The study, published in the Journal of Cosmetic Dermatology and funded by The Procter and Gamble Company (P&G), said research conducted by the US and UK based teams found specific antioxidant activities in green tea extract, or Camellia sinensis, protected against protein damage in hair caused by UV exposure. Extracts most effectively prevented UV damage when incorporated into leave-on applications, they found, though protection varied according to the level of polyphenols present in the extract.
UV a ‘major source’ of hair damage
The researchers said UV was a “major source of hair damage” and so prevention of this was “of high interest to cosmetic companies”.
“…The proteins, lipids, and melanins in hair are all targets for sunlight irradiation—absorbing UV radiation,” they said. “These reactions have been studied and reported on in both hair and wool.”
According to the researchers, UV exposure caused damage to hair proteins and created reactive oxygen species, loss of hair strength, natural shine and “hair color changes such as yellowing or fading of artificial color.”
Primary antioxidants were one approach to reducing UV damage, they said, and multiple botanicals had been found effective in studies, including pomegranate and honeysuckle extracts for color change and artichoke and rice extracts for protein protection.
However, they added: “None of these studies include an analysis of extract compositions and how these compositions correlate antioxidant activity of botanical extracts with prevention of hair damage.”
“This is important as extracts from plant species can vary significantly from sample to sample and between suppliers,” the researchers said.
Level of UV protection linked with antioxidant activity
The study tested 16 Camellia sinensis extracts from seven suppliers, in green and white varieties, and various delusion levels, some of which were unknown. Results showed the extracts could protect hair from UV damage, and showed a higher level of protection when the specific extract had higher levels of antioxidants, specifically polyphenols.
Extracts were tested for OxiSelect Oxygen Radical Antioxidant Capacity (ORAC) score, which indicated antioxidant levels, including that of antioxidants catechins and procyanidins found in tea.
“Data show that botanical extracts high in polyphenols such as catechins and procyanidins will have the greatest efficacy in both ORAC testing and UV hair protection,” the researchers said.
The extract with the highest ORAC score showed the same level of biomarker intensity as hair not exposed to UV radiation at all.
Not all tea extracts are made the same
However, the study showed a wide variability in ORAC scores between extracts, with the highest score at 3.4 million and the lowest at 92. The researchers said this difference could help determine what type of tea extract a product should use. For example, the study suggested non-fermented teas were higher in the antioxidant catechin because of the chemical effects of fermentation and heat on antioxidant compounds.
Other factors also impacted the antioxidant level of a given tea extract, including “species, season, age of leaves (plucking positions), climate, horticultural conditions (soil, water, fertilizers, etc.) in addition to extraction protocol”, they said.
Tests conducted to map out the composition of these green tea extracts, they said, could also be used across other types of botanical extracts in order to determine the antioxidant composition and effectiveness between suppliers and types of extract moving forward.
Source: Journal of Cosmetic Dermatology
Published August 2021, online ahead of print – doi: 10.1111/jocd.14387
Title: “Protection of hair from damage induced by ultraviolet irradiation using tea (Camellia sinensis) extracts”
Authors: SL. Davis et al.