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Department of Pharmacy, SND Institute of Pharmacy, Babhulgaon, Yeola, Maharashtra, India.
Reactive oxygen species (ROS) are a common trigger for skin aging, which is caused by both intrinsic (chronological) processes and external causes including UV radiation and pollution. Excess ROS cause wrinkles, dryness, and loss of elasticity by damaging lipids, proteins, and DNA, upregulating matrix metalloproteinases (MMPs), and degrading dermal collagen and elastin [11–20]. The shoe flower or China rose, Hibiscus rosa-sinensis Linn. (Malvaceae), is a commonly available plant whose flowers and leaves include flavonoids, anthocyanins, phenolic compounds, mucilage, vitamins, and sterols [1-3]. Plant polyphenols are appealing topical antioxidants. In experiments, plant extracts exhibit antioxidant, anti-inflammatory, wound-healing, antibacterial, and hair-growth properties [7–10]. Water-rich, non-greasy, and esthetically pleasing, hydrogels can contain hydrophilic plant extracts and moisturize the skin [25–29]. The botany, phytochemistry, and antioxidant pharmacology of H. rosa-sinensis, the biology of skin aging, the principles of hydrogel production, and the assessment criteria pertinent to a leaf plus flower extract hydrogel are all summarized in this paper. The motivation for the current endeavor is supported by the fact that no study that particularly creates a combined leaf and flower extract hydrogel for anti-aging usage was found in the reviewed literature.
Figure 1: Human Skin
The skin, being the outermost layer of the body, is continuously exposed to oxidants from both internal metabolism and the environment. Skin has been utilized as a standard model to study the connection between oxidative stress and aging since Harman's free radical theory proposed that ROS buildup is a significant driver of aging [11,15]. Consumer interest in natural, plant-based cosmeceuticals has grown since they are believed to be safer and are often high in polyphenols that may enhance the skin's natural antioxidant defenses [14,21,24].
An successful topical antioxidant requires three things: a source of active compounds, a delivery strategy that enables them to reach the skin while preserving their stability, and a suitable evaluation to show their quality and performance. H. rosa-sinensis is inexpensive, readily accessible, and has a long history of traditional use in India [4-6]. Spreadable, cooling, and suitable for aqueous extracts are hydrogels composed of polymers such xanthan gum, Carbopol, or HPMC [25, 29]. This article's goal is to combine these three components and provide a logical method for creating and assessing a hydrogel made from Hibiscus leaf and flower extract.
2. Botany and Traditional Uses of Hibiscus rosa-sinensis
Originally from East Asia, H. rosa-sinensis is an evergreen flowering shrub in the Malvaceae family that is grown as a decorative and therapeutic plant in tropical and subtropical areas [1, 3]. Shoe flower, China rose, Japa, and Rudrapushpa are common names. Wounds, inflammation, fever, cough, diabetes, infections, hair loss, and stomach diseases have all been treated with various parts in traditional medicine [1,4-6]. Additionally, flowers are utilized as a natural colorant and in hair oils, which suggests a cosmetic function.
Figure 1: Hibiscus rosa-sinensis
2.1 Taxonomy and Morphology
Table 1: Taxonomical Classification
| Rank | Classification |
|---|---|
| Kingdom | Plantae |
| Order | Malvales |
| Family | Malvaceae |
| Genus | Hibiscus |
| Species | Hibiscus rosa-sinensis L. |
The plant is a woody shrub with branches that grows to a height of one to three meters. Its simple, alternating, oval leaves have toothed margins. The flowers have five petals, a conspicuous staminal column, and are big, showy, and funnel-shaped. Although varieties vary from white and yellow to pink and orange, red is the most common color [1,3]. The cultivar and color utilized in the project should always be noted because flower color affects pigment and antioxidant content [7].
3. Phytochemistry
There are bioactive substances in every section of the plant. Flavonoids, tannins, terpenoids, anthocyanins, saponins, cyclopeptide alkaloids, and vitamins are reported in reviews [1-3].
Table 2: Phytochemicals Present in Hibiscus rosa-sinensis
| Plant part | Reported constituents | Relevance to anti-aging |
|---|---|---|
| Flower | Ascorbic acid, thiamin, riboflavin, flavonols (quercetin-3-diglucoside, quercetin-3,7-diglucoside, kaempferol glycosides), anthocyanins (cyanidin-3,5-diglucoside, cyanidin-3-sophoroside-5-glucoside) and mucilage [2,3,7] | UV absorption, metal chelation, radicalscavenging, film formation, and moisturizing mucilage |
| Leaf | Alkaloids, phenolics, mucilage, sterols, glycosides, reducing sugars, and resin [1-3,7] | Hydrating polysaccharides and additional phenolic antioxidants |
| Stem and root | sterculic and malvalic acids, beta-sitosterol, taraxeryl acetate, saponins, and tannins [1,2]. | Not utilized in the current formulation |
Cultivar, flower color, season, solvent, and extraction method all affect the phenolic and anthocyanin content [7,35]. When the extract is put in a gel with a pH that is almost neutral, it matters because anthocyanins are sensitive to temperature and pH and break down at higher pH and heat [34]. It is therefore advised to standardize using total phenolic content (Folin-Ciocalteu) [39], total flavonoid content (aluminum chloride technique) [40], and total anthocyanin content (pH-differential method) [41].
3.1 Antioxidant chemistry of the main constituent classes
Table 3: Antioxidant Chemistry of the Main Constituent Classes
| Class | Why it scavenges radicals | Practical point |
|---|---|---|
| Flavonols (quercetin and kaempferol glycosides) | The radical that results from phenolic -OH groups donating an electron or hydrogen atom is stabilized by delocalization; quercetin's catechol group additionally chelates copper and iron [20,34]. | Although they dissolve easily in water, glycosides are less able to penetrate skin than aglycones [32]. |
| Anthocyanins (cyanidin glycosides) | The resultant radical can be stabilized and given electrons by the conjugated phenolic ring system [34]. | They are most stable in acidic conditions, and their color and stability vary with pH [34]. |
| Phenolic acids and tannins | Each molecule has several hydroxyl groups. | Add astringency; some polymers and proteins may be bound. |
| Ascorbic acid and other vitamins | reducing agents that support the regeneration of more antioxidants [14] | Sensitive to heat and oxygen |
3.2 Choice of solvent
What is extracted depends on the polarity of the solvent. Water yields higher mucilage and anthocyanin-rich fractions, but ethanol and hydroalcoholic combinations typically recover more phenolics and flavonoids [1,35]. An aqueous or hydroalcoholic extract (with the alcohol completely eliminated) is more useful than a non-polar one since the dried extract must disperse in water for a hydrogel. Comparing two solvents is a helpful experiment because hawthorn hydrogels generated with ethanolic extracts shown more antioxidant activity than aqueous ones in most experiments [50].
4. Antioxidant Activity of H. rosa-sinensis
Free radicals are scavenged by flower and leaf extracts, according to several in vitro investigations. examined extracts from hibiscus and cassia flowers and connected their phenolic content to antibacterial and antioxidant properties [7]. According to other research, ethanolic flower extracts suppress hydroxyl radicals and lipid peroxidation, flavonoids extracted from the petals exhibit antioxidant action, and a 70% ethanol leaf extract protects proteins and lipids from oxidative damage [1,2,3,7]. Additionally, reviews point out that aqueous extracts contain more mucilage and anthocyanins, but ethanol and methanol typically extract more phenolics than water [1,35].
The common in vitro methods used to quantify antioxidant capacity are summarised below.
Table 4: Antioxidant Activity of H. rosa-sinensis
| Assay | Principle | Reference |
|---|---|---|
| DPPH | Hydrogen/electron donation decolourises the purple DPPH radical (about 517 nm) | [36] |
| ABTS | Reduction of the pre-formed ABTS radical cation | [37] |
| FRAP | Reduction of Fe(III)-TPTZ to Fe(II) at low pH | [38] |
| Total phenolics | Folin-Ciocalteu reduction | [39] |
| Total flavonoids | AlCl3 complexation | [40] |
5. Skin Aging and Oxidative Stress
The term "skin aging exposome" refers to both the intrinsic (genetic, hormonal, and cellular senescence) and extrinsic (mostly caused by UV light, smoking, and pollution) components of skin aging [17,18]. ROS are produced by both mechanisms through photochemical processes, NADPH oxidases, and mitochondria [15]. In addition to decreasing collagen production, ROS stimulate signaling pathways (AP-1, NF-kB) that increase MMP-1, MMP-3, and MMP-9, which break down type I and III collagen and cause fine and coarse wrinkles, loss of firmness, and compromised barrier function [12,13]. Damage is exacerbated by lipid peroxidation, inflammation, and advanced glycation end products [13,15,16].
