Natural polymers may also serve multiple roles in drug delivery as binders, disintegrants, gelling agents, stabilizers, coating materials, and matrix formers in various formulations (Sharma et al., 2019). Furthermore, their physicochemical properties (swelling, gel formation, viscosity and films) are also exceptionally advantageous in the design of sustained release (SR) systems. For oral dosage forms, natural polymers can modulate drug release through mechanisms like diffusion, erosion, or swelling-controlled transport, thereby maintaining steady plasma drug concentrations (Ngwuluka et al., 2014). In addition, their ability to mimic physiological environments enhances the wellbeing and tolerability of formulations. This review deals the some of widely studied natural polymers include: Plant-derived polysaccharides such as guar gum, xanthan gum, gum acacia, pectin, and mucilages from various plants (okra, fenugreek, plantago, hibiscus). Marine polysaccharides like alginate and carrageenan, used for gel-forming and mucoadhesive applications (Idrees et al., 2020). Animal-derived polymers such as chitosan (from chitin) and gelatin, which exhibit excellent biocompatibility and mucoadhesive properties. Microbial polysaccharides such as pullulan and dextran, offering unique viscosity and film-forming properties. These polymers not only ensure controlled release but also provide stability against harsh gastrointestinal (GI) conditions, making them highly suitable for chronic conditions requiring long-term therapy (Sung and Kim, 2020).

Natural polymers have gained prominence in modern pharmaceutics due to their ability to act as functional excipients in advanced drug delivery systems. A major function of natural polymers is in the design of controlled and extended-release systems, wherein the drug is released over an extended period of time in a controlled manner, providing a prolonged therapeutic effect while reducing the need for frequent dosing and administration (Zhao et al., 2023). This can be particularly advantageous for patients with chronic illnesses, such as diabetes mellitus, which requires adherence to a long-term treatment plan. Another important function of natural polymers is in mucoadhesion, or the ability of dosage forms to adhere to mucosal surfaces (e.g., those within the gastrointestinal tract) (Zhou et al., 2024). Developing mucoadhesive systems based on natural polymers may provide benefits for drugs with limited absorption windows or those that have short half-lives (Sonia and Sharma, 2012).

Natural polymers are also known for their relatively compatible and non-toxic properties, as they come from renewable sources found in nature, such as plants, algae, and even microbes. As natural materials, they are biodegradable, can accommodate long-term use, and can have lower risks of inducing adverse immune reactions compared to some synthetic excipients (Debotton and Dahan, 2017). At the same time, the natural source and preparation of dosing may take on even greater importance with the increasing push towards sustainability and green practice within pharmaceutical/design development.

Various natural polymers have been investigated as excipients for controlled drug delivery systems, particularly for diabetes management. Examples include: Guar gum - a galactomannan polysaccharide that swells and is viscous, which acts as a matrix former for sustained release tablets. Xanthan gum - a microbial polysaccharide that provides thickening and gel-forming properties for many controlled release formulations (Kulkarni et al., 2012). Pectin - a plant-based polysaccharide that gels, for use in colon-targeted as well as sustained release formulations. Locust bean gum - a galactomannan that exhibits a synergistic gelling property in the presence of other gums, well-suited for oral delivery (Qiu et al., 2022). Tragacanth gum - a natural gum with superior water-binding capacity, often used for suspending and controlling release. Starch derivatives - modified starches that have good film-forming and matrix-forming possibilities are flexible excipients (Ahmed and Thornalley, 2007). The benefits of these polymers is that they are renewable, regulatory acceptance as a GRAS (Generally Recognized as Safe) substance, and exhibit structural diversity for functional modifications; however, they also have challenges that they are often inherent due to employer variability in batches that exist due to environmental and geographical conditions. These natural polymers can be impacted by contaminating microorganisms during storage which could potentially restrict their use as safe excipients. Assessment of the functionality of natural polymer excipients for good pharmaceutical quality should also consider the appropriate levels of materials to standardize drug delivery action for their reproducibility.

Management of diabetes mellitus is dependent on constant and vigilant monitoring of blood glucose levels to minimize both acute and long-term complications from the disease (Ahmed and Thornalley, 2007). An example of this is with conventional immediate-release dosage forms of the drug metformin that often result in variability in drug plasma concentration resulting in peaks and doses that might risk gastrointestinal irritation. Natural polymers used in sustained release systems can minimize fluctuations and allow for a more consistent rate of drug release and more stable glycemic control (Huang et al., 2018).

