HYGIENE
The antibacterial power of lichens
Anna Maria Motta – Variati
Lichens are a peculiar group of vegetal organism, which can be described as a symbiotic relationship between an algae and a fungus, that allow them to survive in extreme environmental conditions. Through the chlorophyllous synthesis, the algae feeds the organism with organic compounds, while the fungus, besides absorbing minerals and water from the ground, confers stability and a substrate used by the alga itself to grow. Lichens possess specific bio metabolic
paths that lead to the synthesis of a peculiar group of organic compounds, the lichenic acids, characterized by specific antimicrobial properties and utilised by the lichen to protect itself from the attack of bacteria, fungi and other foreign microorganism.1 Thanks to these properties, several lichens
have been used in traditional medicine for years for making infusions and extracts. In particular, the use in ancient China and Arabia of extracts from the Usnea lichen species is documented in relation to the treatment of cutaneous infections.2 Among the molecules responsible of such
antibacterial activity, usnic acid is the most known and studied. It is a characteristic organic molecule, belonging to the family of lichenic acids, isolated for the first time by Rochleder & Heldt in 1843,3
and found in a wide number of
species and varieties of lichens, including genus Usnea, Cladonia, Cetraria and Parmelia, in concentrations ranging between 0.5-2%.4 Among the lichenic species containing usnic acid, the most commonly used is Usnea barbata - traditionally named old man’s beard due to its characteristic appearance like a beard dangling from the branches of the trees. Thanks to its wide diffusion and being a not protected lichen species, it represents the primary source for usnic acid industrial use.
INCI Function
57
The role of usnic acid Usnic acid antibacterial properties are mainly addressed towards gram+ strains and some fungi species. Data collected from bibliographic sources show MIC values ranging between 2-15ppm.4
Such values have been confirmed
by an in vitro study commissioned by Variati on seven characteristic gram+ bacterial strains, which show a very high activity profile of usnic acid with an average MIC of 10ppm. From different experimental evidence, a
significant decrease of the antibacterial activity in compounds where the hydroxyl groups had been esterified, acetylated or otherwise substituted have been reported,5,6
leading to the conclusion that the maximum activity profile is probably
TABLE 1: CHARACTERISTICS OF THE SODIUM SALT DERIVATIVE Trade name
Application Evosina 100 Sodium Usnate
Antibacterial active ingredient
Evosina GP Green
Propylene Glycol, Sodium Usnate
Antibacterial active ingredient
Specifically suggested for natural deodorant body care, soothing & antidandruff hair care cosmetics, oral care products
Specifically recommended for natural deodorant body care, soothing & antidandruff hair care cosmetics, oral care products
www.personalcaremagazine.com ISO 16128
100% Natural Origin Index
100% Natural Origin Index
Suggested dose
related to maintaining the integrity of usnic acid molecular structure, including its salts. To overcome the poor solubility of usnic acid,
Variati research developed Evosina®, hereafter described as the sodium salt derivative, which shows a better solubility together with an identical strong activity profile. The sodium salt derivative has been obtained salifying usnic acid on the most reactive hydroxyl oxygen (position 15), allowing to save the dibenzofuran-dione structure integrity, therefore maintaining intact all the anti-microbial properties, as evidenced in different in vitro studies.
0.01 - 0.02%
Composition of the sodium salt derivative The sodium salt derivative has been developed in two versions, Evosina 100, in powder form, and Evosina GP Green, which is the liquid version made up using vegetal propylene glycol from rapeseed and sunflower oils. So, both products are 100% plant derived ingredients and certified by green standards (COSMOS).
0.1 - 1%
Efficacy In order to experimentally confirm the bacteriostatic properties, the active ingredient has been firstly in vitro tested on different Gram+ bacteria strains that typically inhabit human skin, such as Staph. aureus and Staph. epidermidis. The average MIC results of about
October 2023 PERSONAL CARE
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