Topical antioxidants can mitigate UV-induced inflammation, neutralize ROS, and indirectly shield the extracellular matrix [14,19,20]. As indicators of anti-aging potential, natural products have been tested for antioxidant activity, anti-collagenase, and anti-elastase [21–23]. Recent studies emphasize that plant-derived compounds have anti-inflammatory, barrier-supporting, ROS-neutralizing, and MMP-inhibiting actions, and that delivery technique is just as crucial as the active ingredient [55].
5.1 Molecular pathways
Increased ROS from UV exposure and mitochondrial activity trigger transcription factors AP-1 and NF-kB as well as mitogen-activated protein kinase (MAPK) cascades. Collagen is produced more slowly and broken down more quickly as a result of AP-1's interference with TGF-beta/Smad signaling and upregulation of MMP-1, MMP-3, and MMP-9 [12,13]. The enzymatic defenses of the skin, such as glutathione peroxidase, catalase, and superoxide dismutase, also deteriorate with age [15,19].
Table 5: Molecular Pathways
| Aging change | Visible sign | Where an antioxidant gel could help |
|---|---|---|
| ROS rise, lipid peroxidation | Dullness, roughness | Scavenging at the skin surface [14,20] |
| MMP activation, collagen loss | Wrinkles, sagging | Indirect, by lowering ROS-driven MMP signalling [12,13] |
| Chronic low-grade inflammation | Redness, uneven tone | Anti-inflammatory polyphenols [20,55] |
| Water loss from the skin | Dryness, flaking | Water content of the gel, humectants, mucilage [1,25] |
| UV damage | Photoaging, pigmentation | UV-absorbing polyphenols, as an adjunct only and not a sunscreen replacement [20,53] |
6. Anti-Aging Relevance of Hibiscus Constituents
The "anti-aging" claim for the formulation is best framed as antioxidant-based unless additional assays are included because direct experimental evidence on collagenase, elastase, or MMP inhibition by H. rosa-sinensis are sparse in comparison to its antioxidant findings [21–23].
6.1 Mechanistic hypothesis and evidence status
Table 6: Mechanistic Hypothesis and Evidence Status
| Proposed action | Likely constituents | Evidence status |
|---|---|---|
| Direct ROS scavenging | Anthocyanins, flavonols, phenolics | Reported for H. rosa-sinensis extracts in vitro [1,3,7] |
| Metal chelation | Catechol-type flavonoids such as quercetin | General flavonoid chemistry [34]; not tested for this plant in the sources reviewed |
| Protection from UV-induced oxidation | Flavonols | Shown for quercetin formulations [33]; UV absorbance of a Hibiscus gel reported [53] |
| Collagenase and elastase inhibition | Polyphenols, tannins | Suggested by studies of other plants [21-23]; to be tested for Hibiscus |
| Hydration and barrier support | Mucilage, humectants, gel water | Plausible [1,25]; can be measured by corneometry |
This table keeps the review correct by separating reported data for H. rosa-sinensis from extrapolated data. It also highlights areas where your experiments can yield additional information.
7. Hydrogels as Topical Carriers
Large volumes of water can be stored in three-dimensional hydrophilic polymer networks called hydrogels [25, 26]. They provide a cooling effect, hydration, ease of washing, patient acceptance, minimal discomfort, and compatibility with water-soluble extracts when applied topically [27, 28]. Poor lipophilic chemical solubilization and the possibility of microbiological growth necessitate the use of a preservative.
