I have chosen this research question because I struggled with finding appropriate skincare products to deal with my acne. Some are less effective than others, and trial and error with different products would harm my skin. Therefore, comparing common natural and processed skincare products will allow me to gain insights into which of the two would be more beneficial to my skin. Skin conditions, such as acne, often arise from bacterial infections or imbalances in skin flora. Various skincare products are marketed for their antibacterial properties since they possess components that kill most bacteria. The choice of E. coli K-12 strain as the preferred bacteria for testing the effectiveness of skincare products is rooted in its notable characteristics, particularly its documented resistance to various antibiotics. It has been extensively reported to exhibit resistance to multiple antibiotics. According to data from the Anti-Microbial Resistance Study in Indonesia, there has been a noteworthy surge in antibiotic resistance among Escherichia coli bacterial isolates. The resistance rate increased from \(17\%\) in 2010 to a concerning \(52\%\) in 2012. These resistance patterns in E. coli make it a particularly suitable candidate for assessing the efficacy of skincare products. By leveraging a strain known for its resistance, I can more effectively evaluate the potential impact of skincare formulations on bacterial viability, providing valuable insights into the product's antimicrobial properties.

Scientific studies have explored the antibacterial properties of natural compounds. For instance, research has shown that Curcuma longa (turmeric) possesses antimicrobial activity against various bacteria, including E. coli (Chirag et al., 2017). Additionally, Benzoyl peroxide and Salicylic acid are commonly used synthetic antibacterial agents in skincare products (Nakatsuji et al., 2008). While previous research has done an excellent job of investigating the properties, and further testing it against human skin; it has a few limitations. The focus tends to lie on specific skincare products or individual ingredients in them which limits the scope of understanding their broader implications. Additionally, some lack a comparative analysis of natural and processed products. To address this, my exploration will include a variety of natural and processed skincare products to provide a much more comprehensive comparison and a more holistic understanding of their effectiveness.

Questions the IA Will Answer:
1. How effective are natural skin care products like Curcuma longa (turmeric) and Aloe barbadensis (aloe vera) compared to industry-made products containing Benzoyl peroxide and Salicylic acid in inhibiting the growth of Escherichia coli (K-12 strain)?
2. To what extent do these skincare products contribute to inhibiting the growth of non-pathogenic bacteria?

1. Escherichia coli (K-12 strain)
- Chosen due to its resistant behaviour to most antibacterial microbes.
2. Natural skincare products (Curcuma longa paste and Aloe barbadensis gel)
- Because they are the most common and easily available around me.
3. Industry-made skincare products (Benzoyl peroxide cream and Salicylic acid cleanser)
- Chosen because they are products that I had with me and frequently use.
4. 40 discs made out of filter paper due to their absorbent nature, they were best for
5. Nutrient agar plates to facilitate the growth of the bacteria
6. Incubator to keep the temperatures for growth constant
7. Measuring equipment to find the distance of the zone of inhibition.
8. The temperature of 37 degrees Celcius was chosen because this is the temperature that mimics the normal human body temperature. Moreover, the antibacterial properties of the different skincare products are retained at this temperature which reflects their intended use on human skin.
9. Additionally, controlling the concentration of skincare products ensures that any observed differences in antibacterial efficacy are due to the products themselves and not variations in concentration. The \(5\%\) concentration falls within a range where most treatments exhibit measurable antibacterial activity without completely inhibiting E. coli growth. This ensures that I see a spectrum of effectiveness, allowing for meaningful comparisons and insights.
10. 48 hours of incubation time was deemed best by conducting pilot tests with varying incubation times (e.g., 24-36-48 hours) to observe the progression of inhibition zones. Monitoring the plates over time helped identify the point where inhibition plateaus or starts to decline due to factors like cell death or overgrowth. Moreover, 48 hours aided in determining the maximum inhibition area compared to the initial.

