Water-soluble high molecular weight compounds were isolated in yields of 21-22% from the oleogum of Boswellia serrata and B. carteri. Using anion exchange chromatography and gel permeation chromatography, different proteoglycans were purified and characterized, leading to four principally different groups: (i) Hyp-/Ser-rich extensins with O-glycosidic attached arabinan side chains; (ii) Modified extensins, with arabinogalactosylated side chains containing GlA and 4-O-Me-GlcA; (iii) Glycoproteins with N-glycosidic side chains containing higher amounts of Fuc, Man and GluNH(2,) featuring a 200 kD metalloproteinase that has been de novo sequenced and is described for the first time; (iv) Type II arabinogalactans-proteins. Significant differences between the gums from the two species were observed in the protein content (6% vs 22%), offering the possibility of a quick differentiation of gums from both species for analytical quality control. The data also offer an insight into the plant response towards wound-closing by the formation of extensin and AGP-containing gum.