Formulation and Physicochemical Evaluation of an Alcohol-Free Effervescent Herbal Mouthwash Tablet Incorporating Ocimum sanctum and Syzygium aromaticum

Good oral hygiene practice is essential for avoiding dental caries, gingivitis, and periodontal disease. Despite their clinical effectiveness, liquid-based mouthwashes exhibit certain pharmacologic and environmental limitations. The common commercial formulation for liquid mouthwash contains ethanol in a percentage of up to 25%, which has been known to cause xerostomia, mucosal desquamation, and burning sensation [19]. In addition, the need for liquid aqueous solution globally leads to high plastic use, leading to environmental pollution.Effervescent solid tablets represent an extremely novel approach [12]. Effervescent compounds involve a chemical interaction between soluble organic acids like citric and tartaric acids and alkali metal carbonate salts, such as sodium bicarbonate[13].The rapid formation of carbon dioxide gas occurs through a stoichiometric process in the presence of water.

The instant breakdown eliminates any necessity for mechanical mixing and ensures that a freshly prepared solution is available for use [17]. 

Crude powder formulations of Ocimum sanctum (tulsi) and Syzygium aromaticum (clove) were considered for their therapeutic value. Tulsi contains a significant quantity of ursolic acid and eugenol that possess a wide spectrum of antibacterial activity for oral plaque biofilms, without the staining effect caused by chlorhexidine [1,5,15]. Cloves exhibit excellent anesthetic and antifungal properties [7,9].

The current research work is concerned with improving the physicochemical properties of the raw plant powders through the modification of binders and water soluble lubricants. The purpose of this is to make raw plant fibers suitable for tablet compression by controlling the inherent elastic nature of plant fibers, thereby formulating an oral rinse preparation [2,11].

3. MATERIALS AND METHODS

3.1 Materials

The plant powder of Ocimum sanctum and Syzygium aromaticum was obtained from a botanical material vendor and sieved using mesh no. 120. The chemical compounds used included sodium bicarbonate, citric acid anhydrous, tartaric acid, polyvinylpyrrolidone K-30, PEG 6000, sorbitol, and peppermint flavoring agent [20].

3.2 Formulation Design and Optimization Strategy

A series of three experimental batches (F1–F3) were optimized to overcome the capping and sticking tendencies associated with elastic botanical fibers. Formulations were compressed using 200 mg tooling on a rotary press, with batch sizes fixed at 15 tablets (3000 mg total). The study prioritized varying the ratios of PVP K-30 and PEG 6000, utilizing sorbitol as a filler to ensure consistent weight across all variables [11].

• Batch F1: Low Binder (2%) / Low Lubricant (1%)
• Batch F2: Standard Binder (5%) / Standard Lubricant (2%)
• Batch F3: High Binder (8%) / High Lubricant (4%)

3.3 Formulation Table

Target Tablet Weight: 200 mg | Batch Size: 15 Tablets | Method: Direct

Compression

3.4 Manufacturing Procedure (Direct Compression)

Table 1: Pre-Compression Parameters of Batches F1 - F3

Parameter	F1 (Low Binder/ Lube)	F2 (Standard/ Optimized)	F3 (High Binder/ Lube)
Angle of Repose (θ)	29.4° (Good)	27.8° (Excellent)	33.2° (Passable/ Sticky)
Bulk Density (g/mL)	0.52	0.55	0.48
Tapped Density (g/mL)	0.62	0.64	0.6
Carr's Index (%)	16.12%	14.06%	20.00%
Hausner Ratio	1.19	1.16	1.25

5.2 Post-Compression Physicochemical Properties

Table 2: Comparative Post-Compression Evaluation

Parameter	Limit/ Ideal	F1	F2 (Optimized)	F3
Average Weight (mg)	200 mg	198.5 mg	201.2 mg	197.8 mg
Weight Variation (%)	± 7.5%	3.1%	1.8%	4.2%
Hardness (kg/cm²)	3.0 - 4.0	2.2	3.6	5.4
Friability (%)	< 1.0%	1.85%	0.62%	0.28%
Effervescence Time (sec)	< 180 sec	32 sec	88 sec	92 sec
Solution pH	6.0 - 7.0	6.42	6.45	6.51
Visual Solution Clarity	Suspension	Rapid dispersion	Uniform fine suspension	Slow, clumpy

Fig 1: effervescence time testing of the optimized tablet (batch F2) in 15ml of purified water

Discussion of Physicochemical Optimization:

Fig (A)                                                Fig (B)

Figure 2. Physical characteristics of directly compressed herbal effervescent tablets. (Left) Batch F1 prepared with low amount of binder (2% PVP K-30), exhibiting surface capping and edge degradation due to the stiff elasticity of the raw botanical fibers. (Right)  The optimized Batch F2, prepared with higher binder content (5% PVP K-30), showed excellent structural integrity with smooth edges and no capping defects.

The variable study successfully established the mechanical boundaries of the effervescent system containing raw botanical fibers. Batch F1 (2% PVP K-30) failed friability testing (1.85%) and exhibited insufficient hardness (2.2 kg/cm²), demonstrating that elastic plant fibers require a robust polymeric binder to prevent capping and structural failure [2]. Batch F3 the high concentration of PEG 6000 created a hydrophobic barrier that prevented the aqueous medium from penetrating the tablet and reacting with the effervescent base [11].

Batch F2 was the scientifically optimized formulation. The 5% binder concentration was able to trap the elastic plant fibers in a stable matrix (0.62% friability) and the 2% PEG 6000 prevented the eugenol rich clove powder from sticking to the punches of the machine. The generation of a physiologically compatible pH of 6.45 yielded an ideal effervescence time of 88 s.

Figure 3: Final packaging of optimized herbal effervescent mouthwash formulation (Batch F2) in moisture resistant amber glass bottle

6. CONCLUSION

In this study, alcohol free solid dosage herbal effervescent mouthwash has been successfully prepared by direct compression. Critical structure requirement for compression of elastic botanical crude powders without capping or punchsticking was revealed by factorial optimization as 5% PVP K-30 and 2% PEG 6000 matrix (Batch F2). The optimized formulation exhibited excellent precompression flowability, ideal post-compression mechanical strength and fast effervescence time (88 s). Batch F2 shows a very stable, green and physically robust solid-dose alternative to conventional liquid oral rinses by substituting liquid ethanol with an anhydrous stoichiometric effervescent mix.

ACKNOWLEDGEMENT

We express our sincere gratitude to our respected guide, Dr. M. M. Nitalikar, for their invaluable guidance, constant encouragement, and insightful suggestions throughout the course of this project. Their expertise and support played a crucial role in the successful completion of this research work.

We would also like to extend my heartfelt thanks to our respected Principal ,   Dr. S. K. Mohite, for providing the necessary facilities, resources, and a conducive academic environment at Rajarambapu College of Pharmacy that enabled us to carry out this study effectively.

We are deeply thankful to all the teaching and non-teaching staff of the institution for their cooperation and assistance whenever required.

Finally, we would like to acknowledge our family and friends for their continuous motivation and support throughout this work.

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