Chemical composition, antioxidant activity, standardization and kinetics of production of water-propylene glycol extracts of medicinal plants

Abstract

Water-propylene glycol extracts of medicinal plants are widely used as active components in therapeutic and cosmetic products for external use. However, sparse data on the extracting efficiency of water-propylene glycol mixtures and chemical composition of water-propylene glycol extracts of plant raw materials are available in the scientific literature. Usually the manufacturer documentation also provides information about characteristics of the products that are not related to their biological activity. The results of HPLC/MS/MS study of Matricaria chamomilla L. flowers have shown that water-propylene glycol and water-ethanol extracts are similar in the composition of phenolic compounds: the dominant compounds of water-propylene glycol extract of Matricaria chamomilla L. flowers are apigenin and its glycosides (apigenin-7-glucoside, apigenin-7-O-6-O-malonyl-D-glycoside, apigenin-7-acetylglycoside, acetyl-malonyl-apigenin-7-O-glycoside), as well as 5,4’-dioxy-3,6,7,3’-tetramethoxyflavone, cis- and trans-forms of 2-O-glucopyranoside 2-hydroxy-4-methoxycoric acid, 7-methoxycumarin. Spectral and analytical characteristics in the UV-visible range of the spectra of water-propylene glycol extracts of a number of medicinal plants most often used in the cosmetic industry were studied to reveal extracts with the highest protective properties against UV radiation in A and B areas (extracts of Salvia officinalis L. leaves, Matricaria chamomilla L. flowers, Achillea millefolium L. grass), free radicals (extracts of Camellia sinensis L. leaves, Hypericum perforatum L. herb), and the highest content of flavonoids (extracts of Hypericum perforatum L. herb, leaves of Salvia officinalis L.) were revealed. When extracting raw materials from the same batch, the optical density at a wavelength of 270 nm is associated with the content of flavonoids, antioxidants and dry matter by a functional relationship, which is very convenient for rapid control of extraction processes in order to obtain a product with reproducible characteristics. Formulas for calculating the content of antioxidants in extracts using the DPPH method in comparison with standard samples of rutin and gallic acid are derived. Interpretation of data on the antioxidant content in different extracts in comparison with other analytical parameters are also presented. Demonstrated high repeatability of the shape of the spectral curves of Matricaria chamomilla L. flowers extract, observed regardless of the source of raw materials can be used in combination with the individuality of the curve shape of the extracts of raw materials of different types as one of the authenticity criteria. The proposed UV-spectrometric method was used to study the dynamics of Matricaria chamomilla L. flower extraction under different process parameters (temperature, propylene glycol/water ratio in the extractant). It is shown that extraction of raw materials with 50% water-propylene glycol for 4 h at a temperature of 50°C is optimal.