and polyphenols, has antioxidant, antibacterial, and anti-inflammatory properties (Millman et al., 2021) and is known to exert protective effects on the cardiovascular system (Covas et al., 2009). The risk of cardiovascular disease can be decreased by up to 10% by taking olive oil at a dose of 10 g/day (Guasch-Ferré et al., 2014). According to a clinical investigation, olive oil consumption between 10 and 50 mL per day could considerably lower blood pressure (Zamora-Zamora et al., 2018). In addition, a preclinical investigation found that a single dose of olive oil had a cardioprotective impact against cardiac remodeling and blood pressure elevation (Kamisah et al., 2015).

Based on the previously mentioned information, citrus is an economically important fruit, but the peels generated by the juice industry are a major source of agricultural waste. Their fermentation causes many economic and environmental problems, so it is worthwhile to investigate ways to use this citrus waste. Olive oil is a valuable source of antioxidants and healthy fats, and its consumption has been linked to a number of health benefits, including reduced risk of heart disease. Despite the established benefits of these natural products, their specific cardioprotective effects against DOX-induced cardiotoxicity remain underexplored. Most studies have focused on individual components rather than whole extracts, and comparative studies evaluating the effectiveness of different natural sources are limited. Therefore, this study aimed to investigate the cardioprotective potential of lemon, orange peels, and olive oil against DOX-induced myocardial damage in rats. We hypothesize that these natural products can mitigate the oxidative stress, apoptosis, and inflammation associated with DOX cardiotoxicity, providing a comparative analysis of their protective effects. The findings of this study could provide a basis for developing novel dietary strategies or adjunct therapies to reduce the cardiotoxic effects of DOX in cancer patients.

DOX, an anticancer drug, has been reported to increase oxidative stress, which can affect different organs, including the heart. Here, we investigated the toxic effects of DOX on heart function and structure in rats and evaluated the potential protective effects of lemon and orange peels and olive oil. We found that lemon and orange peels and olive oil can significantly mitigate DOX-induced cardiotoxicity in rats as revealed by reduced cardiac biomarkers (AST, LDH, CK, cTnT), oxidative stress markers (NO, MDA), apoptotic markers (Bax and caspase 3), and inflammatory cytokines NFκB, TNFα, IL1β while enhancing antioxidant enzyme activities (SOD, CAT, GPx) compared to the DOX group.

The present results indicate that the DOX group showed a significant decrease in FI compared to other groups, consistent with previous research (Arafa et al., 2014). The olive oil group had FI values closest to the control group. DOX treatment resulted in a significant decrease in BWG, while rats fed with orange or lemon peels showed a significant increase in BWG. The use of DOX simultaneously with the orange peel extract maintained the body weight of the nude mice, which illustrates the protective effects of the orange peel extract (Tajaldini et al., 2020). DOX also caused a significant reduction in FER, aligning with Ghibu et al. (2012), who reported that cumulative DOX doses led to reduced body weight and food consumption due to induced anorexia. Moreover, we observed that DOX significantly elevated serum levels of cardiac damage markers (LDH, AST, CK, and cTnT) compared to the control group, consistent with findings of other studies (Abu Gazia and El-Magd, 2018; Xing et al., 2022). This increase is attributed to the oxidative stress and free radical release caused by DOX, which compromise cardiac cell membranes, leading to enzyme leakage into the bloodstream. Conversely, these markers were significantly reduced in all treatment groups, with the most notable improvement observed in the olive oil group. Similarly, Hammad et al. (2018) reported that active components in orange peels decreased serum AST, cTnT, and LDH levels, while Abdelhaliem and Sheha (2018) demonstrated similar effects with lemon peel. Generally, a drop in these biomarker levels indicates that the treatments have improved heart health.