Table 7: Hydrogels as Topical Carriers
| Component | Examples | Function |
|---|---|---|
| Gelling agent | Carbopol 934/940, HPMC, xanthan gum, sodium CMC, chitosan | Forms the network; controls viscosity and release [25,28,29] |
| Neutraliser | Triethanolamine, NaOH | Ionises Carbopol to give a clear gel [29] |
| Humectant / penetration aid | Glycerin, propylene glycol | Moisturising; retains water; helps spreadability |
| Preservative | Methylparaben, propylparaben | Prevents microbial growth |
After neutralization to a pH of roughly 6-7, carbopol, a cross-linked polyacrylic acid, swells and thickens; its rheology is dependent on this pH [29]. The final gel pH is often regulated near 5-6.5 to prevent irritation and keep anthocyanins reasonably stable because the skin's surface is rather acidic [34].
7.1 Choice of gelling agent
Table 8: Gelling Agents
| Polymer | Key properties | Cautions |
|---|---|---|
| Carbopol 934 / 940 (carbomer) | Clear gel, high viscosity at low concentration, good spreadability after neutralisation [29] | Electrolytes and acidic extract components can thin the gel; needs pH adjustment |
| HPMC | Non-ionic, stable over a wide pH range, film-forming | Slow to hydrate; needs hot-water dispersion |
| Xanthan gum | Shear-thinning, tolerant of salts | Can feel stringy; supports microbial growth |
| Sodium CMC | Low cost, anionic | Viscosity falls at low pH and with salts |
| Chitosan | Cationic, mucoadhesive, mildly antimicrobial | Needs dilute acid; may interact with anionic extract components |
skin sensation and rheology [25, 28, 48, 51]. Trial batches should determine whether the hibiscus extract reduces the viscosity of Carbopol at the selected pH because it contains mucilage and acidic pigments.
8. Formulation Approach for a Leaf and Flower Extract Hydrogel
8.1 Collection and authentication
Fresh flowers and leaves are gathered, verified by a botanist, cleaned, shade-dried, and ground into powder. Standard procedures are used to determine pharmacognostic standards like foreign matter, ash values, and extractive values [47].
8.2 Extraction
Ethanol, hydroalcoholic, or aqueous solvents are frequently used in maceration or Soxhlet extraction, and contemporary methods (aided by microwaves or ultrasound) can increase yield and reduce time [35]. The dry extract is kept in a cool, dark, airtight container after the solvent is evaporated under low pressure. For both leaf and flower extracts, preliminary phytochemical testing and TPC/TFC estimation should be documented [39, 40].
8.3 Preparation of the hydrogel
1. Add the gelling agent (such as Carbopol 940) to a portion of the water and let it swell for a few hours.
2. In the leftover water or glycol, dissolve the humectant and preservative.
3. Gently swirl the leaf and floral extracts into the swollen polymer after dissolving them in a tiny amount of the aqueous solution.
4. Make up to weight and use triethanolamine to adjust the pH to the appropriate level.
Illustrative starting ranges (to be optimised by trial batches; they are not fixed recommendations):
Table 9: Ingredients for Hydrogel Preparation
| Ingredient | Typical range explored |
|---|---|
| Leaf + flower extract | 0.5-5% w/w (several levels, for example 1, 2 and 3%, with a blank) |
| Carbopol 940 | 0.5-1.5% w/w (about 1% gave optimal consistency in a hawthorn hydrogel [50]; 1.5% was used in a Centella-Moringa emulgel [52]) |
| Glycerin / propylene glycol | 5-15% w/w |
| Triethanolamine | q.s. to pH 5.5-6.5 |
| Methylparaben | 0.1-0.2% w/w |
8.4 Suggested batch plan
A simple design compares each extract alone with the combination, plus a blank.
Table 10: Batch Plan
| Batch | Leaf extract | Flower extract | Purpose |
|---|---|---|---|
| F0 | none | none | Blank gel (control) |
| F1 | 1% | none | Leaf only |
| F2 | none | 1% | Flower only |
| F3 | 0.5% | 0.5% | Combination at 1% total |
| F4 | 1% | 1% | Combination at 2% total |
| F5 | 1.5% | 1.5% | Combination at 3% total |
The percentages serve as examples; following a trial run, determine the final levels based on color, pH, and DPPH readings. A reasonable check for synergy is provided by comparing F1, F2, and F3 (equal total extract).
