We now explore LDH inhibitors in more depth, classifying them based on their chemical structures and modes of action into two categories: small-molecule inhibitors and RNA-based inhibitors.

Various natural compounds can inhibit LDH activity through different mechanisms. The most common approach involves direct binding to the enzyme’s active site, leading to the inhibition of pyruvate conversion to lactate (Conners et al., 2005). Polyphenols, such as quercetin and epigallocatechin gallate (EGCG), can bind to the active site of LDH, reducing its activity levels (Gradišar et al., 2007). Additionally, some natural compounds modulate other components involved with LDH, including lactate transporters or mitochondrial enzymes. For instance, rosmarinic acid affects the lactate transporters of cancer cells (Marin-Hernandez et al., 2009; Cerella et al., 2013; Ma et al., 2018).

Another mechanism underlying inhibition of LDH by natural compounds is the regulation of LDH gene expression. Various compounds, such as curcumin, resveratrol, and quercetin, can inhibit LDH expression by reducing LDH gene transcription or promoting LDH protein degradation (Yang et al., 2018; Reyes-Farias and Carrasco-Pozo, 2019; Soni et al., 2020). In contrast to small-molecule inhibitors, RNA-based inhibitors target LDH expression by interfering with its mRNA. As discussed earlier, RNAi and ASOs are commonly used for inhibiting LDH expression, which is achieved at the mRNA level (Wood et al., 2019; Bockstahler et al., 2022).

Several studies have demonstrated the potential therapeutic effects of LDH inhibitors in diseases associated with abnormal LDH activity (Granchi et al., 2010; Valvona et al., 2016). For instance, preclinical studies have shown that LDH inhibitors can suppress tumor growth both as a monotreatment and in combination with other cancer therapies, such as chemotherapy and radiation therapy (Capula et al., 2019; Qiao et al., 2021). LDH inhibitors have also been investigated as potential therapeutics in cardiovascular diseases (Ji et al., 2021), as well as for their effects on Alzheimer’s disease and Parkinson’s disease (Newington et al., 2013; Acharya et al., 2019).

Flavonoids, a group of polyphenols abundant in fruit, vegetables, and medicinal plants, function as LDH inhibitors (Huang et al., 2009). Studies have shown that the flavonoids curcumin and quercetin inhibit LDH activity and reduce lactate synthesis in cancer cells (Maurya and Vinayak, 2015; Unlu et al., 2016; Reyes-Farias and Carrasco-Pozo, 2019). Curcumin treatment reduces LDHA expression in human colorectal cancer cells, leading to decreased lactate production and cellular proliferation (Wang et al., 2015b). Quercetin, found in several foods, including apples and onions (Kopustinskiene et al., 2020), reduces LDHA activity and triggers apoptosis in cancer cells, effectively inhibiting cellular glycolysis by reducing LDHA expression, thereby suppressing lactic acid generation and glucose uptake (Jia et al., 2018). Kaempferol, found in tea and various fruit, downregulates LDHA expression in human breast cancer cells through inhibition of STAT3 activity (Narayan and Kumar, 2014). Galloflavin binds to the NADH-binding site in LDHA, inhibiting its ability to bind to single-stranded DNA and suppressing colorectal cancer growth (Fiume et al., 2013). Moreover, galloflavin has been shown to completely inhibit both LDHA and LDHB (Manerba et al., 2012). EGCG, the primary flavanol in green tea, inhibits LDHA and exhibits anti-cancer activity in pancreatic cancer cells, and it significantly slows the growth of breast cancer cells, triggering apoptosis through its action as an LDHA inhibitor (Wang et al., 2015a; Gao and Chen, 2015). Combining catechin, epicatechin, and gallocatechin with epigallocatechin enhanced the inhibitory effect on LDHA (Cheng et al., 2020). Apigenin reduces LDHA mRNA expression in HepG2 cells, a human hepatocellular carcinoma cell line (Korga et al., 2019). Although the precise mechanism underlying inhibition of LDH by flavonoids is not fully understood, it may involve direct enzyme binding, gene expression modulation, or protein stability regulation (Bader et al., 2015; Yao et al., 2022). Luteolin acts as an LDH inhibitor and has been found to bind effectively to the active pocket residues of LDH (Li et al., 2021b). Additionally, luteolin 7-O-β-d-glucoside, found in Phlomis kurdica, non-specifically inhibits both LDH-1 and LDH-5 (Bader et al., 2015).

