Twelve compounds including secologanin, loganin, the aglycon of loganin, and a new iridoid called glucologanin were isolated from fruit of common snowberry Symphoricarpos albus (L.) Blake. The structure of glucologanin was confirmed using PMR and mass spectroscopy and chemical transformations. 2′,3′,4′,6′,3′,4′, Common snowberry Symphoricarpos L. (Caprifoliaceae, honeysuckle) is a bush up to 1.5 m in height and is widely used as a decorative plant. In nature it is found mainly in North America and in the northern strip of European Russia. In Ukraine, white common snowberry Syphoricarpos albus (L.) Blake is most common.The phytochemistry of common snowberry is insufficiently studied. The contents in fruit of S. albus of phenolic acids [1], carbohydrates [2], and iridoids [3, 4] have been reported.We studied fruit of white common snowberry (S. albus) collected in October-November 2005 in the Botanical Garden of Karazin Kharkov National University (Ukraine). Fruit contains a large amount (85-87%) of water, which we took into account during its processing.Freshly collected berries were ground and extracted with n-butanol. The extract was divided into three fractions by polarity and chromatographed over columns using mixtures of CHCl 3 and CH 3 OH of increasing polarity for elution (see Experimental).A total of 12 pure compounds was isolated. Three of the isolated compounds were iridoids and were identified as secologanin (1), loganin (2), and loganigenin (3) [3, 5, 6]. A fourth glycoside (4) was new. The structures of 1, 2, and 3 were confirmed by PMR and mass spectrometry.Compound 1 was found to be highly unstable during its isolation. The compound was quickly oxidized in solutions by oxygen in air. The product of auto-oxidation was presumably cyclized to form lactone 8. The carboxyl and vinyl (ethylene) groups were involved in the cyclization. The product of auto-oxidation 8 was isolated during additional purification of 1 by column chromatography. Compound 8 contained two C=O groups according to IR spectra, one of which was an ester conjugated to a C=C bond (absorption band at 1696 cm −1 ); the second, a carbonyl of a seven-membered lactone ring (absorption band at 1655 cm −1 ).The PMR spectrum of 8 exhibited a characteristic resonance for the C-3 proton at 7.3 ppm, for the anomeric C-1′ proton at 4.5 ppm; a characteristic multiplet for the ester OCH 3 group at 3.7 ppm; and for protons H-5 and H-11 at 2.7 ppm. There was no resonance for an aldehyde.The mass spectrum of the lactone was consistent with the proposed structure of 8 (see Experimental). Compound 2 can exist as cyclic dimer 5. The C-7 OH group and ester carbonyl form two intermolecular H-bonds. The mass spectrum of the loganin dimer was consistent with the proposed structure of 5.