Among the Candida species, C. albicans has mainly been proposed to bring about oral candidiasis in immunocompromised individuals. This is attributed to the suppression of local and systemic defense mechanisms (1). It is a natural human oral flora in 20-50% of the healthy individuals that engenders infection in conditions such as weakened immune system (2). The most common local and systemic causes that predispose oral candidiasis subsided to salivary secretion, inappropriate dental prostheses, endocrine disorders such as diabetes, nutritional deficiencies, smoking, poor oral hygiene, use of immunosuppressive drugs, chemotherapy, and radiation therapy (3).
Complications of Candida overgrowth in the mouth are local discomfort, altered taste, and dysphagia, which results in malnutrition, slow recovery, and prolonged hospitalization (4).
Currently, the first choice for the treatment of oral candidiasis is nystatin (5). Bad taste and nausea are among the side effects of this chemical medicine. Furthermore, since nystatin is stable in the form of powder, it must be continuously diluted to use. This drug should be consumed every 6 h for 14-21 days, which is unpleasant for patients (6). Natural products are valuable resources in Persian traditional medicine and have been long used for the treatment of diseases. All over the world, many plants have been exploited for their medicinal value (7). With the current growing interest in the application of scores of herbal-originated medicines, physicians and patients have been persuaded to use herbal instead of chemical medicines. Progression in this field could improve patient cooperation (8).
Given the side effects of chemical drugs and complex production stages as well as the fact that humans can develop resistance to chemical drugs, many herbal medicines are commonly discussed(3, 9). One of the most widely used plants is Aloe vera wich has a growing consumption trend. This is a tropical plant grows in most parts of Asia and north Africa with succulent leaves (10), which grows rapidly in tropical regions (3).
 Aloe vera has anti-inflammatory, wound healing, scar reduction, antimicrobial, and anti-fungal effects due to its active ingredients (11). Aloe vera is also effective in treatments related to gingivitis, periodontal surgery (12), aspirin burns (13), angular cheilitis, aphthous ulcers (10), lichen planus (14), burning mouth syndrome (15), and wound healing (16). The anti-microbial, anti-fungal, and anti-inflammatory effects of Aloe vera are well-known worldwide (17). Previous literature has focused on the ethanolic extract of Aloe vera (18), whereas this study applied its hydroalcoholic extract. The issue has figured considerably in medicine.  This study attempts to determine the antifungal activity of different concentrations of hydroalcoholic extracts of Aloe vera against C. albicans in in vitro conditions.
 

To shed light on the anti-fungal activity of different concentrations of Aloe vera extract and nystatin on the growth of C. albicans, we used the disk diffusion method to determine MIC with 8 replicates for each concentration. According to the results, and based on the serial concentrations of Aloe vera extract (75%, 50%, 25%, 12.5%), the mean diameters of the inhibition zone of Candida albicans growth were  7.56± 0.49, 4.81± 0.53, 0.75 ± 0.47, and 0.00 mm, respectively. As set out in Table 1, a higher concentration of Aloe vera extract had a higher anti-fungal activity.
To determine the MIC, we prepared 15% and 20% concentrations of Aloe vera solution and conducted eight replications for them. The results of MIC and sensitivity test of disk diffusion displayed that the 15% concentrations of Aloe vera had inadequate anti-fungal activity. The 20% concentrations were reflected in the results as the MIC for C. albicans in the present study (Table 1).

Table 1. Zone of growth Inhibition in hydroalcoholic extracts of Aloe vera (mm)

P-value= 0.001
Kruskal-Wallis test
 

Overall, the results presented below indicate that the mean diameter of the inhibition zone of the C.albicans growth beard was significantly different for various concentrations of Aloe vera (p=0.001). The zone of inhibition of negative and positive control groups are set out in Figure 1 and Table 2.

As can be observed from Figure 1, the maximum diameter of the inhibition zone of Albicans growth was measured in nystatin, and 75% Aloe vera extract, respectively. The mean diameter of the inhibition zone of C. albicans growth was statistically significant at concentrations of 15% and 20% Aloe vera extract, confirming with DMSO 1% did not affect Candida growth (Table 2).  
To determine the MIC of nystatin, and reach a gold standard, serial dilutions of  1were prepared. Three replicates were performed at each dilution, and the nystatin MIC, and inhibition zone of C. albicans growth diameter was determined as  and 1.3 mm in three replicates, respectively (Table 3).