Flavonoids have been shown to exert beneficial effects on cardiovascular health, preventing atherosclerosis, hypertension, and myocardial infarction (Stangl et al., 2006). Quercetin treatment was found to significantly decrease infarct size and improve cardiac function in rats with myocardial infarction (Zaafan et al., 2013), with quercetin’s capacity to lower oxidative stress, inflammation, and apoptosis in the heart considered possible causes of its cardioprotective effects.

Hesperidin, found in citrus fruits, exhibits anti-hypertensive and anti-atherosclerotic properties (Mahmoud et al., 2019). It has been shown to lower blood pressure and enhance endothelial function in hypertensive rats (Morand et al., 2011), and it prevents atherosclerotic plaque formation in apolipoprotein E–knockout mice (Sugasawa et al., 2019). Catechin in tea and resveratrol in red wine also improve cardiovascular health (Gross, 2004), with the former regulating lipid metabolism and the latter reducing inflammation, oxidative stress, and platelet aggregation (Chen et al., 2016). These mechanisms contribute to improved cardiovascular disease outcomes (Gresele et al., 2011).

Flavonoids have been extensively studied for their potential in treating neurodegenerative diseases owing to their anti-inflammatory, anti-oxidant, and neuroprotective properties (Spagnuolo et al., 2018). In animal models of neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease, flavonoids prevent neurodegeneration and cognitive decline (Solanki et al., 2015) by inhibiting oxidative stress, inflammation, and protein misfolding, and modulating the signaling pathways involved in cell survival, synaptic plasticity, and neurogenesis (Khan et al., 2020; Numakawa and Odaka, 2021). Some flavonoids may also protect against metabolic dysregulation in neurodegenerative processes by inhibiting LDHA activity in the brain (Zhang et al., 2015a). Additionally, flavonoids have been reported to alleviate brain damage caused by ischemia and reperfusion through LDH inhibition and anti-oxidant effects (Dong et al., 2013). The flavonoid oroxylin A reduces LDH expression (Sajeev et al., 2022) and shows potential for preventing and treating neurological diseases (Lu et al., 2016).

Alkaloids, nitrogen-containing compounds widely distributed in the plant kingdom (Roy, 2017), have been recognized for their potential in LDH inhibition and drug discovery (Khazir et al., 2013). Berberine, an isoquinoline alkaloid found in plants, including goldenseal and barberry, possesses anti-bacterial and anti-inflammatory properties, making it a valuable component in Chinese medicine (Imanshahidi and Hosseinzadeh, 2008). Berberine is known to exhibit anti-cancer activity through inhibition of LDHA activity and reduction of lactate production in cancer cells (Tan et al., 2015). In mouse models of breast, colon, and lung cancer, berberine has demonstrated significant anti-cancer effects, inhibiting tumor growth and reducing lactate production (Sun et al., 2009; Mao et al., 2018). Moreover, berberine has shown the ability to suppress LDHA activity, inhibiting pancreatic cancer cell proliferation (Cheng et al., 2021). Papaverine, an isoquinoline-type alkaloid reported to inhibit LDHA, is currently undergoing clinical trials as a radiosensitizer aimed at reducing tumor hypoxia and enhancing the radiotherapy response in A549 non-small cell lung cancer cell (NSCLC) and EO771 breast cancer xenografts (Kapp and Whiteley, 1991; Benej et al., 2018).

