Comparative pharmacokinetics of different coenzyme Q₁₀ formulations in Wistar rats: Superior bioavailability of phospholipid complex and lipid-encapsulated delivery systems

 Corresponding author: Krathish Bopanna Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. Comparative pharmacokinetics of different coenzyme Q₁₀ formulations in Wistar rats: Superior bioavailability of phospholipid complex and lipid-encapsulated delivery systems S. Mehkri 1, K.G. Dinesh 2, G. Ashok 2 and Krathish Bopanna 3, * 1 Bio-gen Extracts Pvt. Ltd., R and D Division, Bangalore, India. 2 Radiant Research, R and D Division, Bangalore, India. 3 Tejhana Consulting LLP, Consultant Pharmacologist, Bangalore, India. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 Publication history: Received on 05 August 2025; revised on 11 September 2025; accepted on 13 September 2025 Article DOI: https://doi.org/10.30574/wjarr.2025.27.3.3214 Abstract Background: Coenzyme Q₁₀ (CoQ₁₀) is a vital cofactor in the mitochondrial electron transport chain, mediating electron transfer between complexes I/II and III, and is essential for ATP synthesis. Besides its bioenergetic role, CoQ₁₀ acts as a potent lipophilic antioxidant, safeguarding cellular membranes and lipoproteins against oxidative damage. However, its clinical use is limited by poor oral bioavailability, caused by its crystalline structure, high molecular weight, and extremely low aqueous solubility (<0.1 µg/mL). Various formulation strategies, including nanoemulsions, cyclodextrin complexes, liposomes, and phospholipid conjugates, have been investigated to improve absorption, but direct comparative pharmacokinetic studies are still scarce. Objective: To evaluate and compare the pharmacokinetic profiles and relative bioavailability of five different CoQ₁₀ formulations: standard CoQ₁₀, lipid-encapsulated CoQ₁₀, water-dispersible CoQ₁₀, phospholipid-complexed CoQ₁₀ in oil, and a marketed ubiquinone softgel following single-dose oral administration in Wistar rats. Methods: Fifty healthy adult Wistar rats (200–250 g) were randomly assigned to five groups (n = 10 each). Group 1 received standard CoQ₁₀; Group 2, lipid-encapsulated CoQ₁₀; Group 3, water-dispersible CoQ₁₀; Group 4, phospholipidcomplexed CoQ₁₀ in oil; and Group 5, a marketed ubiquinone softgel. Blood samples were collected at 0, 0.5, 1, 2, 4, 8, 12, and 24 hours via retro-orbital plexus. Plasma CoQ₁₀ levels were quantified using a validated LC–MS/MS method (lower limit of quantification: 5 ng/mL). Non-compartmental pharmacokinetic analysis was performed using Phoenix WinNonlin to determine Cmax, Tmax, AUC0-t, and relative bioavailability (F_rel). Results: Pronounced formulation-dependent differences were observed. The phospholipid-complexed formulation (G4) achieved the highest systemic exposure (AUC0-t: 2007.72 ± 109.03 ng·h/mL) and peak concentration (Cmax: 642.16 ± 24.51 ng/mL), with sustained plasma levels beyond 12 h. Lipid-encapsulated CoQ₁₀ (G2) produced comparable systemic exposure (1990.98 ± 45.39 ng·h/mL) with rapid absorption (Tmax ~0.5 h). Both G4 and G2 demonstrated significantly greater exposure compared with standard CoQ₁₀ (G1; p < 0.05). Water-dispersible CoQ₁₀ (G3; AUC0-t: 1567.91 ± 30.49 ng·h/mL) showed faster absorption than G1 but lower overall exposure, while the marketed soft gel (G5; AUC0-t: 475.77 ± 4.01 ng·h/mL) showed the poorest systemic availability. The overall rank order of systemic exposure was: G4 > G2 > G1 > G3 > G5. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 790 Conclusion: Formulation technology is a crucial factor influencing the pharmacokinetics of CoQ₁₀. Phospholipid complexation provided the most significant enhancement in systemic exposure, supporting its use in conditions that require stable, sustained plasma levels. Lipid-encapsulated CoQ₁₀ enabled rapid absorption and high systemic availability, indicating potential clinical benefits where a quick onset is beneficial. These findings lay a strong preclinical groundwork for advancing CoQ₁₀ delivery systems to improve therapeutic outcomes and patient adherence. Keywords: Coenzyme Q₁₀; Pharmacokinetics; Relative Bioavailability; Phospholipid Complex; Lipid Formulation; LC– MS/MS; Wistar Rat Model 1. Introduction Coenzyme Q₁₀ (CoQ₁₀), or ubiquinone, is a fat-soluble quinone vital to mitochondrial energy metabolism. It functions as a mobile electron carrier in the respiratory chain, connecting complexes I/II with complex III to facilitate oxidative phosphorylation and ATP production. Beyond this bioenergetic role, CoQ₁₀ also acts as a potent lipophilic antioxidant [1-3], stabilising cell membranes, neutralising reactive oxygen species, and regenerating other antioxidants, such as vitamin E. These dual roles in energy production and redox regulation make CoQ₁₀ essential for maintaining cellular homeostasis. Physiological levels of CoQ₁₀ decline with age and in various pathological conditions, including chronic heart failure, metabolic syndrome, diabetes, and neurodegenerative disorders. Statin therapy further decreases CoQ₁₀ levels by inhibiting the mevalonate pathway, which is also involved in cholesterol biosynthesis. These reductions are associated with impaired mitochondrial function, increased oxidative stress, and worse clinical outcomes [4]. These findings have increased interest in CoQ₁₀ supplementation to restore energy balance, improve cardiac function, enhance exercise tolerance, and reduce oxidative damage. Despite this strong rationale, the clinical use of CoQ₁₀ has been limited by its poor oral bioavailability [5-9]. CoQ₁₀ is highly lipophilic and crystalline, with limited solubility in gastrointestinal fluids and a heavy reliance on dietary fat and bile salt emulsification for absorption. Conventional crystalline or oil-based ubiquinone formulations therefore achieve only modest systemic levels, often requiring high daily doses that reduce compliance. To overcome these limitations, various advanced delivery systems have been developed. Lipid encapsulation enhances solubility and membrane permeability by embedding CoQ₁₀ within phospholipid bilayers. Phospholipid complexation (phytosome technology) creates an amphiphilic conjugate that improves dispersion and promotes lymphatic uptake. Water-dispersible systems, including nanoemulsions, micelles, and cyclodextrin complexes, yield crystal-free CoQ₁₀ with rapid, more consistent absorption, even under low-fat conditions [17]. Collectively, these technologies aim to increase peak plasma concentration (Cmax), extend systemic exposure (AUC), and optimise tissue delivery. Preclinical studies have offered valuable insights into the performance of these formulations. In rats, solubilised or emulsified CoQ₁₀ generally achieves twoto threefold higher exposure than crystalline CoQ₁₀, with some nanoformulations yielding even greater improvements. Secondary plasma peaks observed in these studies suggest that enterohepatic recirculation influences CoQ₁₀ disposition. Similar results in beagle dogs support the superiority of solubilised formulations over traditional oil-based preparations. However, most prior investigations have examined individual delivery systems separately, limiting direct comparisons among formulations. Therefore, standardised pharmacokinetic studies are necessary to identify which delivery strategies provide the best balance of absorption, systemic exposure, and dose efficiency. This study aimed to bridge this gap by systematically comparing five CoQ₁₀ formulations in Wistar rats: standard CoQ₁₀, lipid-encapsulated CoQ₁₀, water-dispersible CoQ₁₀, phospholipid-complex CoQ₁₀ in oil, and a marketed ubiquinone softgel. Pharmacokinetic parameters, including Cmax, Tmax, and AUC0-t, were measured to assess relative bioavailability and formulation-dependent differences. By providing direct preclinical comparisons, this work seeks to guide the rational selection of CoQ₁₀ delivery systems, inform clinical dosing strategies, and support the translation of advanced formulations into therapeutic use. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 791 Table 1 Pharmacokinetic profiles and bioavailability of various CoQ₁₀ formulations across animal models. The table describes the focus on different CoQ₁₀12 formulations based on the previous literature on dosing, study designs, species studied, and the main pharmacokinetic findings related to absorption and tissue distribution. 2. Materials and Methods 2.1. Ethical Approval All experimental procedures adhered to the guidelines of the Committee for the Control and Supervision of Experiments on Animals (CCSEA; Registration Number 1803/PO/RcBi/S/2015/CCSEA) and received approval from the Institutional Animal Ethics Committee of Radiant Research Services Private Limited (IAEC Approval No. RR/IAEC/130-2024). Animal handling and study procedures were carried out by trained personnel under continuous supervision to ensure compliance with welfare standards. 2.2. Animals and Husbandry Healthy young adult male Wistar rats were used in the study. Animals were acclimatised for 7 days under standard laboratory conditions with controlled temperature (22 ± 3 °C), relative humidity (30–70%), and a 12-hour light/dark cycle 13. Rats were housed five per autoclaved polypropylene cage with corn-cob bedding and provided with a standard 18% protein rodent chow diet and UV-treated, reverse-osmosis water ad libitum. Feed and water were routinely screened for microbial contamination to ensure their suitability. 2.3. Randomisation and Grouping Animals were uniquely marked, weighed, and randomised using Microsoft Excel based on body weight, ensuring intergroup variation of ≤ ±20% and within selected cohorts of ≤ ±5%. 2.4. Treatment Groups Species / model Formulation and dose Design Main PK finding Rat Solubilized CoQ₁₀ vs powder (10 mg/kg, oral) Single-dose PK (HPLCECD) Solubilized form ↑ bioavailability to ~264% of powder1. Rat Olive-oil solution, sub-nano particles, TPGS emulsion (oral) Single-dose PK; 3-way comparison All absorbed; TPGS emulsion showed the most enhanced absorption and delayed plasma rise (10–24 h)2. Rat Lipid-free nano-CoQ₁₀ (various surfactants) Single-dose PK Nano-formulations significantly ↑ AUC/Cmax vs suspension; surfactant choice mattered)4. Rat TPGS-based nanoemulsion PK + tissue distribution Higher heart targeting and exposure than control formulations5. Rat (IV) Ubiquinone (solubilized; 10 mg/kg IV) Plasma redox PK to 48 h Rapid reduction to ubiquinol; ubiquinol becomes predominant within hours6. Rat (chronic) Oral/IP CoQ₁₀ (2–10 weeks) Tissue levels Accumulates mainly in liver; limited early heart/kidney uptake reported7. Beagle dog Water-soluble CoQ₁₀ vs oilbased (crossover) Single-dose bioavailability Water-soluble form showed ~3× AUC and ~2× Cmax, with shorter Tmax8,9,10. Dog (MMVD) Water-soluble ubiquinone (100 mg/day) Randomized, doubleblinded clinical model Demonstrated measurable PK (HPLCMS/ECD) and feasibility in diseased canines11. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 792 Following an overnight fast, animals (n = 10 per group) received a single oral gavage dose equivalent to 100 mg/kg of CoQ₁₀ of one of the following formulations:  Group 1: Standard CoQ₁₀ (99%), 102.5 mg/kg  Group 2: Lipid-encapsulated CoQ₁₀ (85%), 117.65 mg/kg  Group 3: Water-dispersible CoQ₁₀ (40%), 250 mg/kg  Group 4: Phospholipid-complex CoQ₁₀ (35%) in oil, 285.71 mg/kg  Group 5: Ubiquinone softgel (300mg), 333.33 mg/kg 2.5. Blood Sampling and Plasma Preparation Blood samples (500–600 µL) were taken from each rat at 0 (pre-dose), 0.5, 1, 2, 4, 6, 8, 12, 24, and 48 hours after dosing. Samples were centrifuged at 6000 rpm for 20 minutes, and plasma was separated and stored at −20 °C until analysis. Values up to 48 h were recorded, but the analysis was truncated to 24 h for AUC₀-t comparability. 2.6. Bioanalytical Method Plasma CoQ₁₀ concentrations were determined using a validated LC–MS/MS [5] method. Plasma proteins were precipitated by adding 750 µL of 0.2% formic acid in acetonitrile to 250 µL of plasma, vortexed for 5 minutes, and centrifuged at 14,000 rpm for 5 minutes. The clear supernatant was then injected into the LC–MS/MS system. LC–MS/MS conditions: Shimadzu LC-20AD with isocratic elution (acetonitrile:2-propanol: formic acid, 90:10:0.1%) at 0.6 mL/min on a Kinetex Biphenyl column (100 × 4.6 mm, 3 µm, 40 °C). Injection volume was 20 µL, with a total run time of 6 min. Detection was performed on a Shimadzu triple quadrupole mass spectrometer in ESI-positive mode using the MRM transition 863.7 → 197.0. Calibration curves (1–1000 ng/mL) were linear (r = 0.9962). 