Sapropel is organic sediment that accumulates underwater in shallow to deep marine basins, lagoons and lakes. The sapropel forms by slow decomposition process of phytoplankton, waste material from higher plants and aquatic animals and fine-grained nonorganic particles in the sediment. Sapropel has long been used as a remedy in medicine, having a positive health effect for skin and other organ systems. For some time there has been increasing interest in extracting of active components from the sapropel for use in skin care.
Freshwater sapropel obtained from different Latvia lakes was used in the extraction process of biologically active components. 105 samples from 5 different lakes in eastern Latvia region Latgale were collected during winter time using the frozen surface of the lakes as a platform to support the sapropel extraction device. The samples were used for the research of sapropel and for the extraction of active ingredients.
The raw sapropel samples were tested for the presence of heavy metals and pesticides and used for obtaining sapropel extracts. Sapropel extract was obtained using solid-liquid method with alkaline solution from 56 samples, mixture was stirred for 24 h, then centrifugated and filtrated; filtrate was acidified and centrifuged again. Filtrate was separated from solid particles, and both liquid extract and solid extract were stored at 4°C before use.
Sapropel extracts were characterised by organic carbon content (TOC), humic acid (HA) and Fulvic acid (FA) concentration, pH level, and antioxidant level. Total organic carbon, HA and FA were determined using spectrometric method. To determine antioxidants the following methods were used: DPPH radical method, Folin-Ciocalteu method for determination of the total phenolic content and total antioxidants status were calculated.
The yield in dried extract form was 22 -28 g of humic acids and 5 - 9 g fulvic acids from one-kilogram dried sapropel. Sapropel from different lakes gave different yields, the difference is higher for the fulvic acids where the highest and lowest values differs by more than 80%, while the total organic carbon is more uniform with the difference between lowest and highest values less being less than 30% and HA results showed dispersion within only 20%. Relative antioxidant level variations between the samples from different lakes were considerably stronger with the difference between the highest and the lowest value is almost threefold for the total antioxidant level. The antioxidant level did not correlate with the FA and HA level.
The colour of sapropel extracts is lake and sapropel strata specific ranging from light yellow to almost black due to different humification level of sapropel.
Conclusion: The raw sapropel source site should be selected differently for different active components needed in the extract in order to optimise the extraction yield. Sapropel can be standardised by defining the desired concentration corridor for the chosen parameters and specific raw sapropel location can be defined as part of the characterisation of the extract. The colour of the extract can vary and can be used for organoleptic identification of the extract from specific sapropel site.
This research was supported by „Analysis of characteristics of medical sapropel and its usage for medical purposes and elaboration of industrial extraction methods”, project No. 18.104.22.168/16/A/165.
Audience take away:
• Audience will gain knowledge about extract characterization and will learn about sapropel extract and apply this knowledge in using extracts from natural substances.
• They will gain additional experience about bulk characteristics of sapropel extract and other extracts from natural products with varying properties. Other faculties and labs can use the research results in their research. The results will simplify and make easier to use sapropel extract in drug design.
• Sapropel extract has good commercial potential for its use in cosmetics and pharmaceuticals, but methodological and technological advancements in standardization and characterization are needed for its use in industry.