Alkaloids, such as berberine, vincamine, rutaecarpine, chelerythrine, and matrine, have been investigated for their therapeutic potential in various cardiovascular diseases (Yamamoto et al., 2001; Jia and Hu, 2010; Zhang and Yan, 2020; Zhang et al., 2021b; Cai et al., 2021). Berberine has been found to inhibit LDH activity in H9c2 cardiomyocytes, providing protection against ischemia/reperfusion injury (Zhu et al., 2020). Berberine treatment has also been shown to decrease lactate production and increase ATP production in cardiomyocytes, improving cellular energy metabolism through LDH activity inhibition (Lv et al., 2012).

Leonurine, derived from the Lamiaceae family, exhibits cardioprotective effects by decreasing LDH activity and exerting anti-oxidative activity (Liu et al., 2010). Additionally, rutaecarpine, chelerythrine, and matrine have been shown to inhibit LDH levels (Bao et al., 2011; Chen and Huang, 2012; Wu et al., 2022). Of these, rutaecarpine confers protection against myocardial cell injury by inhibiting the NADPH oxidase–ROS pathway (Tian et al., 2019).

In neurological diseases, LDH can serve as a marker for cell damage or death (Adan et al., 2016). Conditions such as stroke, traumatic brain injury, or neurodegenerative disorders can lead to cellular injury or necrosis (Mehta et al., 2013), causing LDH release into the extracellular space (Al Shammari et al., 2015). Elevated LDH levels in the cerebrospinal fluid or blood indicate cellular damage or loss (Fang et al., 2022). Alkaloids derived from Amaryllidaceae species have shown acetylcholinesterase (AChE) inhibitory activity, making them potential candidates for Alzheimer’s disease treatment (Marucci et al., 2021). These alkaloids protect neurons against glutamate-induced damage, reducing apoptotic nuclei and LDH release, indicating reduced cell death and damage (Cortes et al., 2015). These alkaloids may indirectly affect LDH activity through the regulation of acetylcholine levels, which impact cellular metabolism (Kim et al., 2017).

Terpenoids, also known as isoprenoids, are a diverse class of chemical compounds found in a wide range of fruits, vegetables, and herbs (Thoppil and Bishayee, 2011). They exhibit numerous biological activities, including anti-cancer properties, (Yang et al., 2020), making them effective against various cancers, such as skin, breast, colon, pancreatic, and prostate cancers. Terpenoids also possess immune-modulating, anti-viral, anti-allergic, and anti-bacterial properties (Thoppil and Bishayee, 2011). Some terpenoids have shown potential for developing anti-cancer drugs as they inhibit LDH activity and reduce lactate production in cancer cells (Kooshki et al., 2022). In patients with idiopathic pulmonary fibrosis, increased levels of LDHA protein and lactate have been associated with reduced lung function (Judge et al., 2018), and gossypol, a terpenoid, has been studied for its potential to decrease the expression of hypoxia-inducible factor 1 alpha (HIF-1α) in lung fibroblast cells (Judge et al., 2017).

Artemisinins, derived from sweet wormwood (Artemisia annua), are well-known for their anti-malarial properties and are widely used for malaria treatment (Das, 2012). Dihydroartemisinin, an artemisinin derivative, exerts inhibitory effects on glycolytic metabolism in NSCLC cell lines by suppressing the glucose transporter glucose transporter 1 and impeding glucose absorption (Mi et al., 2015). This compound can also induce perturbations in lactate generation and a concomitant reduction in ATP synthesis (Guerra et al., 2018). Additional experiments have shown that dihydroartemisinin effectively reduces the expression of pyruvate kinase M2 (PKM2) in K562, HepG2, and ESCC cells (Li et al., 2019a).