Our results revealed potent DOX cardiotoxic effects in rats as evidenced by increased levels of oxidative stress (high levels of NO and MDA and low activity of SOD, CAT, and GPx). When cytochrome P450 reductase and NADH dehydrogenase convert DOX’s quinine moiety to its corresponding semiquinone form, it can trigger ROS production (Kalishina et al., 2003). The DOX semiquinone form is converted to quinine by molecular oxygen oxidation, which in turn produces superoxide radicals. Consistent with our results, Abu Gazia and El-Magd (2018), Ayaz et al. (2004), and El-Agamy et al. (2016) have also demonstrated that DOX treatment causes a substantial rise in cardiac MDA levels. Elevated MDA causes lipid peroxidation, which in turn destroys the cell membranes of cardiomyocytes and releases LDH, CK, and cTnT into the bloodstream because phospholipids are the primary components of cell membranes. By activating endogenous antioxidant enzymes, the body counteracts excessive ROS. However, DOX also targeted this defense mechanism, and a decline in these enzymes suggests that cardiomyocytes suffer oxidative damage because cells can’t remove free radicals (Tokarska-Schlattner et al., 2006). In agreement with our findings, after DOX induction, NO production was significantly increased (Pinto et al., 2007). In contrast, antioxidant enzyme activities were increased in response to the administration of olive oil, lemon, and orange peels, while NO and MDA levels were decreased. This effect can be attributed to the presence of potent antioxidant compounds in olive oil, such as oleuropein and hydroxytyrosol (Utarı et al., 2022), and in citrus peels, such as quercetin, hesperidin, L-carnitine, and silybin (Aziz, 2021; Abd El-Motelp, 2022). Olive oil demonstrates a cardioprotective effect against DOX-induced cardiotoxicity (Almalki et al., 2020), primarily due to its rich content of antioxidant compounds, such as oleuropein and hydroxytyrosol (Rus et al., 2017). Rather than diminishing DOX’s anticancer efficacy, the antioxidants in olive oil have been found to enhance its therapeutic effects, making it a potential synergistic adjunct in chemotherapy (El-Kammar and Ghazy, 2018). Oleic acid has been shown to increase plasma HDL levels while reducing LDL levels (Jimenez-Lopez et al., 2020). Our findings suggest that with their higher L-carnitine content, lemon peels exhibited more pronounced benefits than orange peels. Hesperidin, concentrated in the white pith of citrus fruits, acts as an antioxidant and anti-inflammatory agent and has been associated with reduced risks of heart disease and cancer (Khamis et al., 2018; Selim et al., 2019; Badawy et al., 2021; Sajadi et al., 2021). Therefore, whole citrus peels were used in this study to maximize these beneficial effects. Citrus peels and seeds are abundant in phenolic compounds, with the peels containing higher levels of flavonoids than the seeds (Sawalha et al., 2009). Numerous phytochemicals in orange peel extract are recognized for their antioxidant properties and ability to protect against oxidative stress (Bae and Kim, 2016). These natural antioxidants have protective properties against DOX-induced cardiac damage (Hammad et al., 2018; Patel et al., 2018).

Analyses using light and electron microscopy showed that DOX severely damaged the myocardium by compromising its structural integrity. In the group that received DOX, light microscopy revealed cardiomyocytes that were wavy, irregular, and widely separated; there was also focal necrosis with areas of hyalinization, tissue fibrosis, inflammatory cell infiltration, and clogged blood vessels. This finding aligns with prior research (Abu Gazia and El-Magd, 2018; Qin et al., 2022; Utarı et al., 2022). According to our results and those of Safdar et al. (2017) and Babaei et al. (2020), TEM imaging further supported these findings, showing broken cristae, enlarged mitochondria, and irregularly shaped nuclei in disturbed cardiomyocytes. Because they produce most of the superoxide that the heart cells release when exposed to DOX, the mitochondria in myocardial cells are the first organelles to suffer oxidative damage, which in turn causes mitochondrial malfunction and cell death (Utarı et al., 2022). Our results of the molecular study showed that the cardiac tissue underwent mitochondrial-dependent apoptosis, as shown by the upregulation of Bax and caspase three and the downregulation of Bcl2. Rats treated with orange peel exhibited mild myocardial alterations, such as abnormal mitochondria and loss of striation. In contrast, those treated with lemon peel showed minimal alterations, effectively preventing DOX-induced cardiac injury. Treatment with olive oil provided the greatest cardioprotection, as evidenced by only minor histopathological changes, and lowest expression of Bax and caspase three genes, and highest expression of the Bcl2 gene. This protective effect is attributed to the high oleuropein content in olives and olive oil (Hamza et al., 2021). Studies have shown that oleuropein significantly reduces structural changes in cardiomyocytes, supporting its role as a potent antioxidant that mitigates DOX toxicity by decreasing iNOS, Bax expression, and NO production (Andreadou et al., 2007).

