26 PRESERVATIVES Natural extracts could be used as alternative


preservatives as they have various properties in personal care products, including anti- inflammatory, antioxidant and anti-microbial properties. In particular, the anti-microbial activity of natural extracts is more effective in inhibiting the growth of microorganisms due to various modes of action.5 Therefore, we conducted research to


develop plant-derived Magnolia officinalis bark extract and heptyl undecylenate as multifunctional ingredients with various activities.


Antimicrobial activity ofMagnolia officinalis bark extract Magnolia officinalis bark extract is an important herb that contains diverse, biologically active compounds, including magnolol and honokiol. To evaluate the anti-microbial activity, a well-diffusion assay was performed. The degree of anti-microbial activity was shown by measuring the diameter of the inhibition zone formed on the plate (Figure 1). According to the analysis results,


Magnolia officinalis bark extract was strongly antimicrobial and antifungal activity against skin-related microorganisms, such as Staphylococcus aureus, Cutibacterium acnes, Candida albicans, Aspergillus brasiliensis, and Trichophyton rubrum. Concentrations greater than or equal to 0.1% ofMagnolia officinalis bark extract completely inhibited the growth of gram-positive bacteria, yeast and mould, S. aureus and C. albicans, whereas greater than or equal to 0.02% ofMagnolia officinalis bark extract inhibited the growth. However, it did not show an inhibitory


effect on gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa). As a result, Magnolia officinalis bark extract can potentially be used as an antimicrobial agent for personal care products.


Preservative boosting properties of A-Silkne in formulation Natural preservatives derived from plant and microorganisms with antimicrobial activity can reduce or eliminate the use of preservatives in personal care product formulations. The preservative efficacy test (PET), also known as the challenge test, determines


A-Silkne conc. (%, w/w)


1% Bacteria Yeast Mould


2% 3% 1%


2% 3% 1%


2% 3%


(inoculation) Day 7 6.3


6.3 6.3 5.4 5.4 5.4 5.3 5.3 5.3


0 0 0


5.4 5.4 5.3 5.2 5.1 5.1


INHIBITION ZONE SIZE (MM)


Magnolia offcinalis bark extract conc.


2% 1%


0.5% 0.2% 0.1%


0.04% 0.02%


Bacteria Gram (+)


S. aureus 22 22 22 21 18 11 8


C. acnes >30 >30 >30 >30 >30 18 -


Yeast


20 20 20 17 8 - -


Mould


C. albicans A. brasiliensis 19 19 18 16 10 8 7


Figure 1: Antimicrobial analysis ofMagnolia officinalis bark extract


the effectiveness of the antimicrobial agent by calculating the logarithm of the number of viable microorganisms after microbial contamination of the product. In this study, the PET was made using


Personal Care Products Council guidelines. A combination ofMagnolia officinalis bark extract and heptyl undecylenate (A-Silkne) was used in an oil balm to evaluate the preservative efficacy. Microorganisms used for artificial


contamination were bacteria (E. coli ATCC 8739, P. aeruginosa ATCC 9027, S. aureus ATCC 6038), yeast (C. albicans ATCC 10231) and mould (A. brasiliensis ATCC 16404) at a final concentration of 106


CFU/g for bacteria and 105


CFU/g for yeast and mould. The preservative efficacy was determined by sampling 1g from the formulation at each time-point of 0, 7, 14, and 28 days. In the PET with 1% A-Silkne, there was an immediate reduction of bacteria growth after seven days and inhibited the growth of bacteria until 28 days (Table 1). Although the inhibitory effect on yeast and mould was weak, the inoculated microorganisms steadily


THE NUMBER OF VIABLE MICROORGANISMS (LOG CFU/g) Day 0


decreased for four weeks. Therefore, A-Silkne can be used as a preservative booster for effective preservative systems of personal care products.


Preservative effect of A-Silkne in combination with glyceryl caprylate To evaluate the preservative effect in various formulations, PET was conducted by combining A-Silkne with glyceryl caprylate, a natural multifunctional ingredients. Specifically, in order to evaluate the preservative efficacy of the A-Silkne with glyceryl caprylate in a various personal care products formula (oil balm, O/W type cream, and shampoo), samples were inoculated separately with each microorganism at a final concentration of 106 and 105


CFU/g for yeast and mould.


The preservative efficacy was determined by sampling 1 g from the formulation at each time- point of 0, 7, 14, and 28 days. In a formula of oil balm preserved with 2% A-Silkne and 0.4% glyceryl caprylate, from day 7, bacteria (E. coli ATCC 8739, P. aeruginosa ATCC 9027, S. aureus ATCC 6038), yeast (C. albicans ATCC 10231) and mould (A. brasiliensis ATCC 16404) were not detectable.


Day 14 0


0 0


5.4 5.3 5.2 5.0 5.0 5.0


Table 1: Preservative efficacy test of A-Silkne in oil balm PERSONAL CARE July 2023


Day 28 0


0 0


5.3 5.2 5.1


5.0 5.0 4.9


THE NUMBER OF VIABLE MICROORGANISMS (LOG CFU/g) Day 0


Oil balm


Cream (o/w type)


Cream (w/s type)


Shampoo


Bacteria Yeast


Mould


Bacteria Yeast


Mould


Bacteria Yeast


Mould


Bacteria Yeast


Mould


(inoculation) Day 7 6.3


5.2 5.3 6.3 5.2 5.3 6.6 5.3 5.0 6.3 5.2 5.3


0 0 0


1.0 2.7 4.3 0


2.1


2.3 0 0


4.2


T. rubrum 30 30 20 20 15 - -


-: No antimicrobial activity Well size: 6mm N.C. : DMSO


CFU/g for bacteria


Day 14 0


0 0 0 0


4.2 0 0


1.3 0 0


4.0


Day 28 0


0 0 0 0


3.4 0 0 0 0 0


3.0


Table 2: Preservative efficacy test of A-Silkne with glyceryl caprylate in various formula


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