Limonin, a limonoid present in tangerines, grapefruit, and oranges, exhibits diverse biological functions, including anti-inflammatory and anti-viral properties (Balestrieri et al., 2011; Yang et al., 2014; Gualdani et al., 2016). It has been reported to have anti-tumor activity against breast, liver, colon, and pancreatic cancers (Rahman et al., 2015; Murthy et al., 2021a). Limonin’s inhibitory effect on hexokinase-2 (HK-2) activity was investigated in hepatocellular carcinoma cells, where it effectively suppressed HK-2 activity, leading to decreased cell proliferation and colony formation through reduced glucose consumption and lactate production (Yao et al., 2018). Nimbolide, a limonoid derived from the neem tree (Azadirachta indica A. Juss), has demonstrated cytotoxic effects by regulating proliferation, apoptosis, migration, and invasion in various cancer cell lines (Jaiswara and Kumar, 2022).

Oleanolic acid, a natural triterpenoid, is known for its beneficial properties, including anti-inflammatory, anti-oxidant, anti-microbial, hepatoprotective, and anti-cancer activities (Liu, 1995). In endometriosis research, it inhibits LDHA activity in cell lines and induces apoptotic signaling pathways (Cho et al., 2022). Moreover, it suppresses the mTOR signaling pathway and PKM2 production in other breast and prostate cancer cell lines (Liu et al., 2014).

Ursolic acid, another triterpenoid found in various plants, including apple, basil, rosemary, and lavender (Zerin et al., 2016), exhibits various physiological functions, including antibacterial, anti-cancer, anti-diabetic, anti-inflammatory, and anti-oxidant effects (Mlala et al., 2019). For example, it has been shown to reduce LDHA expression in a breast cancer cell line (Wang et al., 2021a). Additionally, betulinic acid, astragalus saponin, and crocetin have been found to suppress LDHA activity and expression, leading to reduced glucose uptake and downregulation of the glycolysis pathway (Kim et al., 2014; Granchi et al., 2017; Guo et al., 2019; Jiao et al., 2019).

In one study, the terpenoid ferruginol was found to reduce LDH and creatine kinase MB levels, indicators of doxorubicin-induced tissue damage (Li et al., 2021a). The study revealed that ferruginol mitigated apoptosis progression, as shown in a TUNEL assay in response to doxorubicin. Ferruginol’s cardioprotective action was demonstrated through the preservation of mitochondrial integrity, limitation of ROS-induced heart damage, and attenuation of apoptosis. These effects are likely mediated through the SIRT1 pathway, which regulates mitochondrial biogenesis and fatty acid oxidation.

Thymoquinone, known for its anti-inflammatory, anti-tumor, and analgesic properties (De Sousa, 2011; Sá et al., 2014; Sobral et al., 2014), exhibits anti-oxidant and vascular relaxant effects in experimental models of cardiovascular disease. Thymoquinone administration in mice improved superoxide dismutase activity, reduced interleukin-6 levels, and prevented cardiovascular side effects (Nemmar et al., 2011). In rats with isoproterenol-induced myocardial infarction treated with thymoquinone, dose-related decreases in plasmatic LDH, thiobarbituric acid reactive substances, and glutathione reductase were observed (Randhawa et al., 2013).

Regarding ursolic acid, prominent expression of LDH among serum marker enzymes was observed in myocardial ischemia–induced mice. Following ursolic acid treatment, significant protection against cardiac injury was evident, with a marked reduction in LDH activity (Radhiga et al., 2012).

Derived from Ginkgo biloba leaves, Ginkgolide B is a terpenoid diterpene lactone (Iwamoto et al., 2019) known for its anti-inflammatory and neuroprotective properties (Zhang et al., 2011). Ginkgolide B activates the Trk/Ras/MAPK signaling pathway, promoting neurite growth and secretion of brain-derived neurotrophic factors while reducing levels of ROS, LDH, caspase-3, and other proapoptotic factors.

Limonoids have been shown to enhance neuronal differentiation and neurite outgrowth in rat macrophages by activating the PKA/ERK1/2 signaling pathway (Roy and Saraf, 2006), stimulating the secretion of nerve growth factor, and attenuating LDH activity (Zhang et al., 2013a). Through activation of this pathway, limonoids promote neurite outgrowth in rat macrophages, enhancing neuronal differentiation (Gotoh et al., 1990; Yu et al., 2004).