In addition to their function as inert excipients, some natural polymers can themselves have synergistic or therapeutic effects in the management of diabetes. Guar gum and fenugreek mucilage, for example, have been reported to delay glucose absorption, decrease postprandial glucose spikes, and improve lipid profile (Bradley and Speight, 2002). Natural polymers also frequently exhibit antioxidant or hypoglycemic activities that can act in addition to the pharmacological effects of antidiabetic drugs. This dual effect gives them unique advantages in the development of novel and appropriate drug delivery systems to improve therapy in the management of diabetes (Currie et al., 2013).

In this regard, Hibiscus rosa-sinensis mucilage is a particularly attractive natural polymer due to its excellent swelling index, film forming ability, and general riskfree, all of which make it an appropriate natural polymer for sustained release formulations with metformin.

Hibiscus rosa-sinensis, referred to as the Chinese hibiscus, shoe flower, or China rose, is a perennial evergreen shrub that is part of the Malvaceae family. This plant is native to East Asia; however, it is cultivated as an ornamental plant throughout many tropical and subtropical areas of the world due to its large and colorful flowers (Vignesh and Nair, 2018). Apart from its aesthetic uses, this plant has long been established in traditional medicine systems (e.g., Ayurveda, Unani, Chinese medicine) to treat a variety of conditions. Hibiscus rosa-sinensis has green, shiny leaves, trumpet-shaped flowers in all colors (most commonly red), and tissues rich in mucilage (primarily the leaves and petals) (Sivaraman and Saju, 2021). Mucilage from Hibiscus rosa-sinensis is a polysaccharide complex that has demonstrated remarkable swelling, viscosity-inducing, and gel forming abilities, making it useful as a pharmaceutical excipient. In traditional medicine, different parts of Hibiscus rosa-sinensis have been used in folk medicine to treat a variety of conditions, including, wound healing - The leaves and flowers have been applied topically as a demulcent to aid in the healing of cuts, burns, and ulcers (Bala et al., 2022). Anti-inflammatory activity–Extracts of the plant are reported to reduce inflammation and pain, supporting its use in conditions such as arthritis and inflammatory skin disorders (Gunathilaka and Geeganage, 2024). Antidiabetic effects–Several studies have demonstrated the ability of Hibiscus rosa-sinensis extracts to lower blood glucose levels. Mechanisms proposed include inhibition of carbohydrate-digesting enzymes (α-amylase, α-glucosidase), improvement in insulin sensitivity, and enhancement of peripheral glucose uptake (Selvan and Ramesh, 2024). This antidiabetic potential aligns with the therapeutic goals of modern diabetes management. Other ethnomedicinal uses–The plant has also been traditionally used as an emollient, hair tonic, anti-fertility agent, and in the management of hypertension and hyperlipidemia.

Hibiscus rosa-sinensis is a valuable mucilage source from a pharmaceutical standpoint thanks to its plentiful supply, ease of preparation, and eco-friendliness (Bala et al., 2022). Essentially, the mucilage’s functional characteristics (swelling, capacity for water retention, binding action, and film-forming ability) lend themselves to usefulness for controlled and sustained release applications. Moreover, with the plant’s recognized antidiabetic potency in traditional medicine, they provide a strong rationale for examining if the mucilage can be used as an alternative natural excipient for sustained release delivery of metformin and other antidiabetic medications (Pillai and Saraswathy, 2016).

The mucilage from Hibiscus rosa-sinensis may be reliably sourced from the plant’s leaves and flowers since they have a significant amount of water-soluble polysaccharides (Ruban and Gajalakshmi, 2012). The extraction typically involves using water to extract the mucilage from the relevant plant parts, followed by the precipitation of the mucilage with organic solvents to isolate it from other constituents of the plant (e.g., chlorophyll, flavonoids, and secondary metabolites).

The mucilage derived from Hibiscus rosa-sinensis possesses several functional properties that make it excellent as a natural excipient for drug delivery systems, especially in extended-release formulations. These properties stem primarily from its polysaccharide-rich composition, which imparts unique physicochemical and biopharmaceutical advantages (Saidin et al., 2022).

