Guava Leaf Extract as a Sustainable Preservative Alternative in Semi-Solid Pharmaceuticals: Efficacy and Stability Assessment

Abstract

Background: Natural alternatives are becoming more popular as a result of health risks associated with synthetic preservatives in pharmaceuticals. Because of its antibacterial properties, Psidium guajava (L.) leaf extract is a practical choice for sustainable preservation.

Objectives: The aim of this research is to evaluate the efficacy of Psidium guajava (L.) leaf extract as a 10% (w/w) natural preservative in five different base formulations: creams (clotrimazole cream, permethrin cream, and gentamicin cream) and gels (indomethacin emulgel and ibuprofen gel).

Methods: Over the course of 28 days, antimicrobial activity against Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Aspergillus brasiliensis, and Candida albicans was evaluated. In accordance with USP/BP guidelines, three months of accelerated conditions (40 ± 2 °C/75% ± 5% RH) were used to assess chemical, physical, and microbiological stability. The stability of the active component was examined using HPLC.

Results: Our findings showed that the extract completely inhibited the growth of tested bacterial species in clotrimazole cream, permethrin cream, gentamicin cream, and indomethacin emulgel, demonstrating significant antibacterial activity across all formulations. However, the antifungal activity was restricted. The preservation effectiveness criterion (bacterial/yeast counts < 10 CFU, mold < 20 CFU) was only fulfilled by ibuprofen gel and clotrimazole cream. Although there were color changes, stability tests verified that the active components such as ibuprofen (reduced from 97.5% to 92%) and clotrimazole (reduced from 99.9% to 95%) decomposed minimally and had acceptable physical characteristics. Particularly against fungus, the extract was surpassed by chemical preservatives (methyl/propyl paraben).

Conclusions: Certain semi-solid pharmaceuticals can benefit from the stability and antimicrobial protection provided by guava leaf extract, a natural preservative. The weak antifungal activity of the guava leaf extract emphasizes the necessity for specific improvements in the formulation.

Introduction

Although topical treatments, particularly those in multi-use packaging, are prone to contamination with repeated application, the skin serves as a natural barrier against microbial invasion [1,2,3,4,5,6]. Despite this, skin is prone to various disorders, including inflammation and skin infections caused by different types of bacteria, fungi, or parasites [7,8]. These disorders are often treated with topical medications such as creams and gels [9], which are pharmaceutical formulations composed of several ingredients, such as the active molecules and other substances called excipients [10]. To preserve the composition of active ingredients in pharmaceutical formulations, it is necessary to use preservatives [11] such as parabens [12]. However, artificial preservatives can disrupt hormonal function, in particular the female hormone estrogen [13,14]. The side effects of these preservatives have led to growing interest in using natural preservatives derived from plant extracts as an alternative, as they are less harmful than chemical substances [15].

A number of studies have already been carried out on the use of plant derivatives or extracts as preservatives, with certain plants having demonstrated antimicrobial and antifungal properties [16,17]. It was found that Psidium guajava (L.) had several pharmacological activities [18], particularly antimicrobial activity [19].

The medicinal plant Psidium guajava, or guava, has been extensively researched and prized for its diverse phytochemical composition. Various bioactive components, including flavonoids (including quercetin, guaijaverin, and kaempferol), tannins, saponins, triterpenoids, and essential oils, have been found in guava leaf and fruit extracts across numerous investigations [16,17]. The plant’s antibacterial, antioxidant, and anti-inflammatory properties are thought to be mostly attributed to flavonoids and tannins, which are especially prevalent in ethanolic and methanolic extracts [18]. A similar antimicrobial profile has been reported across several investigations; however, the presence of these chemicals may vary based on the extraction process, plant part employed, and geographical origin [19].

Flavonoids and tannins, in particular, are the phytochemicals that work together to give Psidium guajava extract its antibacterial properties. Quercetin is one flavonoid that can interfere with DNA replication by rupturing bacterial membranes and inhibiting enzymes like DNA gyrase. By using metal ion chelation, tannins can deprive microorganisms of vital nutrients and inactivate bacterial proteins and enzymes. All of these behaviors affect the development and survival of bacteria [18,20,21].

Semi-solid formulations should be free from microbial contamination during production, storage, and use; preservative effectiveness testing is crucial, especially for formulations that are given in numerous doses. Because active pharmaceutical ingredients (APIs) have frequently selective or narrow-spectrum activity, additional preservatives are needed even in formulations that contain APIs with antimicrobial activities. On the other hand, preservatives are made to prevent the activity of variety of bacteria, fungi, and yeasts, guaranteeing the product’s safety and effectiveness during its whole shelf life [10,11,15].

Our study is based primarily on the development of several formulations for cutaneous treatment. The formulations were clotrimazole cream for the treatment of vulvar infections caused by vulvovaginal fungi such as Candida, a permethrin cream for the antiparasitic treatment of external infections, and a gentamicin cream as an antibiotic against staphylococci. The other two formulations were an indomethacin emulgel and an ibuprofen gel as anti-inflammatory agents. The antibacterial (S. aureus: ATCC 6538, E. coli: ATCC 8739, and P. aeruginosa: ATCC 9027) and antifungal activity (C. albicans: ATCC 10231 and A. brasiliensis: ATCC 16404) of Psidium guajava (L.) extract (10%) were tested in all five formulations. In our study, high-performance liquid chromatography (HPLC) was used to detect and determine the concentration of active ingredients present in the formulations. Finally, the stability of these pharmaceutical products, in the form of creams and gels, was assessed for three months under accelerated conditions (40°/75% RH).

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Preparation of Ibuprofen Gel

This pharmaceutical preparation was designed using the protocol established by Kashyap et al. [33], with a specific adaptation for our research. The new gel formulation was developed by using ibuprofen (as a non-steroidal anti-inflammatory drug) (5.0% w/w) as the active molecule with 23 g isopropyl alcohol (solvent). The ingredients were mixed in a container for 5 min using a hand blender; this mixture was transferred to another container containing 20 g propylene glycol (solvent) and mixed for 5 min. Then, a solution containing 10 g P. guajava leaf powder in 38 g pure water was added while stirring continuously, followed by the addition of 3 g Sepigel (viscosity increasing agent) and 1 g isopropyl myristate (vehicle). The formulation was mixed for 5 min using a hand mixer. Three preparations were developed for this formulation, the first of which included a natural preservative based on an extract of the plant studied, at a concentration of 10%. The second preparation, used as a positive control, was formulated with chemical preservatives, notably 0.12% methyl and 0.08% propyl paraben. The third preparation, used as a negative control, was preservative-free.

Imtara, H.; Atiya, M.; Hanania, M.; Abbadi, J.; Mudalal, S.; Al-Rimawi, F. Guava Leaf Extract as a Sustainable Preservative Alternative in Semi-Solid Pharmaceuticals: Efficacy and Stability Assessment. Antibiotics 2025, 14, 1176. https://doi.org/10.3390/antibiotics14121176

Read also our introduction article on Topical Excipients here: