Characterization, Antioxidant Capacity, and In Vitro Bioaccessibility of Ginger (Zingiber officinale Roscoe) in Different Pharmaceutical Formulations

Abstract

Ginger (Zingiber officinale Roscoe) has been widely recognized for its antioxidant properties, primarily attributed to its phenolic compounds such as gingerols and shogaols. However, limited data exist regarding how different pharmaceutical forms influence the bioaccessibility and antioxidant efficacy of these compounds. This study aimed to evaluate the antioxidant capacity and bioaccessibility of ginger in different pharmaceutical forms—capsules (20 mg, 40 mg, and 80 mg), a pure powdered extract, and a liquid formulation—standardized to ≥6% gingerols. The phenolic profile of each formulation was characterized using HPLC-DAD (High-Performance Liquid Chromatography with Diode Array Detection), followed by the evaluation of antioxidant capacity through DPPH (2,2-Diphenyl-1-picrylhydrazyl) and ORAC (Oxygen Radical Absorbance Capacity) assays, and the assessment of bioaccessibility via an in vitro digestion model. The results demonstrated that antioxidant activity was positively correlated with extract concentration and was highest in the liquid formulation (426.0 ± 0.05 µmol Trolox equivalents (TE) and 11,336.7 ± 0.20 µmol TE in the DPPH and ORAC assays, respectively). The bioaccessibility of 6-gingerol and 6-shogaol significantly increased in the liquid form, reaching 23.44% and 11.31%, respectively, compared to ≤4% in the pure extract. These findings highlight the influence of the formulation matrix on compound release and support the use of liquid preparations to enhance the functional efficacy of ginger-derived nutraceuticals. This standardized comparative approach, using formulations derived from the same extract, offers new insights into how the delivery matrix influences the functional performance of ginger compounds, providing guidance for the development of more effective nutraceutical strategies.

Introduction

Oxidative stress is produced by an imbalance between the production of reactive oxygen species (ROS) and the ability to counteract them through antioxidant mechanisms [1,2,3]. This imbalance may be caused by insufficient antioxidant intake, the depletion of endogenous antioxidants, or an increase in ROS production [1,2]. ROS are molecules containing highly reactive oxygen; the most common examples include hydrogen peroxide (H2O2), superoxide (O2·) and the hydroxyl radical (OH·), the most reactive ROS species [1]. ROS are involved in essential processes in the organism, such as cellular homeostasis, gene expression, receptor activation, and signal transduction [2]. An increase in ROS production could lead to harmful effects in vital cellular structures including proteins, lipids, and nucleic acids, leading to the development of different pathological conditions that affect human health [2,3,4].

The onset of disease is closely related to cellular oxidation levels, highlighting the importance of including foods in the diet that can prevent oxidative stress [1,2,3]. Evidence from previous studies and clinical trials suggests that supplementation with phytochemicals, such as those found in Zingiber officinale, can decelerate cellular degradation linked to redox imbalances [5,6,7]. Ginger (Zingiber officinale Roscoe) is a perennial herb member of the Zingiberaceae family that is among the most active natural remedies due to its numerous biological properties [4]. The rhizome of Zingiber officinale has been used in traditional medicine for the treatment of various conditions and is composed mostly of phenolic compounds, with gingerols (6-gingerol, 8-gingerol, and 10-gingerol), shogaols (6-shogaol, 8-shogaol, and 10-shogaol), and flavonoids standing out for their antioxidant bioactivity [5,7,8,9]. These bioactive compounds exhibit their antioxidative capacity primarily through their chemical structure, characterized by multiple hydroxyl groups attached to an aromatic ring, enabling them to neutralize free radicals or chelate metal ions, thereby reducing oxidative stress [7,10].

Among the bioactive compounds present in Zingiber officinale, 6-shogaol and specially 6-gingerol exhibits significant in vitro antioxidant capacity [8,11]. The mechanism involved in its antioxidant capacity is related to the prevention of free radicals as well as to its ability to scavenge them [2,7]. The most recent scientific literature has shown that 6-gingerol potentiates Beclin-1 expression favoring autophagy in human endothelial cells and interferes with PI3K/AKT/mTOR pathway signaling without altering the cell cycle [2]. Different studies have shown that 6-gingerol can effectively inhibit xanthine oxidase (XO), an enzyme responsible for catalyzing the oxidation of hypoxanthine to xanthine and xanthine to uric acid, preventing the production of ROS in the last stage of metabolic degradation of purines [8]. Additionally, 6-gingerol has been reported to enhance the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and decrease the level of malondialdehyde (MDA), a marker of lipid peroxidation. In other research, 6-shogaol has been shown to exhibit antioxidant capacity through activation of the nuclear factor erythroid 2 (Nrf2) signaling pathway [12,13,14]. Thus, Zingiber officinale extract can regulate lipogenesis, fatty acid oxidation, mitochondrial dysfunction, and oxidative stress, conferring various biological properties, including anticancer, antimicrobial, anti-inflammatory, and antiallergic effects.