Research hypothesis: Natural skincare products, such as Curcuma longa(turmeric) and Aloe barbadensis (aloe vera), will be more effective in killing bacteria compared to industry-made products containing Benzoyl peroxide and Salicylic acid.

This might be due to synergistic effects, where the interaction of multiple natural compounds in a product might enhance their combined antibacterial activity (Ayaz et al., 2019), but robust scientific evidence for such synergies is often lacking and requires further research.

Null hypothesis: There will be no difference in effectiveness between natural skincare products such as Curcuma longa(turmeric) and Aloe barbadensis (aloe vera), and industry-made products containing Benzoyl peroxide and Salicylic acid.

1. Prepare the solutions for all the skincare products.
a. Tumeric:
i. Dissolved 2.5 g of turmeric powder into 50 mL of distilled water.
b. Aloe vera:
i. Extracted Aloe Vera paste from a plant.
ii. Measure 2.5 g of the paste and dissolve it into 50 mL of distilled water.
c. Benzoyl peroxide:
i. Obtained CeraVe 4% Acne Treatment Gel from a pharmacy.
ii. Measure 2.85 g of the gel and dilute it into 50 ml of distilled water to make a \(5\%\) concentration.
d. Salicylic acid
i. Obtained Ordinary Salicylic acid 2% solution from a pharmacy.
ii. Measure 12.5 mL of the solution using a volume pipette and add it to 37.5 mL of distilled water to obtain a concentration of \(5\%\) acid.
2. Set up Petri dishes with E. Coli culture on nutrient agar, and set up at least 3 Petri dishes for each treatment to ensure accuracy.
3. Soak 40 discs, 10 for each skin care product, in a 50 ml beaker for the treatments for the same amount of time ( 10 min ).
4. Incubate all Petri dishes for 48 hours at 37 degrees Celsius.
5. Observe and measure the inhibition zones around each disc
6. Calculate and compare the values obtained.

- Independent Variable: Type of skincare product (natural: turmeric and aloe vera vs. industry-made: benzoyl peroxide and salicylic acid).
- Dependent Variable: Diameter of the inhibition zone, indicating the antibacterial effectiveness.
- Control Variables: Temperature, incubation conditions, and the concentration of skincare product applied to the agar plates.

Table 1: Raw data table

I used the Analysis of Variance (ANOVA) test because ANOVA excels at analyzing data with one categorical independent variable (treatment) having multiple levels (four treatments in your case) and one continuous dependent variable (inhibition zone size). It simultaneously assesses both between-group variability (differences in inhibition zones across treatments) and within-group variability (variation within each treatment group). Moreover, the insights from ANOVA pave the way for post-hoc tests like Tukey's HSD, which identified specific pairs of treatments with statistically significant differences. This helped you pinpoint which products stand out in terms of their antibacterial activity.

The \(f\)-ratio value is 487.26653. The \(p\)-value is \(<.0001\). The result is significant at \(p<.05\).

This study investigated the antibacterial activity of two natural skincare products (Curcuma longa and Aloe barbadensis) and two industry-made products (Benzoyl peroxide and Salicylic acid) against bacteria using an agar diffusion assay. The analysis is presented to the following hypotheses:
- Research Hypothesis: Natural skincare products will be more effective in killing bacteria compared to industry-made products.
- Null Hypothesis: There will be no difference in effectiveness between natural and industry-made products.

Statistically significant difference: ANOVA revealed a significant difference ( p -value \(<0.0001\) ) in inhibition zone sizes, indicating at least one product differed from the others.

Differing activity levels: Post-hoc tests showed Salicylic acid had the largest average inhibition zone ( 15.15 mm ), followed by Aloe barbadensis ( 12.50 mm ), Curcuma longa ( 10.83 mm ), and lastly Benzoyl peroxide ( 9.20 mm ).

Based on the data, the research hypothesis is not supported. Salicylic acid, an industry-made product, exhibited the strongest antibacterial activity. Aloe barbadensis, a natural product, ranked second. Conversely, Benzoyl peroxide, another industry-made product, showed the lowest activity. Curcuma longa, the other natural product, ranked third.