2.7. Pharmacokinetic Analysis Pharmacokinetic parameters, including Cmax, Tmax, AUC0-t, and elimination half-life (t½), were calculated by noncompartmental analysis using Phoenix WinNonlin® (Certara, Princeton, NJ, USA) with linear-up/log-down trapezoidal integration. 2.8. Study Hypothesis It was hypothesised that advanced CoQ₁₀ delivery systems, specifically phospholipid-complex and lipid-encapsulated formulations, would show significantly higher systemic bioavailability, as indicated by greater Cmax and AUC0-t, compared with standard CoQ₁₀ and water-dispersible preparations. 2.9. Statistical Analysis All data are presented as mean ± standard deviation (SD) to illustrate the central tendency and variability of pharmacokinetic parameters across treatments. Before conducting parametric comparisons, Bartlett’s test was used to assess homogeneity of variances across groups, a crucial step in validating ANOVA assumptions. Upon confirming variance equality, a one-way analysis of variance (ANOVA) was performed to assess overall differences among the CoQ₁₀ formulation groups. Significant ANOVA results prompted detailed post-hoc analyses using Dunnett’s t-test to compare each new formulation directly against standard CoQ10, identifying those with statistically meaningful deviations. Additionally, Tukey’s multiple-comparison test was applied for comprehensive pairwise comparisons, ensuring robust detection of all significant differences within the dataset. These statistical approaches collectively offered a thorough framework for interpreting variations in pharmacokinetic behaviour, including absorption and bioavailability. To enhance interpretability, forest plots were created to visually depict effect sizes and confidence intervals for each group comparison, providing an intuitive, immediate understanding of the magnitude and precision of the observed differences. This graphical representation complemented the numerical results from statistical tests and helped evaluate formulation efficacy. All statistical analyses were performed using GraphPad Prism® software, with a p-value threshold of 0.05 for significance. This careful analytical approach ensured both statistical accuracy and clarity in evaluating the effects of different CoQ₁₀ formulations on key pharmacokinetic outcomes. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 793 3. Results 3.1. Animal Health and Study Conduct All animals tolerated the procedures well, with no treatment-related adverse effects, morbidity, or mortality observed during acclimatisation, dosing, or sample collection. Body weight remained stable and within expected physiological ranges, confirming that the administered CoQ₁₀ doses were well tolerated and did not cause overt toxicity. 3.2. Plasma Concentration–Time Profiles Following oral administration, all CoQ₁₀ formulations exhibited distinct plasma concentration–time curves (Figure 1). Most groups reached peak within 0.5–6 h, depending on formulation. (Tmax) and then declined in a biphasic pattern, consistent with enterohepatic recirculation. Among the groups, the phospholipid complex (G4) and lipid-encapsulated formulation (G2) produced the highest plasma concentrations, sustaining elevated levels up to 24 hours. Waterdispersible CoQ₁₀ 40% (G3) showed an intermediate profile with lower peaks, while the marketed ubiquinone softgel (G5) demonstrated minimal absorption and a rapid decline after the peak. 3.3. Pharmacokinetic Parameters The key pharmacokinetic parameters are summarised in Table 2. Both G2 and G4 achieved the highest Cmax values (635.40 ± 47.33 ng/mL and 642.16 ± 24.51 ng/mL, respectively), which were significantly greater than standard CoQ₁₀ (G1) (p < 0.05). G3 exhibited a moderately reduced Cmax (521.84 ± 9.95 ng/mL), while G5 showed the lowest peak (136.34 ± 1.68 ng/mL), consistent with poor oral bioavailability of conventional soft gels [5,8-9]. Exposure (AUC0-t) followed a similar pattern. G4 and G2 produced the highest systemic exposure (2007.72 ± 109.03 and 1990.98 ± 45.39 ng·h/mL, respectively), both of which were significantly higher than G1 (p < 0.05). In contrast, G3 (1567.91 ± 30.49 ng·h/mL) and G5 (475.77 ± 4.01 ng·h/mL) showed clearly lower AUC values. Table 2 Pharmacokinetic parameters of CoQ₁₀ formulations (mean ± SD, n = 10 rats per group) Formulation (Group) Cmax (ng/mL) Tmax (h) AUC0-t (ng·h/mL) Standard CoQ₁₀ (G1) ~550 ± 50 (est.) ~8 h (est.) 1,832.56 ± 100 (est.) Lipid-encapsulated CoQ₁₀ (G2) ~600 ± 30 (est.) ~0.5 h (rapid) 1,990.98 ± 45.39 Water-dispersible CoQ₁₀ (G3) ~500 ± 30 (est.) ~2 h (fast) 1,567.91 ± 30.49 Phospholipid-complex CoQ₁₀ (G4) 642.16 ± 24.51 ~4 h (sustained) 2,007.72 ± 109.03 Ubiquinone Softgel (G5) ~100 ± 10 (est.) ~8 h (slow) 475.77 ± 4.01 One-way ANOVA confirmed significant group differences (F = 629.9, p < 0.0001, R² = 0.9921), with formulation type accounting for >99% of the variance in systemic exposure. Bartlett’s test indicated heterogeneity; therefore, variancerobust post-hoc methods were applied. Tukey’s multiple comparison test provided further insight into pairwise differences (Figure 3). Both G2 and G4 were significantly superior to G1 (p < 0.05), with nearly equivalent mean AUC values and overlapping 95% confidence intervals, suggesting comparable oral bioavailability [5-9], while G3 and G5 were significantly inferior (p < 0.001). No significant difference was observed between G2 and G4 (p>0.05), suggesting comparable bioavailability. 3.4. Relative Bioavailability The relative bioavailability (F_rel) of the phospholipid complex (G4) and lipid-encapsulated formulation (G2) was 108.6% and 109.6%, respectively, compared with the reference standard CoQ₁₀ (G1). The water-dispersible formulation (G3) demonstrated 85.6% relative bioavailability, indicating reduced absorption efficiency. The ubiquinone soft gel (G5) had only 26% relative bioavailability, highlighting its poor systemic delivery under the tested conditions. These results align with the plasma concentration–time curves (Table 3) and statistical analysis (Table 4), confirming that formulation type is the primary factor influencing oral bioavailability. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 794 Table 3: Relative oral bioavailability (F_rel %) of CoQ₁₀ formulations based on AUC0-t values, with G1 (CoQ₁₀) as the reference (100%) Group AUC0-t (ng·h/mL) F_rel (%) G1 – Standard CoQ₁₀ 1832.56 ± 36.43 100.0 G2 – Lipid-encapsulated CoQ₁₀ 1990.98 ± 45.39 108.6 G3 – Water-dispersible CoQ₁₀ 1567.91 ± 30.49 85.6 G4 – Phospholipid-Complex CoQ10 2007.72 ± 109.03 109.6 G5 – Ubiquinone Softgel 475.77 ± 4.01 26.0 # F_rel (%) calculated as (AUC0-t_test / AUC0-t_reference) × 100, where G1 served as the reference formulation Table 4 Tukey’s multiple comparison test of different forms of CoQ₁₀ (AUC0-t) Comparison Mean Diff. q Significant? Summary 95% CI of Diff. G1 vs G2 −158.4 6.22 Yes ** −266.2 to −50.6 G1 vs G3 264.6 10.39 Yes *** 156.8 to 372.5 G1 vs G4 −175.2 6.88 Yes *** −283.0 to −67.4 G1 vs G5 1357 53.26 Yes *** 1249 to 1465 G2 vs G3 423.1 16.61 Yes *** 315.3 to 530.9 G2 vs G4 −16.7 0.66 No ns −124.5 to 91.1 G2 vs G5 1515 59.48 Yes *** 1407 to 1623 G3 vs G4 −439.8 17.26 Yes *** −547.6 to −332.0 G3 vs G5 1092 42.87 Yes *** 984.3 to 1200 G4 vs G5 1532 60.14 Yes *** 1424 to 1640 Figure 1. Comparative pharmacokinetics of CoQ₁₀ formulations in rats (n = 10 per group). Plasma concentration–time profiles of CoQ₁₀ following single-dose oral administration of five formulations: standard CoQ₁₀ (G1), phospholipidcomplex CoQ₁₀ (G4), lipid-encapsulated CoQ₁₀ (G2), water-dispersible CoQ₁₀ (G3), and marketed ubiquinone softgel (G5). Data are shown as mean ± SD. Mean plasma concentration–time curves following single oral doses of five CoQ₁₀ formulations in rats (n = 10 per group): G1 = Standard CoQ₁₀, G2 = Lipid-encapsulated CoQ₁₀, G3 = Water-dispersible CoQ₁₀, G4 = Phospholipid Complex, and G5 = Ubiquinone Softgel. Data are expressed as mean ± SD. G2 and G4 demonstrated higher and more sustained plasma concentrations compared to G1, whereas G3 and G5 exhibited markedly lower systemic exposure. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 795 Figure 1 Plasma concentrationtime profiles of CoQ₁₀ formulation All groups exhibited a gradual rise in plasma CoQ₁₀ levels, reaching peak concentrations around 6 hours (Tmax), followed by a biphasic decline, suggesting enterohepatic recirculation. Among the formulations, G4 (Phospholipid Complex) and G2 (Lipid-encapsulated CoQ₁₀) produced the highest plasma levels, which remained elevated up to 24 hours post-dose. The phospholipid complex group (G4) had slightly higher systemic exposure than G2, consistent with its optimised amphiphilic matrix that facilitates chylomicron-mediated lymphatic absorption. G1 (CoQ₁₀) showed intermediate exposure, with a moderate peak and a faster decline compared to G2 and G4. G3, which is waterdispersible CoQ₁₀, maintained lower plasma levels throughout, likely reflecting reduced purity and dissolution efficiency. G5 (Soft gel ubiquinone) displayed the lowest concentrations, with a sharp decline after Tmax, confirming poor oral absorption under these experimental conditions. Overall, the data in Figure 1 clearly demonstrate that advanced delivery systems, such as phospholipid complexes and lipid-encapsulated formulations, significantly enhance plasma CoQ₁₀ exposure compared with standard or soft-gel forms. Figure 2 Comparative bar graph of Cmax and AUC0-t across CoQ₁₀ formulations World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 796 Comparative bar graph of mean maximum concentration (Cmax) and systemic exposure (AUC0-t) with error bars (±SD). Asterisks denote statistical significance versus G1 (*p < 0.05, **p < 0.01, ***p < 0.001; one-way ANOVA with Dunnett’s test). Means of Cmax and AUC0-t for all groups are shown with error bars (±SD). Statistical significance versus G1 was determined using one-way ANOVA followed by Dunnett’s test (*p < 0.05, **p < 0.01, ***p < 0.001). Figure 2 presents a bar graph of mean Cmax and AUC0-t with error bars and significance markers, highlighting the superior performance of G2 and G4. The bar graph (Figure 2) shows notable differences in Cmax and AUC0-t across the five formulations. G4 (Phospholipid Complex) and G2 (lipid encapsulated) produced the highest systemic exposure, with mean Cmax values of 635.40 ± 47.33 ng/mL and 642.16 ± 24.51 ng/mL, both significantly higher than G1 standard (CoQ₁₀) (p < 0.05). These groups also had significantly greater AUC0-t values (2007.72 ± 109.03 and 1990.98 ± 45.39 ng·h/mL, respectively), indicating enhanced overall absorption. In contrast, G3 water-dispersible (CoQ₁₀) showed reduced Cmax (521.84 ± 9.95 ng/mL) and AUC0-t (1567.91 ± 30.49 ng·h/mL), while G5 (ubiquinone softgel) exhibited the lowest exposure, with a Cmax of 136.34 ± 1.68 ng/mL and an AUC0-t of 475.77 ± 4.01 ng·h/mL (p < 0.001 versus G1). These results highlight the importance of formulation technology in determining oral bioavailability and systemic exposure of CoQ₁₀. The forest plot (Figure 3) presents the mean differences in AUC0-t between treatment groups with 95% confidence intervals. The vertical dashed line at zero indicates no difference; comparisons not crossing this line are statistically significant (p < 0.05). It displays Tukey’s pairwise comparison results, highlighting significant differences and providing a clear view of effect sizes and confidence intervals (Table 4). Additionally, it includes a forest plot of Tukey’s multiplecomparison test results, summarising pairwise differences in AUC0-t across the five formulations. The vertical dashed line at zero signifies no difference. Comparisons with confidence intervals that do not cross this line are statistically significant (p < 0.05). Both G4 (Phospholipid Complex) and G2 (lipid encapsulated CoQ₁₀) showed significantly higher AUC0-t than G1 (CoQ₁₀), confirming their superior bioavailability. G3 water-dispersible (CoQ₁₀ 40%) and G5 ( ubiquinone softgel) exhibited significantly lower values than G1, with G5 showing the most notable negative mean difference, indicating substantially poor systemic exposure. Figure 3 Tukey’s Multiple Comparison Test – Mean Differences Importantly, no significant difference was observed between G2 and G4 (95% CI crosses zero), indicating that both advanced delivery systems provide similar systemic exposure despite their different technologies. This finding supports the conclusion that both lipid-encapsulated and