As early as 1543 BC, the ancient Egyptians isolated salicylic acid from the bark of willow trees and used it as a painkiller. In 1828, Joseph Buchner, a German professor of pharmacy, extracted "salvinoside" from willow bark. In 1829, French chemist Henri Leroux improved the purification method and obtained more salvinoside crystals. In 1838, Italian Lafayette Piria obtained salicylic acid from salvinoside and named it salicylic acid. The discovery of salicylic acid also gave birth to the most successful drug in history-aspirin, whose chemical name is acetylsalicylic acid - a derivative of salicylic acid. After more than a hundred years of research, scientists have discovered that salicylic acid also has anti-inflammatory, acne-removing, keratin-regulating and whitening effects. These discoveries have made salicylic acid a very common skin care and acne-removing ingredient in medical treatment and daily care.
Figure 1. Micrograph showing the morphological characteristics of nanoliposomes analysed. (Oskoueian E, et al.; 2020)
Salicylic acid has a wide range of uses and is inseparable from its many functions. Firstly, salicylic acid is fat soluble and can penetrate into the pores to dissolve lipids, remove accumulated oil and dirt in the pores, loosen acne plugs, while also having anti-inflammatory and anti-bacterial effects. Secondly, salicylic acid has a dual conditioning effect on keratin. It stimulates the production of immature keratin cells and prevents the accumulation of old and dead keratin. It is an ideal ingredient to help regulate the keratin barrier. In addition, topical salicylic acid has varying degrees of anti-inflammatory, astringent and anti-itching effects on seborrhoeic dermatitis, folliculitis, etc. Salicylic acid also has some broad-spectrum bactericidal activity and is effective against many bacteria and fungi. Finally, salicylic acid can dissolve the connections between the skin cuticles, causing the cuticles to fall off, remove excessively thick cuticles, stimulate epidermal metabolism, rejuvenate and lighten the skin, prevent acne spots, and prevent ultraviolet damage and photo-aging. Because of its multi-potency, salicylic acid has been widely used in the skin field. But so far, there are still some challenges in the formulation and application of salicylic acid in skin care, mainly reflected in: 1. The solubility and delivery of salicylic acid; salicylic acid is a fat-soluble compound and is difficult to dissolve in water. After dissolution, salicylic acid crystals may be produced, which irritates the skin. In the early practical formulation applications, salicylic acid is usually dissolved in alcohol. However, alcohol itself is not friendly to the skin, and alcohol is highly volatile and prone to crystallization. Crystallized salicylic acid cannot penetrate into the skin and cannot play a role at all. It is also easy to cause dryness and irritation of the skin. 2. The irritation problem of salicylic acid. For salicylic acid to be effective, its pH value must be lower than 3. This concentration is irritating to the skin. Many people will experience burning, stinging, and itching symptoms after acid brushing, and long-term improper use. 3. The "toxicity" problem of salicylic acid. Experiments have shown that "oral" salicylic acid has similar adverse effects to oral aspirin, which may cause fetal malformations, increase the risk of miscarriage and other pregnancy complications. However, there are currently no experiments to prove the effect of "external salicylic acid" on pregnant women. Although salicylic acid is widely used, many products containing salicylic acid do not achieve the desired effect in actual use due to its various shortcomings.
Researchers have tried a number of ways to solve the solubility and irritation problems with salicylic acid, and liposomal salicylic acid is one of the better ones. Liposomal salicylic acid is a new type of salicylic acid produced by encapsulating salicylic acid in liposomes. As liposomes are tiny spherical vesicles formed by phospholipids as membrane materials, their structure is similar to that of cell membranes, so they have good biocompatibility and transdermal absorption ability. Liposome encapsulation technology can encapsulate lipid-soluble ingredients such as salicylic acid in liposomes to form water-soluble microcapsules, thereby improving their solubility and stability in skin care products and increasing their permeability and absorbability in the skin. These have solved the above-mentioned obstacles in the application of salicylic acid and are a relatively excellent optimisation method.
Alternate Names:
Liposomal salicylic acid
Nanoencapsulated salicylic acid
Salicylic acid liposomes
Liposome-encapsulated salicylic acid
Nanoliposome salicylic acid
References:
1. Oskoueian E, et al.; Nanoliposomes encapsulation of enriched phenolic fraction from pistachio hulls and its antioxidant, anti-inflammatory, and anti-melanogenic activities. J Microencapsul. 2020, 37(1):1-13.
Nanoparticles-Based Delivery Systems for Salicylic Acid as Plant Growth Stimulator and Stress Alleviation
Plants (Basel)
Authors: Polyakov V, Bauer T, Butova V, Minkina T, Rajput VD.
Abstract
The population growth tendency leads to an increase in demand for food products, and in particular, products obtained from the processing of plants. However, there are issues of biotic and abiotic stresses that can significantly reduce crop yields and escalate the food crisis. Therefore, in recent years, the development of new methods of plant protection became an important task. One of the most promising ways to protect plants is to treat them with various phytohormones. Salicylic acid (SA) is one of the regulators of systemic acquired resistance (SAR) signaling pathways. These mechanisms are able to protect plants from biotic and abiotic stresses by increasing the expression of genes that encode antioxidant enzymes. However, salicylic acid in high doses can act as an antagonist and have the negative rebound effect of inhibition of plant growth and development. To maintain optimal SA concentrations in the long term, it is necessary to develop systems for the delivery and slow release of SA in plants. The purpose of this review is to summarize and study methods of delivery and controlled release of SA in a plant. Various carriers-based nanoparticles (NPs) synthesized from both organic and inorganic compounds, their chemical structure, impacts on plants, advantages, and disadvantages are comprehensively discussed. The mechanisms of controlled release of SA and the effects of the use of the considered composites on the growth and development of plants are also described. The present review will be helpful to design or fabricate NPs and NPs-based delivery systems for salicylic acid-controlled release and better understating of the mechanism of SA-NPs interaction to alleviate stress on plants.
Salicylic Acid Co-Precipitation with Alginate via Supercritical Atomization for Cosmetic Applications
Materials (Basel).
Authors: Baldino L, Reverchon E.
Abstract
Alginate-based microparticles were produced via supercritical assisted atomization (SAA) with the aim of obtaining a biocompatible and low-cost carrier for the delivery of active compounds in cosmetic applications. Salicylic acid was selected as an active model compound, and it was co-precipitated with alginate via SAA, operating at 82 bar and 80 °C. In particular, the drug-to-polymer weight ratio was fixed at 1/4, whereas polymer concentration was varied from 5 to 20 mg/mL in the starting aqueous solution. Operating in this way, alginate-salicylic acid microparticles were characterized by a mean diameter of 0.72 ± 0.25 μm, and the active compound became amorphous after processing. A salicylic acid encapsulation efficiency close to 100% was reached, and the drug release time from the biopolymeric microparticles was prolonged up to nine times with respect to untreated salicylic acid powder.
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