Byline: Uwe. Wollina
In recent years the interest for natural substances in dermatotherapy and cosmetics has increased. Peat is a complex natural source of humic substances that are of potential interest in both dermatology and cosmetology. Humic substances in peat have been partially characterized and pharmacologic and biologic activities have been documented. Possible clinical applications are outlined.
Natural substances have historically been a rich source of lead molecules in drug development. Recently, effective high-impact technologies have become available to screen natural products.[sup]  There is a growing serious interest in characterization of natural substances in medicine, in particular dermatology, and dermocosmetics.[sup] ,
Peat, a source of natural substances, has long been used in physiotherapy, rheumatology and sports medicine. Peat is a rich natural source of humic substances that are of potential interest in dermatology and cosmetology.
Humic substances are natural products that develop during decomposition of organic matter in humus. Humic substances are the most stable fraction of organic substances in soils. The dark color comes from quinine structures [Figure 1]. A substantial part of humic acids is in carboxylic acid functional groups that bind multivalent positively charged ions.[sup]  Although the composition of peat is very complex and not completely understood[sup] , the principal substances may be divided into the following categories:[sup] 
*humic acids *humin *fulvic acids
Other major components include pectins, cellulose and lignins, wax, resins and inorganic material. Dark peat contains about 10 times more humic substances than the white garden peat. The composition and the amount of the particular ingredients may vary with the geographical area, where peat was harvested. Drying peat can cause a breakdown in the natural cellular structure that negatively interferes with its water solubility.
Humic substances are highly chemically active yet recalcitrant with respect to biodegradation. They have several biologic activities such as antibacterial, antifungal, immunomodulatory and photoprotective actions that are of potential interest in dermatology and cosmetology.
Studies on the Pharmacologic and Biologic Activity of Peat
In the past, crude extracts from peat of various sources have been screened for antibacterial activity.[sup]  Humic acid and fulvic acid exert antimicrobial activities in vitro .[sup]  Antibacterial activity has been shown against a variety of pathologic germs including Staphylococcus aureus , Escherichia coli , Pseudomonas aeruginosa , Klebsiella pneumoniae and against yeasts like Candida albicans .[sup] , Humic acids and poly(OH)carboxylates are selective inhibitors of Herpes simplex virus and Cytomegalovirus replication.[sup] , Oxihumate - a water-soluble compound of peat - inhibited HIV-1 infection of MT-2 cells with an IC(50) of 12.5 [micro]g/ml. Treatment of free and cell-attached HIV with oxihumate irreversibly reduced infectivity, while the susceptibility of target cells to the virus was not impaired by treatment prior to infection. The infectivity of the HIV particles was inhibited by interference with CD4 binding and the V3 loop-mediated step of virus entry. No viral resistance to oxihumate developed over a 12-week period in vitro .[sup]  Furthermore, it was shown in vivo that oral administration of humus extract in freshwater fish...