Development trends need the necessity for wider use of the local resources and available natural materials are one of the priorities around the world. Freshwater sapropel is a common material in the water basement of the lakes, but still not sufficiently explored. The main goal of the project to start detailed and systematic research on the medical properties of sapropel to be obtained in Latvia, promote its scientifically based use in balneology, develop new medical procedures and services, and promote development of new exportable products. The results include the survey, sampling depths, and processing, evaluation of external signs, physical, chemical, and biochemical parameters, and evaluation of microbiological indicators. Active components from the sapropel samples extracted using the alkaline method. Sapropel extracts were characterized by organic carbon content, humic and fulvic acid concentrations, total phenolic content, trace metal and pesticide concentrations, total antioxidant status, and microbiological flora. Summarizing the article's main findings it was concluded that Latvian freshwater sapropel can be used as raw material for obtaining sapropel extract and use it in the preparation of pharmaceuticals and promote the development of new exportable products and services.

Sapropel has been used for different purposes - in agriculture as fertilizer, in construction as building material, in cosmetic products, in balneology also in medicine and pharmaceuticals as bioactive component. Previously sapropel has been commonly used in raw form and there is no general accepted method or standard method for obtaining sapropel extract. However, most extraction methods follow the same path. Currently, there are few extraction methods using several extractants for obtaining bioactive components from raw sapropel. The most commonly used extractant is alkaline solution. When sapropel is subjected to alkaline environment, the humic and fulvic acids, together with some lipids, vitamins and sugar, present in the raw sapropel become soluble, however other organic and mineral content present in the sapropel remain solid. Alkaline extraction is followed by filtration and water present in the aqueous mixture is evaporated off. Latvian freshwater sapropel can be used as raw material for obtaining sapropel extract and use it as remedy. But the main question for sapropel usage in medicine, balneology and pharmacy is to develop quality criteria for raw sapropel and its extracts. The quality criteria should include minimum requirements for biologically active substance concentration, pH values, antioxidants as well as physical characteristics. In future studies the differences in extract characteristics of the various deposit sites, as well as the stability of the extracts under different storage conditions should be defined; also, there is need for a common approach to develop method of extraction process for active substances from sapropel and analysis procedures of its extract.

Previously, sapropel has been commonly used in agriculture, cosmetology and medicine in its raw form and there has been no generally accepted method or standard for realizing sapropel extract. However, for sapropel usage in medicine, balneology and pharmacy, it is essential to develop quality criteria for raw sapropel and its extracts. This review aims at discussing and summing up different techniques for extracting bioactive compounds from sapropel as well as the possibilities of creating quality criteria. This paper covers existing analytical techniques and methodologies; currently, there are few extraction methods using several extractants for obtaining bioactive components from raw sapropel. Different freshwater sapropel types have been described and characterized. Bioactive components in sapropel have been identified and explained. Humic acids and fulvic acids have been identified as the main substances and their extraction methods have been listed. Solid-liquid, ultrasound assisted and supercritical fluid extraction methods have been pointed out as the most suitable. Additionally, analysis and storage conditions of the extracts have been discussed. There have been found to be no commonly accepted standard methods for sapropel extraction, or for the analysis and characterization of the sapropel extracts. For pharmacological applications, a common approach for the extraction process of active substances from sapropel and the analysis procedures of the extracts need to be established. This review will help equip other researchers with the latest information on this topic.

Background and Objective: Sapropel, a biologically active sedimentary deposit, is high in organic matter and minerals and has been shown to offer health benefits. Its constituents, humic acid (HA) and fulvic acid (FA), have been found to have some therapeutic applications. The aim of this study was to determine the potential therapeutically significant properties of freshwater sapropel extracts: their polyacid content, antioxidative (AO) status, and biological activity in cell culture. Materials and Methods: Freshwater lakes from the southeast region of Latvia were investigated layer by layer. The total organic carbon (TOC) was determined through combustion using the catalytic oxidation method, HA and FA were measured via acid perspiration, and the total polyphenol content (TPC) and total antioxidant status (TAS) was analysed spectrophotometrically. Sapropel extracts’ regenerative abilities were tested in vitro using a Cell-IQ real-time monitoring system on mouse BALB/c 3T3 fibroblasts and human keratinocyte HaCaT cell lines. Cytotoxicity was measured through neutral red uptake assessment as a concentration-dependent reduction in the uptake of neutral red dye relative to a vehicle control or untreated cells. Results: The highest AO activity was observed in sapropel extracts with elevated concentrations of HA and TPC from Audzelu Lake (1.08 ± 0.03 mmol/L), and the lowest activity was found in extracts from Ivusku Lake (0.31 ± 0.01 mmol/L). Correspondingly, the concentrations of HA in Audzelu and Ivusku Lakes were recorded as 45.2 and 27.4 mg/g, respectively. High concentrations of HA promoted in vitro cell growth upon short-term exposure (up to 6 h). Conclusions: The results show that high TPC correlates with AO status and sapropel extracts with higher concentrations of HA exhibit greater AO activity and promote in vitro cell growth, suggesting a perspective use for short-term topical therapeutic skin applications. However, higher concentrations over longer durations showed cytotoxic effects, indicating the need for further investigation.

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