A team of researchers at the University of Minnesota Twin Cities has pinpointed compounds that help explain Baltic amber’s therapeutic effects and that could lead to new medicines to combat antibiotic-resistant bacteria such as Staphylococcus aureus.
McDermott & Ambrose report in vitro antibacterial activity of compounds present in Baltic amber. Image credit: Edgars Gjacs.
Amber is formed through the fossilization of tree resin from various species of pine and pine-like trees over millions of years.
The largest known deposits of amber, which originate from now extinct conifers of the family Sciadopityaceae, are located in the Baltic Sea region.
Referred to as Baltic amber, this amber has been used medicinally for centuries due to its immune-boosting, wound-healing, analgesic, anti-inflammatory, anti-infective, antifungal, and anticancer properties.
Despite its well established use in folk medicine, a comprehensive study of the bioactive constituents of Baltic amber has yet to be conducted to explain its therapeutic effects.
Furthermore, fossils are an underinvestigated yet promising source of novel drug candidates due to the transformations that occur during the fossilization process and the different metabolic products generated by extinct species.
“We knew from previous research that there were substances in Baltic amber that might lead to new antibiotics, but they had not been systematically explored,” said study lead author Dr. Elizabeth Ambrose, a researcher in the Department of Medicinal Chemistry at the University of Minnesota-Twin Cities.
“We have now extracted and identified several compounds in Baltic amber that show activity against Gram-positive, antibiotic-resistant bacteria.”
Dr. Ambrose and her colleague, University of Minnesota-Twin Cities Ph.D. candidate Connor McDermott, analyzed samples of Baltic amber.
“One major challenge was preparing a homogeneous fine powder from the amber pebbles that could be extracted with solvents,” McDermott explained.
Using gas chromatography-mass spectrometry, the scientists identified dozens of compounds in the amber powder extracts.
The most interesting were abietic acid, dehydroabietic acid and palustric acid — 20-carbon, three-ringed organic compounds with known biological activity.
“The most important finding is that these compounds are active against Gram-positive bacteria, such as certain Staphylococcus aureus strains, but not Gram-negative bacteria,” McDermott said.
“This implies that the composition of the bacterial membrane is important for the activity of the compounds.”
The team also compared the compounds extracted from samples of Baltic amber with those from the Japanese umbrella pine (Sciadopitys verticillata), the closest living relative to the extinct conifers that produced the resin that became Baltic amber.
“We are excited to move forward with these results,” Dr. Ambrose said.
“Abietic acids and their derivatives are potentially an untapped source of new medicines, especially for treating infections caused by Gram-positive bacteria, which are increasingly becoming resistant to known antibiotics.”
The authors presented their results today at the 2021 Spring Meeting of the American Chemical Society (ACS).
Connor McDermott & Elizabeth Ambrose. Paleopharmaceuticals: Prospective drugs from Baltic amber. ACS Spring 2021, abstract # 42581