Nuclear Magnetic Resonance Characterization of Indonesian Amber

Abstract

Amber from four major Indonesian islands (Sumatra, Sulawesi, Borneo, New Guinea), Malaysian Borneo, and from the Papua New Guinea island of Vanatinai (a total of 19 samples) has been examined by solid state carbon-13 and solution proton nuclear magnetic resonance (NMR) spectroscopy. All samples but one had common NMR fingerprints by all spectral tests, characteristic of NMR Group B ambers. The single exception, called green copal, had NMR fingerprints very similar to a commercial sample of dammar, the name given to many modern exudates from Dipterocarpaceae trees in the region. There was a clear familial resemblance for the dammar and green copal samples with all the spectra from many samples of modern dipterocarp exudates, with the trend of greater spectral complexity in going from amber to copal/dammar and modern exudates. These spectral comparisons provide further evidence that dipterocarp forests provided the resins that matured into copal and eventually amber after the passage of millions of years.