Discussion

The production of synthetic drugs could improve health care facilities worldwide. The present study indicates that the Aloe vera extract has anti-fungal activity. Saniasiaya et al. (22) and Shireen et al. (23) concur the anti-fungal activity of Aloe vera extract increases at higher doses. This is also in agreement with studies done by Shireen et al. (23).
This study probe highlights the fact that Aloe vera extract is effective in the case of candidiasis, especially for immunocompromised patients like HIV subjects and organ transplant patients, as use decrease the burden of the medication. Owing to the fact that it is relatively easy to cultivate, the usage of Aloe vera is also cost-effective.
Given the evident treatment applications of herbal medicine, returning to nature and reusing herbal medicines can prevent the probable side effects of chemical drugs (24). Iran has a rich and valuable herbal resource due to its diverse climatic conditions and nature. One of the most valuable medicinal plants is Aloe vera (17). According to the above-mentioned functional effects of Aloe vera, this survey investigated the anti-fungal activity of various concentrations of Aloe vera extract on C. albicans through an in vitro study.
In addition to the anti-fungal impact of Aloe vera, other potential areas of application in dentistry are applications directly at sites of periodontal surgery (25), aspirin burns (26), Angular cheilitis, aphthous ulcer. Aloe vera could also be used to treat oral lichen planus, and alveolar osteitis (23).
In the current study, the mean diameter of the inhibition zone of C.albicans growth at 75 % concentration extract of Aloe vera was comparable to standard nystatin suspension and 20% Aloe vera concentration was determined as the MIC for C. albicans.
In the present study, we used the hydro-alcoholic extracts of Aloe vera and the disk diffusion method to evaluate the anti-fungal activity of Aloe vera extracts, which is in line with previous literature (21, 23, 27).
 In the present study, serial concentrations of the hydroalcoholic extract of Aloe vera (12.5%, 25%, 50%, 75% ) were examined, and our experiments are in line with Jain et al.(21) Abdul-Jabbar et al.(28) also used hydroalcoholic extracts of Aloe vera at concentrations of 15%, 20%, 25%, and 30%, which was at variance with this study. It was mentioned Aloe vera extracts at high concentration had a reliable anti-fungal activity. Of course, the aqueous extract of Aloe vera was less effective than the alcoholic type. Since the nature of the anti-fungal activity of alcohol is more than water (29), this study applied hydroalcoholic extracts of Aloe vera, similar to the previous literature (30).
Nystatin (100,000 IU) was used as a positive control and the gold standard for comparing Aloe vera^, s anti-fungal properties, which is in alignment with Al-Husseini (2010),  Stanley et al. and Amjed et al. (2017) studies (27, 31, 32). Chlorhexidine and Amphotericin B were used as a positive control by Shireen et al. (2017) which is congruous with our study (23).  In good agreement with previous studies, 1% DMSO was applied as the negative control group (33, 34).
In the present study, the mean inhibition zone of growth C. albicans was measured as zero, 0.75± 0.46, 4.81 ±0.53, and 7.56 ±0.49 mm at 12.5%, 25%, 50%, and 75% ​​ concentrations of Aloe vera extract in eight replications, respectively.
Jain et al.(21) also evaluated 12.5%, 25%, 50%, and 100% Aloe vera concentrations and reported  zones of inhibition of 0, 0, 1.06 ±0.41, and 3.35 ± 0.59 mm, respectively. This is lower than the rate obtained in the present study. This is why they used only the solid mucilaginous gel of Aloe vera instead of leaf extracts (as were used in the present study). Based on their results, concentrations of 50% and 100% of Aloe vera had anti-fungal effects, which is in agreement with our findings. In this regard, our findings are in line with those of Jain et al. (21). A probable mechanism of the gained antifungal properties is attributed to the tannins, saponins flavonoids, alkaloids, and steroids, contained in Aloe vera extracts (18).
Since the results of an experiment can be affected by various factors such as essential oil extraction method, inoculation volume, growth phase, the medium used for growth, ambient pH, incubation time, and incubation temperature, comparing the published data are controversial and difficult to generalize. Many studies to date, however, have attempted to cite MIC as a criterion for determining the antimicrobial activity of essential oils (35, 36).
Our finding is at variance with the research of Jain et al.(21), as we elicited 20% of Aloe vera extract as MIC, while previous evidence reported 15%(21). The susceptibility method is probably responsible for this discrepancy. Jain et al. used a broth microdilution test for MIC determination while the disk diffusion method was applied in the present study (21).
The findings provide support for the anti-fungal activity of Aloe vera extract. However, our research suffers a critical limitation; due to the restricted availability of the hydroalcoholic extract of Aloe vera to prepare herbal extracts at different concentrations.
Given that our findings are based on some limitations, the results of our analyses should be interpreted with the utmost caution.
  Modalities targeted at the use of Aloe vera against C. albicans can prove to be more useful and accordant compared to common anti-fungal drugs for therapeutic goals against a variety of oral fungal diseases (18). There are further research agendas here that could fruitfully be perused. For example, the antifungal activity of Aloe vera can be increased in many folds in combination with other herbal medicines. Hence, it would be further evaluated. The conclusion of this survey should be interpreted with caution. More studies should be programmed in the field of phytochemistry exercising attention to both in vivo, and in vitro analysis. The isolation of bioactive compounds could be a good idea for future studies.

 

Conclusion

The extract of Aloe vera has concentration-dependent anti-fungal activity against C. albicans. There was a significant difference in the mean diameters of the non-growth zones based on the concentration of Aloe vera. Aloe vera extract at a 75% concentration effectively inhibited the growth of C. albicans. A concentration of 20% was determined as the minimum inhibitory concentration for C. albicans. Thus, Aloe vera can be proposed as an alternative traditional anti-fungal choice to therapeutic goals.
 
 

Acknowledgements

This article is extracted from a thesis (Dentistry student) conducted in Yazd Dental faculty. Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Thanks are owed to Yazd Shahid Sadoughi University of Medical Sciences for their financial supports (6431). The authors also would like to thank Mrs Ghafoorzadeh (Ms in Laboratory Technology Dep., Paramedicine School) for her kind laboratory works.

 

Funding

This study was financially supported by Yazd Shahid Sadoughi University of Medical Sciences (no 6431). The funding organization had no role in study design, data collection and analysis, interpretation of data, and manuscript preparation.

 

Conflicts of Interest

The authors declare that there is no conflict of interest.