The effective dose of Zingiber officinale and the length of the administration to observe antioxidant capacity varies widely between different in vitro and in vivo studies. Daily supplementation with 1 g of ginger for up to 3 months has been shown to reduce serum nitric oxide levels and inhibit the expression of inducible nitric oxide synthase (iNOS) in immune cells, highlighting its potential role in modulating oxidative stress and inflammatory pathways [12,15]. However, the clinical translation of these findings depends not only on the activity of isolated compounds, but also on their stability, release, and absorption in real-world formulations.

Moreover, the formulation matrix plays a critical role in the protection, solubility, and biological activity of phenolic compounds such as gingerols and shogaols. Unlike specialized encapsulation technologies, conventional dosage forms like powders, capsules, or liquid solutions can modulate the stability, antioxidant capacity, and bioaccessibility of these compounds depending on the physicochemical environment they create. In this context, the liquid formulation demonstrated superior performance not only in preserving the integrity and enhancing the bioaccessibility of 6-gingerol and 6-shogaol during digestion but also in maintaining their antioxidant potential, highlighting the relevance of formulation design in maximizing the functional efficacy of ginger-derived nutraceuticals.

Despite the extensive evidence supporting the antioxidant capacity of Zingiber officinale and its bioactive constituents, there is limited information regarding how different pharmaceutical formulations influence its stability, solubility, and bioaccessibility under gastrointestinal conditions [16]. Most studies have focused on raw extracts or isolated compounds, overlooking the potential modifications induced by delivery systems such as capsules or liquid suspensions. These formulations may alter the release profile, protection from degradation, and ultimately the biological activity of ginger-derived compounds [17]. To address this gap, our study uses a controlled experimental design where all formulations are based on a single standardized extract of Zingiber officinale, allowing us to isolate the effect of the delivery matrix on antioxidant capacity and compound bioaccessibility. This approach offers a novel perspective by integrating in vitro digestion and antioxidant assessment under physiologically relevant conditions.

Therefore, it is essential to assess not only the antioxidant capacity of Zingiber officinale in various dosage forms, but also to understand how these formulations affect its chemical integrity and intestinal availability after digestion. By comparing different formulations, it is possible to determine the most efficient delivery system for maximizing antioxidant potential and enhancing the bioaccessibility of functional phytochemicals.

The use of nutraceuticals may serve as an adjuvant treatment for oxidative stress-related diseases, including neurodegenerative, cardiovascular, autoimmune, and inflammatory disorders [5]. In this context, the aim of this study is to evaluate the in vitro antioxidant capacity of ginger extract and capsules at different concentrations (20 mg, 40 mg, and 80 mg), as well as a liquid formulation containing Zingiber officinale (1000 mg of extract in 300 mL), using the oxygen radical absorbance capacity (ORAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods [18,19,20], and comparing the results obtained with different solvents. Additionally, the stability and bioaccessibility of pure ginger extract and the liquid formulation will be assessed after an in vitro digestion process. Prior to these analyses, a qualitative and quantitative characterization of the ginger extract and its different pharmaceutical formulations will be conducted using high-performance liquid chromatography with diode array detection (HPLC-DAD). Therefore, these results will provide a basis for future research aimed at evaluating the in vivo bioavailability of these compounds and determining the optimal concentrations to achieve antioxidant effects in the body.

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Materials and Methods

Source: Plana, L.; Marhuenda, J.; Arcusa, R.; García-Muñoz, A.M.; Ballester, P.; Cerdá, B.; Victoria-Montesinos, D.; Zafrilla, P. Characterization, Antioxidant Capacity, and In Vitro Bioaccessibility of Ginger (Zingiber officinale Roscoe) in Different Pharmaceutical Formulations. Antioxidants 2025, 14, 873. https://doi.org/10.3390/antiox14070873