The vibrant orange hue of carrots and sweet potatoes is due to the presence of ß-carotene (Zeb and Mehmood, 2004), a compound that serves as a precursor to vitamin A and is known for its anti-oxidant properties and potential health benefits (Thomas and Oyediran, 2008). ß-carotene plays a protective role in the brain, guarding against the harmful effects of cadmium-induced oxidative stress (Gonzalez-Burgos and Gómez-Serranillos, 2012). It enhances ATPase activity, reduces LDH activity and lipid peroxidation, and contributes to the surge of both enzymatic anti-oxidants, such as glutathione S-transferase and superoxide dismutase, and nonenzymatic anti-oxidants, including glutathione (Park et al., 2011).

Eucommia ulmoides Oliv. Bark contains geniposidic acid, one of its active ingredients (Xie et al., 2015). Geniposidic acid not only inhibits LDH but also PARP, cleaved caspase 3, MMPs, and cytochrome C, while increasing the levels of Bcl-2, Bcl-xL, and BDNF (Kwon et al., 2012). These combined effects result in an anti-apoptotic effect and suggest potential applications in the prevention or treatment of neurodegenerative diseases, such as Alzheimer’s disease (Venkatesan et al., 2015).

Allicin is a bioactive sulfur compound mainly stored in a precursor form in various plant parts. It is known to possess cardioprotective, anti-microbial, cholesterol-lowering, anti-inflammatory, and anti-tumor properties (Catanzaro et al., 2022). In experiments involving the combination treatment of tamoxifen and allicin on Ehrlich ascites carcinoma, both in vitro and in vivo, LDH levels were reduced, and there was a significant decrease in tumor growth (Suddek, 2014). Furthermore, in an experiment conducted on male Swiss albino mice, it was confirmed that cardiac oxidative damage was reduced when allicin and doxorubicin were administered together. This reduction in oxidative damage was attributed to a decrease in myocardial expression of activated caspase-3 and cyclooxygenase-2 (Abdel-Daim et al., 2017). In Parkinson’s disease, allicin is also known to have a protective effect against nerve damage related to Parkinson’s disease through its inherent antioxidant function and its ability to reduce LDH release (Liu et al., 2015).

Taurine, an organic compound containing sulfur in its chemical structure, possesses anti-inflammatory, anti-oxidant, and various physiological functions within the cardiovascular, kidney, endocrine, and immune systems (Kim and Cha, 2014). Treatment of the HepG2 cell line, a hepatocellular carcinoma cell line, with taurine resulted in a significant increase in apoptosis-related factors at both the gene and protein levels. Additionally, LDH activity was markedly reduced, indicating the inhibition of glycolysis and cell proliferation (Nabi et al., 2021). Furthermore, taurine has been found to prevent cardiac injury by reducing LDH activity, which is increased by cisplatin (Chowdhury et al., 2016). In neurons, taurine reduced nickel-induced LDH release and mitigated the decrease in ROS production, superoxide dismutase activity, and glutathione concentration, demonstrating its neuroprotective effect through the reduction of oxidative stress (Xu et al., 2015) (Figures 3, 4 and Table 1).

Natural compounds can be rapidly metabolized or excreted from the body, limiting their effectiveness as therapeutics (Fernandes et al., 2014). To address this issue, researchers are exploring various strategies, such as drug delivery systems, chemical modifications, and formulation approaches, to improve the bioavailability of these compounds (Prajapati et al., 2013).

Natural compounds often interact with multiple targets in the body, leading to unexpected side effects (David et al., 2015). Some natural compounds may have off-target effects, resulting in side effects, while others may lack specificity toward cancer cells, causing toxicity to normal cells (Mehta et al., 2010). Researchers are developing combination therapies to enhance the specificity of some compounds for cancer cells and minimize side effects (Koehn and Carter, 2005).

