A research team out of South Korea, Hoang et al, published a synthesis in Cosmetics of existing research into plant-based antioxidants to determine what the personal care industry does and does not know about the ingredients and their topical application.
While the use of antioxidants in cosmetics is fairly ubiquitous, Hoang et al said recent research has called into question the safety of synthetic antioxidants, which needs more investigation.
At the same time, consumer interest in non-synthetic, sustainable and biodegradable products leads to plant-extract based antioxidants, and opens an avenue for use of upcycled ingredients, largely from food production waste.
“The use of plant extracts in skincare products is demanded by consumers, who are becoming increasingly concerned with purchasing ecofriendly products,” Hoang et al said. “However, consumers, are frequently unaware that natural products are complex mixtures of many chemical compounds that can cause adverse reactions.”
To solve that issue and make plant extract antioxidants more usable, Hoang et al said chemists should chemically characterize the composition of their extracts.
Below are three takeaways from Hoang et al’s findings.
There are a number of viable plant sources of antioxidants
Hoang et al listed dozens of sources of plant-based antioxidants, antioxidant minerals and vitamins, some of which are already being topically tested or used. Many of the extracts offer antioxidant properties like ROS neutralization, photoprotective effects, anti-inflammation and lipid stabilization, along with others.
Among the most common cosmetic plant-based antioxidants are those derived from tea leaves. Green tea extracts are common in commercial products already, and along with black tea extracts are a good source of polyphenols.
Vitamins derived from plant extracts can sometimes serve as antioxidants, like vitamin C and E, but can have other topical effects, like the powerful anti-aging retinoids derived from vitamin A and prevention of vascular manifestations of aging with vitamin K.
Plants extracts which can provide useful antioxidants, antioxidant minerals and vitamins include:
- Tea leaves
- Grape seed
- Acerola seed
- Pine bark
- Milk thistle
- Whole grains
- Green leafy vegetables
Flavonoids are abundant and underused
According to Hoang et al, flavonoids are the most abundant of the plant-based actives, with more than 5,000 types extracted and identified. Flavonoids are a derivative of chalcone, a compound involved in plant metabolism
They are most commonly associated with antioxidant properties, in that they scavenge nearly all types of free radicals, are anti-inflammatory, anti-irritant and in skincare are good for binding proteins, making them multi-active.
Some research also shows some varieties flavonoids reduce histamine release, which are the antibodies involved in causing reactions to allergens like pollen.
“Despite their multifunctional properties, flavonoids are underutilized,” Hoang et al said. “The objective of this study was to discuss the potential applications of flavonoids as the main active ingredients in cosmeceuticals.”
Plant-based antioxidants can cause adverse skin reactions and need further testing
While plant extracts offer a variety of potential active and multi-active ingredients, Hoang et al said the uses listed in their paper can’t be explicitly proven at this time due to lack of adequate research. However, there is research suggesting there are limitations in consumer usability.
Natural antioxidants are generally more expensive than synthetics and are prone to degradation. Polyphenols from herbs are also sensitive to light and heat and have low stability.
Natural antioxidants have lower levels of cutaneous bioavailability through low absorption.
Antioxidants can also cause adverse effects like acute toxicity, skin and eye irritation, skin sensitization and photosensitization.
Topical application of vitamins and other natural ingredients can also cause conditions like dermatitis, erythema multiforme and xanthomatous reactions in rare cases. Additionally plant extract can cause allergic reactions in some customers, Hoang et al said.
Despite these limitations, Hoang et al said there is sufficient evidence that plant extracts can provide valuable topical bioactive ingredients, given further research.
“Although the use of antioxidants is promising, there are limited clinical trials in humans examining the role of antioxidants in preventing skin aging,” Hoang et al said. “Thus, further experimental data can be explored in the future, and synergistic effects are recommended for better efficacy in combination.”
2021, 8(4), 106; https://doi.org/10.3390/cosmetics8040106
Title: Feature Papers in Cosmetics in 2021
Authors: H Hoang et al