The protective mechanisms of these natural products against DOX-induced cardiotoxicity also include the suppression of inflammatory pathways (lower levels of NFκB, TNFα, and IL1β). This aligns with previous studies suggesting that antioxidants can counteract DOX-induced free radical formation, apoptosis, and inflammation in cardiac tissue (Andreadou et al., 2007; Guimarães et al., 2010; Abu and El-Magd, 2018; Hamza et al., 2021). The observed cardioprotective effects can be attributed to the high content of bioactive compounds in these natural sources, including flavonoids, polyphenols, and oleic acid, known for their antioxidant and anti-inflammatory properties (Covas et al., 2009; González-Molina et al., 2010; Almalki et al., 2020). The histopathological examination corroborated these biochemical findings, showing that lemon and orange peels and olive oil preserved myocardial architecture, reduced inflammatory cell infiltration, and minimized mitochondrial damage and myofibril lysis. Among the treatments, olive oil exhibited the most pronounced protective effects, possibly due to its rich composition of phenolic compounds and unsaturated fatty acids, which have been shown to modulate oxidative stress and inflammation more effectively than other natural sources (Covas et al., 2009). Thus, it would be recommended to add olive oil to salads and vegetables and eat whole citrus fruit with its peel to improve heart health.

Oxidative stress induced by DOX could activate NFκB, which subsequently regulates TNFα, IL1β and pro-apoptotic genes Bax and caspase 3 (Gloire et al., 2006; Tan et al., 2010). Similarly, the inhibition of PI3K/AKT signaling may suppress anti-apoptotic proteins such as Bcl2 (Franke et al., 2003). The observed reduction in Bax and caspase three and the elevation of Bcl2 levels following treatment with citrus peels and olive oil suggest a potential modulation of these pathways. Notably, the high antioxidant and anti-inflammatory properties of these treatments could mediate upstream effects by reducing ROS production and suppressing NF-κB activation.

Several limitations should be considered when interpreting these results. First, the study was conducted on a small sample size of rats, which may limit the generalizability of the findings. Second, the study did not investigate the long-term effects of these natural products beyond the 28-day experimental period. Third, the exact molecular mechanisms underlying the cardioprotective effects were not explored in depth. Fourth, our study did not explore whether these natural treatments interfere with DOX’s anticancer effects. Fifth, this study also lacks comprehensive dose-response studies that could further elucidate the therapeutic potential of lemon and orange peels and olive oil and their mechanisms of action. Future research should include a larger sample size, extended observation periods, and molecular studies to better understand the pathways involved in the protective effects of these natural products. Future studies could also investigate whether these cardioprotective treatments reduce DOX’s efficacy against tumors, balancing cardioprotection with cancer treatment.

This study highlights the potential of lemon and orange peels and olive oil in protecting against DOX-induced cardiotoxicity by reducing oxidative stress, apoptosis, and inflammation in cardiac tissue. Among the tested treatments, olive oil showed the most significant cardioprotective effects. These findings suggest that incorporating these natural products into the diet could be a beneficial strategy for mitigating the cardiotoxic effects of DOX in cancer patients. Further research is warranted to explore their potential use as complementary therapies in clinical settings.