The exact mechanism of action for natural compounds as LDH inhibitors remains unclear, hindering their development as therapeutic agents (Augoff et al., 2015). This lack of understanding makes it challenging to enhance their efficacy and minimize potential side effects. Researchers are employing various methods, including computational modeling, biochemical analysis, and proteomics, to elucidate the mechanisms (Lahlou, 2013).

The absence of standardized protocols for screening and testing natural compounds as LDH inhibitors leads to inconsistent results. Variations in cell lines and assay conditions can contribute to discrepancies in study outcomes. To address this, many researchers are striving to establish a standardized protocol for screening and evaluating natural compounds (Cos et al., 2006).

The nonpatentable nature of natural compounds has reduced commercial interest in their development as therapeutic agents (Li and Vederas, 2009). Additionally, the high costs associated with clinical trials and regulatory approval pose challenges for investing in natural compound–based drugs (Thomford et al., 2018). To overcome these obstacles, researchers are exploring various business models, such as open-source drug discovery, to incentivize the development of natural compounds as therapeutic agents (Sugumaran, 2012).

To develop safe and effective drugs, it is essential to identify the major functional compounds in complex natural compounds. Techniques such as high-performance liquid chromatography, gas chromatography–mass spectrometry, and nuclear magnetic resonance, can be used for this purpose (Tsao et al., 2003; Garcia and Barbas, 2011; Wang et al., 2021b). The complexity of some natural compounds makes it challenging to pinpoint the desired therapeutic effect. Utilizing various methods can help identify the principal operational constituent within the complex blend, facilitating the formulation of effective and secure pharmaceuticals.

Natural compounds often have low potency and selectivity against the target enzyme due to their low concentrations in their natural sources (Ochoa-Villarreal et al., 2016; Cazzaniga et al., 2021). Optimization of bioactivity can be achieved through structural modification, semi-synthesis, or total synthesis of natural compounds (Prachayasittikul et al., 2015). Structural modification can be applied to enhance the pharmacological properties of natural compounds (Guo, 2017). This process entails altering the compound’s stereochemistry or adding and removing functional groups. For instance, taxol, a natural compound with limited therapeutic potential owing to its low solubility in water (Dordunoo and Burt, 1996), underwent chemical modification to create a more soluble variant known as docetaxel, which has become a popular cancer medication (Hanauske et al., 1992; Fitzpatrick and Wheeler, 2003). Semi-synthesis, which involves analog production through chemical reactions, is another approach for enhancing the pharmacological properties of natural compounds (Lourenco et al., 2012). Although it is not as demanding as total synthesis, semi-synthesis remains effective in improving the compound’s bioactivity. An excellent example of semi-synthesis is the transformation of artemisinin into artesunate, resulting in a more potent variant now used in malaria treatment (White and Olliaro, 1998). Total synthesis the complete chemical synthesis of the natural compound from simple starting materials (Atanasov et al., 2021), represents the most challenging method of bioactivity optimization, but it can also be the most effective. For example, the natural compound shikonin has been completely synthesized, leading to the development of new drugs for the treatment of cancer and other diseases (Andujar et al., 2012; Wang et al., 2012).

Pharmacokinetic properties, including solubility, stability, bioavailability, and metabolic stability, are crucial considerations in drug development (Sang et al., 2019). Some natural compounds exhibit poor pharmacokinetic properties, which can impede their development as therapeutic agents (Ma et al., 2022). To address this, prodrugs can be used, which are inert compounds that undergo metabolic transformation within the body to generate the active drug (Huttunen et al., 2011). Prodrugs can enhance the stability, solubility, and bioavailability of natural compounds, making them more effective in disease treatment. Additionally, formulation technologies, such as liposomes, nanoparticles, and cyclodextrins, can improve the solubility, stability, and release control of natural compounds, making them easier to administer and more effective (Augustin et al., 2013). Conjugation with suitable carriers, including polyethylene glycol, albumin, and dendrimers, is another approach to optimize pharmacokinetic properties, with this strategy aiming to enhance the overall efficacy of natural compounds as potential therapeutic agents (Gidwani and Vyas, 2015).

