Widely used in traditional medicine, these botanical extracts are today commonly applied in cosmetic formulations because of their antioxidant and anti-inflammatory properties.
However, research on the skin care effects of mixed extracts remains limited.
To elucidate the optimal proportions of the three extracts to maximise their benefits, researchers from Chiang Mai University in Thailand conducted a study using a two-level full factorial design.
The antioxidant activity of all extracts was evaluated via DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power), and lipid peroxidation inhibition assays.
The results showed that the concentration ratio of C. arabica, C. asiatica, and C. longa extracts that achieved the highest antioxidant activity was 0.5:6:2 mg/mL.
Increased concentrations of C. arabica and C. longa extracts had the main influence on free radical scavenging activity in the DPPH assay, while C. arabica extract had the most significant influence on increasing FRAP value.
“The concentrations of these extracts had a statistically significant impact on DPPH inhibition. The positive interactions can produce a synergistic effect, where the combined result is greater than the sum of their individual effects, as the different active compounds work together to enhance antioxidant activity,” the authors wrote.
Hyaluronidase is an enzyme that breaks down hyaluronic acid. Increased hyaluronidase activity diminishes the skin’s ability to retain moisture, leading to dryness, volume loss, and wrinkle formation.
It was found that the proportion of C. arabica, C. asiatica, and C. longa extracts that achieved the highest hyaluronidase inhibition percentage value was 10:10:5 mg/mL.
A higher concentration of C. arabica extract had the biggest effect on a higher percentage of enzyme inhibition, followed by the combined influence of C. asiatica and C. longa extracts.
For the increase in the percentage of lipid peroxidation inhibition, C. arabica and C. longa extracts were the main influencing factor.
Delay skin ageing
Free radicals are known to stimulate breakdown of collagen and elastin, damage the dermal connective tissue, and accelerate premature skin ageing. Notably, all three extracts possess DPPH free radical-scavenging properties.
In addition, the high antioxidant activity of C. arabica, C. asiatica, and C. longa extracts was attributed to the presence of phenolics and flavonoids.
C. arabica extract, in particular, showed “outstanding” antioxidant activity compared to the other two.
“There were several possible reasons why C. asiatica extract showed lower antioxidant activity. It contains compounds like asiaticoside, madecassoside, and other triterpenoids, which may not be as effective in scavenging lipid peroxyl radicals compared to other antioxidants such as tocopherol acetate or polyphenols.
“These specific compounds might lack the necessary redox potential to effectively interrupt the lipid peroxidation chain reaction. Another possibility is that the concentration of bioactive compounds in the extract may be insufficient to produce a strong antioxidative effect in complex biological systems. Additionally, the bioavailability of these compounds could be limited, reducing their efficacy in preventing lipid peroxidation at the site of action.”
Combining strengths for stability
Mixed extracts reportedly tend to be unstable when exposed to light.
To support their application as raw materials in cosmetics, the researchers in this study investigated photostability enhancement of the mixed extracts using an antioxidant agent or a sunscreen agent.
It was observed that bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) demonstrated better UV protection compared to titanium dioxide.
BEMT protects against UVA/UVB rays, especially in the UVA spectrum. It is also highly stable under sunlight and effective over time, preventing the breakdown of phenolic compounds due to UV exposure.
As a stablising agent, sodium metabisulfite enhances the stability of active substances by binding and inhibiting the reaction of free radicals.
When the three extracts were combined with BEMT and sodium metabisulfite, the reduction in total phenolic content was less than that observed in individual extracts, mixed extracts, or mixed extracts combined with antioxidants alone.
This suggests that the combination of sunscreen and stabilising agents provides elevated protection against degradation caused by UV exposure, ensuring better preservation of bioactive compounds in the extracts.
Nevertheless, it should be noted that the total phenolic content decreased more when the mixed extracts were combined with a sunscreen agent alone.
Also, C. longa extract exhibited more light degradation than C. asiatica and C. arabica extracts because of curcumin’s sensitivity to UV light.
“Although both antioxidants and sunscreen agents effectively reduce the degradation of total phenolic compounds in the extracts, the combination of sodium metabisulfite and BEMT with the mixed extracts can significantly increase their photostability.
“All results indicate that the mixed extracts exhibited antioxidant activity and hyaluronidase inhibitory activity with good photostability for further application in cosmetic products,” the researchers concluded.
Source: Cosmetics
https://doi.org/10.3390/cosmetics11060201
“Optimizing Antioxidant and Anti-Hyaluronidase Activities of Mixed Coffea arabica, Centella asiatica, and Curcuma longa Extracts for Cosmetic Application”
Authors: Natthanan Phupaisan, et al