Metformin is a commonly used first-line oral antihyperglycemic agent for the treatment of type 2 diabetes mellitus. While metformin has helpful efficacy, it still poses significant pharmacokinetic constraints, limiting the potential for optimal therapeutic success (Jabbour and Ziring, 2011). Metformin has an approximate plasma half-life of 4–6 h and also exhibits incomplete gastrointestinal absorption, with bioavailability ranging from 50% to 60% based on the administered drug dosage. Consequently, metformin requires multiple daily dosing (2–3 times per day), potentially impacting adherence to therapy (Donnelly et al., 2009).

Besides potential pharmacokinetic issues, metformin therapy is often accompanied by gastrointestinal (GI) adverse effects: diarrhea, nausea, bloating, and abdominal pain. These GI adverse effects are likely due to the high local concentration of metformin, which is influenced by the rapid absorption and elimination of the drug (Abbasi et al., 2024). More specifically, the adverse effects of diarrhea and other GI tract adverse effects are common and often lead to intolerability requiring discontinuation or dose reductions of metformin and ultimately reduced long-term efficacy for optimal glycemic control. Accordingly, existing rapid release metformin formulations have significant limitations for patient tolerability, adherence to metformin therapy, and sustained therapeutic activity (Hu et al., 2006).

To address these limitations, it is useful to formulate sustained release (SR) formulations of metformin. Sustained release (SR) systems change the release profile of the drug; SR profiles deliver the drug in a slow and sustained manner, resulting in stable plasma concentrations of the drug for a longer time (Jabbour and Ziring, 2011). This is beneficial as SR dosing can enable the ability to be dosed once daily per day which is important for convenience and adherence in patients with chronic illness such as diabetes (Donnelly et al., 2009).

In addition, SR metformin also improves glycemic control through the stabilization of therapeutic drug concentration and decreasing fluctuations of glucose levels in the blood which also decreases the risk of treatment failure (Tan et al., 2021).

In conclusion, sustained release metformin formulations not only address the pharmacokinetics limitations but also may have in improving the quality of life of patients and the long-term management of diabetes mellitus.

Hibiscus rosa-sinensis mucilage has unique physicochemical characteristics that support high swellability, gel forming and biocompatibility, which could be utilized to formulate a natural polymer for sustained release formulations of metformin (Panda, 2025). These properties can be utilized for different formulation strategies to achieve different drug release kinetics (Amiri et al., 2021).

The controlled release of metformin from formulations with Hibiscus rosa-sinensis mucilage, will be based primarily upon the swelling and gel-forming properties of the mucilage (Anand et al., 2017). Upon contact with gastrointestinal fluids, the mucilage will swell in water via its hydrophilic polysaccharides, forming a gel-like layer around the dosage form. This gel-like layer can then act as a diffusion barrier to slow the release of metformin from the dosage form into the surrounding medium (Gopalakrishna Murthy et al., 2023).

In addition to diffusion, the mucilage matrix will also aid in the release of drug through its erosion. The matrix erodes slowly as the polymer continues to hydrate and degrade in physiological conditions, allowing the controlled release of the encapsulated drug. This mechanism combines the swelling-controlled diffusion with erosion, yielding a more reliable and extended drug release profile (Yahaya et al., 2023). Depending upon the formulation parameters such as the mucilage concentration, cross-linking and geometry of the tablets the drug release can follow either zero-order kinetics (constant release rate) or Higuchi kinetics (drug release is proportional to the square root of time). Given the biopharmaceutical profile of metformin, the utilization of both mechanisms is highly advantageous, as it enables the sustained regulation of its plasma concentration over an extended period, thereby enhancing therapeutic efficacy (Jani and Shah, 2008).

The Figure 3, illustrates the role of Hibiscus rosa-sinensis mucilage in modulating the release kinetics of metformin through matrix formation, swelling, and gel barrier mechanisms. It also highlights its potential as a natural, biodegradable polymer offering controlled drug release, improved bioavailability, and enhanced patient compliance.

The polymeric nature of natural polymer mucilage from Hibiscus rosa-sinensis offers a number of advantages compare to standard traditional synthetic excipients for sustained release formulations: Bio-resorbable and non-toxicity: The mucilage is naturally derived meaning it is biocompatible and will be metabolized and/or excreted without concerns for related risk from long period exposure to polymers from other sources and these are very cheaper (Maitz, 2015). Renewable and patient acceptance: Assuming the polymer will originate from a plant, the mucilage is renewable and acceptable wherever patients are looking for natural, plant based, or excipient free alternatives (Hacker and Mikos, 2011).