There are various nano-formulation types, including liposomes, hydrogels, solid lipid nanoparticles, polymeric nanomicelles, dendrimers, chitosan-based nanoparticles, metal nanoparticles, and nanocrystals, which are under investigation for their application with natural compounds (Murthy et al., 2021b). Nano-formulations can safeguard polyphenols against degradation, enhance absorption, and reduce toxicity, making them well-suited for delivering compounds (Khiev et al., 2021). These delivery systems offer advantages such as improved solubility, oral absorption, safety, and bioavailability. Researchers are currently testing the in vitro and in vivo efficacy of polyphenols like curcumin, quercetin, resveratrol, silybin, luteolin, naringenin, genistein, gossypol, ellagic acid, and hesperidin for treating various diseases (Murthy et al., 2021b).

Curcumin, a polyphenol, exhibits variations in its effects depending on the type and form of nanoparticles and has been extensively studied in various disease models, including malaria, cancer, and cerebral ischemia (Maheshwari et al., 2006; Tsai et al., 2011; Rahimi et al., 2016). The application of these nanoparticle forms has resulted in various effects, including increased solubility and circulation time, enhanced anti-tumor effects and bioavailability, improved anti-oxidative properties, and brain delivery (Liu and Chang, 2011; Liu et al., 2011; Liu et al., 2013). Camptothecin, a natural plant alkaloid, has demonstrated potent anti-tumor activity by targeting intracellular topoisomerase I (Pommier, 2006). The application of nanoformulation has been shown to enhance the efficacy of cancer treatment by addressing limiting factors such as water insolubility (Ghanbari-Movahed et al., 2021). Terpenoids have also been studied for their potential to improve the effectiveness of gastric cancer treatment by increasing anti-cancer and anti-bacterial efficacy through nanoconjugates, and by addressing shortcomings such as target delivery, stability, and half-life (Attri et al., 2023).

The green synthesis of silver nanoparticles from extracts of various plant parts has attracted widespread interest among researchers due to their unique optical and structural properties (Habeeb Rahuman et al., 2022). The green synthesis of nanoparticles is biocompatible and has potential applications in catalysts, anti-bacterial agents, energy harvesting, cancer/gene therapy, and sensing (Rana et al., 2020). Biological methods for nanoparticle synthesis are more economical, easier to implement, have a lower environmental impact, and require fewer processing steps than chemical and physical methods (Kumari et al., 2019). Plants contain polyphenols, flavonoids, alkaloids, and other biomolecules that work synergistically to inhibit oxidative damage to cellular components, leading to the reduction of metal ions into nanoparticles (Mohanpuria et al., 2008; Krishnaraj et al., 2014). Numerous studies have reported the synthesis of gold nanoparticles (AuNPs) using extracts from various plant parts. The putative biomolecules involved in the reduction of gold salts to gold nanoparticles include flavonoids, gingerol, shogaols, gingerone, paradol, catechin, proteins, aromatic amines, and aliphatic amines (Raghunandan et al., 2010; Kumar et al., 2011; Suman et al., 2014). However, the fundamental molecular mechanisms involved in nanoparticle formation are not fully understood, and further studies using natural products are needed.

Natural compounds often possess broad-spectrum activity against multiple targets, posing a challenge in developing specific inhibitors for the target enzyme. Target specificity is crucial in drug development, as it minimizes the potential for off-target effects and improves the therapeutic index of the drug (Mizuno et al., 2003). Several methods can be employed to enhance the specificity of natural compounds. Structure-based design uses computer modeling to develop compounds that specifically bind to target enzymes (Read et al., 2001b), with this approach being especially effective when the three-dimensional structure of the enzyme is already known (Schmidt et al., 2014). Molecular docking, employing computer algorithms, predicts compound binding to the intended enzyme (Abdolmaleki et al., 2017). To improve specificity, one strategy involves identifying compounds that favor the target enzyme while having minimal impact on off-target enzymes (Xu et al., 2021). High-throughput screening on compound libraries is another approach (Mayr and Bojanic, 2009), testing a large number of compounds to identify those that work well with the target enzyme while suppressing other enzymes (Bachovchin et al., 2009).