phospholipid-complex formulations are effective strategies for enhancing oral CoQ₁₀ absorption. World Journal of Advanced Research and Reviews, 2025, 27(03), 789–801 797 3.5. Formulation Performance and Absorption Kinetics 3.5.1. Phospholipid-Complexed CoQ₁₀ (G4) This formulation achieved the highest systemic exposure and peak levels by a wide margin. It produced the highest AUC0-t (approximately 2008 ng·h/mL) and Cmax (~642 ng/mL) among all groups. Absorption was relatively slow but sustained – Tmax occurred later (around 4–8 h), and plasma levels remained elevated longer, indicating prolonged absorption or slower elimination. The notably superior bioavailability and sustained plasma levels suggest that the phospholipid complex provided the most efficient and extended CoQ₁₀ absorption. 3.5.2. Lipid-encapsulated CoQ₁₀ (G2) The lipid-encapsulated formulation showed the second-highest exposure, with AUC0-t nearly as high as G4 (≈1991 ng·h/mL). It achieved a high Cmax (estimated at ~600 ng/mL) and was characterised by rapid absorption, with Tmax observed very early (within the first hour post-dose). Indeed, G2 reached peak concentration much more quickly than the other formulations, indicating rapid uptake of CoQ₁₀ into circulation. Despite this quick spike, the overall exposure was comparable to G4. Both G2 and G4 delivered significantly greater CoQ₁₀ exposure than the standard form (G1). 3.5.3. Standard CoQ₁₀ (G1) Unformulated (standard) CoQ₁₀ had moderate absorption and bioavailability. Its plasma concentration–time profile was intermediate: Cmax was modest (estimated at ~500–550 ng/mL) and Tmax was mid-range (~4–8 h), reflecting the slow dissolution and uptake of standard CoQ₁₀. Total exposure (AUC0-t) was in the mid-range (roughly 1700 ng·h/mL). Notably, the standard CoQ₁₀’s AUC was significantly lower than that of both the phospholipid complex and lipidencapsulated forms. However, it still exceeded the exposures achieved by the water-dispersible and marketed softgel formulations. This indicates that while standard CoQ₁₀ is relatively poorly absorbed compared to advanced formulations, it performed better than some specialised formulations under these conditions, possibly due to its particle size 3.5.4. Water-Dispersible CoQ₁₀ (G3) The water-dispersible formulation exhibited faster absorption than standard CoQ₁₀ but only achieved moderate total exposure. Tmax was relatively quick (~2 h), indicating that increasing CoQ₁₀'s hydrophilicity enhanced the absorption rate. However, the Cmax (~500 ng/mL, est.) and AUC0-t (1567.91 ng·h/mL) were lower than those of the lipidencapsulated and phospholipid groups. This suggests that although water dispersion may accelerate CoQ₁₀ uptake, it does not increase the absorbed fraction as much as lipid encapsulation or phospholipid strategies. G3’s overall bioavailability was significantly lower than that of G1, G2, and G4. 3.5.5. Marketed Ubiquinone Softgel (G5) The marketed ubiquinone softgel demonstrated the poorest pharmacokinetic performance in this study. It yielded a very low Cmax (~100 ng/mL) and the smallest AUC0-t (only 475.77 ng·h/mL), indicating minimal CoQ₁₀ absorption. Plasma levels increased gradually (Tmax ~8 h) and did not reach high concentrations. This conventional oil-based CoQ₁₀ capsule provided significantly lower systemic availability than all other formulations, suggesting that rats absorbed very little CoQ₁₀ from the softgel. 3.6. Relative Bioavailability Ranking Based on the total CoQ₁₀ exposure (AUC0-t), the relative bioavailability of the formulations is ranked as follows: G4 (Phospholipid complex) > G2 (Lipid-encapsulated) > G1 (standard) > G3 (Water-dispersible) > G5 (Softgel). In other words, the phospholipid-complexed CoQ₁₀ provided the highest bioavailability, while the commercial ubiquinone softgel was the least bioavailable. Quantitatively, the phospholipid complex yielded over 4× greater AUC than the softgel, and the lipid-encapsulated formulation was similarly close, approximately 4× higher in exposure than the softgel. The standard and water-dispersible forms of CoQ₁₀ were intermediate, with the standard slightly outperforming the water-dispersible formulation.