Scientifically known as Curcuma longa, turmeric is a perennial herbaceous plant belonging to the Zingiberaceae family. Thanks to its antioxidant, anti-inflammatory, and antibacterial properties, turmeric is beneficial for skin care. For instance, it can be used to reduce the appearance of pigmentation spots. Let's explore its mechanism of action together.
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Curcuma against dark spots?
Summary
Published May 17, 2023,
updated on October 4, 2024,
by
Pauline, Chemical Engineer
—
5 min read
Brown Spots: What are their origins?
The brown spots form as a result of melanin accumulation in the skin. This dark brown pigment is an essential element that plays a protective role against UV rays. However, in the case of overproduction, it does have an impact on the uniformity of the complexion. The pigment spots are thus the result of the alteration of the skin's complexion. There are three categories of brown spots depending on the cause.
The sun spots caused by prolonged and repeated exposure to the sun's UV rays.
The production of melanin is triggered following exposure to sunlight. Indeed, UV rays act on tyrosine, an amino acid, and, thanks to the enzyme tyrosinase, initiate a cascade of reactions leading to the synthesis of melanin (melanogenesis). Sunspots gradually form throughout life, as sun exposure is repeated. That's why it's important to apply a daily sunscreen. Tobacco or pollution can also play a role in their appearance, as these elements generate oxidative stress in cells and accelerate skin ageing.
The pregnancy mask is linked to hormonal changes.
During pregnancy, the levels of oestrogen and progesterone in the body significantly increase, leading to an overproduction of melanin by the melanocytes. Also known as melasma, the pregnancy mask can also appear following the use of contraceptive pills or hormone replacement therapy.
Thepost-inflammatory hyperpigmentation.
These brown spots form as a result of skin inflammation or lesions. Indeed, during inflammation (acne, burn, injury...), pro-inflammatory cytokines stimulate the activity of melanocytes.
Is turmeric effective on brown spots?
A close relative of ginger, turmeric is a perennial plant that thrives primarily in the humid climates of certain African and Asian countries. Currently, there are approximately 700 species of Curcuma longa. The mechanical grinding of the rhizomes of this plant produces a golden-orange powder with a spicy flavour and multiple benefits for the skin. It is particularly used to combat dark spots, as it contains several active ingredients inhibiting the process of melanogenesis.
The flagship molecule of turmeric is curcumin, accounting for nearly 10% of its composition. A study conducted in vitro on skin cells has shown that this molecule has a tyrosinase activity inhibitory effect, the enzyme that allows the conversion of tyrosine into melanin. It has also been shown that curcumin induces a decrease in the expression of the gene coding for tyrosinase.
Turmeric also contains alpha-turmerone, a sesquiterpene that acts on brown spots. This compound notably inhibits the synthesis of the hormone α-MSH (α-melanocyte-stimulating hormone), a hormone that activates certain melanocortin receptors. These receptors trigger the production of melanin. Alpha-turmerone can also prevent the phosphorylation of the CREB protein (C-AMP Response Element-Binding Protein). This phosphorylation triggers a cascade of reactions leading to the stimulation of tyrosinase transcription.
Finally, turmeric has a preventive effect on dark spots. Curcumin is indeed a powerful antioxidant due to its chemical structure, which includes several double bonds. This feature allows it to make a donation of an electron to free radicals. This stabilises and neutralises these reactive species, which are capable of stimulating melanogenesis.
Sources
SUDHEER A. & al. Antioxidant and anti-inflammatory properties of curcumin. Advances in Experimental Medicine and Biology (2007).
WONGKAJORNSILP A. & al. Modulation of antioxidant defense by Alpinia galanga and Curcuma aromatica extracts correlates with their inhibition of UVA-induced melanogenesis. Cell Biology and Toxicology (2010).
LEE S. J. & al. Aromatic-turmerone inhibits α-MSH and IBMX-induced melanogenesis by inactivating CREB and MITF signaling pathways. Archives of Dermatological Research (2011).
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