Toxicity concerns are prevalent in drug development, especially when working with natural compounds, as they have the potential to harm healthy cells (Ali Abdalla et al., 2022). One approach to reduce toxicity is through the use of prodrugs and proper carriers. Various techniques, including conjugation, can decrease toxicity by refining pharmacokinetic features, enhancing precision in targeting disease cells, and minimizing risks to healthy cells (Ma et al., 2019).

Combining natural compounds with suitable carriers has led to successful cancer treatments, such as antibody-drug conjugates, which function by attaching a toxin to an antibody that specifically targets cancer cells, delivering the toxin directly to the intended site (Dosio et al., 2011). This targeted delivery system not only reduces toxicity in healthy cells but also enhances the cancer cell specificity of natural compounds (Puthenveetil et al., 2016). An example of this progressive method involves combining a special peptide with curcumin, which specifically targets EGFR and has a more pronounced impact on suppressing breast cancer cells. The peptide–curcumin conjugate directs its attention toward EGFR-positive cancer cells, hindering their growth without significantly affecting healthy cells (Jin et al., 2017).

The development of natural compounds as LDH inhibitors faces a major obstacle in the form of intellectual property challenges. Given that these compounds are found in nature, they cannot be patented, preventing companies from obtaining exclusive rights to their use (Harrison, 2014). To address this issue, one possible solution is to create modified medications with unique characteristics (Kirschning et al., 2007). These modified versions can be patented as fresh innovations, protecting the investment in drug development while still making the original natural compound available for other purposes. Additionally, exploring innovative delivery systems can enhance the potency of natural compounds and reduce their harmful effects. Overcoming the complexities of intellectual property allows companies to secure exclusive rights to the use of delivery technologies, facilitating the development of effective and commercially viable natural compound–based drugs.

Clinical trials play a critical role in evaluating the safety and efficacy of drug candidates before their approval for human use (Deore et al., 2019). Extensive preclinical and clinical testing is essential for natural compounds being developed as LDH inhibitors to assess their safety and efficacy in humans. Clinical trials for LDH inhibitors present unique challenges but are vital for evaluating the safety and efficacy of these compounds in humans. Developing LDH inhibitors for cancer treatment requires specific patient populations and endpoints for clinical trials. Currently, no United States Food and Drug Administration–approved LDH inhibitors for cancer treatment exist, and their development necessitates comprehensive clinical testing to assess efficacy and safety. Some natural compounds, such as gossypol and galloflavin, have shown potential as LDH inhibitors in preclinical studies, demonstrating both LDH activity inhibition and anti-cancer properties (Cui et al., 2017; Rani and Kumar, 2017). LDHB is associated with an aggressive cancer phenotype, and there are studies aimed at identifying and clinically applying selective inhibitors for LDHB (McCleland et al., 2012; Shibata et al., 2021). In a study of clinical samples from colorectal cancer patients, a significant correlation was observed between MYC expression and the expression of multiple metabolic genes, accompanied by elevated LDHB levels, while LDHA levels remained unchanged (Satoh et al., 2017). The approach of promoting cancer cell necrosis through the inhibition of lactate transport is presently being employed in initial clinical trials as a potential cancer treatment strategy, utilizing the selective MCT-1 inhibitor known as AZD3965 (Beloueche-Babari et al., 2020).

No existing LDH inhibitors have yet shown clinically significant effects, but research is underway to discover new ones using computer-based structure-based virtual screening methods (Di Magno et al., 2022). However, the clinical advancement of these compounds faces challenges, including effectiveness, toxicity, specificity, and bioavailability. These obstacles underscore the importance of thorough preclinical and clinical testing in advancing natural compounds as LDH inhibitors.