Product bioactivity: Beyond the mucilage’s functional use as an excipient, it has been reported, the mucilage itself contains antioxidant and anti-inflammatory activity that may further benefit the patient. These bioactivities may help modulate oxidative stress and inflammation for patients with diabetes, potentially adding therapeutic value to the metformin formulation (Gunatillake et al., 2006).

Together, these benefits demonstrate the applicability of Hibiscus mucilage as both a functional excipient, and a value-added ingredient that could potentially enhance overall health outcomes in improved diabetes care (Satchanska et al., 2024).

Various obstacles exist to potential applications of Hibiscus rosa-sinensis mucilage as a sustained release formulation. These include.

One avenue to begin would be known development of polymers mixtures, whereby Hibiscus mucilage could be mixed with well-characterized synthetic polymers such as hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP), or carbopol to produce an optimal drug release profile, mechanical properties, and stability of sustained release dosage forms (Selvan and Ramesh, 2024). With careful adjustment of the ratio and properties of each synthetic and natural polymer, formulations may achieve controlled and predictable drug release, eliminating some variability inherent in using natural polymers alone (Sahu et al., 2024).

In addition to matrix tablets, Hibiscus mucilage use could be extended to a variety of advanced drug delivery systems, including microspheres, nanoparticles and a variety of mucoadhesive films. Microspheres and nanoparticles allow highly controlled drug release, enhanced absorption, and drug targeting to specific regions of the GI tract (Barus et al., 2025). Mucoadhesive films allow potentially prolonged residence time of a drug in the oral mucosa or the intestinal mucosa, which is especially useful for drugs like metformin, which have small absorption windows. The development of dosage forms using Hibiscus mucilage in these various designs may create an opportunity to extend individualized and patient-friendly diabetes control (Yahaya et al., 2023).

Additionally, to possible excipient properties, Hibiscus mucilage may elicit pharmacological properties. Evidence presented in the literature suggests that extracts of Hibiscus have anti-diabetic, antioxidant, and anti-inflammatory properties (Kapoor et al., 2021). Future formulations in developments may utilize the potential synergistic activity of the mucilage in which mucilage would act to control drug release and simultaneously to facilitate glycemia control and reduce oxidative stress activity while increasing the overall efficacy of metformin regimens (Abate and Belay, 2022).

Despite a large body of preclinical evidence for Hibiscus mucilage, clinical applications remain unrealized. A systematic and comprehensive program of preclinical and clinical research will be necessary to define reliability, efficacy, and pharmacokinetic potential of mucilage as sustained released formulations (Yasmin et al., 2023). Clinical studies to examine certain patient outcomes, tolerate, and longer-term compliance will be of necessity to parametrically introduce a commercial pharmaceutical product for the end user. In addition, regulatory standards and evidence based standardized protocols will be required for extraction of the mucilage to prepare it to become a part of diabetes therapy (Nogueira Silva Lima et al., 2022).

Natural Excipients such as Hibiscus rosa-sinensis mucilage have the potential for safe and sustainable pharmaceutical delivery but must adhere to regulatory guidelines (e.g., FDA/EMA) for safety, quality, and reproducibility in order to gain greater use. To meet this challenge, it will be necessary to develop standardized methods for extracting, purifying, and characterizing natural excipients as well as develop pharmacopoeia monographs to ensure that the functional properties of each natural excipient are consistent from one batch to the next and that they may be used to create commercial pharmaceutical preparations (Kavoosi et al., 2025; Amin et al., 2023).

In conclusion, the potential of Hibiscus rosa-sinensis mucilage to be formulated for drug delivery will largely depend on the methods of formulating mucilage with contemporary formulation techniques, the delivery of the mucilage in novel dosage forms, as well as comprehensive clinical studies for human subjects (Saeed et al., 2025; Nguyen et al., 2025). The future of Hibiscus rosa-sinensis mucilage is to utilize the unique functional capabilities of natural polymers through their effects and properties that can provide sustained release of a therapy that is safe, effective, and patients friendly for managing diabetes (Amin et al., 2023; Amin et al., 2022). The detail future prospective were depicted in Figure 4.