This may be because the sample size may limit generalizability. Lack of information on experimental details hinders deeper understanding. Moreover, the study only measured inhibition zone size, not translating directly to real-world skin effectiveness. While Salicylic acid was most effective here, Benzoyl peroxide might have other well-established skin benefits beyond this specific experiment. The observed ranking doesn't negate potential synergistic effects in natural products requiring further research.

The experimental setup may have had some sources of error that could affect the results of the experiment. One may have been varied concentrations of the skincare products for each of the products. Dissolving powdered turmeric can be inconsistent, leading to uneven dispersion and potential differences in active ingredients across discs. Extracting aloe vera paste from a plant may not yield consistent concentrations of active components due to variations in plant parts used and extraction methods. Additionally, using a specific E. coli strain might not generalize to other bacterial species relevant to skin conditions. Moreover, the variations in culture density or growth phase could have affected bacterial susceptibility to the treatments. The different nutrient agar batches may vary in composition, influencing bacterial growth and susceptibility. Errors may have arisen from manual measurement which can be subjective, introducing inconsistencies, especially for smaller zones.

To improve these errors, I could have used standardised solution preparation methods (e.g., using standardized extracts or commercially available solutions) rather than carrying out the dilution myself. However, this would have been an expensive process and thus manual methods were resorted to. Moreover, I could consider using a broader range of bacterial strains if applicable so that I can have a better ground for comparison of industry-made and natural skincare products. To avoid errors that arise with differences in the growth phases of bacteria, using a commercially available, standardized medium specifically designed for the chosen bacterial strain (e.g., E. coli) would be effective. This ensures consistent nutrient composition and avoids potential variations that could impact growth patterns. Moreover, employing objective measurement techniques, such as image analysis tools would enable higher accuracy in the measurement of the inhibition zones.

This research investigated the antibacterial effectiveness of two natural skincare products (Curcuma longa, Aloe barbadensis) and two industry-made products (Benzoyl peroxide, Salicylic acid) against non-pathogenic bacteria using an agar diffusion assay. Statistical analysis based on ANOVA and post-hoc tests strictly guides this conclusion:

Research Question: How does the antibacterial effectiveness of natural skincare products compare to industry-made products in inhibiting the growth of non-pathogenic bacteria?
Answer: Contrary to the initial hypothesis, the data does not support the notion that natural skincare products are generally more effective than industry-made ones. Statistical analysis reveals significant differences in inhibition zones: ANOVA identified a statistically significant difference (p-value \(<0.0001\)) between the four products. Salicylic acid was the most effective, Aloe barbadensis second and lower activity for the other products: Both Curcuma longa (10.83 mm) and Benzoyl peroxide (9.20 mm) displayed lower activity, with Benzoyl peroxide showing the least effectiveness among the tested products.

Based solely on the statistical analysis of this specific experiment, the initial hypothesis favouring natural products is not supported. Salicylic acid, an industry-made product, demonstrated the strongest antibacterial activity against non-pathogenic bacteria in this controlled setting. However, it is crucial to consider the limitations mentioned above and acknowledge that this finding applies to the specific products and conditions tested. Further research is needed to draw broader conclusions about the general effectiveness of natural versus industry-made skincare products in various contexts and for specific skin concerns.

Chirag, P., Amit, S., & Chetan, P. (2017). Antibacterial Activity of Curcuma longa (Turmeric) Rhizome Extracts against Escherichia coli. Journal of Pharmacognosy and Phytochemistry, 6(4), 42-44.

Nakatsuji, T., Kao, M. C., Fang, J. Y., Zouboulis, C. C., Zhang, L., Gallo, R. L., & Huang, C. M. (2008). Antimicrobial Property of Lauric Acid Against Propionibacterium acnes: Its Therapeutic Potential for Inflammatory Acne Vulgaris. The Journal of Investigative Dermatology, 128(6), 1237-1242.