Compounds present in the fruits of Vaccinium species, regarded as one of the richest sources of antioxidant phytonutrients, are reported to play several roles in human health maintenance. Meanwhile, another important group of dietary nutraceutics, i.e. triterpenoids, was not well characterized in these plants. Thus, the purpose of this work was the investigation of triterpenoidal constituents in three wild species bearing edible fruits, i.e. bilberry Vaccinium myrtillus L., cowberry V. vitis-idaea L. and cranberry V. oxycoccus L., naturally occurring and readily harvested in Poland.

Collected berries were used either dried to study the contents of triterpenoids in the entire fruits, or fresh to isolate the constituents of epicuticular wax layer. Dried berries were powdered and extracted in Soxhlet apparatus with diethyl ether. The surface of fresh undamaged berries was gently extracted by chloroform and ethyl ether. Obtained extracts were separated by TLC and isolated triterpene compounds were essayed by GLC.

Two isomeric acids, oleanolic and ursolic, were identified as the main triterpenoid constituents in all berries studied. The total content of both acids were rather similar, amounted to 0.7 % of dried weight in bilberry, 1 % in cowberry and 0.9 % in cranberry. However, the ratio of oleanolic to ursolic acid was different, equaling in bilberry 1:0.58, in cowberry 1:2.8 and in cranberry 1:4.7. Thus, oleanolic acid is almost twice more abundant than ursolic acid in bilberry, whereas in two other berries the amount of ursolic acid is higher, in cowberry more than twice than oleanolic, in cranberry almost five times. In fruit epicuticular wax layers the same acids were detected, with the ratio of oleanolic to ursolic acid respectively 1:0.46, 1:3.8, 1:5.1 in bilberry, cowberry and cranberry. As we discovered previously, the oleanolic acid is more abundant also in other parts (i.e. leaves and rhizomes) of the bilberry plant, whereas ursolic acid is dominant in cowberry and cranberry plants.

The obtained results have shown that in evergreen Vaccinium species, i.e. cowberry and cranberry, the ursolic acid is predominant, whereas in bilberry, shedding leaves for the winter, oleanolic acid is the most abundant. It can indicate the presumable difference in physiological activities of these two isomers, as it is known for other isomeric compounds produced by plants (for example antibacterial (+)-catechin and phytotoxic (-)-catechin). Durability and resistance of cowberry and cranberry fruits are ascribed mainly to their high content of benzoic acid, however, the role of the thickness of epicuticular waxes layer rich in ursolic acid also regarded as the potent preservative, cannot be ruled out.

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