8.5 Common formulation problems
Table 11: Arising Formulation Problems
| Problem | Probable cause | Possible remedy |
|---|---|---|
| Lumps (fish-eyes) | Carbopol added too fast | Sprinkle slowly into a vortex and let it swell overnight |
| Thin gel after adding extract | Electrolytes or acids lower viscosity | Re-adjust pH; raise polymer level; add HPMC or xanthan gum |
| Colour fades or browns | Anthocyanin breakdown by pH, light or heat | Keep pH near 5.5; use opaque packaging; consider a chelator or antioxidant [34] |
| Turbidity or sediment | Insoluble extract fraction | Filter the extract; remove all alcohol from hydroalcoholic extract |
| Microbial growth | Aqueous base plus plant material | Use a preservative; run a microbial limit test |
9. Evaluation of the Hydrogel
Table 12: Evaluation Parameters of the Hydrogels
| Parameter | Method / purpose | Notes |
|---|---|---|
| Organoleptic | Colour, odour, appearance, homogeneity | Anthocyanin colour change can signal degradation [34] |
| pH | Digital pH meter (1% dispersion) | Target near skin pH; a herbal hydrogel stayed at 5.5-6.5 over 90 days [50] |
| Viscosity and rheology | Brookfield viscometer | Shear-thinning flow is desirable [29] |
| Spreadability and extrudability | Parallel-plate method; tube extrusion | Patient acceptance and dose uniformity [51] |
| Extract content | Marker such as TPC or TFC | Assures uniformity [39,40] |
| Antioxidant activity of the finished gel | DPPH, ABTS, FRAP versus extract and blank gel | Confirms the extract remains active after formulation [36-38,50] |
| In vitro release / permeation | Franz diffusion cell with a synthetic or animal membrane | Release kinetics fitted to Higuchi and Korsmeyer-Peppas models [44-46] |
| Skin irritation | Primary irritation index (Draize-type), or human volunteers with ethical approval | Safety for topical use [42,49] |
| Stability | ICH Q1A(R2) conditions, for example 40 C / 75% RH, plus room temperature and refrigerated | Observe pH, viscosity, colour and antioxidant activity [43] |
| Microbial limit | Total viable count | Quality control |
9.1 Method notes
Table 13: An Overview of Published Herbal Gel and Hydrogel Research
| Plant | Base | Evaluations reported |
|---|---|---|
| Oenanthe javanica [48] | Carbopol, HPMC, xanthan gum, glycerin | pH, appearance, rheology, volunteer smoothness rating |
| Gac fruit [49] | Carbopol 940 | Physical properties, DPPH, skin irritation in volunteers |
| Hawthorn [50] | Carbopol 940 (1%) | pH over 90 days, TBARS, beta-carotene bleaching, DPPH, reducing power |
| Centella asiatica madecassoside [51] | Carbopol 940, HPMC | Spreadability, rheology, antimicrobial and antioxidant activity |
| Centella plus Moringa [52] | Carbopol emulgel with stearic acid | Organoleptic, physical quality, DPPH |
11. Challenges and Future Perspectives
CONCLUSION
Hydrogels are an appropriate, patient-friendly carrier for the abundant, readily available polyphenols with proven antioxidant action found in H. rosa-sinensis leaves and flowers. A standardized leaf and flower extract hydrogel makes sense as an anti-aging option because oxidative stress is closely associated with skin aging. A good project should standardize the extracts, optimize the gel base, assess stability, irritation, and physicochemical characteristics, and show antioxidant activity in the finished product. Since there is now insufficient direct evidence for integrated leaf and flower hydrogels, this is a promising subject for future research.
REFERENCES
Zeenat Shaikh, Bharat Pawar, Pratik More, Sayali Sonawane, Formulation and Evaluation of Hibiscus Rosa-Sinensis Leaf and Flower Extract Hydrogel for Antioxidant & Anti-Aging Potential: A Review, Int. J. of Pharm. Sci., 2026, Vol 4, Issue 11, 1909-1920. https://doi.org/10.5281/zenodo.24155466
10.5281/zenodo.24155466